fair.c 265.9 KB
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// SPDX-License-Identifier: GPL-2.0
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */
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#include "sched.h"
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#include <trace/events/sched.h>

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/*
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 * Targeted preemption latency for CPU-bound tasks:
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 *
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 * NOTE: this latency value is not the same as the concept of
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 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
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 *
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 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
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 *
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_latency			= 6000000ULL;
unsigned int normalized_sysctl_sched_latency		= 6000000ULL;
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/*
 * The initial- and re-scaling of tunables is configurable
 *
 * Options are:
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 *
 *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
 *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 *
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
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 */
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enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
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/*
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 * Minimal preemption granularity for CPU-bound tasks:
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 *
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 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_min_granularity		= 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
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/*
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 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
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 */
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static unsigned int sched_nr_latency = 8;
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/*
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 * After fork, child runs first. If set to 0 (default) then
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 * parent will (try to) run first.
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 */
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
 * SCHED_OTHER wake-up granularity.
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
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 *
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_wakeup_granularity		= 1000000UL;
unsigned int normalized_sysctl_sched_wakeup_granularity	= 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
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#ifdef CONFIG_SMP
/*
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 * For asym packing, by default the lower numbered CPU has higher priority.
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 */
int __weak arch_asym_cpu_priority(int cpu)
{
	return -cpu;
}
#endif

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#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
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 * (default: 5 msec, units: microseconds)
 */
unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
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#endif

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/*
 * The margin used when comparing utilization with CPU capacity:
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 * util * margin < capacity * 1024
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 *
 * (default: ~20%)
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 */
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unsigned int capacity_margin				= 1280;
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static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
	lw->weight += inc;
	lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
	lw->weight -= dec;
	lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
	lw->weight = w;
	lw->inv_weight = 0;
}

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/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
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static unsigned int get_update_sysctl_factor(void)
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{
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	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
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	unsigned int factor;

	switch (sysctl_sched_tunable_scaling) {
	case SCHED_TUNABLESCALING_NONE:
		factor = 1;
		break;
	case SCHED_TUNABLESCALING_LINEAR:
		factor = cpus;
		break;
	case SCHED_TUNABLESCALING_LOG:
	default:
		factor = 1 + ilog2(cpus);
		break;
	}

	return factor;
}

static void update_sysctl(void)
{
	unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
	(sysctl_##name = (factor) * normalized_sysctl_##name)
	SET_SYSCTL(sched_min_granularity);
	SET_SYSCTL(sched_latency);
	SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void sched_init_granularity(void)
{
	update_sysctl();
}

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#define WMULT_CONST	(~0U)
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#define WMULT_SHIFT	32

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static void __update_inv_weight(struct load_weight *lw)
{
	unsigned long w;

	if (likely(lw->inv_weight))
		return;

	w = scale_load_down(lw->weight);

	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
		lw->inv_weight = 1;
	else if (unlikely(!w))
		lw->inv_weight = WMULT_CONST;
	else
		lw->inv_weight = WMULT_CONST / w;
}
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/*
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 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
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 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
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 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
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 */
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
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	__update_inv_weight(lw);
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	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
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	}

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	/* hint to use a 32x32->64 mul */
	fact = (u64)(u32)fact * lw->inv_weight;
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	while (fact >> 32) {
		fact >>= 1;
		shift--;
	}
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	return mul_u64_u32_shr(delta_exec, fact, shift);
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}


const struct sched_class fair_sched_class;
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/**************************************************************
 * CFS operations on generic schedulable entities:
 */

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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
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	return cfs_rq->rq;
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}

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static inline struct task_struct *task_of(struct sched_entity *se)
{
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	SCHED_WARN_ON(!entity_is_task(se));
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	return container_of(se, struct task_struct, se);
}

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/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
		for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return grp->my_q;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		struct rq *rq = rq_of(cfs_rq);
		int cpu = cpu_of(rq);
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
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		 * enqueued. The fact that we always enqueue bottom-up
		 * reduces this to two cases and a special case for the root
		 * cfs_rq. Furthermore, it also means that we will always reset
		 * tmp_alone_branch either when the branch is connected
		 * to a tree or when we reach the beg of the tree
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		 */
		if (cfs_rq->tg->parent &&
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		    cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
			/*
			 * If parent is already on the list, we add the child
			 * just before. Thanks to circular linked property of
			 * the list, this means to put the child at the tail
			 * of the list that starts by parent.
			 */
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
				&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
			/*
			 * The branch is now connected to its tree so we can
			 * reset tmp_alone_branch to the beginning of the
			 * list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else if (!cfs_rq->tg->parent) {
			/*
			 * cfs rq without parent should be put
			 * at the tail of the list.
			 */
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			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq->leaf_cfs_rq_list);
			/*
			 * We have reach the beg of a tree so we can reset
			 * tmp_alone_branch to the beginning of the list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else {
			/*
			 * The parent has not already been added so we want to
			 * make sure that it will be put after us.
			 * tmp_alone_branch points to the beg of the branch
			 * where we will add parent.
			 */
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				rq->tmp_alone_branch);
			/*
			 * update tmp_alone_branch to points to the new beg
			 * of the branch
			 */
			rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
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		}
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		cfs_rq->on_list = 1;
	}
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->on_list) {
		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
		cfs_rq->on_list = 0;
	}
}

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/* Iterate thr' all leaf cfs_rq's on a runqueue */
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#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)			\
	list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list,	\
				 leaf_cfs_rq_list)
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/* Do the two (enqueued) entities belong to the same group ? */
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static inline struct cfs_rq *
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
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		return se->cfs_rq;
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	return NULL;
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}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return se->parent;
}

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static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
	int se_depth, pse_depth;

	/*
	 * preemption test can be made between sibling entities who are in the
	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
	 * both tasks until we find their ancestors who are siblings of common
	 * parent.
	 */

	/* First walk up until both entities are at same depth */
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	se_depth = (*se)->depth;
	pse_depth = (*pse)->depth;
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	while (se_depth > pse_depth) {
		se_depth--;
		*se = parent_entity(*se);
	}

	while (pse_depth > se_depth) {
		pse_depth--;
		*pse = parent_entity(*pse);
	}

	while (!is_same_group(*se, *pse)) {
		*se = parent_entity(*se);
		*pse = parent_entity(*pse);
	}
}

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
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}


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#define for_each_sched_entity(se) \
		for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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	return &task_rq(p)->cfs;
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}

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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	struct task_struct *p = task_of(se);
	struct rq *rq = task_rq(p);

	return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return NULL;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

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#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)	\
		for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return NULL;
}

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static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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static __always_inline
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void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
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/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

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static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
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{
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	s64 delta = (s64)(vruntime - max_vruntime);
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	if (delta > 0)
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		max_vruntime = vruntime;
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	return max_vruntime;
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}

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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

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static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

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static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
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	struct sched_entity *curr = cfs_rq->curr;
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	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
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	u64 vruntime = cfs_rq->min_vruntime;

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	if (curr) {
		if (curr->on_rq)
			vruntime = curr->vruntime;
		else
			curr = NULL;
	}
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	if (leftmost) { /* non-empty tree */
		struct sched_entity *se;
		se = rb_entry(leftmost, struct sched_entity, run_node);
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		if (!curr)
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			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

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	/* ensure we never gain time by being placed backwards. */
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	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
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#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
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}

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
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	struct rb_node *parent = NULL;
	struct sched_entity *entry;
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	bool leftmost = true;
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	/*
	 * Find the right place in the rbtree:
	 */
	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_entity, run_node);
		/*
		 * We dont care about collisions. Nodes with
		 * the same key stay together.
		 */
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		if (entity_before(se, entry)) {
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			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
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			leftmost = false;
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		}
	}

	rb_link_node(&se->run_node, parent, link);
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	rb_insert_color_cached(&se->run_node,
			       &cfs_rq->tasks_timeline, leftmost);
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}

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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
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}

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struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
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	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
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}

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static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
	struct rb_node *next = rb_next(&se->run_node);

	if (!next)
		return NULL;

	return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
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struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
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	if (!last)
		return NULL;
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	return rb_entry(last, struct sched_entity, run_node);
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}

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/**************************************************************
 * Scheduling class statistics methods:
 */

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int sched_proc_update_handler(struct ctl_table *table, int write,
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		void __user *buffer, size_t *lenp,
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		loff_t *ppos)
{
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	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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	unsigned int factor = get_update_sysctl_factor();
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	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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#define WRT_SYSCTL(name) \
	(normalized_sysctl_##name = sysctl_##name / (factor))
	WRT_SYSCTL(sched_min_granularity);
	WRT_SYSCTL(sched_latency);
	WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL

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	return 0;
}
#endif
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/*
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 * delta /= w
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 */
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static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
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{
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	if (unlikely(se->load.weight != NICE_0_LOAD))
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		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
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	return delta;
}

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/*
 * The idea is to set a period in which each task runs once.
 *
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 * When there are too many tasks (sched_nr_latency) we have to stretch
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 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
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static u64 __sched_period(unsigned long nr_running)
{
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	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
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}

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/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
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 * s = p*P[w/rw]
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 */
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static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
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	for_each_sched_entity(se) {
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		struct load_weight *load;
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		struct load_weight lw;
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		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
668

M
Mike Galbraith 已提交
669
		if (unlikely(!se->on_rq)) {
670
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
671 672 673 674

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
675
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
676 677
	}
	return slice;
678 679
}

680
/*
A
Andrei Epure 已提交
681
 * We calculate the vruntime slice of a to-be-inserted task.
682
 *
683
 * vs = s/w
684
 */
685
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
686
{
687
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
688 689
}

690
#ifdef CONFIG_SMP
691
#include "pelt.h"
692 693
#include "sched-pelt.h"

694
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
695 696
static unsigned long task_h_load(struct task_struct *p);

697 698
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
699
{
700
	struct sched_avg *sa = &se->avg;
701

702 703
	memset(sa, 0, sizeof(*sa));

704 705 706 707 708 709 710
	/*
	 * Tasks are intialized with full load to be seen as heavy tasks until
	 * they get a chance to stabilize to their real load level.
	 * Group entities are intialized with zero load to reflect the fact that
	 * nothing has been attached to the task group yet.
	 */
	if (entity_is_task(se))
711 712
		sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);

713 714
	se->runnable_weight = se->load.weight;

715
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
716
}
717

718
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
719
static void attach_entity_cfs_rq(struct sched_entity *se);
720

721 722 723 724 725 726 727 728 729 730 731 732 733
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
734
 *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
735
 *
736
 * where n denotes the nth task and cpu_scale the CPU capacity.
737
 *
738 739
 * For example, for a CPU with 1024 of capacity, a simplest series from
 * the beginning would be like:
740 741 742 743 744 745 746 747 748 749 750
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
751 752
	long cpu_scale = arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
753 754 755 756 757 758 759 760 761 762 763 764

	if (cap > 0) {
		if (cfs_rq->avg.util_avg != 0) {
			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
			sa->util_avg /= (cfs_rq->avg.load_avg + 1);

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
	}
765 766 767 768 769 770 771

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
772
			update_cfs_rq_load_avg(now, cfs_rq);
773
			attach_entity_load_avg(cfs_rq, se, 0);
774 775 776 777 778
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
779
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
780 781 782 783
			return;
		}
	}

784
	attach_entity_cfs_rq(se);
785 786
}

787
#else /* !CONFIG_SMP */
788
void init_entity_runnable_average(struct sched_entity *se)
789 790
{
}
791 792 793
void post_init_entity_util_avg(struct sched_entity *se)
{
}
794 795 796
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
797
#endif /* CONFIG_SMP */
798

799
/*
800
 * Update the current task's runtime statistics.
801
 */
802
static void update_curr(struct cfs_rq *cfs_rq)
803
{
804
	struct sched_entity *curr = cfs_rq->curr;
805
	u64 now = rq_clock_task(rq_of(cfs_rq));
806
	u64 delta_exec;
807 808 809 810

	if (unlikely(!curr))
		return;

811 812
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
813
		return;
814

I
Ingo Molnar 已提交
815
	curr->exec_start = now;
816

817 818 819 820
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
821
	schedstat_add(cfs_rq->exec_clock, delta_exec);
822 823 824 825

	curr->vruntime += calc_delta_fair(delta_exec, curr);
	update_min_vruntime(cfs_rq);

826 827 828
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

829
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
830
		cgroup_account_cputime(curtask, delta_exec);
831
		account_group_exec_runtime(curtask, delta_exec);
832
	}
833 834

	account_cfs_rq_runtime(cfs_rq, delta_exec);
835 836
}

837 838 839 840 841
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

842
static inline void
843
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
844
{
845 846 847 848 849 850 851
	u64 wait_start, prev_wait_start;

	if (!schedstat_enabled())
		return;

	wait_start = rq_clock(rq_of(cfs_rq));
	prev_wait_start = schedstat_val(se->statistics.wait_start);
852 853

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
854 855
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
856

857
	__schedstat_set(se->statistics.wait_start, wait_start);
858 859
}

860
static inline void
861 862 863
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
864 865
	u64 delta;

866 867 868 869
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
870 871 872 873 874 875 876 877 878

	if (entity_is_task(se)) {
		p = task_of(se);
		if (task_on_rq_migrating(p)) {
			/*
			 * Preserve migrating task's wait time so wait_start
			 * time stamp can be adjusted to accumulate wait time
			 * prior to migration.
			 */
879
			__schedstat_set(se->statistics.wait_start, delta);
880 881 882 883 884
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

885
	__schedstat_set(se->statistics.wait_max,
886
		      max(schedstat_val(se->statistics.wait_max), delta));
887 888 889
	__schedstat_inc(se->statistics.wait_count);
	__schedstat_add(se->statistics.wait_sum, delta);
	__schedstat_set(se->statistics.wait_start, 0);
890 891
}

892
static inline void
893 894 895
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
896 897 898 899 900 901 902
	u64 sleep_start, block_start;

	if (!schedstat_enabled())
		return;

	sleep_start = schedstat_val(se->statistics.sleep_start);
	block_start = schedstat_val(se->statistics.block_start);
903 904 905 906

	if (entity_is_task(se))
		tsk = task_of(se);

907 908
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
909 910 911 912

		if ((s64)delta < 0)
			delta = 0;

913
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
914
			__schedstat_set(se->statistics.sleep_max, delta);
915

916 917
		__schedstat_set(se->statistics.sleep_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
918 919 920 921 922 923

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
924 925
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
926 927 928 929

		if ((s64)delta < 0)
			delta = 0;

930
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
931
			__schedstat_set(se->statistics.block_max, delta);
932

933 934
		__schedstat_set(se->statistics.block_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
935 936 937

		if (tsk) {
			if (tsk->in_iowait) {
938 939
				__schedstat_add(se->statistics.iowait_sum, delta);
				__schedstat_inc(se->statistics.iowait_count);
940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957
				trace_sched_stat_iowait(tsk, delta);
			}

			trace_sched_stat_blocked(tsk, delta);

			/*
			 * Blocking time is in units of nanosecs, so shift by
			 * 20 to get a milliseconds-range estimation of the
			 * amount of time that the task spent sleeping:
			 */
			if (unlikely(prof_on == SLEEP_PROFILING)) {
				profile_hits(SLEEP_PROFILING,
						(void *)get_wchan(tsk),
						delta >> 20);
			}
			account_scheduler_latency(tsk, delta >> 10, 0);
		}
	}
958 959
}

960 961 962
/*
 * Task is being enqueued - update stats:
 */
963
static inline void
964
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
965
{
966 967 968
	if (!schedstat_enabled())
		return;

969 970 971 972
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
973
	if (se != cfs_rq->curr)
974
		update_stats_wait_start(cfs_rq, se);
975 976 977

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
978 979 980
}

static inline void
981
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
982
{
983 984 985 986

	if (!schedstat_enabled())
		return;

987 988 989 990
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
991
	if (se != cfs_rq->curr)
992
		update_stats_wait_end(cfs_rq, se);
993

994 995
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
996

997
		if (tsk->state & TASK_INTERRUPTIBLE)
998
			__schedstat_set(se->statistics.sleep_start,
999 1000
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
1001
			__schedstat_set(se->statistics.block_start,
1002
				      rq_clock(rq_of(cfs_rq)));
1003 1004 1005
	}
}

1006 1007 1008 1009
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1010
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1011 1012 1013 1014
{
	/*
	 * We are starting a new run period:
	 */
1015
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1016 1017 1018 1019 1020 1021
}

/**************************************************
 * Scheduling class queueing methods:
 */

1022 1023
#ifdef CONFIG_NUMA_BALANCING
/*
1024 1025 1026
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
1027
 */
1028 1029
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1030 1031 1032

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1033

1034 1035 1036
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
	pid_t gid;
	int active_nodes;

	struct rcu_head rcu;
	unsigned long total_faults;
	unsigned long max_faults_cpu;
	/*
	 * Faults_cpu is used to decide whether memory should move
	 * towards the CPU. As a consequence, these stats are weighted
	 * more by CPU use than by memory faults.
	 */
	unsigned long *faults_cpu;
	unsigned long faults[0];
};

static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);

1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

	/*
	 * Calculations based on RSS as non-present and empty pages are skipped
	 * by the PTE scanner and NUMA hinting faults should be trapped based
	 * on resident pages
	 */
	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
	rss = get_mm_rss(p->mm);
	if (!rss)
		rss = nr_scan_pages;

	rss = round_up(rss, nr_scan_pages);
	return rss / nr_scan_pages;
}

/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560

static unsigned int task_scan_min(struct task_struct *p)
{
1084
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1085 1086 1087
	unsigned int scan, floor;
	unsigned int windows = 1;

1088 1089
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1090 1091 1092 1093 1094 1095
	floor = 1000 / windows;

	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
	return max_t(unsigned int, floor, scan);
}

1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;
	}

	return max(smin, period);
}

1115 1116
static unsigned int task_scan_max(struct task_struct *p)
{
1117 1118
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1119 1120 1121

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);
		unsigned long period = smax;

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;

		smax = max(smax, period);
	}

1137 1138 1139
	return max(smin, smax);
}

1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180
void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
	int mm_users = 0;
	struct mm_struct *mm = p->mm;

	if (mm) {
		mm_users = atomic_read(&mm->mm_users);
		if (mm_users == 1) {
			mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
			mm->numa_scan_seq = 0;
		}
	}
	p->node_stamp			= 0;
	p->numa_scan_seq		= mm ? mm->numa_scan_seq : 0;
	p->numa_scan_period		= sysctl_numa_balancing_scan_delay;
	p->numa_work.next		= &p->numa_work;
	p->numa_faults			= NULL;
	p->numa_group			= NULL;
	p->last_task_numa_placement	= 0;
	p->last_sum_exec_runtime	= 0;

	/* New address space, reset the preferred nid */
	if (!(clone_flags & CLONE_VM)) {
		p->numa_preferred_nid = -1;
		return;
	}

	/*
	 * New thread, keep existing numa_preferred_nid which should be copied
	 * already by arch_dup_task_struct but stagger when scans start.
	 */
	if (mm) {
		unsigned int delay;

		delay = min_t(unsigned int, task_scan_max(current),
			current->numa_scan_period * mm_users * NSEC_PER_MSEC);
		delay += 2 * TICK_NSEC;
		p->node_stamp = delay;
	}
}

1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running += (p->numa_preferred_nid != -1);
	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}

1193 1194 1195 1196 1197 1198 1199 1200 1201
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)

/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)

1202 1203 1204 1205 1206
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1207
/*
1208
 * The averaged statistics, shared & private, memory & CPU,
1209 1210 1211 1212 1213
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1214
{
1215
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1216 1217 1218 1219
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1220
	if (!p->numa_faults)
1221 1222
		return 0;

1223 1224
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1225 1226
}

1227 1228 1229 1230 1231
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1232 1233
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1234 1235
}

1236 1237
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1238 1239
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1240 1241
}

1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265
static inline unsigned long group_faults_priv(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
	}

	return faults;
}

static inline unsigned long group_faults_shared(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
	}

	return faults;
}

1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

static bool numa_is_active_node(int nid, struct numa_group *ng)
{
	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}

1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

	/*
	 * All nodes are directly connected, and the same distance
	 * from each other. No need for fancy placement algorithms.
	 */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return 0;

	/*
	 * This code is called for each node, introducing N^2 complexity,
	 * which should be ok given the number of nodes rarely exceeds 8.
	 */
	for_each_online_node(node) {
		unsigned long faults;
		int dist = node_distance(nid, node);

		/*
		 * The furthest away nodes in the system are not interesting
		 * for placement; nid was already counted.
		 */
		if (dist == sched_max_numa_distance || node == nid)
			continue;

		/*
		 * On systems with a backplane NUMA topology, compare groups
		 * of nodes, and move tasks towards the group with the most
		 * memory accesses. When comparing two nodes at distance
		 * "hoplimit", only nodes closer by than "hoplimit" are part
		 * of each group. Skip other nodes.
		 */
		if (sched_numa_topology_type == NUMA_BACKPLANE &&
					dist > maxdist)
			continue;

		/* Add up the faults from nearby nodes. */
		if (task)
			faults = task_faults(p, node);
		else
			faults = group_faults(p, node);

		/*
		 * On systems with a glueless mesh NUMA topology, there are
		 * no fixed "groups of nodes". Instead, nodes that are not
		 * directly connected bounce traffic through intermediate
		 * nodes; a numa_group can occupy any set of nodes.
		 * The further away a node is, the less the faults count.
		 * This seems to result in good task placement.
		 */
		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
			faults *= (sched_max_numa_distance - dist);
			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
		}

		score += faults;
	}

	return score;
}

1343 1344 1345 1346 1347 1348
/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
1349 1350
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1351
{
1352
	unsigned long faults, total_faults;
1353

1354
	if (!p->numa_faults)
1355 1356 1357 1358 1359 1360 1361
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1362
	faults = task_faults(p, nid);
1363 1364
	faults += score_nearby_nodes(p, nid, dist, true);

1365
	return 1000 * faults / total_faults;
1366 1367
}

1368 1369
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1370
{
1371 1372 1373 1374 1375 1376 1377 1378
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1379 1380
		return 0;

1381
	faults = group_faults(p, nid);
1382 1383
	faults += score_nearby_nodes(p, nid, dist, false);

1384
	return 1000 * faults / total_faults;
1385 1386
}

1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);

	/*
	 * Multi-stage node selection is used in conjunction with a periodic
	 * migration fault to build a temporal task<->page relation. By using
	 * a two-stage filter we remove short/unlikely relations.
	 *
	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
	 * a task's usage of a particular page (n_p) per total usage of this
	 * page (n_t) (in a given time-span) to a probability.
	 *
	 * Our periodic faults will sample this probability and getting the
	 * same result twice in a row, given these samples are fully
	 * independent, is then given by P(n)^2, provided our sample period
	 * is sufficiently short compared to the usage pattern.
	 *
	 * This quadric squishes small probabilities, making it less likely we
	 * act on an unlikely task<->page relation.
	 */
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
	if (!cpupid_pid_unset(last_cpupid) &&
				cpupid_to_nid(last_cpupid) != dst_nid)
		return false;

	/* Always allow migrate on private faults */
	if (cpupid_match_pid(p, last_cpupid))
		return true;

	/* A shared fault, but p->numa_group has not been set up yet. */
	if (!ng)
		return true;

	/*
1427 1428
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1429
	 */
1430 1431
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1432 1433 1434
		return true;

	/*
1435 1436 1437 1438 1439 1440
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1441
	 */
1442 1443
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1444 1445
}

1446
static unsigned long weighted_cpuload(struct rq *rq);
1447 1448
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1449
static unsigned long capacity_of(int cpu);
1450

1451
/* Cached statistics for all CPUs within a node */
1452
struct numa_stats {
1453
	unsigned long nr_running;
1454
	unsigned long load;
1455 1456

	/* Total compute capacity of CPUs on a node */
1457
	unsigned long compute_capacity;
1458 1459

	/* Approximate capacity in terms of runnable tasks on a node */
1460
	unsigned long task_capacity;
1461
	int has_free_capacity;
1462
};
1463

1464 1465 1466 1467 1468
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1469 1470
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1471 1472 1473 1474 1475 1476

	memset(ns, 0, sizeof(*ns));
	for_each_cpu(cpu, cpumask_of_node(nid)) {
		struct rq *rq = cpu_rq(cpu);

		ns->nr_running += rq->nr_running;
1477
		ns->load += weighted_cpuload(rq);
1478
		ns->compute_capacity += capacity_of(cpu);
1479 1480

		cpus++;
1481 1482
	}

1483 1484 1485 1486 1487
	/*
	 * If we raced with hotplug and there are no CPUs left in our mask
	 * the @ns structure is NULL'ed and task_numa_compare() will
	 * not find this node attractive.
	 *
1488 1489
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1490 1491 1492 1493
	 */
	if (!cpus)
		return;

1494 1495 1496 1497 1498 1499
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

	ns->task_capacity = min_t(unsigned, capacity,
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1500
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1501 1502
}

1503 1504
struct task_numa_env {
	struct task_struct *p;
1505

1506 1507
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1508

1509
	struct numa_stats src_stats, dst_stats;
1510

1511
	int imbalance_pct;
1512
	int dist;
1513 1514 1515

	struct task_struct *best_task;
	long best_imp;
1516 1517 1518
	int best_cpu;
};

1519 1520 1521 1522 1523
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
	if (env->best_task)
		put_task_struct(env->best_task);
1524 1525
	if (p)
		get_task_struct(p);
1526 1527 1528 1529 1530 1531

	env->best_task = p;
	env->best_imp = imp;
	env->best_cpu = env->dst_cpu;
}

1532
static bool load_too_imbalanced(long src_load, long dst_load,
1533 1534
				struct task_numa_env *env)
{
1535 1536
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547
	long src_capacity, dst_capacity;

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1548

1549
	imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1550

1551
	orig_src_load = env->src_stats.load;
1552
	orig_dst_load = env->dst_stats.load;
1553

1554
	old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1555 1556 1557

	/* Would this change make things worse? */
	return (imb > old_imb);
1558 1559
}

1560 1561 1562 1563 1564 1565
/*
 * This checks if the overall compute and NUMA accesses of the system would
 * be improved if the source tasks was migrated to the target dst_cpu taking
 * into account that it might be best if task running on the dst_cpu should
 * be exchanged with the source task
 */
1566
static void task_numa_compare(struct task_numa_env *env,
1567
			      long taskimp, long groupimp, bool maymove)
1568 1569 1570
{
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1571
	long src_load, dst_load;
1572
	long load;
1573
	long imp = env->p->numa_group ? groupimp : taskimp;
1574
	long moveimp = imp;
1575
	int dist = env->dist;
1576 1577

	rcu_read_lock();
1578 1579
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1580 1581
		cur = NULL;

1582 1583 1584 1585 1586 1587 1588
	/*
	 * Because we have preemption enabled we can get migrated around and
	 * end try selecting ourselves (current == env->p) as a swap candidate.
	 */
	if (cur == env->p)
		goto unlock;

1589 1590 1591 1592 1593 1594 1595
	if (!cur) {
		if (maymove || imp > env->best_imp)
			goto assign;
		else
			goto unlock;
	}

1596 1597 1598 1599
	/*
	 * "imp" is the fault differential for the source task between the
	 * source and destination node. Calculate the total differential for
	 * the source task and potential destination task. The more negative
1600
	 * the value is, the more remote accesses that would be expected to
1601 1602
	 * be incurred if the tasks were swapped.
	 */
1603 1604 1605
	/* Skip this swap candidate if cannot move to the source cpu */
	if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
		goto unlock;
1606

1607 1608 1609 1610 1611 1612 1613
	/*
	 * If dst and source tasks are in the same NUMA group, or not
	 * in any group then look only at task weights.
	 */
	if (cur->numa_group == env->p->numa_group) {
		imp = taskimp + task_weight(cur, env->src_nid, dist) -
		      task_weight(cur, env->dst_nid, dist);
1614
		/*
1615 1616
		 * Add some hysteresis to prevent swapping the
		 * tasks within a group over tiny differences.
1617
		 */
1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630
		if (cur->numa_group)
			imp -= imp / 16;
	} else {
		/*
		 * Compare the group weights. If a task is all by itself
		 * (not part of a group), use the task weight instead.
		 */
		if (cur->numa_group && env->p->numa_group)
			imp += group_weight(cur, env->src_nid, dist) -
			       group_weight(cur, env->dst_nid, dist);
		else
			imp += task_weight(cur, env->src_nid, dist) -
			       task_weight(cur, env->dst_nid, dist);
1631 1632
	}

1633
	if (imp <= env->best_imp)
1634 1635
		goto unlock;

