fair.c 258.2 KB
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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 <linux/sched/mm.h>
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#include <linux/sched/topology.h>

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#include <linux/latencytop.h>
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#include <linux/cpumask.h>
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#include <linux/cpuidle.h>
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#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
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#include <linux/mempolicy.h>
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#include <linux/migrate.h>
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#include <linux/task_work.h>
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#include <trace/events/sched.h>

#include "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
/*
 * For asym packing, by default the lower numbered cpu has higher priority.
 */
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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/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
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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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}

#define entity_is_task(se)	1

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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.
 *
673
 * s = p*P[w/rw]
674
 */
P
Peter Zijlstra 已提交
675
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
676
{
M
Mike Galbraith 已提交
677
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
678

M
Mike Galbraith 已提交
679
	for_each_sched_entity(se) {
L
Lin Ming 已提交
680
		struct load_weight *load;
681
		struct load_weight lw;
L
Lin Ming 已提交
682 683 684

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
685

M
Mike Galbraith 已提交
686
		if (unlikely(!se->on_rq)) {
687
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
688 689 690 691

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
692
		slice = __calc_delta(slice, se->load.weight, load);
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Mike Galbraith 已提交
693 694
	}
	return slice;
695 696
}

697
/*
A
Andrei Epure 已提交
698
 * We calculate the vruntime slice of a to-be-inserted task.
699
 *
700
 * vs = s/w
701
 */
702
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
703
{
704
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
705 706
}

707
#ifdef CONFIG_SMP
708 709 710

#include "sched-pelt.h"

711
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
712 713
static unsigned long task_h_load(struct task_struct *p);

714 715
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
716
{
717
	struct sched_avg *sa = &se->avg;
718

719 720
	memset(sa, 0, sizeof(*sa));

721 722 723 724 725 726 727
	/*
	 * 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))
728 729
		sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);

730 731
	se->runnable_weight = se->load.weight;

732
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
733
}
734

735
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
736
static void attach_entity_cfs_rq(struct sched_entity *se);
737

738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766
/*
 * 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:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  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;
767
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
768 769 770 771 772 773 774 775 776 777 778 779

	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;
		}
	}
780 781 782 783 784 785 786

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
787
			update_cfs_rq_load_avg(now, cfs_rq);
788 789 790 791 792 793
			attach_entity_load_avg(cfs_rq, se);
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
794
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
795 796 797 798
			return;
		}
	}

799
	attach_entity_cfs_rq(se);
800 801
}

802
#else /* !CONFIG_SMP */
803
void init_entity_runnable_average(struct sched_entity *se)
804 805
{
}
806 807 808
void post_init_entity_util_avg(struct sched_entity *se)
{
}
809 810 811
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
812
#endif /* CONFIG_SMP */
813

814
/*
815
 * Update the current task's runtime statistics.
816
 */
817
static void update_curr(struct cfs_rq *cfs_rq)
818
{
819
	struct sched_entity *curr = cfs_rq->curr;
820
	u64 now = rq_clock_task(rq_of(cfs_rq));
821
	u64 delta_exec;
822 823 824 825

	if (unlikely(!curr))
		return;

826 827
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
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Peter Zijlstra 已提交
828
		return;
829

I
Ingo Molnar 已提交
830
	curr->exec_start = now;
831

832 833 834 835
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
836
	schedstat_add(cfs_rq->exec_clock, delta_exec);
837 838 839 840

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

841 842 843
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

844
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
845
		cpuacct_charge(curtask, delta_exec);
846
		account_group_exec_runtime(curtask, delta_exec);
847
	}
848 849

	account_cfs_rq_runtime(cfs_rq, delta_exec);
850 851
}

852 853 854 855 856
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

857
static inline void
858
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
859
{
860 861 862 863 864 865 866
	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);
867 868

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
869 870
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
871

872
	schedstat_set(se->statistics.wait_start, wait_start);
873 874
}

875
static inline void
876 877 878
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
879 880
	u64 delta;

881 882 883 884
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
885 886 887 888 889 890 891 892 893

	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.
			 */
894
			schedstat_set(se->statistics.wait_start, delta);
895 896 897 898 899
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

900 901 902 903 904
	schedstat_set(se->statistics.wait_max,
		      max(schedstat_val(se->statistics.wait_max), delta));
	schedstat_inc(se->statistics.wait_count);
	schedstat_add(se->statistics.wait_sum, delta);
	schedstat_set(se->statistics.wait_start, 0);
905 906
}

907
static inline void
908 909 910
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
911 912 913 914 915 916 917
	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);
918 919 920 921

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

922 923
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
924 925 926 927

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

928 929
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
			schedstat_set(se->statistics.sleep_max, delta);
930

931 932
		schedstat_set(se->statistics.sleep_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
933 934 935 936 937 938

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
939 940
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
941 942 943 944

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

945 946
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
			schedstat_set(se->statistics.block_max, delta);
947

948 949
		schedstat_set(se->statistics.block_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
950 951 952

		if (tsk) {
			if (tsk->in_iowait) {
953 954
				schedstat_add(se->statistics.iowait_sum, delta);
				schedstat_inc(se->statistics.iowait_count);
955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972
				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);
		}
	}
973 974
}

975 976 977
/*
 * Task is being enqueued - update stats:
 */
978
static inline void
979
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
980
{
981 982 983
	if (!schedstat_enabled())
		return;

984 985 986 987
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
988
	if (se != cfs_rq->curr)
989
		update_stats_wait_start(cfs_rq, se);
990 991 992

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
993 994 995
}

static inline void
996
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
997
{
998 999 1000 1001

	if (!schedstat_enabled())
		return;

1002 1003 1004 1005
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
1006
	if (se != cfs_rq->curr)
1007
		update_stats_wait_end(cfs_rq, se);
1008

1009 1010
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
1011

1012 1013 1014 1015 1016 1017
		if (tsk->state & TASK_INTERRUPTIBLE)
			schedstat_set(se->statistics.sleep_start,
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
			schedstat_set(se->statistics.block_start,
				      rq_clock(rq_of(cfs_rq)));
1018 1019 1020
	}
}

1021 1022 1023 1024
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1025
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1026 1027 1028 1029
{
	/*
	 * We are starting a new run period:
	 */
1030
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1031 1032 1033 1034 1035 1036
}

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

1037 1038
#ifdef CONFIG_NUMA_BALANCING
/*
1039 1040 1041
 * 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.
1042
 */
1043 1044
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1045 1046 1047

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1048

1049 1050 1051
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074
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);

1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098
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)
{
1099
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1100 1101 1102
	unsigned int scan, floor;
	unsigned int windows = 1;

1103 1104
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1105 1106 1107 1108 1109 1110
	floor = 1000 / windows;

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

1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
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);
}

1130 1131
static unsigned int task_scan_max(struct task_struct *p)
{
1132 1133
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1134 1135 1136

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151

	/* 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);
	}

1152 1153 1154
	return max(smin, smax);
}

1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166
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));
}

1167 1168 1169 1170 1171 1172 1173 1174 1175
/* 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)

1176 1177 1178 1179 1180
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1181 1182 1183 1184 1185 1186 1187
/*
 * The averaged statistics, shared & private, memory & cpu,
 * 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)
1188
{
1189
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1190 1191 1192 1193
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1194
	if (!p->numa_faults)
1195 1196
		return 0;

1197 1198
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1199 1200
}

1201 1202 1203 1204 1205
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1206 1207
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1208 1209
}

1210 1211
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1212 1213
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1214 1215
}

1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239
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;
}

1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251
/*
 * 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;
}

1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 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
/* 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;
}

1317 1318 1319 1320 1321 1322
/*
 * 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.
 */
1323 1324
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1325
{
1326
	unsigned long faults, total_faults;
1327

1328
	if (!p->numa_faults)
1329 1330 1331 1332 1333 1334 1335
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1336
	faults = task_faults(p, nid);
1337 1338
	faults += score_nearby_nodes(p, nid, dist, true);

1339
	return 1000 * faults / total_faults;
1340 1341
}

1342 1343
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1344
{
1345 1346 1347 1348 1349 1350 1351 1352
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1353 1354
		return 0;

1355
	faults = group_faults(p, nid);
1356 1357
	faults += score_nearby_nodes(p, nid, dist, false);

1358
	return 1000 * faults / total_faults;
1359 1360
}

1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400
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;