1636 1637 1638
	if (maymove && moveimp > imp && moveimp > env->best_imp) {
		imp = moveimp - 1;
		cur = NULL;
1639
		goto assign;
1640
	}
1641 1642 1643 1644

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
1645 1646 1647 1648
	load = task_h_load(env->p) - task_h_load(cur);
	if (!load)
		goto assign;

1649 1650
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1651

1652
	if (load_too_imbalanced(src_load, dst_load, env))
1653 1654
		goto unlock;

1655
assign:
1656 1657 1658 1659
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1660 1661
	if (!cur) {
		/*
1662
		 * select_idle_siblings() uses an per-CPU cpumask that
1663 1664 1665
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1666 1667
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1668 1669
		local_irq_enable();
	}
1670

1671 1672 1673 1674 1675
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1676 1677
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1678
{
1679 1680
	long src_load, dst_load, load;
	bool maymove = false;
1681 1682
	int cpu;

1683 1684 1685 1686 1687 1688 1689 1690 1691 1692
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;

	/*
	 * If the improvement from just moving env->p direction is better
	 * than swapping tasks around, check if a move is possible.
	 */
	maymove = !load_too_imbalanced(src_load, dst_load, env);

1693 1694
	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1695
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1696 1697 1698
			continue;

		env->dst_cpu = cpu;
1699
		task_numa_compare(env, taskimp, groupimp, maymove);
1700 1701 1702
	}
}

1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

	if (src->has_free_capacity && !dst->has_free_capacity)
		return false;

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1720 1721 1722
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1723 1724 1725 1726 1727
		return true;

	return false;
}

1728 1729 1730 1731
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1732

1733
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1734
		.src_nid = task_node(p),
1735 1736 1737 1738 1739

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1740
		.best_cpu = -1,
1741 1742
	};
	struct sched_domain *sd;
1743
	unsigned long taskweight, groupweight;
1744
	int nid, ret, dist;
1745
	long taskimp, groupimp;
1746

1747
	/*
1748 1749 1750 1751 1752 1753
	 * Pick the lowest SD_NUMA domain, as that would have the smallest
	 * imbalance and would be the first to start moving tasks about.
	 *
	 * And we want to avoid any moving of tasks about, as that would create
	 * random movement of tasks -- counter the numa conditions we're trying
	 * to satisfy here.
1754 1755
	 */
	rcu_read_lock();
1756
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1757 1758
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1759 1760
	rcu_read_unlock();

1761 1762 1763 1764 1765 1766 1767
	/*
	 * Cpusets can break the scheduler domain tree into smaller
	 * balance domains, some of which do not cross NUMA boundaries.
	 * Tasks that are "trapped" in such domains cannot be migrated
	 * elsewhere, so there is no point in (re)trying.
	 */
	if (unlikely(!sd)) {
1768
		sched_setnuma(p, task_node(p));
1769 1770 1771
		return -EINVAL;
	}

1772
	env.dst_nid = p->numa_preferred_nid;
1773 1774 1775 1776 1777 1778
	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
	taskweight = task_weight(p, env.src_nid, dist);
	groupweight = group_weight(p, env.src_nid, dist);
	update_numa_stats(&env.src_stats, env.src_nid);
	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1779
	update_numa_stats(&env.dst_stats, env.dst_nid);
1780

1781
	/* Try to find a spot on the preferred nid. */
1782 1783
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1784

1785 1786 1787 1788 1789 1790 1791
	/*
	 * Look at other nodes in these cases:
	 * - there is no space available on the preferred_nid
	 * - the task is part of a numa_group that is interleaved across
	 *   multiple NUMA nodes; in order to better consolidate the group,
	 *   we need to check other locations.
	 */
1792
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1793 1794 1795
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1796

1797
			dist = node_distance(env.src_nid, env.dst_nid);
1798 1799 1800 1801 1802
			if (sched_numa_topology_type == NUMA_BACKPLANE &&
						dist != env.dist) {
				taskweight = task_weight(p, env.src_nid, dist);
				groupweight = group_weight(p, env.src_nid, dist);
			}
1803

1804
			/* Only consider nodes where both task and groups benefit */
1805 1806
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1807
			if (taskimp < 0 && groupimp < 0)
1808 1809
				continue;

1810
			env.dist = dist;
1811 1812
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1813 1814
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1815 1816 1817
		}
	}

1818 1819 1820 1821 1822 1823 1824 1825
	/*
	 * If the task is part of a workload that spans multiple NUMA nodes,
	 * and is migrating into one of the workload's active nodes, remember
	 * this node as the task's preferred numa node, so the workload can
	 * settle down.
	 * A task that migrated to a second choice node will be better off
	 * trying for a better one later. Do not set the preferred node here.
	 */
1826 1827 1828 1829
	if (p->numa_group) {
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
1830
			nid = cpu_to_node(env.best_cpu);
1831

1832 1833
		if (nid != p->numa_preferred_nid)
			sched_setnuma(p, nid);
1834 1835 1836 1837 1838
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1839

1840 1841 1842 1843
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
1844
	p->numa_scan_period = task_scan_start(p);
1845

1846
	if (env.best_task == NULL) {
1847 1848 1849
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1850 1851 1852 1853
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1854 1855
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1856 1857
	put_task_struct(env.best_task);
	return ret;
1858 1859
}

1860 1861 1862
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1863 1864
	unsigned long interval = HZ;

1865
	/* This task has no NUMA fault statistics yet */
1866
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1867 1868
		return;

1869
	/* Periodically retry migrating the task to the preferred node */
1870
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1871
	p->numa_migrate_retry = jiffies + interval;
1872 1873

	/* Success if task is already running on preferred CPU */
1874
	if (task_node(p) == p->numa_preferred_nid)
1875 1876 1877
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1878
	task_numa_migrate(p);
1879 1880
}

1881
/*
1882
 * Find out how many nodes on the workload is actively running on. Do this by
1883 1884 1885 1886
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 */
1887
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1888 1889
{
	unsigned long faults, max_faults = 0;
1890
	int nid, active_nodes = 0;
1891 1892 1893 1894 1895 1896 1897 1898 1899

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
		if (faults > max_faults)
			max_faults = faults;
	}

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
1900 1901
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1902
	}
1903 1904 1905

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1906 1907
}

1908 1909 1910
/*
 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
 * increments. The more local the fault statistics are, the higher the scan
1911 1912 1913
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
1914 1915
 */
#define NUMA_PERIOD_SLOTS 10
1916
#define NUMA_PERIOD_THRESHOLD 7
1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927

/*
 * Increase the scan period (slow down scanning) if the majority of
 * our memory is already on our local node, or if the majority of
 * the page accesses are shared with other processes.
 * Otherwise, decrease the scan period.
 */
static void update_task_scan_period(struct task_struct *p,
			unsigned long shared, unsigned long private)
{
	unsigned int period_slot;
1928
	int lr_ratio, ps_ratio;
1929 1930 1931 1932 1933 1934 1935 1936
	int diff;

	unsigned long remote = p->numa_faults_locality[0];
	unsigned long local = p->numa_faults_locality[1];

	/*
	 * If there were no record hinting faults then either the task is
	 * completely idle or all activity is areas that are not of interest
1937 1938 1939
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1940
	 */
1941
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		p->mm->numa_next_scan = jiffies +
			msecs_to_jiffies(p->numa_scan_period);

		return;
	}

	/*
	 * Prepare to scale scan period relative to the current period.
	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
	 */
	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976
	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);

	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are local. There is no need to
		 * do fast NUMA scanning, since memory is already local.
		 */
		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are shared with other tasks.
		 * There is no point in continuing fast NUMA scanning,
		 * since other tasks may just move the memory elsewhere.
		 */
		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
1977 1978 1979 1980 1981
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1982 1983 1984
		 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
		 * yet they are not on the local NUMA node. Speed up
		 * NUMA scanning to get the memory moved over.
1985
		 */
1986 1987
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1988 1989 1990 1991 1992 1993 1994
	}

	p->numa_scan_period = clamp(p->numa_scan_period + diff,
			task_scan_min(p), task_scan_max(p));
	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
	u64 runtime, delta, now;
	/* Use the start of this time slice to avoid calculations. */
	now = p->se.exec_start;
	runtime = p->se.sum_exec_runtime;

	if (p->last_task_numa_placement) {
		delta = runtime - p->last_sum_exec_runtime;
		*period = now - p->last_task_numa_placement;
	} else {
2013
		delta = p->se.avg.load_sum;
2014
		*period = LOAD_AVG_MAX;
2015 2016 2017 2018 2019 2020 2021 2022
	}

	p->last_sum_exec_runtime = runtime;
	p->last_task_numa_placement = now;

	return delta;
}

2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069
/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
	nodemask_t nodes;
	int dist;

	/* Direct connections between all NUMA nodes. */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return nid;

	/*
	 * On a system with glueless mesh NUMA topology, group_weight
	 * scores nodes according to the number of NUMA hinting faults on
	 * both the node itself, and on nearby nodes.
	 */
	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
		unsigned long score, max_score = 0;
		int node, max_node = nid;

		dist = sched_max_numa_distance;

		for_each_online_node(node) {
			score = group_weight(p, node, dist);
			if (score > max_score) {
				max_score = score;
				max_node = node;
			}
		}
		return max_node;
	}

	/*
	 * Finding the preferred nid in a system with NUMA backplane
	 * interconnect topology is more involved. The goal is to locate
	 * tasks from numa_groups near each other in the system, and
	 * untangle workloads from different sides of the system. This requires
	 * searching down the hierarchy of node groups, recursively searching
	 * inside the highest scoring group of nodes. The nodemask tricks
	 * keep the complexity of the search down.
	 */
	nodes = node_online_map;
	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
		unsigned long max_faults = 0;
2070
		nodemask_t max_group = NODE_MASK_NONE;
2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103
		int a, b;

		/* Are there nodes at this distance from each other? */
		if (!find_numa_distance(dist))
			continue;

		for_each_node_mask(a, nodes) {
			unsigned long faults = 0;
			nodemask_t this_group;
			nodes_clear(this_group);

			/* Sum group's NUMA faults; includes a==b case. */
			for_each_node_mask(b, nodes) {
				if (node_distance(a, b) < dist) {
					faults += group_faults(p, b);
					node_set(b, this_group);
					node_clear(b, nodes);
				}
			}

			/* Remember the top group. */
			if (faults > max_faults) {
				max_faults = faults;
				max_group = this_group;
				/*
				 * subtle: at the smallest distance there is
				 * just one node left in each "group", the
				 * winner is the preferred nid.
				 */
				nid = a;
			}
		}
		/* Next round, evaluate the nodes within max_group. */
2104 2105
		if (!max_faults)
			break;
2106 2107 2108 2109 2110
		nodes = max_group;
	}
	return nid;
}

2111 2112
static void task_numa_placement(struct task_struct *p)
{
2113 2114
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2115
	unsigned long fault_types[2] = { 0, 0 };
2116 2117
	unsigned long total_faults;
	u64 runtime, period;
2118
	spinlock_t *group_lock = NULL;
2119

2120 2121 2122 2123 2124
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
2125
	seq = READ_ONCE(p->mm->numa_scan_seq);
2126 2127 2128
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2129
	p->numa_scan_period_max = task_scan_max(p);
2130

2131 2132 2133 2134
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2135 2136 2137
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2138
		spin_lock_irq(group_lock);
2139 2140
	}

2141 2142
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2143 2144
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2145
		unsigned long faults = 0, group_faults = 0;
2146
		int priv;
2147

2148
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2149
			long diff, f_diff, f_weight;
2150

2151 2152 2153 2154
			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2155

2156
			/* Decay existing window, copy faults since last scan */
2157 2158 2159
			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
			fault_types[priv] += p->numa_faults[membuf_idx];
			p->numa_faults[membuf_idx] = 0;
2160

2161 2162 2163 2164 2165 2166 2167 2168
			/*
			 * Normalize the faults_from, so all tasks in a group
			 * count according to CPU use, instead of by the raw
			 * number of faults. Tasks with little runtime have
			 * little over-all impact on throughput, and thus their
			 * faults are less important.
			 */
			f_weight = div64_u64(runtime << 16, period + 1);
2169
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2170
				   (total_faults + 1);
2171 2172
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2173

2174 2175 2176
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2177
			p->total_numa_faults += diff;
2178
			if (p->numa_group) {
2179 2180 2181 2182 2183 2184 2185 2186 2187
				/*
				 * safe because we can only change our own group
				 *
				 * mem_idx represents the offset for a given
				 * nid and priv in a specific region because it
				 * is at the beginning of the numa_faults array.
				 */
				p->numa_group->faults[mem_idx] += diff;
				p->numa_group->faults_cpu[mem_idx] += f_diff;
2188
				p->numa_group->total_faults += diff;
2189
				group_faults += p->numa_group->faults[mem_idx];
2190
			}
2191 2192
		}

2193 2194 2195 2196
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2197 2198 2199 2200 2201 2202 2203

		if (group_faults > max_group_faults) {
			max_group_faults = group_faults;
			max_group_nid = nid;
		}
	}

2204 2205
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2206
	if (p->numa_group) {
2207
		numa_group_count_active_nodes(p->numa_group);
2208
		spin_unlock_irq(group_lock);
2209
		max_nid = preferred_group_nid(p, max_group_nid);
2210 2211
	}

2212 2213 2214 2215 2216 2217 2218
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);

		if (task_node(p) != p->numa_preferred_nid)
			numa_migrate_preferred(p);
2219
	}
2220 2221
}

2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232
static inline int get_numa_group(struct numa_group *grp)
{
	return atomic_inc_not_zero(&grp->refcount);
}

static inline void put_numa_group(struct numa_group *grp)
{
	if (atomic_dec_and_test(&grp->refcount))
		kfree_rcu(grp, rcu);
}

2233 2234
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2235 2236 2237 2238 2239 2240 2241 2242 2243
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

	if (unlikely(!p->numa_group)) {
		unsigned int size = sizeof(struct numa_group) +
2244
				    4*nr_node_ids*sizeof(unsigned long);
2245 2246 2247 2248 2249 2250

		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
		if (!grp)
			return;

		atomic_set(&grp->refcount, 1);
2251 2252
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2253
		spin_lock_init(&grp->lock);
2254
		grp->gid = p->pid;
2255
		/* Second half of the array tracks nids where faults happen */
2256 2257
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2258

2259
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2260
			grp->faults[i] = p->numa_faults[i];
2261

2262
		grp->total_faults = p->total_numa_faults;
2263

2264 2265 2266 2267 2268
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2269
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2270 2271

	if (!cpupid_match_pid(tsk, cpupid))
2272
		goto no_join;
2273 2274 2275

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2276
		goto no_join;
2277 2278 2279

	my_grp = p->numa_group;
	if (grp == my_grp)
2280
		goto no_join;
2281 2282 2283 2284 2285 2286

	/*
	 * Only join the other group if its bigger; if we're the bigger group,
	 * the other task will join us.
	 */
	if (my_grp->nr_tasks > grp->nr_tasks)
2287
		goto no_join;
2288 2289 2290 2291 2292

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2293
		goto no_join;
2294

2295 2296 2297 2298 2299 2300 2301
	/* Always join threads in the same process. */
	if (tsk->mm == current->mm)
		join = true;

	/* Simple filter to avoid false positives due to PID collisions */
	if (flags & TNF_SHARED)
		join = true;
2302

2303 2304 2305
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2306
	if (join && !get_numa_group(grp))
2307
		goto no_join;
2308 2309 2310 2311 2312 2313

	rcu_read_unlock();

	if (!join)
		return;

2314 2315
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2316

2317
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2318 2319
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2320
	}
2321 2322
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2323 2324 2325 2326 2327

	my_grp->nr_tasks--;
	grp->nr_tasks++;

	spin_unlock(&my_grp->lock);
2328
	spin_unlock_irq(&grp->lock);
2329 2330 2331 2332

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2333 2334 2335 2336 2337
	return;

no_join:
	rcu_read_unlock();
	return;
2338 2339 2340 2341 2342
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2343
	void *numa_faults = p->numa_faults;
2344 2345
	unsigned long flags;
	int i;
2346 2347

	if (grp) {
2348
		spin_lock_irqsave(&grp->lock, flags);
2349
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2350
			grp->faults[i] -= p->numa_faults[i];
2351
		grp->total_faults -= p->total_numa_faults;
2352

2353
		grp->nr_tasks--;
2354
		spin_unlock_irqrestore(&grp->lock, flags);
2355
		RCU_INIT_POINTER(p->numa_group, NULL);
2356 2357 2358
		put_numa_group(grp);
	}

2359
	p->numa_faults = NULL;
2360
	kfree(numa_faults);
2361 2362
}

2363 2364 2365
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2366
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2367 2368
{
	struct task_struct *p = current;
2369
	bool migrated = flags & TNF_MIGRATED;
2370
	int cpu_node = task_node(current);
2371
	int local = !!(flags & TNF_FAULT_LOCAL);
2372
	struct numa_group *ng;
2373
	int priv;
2374

2375
	if (!static_branch_likely(&sched_numa_balancing))
2376 2377
		return;

2378 2379 2380 2381
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2382
	/* Allocate buffer to track faults on a per-node basis */
2383 2384
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2385
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2386

2387 2388
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2389
			return;
2390

2391
		p->total_numa_faults = 0;
2392
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2393
	}
2394

2395 2396 2397 2398 2399 2400 2401 2402
	/*
	 * First accesses are treated as private, otherwise consider accesses
	 * to be private if the accessing pid has not changed
	 */
	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
		priv = 1;
	} else {
		priv = cpupid_match_pid(p, last_cpupid);
2403
		if (!priv && !(flags & TNF_NO_GROUP))
2404
			task_numa_group(p, last_cpupid, flags, &priv);
2405 2406
	}

2407 2408 2409 2410 2411 2412
	/*
	 * If a workload spans multiple NUMA nodes, a shared fault that
	 * occurs wholly within the set of nodes that the workload is
	 * actively using should be counted as local. This allows the
	 * scan rate to slow down when a workload has settled down.
	 */
2413 2414 2415 2416
	ng = p->numa_group;
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2417 2418
		local = 1;

2419
	task_numa_placement(p);
2420

2421 2422 2423 2424 2425
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
	if (time_after(jiffies, p->numa_migrate_retry))
2426 2427
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2428 2429
	if (migrated)
		p->numa_pages_migrated += pages;
2430 2431
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2432

2433 2434
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2435
	p->numa_faults_locality[local] += pages;
2436 2437
}

2438 2439
static void reset_ptenuma_scan(struct task_struct *p)
{
2440 2441 2442 2443 2444 2445 2446 2447
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2448
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2449 2450 2451
	p->mm->numa_scan_offset = 0;
}

2452 2453 2454 2455 2456 2457 2458 2459 2460
/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
void task_numa_work(struct callback_head *work)
{
	unsigned long migrate, next_scan, now = jiffies;
	struct task_struct *p = current;
	struct mm_struct *mm = p->mm;
2461
	u64 runtime = p->se.sum_exec_runtime;
2462
	struct vm_area_struct *vma;
2463
	unsigned long start, end;
2464
	unsigned long nr_pte_updates = 0;
2465
	long pages, virtpages;
2466

2467
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480

	work->next = work; /* protect against double add */
	/*
	 * Who cares about NUMA placement when they're dying.
	 *
	 * NOTE: make sure not to dereference p->mm before this check,
	 * exit_task_work() happens _after_ exit_mm() so we could be called
	 * without p->mm even though we still had it when we enqueued this
	 * work.
	 */
	if (p->flags & PF_EXITING)
		return;

2481
	if (!mm->numa_next_scan) {
2482 2483
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2484 2485
	}

2486 2487 2488 2489 2490 2491 2492
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2493 2494
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2495
		p->numa_scan_period = task_scan_start(p);
2496
	}
2497

2498
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2499 2500 2501
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2502 2503 2504 2505 2506 2507
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2508 2509 2510
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2511
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2512 2513
	if (!pages)
		return;
2514

2515

2516 2517
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2518
	vma = find_vma(mm, start);
2519 2520
	if (!vma) {
		reset_ptenuma_scan(p);
2521
		start = 0;
2522 2523
		vma = mm->mmap;
	}
2524
	for (; vma; vma = vma->vm_next) {
2525
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2526
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2527
			continue;
2528
		}
2529

2530 2531 2532 2533 2534 2535 2536 2537 2538 2539
		/*
		 * Shared library pages mapped by multiple processes are not
		 * migrated as it is expected they are cache replicated. Avoid
		 * hinting faults in read-only file-backed mappings or the vdso
		 * as migrating the pages will be of marginal benefit.
		 */
		if (!vma->vm_mm ||
		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
			continue;

M
Mel Gorman 已提交
2540 2541 2542 2543 2544 2545
		/*
		 * Skip inaccessible VMAs to avoid any confusion between
		 * PROT_NONE and NUMA hinting ptes
		 */
		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
			continue;
2546

2547 2548 2549 2550
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2551
			nr_pte_updates = change_prot_numa(vma, start, end);
2552 2553

			/*
2554 2555 2556 2557 2558 2559
			 * Try to scan sysctl_numa_balancing_size worth of
			 * hpages that have at least one present PTE that
			 * is not already pte-numa. If the VMA contains
			 * areas that are unused or already full of prot_numa
			 * PTEs, scan up to virtpages, to skip through those
			 * areas faster.
2560 2561 2562
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2563
			virtpages -= (end - start) >> PAGE_SHIFT;
2564

2565
			start = end;
2566
			if (pages <= 0 || virtpages <= 0)
2567
				goto out;
2568 2569

			cond_resched();
2570
		} while (end != vma->vm_end);
2571
	}
2572

2573
out:
2574
	/*
P
Peter Zijlstra 已提交
2575 2576 2577 2578
	 * It is possible to reach the end of the VMA list but the last few
	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
	 * would find the !migratable VMA on the next scan but not reset the
	 * scanner to the start so check it now.
2579 2580
	 */
	if (vma)
2581
		mm->numa_scan_offset = start;
2582 2583 2584
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595

	/*
	 * Make sure tasks use at least 32x as much time to run other code
	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
	 * Usually update_task_scan_period slows down scanning enough; on an
	 * overloaded system we need to limit overhead on a per task basis.
	 */
	if (unlikely(p->se.sum_exec_runtime != runtime)) {
		u64 diff = p->se.sum_exec_runtime - runtime;
		p->node_stamp += 32 * diff;
	}
2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620
}

/*
 * Drive the periodic memory faults..
 */
void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
	struct callback_head *work = &curr->numa_work;
	u64 period, now;

	/*
	 * We don't care about NUMA placement if we don't have memory.
	 */
	if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
		return;

	/*
	 * Using runtime rather than walltime has the dual advantage that
	 * we (mostly) drive the selection from busy threads and that the
	 * task needs to have done some actual work before we bother with
	 * NUMA placement.
	 */
	now = curr->se.sum_exec_runtime;
	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;

2621
	if (now > curr->node_stamp + period) {
2622
		if (!curr->node_stamp)
2623
			curr->numa_scan_period = task_scan_start(curr);
2624
		curr->node_stamp += period;
2625 2626 2627 2628 2629 2630 2631

		if (!time_before(jiffies, curr->mm->numa_next_scan)) {
			init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
			task_work_add(curr, work, true);
		}
	}
}
2632

2633 2634 2635 2636
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2637 2638 2639 2640 2641 2642 2643 2644

static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
}

static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}
2645

2646 2647
#endif /* CONFIG_NUMA_BALANCING */

2648 2649 2650 2651
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2652
	if (!parent_entity(se))
2653
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2654
#ifdef CONFIG_SMP
2655 2656 2657 2658 2659 2660
	if (entity_is_task(se)) {
		struct rq *rq = rq_of(cfs_rq);

		account_numa_enqueue(rq, task_of(se));
		list_add(&se->group_node, &rq->cfs_tasks);
	}
2661
#endif
2662 2663 2664 2665 2666 2667 2668
	cfs_rq->nr_running++;
}

static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_sub(&cfs_rq->load, se->load.weight);
2669
	if (!parent_entity(se))
2670
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2671
#ifdef CONFIG_SMP
2672 2673
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2674
		list_del_init(&se->group_node);
2675
	}
2676
#endif
2677 2678 2679
	cfs_rq->nr_running--;
}

2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720
/*
 * Signed add and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define add_positive(_ptr, _val) do {                           \
	typeof(_ptr) ptr = (_ptr);                              \
	typeof(_val) val = (_val);                              \
	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
								\
	res = var + val;                                        \
								\
	if (val < 0 && res > var)                               \
		res = 0;                                        \
								\
	WRITE_ONCE(*ptr, res);                                  \
} while (0)

/*
 * Unsigned subtract and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define sub_positive(_ptr, _val) do {				\
	typeof(_ptr) ptr = (_ptr);				\
	typeof(*ptr) val = (_val);				\
	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
	res = var - val;					\
	if (res > var)						\
		res = 0;					\
	WRITE_ONCE(*ptr, res);					\
} while (0)

#ifdef CONFIG_SMP
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2721 2722 2723 2724
	cfs_rq->runnable_weight += se->runnable_weight;

	cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
	cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
2725 2726 2727 2728 2729
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2730 2731 2732 2733 2734
	cfs_rq->runnable_weight -= se->runnable_weight;

	sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
	sub_positive(&cfs_rq->avg.runnable_load_sum,
		     se_runnable(se) * se->avg.runnable_load_sum);
2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760
}

static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
}

static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
}
#else
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif

2761
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2762
			    unsigned long weight, unsigned long runnable)
2763 2764 2765 2766 2767 2768 2769 2770 2771 2772
{
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
		account_entity_dequeue(cfs_rq, se);
		dequeue_runnable_load_avg(cfs_rq, se);
	}
	dequeue_load_avg(cfs_rq, se);

2773
	se->runnable_weight = runnable;
2774 2775 2776
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2777 2778 2779 2780 2781 2782 2783
	do {
		u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;

		se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
		se->avg.runnable_load_avg =
			div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
	} while (0);
2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799
#endif

	enqueue_load_avg(cfs_rq, se);
	if (se->on_rq) {
		account_entity_enqueue(cfs_rq, se);
		enqueue_runnable_load_avg(cfs_rq, se);
	}
}

void reweight_task(struct task_struct *p, int prio)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct load_weight *load = &se->load;
	unsigned long weight = scale_load(sched_prio_to_weight[prio]);

2800
	reweight_entity(cfs_rq, se, weight, weight);
2801 2802 2803
	load->inv_weight = sched_prio_to_wmult[prio];
}

2804
#ifdef CONFIG_FAIR_GROUP_SCHED
2805
#ifdef CONFIG_SMP
2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843
/*
 * All this does is approximate the hierarchical proportion which includes that
 * global sum we all love to hate.
 *
 * That is, the weight of a group entity, is the proportional share of the
 * group weight based on the group runqueue weights. That is:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------               (1)
 *			  \Sum grq->load.weight
 *
 * Now, because computing that sum is prohibitively expensive to compute (been
 * there, done that) we approximate it with this average stuff. The average
 * moves slower and therefore the approximation is cheaper and more stable.
 *
 * So instead of the above, we substitute:
 *
 *   grq->load.weight -> grq->avg.load_avg                         (2)
 *
 * which yields the following:
 *
 *                     tg->weight * grq->avg.load_avg
 *   ge->load.weight = ------------------------------              (3)
 *				tg->load_avg
 *
 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
 *
 * That is shares_avg, and it is right (given the approximation (2)).
 *
 * The problem with it is that because the average is slow -- it was designed
 * to be exactly that of course -- this leads to transients in boundary
 * conditions. In specific, the case where the group was idle and we start the
 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
 * yielding bad latency etc..
 *
 * Now, in that special case (1) reduces to:
 *
 *                     tg->weight * grq->load.weight
2844
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857
 *			    grp->load.weight
 *
 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
 *
 * So what we do is modify our approximation (3) to approach (4) in the (near)
 * UP case, like:
 *
 *   ge->load.weight =
 *
 *              tg->weight * grq->load.weight
 *     ---------------------------------------------------         (5)
 *     tg->load_avg - grq->avg.load_avg + grq->load.weight
 *
2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869
 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
 * we need to use grq->avg.load_avg as its lower bound, which then gives:
 *
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------		   (6)
 *				tg_load_avg'
 *
 * Where:
 *
 *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
 *                  max(grq->load.weight, grq->avg.load_avg)
2870 2871 2872 2873 2874 2875 2876 2877 2878
 *
 * And that is shares_weight and is icky. In the (near) UP case it approaches
 * (4) while in the normal case it approaches (3). It consistently
 * overestimates the ge->load.weight and therefore:
 *
 *   \Sum ge->load.weight >= tg->weight
 *
 * hence icky!
 */
2879
static long calc_group_shares(struct cfs_rq *cfs_rq)
2880
{
2881 2882 2883 2884
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2885