	/*
1401 1402
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1403
	 */
1404 1405
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1406 1407 1408
		return true;

	/*
1409 1410 1411 1412 1413 1414
	 * 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)
1415
	 */
1416 1417
	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;
1418 1419
}

1420
static unsigned long weighted_cpuload(struct rq *rq);
1421 1422
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1423
static unsigned long capacity_of(int cpu);
1424

1425
/* Cached statistics for all CPUs within a node */
1426
struct numa_stats {
1427
	unsigned long nr_running;
1428
	unsigned long load;
1429 1430

	/* Total compute capacity of CPUs on a node */
1431
	unsigned long compute_capacity;
1432 1433

	/* Approximate capacity in terms of runnable tasks on a node */
1434
	unsigned long task_capacity;
1435
	int has_free_capacity;
1436
};
1437

1438 1439 1440 1441 1442
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1443 1444
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1445 1446 1447 1448 1449 1450

	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;
1451
		ns->load += weighted_cpuload(rq);
1452
		ns->compute_capacity += capacity_of(cpu);
1453 1454

		cpus++;
1455 1456
	}

1457 1458 1459 1460 1461
	/*
	 * 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.
	 *
1462 1463
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1464 1465 1466 1467
	 */
	if (!cpus)
		return;

1468 1469 1470 1471 1472 1473
	/* 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));
1474
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1475 1476
}

1477 1478
struct task_numa_env {
	struct task_struct *p;
1479

1480 1481
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1482

1483
	struct numa_stats src_stats, dst_stats;
1484

1485
	int imbalance_pct;
1486
	int dist;
1487 1488 1489

	struct task_struct *best_task;
	long best_imp;
1490 1491 1492
	int best_cpu;
};

1493 1494 1495 1496 1497
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);
1498 1499
	if (p)
		get_task_struct(p);
1500 1501 1502 1503 1504 1505

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

1506
static bool load_too_imbalanced(long src_load, long dst_load,
1507 1508
				struct task_numa_env *env)
{
1509 1510
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521
	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;
1522 1523

	/* We care about the slope of the imbalance, not the direction. */
1524 1525
	if (dst_load < src_load)
		swap(dst_load, src_load);
1526 1527

	/* Is the difference below the threshold? */
1528 1529
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1530 1531 1532 1533 1534
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1535
	 * Compare it with the old imbalance.
1536
	 */
1537
	orig_src_load = env->src_stats.load;
1538
	orig_dst_load = env->dst_stats.load;
1539

1540 1541
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1542

1543 1544 1545 1546 1547
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1548 1549
}

1550 1551 1552 1553 1554 1555
/*
 * 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
 */
1556 1557
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1558 1559 1560 1561
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1562
	long src_load, dst_load;
1563
	long load;
1564
	long imp = env->p->numa_group ? groupimp : taskimp;
1565
	long moveimp = imp;
1566
	int dist = env->dist;
1567 1568

	rcu_read_lock();
1569 1570
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1571 1572
		cur = NULL;

1573 1574 1575 1576 1577 1578 1579
	/*
	 * 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;

1580 1581 1582 1583 1584 1585 1586 1587 1588
	/*
	 * "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
	 * the value is, the more rmeote accesses that would be expected to
	 * be incurred if the tasks were swapped.
	 */
	if (cur) {
		/* Skip this swap candidate if cannot move to the source cpu */
1589
		if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1590 1591
			goto unlock;

1592 1593
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1594
		 * in any group then look only at task weights.
1595
		 */
1596
		if (cur->numa_group == env->p->numa_group) {
1597 1598
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1599 1600 1601 1602 1603 1604
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1605
		} else {
1606 1607 1608 1609 1610 1611
			/*
			 * 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)
1612 1613
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1614
			else
1615 1616
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1617
		}
1618 1619
	}

1620
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1621 1622 1623 1624
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1625
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1626
		    !env->dst_stats.has_free_capacity)
1627 1628 1629 1630 1631 1632
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1633 1634
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1635 1636 1637 1638 1639 1640
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1641 1642 1643
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1644

1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661
	if (moveimp > imp && moveimp > env->best_imp) {
		/*
		 * If the improvement from just moving env->p direction is
		 * better than swapping tasks around, check if a move is
		 * possible. Store a slightly smaller score than moveimp,
		 * so an actually idle CPU will win.
		 */
		if (!load_too_imbalanced(src_load, dst_load, env)) {
			imp = moveimp - 1;
			cur = NULL;
			goto assign;
		}
	}