2886
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2887

2888
	tg_weight = atomic_long_read(&tg->load_avg);
2889

2890 2891 2892
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2893

2894
	shares = (tg_shares * load);
2895 2896
	if (tg_weight)
		shares /= tg_weight;
2897

2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909
	/*
	 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
	 * of a group with small tg->shares value. It is a floor value which is
	 * assigned as a minimum load.weight to the sched_entity representing
	 * the group on a CPU.
	 *
	 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
	 * on an 8-core system with 8 tasks each runnable on one CPU shares has
	 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
	 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
	 * instead of 0.
	 */
2910
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
2911
}
2912 2913

/*
2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938
 * This calculates the effective runnable weight for a group entity based on
 * the group entity weight calculated above.
 *
 * Because of the above approximation (2), our group entity weight is
 * an load_avg based ratio (3). This means that it includes blocked load and
 * does not represent the runnable weight.
 *
 * Approximate the group entity's runnable weight per ratio from the group
 * runqueue:
 *
 *					     grq->avg.runnable_load_avg
 *   ge->runnable_weight = ge->load.weight * -------------------------- (7)
 *						 grq->avg.load_avg
 *
 * However, analogous to above, since the avg numbers are slow, this leads to
 * transients in the from-idle case. Instead we use:
 *
 *   ge->runnable_weight = ge->load.weight *
 *
 *		max(grq->avg.runnable_load_avg, grq->runnable_weight)
 *		-----------------------------------------------------	(8)
 *		      max(grq->avg.load_avg, grq->load.weight)
 *
 * Where these max() serve both to use the 'instant' values to fix the slow
 * from-idle and avoid the /0 on to-idle, similar to (6).
2939 2940 2941
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
2942 2943 2944 2945 2946 2947 2948
	long runnable, load_avg;

	load_avg = max(cfs_rq->avg.load_avg,
		       scale_load_down(cfs_rq->load.weight));

	runnable = max(cfs_rq->avg.runnable_load_avg,
		       scale_load_down(cfs_rq->runnable_weight));
2949 2950 2951 2952

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
2953

2954 2955
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
2956
#endif /* CONFIG_SMP */
2957

2958 2959
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2960 2961 2962 2963 2964
/*
 * Recomputes the group entity based on the current state of its group
 * runqueue.
 */
static void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
2965
{
2966 2967
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
2968

2969
	if (!gcfs_rq)
2970 2971
		return;

2972
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
2973
		return;
2974

2975
#ifndef CONFIG_SMP
2976
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
2977 2978

	if (likely(se->load.weight == shares))
2979
		return;
2980
#else
2981 2982
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
2983
#endif
P
Peter Zijlstra 已提交
2984

2985
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
2986
}
2987

P
Peter Zijlstra 已提交
2988
#else /* CONFIG_FAIR_GROUP_SCHED */
2989
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
2990 2991 2992 2993
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2994
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
2995
{
2996 2997
	struct rq *rq = rq_of(cfs_rq);

2998
	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
2999 3000 3001
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
3002
		 * a real problem.
3003 3004 3005 3006 3007 3008 3009 3010 3011 3012
		 *
		 * It will not get called when we go idle, because the idle
		 * thread is a different class (!fair), nor will the utilization
		 * number include things like RT tasks.
		 *
		 * As is, the util number is not freq-invariant (we'd have to
		 * implement arch_scale_freq_capacity() for that).
		 *
		 * See cpu_util().
		 */
3013
		cpufreq_update_util(rq, flags);
3014 3015 3016
	}
}

3017
#ifdef CONFIG_SMP
3018
#ifdef CONFIG_FAIR_GROUP_SCHED
3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031
/**
 * update_tg_load_avg - update the tg's load avg
 * @cfs_rq: the cfs_rq whose avg changed
 * @force: update regardless of how small the difference
 *
 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
 * However, because tg->load_avg is a global value there are performance
 * considerations.
 *
 * In order to avoid having to look at the other cfs_rq's, we use a
 * differential update where we store the last value we propagated. This in
 * turn allows skipping updates if the differential is 'small'.
 *
3032
 * Updating tg's load_avg is necessary before update_cfs_share().
3033
 */
3034
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3035
{
3036
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3037

3038 3039 3040 3041 3042 3043
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3044 3045 3046
	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
		atomic_long_add(delta, &cfs_rq->tg->load_avg);
		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3047
	}
3048
}
3049

3050
/*
3051
 * Called within set_task_rq() right before setting a task's CPU. The
3052 3053 3054 3055 3056 3057
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
3058 3059 3060
	u64 p_last_update_time;
	u64 n_last_update_time;

3061 3062 3063 3064 3065 3066 3067 3068 3069 3070
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

	/*
	 * We are supposed to update the task to "current" time, then its up to
	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
	 * getting what current time is, so simply throw away the out-of-date
	 * time. This will result in the wakee task is less decayed, but giving
	 * the wakee more load sounds not bad.
	 */
3071 3072
	if (!(se->avg.last_update_time && prev))
		return;
3073 3074

#ifndef CONFIG_64BIT
3075
	{
3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

		do {
			p_last_update_time_copy = prev->load_last_update_time_copy;
			n_last_update_time_copy = next->load_last_update_time_copy;

			smp_rmb();

			p_last_update_time = prev->avg.last_update_time;
			n_last_update_time = next->avg.last_update_time;

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
3090
	}
3091
#else
3092 3093
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3094
#endif
3095 3096
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3097
}
3098

3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109

/*
 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
 * propagate its contribution. The key to this propagation is the invariant
 * that for each group:
 *
 *   ge->avg == grq->avg						(1)
 *
 * _IFF_ we look at the pure running and runnable sums. Because they
 * represent the very same entity, just at different points in the hierarchy.
 *
3110 3111 3112
 * Per the above update_tg_cfs_util() is trivial and simply copies the running
 * sum over (but still wrong, because the group entity and group rq do not have
 * their PELT windows aligned).
3113 3114 3115 3116 3117 3118 3119 3120
 *
 * However, update_tg_cfs_runnable() is more complex. So we have:
 *
 *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg		(2)
 *
 * And since, like util, the runnable part should be directly transferable,
 * the following would _appear_ to be the straight forward approach:
 *
3121
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3122 3123 3124
 *
 * And per (1) we have:
 *
3125
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143
 *
 * Which gives:
 *
 *                      ge->load.weight * grq->avg.load_avg
 *   ge->avg.load_avg = -----------------------------------		(4)
 *                               grq->load.weight
 *
 * Except that is wrong!
 *
 * Because while for entities historical weight is not important and we
 * really only care about our future and therefore can consider a pure
 * runnable sum, runqueues can NOT do this.
 *
 * We specifically want runqueues to have a load_avg that includes
 * historical weights. Those represent the blocked load, the load we expect
 * to (shortly) return to us. This only works by keeping the weights as
 * integral part of the sum. We therefore cannot decompose as per (3).
 *
3144 3145 3146 3147 3148 3149
 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
 * runnable section of these tasks overlap (or not). If they were to perfectly
 * align the rq as a whole would be runnable 2/3 of the time. If however we
 * always have at least 1 runnable task, the rq as a whole is always runnable.
3150
 *
3151
 * So we'll have to approximate.. :/
3152
 *
3153
 * Given the constraint:
3154
 *
3155
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3156
 *
3157 3158
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
3159
 *
3160
 * On removal, we'll assume each task is equally runnable; which yields:
3161
 *
3162
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3163
 *
3164
 * XXX: only do this for the part of runnable > running ?
3165 3166 3167
 *
 */

3168
static inline void
3169
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3170 3171 3172 3173 3174 3175 3176
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

	/* Nothing to update */
	if (!delta)
		return;

3177 3178 3179 3180 3181 3182 3183 3184
	/*
	 * The relation between sum and avg is:
	 *
	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
	 *
	 * however, the PELT windows are not aligned between grq and gse.
	 */

3185 3186 3187 3188 3189 3190 3191 3192 3193 3194
	/* Set new sched_entity's utilization */
	se->avg.util_avg = gcfs_rq->avg.util_avg;
	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;

	/* Update parent cfs_rq utilization */
	add_positive(&cfs_rq->avg.util_avg, delta);
	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
}

static inline void
3195
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3196
{
3197 3198 3199 3200
	long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
	unsigned long runnable_load_avg, load_avg;
	u64 runnable_load_sum, load_sum = 0;
	s64 delta_sum;
3201

3202 3203
	if (!runnable_sum)
		return;
3204

3205
	gcfs_rq->prop_runnable_sum = 0;
3206

3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229
	if (runnable_sum >= 0) {
		/*
		 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
		 * the CPU is saturated running == runnable.
		 */
		runnable_sum += se->avg.load_sum;
		runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
	} else {
		/*
		 * Estimate the new unweighted runnable_sum of the gcfs_rq by
		 * assuming all tasks are equally runnable.
		 */
		if (scale_load_down(gcfs_rq->load.weight)) {
			load_sum = div_s64(gcfs_rq->avg.load_sum,
				scale_load_down(gcfs_rq->load.weight));
		}

		/* But make sure to not inflate se's runnable */
		runnable_sum = min(se->avg.load_sum, load_sum);
	}

	/*
	 * runnable_sum can't be lower than running_sum
3230
	 * As running sum is scale with CPU capacity wehreas the runnable sum
3231 3232 3233 3234 3235 3236
	 * is not we rescale running_sum 1st
	 */
	running_sum = se->avg.util_sum /
		arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	runnable_sum = max(runnable_sum, running_sum);

3237 3238
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3239

3240 3241
	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
	delta_avg = load_avg - se->avg.load_avg;
3242

3243 3244 3245 3246
	se->avg.load_sum = runnable_sum;
	se->avg.load_avg = load_avg;
	add_positive(&cfs_rq->avg.load_avg, delta_avg);
	add_positive(&cfs_rq->avg.load_sum, delta_sum);
3247

3248 3249
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3250 3251
	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3252

3253 3254
	se->avg.runnable_load_sum = runnable_sum;
	se->avg.runnable_load_avg = runnable_load_avg;
3255

3256
	if (se->on_rq) {
3257 3258
		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3259 3260 3261
	}
}

3262
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3263
{
3264 3265
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3266 3267 3268 3269 3270
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3271
	struct cfs_rq *cfs_rq, *gcfs_rq;
3272 3273 3274 3275

	if (entity_is_task(se))
		return 0;

3276 3277
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3278 3279
		return 0;

3280 3281
	gcfs_rq->propagate = 0;

3282 3283
	cfs_rq = cfs_rq_of(se);

3284
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3285

3286 3287
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3288 3289 3290 3291

	return 1;
}

3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310
/*
 * Check if we need to update the load and the utilization of a blocked
 * group_entity:
 */
static inline bool skip_blocked_update(struct sched_entity *se)
{
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);

	/*
	 * If sched_entity still have not zero load or utilization, we have to
	 * decay it:
	 */
	if (se->avg.load_avg || se->avg.util_avg)
		return false;

	/*
	 * If there is a pending propagation, we have to update the load and
	 * the utilization of the sched_entity:
	 */
3311
	if (gcfs_rq->propagate)
3312 3313 3314 3315 3316 3317 3318 3319 3320 3321
		return false;

	/*
	 * Otherwise, the load and the utilization of the sched_entity is
	 * already zero and there is no pending propagation, so it will be a
	 * waste of time to try to decay it:
	 */
	return true;
}

3322
#else /* CONFIG_FAIR_GROUP_SCHED */
3323

3324
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3325 3326 3327 3328 3329 3330

static inline int propagate_entity_load_avg(struct sched_entity *se)
{
	return 0;
}

3331
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3332

3333
#endif /* CONFIG_FAIR_GROUP_SCHED */
3334

3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345
/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_task()
 * @cfs_rq: cfs_rq to update
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
3346 3347 3348 3349
 * Returns true if the load decayed or we removed load.
 *
 * Since both these conditions indicate a changed cfs_rq->avg.load we should
 * call update_tg_load_avg() when this function returns true.
3350
 */
3351
static inline int
3352
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3353
{
3354
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3355
	struct sched_avg *sa = &cfs_rq->avg;
3356
	int decayed = 0;
3357

3358 3359
	if (cfs_rq->removed.nr) {
		unsigned long r;
3360
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3361 3362 3363 3364

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3365
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3366 3367 3368 3369
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3370
		sub_positive(&sa->load_avg, r);
3371
		sub_positive(&sa->load_sum, r * divider);
3372

3373
		r = removed_util;
3374
		sub_positive(&sa->util_avg, r);
3375
		sub_positive(&sa->util_sum, r * divider);
3376

3377
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3378 3379

		decayed = 1;
3380
	}
3381

3382
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3383

3384 3385 3386 3387
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3388

3389
	if (decayed)
3390
		cfs_rq_util_change(cfs_rq, 0);
3391

3392
	return decayed;
3393 3394
}

3395 3396 3397 3398 3399 3400 3401 3402
/**
 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
 * @cfs_rq: cfs_rq to attach to
 * @se: sched_entity to attach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3403
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3404
{
3405 3406 3407 3408 3409 3410 3411 3412 3413
	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;

	/*
	 * When we attach the @se to the @cfs_rq, we must align the decay
	 * window because without that, really weird and wonderful things can
	 * happen.
	 *
	 * XXX illustrate
	 */
3414
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432
	se->avg.period_contrib = cfs_rq->avg.period_contrib;

	/*
	 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
	 * period_contrib. This isn't strictly correct, but since we're
	 * entirely outside of the PELT hierarchy, nobody cares if we truncate
	 * _sum a little.
	 */
	se->avg.util_sum = se->avg.util_avg * divider;

	se->avg.load_sum = divider;
	if (se_weight(se)) {
		se->avg.load_sum =
			div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
	}

	se->avg.runnable_load_sum = se->avg.load_sum;

3433
	enqueue_load_avg(cfs_rq, se);
3434 3435
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3436 3437

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3438

3439
	cfs_rq_util_change(cfs_rq, flags);
3440 3441
}

3442 3443 3444 3445 3446 3447 3448 3449
/**
 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
 * @cfs_rq: cfs_rq to detach from
 * @se: sched_entity to detach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3450 3451
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3452
	dequeue_load_avg(cfs_rq, se);
3453 3454
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3455 3456

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3457

3458
	cfs_rq_util_change(cfs_rq, 0);
3459 3460
}

3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2
#define DO_ATTACH	0x4

/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);
	int decayed;

	/*
	 * Track task load average for carrying it to new CPU after migrated, and
	 * track group sched_entity load average for task_h_load calc in migration
	 */
	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
		__update_load_avg_se(now, cpu, cfs_rq, se);

	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
	decayed |= propagate_entity_load_avg(se);

	if (!se->avg.last_update_time && (flags & DO_ATTACH)) {

3488 3489 3490 3491 3492 3493 3494 3495
		/*
		 * DO_ATTACH means we're here from enqueue_entity().
		 * !last_update_time means we've passed through
		 * migrate_task_rq_fair() indicating we migrated.
		 *
		 * IOW we're enqueueing a task on a new CPU.
		 */
		attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
3496 3497 3498 3499 3500 3501
		update_tg_load_avg(cfs_rq, 0);

	} else if (decayed && (flags & UPDATE_TG))
		update_tg_load_avg(cfs_rq, 0);
}

3502
#ifndef CONFIG_64BIT
3503 3504
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3505
	u64 last_update_time_copy;
3506
	u64 last_update_time;
3507

3508 3509 3510 3511 3512
	do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
	} while (last_update_time != last_update_time_copy);
3513 3514 3515

	return last_update_time;
}
3516
#else
3517 3518 3519 3520
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3521 3522
#endif

3523 3524 3525 3526 3527 3528 3529 3530 3531 3532
/*
 * Synchronize entity load avg of dequeued entity without locking
 * the previous rq.
 */
void sync_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	last_update_time = cfs_rq_last_update_time(cfs_rq);
3533
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3534 3535
}

3536 3537 3538 3539 3540 3541 3542
/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
void remove_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3543
	unsigned long flags;
3544 3545

	/*
3546 3547 3548 3549 3550 3551 3552
	 * tasks cannot exit without having gone through wake_up_new_task() ->
	 * post_init_entity_util_avg() which will have added things to the
	 * cfs_rq, so we can remove unconditionally.
	 *
	 * Similarly for groups, they will have passed through
	 * post_init_entity_util_avg() before unregister_sched_fair_group()
	 * calls this.
3553 3554
	 */

3555
	sync_entity_load_avg(se);
3556 3557 3558 3559 3560

	raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
	++cfs_rq->removed.nr;
	cfs_rq->removed.util_avg	+= se->avg.util_avg;
	cfs_rq->removed.load_avg	+= se->avg.load_avg;
3561
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3562
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3563
}
3564

3565 3566
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3567
	return cfs_rq->avg.runnable_load_avg;
3568 3569 3570 3571 3572 3573 3574
}

static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.load_avg;
}

3575
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3576

3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603
static inline unsigned long task_util(struct task_struct *p)
{
	return READ_ONCE(p->se.avg.util_avg);
}

static inline unsigned long _task_util_est(struct task_struct *p)
{
	struct util_est ue = READ_ONCE(p->se.avg.util_est);

	return max(ue.ewma, ue.enqueued);
}

static inline unsigned long task_util_est(struct task_struct *p)
{
	return max(task_util(p), _task_util_est(p));
}

static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
				    struct task_struct *p)
{
	unsigned int enqueued;

	if (!sched_feat(UTIL_EST))
		return;

	/* Update root cfs_rq's estimated utilization */
	enqueued  = cfs_rq->avg.util_est.enqueued;
3604
	enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
}

/*
 * Check if a (signed) value is within a specified (unsigned) margin,
 * based on the observation that:
 *
 *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
 *
 * NOTE: this only works when value + maring < INT_MAX.
 */
static inline bool within_margin(int value, int margin)
{
	return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
}

static void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
	long last_ewma_diff;
	struct util_est ue;

	if (!sched_feat(UTIL_EST))
		return;

3630 3631 3632 3633
	/* Update root cfs_rq's estimated utilization */
	ue.enqueued  = cfs_rq->avg.util_est.enqueued;
	ue.enqueued -= min_t(unsigned int, ue.enqueued,
			     (_task_util_est(p) | UTIL_AVG_UNCHANGED));
3634 3635 3636 3637 3638 3639 3640 3641 3642
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);

	/*
	 * Skip update of task's estimated utilization when the task has not
	 * yet completed an activation, e.g. being migrated.
	 */
	if (!task_sleep)
		return;

3643 3644 3645 3646 3647 3648 3649 3650
	/*
	 * If the PELT values haven't changed since enqueue time,
	 * skip the util_est update.
	 */
	ue = p->se.avg.util_est;
	if (ue.enqueued & UTIL_AVG_UNCHANGED)
		return;

3651 3652 3653 3654
	/*
	 * Skip update of task's estimated utilization when its EWMA is
	 * already ~1% close to its last activation value.
	 */
3655
	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682
	last_ewma_diff = ue.enqueued - ue.ewma;
	if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
		return;

	/*
	 * Update Task's estimated utilization
	 *
	 * When *p completes an activation we can consolidate another sample
	 * of the task size. This is done by storing the current PELT value
	 * as ue.enqueued and by using this value to update the Exponential
	 * Weighted Moving Average (EWMA):
	 *
	 *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
	 *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
	 *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
	 *          = w * (      last_ewma_diff            ) +     ewma(t-1)
	 *          = w * (last_ewma_diff  +  ewma(t-1) / w)
	 *
	 * Where 'w' is the weight of new samples, which is configured to be
	 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
	 */
	ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
	ue.ewma  += last_ewma_diff;
	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
	WRITE_ONCE(p->se.avg.util_est, ue);
}

3683 3684
#else /* CONFIG_SMP */

3685 3686
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3687
#define DO_ATTACH	0x0
3688

3689
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3690
{
3691
	cfs_rq_util_change(cfs_rq, 0);
3692 3693
}

3694
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3695

3696
static inline void
3697
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
3698 3699 3700
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3701
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3702 3703 3704 3705
{
	return 0;
}

3706 3707 3708 3709 3710 3711 3712
static inline void
util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}

static inline void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
		 bool task_sleep) {}

3713
#endif /* CONFIG_SMP */
3714

P
Peter Zijlstra 已提交
3715 3716 3717 3718 3719 3720 3721 3722 3723
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	s64 d = se->vruntime - cfs_rq->min_vruntime;

	if (d < 0)
		d = -d;

	if (d > 3*sysctl_sched_latency)
3724
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3725 3726 3727
#endif
}

3728 3729 3730
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3731
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3732

3733 3734 3735 3736 3737 3738
	/*
	 * The 'current' period is already promised to the current tasks,
	 * however the extra weight of the new task will slow them down a
	 * little, place the new task so that it fits in the slot that
	 * stays open at the end.
	 */
P
Peter Zijlstra 已提交
3739
	if (initial && sched_feat(START_DEBIT))
3740
		vruntime += sched_vslice(cfs_rq, se);
3741

3742
	/* sleeps up to a single latency don't count. */
3743
	if (!initial) {
3744
		unsigned long thresh = sysctl_sched_latency;
3745

3746 3747 3748 3749 3750 3751
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3752

3753
		vruntime -= thresh;
3754 3755
	}

3756
	/* ensure we never gain time by being placed backwards. */
3757
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3758 3759
}

3760 3761
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773
static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
	if (schedstat_enabled())
		return;

	/* Force schedstat enabled if a dependent tracepoint is active */
	if (trace_sched_stat_wait_enabled()    ||
			trace_sched_stat_sleep_enabled()   ||
			trace_sched_stat_iowait_enabled()  ||
			trace_sched_stat_blocked_enabled() ||
			trace_sched_stat_runtime_enabled())  {
3774
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3775
			     "stat_blocked and stat_runtime require the "
3776
			     "kernel parameter schedstats=enable or "
3777 3778 3779 3780 3781
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800

/*
 * MIGRATION
 *
 *	dequeue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way the vruntime transition between RQs is done when both
 * min_vruntime are up-to-date.
 *
 * WAKEUP (remote)
 *
3801
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way we don't have the most up-to-date min_vruntime on the originating
 * CPU and an up-to-date min_vruntime on the destination CPU.
 */

3813
static void
3814
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3815
{
3816 3817 3818
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3819
	/*
3820 3821
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3822
	 */
3823
	if (renorm && curr)
3824 3825
		se->vruntime += cfs_rq->min_vruntime;

3826 3827
	update_curr(cfs_rq);

3828
	/*
3829 3830 3831 3832
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past. Being
	 * placed in the past could significantly boost this task to the
	 * fairness detriment of existing tasks.
3833
	 */
3834 3835 3836
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3837 3838 3839 3840 3841 3842 3843 3844
	/*
	 * When enqueuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Add its load to cfs_rq->runnable_avg
	 *   - For group_entity, update its weight to reflect the new share of
	 *     its group cfs_rq
	 *   - Add its new weight to cfs_rq->load.weight
	 */
3845
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3846
	update_cfs_group(se);
3847
	enqueue_runnable_load_avg(cfs_rq, se);
3848
	account_entity_enqueue(cfs_rq, se);
3849

3850
	if (flags & ENQUEUE_WAKEUP)
3851
		place_entity(cfs_rq, se, 0);
3852

3853
	check_schedstat_required();
3854 3855
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3856
	if (!curr)
3857
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3858
	se->on_rq = 1;
3859

3860
	if (cfs_rq->nr_running == 1) {
3861
		list_add_leaf_cfs_rq(cfs_rq);
3862 3863
		check_enqueue_throttle(cfs_rq);
	}
3864 3865
}

3866
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3867
{
3868 3869
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3870
		if (cfs_rq->last != se)
3871
			break;
3872 3873

		cfs_rq->last = NULL;
3874 3875
	}
}
P
Peter Zijlstra 已提交
3876

3877 3878 3879 3880
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3881
		if (cfs_rq->next != se)
3882
			break;
3883 3884

		cfs_rq->next = NULL;
3885
	}
P
Peter Zijlstra 已提交
3886 3887
}

3888 3889 3890 3891
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3892
		if (cfs_rq->skip != se)
3893
			break;
3894 3895

		cfs_rq->skip = NULL;
3896 3897 3898
	}
}

P
Peter Zijlstra 已提交
3899 3900
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3901 3902 3903 3904 3905
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3906 3907 3908

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3909 3910
}

3911
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3912

3913
static void
3914
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3915
{
3916 3917 3918 3919
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3920 3921 3922 3923 3924 3925 3926 3927 3928

	/*
	 * When dequeuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Substract its load from the cfs_rq->runnable_avg.
	 *   - Substract its previous weight from cfs_rq->load.weight.
	 *   - For group entity, update its weight to reflect the new share
	 *     of its group cfs_rq.
	 */
3929
	update_load_avg(cfs_rq, se, UPDATE_TG);
3930
	dequeue_runnable_load_avg(cfs_rq, se);
3931

3932
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3933

P
Peter Zijlstra 已提交
3934
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3935

3936
	if (se != cfs_rq->curr)
3937
		__dequeue_entity(cfs_rq, se);
3938
	se->on_rq = 0;
3939
	account_entity_dequeue(cfs_rq, se);
3940 3941

	/*
3942 3943 3944 3945
	 * Normalize after update_curr(); which will also have moved
	 * min_vruntime if @se is the one holding it back. But before doing
	 * update_min_vruntime() again, which will discount @se's position and
	 * can move min_vruntime forward still more.
3946
	 */
3947
	if (!(flags & DEQUEUE_SLEEP))
3948
		se->vruntime -= cfs_rq->min_vruntime;
3949

3950 3951 3952
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3953
	update_cfs_group(se);
3954 3955 3956 3957 3958 3959 3960 3961 3962

	/*
	 * Now advance min_vruntime if @se was the entity holding it back,
	 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
	 * put back on, and if we advance min_vruntime, we'll be placed back
	 * further than we started -- ie. we'll be penalized.
	 */
	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
		update_min_vruntime(cfs_rq);
3963 3964 3965 3966 3967
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3968
static void
I
Ingo Molnar 已提交
3969
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3970
{
3971
	unsigned long ideal_runtime, delta_exec;
3972 3973
	struct sched_entity *se;
	s64 delta;
3974

P
Peter Zijlstra 已提交
3975
	ideal_runtime = sched_slice(cfs_rq, curr);
3976
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3977
	if (delta_exec > ideal_runtime) {
3978
		resched_curr(rq_of(cfs_rq));
3979 3980 3981 3982 3983
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994
		return;
	}

	/*
	 * Ensure that a task that missed wakeup preemption by a
	 * narrow margin doesn't have to wait for a full slice.
	 * This also mitigates buddy induced latencies under load.
	 */
	if (delta_exec < sysctl_sched_min_granularity)
		return;

3995 3996
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3997

3998 3999
	if (delta < 0)
		return;
4000

4001
	if (delta > ideal_runtime)
4002
		resched_curr(rq_of(cfs_rq));
4003 4004
}

4005
static void
4006
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4007
{
4008 4009 4010 4011 4012 4013 4014
	/* 'current' is not kept within the tree. */
	if (se->on_rq) {
		/*
		 * Any task has to be enqueued before it get to execute on
		 * a CPU. So account for the time it spent waiting on the
		 * runqueue.
		 */
4015
		update_stats_wait_end(cfs_rq, se);
4016
		__dequeue_entity(cfs_rq, se);
4017
		update_load_avg(cfs_rq, se, UPDATE_TG);
4018 4019
	}

4020
	update_stats_curr_start(cfs_rq, se);
4021
	cfs_rq->curr = se;
4022

I
Ingo Molnar 已提交
4023 4024 4025 4026 4027
	/*
	 * Track our maximum slice length, if the CPU's load is at
	 * least twice that of our own weight (i.e. dont track it
	 * when there are only lesser-weight tasks around):
	 */
4028
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4029 4030 4031
		schedstat_set(se->statistics.slice_max,
			max((u64)schedstat_val(se->statistics.slice_max),
			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
I
Ingo Molnar 已提交
4032
	}
4033

4034
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4035 4036
}

4037 4038 4039
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4040 4041 4042 4043 4044 4045 4046
/*
 * Pick the next process, keeping these things in mind, in this order:
 * 1) keep things fair between processes/task groups
 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
4047 4048
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4049
{
4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060
	struct sched_entity *left = __pick_first_entity(cfs_rq);
	struct sched_entity *se;

	/*
	 * If curr is set we have to see if its left of the leftmost entity
	 * still in the tree, provided there was anything in the tree at all.
	 */
	if (!left || (curr && entity_before(curr, left)))
		left = curr;

	se = left; /* ideally we run the leftmost entity */
4061

4062 4063 4064 4065 4066
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4067 4068 4069 4070 4071 4072 4073 4074 4075 4076
		struct sched_entity *second;

		if (se == curr) {
			second = __pick_first_entity(cfs_rq);
		} else {
			second = __pick_next_entity(se);
			if (!second || (curr && entity_before(curr, second)))
				second = curr;
		}

4077 4078 4079
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4080

4081 4082 4083 4084 4085 4086
	/*
	 * Prefer last buddy, try to return the CPU to a preempted task.
	 */
	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
		se = cfs_rq->last;

4087 4088 4089 4090 4091 4092
	/*
	 * Someone really wants this to run. If it's not unfair, run it.
	 */
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;

4093
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4094 4095

	return se;
4096 4097
}

4098
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4099

4100
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4101 4102 4103 4104 4105 4106
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4107
		update_curr(cfs_rq);
4108

4109 4110 4111
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4112
	check_spread(cfs_rq, prev);
4113

4114
	if (prev->on_rq) {
4115
		update_stats_wait_start(cfs_rq, prev);
4116 4117
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4118
		/* in !on_rq case, update occurred at dequeue */
4119
		update_load_avg(cfs_rq, prev, 0);
4120
	}
4121
	cfs_rq->curr = NULL;
4122 4123
}

P
Peter Zijlstra 已提交
4124 4125
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4126 4127
{
	/*
4128
	 * Update run-time statistics of the 'current'.
4129
	 */
4130
	update_curr(cfs_rq);
4131

4132 4133 4134
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4135
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4136
	update_cfs_group(curr);
4137

P
Peter Zijlstra 已提交
4138 4139 4140 4141 4142
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4143
	if (queued) {
4144
		resched_curr(rq_of(cfs_rq));
4145 4146
		return;
	}
P
Peter Zijlstra 已提交
4147 4148 4149 4150 4151 4152 4153 4154
	/*
	 * don't let the period tick interfere with the hrtick preemption
	 */
	if (!sched_feat(DOUBLE_TICK) &&
			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
		return;
#endif

Y
Yong Zhang 已提交
4155
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4156
		check_preempt_tick(cfs_rq, curr);
4157 4158
}

4159 4160 4161 4162 4163 4164

/**************************************************
 * CFS bandwidth control machinery
 */

#ifdef CONFIG_CFS_BANDWIDTH
4165 4166

#ifdef HAVE_JUMP_LABEL
4167
static struct static_key __cfs_bandwidth_used;
4168 4169 4170

static inline bool cfs_bandwidth_used(void)
{
4171
	return static_key_false(&__cfs_bandwidth_used);
4172 4173
}

4174
void cfs_bandwidth_usage_inc(void)
4175
{
4176
	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4177 4178 4179 4180
}

void cfs_bandwidth_usage_dec(void)
{
4181
	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4182 4183 4184 4185 4186 4187 4188
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4189 4190
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4191 4192
#endif /* HAVE_JUMP_LABEL */

4193 4194 4195 4196 4197 4198 4199 4200
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4201 4202 4203 4204 4205 4206

static inline u64 sched_cfs_bandwidth_slice(void)
{
	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

P
Paul Turner 已提交
4207 4208 4209 4210 4211 4212 4213
/*
 * Replenish runtime according to assigned quota and update expiration time.
 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
 * additional synchronization around rq->lock.
 *
 * requires cfs_b->lock
 */
4214
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4215 4216 4217 4218 4219 4220 4221 4222 4223
{
	u64 now;

	if (cfs_b->quota == RUNTIME_INF)
		return;

	now = sched_clock_cpu(smp_processor_id());
	cfs_b->runtime = cfs_b->quota;
	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
4224
	cfs_b->expires_seq++;
P
Paul Turner 已提交
4225 4226
}

4227 4228 4229 4230 4231
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4232 4233 4234 4235
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
	if (unlikely(cfs_rq->throttle_count))
4236
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4237

4238
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4239 4240
}

4241 4242
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4243 4244 4245
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4246
	u64 amount = 0, min_amount, expires;
4247
	int expires_seq;
4248 4249 4250 4251 4252 4253 4254

	/* note: this is a positive sum as runtime_remaining <= 0 */
	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota == RUNTIME_INF)
		amount = min_amount;
4255
	else {
P
Peter Zijlstra 已提交
4256
		start_cfs_bandwidth(cfs_b);
4257 4258 4259 4260 4261 4262

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4263
	}
4264
	expires_seq = cfs_b->expires_seq;
P
Paul Turner 已提交
4265
	expires = cfs_b->runtime_expires;
4266 4267 4268
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4269 4270 4271 4272 4273
	/*
	 * we may have advanced our local expiration to account for allowed
	 * spread between our sched_clock and the one on which runtime was
	 * issued.
	 */
4274 4275
	if (cfs_rq->expires_seq != expires_seq) {
		cfs_rq->expires_seq = expires_seq;
P
Paul Turner 已提交
4276
		cfs_rq->runtime_expires = expires;
4277
	}
4278 4279

	return cfs_rq->runtime_remaining > 0;
4280 4281
}

P
Paul Turner 已提交
4282 4283 4284 4285 4286
/*
 * Note: This depends on the synchronization provided by sched_clock and the
 * fact that rq->clock snapshots this value.
 */
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4287
{
P
Paul Turner 已提交
4288 4289 4290
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4291
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4292 4293
		return;

P
Paul Turner 已提交
4294 4295 4296 4297 4298 4299 4300 4301 4302
	if (cfs_rq->runtime_remaining < 0)
		return;

	/*
	 * If the local deadline has passed we have to consider the
	 * possibility that our sched_clock is 'fast' and the global deadline
	 * has not truly expired.
	 *
	 * Fortunately we can check determine whether this the case by checking
4303
	 * whether the global deadline(cfs_b->expires_seq) has advanced.
P
Paul Turner 已提交
4304
	 */
4305
	if (cfs_rq->expires_seq == cfs_b->expires_seq) {
P
Paul Turner 已提交
4306 4307 4308 4309 4310 4311 4312 4313
		/* extend local deadline, drift is bounded above by 2 ticks */
		cfs_rq->runtime_expires += TICK_NSEC;
	} else {
		/* global deadline is ahead, expiration has passed */
		cfs_rq->runtime_remaining = 0;
	}
}

4314
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4315 4316
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4317
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4318 4319 4320
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4321 4322
		return;

4323 4324 4325 4326 4327
	/*
	 * if we're unable to extend our runtime we resched so that the active
	 * hierarchy can be throttled
	 */
	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4328
		resched_curr(rq_of(cfs_rq));
4329 4330
}

4331
static __always_inline
4332
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4333
{
4334
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4335 4336 4337 4338 4339
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4340 4341
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4342
	return cfs_bandwidth_used() && cfs_rq->throttled;
4343 4344
}

4345 4346 4347
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4348
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

	src_cfs_rq = tg->cfs_rq[src_cpu];
	dest_cfs_rq = tg->cfs_rq[dest_cpu];

	return throttled_hierarchy(src_cfs_rq) ||
	       throttled_hierarchy(dest_cfs_rq);
}

static int tg_unthrottle_up(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

	cfs_rq->throttle_count--;
	if (!cfs_rq->throttle_count) {
4375
		/* adjust cfs_rq_clock_task() */
4376
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4377
					     cfs_rq->throttled_clock_task;
4378 4379 4380 4381 4382 4383 4384 4385 4386 4387
	}

	return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

4388 4389
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4390
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4391 4392 4393 4394 4395
	cfs_rq->throttle_count++;

	return 0;
}

4396
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4397 4398 4399 4400 4401
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;
P
Peter Zijlstra 已提交
4402
	bool empty;
4403 4404 4405

	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

4406
	/* freeze hierarchy runnable averages while throttled */
4407 4408 4409
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
		/* throttled entity or throttle-on-deactivate */
		if (!se->on_rq)
			break;

		if (dequeue)
			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
		qcfs_rq->h_nr_running -= task_delta;

		if (qcfs_rq->load.weight)
			dequeue = 0;
	}

	if (!se)
4427
		sub_nr_running(rq, task_delta);
4428 4429

	cfs_rq->throttled = 1;
4430
	cfs_rq->throttled_clock = rq_clock(rq);
4431
	raw_spin_lock(&cfs_b->lock);
4432
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4433

4434 4435 4436 4437 4438
	/*
	 * Add to the _head_ of the list, so that an already-started
	 * distribute_cfs_runtime will not see us
	 */
	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4439 4440 4441 4442 4443 4444 4445 4446

	/*
	 * If we're the first throttled task, make sure the bandwidth
	 * timer is running.
	 */
	if (empty)
		start_cfs_bandwidth(cfs_b);

4447 4448 4449
	raw_spin_unlock(&cfs_b->lock);
}

4450
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4451 4452 4453 4454 4455 4456 4457
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	int enqueue = 1;
	long task_delta;

4458
	se = cfs_rq->tg->se[cpu_of(rq)];
4459 4460

	cfs_rq->throttled = 0;
4461 4462 4463

	update_rq_clock(rq);

4464
	raw_spin_lock(&cfs_b->lock);
4465
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4466 4467 4468
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4469 4470 4471
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489
	if (!cfs_rq->load.weight)
		return;

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		if (se->on_rq)
			enqueue = 0;

		cfs_rq = cfs_rq_of(se);
		if (enqueue)
			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
		cfs_rq->h_nr_running += task_delta;

		if (cfs_rq_throttled(cfs_rq))
			break;
	}

	if (!se)
4490
		add_nr_running(rq, task_delta);
4491

4492
	/* Determine whether we need to wake up potentially idle CPU: */
4493
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4494
		resched_curr(rq);
4495 4496 4497 4498 4499 4500
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4501 4502
	u64 runtime;
	u64 starting_runtime = remaining;
4503 4504 4505 4506 4507

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4508
		struct rq_flags rf;
4509

4510
		rq_lock(rq, &rf);
4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526
		if (!cfs_rq_throttled(cfs_rq))
			goto next;

		runtime = -cfs_rq->runtime_remaining + 1;
		if (runtime > remaining)
			runtime = remaining;
		remaining -= runtime;

		cfs_rq->runtime_remaining += runtime;
		cfs_rq->runtime_expires = expires;

		/* we check whether we're throttled above */
		if (cfs_rq->runtime_remaining > 0)
			unthrottle_cfs_rq(cfs_rq);

next:
4527
		rq_unlock(rq, &rf);
4528 4529 4530 4531 4532 4533

		if (!remaining)
			break;
	}
	rcu_read_unlock();

4534
	return starting_runtime - remaining;
4535 4536
}

4537 4538 4539 4540 4541 4542 4543 4544
/*
 * Responsible for refilling a task_group's bandwidth and unthrottling its
 * cfs_rqs as appropriate. If there has been no activity within the last
 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
 * used to track this state.
 */
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
4545
	u64 runtime, runtime_expires;
4546
	int throttled;
4547 4548 4549

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4550
		goto out_deactivate;
4551

4552
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4553
	cfs_b->nr_periods += overrun;
4554

4555 4556 4557 4558 4559 4560
	/*
	 * idle depends on !throttled (for the case of a large deficit), and if
	 * we're going inactive then everything else can be deferred
	 */
	if (cfs_b->idle && !throttled)
		goto out_deactivate;
P
Paul Turner 已提交
4561 4562 4563

	__refill_cfs_bandwidth_runtime(cfs_b);

4564 4565 4566
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4567
		return 0;
4568 4569
	}

4570 4571 4572
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4573 4574 4575
	runtime_expires = cfs_b->runtime_expires;

	/*
4576 4577 4578 4579 4580
	 * This check is repeated as we are holding onto the new bandwidth while
	 * we unthrottle. This can potentially race with an unthrottled group
	 * trying to acquire new bandwidth from the global pool. This can result
	 * in us over-using our runtime if it is all used during this loop, but
	 * only by limited amounts in that extreme case.
4581
	 */
4582 4583
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4584 4585 4586 4587 4588 4589 4590
		raw_spin_unlock(&cfs_b->lock);
		/* we can't nest cfs_b->lock while distributing bandwidth */
		runtime = distribute_cfs_runtime(cfs_b, runtime,
						 runtime_expires);
		raw_spin_lock(&cfs_b->lock);

		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4591 4592

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4593
	}
4594

4595 4596 4597 4598 4599 4600 4601
	/*
	 * While we are ensured activity in the period following an
	 * unthrottle, this also covers the case in which the new bandwidth is
	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
	 * timer to remain active while there are any throttled entities.)
	 */
	cfs_b->idle = 0;
4602

4603 4604 4605 4606
	return 0;

out_deactivate:
	return 1;
4607
}
4608

4609 4610 4611 4612 4613 4614 4615
/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;

4616 4617 4618 4619
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4620
 * hrtimer base being cleared by hrtimer_start. In the case of
4621 4622
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

	/* if the call-back is running a quota refresh is already occurring */
	if (hrtimer_callback_running(refresh_timer))
		return 1;

	/* is a quota refresh about to occur? */
	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
	if (remaining < min_expire)
		return 1;

	return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

	/* if there's a quota refresh soon don't bother with slack */
	if (runtime_refresh_within(cfs_b, min_left))
		return;

P
Peter Zijlstra 已提交
4648 4649 4650
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679
}

/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

	if (slack_runtime <= 0)
		return;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota != RUNTIME_INF &&
	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
		cfs_b->runtime += slack_runtime;

		/* we are under rq->lock, defer unthrottling using a timer */
		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
		    !list_empty(&cfs_b->throttled_cfs_rq))
			start_cfs_slack_bandwidth(cfs_b);
	}
	raw_spin_unlock(&cfs_b->lock);

	/* even if it's not valid for return we don't want to try again */
	cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
4680 4681 4682
	if (!cfs_bandwidth_used())
		return;

4683
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698
		return;

	__return_cfs_rq_runtime(cfs_rq);
}

/*
 * This is done with a timer (instead of inline with bandwidth return) since
 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
 */
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
	u64 expires;

	/* confirm we're still not at a refresh boundary */
4699 4700 4701
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4702
		return;
4703
	}
4704

4705
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4706
		runtime = cfs_b->runtime;
4707

4708 4709 4710 4711 4712 4713 4714 4715 4716 4717
	expires = cfs_b->runtime_expires;
	raw_spin_unlock(&cfs_b->lock);

	if (!runtime)
		return;

	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);

	raw_spin_lock(&cfs_b->lock);
	if (expires == cfs_b->runtime_expires)
4718
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4719 4720 4721
	raw_spin_unlock(&cfs_b->lock);
}

4722 4723 4724 4725 4726 4727 4728
/*
 * When a group wakes up we want to make sure that its quota is not already
 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
 * runtime as update_curr() throttling can not not trigger until it's on-rq.
 */
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
4729 4730 4731
	if (!cfs_bandwidth_used())
		return;

4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745
	/* an active group must be handled by the update_curr()->put() path */
	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
		return;

	/* ensure the group is not already throttled */
	if (cfs_rq_throttled(cfs_rq))
		return;

	/* update runtime allocation */
	account_cfs_rq_runtime(cfs_rq, 0);
	if (cfs_rq->runtime_remaining <= 0)
		throttle_cfs_rq(cfs_rq);
}

4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759
static void sync_throttle(struct task_group *tg, int cpu)
{
	struct cfs_rq *pcfs_rq, *cfs_rq;

	if (!cfs_bandwidth_used())
		return;

	if (!tg->parent)
		return;

	cfs_rq = tg->cfs_rq[cpu];
	pcfs_rq = tg->parent->cfs_rq[cpu];

	cfs_rq->throttle_count = pcfs_rq->throttle_count;
4760
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4761 4762
}

4763
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4764
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4765
{
4766
	if (!cfs_bandwidth_used())
4767
		return false;
4768

4769
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4770
		return false;
4771 4772 4773 4774 4775 4776

	/*
	 * it's possible for a throttled entity to be forced into a running
	 * state (e.g. set_curr_task), in this case we're finished.
	 */
	if (cfs_rq_throttled(cfs_rq))
4777
		return true;
4778 4779

	throttle_cfs_rq(cfs_rq);
4780
	return true;
4781
}
4782 4783 4784 4785 4786

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
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Peter Zijlstra 已提交
4787

4788 4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, period_timer);
	int overrun;
	int idle = 0;

4800
	raw_spin_lock(&cfs_b->lock);
4801
	for (;;) {
P
Peter Zijlstra 已提交
4802
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4803 4804 4805 4806 4807
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4808 4809
	if (idle)
		cfs_b->period_active = 0;
4810
	raw_spin_unlock(&cfs_b->lock);
4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	raw_spin_lock_init(&cfs_b->lock);
	cfs_b->runtime = 0;
	cfs_b->quota = RUNTIME_INF;
	cfs_b->period = ns_to_ktime(default_cfs_period());

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
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Peter Zijlstra 已提交
4823
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	cfs_rq->runtime_enabled = 0;
	INIT_LIST_HEAD(&cfs_rq->throttled_list);
}

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Peter Zijlstra 已提交
4835
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4836
{
4837 4838
	u64 overrun;

P
Peter Zijlstra 已提交
4839
	lockdep_assert_held(&cfs_b->lock);
4840

4841 4842 4843 4844 4845 4846 4847 4848
	if (cfs_b->period_active)
		return;

	cfs_b->period_active = 1;
	overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
	cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period);
	cfs_b->expires_seq++;
	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4849 4850 4851 4852
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4853 4854 4855 4856
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4857 4858 4859 4860
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4861
/*
4862
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
4863 4864 4865 4866 4867 4868
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
4869 4870
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4871
	struct task_group *tg;
4872

4873 4874 4875 4876 4877 4878
	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4879 4880 4881 4882 4883

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4884
	rcu_read_unlock();
4885 4886
}

4887
/* cpu offline callback */
4888
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4889
{
4890 4891 4892 4893 4894 4895 4896
	struct task_group *tg;

	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4897 4898 4899 4900 4901 4902 4903 4904

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4905
		cfs_rq->runtime_remaining = 1;
4906
		/*
4907
		 * Offline rq is schedulable till CPU is completely disabled
4908 4909 4910 4911
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

4912 4913 4914
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
4915
	rcu_read_unlock();
4916 4917 4918
}

#else /* CONFIG_CFS_BANDWIDTH */
4919 4920
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4921
	return rq_clock_task(rq_of(cfs_rq));
4922 4923
}

4924
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4925
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4926
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4927
static inline void sync_throttle(struct task_group *tg, int cpu) {}
4928
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4929 4930 4931 4932 4933

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
	return 0;
}

static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	return 0;
}
4945 4946 4947 4948 4949

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4950 4951
#endif

4952 4953 4954 4955 4956
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4957
static inline void update_runtime_enabled(struct rq *rq) {}
4958
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4959 4960 4961

#endif /* CONFIG_CFS_BANDWIDTH */

4962 4963 4964 4965
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4966 4967 4968 4969 4970 4971
#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

4972
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
4973

4974
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
4975 4976 4977 4978 4979 4980
		u64 slice = sched_slice(cfs_rq, se);
		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
		s64 delta = slice - ran;

		if (delta < 0) {
			if (rq->curr == p)
4981
				resched_curr(rq);
P
Peter Zijlstra 已提交
4982 4983
			return;
		}
4984
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4985 4986
	}
}
4987 4988 4989 4990 4991 4992 4993 4994 4995 4996

/*
 * called from enqueue/dequeue and updates the hrtick when the
 * current task is from our class and nr_running is low enough
 * to matter.
 */
static void hrtick_update(struct rq *rq)
{
	struct task_struct *curr = rq->curr;

4997
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4998 4999 5000 5001 5002
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5003
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
5004 5005 5006 5007
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5008 5009 5010 5011

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
5012 5013
#endif

5014 5015 5016 5017 5018
/*
 * The enqueue_task method is called before nr_running is
 * increased. Here we update the fair scheduling stats and
 * then put the task into the rbtree:
 */
5019
static void
5020
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5021 5022
{
	struct cfs_rq *cfs_rq;
5023
	struct sched_entity *se = &p->se;
5024

5025 5026 5027 5028 5029 5030 5031 5032
	/*
	 * The code below (indirectly) updates schedutil which looks at
	 * the cfs_rq utilization to select a frequency.
	 * Let's add the task's estimated utilization to the cfs_rq's
	 * estimated utilization, before we update schedutil.
	 */
	util_est_enqueue(&rq->cfs, p);

5033 5034 5035 5036 5037 5038
	/*
	 * If in_iowait is set, the code below may not trigger any cpufreq
	 * utilization updates, so do it here explicitly with the IOWAIT flag
	 * passed.
	 */
	if (p->in_iowait)
5039
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5040

5041
	for_each_sched_entity(se) {
5042
		if (se->on_rq)
5043 5044
			break;
		cfs_rq = cfs_rq_of(se);
5045
		enqueue_entity(cfs_rq, se, flags);
5046 5047 5048 5049 5050 5051

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running increment below.
5052
		 */
5053 5054
		if (cfs_rq_throttled(cfs_rq))
			break;
5055
		cfs_rq->h_nr_running++;
5056

5057
		flags = ENQUEUE_WAKEUP;
5058
	}
P
Peter Zijlstra 已提交
5059

P
Peter Zijlstra 已提交
5060
	for_each_sched_entity(se) {
5061
		cfs_rq = cfs_rq_of(se);
5062
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5063

5064 5065 5066
		if (cfs_rq_throttled(cfs_rq))
			break;

5067
		update_load_avg(cfs_rq, se, UPDATE_TG);
5068
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5069 5070
	}

Y
Yuyang Du 已提交
5071
	if (!se)
5072
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5073

5074
	hrtick_update(rq);
5075 5076
}

5077 5078
static void set_next_buddy(struct sched_entity *se);

5079 5080 5081 5082 5083
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5084
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5085 5086
{
	struct cfs_rq *cfs_rq;
5087
	struct sched_entity *se = &p->se;
5088
	int task_sleep = flags & DEQUEUE_SLEEP;
5089 5090 5091

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5092
		dequeue_entity(cfs_rq, se, flags);
5093 5094 5095 5096 5097 5098 5099 5100 5101

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running decrement below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
5102
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5103

5104
		/* Don't dequeue parent if it has other entities besides us */
5105
		if (cfs_rq->load.weight) {
5106 5107
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5108 5109 5110 5111
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5112 5113
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5114
			break;
5115
		}
5116
		flags |= DEQUEUE_SLEEP;
5117
	}
P
Peter Zijlstra 已提交
5118

P
Peter Zijlstra 已提交
5119
	for_each_sched_entity(se) {
5120
		cfs_rq = cfs_rq_of(se);
5121
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5122

5123 5124 5125
		if (cfs_rq_throttled(cfs_rq))
			break;

5126
		update_load_avg(cfs_rq, se, UPDATE_TG);
5127
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5128 5129
	}

Y
Yuyang Du 已提交
5130
	if (!se)
5131
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5132

5133
	util_est_dequeue(&rq->cfs, p, task_sleep);
5134
	hrtick_update(rq);
5135 5136
}

5137
#ifdef CONFIG_SMP
5138 5139 5140 5141 5142

/* Working cpumask for: load_balance, load_balance_newidle. */
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);

5143
#ifdef CONFIG_NO_HZ_COMMON
5144 5145 5146 5147 5148
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5149
 * The exact cpuload calculated at every tick would be:
5150
 *
5151 5152
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
5153 5154
 * If a CPU misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when CPU may be busy, then we have:
5155 5156 5157
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
5158 5159 5160
 *
 * decay_load_missed() below does efficient calculation of
 *
5161 5162 5163 5164 5165 5166
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
5167
 *
5168
 * The calculation is approximated on a 128 point scale.
5169 5170
 */
#define DEGRADE_SHIFT		7
5171 5172 5173 5174 5175 5176 5177 5178 5179

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208

/*
 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
 * would be when CPU is idle and so we just decay the old load without
 * adding any new load.
 */
static unsigned long
decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
{
	int j = 0;

	if (!missed_updates)
		return load;

	if (missed_updates >= degrade_zero_ticks[idx])
		return 0;

	if (idx == 1)
		return load >> missed_updates;

	while (missed_updates) {
		if (missed_updates % 2)
			load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;

		missed_updates >>= 1;
		j++;
	}
	return load;
}
5209 5210 5211 5212

static struct {
	cpumask_var_t idle_cpus_mask;
	atomic_t nr_cpus;
5213
	int has_blocked;		/* Idle CPUS has blocked load */
5214
	unsigned long next_balance;     /* in jiffy units */
5215
	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5216 5217
} nohz ____cacheline_aligned;

5218
#endif /* CONFIG_NO_HZ_COMMON */
5219

5220
/**
5221
 * __cpu_load_update - update the rq->cpu_load[] statistics
5222 5223 5224 5225
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5226
 * Update rq->cpu_load[] statistics. This function is usually called every
5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
5253
 * term.
5254
 */
5255 5256
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5257
{
5258
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269
	int i, scale;

	this_rq->nr_load_updates++;

	/* Update our load: */
	this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
	for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
		unsigned long old_load, new_load;

		/* scale is effectively 1 << i now, and >> i divides by scale */

5270
		old_load = this_rq->cpu_load[i];
5271
#ifdef CONFIG_NO_HZ_COMMON
5272
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5273 5274 5275 5276 5277 5278 5279 5280 5281
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
5282
#endif
5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

		this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
	}
}

5296
/* Used instead of source_load when we know the type == 0 */
5297
static unsigned long weighted_cpuload(struct rq *rq)
5298
{
5299
	return cfs_rq_runnable_load_avg(&rq->cfs);
5300 5301
}

5302
#ifdef CONFIG_NO_HZ_COMMON
5303 5304
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
5305
 * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
5331
		cpu_load_update(this_rq, load, pending_updates);
5332 5333 5334
	}
}

5335 5336 5337 5338
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5339
static void cpu_load_update_idle(struct rq *this_rq)
5340 5341 5342 5343
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5344
	if (weighted_cpuload(this_rq))
5345 5346
		return;

5347
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5348 5349 5350
}

/*
5351 5352 5353 5354
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
5355
 */
5356
void cpu_load_update_nohz_start(void)
5357 5358
{
	struct rq *this_rq = this_rq();
5359 5360 5361 5362 5363 5364

	/*
	 * This is all lockless but should be fine. If weighted_cpuload changes
	 * concurrently we'll exit nohz. And cpu_load write can race with
	 * cpu_load_update_idle() but both updater would be writing the same.
	 */
5365
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5366 5367 5368 5369 5370 5371 5372
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5373
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5374 5375
	struct rq *this_rq = this_rq();
	unsigned long load;
5376
	struct rq_flags rf;
5377 5378 5379 5380

	if (curr_jiffies == this_rq->last_load_update_tick)
		return;

5381
	load = weighted_cpuload(this_rq);
5382
	rq_lock(this_rq, &rf);
5383
	update_rq_clock(this_rq);
5384
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5385
	rq_unlock(this_rq, &rf);
5386
}
5387 5388 5389 5390 5391 5392 5393 5394
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
5395
#ifdef CONFIG_NO_HZ_COMMON
5396 5397
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5398
#endif
5399 5400
	cpu_load_update(this_rq, load, 1);
}
5401 5402 5403 5404

/*
 * Called from scheduler_tick()
 */
5405
void cpu_load_update_active(struct rq *this_rq)
5406
{
5407
	unsigned long load = weighted_cpuload(this_rq);
5408 5409 5410 5411 5412

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5413 5414
}

5415
/*
5416
 * Return a low guess at the load of a migration-source CPU weighted
5417 5418 5419 5420 5421 5422 5423 5424
 * according to the scheduling class and "nice" value.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static unsigned long source_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5425
	unsigned long total = weighted_cpuload(rq);
5426 5427 5428 5429 5430 5431 5432 5433

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return min(rq->cpu_load[type-1], total);
}

/*
5434
 * Return a high guess at the load of a migration-target CPU weighted
5435 5436 5437 5438 5439
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5440
	unsigned long total = weighted_cpuload(rq);
5441 5442 5443 5444 5445 5446 5447

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return max(rq->cpu_load[type-1], total);
}

5448
static unsigned long capacity_of(int cpu)
5449
{
5450
	return cpu_rq(cpu)->cpu_capacity;
5451 5452
}

5453 5454 5455 5456 5457
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5458 5459 5460
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5461
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5462
	unsigned long load_avg = weighted_cpuload(rq);
5463 5464

	if (nr_running)
5465
		return load_avg / nr_running;
5466 5467 5468 5469

	return 0;
}

P
Peter Zijlstra 已提交
5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486
static void record_wakee(struct task_struct *p)
{
	/*
	 * Only decay a single time; tasks that have less then 1 wakeup per
	 * jiffy will not have built up many flips.
	 */
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
		current->wakee_flips >>= 1;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}