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

1662
	if (cur) {
1663 1664 1665
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1666 1667
	}

1668
	if (load_too_imbalanced(src_load, dst_load, env))
1669 1670
		goto unlock;

1671 1672 1673 1674
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1675 1676 1677 1678 1679 1680
	if (!cur) {
		/*
		 * select_idle_siblings() uses an per-cpu cpumask that
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1681 1682
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1683 1684
		local_irq_enable();
	}
1685

1686 1687 1688 1689 1690 1691
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1692 1693
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1694 1695 1696 1697 1698
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1699
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1700 1701 1702
			continue;

		env->dst_cpu = cpu;
1703
		task_numa_compare(env, taskimp, groupimp);
1704 1705 1706
	}
}

1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723
/* 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
	 */
1724 1725 1726
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1727 1728 1729 1730 1731
		return true;

	return false;
}

1732 1733 1734 1735
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1736

1737
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1738
		.src_nid = task_node(p),
1739 1740 1741 1742 1743

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1744
		.best_cpu = -1,
1745 1746
	};
	struct sched_domain *sd;
1747
	unsigned long taskweight, groupweight;
1748
	int nid, ret, dist;
1749
	long taskimp, groupimp;
1750

1751
	/*
1752 1753 1754 1755 1756 1757
	 * 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.
1758 1759
	 */
	rcu_read_lock();
1760
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1761 1762
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1763 1764
	rcu_read_unlock();

1765 1766 1767 1768 1769 1770 1771
	/*
	 * 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)) {
1772
		p->numa_preferred_nid = task_node(p);
1773 1774 1775
		return -EINVAL;
	}

1776
	env.dst_nid = p->numa_preferred_nid;
1777 1778 1779 1780 1781 1782
	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;
1783
	update_numa_stats(&env.dst_stats, env.dst_nid);
1784

1785
	/* Try to find a spot on the preferred nid. */
1786 1787
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1788

1789 1790 1791 1792 1793 1794 1795
	/*
	 * 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.
	 */
1796
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1797 1798 1799
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1800

1801
			dist = node_distance(env.src_nid, env.dst_nid);
1802 1803 1804 1805 1806
			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);
			}
1807

1808
			/* Only consider nodes where both task and groups benefit */
1809 1810
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1811
			if (taskimp < 0 && groupimp < 0)
1812 1813
				continue;

1814
			env.dist = dist;
1815 1816
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1817 1818
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1819 1820 1821
		}
	}

1822 1823 1824 1825 1826 1827 1828 1829
	/*
	 * 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.
	 */
1830
	if (p->numa_group) {
1831 1832
		struct numa_group *ng = p->numa_group;

1833 1834 1835 1836 1837
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1838
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1839 1840 1841 1842 1843 1844
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1845

1846 1847 1848 1849
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
1850
	p->numa_scan_period = task_scan_start(p);
1851

1852
	if (env.best_task == NULL) {
1853 1854 1855
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1856 1857 1858 1859
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1860 1861
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1862 1863
	put_task_struct(env.best_task);
	return ret;
1864 1865
}

1866 1867 1868
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1869 1870
	unsigned long interval = HZ;

1871
	/* This task has no NUMA fault statistics yet */
1872
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1873 1874
		return;

1875
	/* Periodically retry migrating the task to the preferred node */
1876 1877
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1878 1879

	/* Success if task is already running on preferred CPU */
1880
	if (task_node(p) == p->numa_preferred_nid)
1881 1882 1883
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1884
	task_numa_migrate(p);
1885 1886
}

1887
/*
1888
 * Find out how many nodes on the workload is actively running on. Do this by
1889 1890 1891 1892
 * 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.
 */
1893
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1894 1895
{
	unsigned long faults, max_faults = 0;
1896
	int nid, active_nodes = 0;
1897 1898 1899 1900 1901 1902 1903 1904 1905

	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);
1906 1907
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1908
	}
1909 1910 1911

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1912 1913
}

1914 1915 1916
/*
 * 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
1917 1918 1919
 * 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.
1920 1921
 */
#define NUMA_PERIOD_SLOTS 10
1922
#define NUMA_PERIOD_THRESHOLD 7
1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933

/*
 * 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;
1934
	int lr_ratio, ps_ratio;
1935 1936 1937 1938 1939 1940 1941 1942
	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
1943 1944 1945
	 * 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
1946
	 */
1947
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963
		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);
1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982
	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;
1983 1984 1985 1986 1987
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1988 1989 1990
		 * 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.
1991
		 */
1992 1993
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1994 1995 1996 1997 1998 1999 2000
	}

	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));
}

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
/*
 * 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 {
2019
		delta = p->se.avg.load_sum;
2020
		*period = LOAD_AVG_MAX;
2021 2022 2023 2024 2025 2026 2027 2028
	}

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

	return delta;
}

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 2070 2071 2072 2073 2074 2075
/*
 * 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;
2076
		nodemask_t max_group = NODE_MASK_NONE;
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 2104 2105 2106 2107 2108 2109
		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. */
2110 2111
		if (!max_faults)
			break;
2112 2113 2114 2115 2116
		nodes = max_group;
	}
	return nid;
}

2117 2118
static void task_numa_placement(struct task_struct *p)
{
2119 2120
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2121
	unsigned long fault_types[2] = { 0, 0 };
2122 2123
	unsigned long total_faults;
	u64 runtime, period;
2124
	spinlock_t *group_lock = NULL;
2125

2126 2127 2128 2129 2130
	/*
	 * 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:
	 */
2131
	seq = READ_ONCE(p->mm->numa_scan_seq);
2132 2133 2134
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2135
	p->numa_scan_period_max = task_scan_max(p);
2136

2137 2138 2139 2140
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2141 2142 2143
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2144
		spin_lock_irq(group_lock);
2145 2146
	}

2147 2148
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2149 2150
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2151
		unsigned long faults = 0, group_faults = 0;
2152
		int priv;
2153

2154
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2155
			long diff, f_diff, f_weight;
2156

2157 2158 2159 2160
			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);
2161

2162
			/* Decay existing window, copy faults since last scan */
2163 2164 2165
			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;
2166

2167 2168 2169 2170 2171 2172 2173 2174
			/*
			 * 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);
2175
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2176
				   (total_faults + 1);
2177 2178
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2179

2180 2181 2182
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2183
			p->total_numa_faults += diff;
2184
			if (p->numa_group) {
2185 2186 2187 2188 2189 2190 2191 2192 2193
				/*
				 * 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;
2194
				p->numa_group->total_faults += diff;
2195
				group_faults += p->numa_group->faults[mem_idx];
2196
			}
2197 2198
		}

2199 2200 2201 2202
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2203 2204 2205 2206 2207 2208 2209

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

2210 2211
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2212
	if (p->numa_group) {
2213
		numa_group_count_active_nodes(p->numa_group);
2214
		spin_unlock_irq(group_lock);
2215
		max_nid = preferred_group_nid(p, max_group_nid);
2216 2217
	}

2218 2219 2220 2221 2222 2223 2224
	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);
2225
	}
2226 2227
}

2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238
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);
}

2239 2240
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2241 2242 2243 2244 2245 2246 2247 2248 2249
{
	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) +
2250
				    4*nr_node_ids*sizeof(unsigned long);
2251 2252 2253 2254 2255 2256

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

		atomic_set(&grp->refcount, 1);
2257 2258
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2259
		spin_lock_init(&grp->lock);
2260
		grp->gid = p->pid;
2261
		/* Second half of the array tracks nids where faults happen */
2262 2263
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2264

2265
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2266
			grp->faults[i] = p->numa_faults[i];
2267

2268
		grp->total_faults = p->total_numa_faults;
2269

2270 2271 2272 2273 2274
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2275
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2276 2277

	if (!cpupid_match_pid(tsk, cpupid))
2278
		goto no_join;
2279 2280 2281

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2282
		goto no_join;
2283 2284 2285

	my_grp = p->numa_group;
	if (grp == my_grp)
2286
		goto no_join;
2287 2288 2289 2290 2291 2292

	/*
	 * 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)
2293
		goto no_join;
2294 2295 2296 2297 2298