M
Mike Galbraith 已提交
5487 5488
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5489
 *
M
Mike Galbraith 已提交
5490
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502
 * at a frequency roughly N times higher than one of its wakees.
 *
 * In order to determine whether we should let the load spread vs consolidating
 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.
 *
 * With both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.
 *
 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
 * whatever is irrelevant, spread criteria is apparent partner count exceeds
 * socket size.
M
Mike Galbraith 已提交
5503
 */
5504 5505
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5506 5507
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5508
	int factor = this_cpu_read(sd_llc_size);
5509

M
Mike Galbraith 已提交
5510 5511 5512 5513 5514
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5515 5516
}

5517
/*
5518 5519 5520
 * The purpose of wake_affine() is to quickly determine on which CPU we can run
 * soonest. For the purpose of speed we only consider the waking and previous
 * CPU.
5521
 *
5522 5523
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *			cache-affine and is (or	will be) idle.
5524 5525 5526 5527
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5528
 */
5529
static int
5530
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5531
{
5532 5533 5534 5535 5536
	/*
	 * If this_cpu is idle, it implies the wakeup is from interrupt
	 * context. Only allow the move if cache is shared. Otherwise an
	 * interrupt intensive workload could force all tasks onto one
	 * node depending on the IO topology or IRQ affinity settings.
5537 5538 5539 5540 5541 5542
	 *
	 * If the prev_cpu is idle and cache affine then avoid a migration.
	 * There is no guarantee that the cache hot data from an interrupt
	 * is more important than cache hot data on the prev_cpu and from
	 * a cpufreq perspective, it's better to have higher utilisation
	 * on one CPU.
5543
	 */
5544 5545
	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5546

5547
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5548
		return this_cpu;
5549

5550
	return nr_cpumask_bits;
5551 5552
}

5553
static int
5554 5555
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5556 5557 5558 5559
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5560
	this_eff_load = target_load(this_cpu, sd->wake_idx);
5561 5562 5563 5564

	if (sync) {
		unsigned long current_load = task_h_load(current);

5565
		if (current_load > this_eff_load)
5566
			return this_cpu;
5567

5568
		this_eff_load -= current_load;
5569 5570 5571 5572
	}

	task_load = task_h_load(p);

5573 5574 5575 5576
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5577

5578
	prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5579 5580 5581 5582
	prev_eff_load -= task_load;
	if (sched_feat(WA_BIAS))
		prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5583

5584 5585 5586 5587 5588 5589 5590 5591 5592 5593
	/*
	 * If sync, adjust the weight of prev_eff_load such that if
	 * prev_eff == this_eff that select_idle_sibling() will consider
	 * stacking the wakee on top of the waker if no other CPU is
	 * idle.
	 */
	if (sync)
		prev_eff_load += 1;

	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5594 5595
}

5596
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5597
		       int this_cpu, int prev_cpu, int sync)
5598
{
5599
	int target = nr_cpumask_bits;
5600

5601
	if (sched_feat(WA_IDLE))
5602
		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5603

5604 5605
	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5606

5607
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5608 5609
	if (target == nr_cpumask_bits)
		return prev_cpu;
5610

5611 5612 5613
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
	return target;
5614 5615
}

5616
static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
5617 5618 5619

static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
{
5620
	return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0);
5621 5622
}

5623 5624 5625
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
5626 5627
 *
 * Assumes p is allowed on at least one CPU in sd.
5628 5629
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5630
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5631
		  int this_cpu, int sd_flag)
5632
{
5633
	struct sched_group *idlest = NULL, *group = sd->groups;
5634
	struct sched_group *most_spare_sg = NULL;
5635 5636 5637
	unsigned long min_runnable_load = ULONG_MAX;
	unsigned long this_runnable_load = ULONG_MAX;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
5638
	unsigned long most_spare = 0, this_spare = 0;
5639
	int load_idx = sd->forkexec_idx;
5640 5641 5642
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5643

5644 5645 5646
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5647
	do {
5648 5649
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5650 5651
		int local_group;
		int i;
5652

5653
		/* Skip over this group if it has no CPUs allowed */
5654
		if (!cpumask_intersects(sched_group_span(group),
5655
					&p->cpus_allowed))
5656 5657 5658
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5659
					       sched_group_span(group));
5660

5661 5662 5663 5664
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5665
		avg_load = 0;
5666
		runnable_load = 0;
5667
		max_spare_cap = 0;
5668

5669
		for_each_cpu(i, sched_group_span(group)) {
5670
			/* Bias balancing toward CPUs of our domain */
5671 5672 5673 5674 5675
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5676 5677 5678
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5679 5680 5681 5682 5683

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5684 5685
		}

5686
		/* Adjust by relative CPU capacity of the group */
5687 5688 5689 5690
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5691 5692

		if (local_group) {
5693 5694
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5695 5696
			this_spare = max_spare_cap;
		} else {
5697 5698 5699
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
5700
				 * so we can pick this new CPU:
5701 5702 5703 5704 5705 5706 5707 5708
				 */
				min_runnable_load = runnable_load;
				min_avg_load = avg_load;
				idlest = group;
			} else if ((runnable_load < (min_runnable_load + imbalance)) &&
				   (100*min_avg_load > imbalance_scale*avg_load)) {
				/*
				 * The runnable loads are close so take the
5709
				 * blocked load into account through avg_load:
5710 5711
				 */
				min_avg_load = avg_load;
5712 5713 5714 5715 5716 5717 5718
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5719 5720 5721
		}
	} while (group = group->next, group != sd->groups);

5722 5723 5724 5725 5726 5727
	/*
	 * The cross-over point between using spare capacity or least load
	 * is too conservative for high utilization tasks on partially
	 * utilized systems if we require spare_capacity > task_util(p),
	 * so we allow for some task stuffing by using
	 * spare_capacity > task_util(p)/2.
5728 5729 5730 5731
	 *
	 * Spare capacity can't be used for fork because the utilization has
	 * not been set yet, we must first select a rq to compute the initial
	 * utilization.
5732
	 */
5733 5734 5735
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5736
	if (this_spare > task_util(p) / 2 &&
5737
	    imbalance_scale*this_spare > 100*most_spare)
5738
		return NULL;
5739 5740

	if (most_spare > task_util(p) / 2)
5741 5742
		return most_spare_sg;

5743
skip_spare:
5744 5745 5746
	if (!idlest)
		return NULL;

5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758
	/*
	 * When comparing groups across NUMA domains, it's possible for the
	 * local domain to be very lightly loaded relative to the remote
	 * domains but "imbalance" skews the comparison making remote CPUs
	 * look much more favourable. When considering cross-domain, add
	 * imbalance to the runnable load on the remote node and consider
	 * staying local.
	 */
	if ((sd->flags & SD_NUMA) &&
	    min_runnable_load + imbalance >= this_runnable_load)
		return NULL;

5759
	if (min_runnable_load > (this_runnable_load + imbalance))
5760
		return NULL;
5761 5762 5763 5764 5765

	if ((this_runnable_load < (min_runnable_load + imbalance)) &&
	     (100*this_avg_load < imbalance_scale*min_avg_load))
		return NULL;

5766 5767 5768 5769
	return idlest;
}

/*
5770
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5771 5772
 */
static int
5773
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5774 5775
{
	unsigned long load, min_load = ULONG_MAX;
5776 5777 5778 5779
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5780 5781
	int i;

5782 5783
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5784
		return cpumask_first(sched_group_span(group));
5785

5786
	/* Traverse only the allowed CPUs */
5787
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5788
		if (available_idle_cpu(i)) {
5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809
			struct rq *rq = cpu_rq(i);
			struct cpuidle_state *idle = idle_get_state(rq);
			if (idle && idle->exit_latency < min_exit_latency) {
				/*
				 * We give priority to a CPU whose idle state
				 * has the smallest exit latency irrespective
				 * of any idle timestamp.
				 */
				min_exit_latency = idle->exit_latency;
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
				   rq->idle_stamp > latest_idle_timestamp) {
				/*
				 * If equal or no active idle state, then
				 * the most recently idled CPU might have
				 * a warmer cache.
				 */
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			}
5810
		} else if (shallowest_idle_cpu == -1) {
5811
			load = weighted_cpuload(cpu_rq(i));
5812
			if (load < min_load) {
5813 5814 5815
				min_load = load;
				least_loaded_cpu = i;
			}
5816 5817 5818
		}
	}

5819
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5820
}
5821

5822 5823 5824
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
5825
	int new_cpu = cpu;
5826

5827 5828 5829
	if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
		return prev_cpu;

5830 5831 5832 5833 5834 5835 5836
	/*
	 * We need task's util for capacity_spare_wake, sync it up to prev_cpu's
	 * last_update_time.
	 */
	if (!(sd_flag & SD_BALANCE_FORK))
		sync_entity_load_avg(&p->se);

5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853
	while (sd) {
		struct sched_group *group;
		struct sched_domain *tmp;
		int weight;

		if (!(sd->flags & sd_flag)) {
			sd = sd->child;
			continue;
		}

		group = find_idlest_group(sd, p, cpu, sd_flag);
		if (!group) {
			sd = sd->child;
			continue;
		}

		new_cpu = find_idlest_group_cpu(group, p, cpu);
5854
		if (new_cpu == cpu) {
5855
			/* Now try balancing at a lower domain level of 'cpu': */
5856 5857 5858 5859
			sd = sd->child;
			continue;
		}

5860
		/* Now try balancing at a lower domain level of 'new_cpu': */
5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874
		cpu = new_cpu;
		weight = sd->span_weight;
		sd = NULL;
		for_each_domain(cpu, tmp) {
			if (weight <= tmp->span_weight)
				break;
			if (tmp->flags & sd_flag)
				sd = tmp;
		}
	}

	return new_cpu;
}

5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903
#ifdef CONFIG_SCHED_SMT

static inline void set_idle_cores(int cpu, int val)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		WRITE_ONCE(sds->has_idle_cores, val);
}

static inline bool test_idle_cores(int cpu, bool def)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		return READ_ONCE(sds->has_idle_cores);

	return def;
}

/*
 * Scans the local SMT mask to see if the entire core is idle, and records this
 * information in sd_llc_shared->has_idle_cores.
 *
 * Since SMT siblings share all cache levels, inspecting this limited remote
 * state should be fairly cheap.
 */
P
Peter Zijlstra 已提交
5904
void __update_idle_core(struct rq *rq)
5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916
{
	int core = cpu_of(rq);
	int cpu;

	rcu_read_lock();
	if (test_idle_cores(core, true))
		goto unlock;

	for_each_cpu(cpu, cpu_smt_mask(core)) {
		if (cpu == core)
			continue;

5917
		if (!available_idle_cpu(cpu))
5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933
			goto unlock;
	}

	set_idle_cores(core, 1);
unlock:
	rcu_read_unlock();
}

/*
 * Scan the entire LLC domain for idle cores; this dynamically switches off if
 * there are no idle cores left in the system; tracked through
 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
 */
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
5934
	int core, cpu;
5935

P
Peter Zijlstra 已提交
5936 5937 5938
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5939 5940 5941
	if (!test_idle_cores(target, false))
		return -1;

5942
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
5943

5944
	for_each_cpu_wrap(core, cpus, target) {
5945 5946 5947 5948
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
5949
			if (!available_idle_cpu(cpu))
5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971
				idle = false;
		}

		if (idle)
			return core;
	}

	/*
	 * Failed to find an idle core; stop looking for one.
	 */
	set_idle_cores(target, 0);

	return -1;
}

/*
 * Scan the local SMT mask for idle CPUs.
 */
static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	int cpu;

P
Peter Zijlstra 已提交
5972 5973 5974
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5975
	for_each_cpu(cpu, cpu_smt_mask(target)) {
5976
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5977
			continue;
5978
		if (available_idle_cpu(cpu))
5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002
			return cpu;
	}

	return -1;
}

#else /* CONFIG_SCHED_SMT */

static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

#endif /* CONFIG_SCHED_SMT */

/*
 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
 * average idle time for this rq (as found in rq->avg_idle).
6003
 */
6004 6005
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
6006
	struct sched_domain *this_sd;
6007
	u64 avg_cost, avg_idle;
6008 6009
	u64 time, cost;
	s64 delta;
6010
	int cpu, nr = INT_MAX;
6011

6012 6013 6014 6015
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

6016 6017 6018 6019
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
6020 6021 6022 6023
	avg_idle = this_rq()->avg_idle / 512;
	avg_cost = this_sd->avg_scan_cost + 1;

	if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6024 6025
		return -1;

6026 6027 6028 6029 6030 6031 6032 6033
	if (sched_feat(SIS_PROP)) {
		u64 span_avg = sd->span_weight * avg_idle;
		if (span_avg > 4*avg_cost)
			nr = div_u64(span_avg, avg_cost);
		else
			nr = 4;
	}

6034 6035
	time = local_clock();

6036
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6037 6038
		if (!--nr)
			return -1;
6039
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6040
			continue;
6041
		if (available_idle_cpu(cpu))
6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054
			break;
	}

	time = local_clock() - time;
	cost = this_sd->avg_scan_cost;
	delta = (s64)(time - cost) / 8;
	this_sd->avg_scan_cost += delta;

	return cpu;
}

/*
 * Try and locate an idle core/thread in the LLC cache domain.
6055
 */
6056
static int select_idle_sibling(struct task_struct *p, int prev, int target)
6057
{
6058
	struct sched_domain *sd;
6059
	int i, recent_used_cpu;
6060

6061
	if (available_idle_cpu(target))
6062
		return target;
6063 6064

	/*
6065
	 * If the previous CPU is cache affine and idle, don't be stupid:
6066
	 */
6067
	if (prev != target && cpus_share_cache(prev, target) && available_idle_cpu(prev))
6068
		return prev;
6069

6070
	/* Check a recently used CPU as a potential idle candidate: */
6071 6072 6073 6074
	recent_used_cpu = p->recent_used_cpu;
	if (recent_used_cpu != prev &&
	    recent_used_cpu != target &&
	    cpus_share_cache(recent_used_cpu, target) &&
6075
	    available_idle_cpu(recent_used_cpu) &&
6076 6077 6078
	    cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
		/*
		 * Replace recent_used_cpu with prev as it is a potential
6079
		 * candidate for the next wake:
6080 6081 6082 6083 6084
		 */
		p->recent_used_cpu = prev;
		return recent_used_cpu;
	}

6085
	sd = rcu_dereference(per_cpu(sd_llc, target));
6086 6087
	if (!sd)
		return target;
6088

6089 6090 6091
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6092

6093 6094 6095 6096 6097 6098 6099
	i = select_idle_cpu(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;

	i = select_idle_smt(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6100

6101 6102
	return target;
}
6103

6104 6105 6106 6107 6108 6109 6110
/**
 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
 * @cpu: the CPU to get the utilization of
 *
 * The unit of the return value must be the one of capacity so we can compare
 * the utilization with the capacity of the CPU that is available for CFS task
 * (ie cpu_capacity).
6111 6112 6113 6114 6115 6116 6117 6118 6119 6120
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
6121 6122 6123 6124 6125 6126 6127 6128
 * The estimated utilization of a CPU is defined to be the maximum between its
 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
 * currently RUNNABLE on that CPU.
 * This allows to properly represent the expected utilization of a CPU which
 * has just got a big task running since a long sleep period. At the same time
 * however it preserves the benefits of the "blocked utilization" in
 * describing the potential for other tasks waking up on the same CPU.
 *
6129 6130 6131 6132 6133 6134 6135 6136 6137 6138
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
6139 6140
 *
 * Return: the (estimated) utilization for the specified CPU
6141
 */
6142
static inline unsigned long cpu_util(int cpu)
6143
{
6144 6145 6146 6147 6148 6149 6150 6151
	struct cfs_rq *cfs_rq;
	unsigned int util;

	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

	if (sched_feat(UTIL_EST))
		util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6152

6153
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6154
}
6155

6156
/*
6157
 * cpu_util_wake: Compute CPU utilization with any contributions from
6158 6159
 * the waking task p removed.
 */
6160
static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
6161
{
6162 6163
	struct cfs_rq *cfs_rq;
	unsigned int util;
6164 6165

	/* Task has no contribution or is new */
6166
	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6167 6168
		return cpu_util(cpu);

6169 6170 6171 6172 6173
	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

	/* Discount task's blocked util from CPU's util */
	util -= min_t(unsigned int, util, task_util(p));
6174

6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209
	/*
	 * Covered cases:
	 *
	 * a) if *p is the only task sleeping on this CPU, then:
	 *      cpu_util (== task_util) > util_est (== 0)
	 *    and thus we return:
	 *      cpu_util_wake = (cpu_util - task_util) = 0
	 *
	 * b) if other tasks are SLEEPING on this CPU, which is now exiting
	 *    IDLE, then:
	 *      cpu_util >= task_util
	 *      cpu_util > util_est (== 0)
	 *    and thus we discount *p's blocked utilization to return:
	 *      cpu_util_wake = (cpu_util - task_util) >= 0
	 *
	 * c) if other tasks are RUNNABLE on that CPU and
	 *      util_est > cpu_util
	 *    then we use util_est since it returns a more restrictive
	 *    estimation of the spare capacity on that CPU, by just
	 *    considering the expected utilization of tasks already
	 *    runnable on that CPU.
	 *
	 * Cases a) and b) are covered by the above code, while case c) is
	 * covered by the following code when estimated utilization is
	 * enabled.
	 */
	if (sched_feat(UTIL_EST))
		util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));

	/*
	 * Utilization (estimated) can exceed the CPU capacity, thus let's
	 * clamp to the maximum CPU capacity to ensure consistency with
	 * the cpu_util call.
	 */
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6210 6211
}

6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229
/*
 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
 *
 * In that case WAKE_AFFINE doesn't make sense and we'll let
 * BALANCE_WAKE sort things out.
 */
static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
{
	long min_cap, max_cap;

	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;

	/* Minimum capacity is close to max, no need to abort wake_affine */
	if (max_cap - min_cap < max_cap >> 3)
		return 0;

6230 6231 6232
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6233 6234 6235
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6236
/*
6237 6238 6239
 * select_task_rq_fair: Select target runqueue for the waking task in domains
 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6240
 *
6241 6242
 * Balances load by selecting the idlest CPU in the idlest group, or under
 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6243
 *
6244
 * Returns the target CPU number.
6245 6246 6247
 *
 * preempt must be disabled.
 */
6248
static int
6249
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6250
{
6251
	struct sched_domain *tmp, *sd = NULL;
6252
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6253
	int new_cpu = prev_cpu;
6254
	int want_affine = 0;
6255
	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6256

P
Peter Zijlstra 已提交
6257 6258
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6259
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6260
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6261
	}
6262

6263
	rcu_read_lock();
6264
	for_each_domain(cpu, tmp) {
6265
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6266
			break;
6267

6268
		/*
6269
		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6270
		 * cpu is a valid SD_WAKE_AFFINE target.
6271
		 */
6272 6273
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6274 6275 6276 6277
			if (cpu != prev_cpu)
				new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);

			sd = NULL; /* Prefer wake_affine over balance flags */
6278
			break;
6279
		}
6280

6281
		if (tmp->flags & sd_flag)
6282
			sd = tmp;
M
Mike Galbraith 已提交
6283 6284
		else if (!want_affine)
			break;
6285 6286
	}

6287 6288
	if (unlikely(sd)) {
		/* Slow path */
6289
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6290 6291 6292 6293 6294 6295 6296
	} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
		/* Fast path */

		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);

		if (want_affine)
			current->recent_used_cpu = cpu;
6297
	}
6298
	rcu_read_unlock();
6299

6300
	return new_cpu;
6301
}
6302

6303 6304
static void detach_entity_cfs_rq(struct sched_entity *se);

6305
/*
6306
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6307
 * cfs_rq_of(p) references at time of call are still valid and identify the
6308
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6309
 */
6310
static void migrate_task_rq_fair(struct task_struct *p)
6311
{
6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337
	/*
	 * As blocked tasks retain absolute vruntime the migration needs to
	 * deal with this by subtracting the old and adding the new
	 * min_vruntime -- the latter is done by enqueue_entity() when placing
	 * the task on the new runqueue.
	 */
	if (p->state == TASK_WAKING) {
		struct sched_entity *se = &p->se;
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 min_vruntime;

#ifndef CONFIG_64BIT
		u64 min_vruntime_copy;

		do {
			min_vruntime_copy = cfs_rq->min_vruntime_copy;
			smp_rmb();
			min_vruntime = cfs_rq->min_vruntime;
		} while (min_vruntime != min_vruntime_copy);
#else
		min_vruntime = cfs_rq->min_vruntime;
#endif

		se->vruntime -= min_vruntime;
	}

6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356
	if (p->on_rq == TASK_ON_RQ_MIGRATING) {
		/*
		 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
		 * rq->lock and can modify state directly.
		 */
		lockdep_assert_held(&task_rq(p)->lock);
		detach_entity_cfs_rq(&p->se);

	} else {
		/*
		 * We are supposed to update the task to "current" time, then
		 * its up to date and ready to go to new CPU/cfs_rq. But we
		 * have difficulty in getting what current time is, so simply
		 * throw away the out-of-date time. This will result in the
		 * wakee task is less decayed, but giving the wakee more load
		 * sounds not bad.
		 */
		remove_entity_load_avg(&p->se);
	}
6357 6358 6359

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6360 6361

	/* We have migrated, no longer consider this task hot */
6362
	p->se.exec_start = 0;
6363
}
6364 6365 6366 6367 6368

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6369 6370
#endif /* CONFIG_SMP */

6371
static unsigned long wakeup_gran(struct sched_entity *se)
6372 6373 6374 6375
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6376 6377
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6378 6379 6380 6381 6382 6383 6384 6385 6386
	 *
	 * By using 'se' instead of 'curr' we penalize light tasks, so
	 * they get preempted easier. That is, if 'se' < 'curr' then
	 * the resulting gran will be larger, therefore penalizing the
	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
	 * be smaller, again penalizing the lighter task.
	 *
	 * This is especially important for buddies when the leftmost
	 * task is higher priority than the buddy.
6387
	 */
6388
	return calc_delta_fair(gran, se);
6389 6390
}

6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412
/*
 * Should 'se' preempt 'curr'.
 *
 *             |s1
 *        |s2
 *   |s3
 *         g
 *      |<--->|c
 *
 *  w(c, s1) = -1
 *  w(c, s2) =  0
 *  w(c, s3) =  1
 *
 */
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
	s64 gran, vdiff = curr->vruntime - se->vruntime;

	if (vdiff <= 0)
		return -1;

6413
	gran = wakeup_gran(se);
6414 6415 6416 6417 6418 6419
	if (vdiff > gran)
		return 1;

	return 0;
}

6420 6421
static void set_last_buddy(struct sched_entity *se)
{
6422 6423 6424
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6425 6426 6427
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6428
		cfs_rq_of(se)->last = se;
6429
	}
6430 6431 6432 6433
}

static void set_next_buddy(struct sched_entity *se)
{
6434 6435 6436
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6437 6438 6439
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6440
		cfs_rq_of(se)->next = se;
6441
	}
6442 6443
}

6444 6445
static void set_skip_buddy(struct sched_entity *se)
{
6446 6447
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6448 6449
}

6450 6451 6452
/*
 * Preempt the current task with a newly woken task if needed:
 */
6453
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6454 6455
{
	struct task_struct *curr = rq->curr;
6456
	struct sched_entity *se = &curr->se, *pse = &p->se;
6457
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6458
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6459
	int next_buddy_marked = 0;
6460

I
Ingo Molnar 已提交
6461 6462 6463
	if (unlikely(se == pse))
		return;

6464
	/*
6465
	 * This is possible from callers such as attach_tasks(), in which we
6466 6467 6468 6469 6470 6471 6472
	 * unconditionally check_prempt_curr() after an enqueue (which may have
	 * lead to a throttle).  This both saves work and prevents false
	 * next-buddy nomination below.
	 */
	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
		return;

6473
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6474
		set_next_buddy(pse);
6475 6476
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6477

6478 6479 6480
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6481 6482 6483 6484 6485 6486
	 *
	 * Note: this also catches the edge-case of curr being in a throttled
	 * group (e.g. via set_curr_task), since update_curr() (in the
	 * enqueue of curr) will have resulted in resched being set.  This
	 * prevents us from potentially nominating it as a false LAST_BUDDY
	 * below.
6487 6488 6489 6490
	 */
	if (test_tsk_need_resched(curr))
		return;

6491 6492 6493 6494 6495
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6496
	/*
6497 6498
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6499
	 */
6500
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6501
		return;
6502

6503
	find_matching_se(&se, &pse);
6504
	update_curr(cfs_rq_of(se));
6505
	BUG_ON(!pse);
6506 6507 6508 6509 6510 6511 6512
	if (wakeup_preempt_entity(se, pse) == 1) {
		/*
		 * Bias pick_next to pick the sched entity that is
		 * triggering this preemption.
		 */
		if (!next_buddy_marked)
			set_next_buddy(pse);
6513
		goto preempt;
6514
	}
6515

6516
	return;
6517

6518
preempt:
6519
	resched_curr(rq);
6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533
	/*
	 * Only set the backward buddy when the current task is still
	 * on the rq. This can happen when a wakeup gets interleaved
	 * with schedule on the ->pre_schedule() or idle_balance()
	 * point, either of which can * drop the rq lock.
	 *
	 * Also, during early boot the idle thread is in the fair class,
	 * for obvious reasons its a bad idea to schedule back to it.
	 */
	if (unlikely(!se->on_rq || curr == rq->idle))
		return;

	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
		set_last_buddy(se);
6534 6535
}

6536
static struct task_struct *
6537
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6538 6539 6540
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6541
	struct task_struct *p;
6542
	int new_tasks;
6543

6544
again:
6545
	if (!cfs_rq->nr_running)
6546
		goto idle;
6547

6548
#ifdef CONFIG_FAIR_GROUP_SCHED
6549
	if (prev->sched_class != &fair_sched_class)
6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568
		goto simple;

	/*
	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
	 * likely that a next task is from the same cgroup as the current.
	 *
	 * Therefore attempt to avoid putting and setting the entire cgroup
	 * hierarchy, only change the part that actually changes.
	 */

	do {
		struct sched_entity *curr = cfs_rq->curr;

		/*
		 * Since we got here without doing put_prev_entity() we also
		 * have to consider cfs_rq->curr. If it is still a runnable
		 * entity, update_curr() will update its vruntime, otherwise
		 * forget we've ever seen it.
		 */
6569 6570 6571 6572 6573
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6574

6575 6576 6577
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6578
			 * Therefore the nr_running test will indeed
6579 6580
			 * be correct.
			 */
6581 6582 6583 6584 6585 6586
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6587
				goto simple;
6588
			}
6589
		}
6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622

		se = pick_next_entity(cfs_rq, curr);
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

	p = task_of(se);

	/*
	 * Since we haven't yet done put_prev_entity and if the selected task
	 * is a different task than we started out with, try and touch the
	 * least amount of cfs_rqs.
	 */
	if (prev != p) {
		struct sched_entity *pse = &prev->se;

		while (!(cfs_rq = is_same_group(se, pse))) {
			int se_depth = se->depth;
			int pse_depth = pse->depth;

			if (se_depth <= pse_depth) {
				put_prev_entity(cfs_rq_of(pse), pse);
				pse = parent_entity(pse);
			}
			if (se_depth >= pse_depth) {
				set_next_entity(cfs_rq_of(se), se);
				se = parent_entity(se);
			}
		}

		put_prev_entity(cfs_rq, pse);
		set_next_entity(cfs_rq, se);
	}

6623
	goto done;
6624 6625
simple:
#endif
6626

6627
	put_prev_task(rq, prev);
6628

6629
	do {
6630
		se = pick_next_entity(cfs_rq, NULL);
6631
		set_next_entity(cfs_rq, se);
6632 6633 6634
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6635
	p = task_of(se);
6636

6637
done: __maybe_unused;
6638 6639 6640 6641 6642 6643 6644 6645 6646
#ifdef CONFIG_SMP
	/*
	 * Move the next running task to the front of
	 * the list, so our cfs_tasks list becomes MRU
	 * one.
	 */
	list_move(&p->se.group_node, &rq->cfs_tasks);
#endif

6647 6648
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6649 6650

	return p;
6651 6652

idle:
6653 6654
	new_tasks = idle_balance(rq, rf);

6655 6656 6657 6658 6659
	/*
	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
	 * possible for any higher priority task to appear. In that case we
	 * must re-start the pick_next_entity() loop.
	 */
6660
	if (new_tasks < 0)
6661 6662
		return RETRY_TASK;

6663
	if (new_tasks > 0)
6664 6665 6666
		goto again;

	return NULL;
6667 6668 6669 6670 6671
}

/*
 * Account for a descheduled task:
 */
6672
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6673 6674 6675 6676 6677 6678
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6679
		put_prev_entity(cfs_rq, se);
6680 6681 6682
	}
}

6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707
/*
 * sched_yield() is very simple
 *
 * The magic of dealing with the ->skip buddy is in pick_next_entity.
 */
static void yield_task_fair(struct rq *rq)
{
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *se = &curr->se;

	/*
	 * Are we the only task in the tree?
	 */
	if (unlikely(rq->nr_running == 1))
		return;

	clear_buddies(cfs_rq, se);

	if (curr->policy != SCHED_BATCH) {
		update_rq_clock(rq);
		/*
		 * Update run-time statistics of the 'current'.
		 */
		update_curr(cfs_rq);
6708 6709 6710 6711 6712
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6713
		rq_clock_skip_update(rq);
6714 6715 6716 6717 6718
	}

	set_skip_buddy(se);
}

6719 6720 6721 6722
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6723 6724
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6725 6726 6727 6728 6729 6730 6731 6732 6733 6734
		return false;

	/* Tell the scheduler that we'd really like pse to run next. */
	set_next_buddy(se);

	yield_task_fair(rq);

	return true;
}

6735
#ifdef CONFIG_SMP
6736
/**************************************************
P
Peter Zijlstra 已提交
6737 6738 6739 6740 6741
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
6742
 * per-CPU scheduler provides, namely provide a proportional amount of compute
P
Peter Zijlstra 已提交
6743 6744 6745 6746
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
6747
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
P
Peter Zijlstra 已提交
6748 6749 6750 6751
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
6752
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
6753
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6754 6755 6756 6757 6758 6759
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
6760
 * C_i is the compute capacity of CPU i, typically it is the
P
Peter Zijlstra 已提交
6761 6762 6763 6764 6765 6766
 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
 * can also include other factors [XXX].
 *
 * To achieve this balance we define a measure of imbalance which follows
 * directly from (1):
 *
6767
 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
P
Peter Zijlstra 已提交
6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780
 *
 * We them move tasks around to minimize the imbalance. In the continuous
 * function space it is obvious this converges, in the discrete case we get
 * a few fun cases generally called infeasible weight scenarios.
 *
 * [XXX expand on:
 *     - infeasible weights;
 *     - local vs global optima in the discrete case. ]
 *
 *
 * SCHED DOMAINS
 *
 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6781
 * for all i,j solution, we create a tree of CPUs that follows the hardware
P
Peter Zijlstra 已提交
6782
 * topology where each level pairs two lower groups (or better). This results
6783
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
P
Peter Zijlstra 已提交
6784
 * tree to only the first of the previous level and we decrease the frequency
6785
 * of load-balance at each level inv. proportional to the number of CPUs in
P
Peter Zijlstra 已提交
6786 6787 6788 6789 6790 6791 6792 6793
 * the groups.
 *
 * This yields:
 *
 *     log_2 n     1     n
 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
 *     i = 0      2^i   2^i
 *                               `- size of each group
6794
 *         |         |     `- number of CPUs doing load-balance
P
Peter Zijlstra 已提交
6795 6796 6797 6798 6799 6800 6801
 *         |         `- freq
 *         `- sum over all levels
 *
 * Coupled with a limit on how many tasks we can migrate every balance pass,
 * this makes (5) the runtime complexity of the balancer.
 *
 * An important property here is that each CPU is still (indirectly) connected
6802
 * to every other CPU in at most O(log n) steps:
P
Peter Zijlstra 已提交
6803 6804 6805
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6806
 *             log_2 n
P
Peter Zijlstra 已提交
6807 6808 6809 6810 6811 6812 6813
 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
 *             k = 0
 *
 * And you'll find that:
 *
 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
 *
6814
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
P
Peter Zijlstra 已提交
6815 6816 6817 6818 6819 6820 6821 6822 6823
 * The task movement gives a factor of O(m), giving a convergence complexity
 * of:
 *
 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
 *
 *
 * WORK CONSERVING
 *
 * In order to avoid CPUs going idle while there's still work to do, new idle
6824
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
P
Peter Zijlstra 已提交
6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844
 * tree itself instead of relying on other CPUs to bring it work.
 *
 * This adds some complexity to both (5) and (8) but it reduces the total idle
 * time.
 *
 * [XXX more?]
 *
 *
 * CGROUPS
 *
 * Cgroups make a horror show out of (2), instead of a simple sum we get:
 *
 *                                s_k,i
 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
 *                                 S_k
 *
 * Where
 *
 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
 *
6845
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
P
Peter Zijlstra 已提交
6846 6847 6848 6849 6850 6851
 *
 * The big problem is S_k, its a global sum needed to compute a local (W_i)
 * property.
 *
 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
 *      rewrite all of this once again.]
6852
 */
6853

6854 6855
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6856 6857
enum fbq_type { regular, remote, all };

6858
#define LBF_ALL_PINNED	0x01
6859
#define LBF_NEED_BREAK	0x02
6860 6861
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6862
#define LBF_NOHZ_STATS	0x10
6863
#define LBF_NOHZ_AGAIN	0x20
6864 6865 6866 6867 6868

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6869
	int			src_cpu;
6870 6871 6872 6873

	int			dst_cpu;
	struct rq		*dst_rq;

6874 6875
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6876
	enum cpu_idle_type	idle;
6877
	long			imbalance;
6878 6879 6880
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6881
	unsigned int		flags;
6882 6883 6884 6885

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6886 6887

	enum fbq_type		fbq_type;
6888
	struct list_head	tasks;
6889 6890
};

6891 6892 6893
/*
 * Is this task likely cache-hot:
 */
6894
static int task_hot(struct task_struct *p, struct lb_env *env)
6895 6896 6897
{
	s64 delta;

6898 6899
	lockdep_assert_held(&env->src_rq->lock);

6900 6901 6902 6903 6904 6905 6906 6907 6908
	if (p->sched_class != &fair_sched_class)
		return 0;

	if (unlikely(p->policy == SCHED_IDLE))
		return 0;

	/*
	 * Buddy candidates are cache hot:
	 */
6909
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6910 6911 6912 6913 6914 6915 6916 6917 6918
			(&p->se == cfs_rq_of(&p->se)->next ||
			 &p->se == cfs_rq_of(&p->se)->last))
		return 1;

	if (sysctl_sched_migration_cost == -1)
		return 1;
	if (sysctl_sched_migration_cost == 0)
		return 0;

6919
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6920 6921 6922 6923

	return delta < (s64)sysctl_sched_migration_cost;
}

6924
#ifdef CONFIG_NUMA_BALANCING
6925
/*
6926 6927 6928
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
6929
 */
6930
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6931
{
6932
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6933
	unsigned long src_faults, dst_faults;
6934 6935
	int src_nid, dst_nid;

6936
	if (!static_branch_likely(&sched_numa_balancing))
6937 6938
		return -1;

6939
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6940
		return -1;
6941 6942 6943 6944

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

6945
	if (src_nid == dst_nid)
6946
		return -1;
6947

6948 6949 6950 6951 6952 6953 6954
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid) {
		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
			return 1;
		else
			return -1;
	}
6955

6956 6957
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6958
		return 0;
6959

6960 6961 6962 6963
	/* Leaving a core idle is often worse than degrading locality. */
	if (env->idle != CPU_NOT_IDLE)
		return -1;

6964 6965 6966 6967 6968 6969
	if (numa_group) {
		src_faults = group_faults(p, src_nid);
		dst_faults = group_faults(p, dst_nid);
	} else {
		src_faults = task_faults(p, src_nid);
		dst_faults = task_faults(p, dst_nid);
6970 6971
	}

6972
	return dst_faults < src_faults;
6973 6974
}

6975
#else
6976
static inline int migrate_degrades_locality(struct task_struct *p,
6977 6978
					     struct lb_env *env)
{
6979
	return -1;
6980
}
6981 6982
#endif

6983 6984 6985 6986
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6987
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6988
{
6989
	int tsk_cache_hot;
6990 6991 6992

	lockdep_assert_held(&env->src_rq->lock);

6993 6994
	/*
	 * We do not migrate tasks that are:
6995
	 * 1) throttled_lb_pair, or
6996
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6997 6998
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6999
	 */
7000 7001 7002
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

7003
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7004
		int cpu;
7005

7006
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7007

7008 7009
		env->flags |= LBF_SOME_PINNED;

7010
		/*
7011
		 * Remember if this task can be migrated to any other CPU in
7012 7013 7014
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
7015 7016
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
7017
		 */
7018
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7019 7020
			return 0;

7021
		/* Prevent to re-select dst_cpu via env's CPUs: */
7022
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7023
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7024
				env->flags |= LBF_DST_PINNED;
7025 7026 7027
				env->new_dst_cpu = cpu;
				break;
			}
7028
		}
7029

7030 7031
		return 0;
	}
7032 7033

	/* Record that we found atleast one task that could run on dst_cpu */
7034
	env->flags &= ~LBF_ALL_PINNED;
7035

7036
	if (task_running(env->src_rq, p)) {
7037
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7038 7039 7040 7041 7042
		return 0;
	}

	/*
	 * Aggressive migration if:
7043 7044 7045
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
7046
	 */
7047 7048 7049
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7050

7051
	if (tsk_cache_hot <= 0 ||
7052
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7053
		if (tsk_cache_hot == 1) {
7054 7055
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7056
		}
7057 7058 7059
		return 1;
	}

7060
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7061
	return 0;
7062 7063
}

7064
/*
7065 7066 7067 7068 7069 7070 7071
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

	p->on_rq = TASK_ON_RQ_MIGRATING;
7072
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7073 7074 7075
	set_task_cpu(p, env->dst_cpu);
}

7076
/*
7077
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7078 7079
 * part of active balancing operations within "domain".
 *
7080
 * Returns a task if successful and NULL otherwise.
7081
 */
7082
static struct task_struct *detach_one_task(struct lb_env *env)
7083
{
7084
	struct task_struct *p;
7085

7086 7087
	lockdep_assert_held(&env->src_rq->lock);

7088 7089
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7090 7091
		if (!can_migrate_task(p, env))
			continue;
7092

7093
		detach_task(p, env);
7094

7095
		/*
7096
		 * Right now, this is only the second place where
7097
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7098
		 * so we can safely collect stats here rather than
7099
		 * inside detach_tasks().
7100
		 */
7101
		schedstat_inc(env->sd->lb_gained[env->idle]);
7102
		return p;
7103
	}
7104
	return NULL;
7105 7106
}

7107 7108
static const unsigned int sched_nr_migrate_break = 32;

7109
/*
7110 7111
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7112
 *
7113
 * Returns number of detached tasks if successful and 0 otherwise.
7114
 */
7115
static int detach_tasks(struct lb_env *env)
7116
{
7117 7118
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7119
	unsigned long load;
7120 7121 7122
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7123

7124
	if (env->imbalance <= 0)
7125
		return 0;
7126

7127
	while (!list_empty(tasks)) {
7128 7129 7130 7131 7132 7133 7134
		/*
		 * We don't want to steal all, otherwise we may be treated likewise,
		 * which could at worst lead to a livelock crash.
		 */
		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
			break;

7135
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7136

7137 7138
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7139
		if (env->loop > env->loop_max)
7140
			break;
7141 7142

		/* take a breather every nr_migrate tasks */
7143
		if (env->loop > env->loop_break) {
7144
			env->loop_break += sched_nr_migrate_break;
7145
			env->flags |= LBF_NEED_BREAK;
7146
			break;
7147
		}
7148

7149
		if (!can_migrate_task(p, env))
7150 7151 7152
			goto next;

		load = task_h_load(p);
7153

7154
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7155 7156
			goto next;

7157
		if ((load / 2) > env->imbalance)
7158
			goto next;
7159

7160 7161 7162 7163
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7164
		env->imbalance -= load;
7165 7166

#ifdef CONFIG_PREEMPT
7167 7168
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7169
		 * kernels will stop after the first task is detached to minimize
7170 7171
		 * the critical section.
		 */
7172
		if (env->idle == CPU_NEWLY_IDLE)
7173
			break;
7174 7175
#endif

7176 7177 7178 7179
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7180
		if (env->imbalance <= 0)
7181
			break;
7182 7183 7184

		continue;
next:
7185
		list_move(&p->se.group_node, tasks);
7186
	}
7187

7188
	/*
7189 7190 7191
	 * Right now, this is one of only two places we collect this stat
	 * so we can safely collect detach_one_task() stats here rather
	 * than inside detach_one_task().
7192
	 */
7193
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7194

7195 7196 7197 7198 7199 7200 7201 7202 7203 7204 7205
	return detached;
}

/*
 * attach_task() -- attach the task detached by detach_task() to its new rq.
 */
static void attach_task(struct rq *rq, struct task_struct *p)
{
	lockdep_assert_held(&rq->lock);

	BUG_ON(task_rq(p) != rq);
7206
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7207
	p->on_rq = TASK_ON_RQ_QUEUED;
7208 7209 7210 7211 7212 7213 7214 7215 7216
	check_preempt_curr(rq, p, 0);
}

/*
 * attach_one_task() -- attaches the task returned from detach_one_task() to
 * its new rq.
 */
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
7217 7218 7219
	struct rq_flags rf;

	rq_lock(rq, &rf);
7220
	update_rq_clock(rq);
7221
	attach_task(rq, p);
7222
	rq_unlock(rq, &rf);
7223 7224 7225 7226 7227 7228 7229 7230 7231 7232
}

/*
 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
 * new rq.
 */
static void attach_tasks(struct lb_env *env)
{
	struct list_head *tasks = &env->tasks;
	struct task_struct *p;
7233
	struct rq_flags rf;
7234

7235
	rq_lock(env->dst_rq, &rf);
7236
	update_rq_clock(env->dst_rq);
7237 7238 7239 7240

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7241

7242 7243 7244
		attach_task(env->dst_rq, p);
	}

7245
	rq_unlock(env->dst_rq, &rf);
7246 7247
}

7248 7249 7250 7251 7252 7253 7254 7255 7256 7257 7258
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->avg.load_avg)
		return true;

	if (cfs_rq->avg.util_avg)
		return true;

	return false;
}

7259
static inline bool others_have_blocked(struct rq *rq)
7260 7261 7262 7263
{
	if (READ_ONCE(rq->avg_rt.util_avg))
		return true;

7264 7265 7266
	if (READ_ONCE(rq->avg_dl.util_avg))
		return true;

7267 7268 7269 7270 7271
#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
	if (READ_ONCE(rq->avg_irq.util_avg))
		return true;
#endif

7272 7273 7274
	return false;
}

7275 7276
#ifdef CONFIG_FAIR_GROUP_SCHED

7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->load.weight)
		return false;

	if (cfs_rq->avg.load_sum)
		return false;

	if (cfs_rq->avg.util_sum)
		return false;

7288
	if (cfs_rq->avg.runnable_load_sum)
7289 7290 7291 7292 7293
		return false;

	return true;
}

7294
static void update_blocked_averages(int cpu)
7295 7296
{
	struct rq *rq = cpu_rq(cpu);
7297
	struct cfs_rq *cfs_rq, *pos;
7298
	struct rq_flags rf;
7299
	bool done = true;
7300

7301
	rq_lock_irqsave(rq, &rf);
7302
	update_rq_clock(rq);
7303

7304 7305 7306 7307
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7308
	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7309 7310
		struct sched_entity *se;

7311 7312 7313
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7314

7315
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7316
			update_tg_load_avg(cfs_rq, 0);
7317

7318 7319 7320
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7321
			update_load_avg(cfs_rq_of(se), se, 0);
7322 7323 7324 7325 7326 7327 7328

		/*
		 * There can be a lot of idle CPU cgroups.  Don't let fully
		 * decayed cfs_rqs linger on the list.
		 */
		if (cfs_rq_is_decayed(cfs_rq))
			list_del_leaf_cfs_rq(cfs_rq);
7329 7330 7331

		/* Don't need periodic decay once load/util_avg are null */
		if (cfs_rq_has_blocked(cfs_rq))
7332
			done = false;
7333
	}
7334
	update_rt_rq_load_avg(rq_clock_task(rq), rq, 0);
7335
	update_dl_rq_load_avg(rq_clock_task(rq), rq, 0);
7336
	update_irq_load_avg(rq, 0);
7337
	/* Don't need periodic decay once load/util_avg are null */
7338
	if (others_have_blocked(rq))
7339
		done = false;
7340 7341 7342

#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7343 7344
	if (done)
		rq->has_blocked_load = 0;
7345
#endif
7346
	rq_unlock_irqrestore(rq, &rf);
7347 7348
}

7349
/*
7350
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7351 7352 7353
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7354
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7355
{
7356 7357
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7358
	unsigned long now = jiffies;
7359
	unsigned long load;
7360

7361
	if (cfs_rq->last_h_load_update == now)
7362 7363
		return;

7364 7365 7366 7367 7368 7369 7370
	cfs_rq->h_load_next = NULL;
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		cfs_rq->h_load_next = se;
		if (cfs_rq->last_h_load_update == now)
			break;
	}
7371

7372
	if (!se) {
7373
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7374 7375 7376 7377 7378
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
7379 7380
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7381 7382 7383 7384
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7385 7386
}

7387
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7388
{
7389
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7390

7391
	update_cfs_rq_h_load(cfs_rq);
7392
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7393
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7394 7395
}
#else
7396
static inline void update_blocked_averages(int cpu)
7397
{
7398 7399
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7400
	struct rq_flags rf;
7401

7402
	rq_lock_irqsave(rq, &rf);
7403
	update_rq_clock(rq);
7404
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7405
	update_rt_rq_load_avg(rq_clock_task(rq), rq, 0);
7406
	update_dl_rq_load_avg(rq_clock_task(rq), rq, 0);
7407
	update_irq_load_avg(rq, 0);
7408 7409
#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7410
	if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq))
7411
		rq->has_blocked_load = 0;
7412
#endif
7413
	rq_unlock_irqrestore(rq, &rf);
7414 7415
}

7416
static unsigned long task_h_load(struct task_struct *p)
7417
{
7418
	return p->se.avg.load_avg;
7419
}
P
Peter Zijlstra 已提交
7420
#endif
7421 7422

/********** Helpers for find_busiest_group ************************/
7423 7424 7425 7426 7427 7428 7429

enum group_type {
	group_other = 0,
	group_imbalanced,
	group_overloaded,
};

7430 7431 7432 7433 7434 7435 7436
/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
	unsigned long avg_load; /*Avg load across the CPUs of the group */
	unsigned long group_load; /* Total load over the CPUs of the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
J
Joonsoo Kim 已提交
7437
	unsigned long load_per_task;
7438
	unsigned long group_capacity;
7439
	unsigned long group_util; /* Total utilization of the group */
7440 7441 7442
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7443
	enum group_type group_type;
7444
	int group_no_capacity;
7445 7446 7447 7448
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7449 7450
};

J
Joonsoo Kim 已提交
7451 7452 7453 7454 7455 7456 7457
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *		 during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest;	/* Busiest group in this sd */
	struct sched_group *local;	/* Local group in this sd */
7458
	unsigned long total_running;
J
Joonsoo Kim 已提交
7459
	unsigned long total_load;	/* Total load of all groups in sd */
7460
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7461 7462 7463
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7464
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7465 7466
};

7467 7468 7469 7470 7471 7472 7473 7474 7475 7476 7477
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
	/*
	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
	 * We must however clear busiest_stat::avg_load because
	 * update_sd_pick_busiest() reads this before assignment.
	 */
	*sds = (struct sd_lb_stats){
		.busiest = NULL,
		.local = NULL,
7478
		.total_running = 0UL,
7479
		.total_load = 0UL,
7480
		.total_capacity = 0UL,
7481 7482
		.busiest_stat = {
			.avg_load = 0UL,
7483 7484
			.sum_nr_running = 0,
			.group_type = group_other,
7485 7486 7487 7488
		},
	};
}

7489 7490 7491
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7492
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7493 7494
 *
 * Return: The load index.
7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506 7507 7508 7509 7510 7511 7512 7513 7514 7515 7516
 */
static inline int get_sd_load_idx(struct sched_domain *sd,
					enum cpu_idle_type idle)
{
	int load_idx;

	switch (idle) {
	case CPU_NOT_IDLE:
		load_idx = sd->busy_idx;
		break;

	case CPU_NEWLY_IDLE:
		load_idx = sd->newidle_idx;
		break;
	default:
		load_idx = sd->idle_idx;
		break;
	}

	return load_idx;
}

7517
static unsigned long scale_rt_capacity(int cpu)
7518 7519
{
	struct rq *rq = cpu_rq(cpu);
7520 7521 7522
	unsigned long max = arch_scale_cpu_capacity(NULL, cpu);
	unsigned long used, free;
	unsigned long irq;
7523

7524
	irq = cpu_util_irq(rq);
7525

7526 7527
	if (unlikely(irq >= max))
		return 1;
7528

7529 7530
	used = READ_ONCE(rq->avg_rt.util_avg);
	used += READ_ONCE(rq->avg_dl.util_avg);
7531

7532 7533
	if (unlikely(used >= max))
		return 1;
7534

7535
	free = max - used;
7536 7537

	return scale_irq_capacity(free, irq, max);
7538 7539
}

7540
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7541
{
7542
	unsigned long capacity = scale_rt_capacity(cpu);
7543 7544
	struct sched_group *sdg = sd->groups;

7545
	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);
7546

7547 7548
	if (!capacity)
		capacity = 1;
7549

7550 7551
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7552
	sdg->sgc->min_capacity = capacity;
7553 7554
}

7555
void update_group_capacity(struct sched_domain *sd, int cpu)
7556 7557 7558
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7559
	unsigned long capacity, min_capacity;
7560 7561 7562 7563
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7564
	sdg->sgc->next_update = jiffies + interval;
7565 7566

	if (!child) {
7567
		update_cpu_capacity(sd, cpu);
7568 7569 7570
		return;
	}

7571
	capacity = 0;
7572
	min_capacity = ULONG_MAX;
7573

P
Peter Zijlstra 已提交
7574 7575 7576 7577 7578 7579
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7580
		for_each_cpu(cpu, sched_group_span(sdg)) {
7581
			struct sched_group_capacity *sgc;
7582
			struct rq *rq = cpu_rq(cpu);
7583

7584
			/*
7585
			 * build_sched_domains() -> init_sched_groups_capacity()
7586 7587 7588
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7589 7590
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7591
			 *
7592
			 * This avoids capacity from being 0 and
7593 7594 7595
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7596
				capacity += capacity_of(cpu);
7597 7598 7599
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7600
			}
7601

7602
			min_capacity = min(capacity, min_capacity);
7603
		}
P
Peter Zijlstra 已提交
7604 7605 7606 7607
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7608
		 */
P
Peter Zijlstra 已提交
7609 7610 7611

		group = child->groups;
		do {
7612 7613 7614 7615
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7616 7617 7618
			group = group->next;
		} while (group != child->groups);
	}
7619

7620
	sdg->sgc->capacity = capacity;
7621
	sdg->sgc->min_capacity = min_capacity;
7622 7623
}

7624
/*
7625 7626 7627
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
7628 7629
 */
static inline int
7630
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7631
{
7632 7633
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7634 7635
}

7636 7637
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7638
 * groups is inadequate due to ->cpus_allowed constraints.
7639
 *
7640 7641
 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
7642 7643
 * Something like:
 *
7644 7645
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7646 7647 7648
 *
 * If we were to balance group-wise we'd place two tasks in the first group and
 * two tasks in the second group. Clearly this is undesired as it will overload
7649
 * cpu 3 and leave one of the CPUs in the second group unused.
7650 7651
 *
 * The current solution to this issue is detecting the skew in the first group
7652 7653
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7654 7655
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7656
 * update_sd_pick_busiest(). And calculate_imbalance() and
7657
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7658 7659 7660 7661 7662 7663 7664
 * to create an effective group imbalance.
 *
 * This is a somewhat tricky proposition since the next run might not find the
 * group imbalance and decide the groups need to be balanced again. A most
 * subtle and fragile situation.
 */

7665
static inline int sg_imbalanced(struct sched_group *group)
7666
{
7667
	return group->sgc->imbalance;
7668 7669
}

7670
/*
7671 7672 7673
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
7674 7675
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7676 7677 7678 7679 7680
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
7681
 */
7682 7683
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7684
{
7685 7686
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7687

7688
	if ((sgs->group_capacity * 100) >
7689
			(sgs->group_util * env->sd->imbalance_pct))
7690
		return true;
7691

7692 7693 7694 7695 7696 7697 7698 7699 7700 7701 7702 7703 7704 7705 7706 7707
	return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running <= sgs->group_weight)
		return false;
7708

7709
	if ((sgs->group_capacity * 100) <
7710
			(sgs->group_util * env->sd->imbalance_pct))
7711
		return true;
7712

7713
	return false;
7714 7715
}

7716 7717 7718 7719 7720 7721 7722 7723 7724 7725 7726
/*
 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
 * per-CPU capacity than sched_group ref.
 */
static inline bool
group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
	return sg->sgc->min_capacity * capacity_margin <
						ref->sgc->min_capacity * 1024;
}

7727 7728 7729
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7730
{
7731
	if (sgs->group_no_capacity)
7732 7733 7734 7735 7736 7737 7738 7739
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7740
static bool update_nohz_stats(struct rq *rq, bool force)
7741 7742 7743 7744
{
#ifdef CONFIG_NO_HZ_COMMON
	unsigned int cpu = rq->cpu;

7745 7746 7747
	if (!rq->has_blocked_load)
		return false;

7748
	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
7749
		return false;
7750

7751
	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
7752
		return true;
7753 7754

	update_blocked_averages(cpu);
7755 7756 7757 7758

	return rq->has_blocked_load;
#else
	return false;
7759 7760 7761
#endif
}

7762 7763
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7764
 * @env: The load balancing environment.
7765 7766 7767 7768
 * @group: sched_group whose statistics are to be updated.
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @local_group: Does group contain this_cpu.
 * @sgs: variable to hold the statistics for this group.
7769
 * @overload: Indicate more than one runnable task for any CPU.
7770
 */
7771 7772
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7773 7774
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7775
{
7776
	unsigned long load;
7777
	int i, nr_running;
7778

7779 7780
	memset(sgs, 0, sizeof(*sgs));

7781
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7782 7783
		struct rq *rq = cpu_rq(i);

7784
		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
7785
			env->flags |= LBF_NOHZ_AGAIN;
7786

7787
		/* Bias balancing toward CPUs of our domain: */
7788
		if (local_group)
7789
			load = target_load(i, load_idx);
7790
		else
7791 7792 7793
			load = source_load(i, load_idx);

		sgs->group_load += load;
7794
		sgs->group_util += cpu_util(i);
7795
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7796

7797 7798
		nr_running = rq->nr_running;
		if (nr_running > 1)
7799 7800
			*overload = true;

7801 7802 7803 7804
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7805
		sgs->sum_weighted_load += weighted_cpuload(rq);
7806 7807 7808 7809
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7810
			sgs->idle_cpus++;
7811 7812
	}

7813 7814
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7815
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7816

7817
	if (sgs->sum_nr_running)
7818
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7819

7820
	sgs->group_weight = group->group_weight;
7821

7822
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7823
	sgs->group_type = group_classify(group, sgs);
7824 7825
}

7826 7827
/**
 * update_sd_pick_busiest - return 1 on busiest group
7828
 * @env: The load balancing environment.
7829 7830
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7831
 * @sgs: sched_group statistics
7832 7833 7834
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7835 7836 7837
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7838
 */
7839
static bool update_sd_pick_busiest(struct lb_env *env,
7840 7841
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7842
				   struct sg_lb_stats *sgs)
7843
{
7844
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7845

7846
	if (sgs->group_type > busiest->group_type)
7847 7848
		return true;

7849 7850 7851 7852 7853 7854
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

7855 7856 7857 7858 7859 7860 7861 7862 7863 7864 7865 7866 7867 7868
	if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
		goto asym_packing;

	/*
	 * Candidate sg has no more than one task per CPU and
	 * has higher per-CPU capacity. Migrating tasks to less
	 * capable CPUs may harm throughput. Maximize throughput,
	 * power/energy consequences are not considered.
	 */
	if (sgs->sum_nr_running <= sgs->group_weight &&
	    group_smaller_cpu_capacity(sds->local, sg))
		return false;

asym_packing:
7869 7870
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7871 7872
		return true;

7873
	/* No ASYM_PACKING if target CPU is already busy */
7874 7875
	if (env->idle == CPU_NOT_IDLE)
		return true;
7876
	/*
T
Tim Chen 已提交
7877 7878 7879
	 * ASYM_PACKING needs to move all the work to the highest
	 * prority CPUs in the group, therefore mark all groups
	 * of lower priority than ourself as busy.
7880
	 */
T
Tim Chen 已提交
7881 7882
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7883 7884 7885
		if (!sds->busiest)
			return true;