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2299
		goto no_join;
2300

2301 2302 2303 2304 2305 2306 2307
	/* 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;
2308

2309 2310 2311
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2312
	if (join && !get_numa_group(grp))
2313
		goto no_join;
2314 2315 2316 2317 2318 2319

	rcu_read_unlock();

	if (!join)
		return;

2320 2321
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2322

2323
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2324 2325
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2326
	}
2327 2328
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2329 2330 2331 2332 2333

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

	spin_unlock(&my_grp->lock);
2334
	spin_unlock_irq(&grp->lock);
2335 2336 2337 2338

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2339 2340 2341 2342 2343
	return;

no_join:
	rcu_read_unlock();
	return;
2344 2345 2346 2347 2348
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2349
	void *numa_faults = p->numa_faults;
2350 2351
	unsigned long flags;
	int i;
2352 2353

	if (grp) {
2354
		spin_lock_irqsave(&grp->lock, flags);
2355
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2356
			grp->faults[i] -= p->numa_faults[i];
2357
		grp->total_faults -= p->total_numa_faults;
2358

2359
		grp->nr_tasks--;
2360
		spin_unlock_irqrestore(&grp->lock, flags);
2361
		RCU_INIT_POINTER(p->numa_group, NULL);
2362 2363 2364
		put_numa_group(grp);
	}

2365
	p->numa_faults = NULL;
2366
	kfree(numa_faults);
2367 2368
}

2369 2370 2371
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2372
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2373 2374
{
	struct task_struct *p = current;
2375
	bool migrated = flags & TNF_MIGRATED;
2376
	int cpu_node = task_node(current);
2377
	int local = !!(flags & TNF_FAULT_LOCAL);
2378
	struct numa_group *ng;
2379
	int priv;
2380

2381
	if (!static_branch_likely(&sched_numa_balancing))
2382 2383
		return;

2384 2385 2386 2387
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2388
	/* Allocate buffer to track faults on a per-node basis */
2389 2390
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2391
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2392

2393 2394
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2395
			return;
2396

2397
		p->total_numa_faults = 0;
2398
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2399
	}
2400

2401 2402 2403 2404 2405 2406 2407 2408
	/*
	 * 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);
2409
		if (!priv && !(flags & TNF_NO_GROUP))
2410
			task_numa_group(p, last_cpupid, flags, &priv);
2411 2412
	}

2413 2414 2415 2416 2417 2418
	/*
	 * 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.
	 */
2419 2420 2421 2422
	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))
2423 2424
		local = 1;

2425
	task_numa_placement(p);
2426

2427 2428 2429 2430 2431
	/*
	 * 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))
2432 2433
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2434 2435
	if (migrated)
		p->numa_pages_migrated += pages;
2436 2437
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2438

2439 2440
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2441
	p->numa_faults_locality[local] += pages;
2442 2443
}

2444 2445
static void reset_ptenuma_scan(struct task_struct *p)
{
2446 2447 2448 2449 2450 2451 2452 2453
	/*
	 * 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:
	 */
2454
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2455 2456 2457
	p->mm->numa_scan_offset = 0;
}

2458 2459 2460 2461 2462 2463 2464 2465 2466
/*
 * 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;
2467
	u64 runtime = p->se.sum_exec_runtime;
2468
	struct vm_area_struct *vma;
2469
	unsigned long start, end;
2470
	unsigned long nr_pte_updates = 0;
2471
	long pages, virtpages;
2472

2473
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486

	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;

2487
	if (!mm->numa_next_scan) {
2488 2489
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2490 2491
	}

2492 2493 2494 2495 2496 2497 2498
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2499 2500
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2501
		p->numa_scan_period = task_scan_start(p);
2502
	}
2503

2504
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2505 2506 2507
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2508 2509 2510 2511 2512 2513
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2514 2515 2516
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2517
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2518 2519
	if (!pages)
		return;
2520

2521

2522 2523
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2524
	vma = find_vma(mm, start);
2525 2526
	if (!vma) {
		reset_ptenuma_scan(p);
2527
		start = 0;
2528 2529
		vma = mm->mmap;
	}
2530
	for (; vma; vma = vma->vm_next) {
2531
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2532
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2533
			continue;
2534
		}
2535