7886
		/* Prefer to move from lowest priority CPU's work */
T
Tim Chen 已提交
7887 7888
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7889 7890 7891 7892 7893 7894
			return true;
	}

	return false;
}

7895 7896 7897 7898 7899 7900 7901 7902 7903 7904 7905 7906 7907 7908 7909 7910 7911 7912 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922 7923 7924
#ifdef CONFIG_NUMA_BALANCING
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running > sgs->nr_numa_running)
		return regular;
	if (sgs->sum_nr_running > sgs->nr_preferred_running)
		return remote;
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	if (rq->nr_running > rq->nr_numa_running)
		return regular;
	if (rq->nr_running > rq->nr_preferred_running)
		return remote;
	return all;
}
#else
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	return regular;
}
#endif /* CONFIG_NUMA_BALANCING */

7925
/**
7926
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7927
 * @env: The load balancing environment.
7928 7929
 * @sds: variable to hold the statistics for this sched_domain.
 */
7930
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7931
{
7932 7933
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7934
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7935
	struct sg_lb_stats tmp_sgs;
7936
	int load_idx, prefer_sibling = 0;
7937
	bool overload = false;
7938 7939 7940 7941

	if (child && child->flags & SD_PREFER_SIBLING)
		prefer_sibling = 1;

7942
#ifdef CONFIG_NO_HZ_COMMON
7943
	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
7944 7945 7946
		env->flags |= LBF_NOHZ_STATS;
#endif

7947
	load_idx = get_sd_load_idx(env->sd, env->idle);
7948 7949

	do {
J
Joonsoo Kim 已提交
7950
		struct sg_lb_stats *sgs = &tmp_sgs;
7951 7952
		int local_group;

7953
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7954 7955
		if (local_group) {
			sds->local = sg;
7956
			sgs = local;
7957 7958

			if (env->idle != CPU_NEWLY_IDLE ||
7959 7960
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7961
		}
7962

7963 7964
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7965

7966 7967 7968
		if (local_group)
			goto next_group;

7969 7970
		/*
		 * In case the child domain prefers tasks go to siblings
7971
		 * first, lower the sg capacity so that we'll try
7972 7973
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7974 7975 7976 7977
		 * these excess tasks. The extra check prevents the case where
		 * you always pull from the heaviest group when it is already
		 * under-utilized (possible with a large weight task outweighs
		 * the tasks on the system).
7978
		 */
7979
		if (prefer_sibling && sds->local &&
7980 7981
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7982
			sgs->group_no_capacity = 1;
7983
			sgs->group_type = group_classify(sg, sgs);
7984
		}
7985

7986
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7987
			sds->busiest = sg;
J
Joonsoo Kim 已提交
7988
			sds->busiest_stat = *sgs;
7989 7990
		}

7991 7992
next_group:
		/* Now, start updating sd_lb_stats */
7993
		sds->total_running += sgs->sum_nr_running;
7994
		sds->total_load += sgs->group_load;
7995
		sds->total_capacity += sgs->group_capacity;
7996

7997
		sg = sg->next;
7998
	} while (sg != env->sd->groups);
7999

8000 8001 8002 8003 8004 8005 8006 8007 8008
#ifdef CONFIG_NO_HZ_COMMON
	if ((env->flags & LBF_NOHZ_AGAIN) &&
	    cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {

		WRITE_ONCE(nohz.next_blocked,
			   jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
	}
#endif

8009 8010
	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8011 8012 8013 8014 8015 8016

	if (!env->sd->parent) {
		/* update overload indicator if we are at root domain */
		if (env->dst_rq->rd->overload != overload)
			env->dst_rq->rd->overload = overload;
	}
8017 8018 8019 8020
}

/**
 * check_asym_packing - Check to see if the group is packed into the
8021
 *			sched domain.
8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035
 *
 * This is primarily intended to used at the sibling level.  Some
 * cores like POWER7 prefer to use lower numbered SMT threads.  In the
 * case of POWER7, it can move to lower SMT modes only when higher
 * threads are idle.  When in lower SMT modes, the threads will
 * perform better since they share less core resources.  Hence when we
 * have idle threads, we want them to be the higher ones.
 *
 * This packing function is run on idle threads.  It checks to see if
 * the busiest CPU in this domain (core in the P7 case) has a higher
 * CPU number than the packing function is being run on.  Here we are
 * assuming lower CPU number will be equivalent to lower a SMT thread
 * number.
 *
8036
 * Return: 1 when packing is required and a task should be moved to
8037
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
8038
 *
8039
 * @env: The load balancing environment.
8040 8041
 * @sds: Statistics of the sched_domain which is to be packed
 */
8042
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8043 8044 8045
{
	int busiest_cpu;

8046
	if (!(env->sd->flags & SD_ASYM_PACKING))
8047 8048
		return 0;

8049 8050 8051
	if (env->idle == CPU_NOT_IDLE)
		return 0;

8052 8053 8054
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
8055 8056
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8057 8058
		return 0;

8059
	env->imbalance = DIV_ROUND_CLOSEST(
8060
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8061
		SCHED_CAPACITY_SCALE);
8062

8063
	return 1;
8064 8065 8066 8067 8068 8069
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8070
 * @env: The load balancing environment.
8071 8072
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8073 8074
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8075
{
8076
	unsigned long tmp, capa_now = 0, capa_move = 0;
8077
	unsigned int imbn = 2;
8078
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8079
	struct sg_lb_stats *local, *busiest;
8080

J
Joonsoo Kim 已提交
8081 8082
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8083

J
Joonsoo Kim 已提交
8084 8085 8086 8087
	if (!local->sum_nr_running)
		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
	else if (busiest->load_per_task > local->load_per_task)
		imbn = 1;
8088

J
Joonsoo Kim 已提交
8089
	scaled_busy_load_per_task =
8090
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8091
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8092

8093 8094
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8095
		env->imbalance = busiest->load_per_task;
8096 8097 8098 8099 8100
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8101
	 * however we may be able to increase total CPU capacity used by
8102 8103 8104
	 * moving them.
	 */

8105
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8106
			min(busiest->load_per_task, busiest->avg_load);
8107
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8108
			min(local->load_per_task, local->avg_load);
8109
	capa_now /= SCHED_CAPACITY_SCALE;
8110 8111

	/* Amount of load we'd subtract */
8112
	if (busiest->avg_load > scaled_busy_load_per_task) {
8113
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8114
			    min(busiest->load_per_task,
8115
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8116
	}
8117 8118

	/* Amount of load we'd add */
8119
	if (busiest->avg_load * busiest->group_capacity <
8120
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8121 8122
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8123
	} else {
8124
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8125
		      local->group_capacity;
J
Joonsoo Kim 已提交
8126
	}
8127
	capa_move += local->group_capacity *
8128
		    min(local->load_per_task, local->avg_load + tmp);
8129
	capa_move /= SCHED_CAPACITY_SCALE;
8130 8131

	/* Move if we gain throughput */
8132
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8133
		env->imbalance = busiest->load_per_task;
8134 8135 8136 8137 8138
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8139
 * @env: load balance environment
8140 8141
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8142
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8143
{
8144
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8145 8146 8147 8148
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8149

8150
	if (busiest->group_type == group_imbalanced) {
8151 8152
		/*
		 * In the group_imb case we cannot rely on group-wide averages
8153
		 * to ensure CPU-load equilibrium, look at wider averages. XXX
8154
		 */
J
Joonsoo Kim 已提交
8155 8156
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8157 8158
	}

8159
	/*
8160 8161 8162 8163
	 * Avg load of busiest sg can be less and avg load of local sg can
	 * be greater than avg load across all sgs of sd because avg load
	 * factors in sg capacity and sgs with smaller group_type are
	 * skipped when updating the busiest sg:
8164
	 */
8165 8166
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8167 8168
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8169 8170
	}

8171
	/*
8172
	 * If there aren't any idle CPUs, avoid creating some.
8173 8174 8175
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8176
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8177
		if (load_above_capacity > busiest->group_capacity) {
8178
			load_above_capacity -= busiest->group_capacity;
8179
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8180 8181
			load_above_capacity /= busiest->group_capacity;
		} else
8182
			load_above_capacity = ~0UL;
8183 8184 8185
	}

	/*
8186
	 * We're trying to get all the CPUs to the average_load, so we don't
8187
	 * want to push ourselves above the average load, nor do we wish to
8188
	 * reduce the max loaded CPU below the average load. At the same time,
8189 8190
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8191
	 */
8192
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8193 8194

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8195
	env->imbalance = min(
8196 8197
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8198
	) / SCHED_CAPACITY_SCALE;
8199 8200 8201

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8202
	 * there is no guarantee that any tasks will be moved so we'll have
8203 8204 8205
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8206
	if (env->imbalance < busiest->load_per_task)
8207
		return fix_small_imbalance(env, sds);
8208
}
8209

8210 8211 8212 8213
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8214
 * if there is an imbalance.
8215 8216 8217 8218
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8219
 * @env: The load balancing environment.
8220
 *
8221
 * Return:	- The busiest group if imbalance exists.
8222
 */
J
Joonsoo Kim 已提交
8223
static struct sched_group *find_busiest_group(struct lb_env *env)
8224
{
J
Joonsoo Kim 已提交
8225
	struct sg_lb_stats *local, *busiest;
8226 8227
	struct sd_lb_stats sds;

8228
	init_sd_lb_stats(&sds);
8229 8230 8231 8232 8233

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8234
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8235 8236
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8237

8238
	/* ASYM feature bypasses nice load balance check */
8239
	if (check_asym_packing(env, &sds))
8240 8241
		return sds.busiest;

8242
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8243
	if (!sds.busiest || busiest->sum_nr_running == 0)
8244 8245
		goto out_balanced;

8246
	/* XXX broken for overlapping NUMA groups */
8247 8248
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8249

P
Peter Zijlstra 已提交
8250 8251
	/*
	 * If the busiest group is imbalanced the below checks don't
8252
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8253 8254
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8255
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8256 8257
		goto force_balance;

8258 8259 8260 8261 8262
	/*
	 * When dst_cpu is idle, prevent SMP nice and/or asymmetric group
	 * capacities from resulting in underutilization due to avg_load.
	 */
	if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) &&
8263
	    busiest->group_no_capacity)
8264 8265
		goto force_balance;

8266
	/*
8267
	 * If the local group is busier than the selected busiest group
8268 8269
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8270
	if (local->avg_load >= busiest->avg_load)
8271 8272
		goto out_balanced;

8273 8274 8275 8276
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8277
	if (local->avg_load >= sds.avg_load)
8278 8279
		goto out_balanced;

8280
	if (env->idle == CPU_IDLE) {
8281
		/*
8282
		 * This CPU is idle. If the busiest group is not overloaded
8283
		 * and there is no imbalance between this and busiest group
8284
		 * wrt idle CPUs, it is balanced. The imbalance becomes
8285 8286
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8287
		 */
8288 8289
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8290
			goto out_balanced;
8291 8292 8293 8294 8295
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8296 8297
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8298
			goto out_balanced;
8299
	}
8300

8301
force_balance:
8302
	/* Looks like there is an imbalance. Compute it */
8303
	calculate_imbalance(env, &sds);
8304 8305 8306
	return sds.busiest;

out_balanced:
8307
	env->imbalance = 0;
8308 8309 8310 8311
	return NULL;
}

/*
8312
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8313
 */
8314
static struct rq *find_busiest_queue(struct lb_env *env,
8315
				     struct sched_group *group)
8316 8317
{
	struct rq *busiest = NULL, *rq;
8318
	unsigned long busiest_load = 0, busiest_capacity = 1;
8319 8320
	int i;

8321
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8322
		unsigned long capacity, wl;
8323 8324 8325 8326
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8327

8328 8329 8330 8331 8332 8333 8334 8335 8336 8337 8338 8339 8340 8341 8342 8343 8344 8345 8346 8347 8348 8349
		/*
		 * We classify groups/runqueues into three groups:
		 *  - regular: there are !numa tasks
		 *  - remote:  there are numa tasks that run on the 'wrong' node
		 *  - all:     there is no distinction
		 *
		 * In order to avoid migrating ideally placed numa tasks,
		 * ignore those when there's better options.
		 *
		 * If we ignore the actual busiest queue to migrate another
		 * task, the next balance pass can still reduce the busiest
		 * queue by moving tasks around inside the node.
		 *
		 * If we cannot move enough load due to this classification
		 * the next pass will adjust the group classification and
		 * allow migration of more tasks.
		 *
		 * Both cases only affect the total convergence complexity.
		 */
		if (rt > env->fbq_type)
			continue;

8350
		capacity = capacity_of(i);
8351

8352
		wl = weighted_cpuload(rq);
8353

8354 8355
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8356
		 * which is not scaled with the CPU capacity.
8357
		 */
8358 8359 8360

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8361 8362
			continue;

8363
		/*
8364 8365 8366
		 * For the load comparisons with the other CPU's, consider
		 * the weighted_cpuload() scaled with the CPU capacity, so
		 * that the load can be moved away from the CPU that is
8367
		 * potentially running at a lower capacity.
8368
		 *
8369
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8370
		 * multiplication to rid ourselves of the division works out
8371 8372
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8373
		 */
8374
		if (wl * busiest_capacity > busiest_load * capacity) {
8375
			busiest_load = wl;
8376
			busiest_capacity = capacity;
8377 8378 8379 8380 8381 8382 8383 8384 8385 8386 8387 8388 8389
			busiest = rq;
		}
	}

	return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL	512

8390
static int need_active_balance(struct lb_env *env)
8391
{
8392 8393 8394
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8395 8396 8397

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8398 8399
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8400
		 */
T
Tim Chen 已提交
8401 8402
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8403
			return 1;
8404 8405
	}

8406 8407 8408 8409 8410 8411 8412 8413 8414 8415 8416 8417 8418
	/*
	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
	 * It's worth migrating the task if the src_cpu's capacity is reduced
	 * because of other sched_class or IRQs if more capacity stays
	 * available on dst_cpu.
	 */
	if ((env->idle != CPU_NOT_IDLE) &&
	    (env->src_rq->cfs.h_nr_running == 1)) {
		if ((check_cpu_capacity(env->src_rq, sd)) &&
		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
			return 1;
	}

8419 8420 8421
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8422 8423
static int active_load_balance_cpu_stop(void *data);

8424 8425 8426 8427 8428
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8429 8430 8431 8432 8433 8434 8435
	/*
	 * Ensure the balancing environment is consistent; can happen
	 * when the softirq triggers 'during' hotplug.
	 */
	if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
		return 0;

8436
	/*
8437
	 * In the newly idle case, we will allow all the CPUs
8438 8439 8440 8441 8442
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

8443
	/* Try to find first idle CPU */
8444
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8445
		if (!idle_cpu(cpu))
8446 8447 8448 8449 8450 8451 8452 8453 8454 8455
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
8456
	 * First idle CPU or the first CPU(busiest) in this sched group
8457 8458
	 * is eligible for doing load balancing at this and above domains.
	 */
8459
	return balance_cpu == env->dst_cpu;
8460 8461
}

8462 8463 8464 8465 8466 8467
/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
			struct sched_domain *sd, enum cpu_idle_type idle,
8468
			int *continue_balancing)
8469
{
8470
	int ld_moved, cur_ld_moved, active_balance = 0;
8471
	struct sched_domain *sd_parent = sd->parent;
8472 8473
	struct sched_group *group;
	struct rq *busiest;
8474
	struct rq_flags rf;
8475
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8476

8477 8478
	struct lb_env env = {
		.sd		= sd,
8479 8480
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8481
		.dst_grpmask    = sched_group_span(sd->groups),
8482
		.idle		= idle,
8483
		.loop_break	= sched_nr_migrate_break,
8484
		.cpus		= cpus,
8485
		.fbq_type	= all,
8486
		.tasks		= LIST_HEAD_INIT(env.tasks),
8487 8488
	};

8489
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8490

8491
	schedstat_inc(sd->lb_count[idle]);
8492 8493

redo:
8494 8495
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8496
		goto out_balanced;
8497
	}
8498

8499
	group = find_busiest_group(&env);
8500
	if (!group) {
8501
		schedstat_inc(sd->lb_nobusyg[idle]);
8502 8503 8504
		goto out_balanced;
	}

8505
	busiest = find_busiest_queue(&env, group);
8506
	if (!busiest) {
8507
		schedstat_inc(sd->lb_nobusyq[idle]);
8508 8509 8510
		goto out_balanced;
	}

8511
	BUG_ON(busiest == env.dst_rq);
8512

8513
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8514

8515 8516 8517
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8518 8519 8520 8521 8522 8523 8524 8525
	ld_moved = 0;
	if (busiest->nr_running > 1) {
		/*
		 * Attempt to move tasks. If find_busiest_group has found
		 * an imbalance but busiest->nr_running <= 1, the group is
		 * still unbalanced. ld_moved simply stays zero, so it is
		 * correctly treated as an imbalance.
		 */
8526
		env.flags |= LBF_ALL_PINNED;
8527
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8528

8529
more_balance:
8530
		rq_lock_irqsave(busiest, &rf);
8531
		update_rq_clock(busiest);
8532 8533 8534 8535 8536

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8537
		cur_ld_moved = detach_tasks(&env);
8538 8539

		/*
8540 8541 8542 8543 8544
		 * We've detached some tasks from busiest_rq. Every
		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
		 * unlock busiest->lock, and we are able to be sure
		 * that nobody can manipulate the tasks in parallel.
		 * See task_rq_lock() family for the details.
8545
		 */
8546

8547
		rq_unlock(busiest, &rf);
8548 8549 8550 8551 8552 8553

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8554
		local_irq_restore(rf.flags);
8555

8556 8557 8558 8559 8560
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8561 8562 8563 8564
		/*
		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
		 * us and move them to an alternate dst_cpu in our sched_group
		 * where they can run. The upper limit on how many times we
8565
		 * iterate on same src_cpu is dependent on number of CPUs in our
8566 8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579
		 * sched_group.
		 *
		 * This changes load balance semantics a bit on who can move
		 * load to a given_cpu. In addition to the given_cpu itself
		 * (or a ilb_cpu acting on its behalf where given_cpu is
		 * nohz-idle), we now have balance_cpu in a position to move
		 * load to given_cpu. In rare situations, this may cause
		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
		 * _independently_ and at _same_ time to move some load to
		 * given_cpu) causing exceess load to be moved to given_cpu.
		 * This however should not happen so much in practice and
		 * moreover subsequent load balance cycles should correct the
		 * excess load moved.
		 */
8580
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8581

8582
			/* Prevent to re-select dst_cpu via env's CPUs */
8583 8584
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8585
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8586
			env.dst_cpu	 = env.new_dst_cpu;
8587
			env.flags	&= ~LBF_DST_PINNED;
8588 8589
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8590

8591 8592 8593 8594 8595 8596
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8597

8598 8599 8600 8601
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8602
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8603

8604
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8605 8606 8607
				*group_imbalance = 1;
		}

8608
		/* All tasks on this runqueue were pinned by CPU affinity */
8609
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8610
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8611 8612 8613 8614 8615 8616 8617 8618 8619
			/*
			 * Attempting to continue load balancing at the current
			 * sched_domain level only makes sense if there are
			 * active CPUs remaining as possible busiest CPUs to
			 * pull load from which are not contained within the
			 * destination group that is receiving any migrated
			 * load.
			 */
			if (!cpumask_subset(cpus, env.dst_grpmask)) {
8620 8621
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8622
				goto redo;
8623
			}
8624
			goto out_all_pinned;
8625 8626 8627 8628
		}
	}

	if (!ld_moved) {
8629
		schedstat_inc(sd->lb_failed[idle]);
8630 8631 8632 8633 8634 8635 8636 8637
		/*
		 * Increment the failure counter only on periodic balance.
		 * We do not want newidle balance, which can be very
		 * frequent, pollute the failure counter causing
		 * excessive cache_hot migrations and active balances.
		 */
		if (idle != CPU_NEWLY_IDLE)
			sd->nr_balance_failed++;
8638

8639
		if (need_active_balance(&env)) {
8640 8641
			unsigned long flags;

8642 8643
			raw_spin_lock_irqsave(&busiest->lock, flags);

8644 8645 8646 8647
			/*
			 * Don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest CPU can't be
			 * moved to this_cpu:
8648
			 */
8649
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8650 8651
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8652
				env.flags |= LBF_ALL_PINNED;
8653 8654 8655
				goto out_one_pinned;
			}

8656 8657 8658 8659 8660
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8661 8662 8663 8664 8665 8666
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8667

8668
			if (active_balance) {
8669 8670 8671
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8672
			}
8673

8674
			/* We've kicked active balancing, force task migration. */
8675 8676 8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687
			sd->nr_balance_failed = sd->cache_nice_tries+1;
		}
	} else
		sd->nr_balance_failed = 0;

	if (likely(!active_balance)) {
		/* We were unbalanced, so reset the balancing interval */
		sd->balance_interval = sd->min_interval;
	} else {
		/*
		 * If we've begun active balancing, start to back off. This
		 * case may not be covered by the all_pinned logic if there
		 * is only 1 task on the busy runqueue (because we don't call
8688
		 * detach_tasks).
8689 8690 8691 8692 8693 8694 8695 8696
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8697 8698 8699 8700 8701 8702 8703 8704 8705 8706 8707 8708 8709 8710 8711 8712 8713
	/*
	 * We reach balance although we may have faced some affinity
	 * constraints. Clear the imbalance flag if it was set.
	 */
	if (sd_parent) {
		int *group_imbalance = &sd_parent->groups->sgc->imbalance;

		if (*group_imbalance)
			*group_imbalance = 0;
	}

out_all_pinned:
	/*
	 * We reach balance because all tasks are pinned at this level so
	 * we can't migrate them. Let the imbalance flag set so parent level
	 * can try to migrate them.
	 */
8714
	schedstat_inc(sd->lb_balanced[idle]);
8715 8716 8717 8718 8719

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8720
	if (((env.flags & LBF_ALL_PINNED) &&
8721
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8722 8723 8724
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8725
	ld_moved = 0;
8726 8727 8728 8729
out:
	return ld_moved;
}

8730 8731 8732 8733 8734 8735 8736 8737 8738 8739 8740 8741 8742 8743 8744 8745
static inline unsigned long
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
	unsigned long interval = sd->balance_interval;

	if (cpu_busy)
		interval *= sd->busy_factor;

	/* scale ms to jiffies */
	interval = msecs_to_jiffies(interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);

	return interval;
}

static inline void
8746
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8747 8748 8749
{
	unsigned long interval, next;

8750 8751
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8752 8753 8754 8755 8756 8757
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8758
/*
8759
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
8760 8761 8762
 * running tasks off the busiest CPU onto idle CPUs. It requires at
 * least 1 task to be running on each physical CPU where possible, and
 * avoids physical / logical imbalances.
8763
 */
8764
static int active_load_balance_cpu_stop(void *data)
8765
{
8766 8767
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8768
	int target_cpu = busiest_rq->push_cpu;
8769
	struct rq *target_rq = cpu_rq(target_cpu);
8770
	struct sched_domain *sd;
8771
	struct task_struct *p = NULL;
8772
	struct rq_flags rf;
8773

8774
	rq_lock_irq(busiest_rq, &rf);
8775 8776 8777 8778 8779 8780 8781
	/*
	 * Between queueing the stop-work and running it is a hole in which
	 * CPUs can become inactive. We should not move tasks from or to
	 * inactive CPUs.
	 */
	if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
		goto out_unlock;
8782

8783
	/* Make sure the requested CPU hasn't gone down in the meantime: */
8784 8785 8786
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
8787 8788 8789

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8790
		goto out_unlock;
8791 8792 8793 8794

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
8795
	 * Bjorn Helgaas on a 128-CPU setup.
8796 8797 8798 8799
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
8800
	rcu_read_lock();
8801 8802 8803 8804 8805 8806 8807
	for_each_domain(target_cpu, sd) {
		if ((sd->flags & SD_LOAD_BALANCE) &&
		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
				break;
	}

	if (likely(sd)) {
8808 8809
		struct lb_env env = {
			.sd		= sd,
8810 8811 8812 8813
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8814
			.idle		= CPU_IDLE,
8815 8816 8817 8818 8819 8820 8821
			/*
			 * can_migrate_task() doesn't need to compute new_dst_cpu
			 * for active balancing. Since we have CPU_IDLE, but no
			 * @dst_grpmask we need to make that test go away with lying
			 * about DST_PINNED.
			 */
			.flags		= LBF_DST_PINNED,
8822 8823
		};

8824
		schedstat_inc(sd->alb_count);
8825
		update_rq_clock(busiest_rq);
8826

8827
		p = detach_one_task(&env);
8828
		if (p) {
8829
			schedstat_inc(sd->alb_pushed);
8830 8831 8832
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8833
			schedstat_inc(sd->alb_failed);
8834
		}
8835
	}
8836
	rcu_read_unlock();
8837 8838
out_unlock:
	busiest_rq->active_balance = 0;
8839
	rq_unlock(busiest_rq, &rf);
8840 8841 8842 8843 8844 8845

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8846
	return 0;
8847 8848
}

8849 8850 8851 8852 8853 8854 8855 8856 8857 8858 8859 8860 8861 8862 8863 8864 8865 8866 8867 8868 8869 8870 8871 8872 8873 8874 8875 8876 8877 8878 8879 8880 8881 8882 8883 8884 8885 8886 8887 8888 8889 8890 8891 8892 8893 8894 8895 8896 8897 8898 8899 8900 8901 8902 8903 8904 8905 8906 8907 8908 8909 8910 8911 8912 8913 8914 8915 8916 8917 8918 8919 8920 8921 8922 8923 8924 8925 8926 8927 8928 8929 8930 8931 8932 8933 8934 8935 8936 8937 8938 8939 8940 8941 8942 8943 8944 8945 8946 8947 8948 8949 8950 8951 8952 8953 8954 8955 8956 8957 8958 8959 8960 8961 8962 8963 8964 8965 8966
static DEFINE_SPINLOCK(balancing);

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
void update_max_interval(void)
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in init_sched_domains.
 */
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
{
	int continue_balancing = 1;
	int cpu = rq->cpu;
	unsigned long interval;
	struct sched_domain *sd;
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;

	rcu_read_lock();
	for_each_domain(cpu, sd) {
		/*
		 * Decay the newidle max times here because this is a regular
		 * visit to all the domains. Decay ~1% per second.
		 */
		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
			sd->max_newidle_lb_cost =
				(sd->max_newidle_lb_cost * 253) / 256;
			sd->next_decay_max_lb_cost = jiffies + HZ;
			need_decay = 1;
		}
		max_cost += sd->max_newidle_lb_cost;

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!continue_balancing) {
			if (need_decay)
				continue;
			break;
		}

		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
				/*
				 * The LBF_DST_PINNED logic could have changed
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
				 */
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
		}
		if (need_serialize)
			spin_unlock(&balancing);
out:
		if (time_after(next_balance, sd->last_balance + interval)) {
			next_balance = sd->last_balance + interval;
			update_next_balance = 1;
		}
	}
	if (need_decay) {
		/*
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
		 */
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
	}
	rcu_read_unlock();

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance)) {
		rq->next_balance = next_balance;

#ifdef CONFIG_NO_HZ_COMMON
		/*
		 * If this CPU has been elected to perform the nohz idle
		 * balance. Other idle CPUs have already rebalanced with
		 * nohz_idle_balance() and nohz.next_balance has been
		 * updated accordingly. This CPU is now running the idle load
		 * balance for itself and we need to update the
		 * nohz.next_balance accordingly.
		 */
		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
			nohz.next_balance = rq->next_balance;
#endif
	}
}

8967 8968 8969 8970 8971
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8972
#ifdef CONFIG_NO_HZ_COMMON
8973 8974 8975 8976 8977 8978
/*
 * idle load balancing details
 * - When one of the busy CPUs notice that there may be an idle rebalancing
 *   needed, they will kick the idle load balancer, which then does idle
 *   load balancing for all the idle CPUs.
 */
8979

8980
static inline int find_new_ilb(void)
8981
{
8982
	int ilb = cpumask_first(nohz.idle_cpus_mask);
8983

8984 8985 8986 8987
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
8988 8989
}

8990 8991 8992 8993 8994
/*
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
 * CPU (if there is one).
 */
8995
static void kick_ilb(unsigned int flags)
8996 8997 8998 8999 9000
{
	int ilb_cpu;

	nohz.next_balance++;