2536 2537 2538 2539 2540 2541 2542 2543 2544 2545
		/*
		 * 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
2546 2547 2548 2549 2550 2551
		/*
		 * 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;
2552

2553 2554 2555 2556
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2557
			nr_pte_updates = change_prot_numa(vma, start, end);
2558 2559

			/*
2560 2561 2562 2563 2564 2565
			 * 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.
2566 2567 2568
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2569
			virtpages -= (end - start) >> PAGE_SHIFT;
2570

2571
			start = end;
2572
			if (pages <= 0 || virtpages <= 0)
2573
				goto out;
2574 2575

			cond_resched();
2576
		} while (end != vma->vm_end);
2577
	}
2578

2579
out:
2580
	/*
P
Peter Zijlstra 已提交
2581 2582 2583 2584
	 * 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.
2585 2586
	 */
	if (vma)
2587
		mm->numa_scan_offset = start;
2588 2589 2590
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601

	/*
	 * 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;
	}
2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626
}

/*
 * 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;

2627
	if (now > curr->node_stamp + period) {
2628
		if (!curr->node_stamp)
2629
			curr->numa_scan_period = task_scan_start(curr);
2630
		curr->node_stamp += period;
2631 2632 2633 2634 2635 2636 2637

		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);
		}
	}
}
2638

2639 2640 2641 2642
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2643 2644 2645 2646 2647 2648 2649 2650

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)
{
}
2651

2652 2653
#endif /* CONFIG_NUMA_BALANCING */

2654 2655 2656 2657
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2658
	if (!parent_entity(se))
2659
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2660
#ifdef CONFIG_SMP
2661 2662 2663 2664 2665 2666
	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);
	}
2667
#endif
2668 2669 2670 2671 2672 2673 2674
	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);
2675
	if (!parent_entity(se))
2676
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2677
#ifdef CONFIG_SMP
2678 2679
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2680
		list_del_init(&se->group_node);
2681
	}
2682
#endif
2683 2684 2685
	cfs_rq->nr_running--;
}

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 2721 2722 2723 2724
/*
 * 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
/*
2725
 * XXX we want to get rid of these helpers and use the full load resolution.
2726 2727 2728 2729 2730 2731
 */
static inline long se_weight(struct sched_entity *se)
{
	return scale_load_down(se->load.weight);
}

2732 2733 2734 2735 2736
static inline long se_runnable(struct sched_entity *se)
{
	return scale_load_down(se->runnable_weight);
}

2737 2738 2739
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2740 2741 2742 2743
	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;
2744 2745 2746 2747 2748
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2749 2750 2751 2752 2753
	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);
2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779
}

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

2780
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2781
			    unsigned long weight, unsigned long runnable)
2782 2783 2784 2785 2786 2787 2788 2789 2790 2791
{
	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);

2792
	se->runnable_weight = runnable;
2793 2794 2795
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2796 2797 2798 2799 2800 2801 2802
	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);
2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818
#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]);

2819
	reweight_entity(cfs_rq, se, weight, weight);
2820 2821 2822
	load->inv_weight = sched_prio_to_wmult[prio];
}

2823 2824
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862
/*
 * 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
2863
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876
 *			    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
 *
2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888
 * 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)
2889 2890 2891 2892 2893 2894 2895 2896 2897
 *
 * 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!
 */
2898
static long calc_group_shares(struct cfs_rq *cfs_rq)
2899
{
2900 2901 2902 2903
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2904

2905
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2906

2907
	tg_weight = atomic_long_read(&tg->load_avg);
2908

2909 2910 2911
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2912

2913
	shares = (tg_shares * load);
2914 2915
	if (tg_weight)
		shares /= tg_weight;
2916

2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928
	/*
	 * 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.
	 */
2929
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
2930
}
2931 2932

/*
2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957
 * 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).
2958 2959 2960
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
2961 2962 2963 2964 2965 2966 2967
	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));
2968 2969 2970 2971

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
2972

2973 2974
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
2975
# endif /* CONFIG_SMP */
2976

2977 2978
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2979 2980 2981 2982 2983
/*
 * 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
2984
{
2985 2986
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
2987

2988
	if (!gcfs_rq)
2989 2990
		return;