9001
	ilb_cpu = find_new_ilb();
9002

9003 9004
	if (ilb_cpu >= nr_cpu_ids)
		return;
9005

9006
	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
P
Peter Zijlstra 已提交
9007
	if (flags & NOHZ_KICK_MASK)
9008
		return;
9009

9010 9011
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
9012
	 * This way we generate a sched IPI on the target CPU which
9013 9014 9015 9016
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
9017 9018 9019 9020 9021 9022 9023 9024 9025 9026 9027 9028 9029 9030 9031 9032 9033 9034 9035
}

/*
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu in the system.
 *   - This rq has more than one task.
 *   - This rq has at least one CFS task and the capacity of the CPU is
 *     significantly reduced because of RT tasks or IRQs.
 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
 *     multiple busy cpu.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
 */
static void nohz_balancer_kick(struct rq *rq)
{
	unsigned long now = jiffies;
	struct sched_domain_shared *sds;
	struct sched_domain *sd;
	int nr_busy, i, cpu = rq->cpu;
9036
	unsigned int flags = 0;
9037 9038 9039 9040 9041 9042 9043 9044

	if (unlikely(rq->idle_balance))
		return;

	/*
	 * We may be recently in ticked or tickless idle mode. At the first
	 * busy tick after returning from idle, we will update the busy stats.
	 */
9045
	nohz_balance_exit_idle(rq);
9046 9047 9048 9049 9050 9051 9052 9053

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return;

9054 9055
	if (READ_ONCE(nohz.has_blocked) &&
	    time_after(now, READ_ONCE(nohz.next_blocked)))
9056 9057
		flags = NOHZ_STATS_KICK;

9058
	if (time_before(now, nohz.next_balance))
9059
		goto out;
9060 9061

	if (rq->nr_running >= 2) {
9062
		flags = NOHZ_KICK_MASK;
9063 9064 9065 9066 9067 9068 9069 9070 9071 9072 9073 9074
		goto out;
	}

	rcu_read_lock();
	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds) {
		/*
		 * XXX: write a coherent comment on why we do this.
		 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
		 */
		nr_busy = atomic_read(&sds->nr_busy_cpus);
		if (nr_busy > 1) {
9075
			flags = NOHZ_KICK_MASK;
9076 9077 9078 9079 9080 9081 9082 9083 9084
			goto unlock;
		}

	}

	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
9085
			flags = NOHZ_KICK_MASK;
9086 9087 9088 9089 9090 9091 9092 9093 9094 9095 9096 9097
			goto unlock;
		}
	}

	sd = rcu_dereference(per_cpu(sd_asym, cpu));
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;

			if (sched_asym_prefer(i, cpu)) {
9098
				flags = NOHZ_KICK_MASK;
9099 9100 9101 9102 9103 9104 9105
				goto unlock;
			}
		}
	}
unlock:
	rcu_read_unlock();
out:
9106 9107
	if (flags)
		kick_ilb(flags);
9108 9109
}

9110
static void set_cpu_sd_state_busy(int cpu)
9111
{
9112
	struct sched_domain *sd;
9113

9114 9115
	rcu_read_lock();
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
9116

9117 9118 9119 9120 9121 9122 9123
	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
	rcu_read_unlock();
9124 9125
}

9126 9127 9128 9129 9130 9131 9132 9133 9134 9135 9136 9137 9138 9139 9140
void nohz_balance_exit_idle(struct rq *rq)
{
	SCHED_WARN_ON(rq != this_rq());

	if (likely(!rq->nohz_tick_stopped))
		return;

	rq->nohz_tick_stopped = 0;
	cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
	atomic_dec(&nohz.nr_cpus);

	set_cpu_sd_state_busy(rq->cpu);
}

static void set_cpu_sd_state_idle(int cpu)
9141 9142 9143 9144
{
	struct sched_domain *sd;

	rcu_read_lock();
9145
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9146 9147 9148 9149 9150

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

9151
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9152
unlock:
9153 9154 9155
	rcu_read_unlock();
}

9156
/*
9157
 * This routine will record that the CPU is going idle with tick stopped.
9158
 * This info will be used in performing idle load balancing in the future.
9159
 */
9160
void nohz_balance_enter_idle(int cpu)
9161
{
9162 9163 9164 9165
	struct rq *rq = cpu_rq(cpu);

	SCHED_WARN_ON(cpu != smp_processor_id());

9166
	/* If this CPU is going down, then nothing needs to be done: */
9167 9168 9169
	if (!cpu_active(cpu))
		return;

9170
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
9171
	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9172 9173
		return;

9174 9175 9176 9177 9178 9179 9180 9181 9182 9183 9184 9185 9186
	/*
	 * Can be set safely without rq->lock held
	 * If a clear happens, it will have evaluated last additions because
	 * rq->lock is held during the check and the clear
	 */
	rq->has_blocked_load = 1;

	/*
	 * The tick is still stopped but load could have been added in the
	 * meantime. We set the nohz.has_blocked flag to trig a check of the
	 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
	 * of nohz.has_blocked can only happen after checking the new load
	 */
9187
	if (rq->nohz_tick_stopped)
9188
		goto out;
9189

9190
	/* If we're a completely isolated CPU, we don't play: */
9191
	if (on_null_domain(rq))
9192 9193
		return;

9194 9195
	rq->nohz_tick_stopped = 1;

9196 9197
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
9198

9199 9200 9201 9202 9203 9204 9205
	/*
	 * Ensures that if nohz_idle_balance() fails to observe our
	 * @idle_cpus_mask store, it must observe the @has_blocked
	 * store.
	 */
	smp_mb__after_atomic();

9206
	set_cpu_sd_state_idle(cpu);
9207 9208 9209 9210 9211 9212 9213

out:
	/*
	 * Each time a cpu enter idle, we assume that it has blocked load and
	 * enable the periodic update of the load of idle cpus
	 */
	WRITE_ONCE(nohz.has_blocked, 1);
9214 9215 9216
}

/*
9217 9218 9219 9220 9221
 * Internal function that runs load balance for all idle cpus. The load balance
 * can be a simple update of blocked load or a complete load balance with
 * tasks movement depending of flags.
 * The function returns false if the loop has stopped before running
 * through all idle CPUs.
9222
 */
9223 9224
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
			       enum cpu_idle_type idle)
9225
{
9226
	/* Earliest time when we have to do rebalance again */
9227 9228
	unsigned long now = jiffies;
	unsigned long next_balance = now + 60*HZ;
9229
	bool has_blocked_load = false;
9230
	int update_next_balance = 0;
P
Peter Zijlstra 已提交
9231 9232
	int this_cpu = this_rq->cpu;
	int balance_cpu;
9233
	int ret = false;
P
Peter Zijlstra 已提交
9234
	struct rq *rq;
9235

P
Peter Zijlstra 已提交
9236
	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9237

9238 9239 9240 9241 9242 9243 9244 9245 9246 9247 9248 9249 9250 9251 9252 9253
	/*
	 * We assume there will be no idle load after this update and clear
	 * the has_blocked flag. If a cpu enters idle in the mean time, it will
	 * set the has_blocked flag and trig another update of idle load.
	 * Because a cpu that becomes idle, is added to idle_cpus_mask before
	 * setting the flag, we are sure to not clear the state and not
	 * check the load of an idle cpu.
	 */
	WRITE_ONCE(nohz.has_blocked, 0);

	/*
	 * Ensures that if we miss the CPU, we must see the has_blocked
	 * store from nohz_balance_enter_idle().
	 */
	smp_mb();

9254
	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9255
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9256 9257 9258
			continue;

		/*
9259 9260
		 * If this CPU gets work to do, stop the load balancing
		 * work being done for other CPUs. Next load
9261 9262
		 * balancing owner will pick it up.
		 */
9263 9264 9265 9266
		if (need_resched()) {
			has_blocked_load = true;
			goto abort;
		}
9267

V
Vincent Guittot 已提交
9268 9269
		rq = cpu_rq(balance_cpu);

9270
		has_blocked_load |= update_nohz_stats(rq, true);
9271

9272 9273 9274 9275 9276
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9277 9278
			struct rq_flags rf;

9279
			rq_lock_irqsave(rq, &rf);
9280
			update_rq_clock(rq);
9281
			cpu_load_update_idle(rq);
9282
			rq_unlock_irqrestore(rq, &rf);
9283

P
Peter Zijlstra 已提交
9284 9285
			if (flags & NOHZ_BALANCE_KICK)
				rebalance_domains(rq, CPU_IDLE);
9286
		}
9287

9288 9289 9290 9291
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9292
	}
9293

9294 9295 9296 9297 9298 9299
	/* Newly idle CPU doesn't need an update */
	if (idle != CPU_NEWLY_IDLE) {
		update_blocked_averages(this_cpu);
		has_blocked_load |= this_rq->has_blocked_load;
	}

P
Peter Zijlstra 已提交
9300 9301 9302
	if (flags & NOHZ_BALANCE_KICK)
		rebalance_domains(this_rq, CPU_IDLE);

9303 9304 9305
	WRITE_ONCE(nohz.next_blocked,
		now + msecs_to_jiffies(LOAD_AVG_PERIOD));

9306 9307 9308
	/* The full idle balance loop has been done */
	ret = true;

9309 9310 9311 9312
abort:
	/* There is still blocked load, enable periodic update */
	if (has_blocked_load)
		WRITE_ONCE(nohz.has_blocked, 1);
9313

9314 9315 9316 9317 9318 9319 9320
	/*
	 * next_balance will be updated only when there is a need.
	 * When the CPU is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		nohz.next_balance = next_balance;
P
Peter Zijlstra 已提交
9321

9322 9323 9324 9325 9326 9327 9328 9329 9330 9331 9332 9333 9334 9335 9336 9337 9338 9339 9340 9341 9342 9343 9344 9345 9346 9347 9348 9349 9350
	return ret;
}

/*
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
	int this_cpu = this_rq->cpu;
	unsigned int flags;

	if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
		return false;

	if (idle != CPU_IDLE) {
		atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
		return false;
	}

	/*
	 * barrier, pairs with nohz_balance_enter_idle(), ensures ...
	 */
	flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
	if (!(flags & NOHZ_KICK_MASK))
		return false;

	_nohz_idle_balance(this_rq, flags, idle);

P
Peter Zijlstra 已提交
9351
	return true;
9352
}
9353 9354 9355 9356 9357 9358 9359 9360 9361 9362 9363 9364 9365 9366 9367 9368 9369 9370 9371 9372 9373 9374 9375 9376 9377 9378 9379 9380 9381 9382 9383 9384 9385

static void nohz_newidle_balance(struct rq *this_rq)
{
	int this_cpu = this_rq->cpu;

	/*
	 * This CPU doesn't want to be disturbed by scheduler
	 * housekeeping
	 */
	if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
		return;

	/* Will wake up very soon. No time for doing anything else*/
	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

	/* Don't need to update blocked load of idle CPUs*/
	if (!READ_ONCE(nohz.has_blocked) ||
	    time_before(jiffies, READ_ONCE(nohz.next_blocked)))
		return;

	raw_spin_unlock(&this_rq->lock);
	/*
	 * This CPU is going to be idle and blocked load of idle CPUs
	 * need to be updated. Run the ilb locally as it is a good
	 * candidate for ilb instead of waking up another idle CPU.
	 * Kick an normal ilb if we failed to do the update.
	 */
	if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
		kick_ilb(NOHZ_STATS_KICK);
	raw_spin_lock(&this_rq->lock);
}

9386 9387 9388
#else /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq) { }

9389
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
P
Peter Zijlstra 已提交
9390 9391 9392
{
	return false;
}
9393 9394

static inline void nohz_newidle_balance(struct rq *this_rq) { }
9395
#endif /* CONFIG_NO_HZ_COMMON */
9396

P
Peter Zijlstra 已提交
9397 9398 9399 9400 9401 9402 9403 9404 9405 9406 9407 9408 9409 9410 9411 9412 9413 9414 9415 9416 9417 9418 9419 9420 9421 9422 9423 9424 9425 9426 9427 9428 9429 9430
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
{
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
	struct sched_domain *sd;
	int pulled_task = 0;
	u64 curr_cost = 0;

	/*
	 * We must set idle_stamp _before_ calling idle_balance(), such that we
	 * measure the duration of idle_balance() as idle time.
	 */
	this_rq->idle_stamp = rq_clock(this_rq);

	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

	/*
	 * This is OK, because current is on_cpu, which avoids it being picked
	 * for load-balance and preemption/IRQs are still disabled avoiding
	 * further scheduler activity on it and we're being very careful to
	 * re-start the picking loop.
	 */
	rq_unpin_lock(this_rq, rf);

	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
9431

P
Peter Zijlstra 已提交
9432 9433 9434 9435 9436 9437
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, &next_balance);
		rcu_read_unlock();

9438 9439
		nohz_newidle_balance(this_rq);

P
Peter Zijlstra 已提交
9440 9441 9442 9443 9444 9445 9446 9447 9448 9449 9450 9451 9452 9453 9454 9455 9456 9457 9458 9459 9460 9461 9462 9463 9464 9465 9466 9467 9468 9469 9470 9471 9472 9473 9474 9475 9476 9477 9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488
		goto out;
	}

	raw_spin_unlock(&this_rq->lock);

	update_blocked_averages(this_cpu);
	rcu_read_lock();
	for_each_domain(this_cpu, sd) {
		int continue_balancing = 1;
		u64 t0, domain_cost;

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, &next_balance);
			break;
		}

		if (sd->flags & SD_BALANCE_NEWIDLE) {
			t0 = sched_clock_cpu(this_cpu);

			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);

			domain_cost = sched_clock_cpu(this_cpu) - t0;
			if (domain_cost > sd->max_newidle_lb_cost)
				sd->max_newidle_lb_cost = domain_cost;

			curr_cost += domain_cost;
		}

		update_next_balance(sd, &next_balance);

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
			break;
	}
	rcu_read_unlock();

	raw_spin_lock(&this_rq->lock);

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

9489
out:
P
Peter Zijlstra 已提交
9490 9491 9492 9493 9494 9495 9496 9497 9498 9499 9500 9501 9502 9503 9504 9505 9506 9507 9508 9509 9510 9511 9512 9513
	/*
	 * While browsing the domains, we released the rq lock, a task could
	 * have been enqueued in the meantime. Since we're not going idle,
	 * pretend we pulled a task.
	 */
	if (this_rq->cfs.h_nr_running && !pulled_task)
		pulled_task = 1;

	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
		this_rq->next_balance = next_balance;

	/* Is there a task of a high priority class? */
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
		pulled_task = -1;

	if (pulled_task)
		this_rq->idle_stamp = 0;

	rq_repin_lock(this_rq, rf);

	return pulled_task;
}

9514 9515 9516 9517
/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9518
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9519
{
9520
	struct rq *this_rq = this_rq();
9521
	enum cpu_idle_type idle = this_rq->idle_balance ?
9522 9523 9524
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9525 9526
	 * If this CPU has a pending nohz_balance_kick, then do the
	 * balancing on behalf of the other idle CPUs whose ticks are
9527
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9528
	 * give the idle CPUs a chance to load balance. Else we may
9529 9530
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9531
	 */
P
Peter Zijlstra 已提交
9532 9533 9534 9535 9536
	if (nohz_idle_balance(this_rq, idle))
		return;

	/* normal load balance */
	update_blocked_averages(this_rq->cpu);
9537
	rebalance_domains(this_rq, idle);
9538 9539 9540 9541 9542
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9543
void trigger_load_balance(struct rq *rq)
9544 9545
{
	/* Don't need to rebalance while attached to NULL domain */
9546 9547 9548 9549
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9550
		raise_softirq(SCHED_SOFTIRQ);
9551 9552

	nohz_balancer_kick(rq);
9553 9554
}

9555 9556 9557
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9558 9559

	update_runtime_enabled(rq);
9560 9561 9562 9563 9564
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9565 9566 9567

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9568 9569
}

9570
#endif /* CONFIG_SMP */
9571

9572
/*
9573 9574 9575 9576 9577 9578
 * scheduler tick hitting a task of our scheduling class.
 *
 * NOTE: This function can be called remotely by the tick offload that
 * goes along full dynticks. Therefore no local assumption can be made
 * and everything must be accessed through the @rq and @curr passed in
 * parameters.
9579
 */
P
Peter Zijlstra 已提交
9580
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9581 9582 9583 9584 9585 9586
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &curr->se;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
P
Peter Zijlstra 已提交
9587
		entity_tick(cfs_rq, se, queued);
9588
	}
9589

9590
	if (static_branch_unlikely(&sched_numa_balancing))
9591
		task_tick_numa(rq, curr);
9592 9593 9594
}

/*
P
Peter Zijlstra 已提交
9595 9596 9597
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9598
 */
P
Peter Zijlstra 已提交
9599
static void task_fork_fair(struct task_struct *p)
9600
{
9601 9602
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9603
	struct rq *rq = this_rq();
9604
	struct rq_flags rf;
9605

9606
	rq_lock(rq, &rf);
9607 9608
	update_rq_clock(rq);

9609 9610
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9611 9612
	if (curr) {
		update_curr(cfs_rq);
9613
		se->vruntime = curr->vruntime;
9614
	}
9615
	place_entity(cfs_rq, se, 1);
9616

P
Peter Zijlstra 已提交
9617
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9618
		/*
9619 9620 9621
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9622
		swap(curr->vruntime, se->vruntime);
9623
		resched_curr(rq);
9624
	}
9625

9626
	se->vruntime -= cfs_rq->min_vruntime;
9627
	rq_unlock(rq, &rf);
9628 9629
}

9630 9631 9632 9633
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9634 9635
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9636
{
9637
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9638 9639
		return;

9640 9641 9642 9643 9644
	/*
	 * Reschedule if we are currently running on this runqueue and
	 * our priority decreased, or if we are not currently running on
	 * this runqueue and our priority is higher than the current's
	 */
P
Peter Zijlstra 已提交
9645
	if (rq->curr == p) {
9646
		if (p->prio > oldprio)
9647
			resched_curr(rq);
9648
	} else
9649
		check_preempt_curr(rq, p, 0);
9650 9651
}

9652
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9653 9654 9655 9656
{
	struct sched_entity *se = &p->se;

	/*
9657 9658 9659 9660 9661 9662 9663 9664 9665 9666
	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
	 * the dequeue_entity(.flags=0) will already have normalized the
	 * vruntime.
	 */
	if (p->on_rq)
		return true;

	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
P
Peter Zijlstra 已提交
9667
	 *
9668 9669 9670 9671
	 * - A forked child which is waiting for being woken up by
	 *   wake_up_new_task().
	 * - A task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
P
Peter Zijlstra 已提交
9672
	 */
9673 9674 9675 9676 9677 9678
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9679 9680 9681 9682 9683 9684 9685 9686 9687 9688 9689 9690 9691 9692 9693 9694 9695 9696
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * Propagate the changes of the sched_entity across the tg tree to make it
 * visible to the root
 */
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq;

	/* Start to propagate at parent */
	se = se->parent;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);

		if (cfs_rq_throttled(cfs_rq))
			break;

9697
		update_load_avg(cfs_rq, se, UPDATE_TG);
9698 9699 9700 9701 9702 9703
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9704
static void detach_entity_cfs_rq(struct sched_entity *se)
9705 9706 9707
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9708
	/* Catch up with the cfs_rq and remove our load when we leave */
9709
	update_load_avg(cfs_rq, se, 0);
9710
	detach_entity_load_avg(cfs_rq, se);
9711
	update_tg_load_avg(cfs_rq, false);
9712
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9713 9714
}

9715
static void attach_entity_cfs_rq(struct sched_entity *se)
9716
{
9717
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9718 9719

#ifdef CONFIG_FAIR_GROUP_SCHED
9720 9721 9722 9723 9724 9725
	/*
	 * Since the real-depth could have been changed (only FAIR
	 * class maintain depth value), reset depth properly.
	 */
	se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
9726

9727
	/* Synchronize entity with its cfs_rq */
9728
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9729
	attach_entity_load_avg(cfs_rq, se, 0);
9730
	update_tg_load_avg(cfs_rq, false);
9731
	propagate_entity_cfs_rq(se);
9732 9733 9734 9735 9736 9737 9738 9739 9740 9741 9742 9743 9744 9745 9746 9747 9748 9749 9750 9751 9752 9753 9754 9755 9756
}

static void detach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	if (!vruntime_normalized(p)) {
		/*
		 * Fix up our vruntime so that the current sleep doesn't
		 * cause 'unlimited' sleep bonus.
		 */
		place_entity(cfs_rq, se, 0);
		se->vruntime -= cfs_rq->min_vruntime;
	}

	detach_entity_cfs_rq(se);
}

static void attach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	attach_entity_cfs_rq(se);
9757 9758 9759 9760

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9761

9762 9763 9764 9765 9766 9767 9768 9769
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
	attach_task_cfs_rq(p);
9770

9771
	if (task_on_rq_queued(p)) {
9772
		/*
9773 9774 9775
		 * We were most likely switched from sched_rt, so
		 * kick off the schedule if running, otherwise just see
		 * if we can still preempt the current task.
9776
		 */
9777 9778 9779 9780
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9781
	}
9782 9783
}

9784 9785 9786 9787 9788 9789 9790 9791 9792
/* Account for a task changing its policy or group.
 *
 * This routine is mostly called to set cfs_rq->curr field when a task
 * migrates between groups/classes.
 */
static void set_curr_task_fair(struct rq *rq)
{
	struct sched_entity *se = &rq->curr->se;

9793 9794 9795 9796 9797 9798 9799
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

		set_next_entity(cfs_rq, se);
		/* ensure bandwidth has been allocated on our new cfs_rq */
		account_cfs_rq_runtime(cfs_rq, 0);
	}
9800 9801
}

9802 9803
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9804
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9805 9806 9807 9808
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9809
#ifdef CONFIG_SMP
9810
	raw_spin_lock_init(&cfs_rq->removed.lock);
9811
#endif
9812 9813
}

P
Peter Zijlstra 已提交
9814
#ifdef CONFIG_FAIR_GROUP_SCHED
9815 9816 9817 9818 9819 9820 9821 9822
static void task_set_group_fair(struct task_struct *p)
{
	struct sched_entity *se = &p->se;

	set_task_rq(p, task_cpu(p));
	se->depth = se->parent ? se->parent->depth + 1 : 0;
}

9823
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9824
{
9825
	detach_task_cfs_rq(p);
9826
	set_task_rq(p, task_cpu(p));
9827 9828 9829 9830 9831

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9832
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9833
}
9834

9835 9836 9837 9838 9839 9840 9841 9842 9843 9844 9845 9846 9847
static void task_change_group_fair(struct task_struct *p, int type)
{
	switch (type) {
	case TASK_SET_GROUP:
		task_set_group_fair(p);
		break;

	case TASK_MOVE_GROUP:
		task_move_group_fair(p);
		break;
	}
}

9848 9849 9850 9851 9852 9853 9854 9855 9856
void free_fair_sched_group(struct task_group *tg)
{
	int i;

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		if (tg->cfs_rq)
			kfree(tg->cfs_rq[i]);
9857
		if (tg->se)
9858 9859 9860 9861 9862 9863 9864 9865 9866 9867
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct sched_entity *se;
9868
	struct cfs_rq *cfs_rq;
9869 9870
	int i;

K
Kees Cook 已提交
9871
	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
9872 9873
	if (!tg->cfs_rq)
		goto err;
K
Kees Cook 已提交
9874
	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
9875 9876 9877 9878 9879 9880 9881 9882 9883 9884 9885 9886 9887 9888 9889 9890 9891 9892 9893 9894
	if (!tg->se)
		goto err;

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
				      GFP_KERNEL, cpu_to_node(i));
		if (!cfs_rq)
			goto err;

		se = kzalloc_node(sizeof(struct sched_entity),
				  GFP_KERNEL, cpu_to_node(i));
		if (!se)
			goto err_free_rq;

		init_cfs_rq(cfs_rq);
		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
9895
		init_entity_runnable_average(se);
9896 9897 9898 9899 9900 9901 9902 9903 9904 9905
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9906 9907 9908 9909 9910 9911 9912 9913 9914 9915 9916
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];

		raw_spin_lock_irq(&rq->lock);
9917
		update_rq_clock(rq);
9918
		attach_entity_cfs_rq(se);
9919
		sync_throttle(tg, i);
9920 9921 9922 9923
		raw_spin_unlock_irq(&rq->lock);
	}
}

9924
void unregister_fair_sched_group(struct task_group *tg)
9925 9926
{
	unsigned long flags;
9927 9928
	struct rq *rq;
	int cpu;
9929

9930 9931 9932
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
9933

9934 9935 9936 9937 9938 9939 9940 9941 9942 9943 9944 9945 9946
		/*
		 * Only empty task groups can be destroyed; so we can speculatively
		 * check on_list without danger of it being re-added.
		 */
		if (!tg->cfs_rq[cpu]->on_list)
			continue;

		rq = cpu_rq(cpu);

		raw_spin_lock_irqsave(&rq->lock, flags);
		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}
9947 9948 9949 9950 9951 9952 9953 9954 9955 9956 9957 9958 9959 9960 9961 9962 9963 9964 9965
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
9966
	if (!parent) {
9967
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
9968 9969
		se->depth = 0;
	} else {
9970
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
9971 9972
		se->depth = parent->depth + 1;
	}
9973 9974

	se->my_q = cfs_rq;
9975 9976
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
9977 9978 9979 9980 9981 9982 9983 9984 9985 9986 9987 9988 9989 9990 9991 9992 9993 9994 9995 9996 9997 9998 9999 10000
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;

	/*
	 * We can't change the weight of the root cgroup.
	 */
	if (!tg->se[0])
		return -EINVAL;

	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

	mutex_lock(&shares_mutex);
	if (tg->shares == shares)
		goto done;

	tg->shares = shares;
	for_each_possible_cpu(i) {
		struct rq *rq = cpu_rq(i);
10001 10002
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
10003 10004

		/* Propagate contribution to hierarchy */
10005
		rq_lock_irqsave(rq, &rf);
10006
		update_rq_clock(rq);
10007
		for_each_sched_entity(se) {
10008
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10009
			update_cfs_group(se);
10010
		}
10011
		rq_unlock_irqrestore(rq, &rf);
10012 10013 10014 10015 10016 10017 10018 10019 10020 10021 10022 10023 10024 10025 10026
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

10027 10028
void online_fair_sched_group(struct task_group *tg) { }

10029
void unregister_fair_sched_group(struct task_group *tg) { }
10030 10031 10032

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
10033

10034
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10035 10036 10037 10038 10039 10040 10041 10042 10043
{
	struct sched_entity *se = &task->se;
	unsigned int rr_interval = 0;

	/*
	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
	 * idle runqueue:
	 */
	if (rq->cfs.load.weight)
10044
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10045 10046 10047 10048

	return rr_interval;
}

10049 10050 10051
/*
 * All the scheduling class methods:
 */
10052
const struct sched_class fair_sched_class = {
10053
	.next			= &idle_sched_class,
10054 10055 10056
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
10057
	.yield_to_task		= yield_to_task_fair,
10058

I
Ingo Molnar 已提交
10059
	.check_preempt_curr	= check_preempt_wakeup,
10060 10061 10062 10063

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

10064
#ifdef CONFIG_SMP
L
Li Zefan 已提交
10065
	.select_task_rq		= select_task_rq_fair,
10066
	.migrate_task_rq	= migrate_task_rq_fair,
10067

10068 10069
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
10070

10071
	.task_dead		= task_dead_fair,
10072
	.set_cpus_allowed	= set_cpus_allowed_common,
10073
#endif
10074

10075
	.set_curr_task          = set_curr_task_fair,
10076
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
10077
	.task_fork		= task_fork_fair,
10078 10079

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
10080
	.switched_from		= switched_from_fair,
10081
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
10082

10083 10084
	.get_rr_interval	= get_rr_interval_fair,

10085 10086
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
10087
#ifdef CONFIG_FAIR_GROUP_SCHED
10088
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
10089
#endif
10090 10091 10092
};

#ifdef CONFIG_SCHED_DEBUG
10093
void print_cfs_stats(struct seq_file *m, int cpu)
10094
{
10095
	struct cfs_rq *cfs_rq, *pos;
10096

10097
	rcu_read_lock();
10098
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
10099
		print_cfs_rq(m, cpu, cfs_rq);
10100
	rcu_read_unlock();
10101
}
10102 10103 10104 10105 10106 10107 10108 10109 10110 10111 10112 10113 10114 10115 10116 10117 10118 10119 10120 10121 10122

#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;

	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
10123 10124 10125 10126 10127 10128

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

10129
#ifdef CONFIG_NO_HZ_COMMON
10130
	nohz.next_balance = jiffies;
10131
	nohz.next_blocked = jiffies;
10132 10133 10134 10135 10136
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}