2991
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
2992
		return;
2993

2994
#ifndef CONFIG_SMP
2995
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
2996 2997

	if (likely(se->load.weight == shares))
2998
		return;
2999
#else
3000 3001
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
3002
#endif
P
Peter Zijlstra 已提交
3003

3004
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
3005
}
3006

P
Peter Zijlstra 已提交
3007
#else /* CONFIG_FAIR_GROUP_SCHED */
3008
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3009 3010 3011 3012
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

3013 3014
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
3015 3016 3017
	struct rq *rq = rq_of(cfs_rq);

	if (&rq->cfs == cfs_rq) {
3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
		 * a real problem -- added to that it only calls on the local
		 * CPU, so if we enqueue remotely we'll miss an update, but
		 * the next tick/schedule should update.
		 *
		 * 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().
		 */
3034
		cpufreq_update_util(rq, 0);
3035 3036 3037
	}
}

3038
#ifdef CONFIG_SMP
3039 3040 3041 3042
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
3043
static u64 decay_load(u64 val, u64 n)
3044
{
3045 3046
	unsigned int local_n;

3047
	if (unlikely(n > LOAD_AVG_PERIOD * 63))
3048 3049 3050 3051 3052 3053 3054
		return 0;

	/* after bounds checking we can collapse to 32-bit */
	local_n = n;

	/*
	 * As y^PERIOD = 1/2, we can combine
3055 3056
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
3057 3058 3059 3060 3061 3062
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
3063 3064
	}

3065 3066
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
3067 3068
}

3069
static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
3070
{
3071
	u32 c1, c2, c3 = d3; /* y^0 == 1 */
3072

3073
	/*
P
Peter Zijlstra 已提交
3074
	 * c1 = d1 y^p
3075
	 */
3076
	c1 = decay_load((u64)d1, periods);
3077 3078

	/*
P
Peter Zijlstra 已提交
3079
	 *            p-1
3080 3081
	 * c2 = 1024 \Sum y^n
	 *            n=1
3082
	 *
3083 3084
	 *              inf        inf
	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
P
Peter Zijlstra 已提交
3085
	 *              n=0        n=p
3086
	 */
3087
	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
3088 3089

	return c1 + c2 + c3;
3090 3091
}

3092
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
3093

3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104
/*
 * Accumulate the three separate parts of the sum; d1 the remainder
 * of the last (incomplete) period, d2 the span of full periods and d3
 * the remainder of the (incomplete) current period.
 *
 *           d1          d2           d3
 *           ^           ^            ^
 *           |           |            |
 *         |<->|<----------------->|<--->|
 * ... |---x---|------| ... |------|-----x (now)
 *
P
Peter Zijlstra 已提交
3105 3106 3107
 *                           p-1
 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
 *                           n=1
3108
 *
P
Peter Zijlstra 已提交
3109
 *    = u y^p +					(Step 1)
3110
 *
P
Peter Zijlstra 已提交
3111 3112 3113
 *                     p-1
 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2)
 *                     n=1
3114 3115 3116
 */
static __always_inline u32
accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
3117
	       unsigned long load, unsigned long runnable, int running)
3118 3119
{
	unsigned long scale_freq, scale_cpu;
3120
	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133
	u64 periods;

	scale_freq = arch_scale_freq_capacity(NULL, cpu);
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

	delta += sa->period_contrib;
	periods = delta / 1024; /* A period is 1024us (~1ms) */

	/*
	 * Step 1: decay old *_sum if we crossed period boundaries.
	 */
	if (periods) {
		sa->load_sum = decay_load(sa->load_sum, periods);
3134 3135
		sa->runnable_load_sum =
			decay_load(sa->runnable_load_sum, periods);
3136 3137
		sa->util_sum = decay_load((u64)(sa->util_sum), periods);

3138 3139 3140 3141 3142 3143 3144
		/*
		 * Step 2
		 */
		delta %= 1024;
		contrib = __accumulate_pelt_segments(periods,
				1024 - sa->period_contrib, delta);
	}
3145 3146 3147
	sa->period_contrib = delta;

	contrib = cap_scale(contrib, scale_freq);
3148 3149 3150 3151
	if (load)
		sa->load_sum += load * contrib;
	if (runnable)
		sa->runnable_load_sum += runnable * contrib;
3152 3153 3154 3155 3156 3157
	if (running)
		sa->util_sum += contrib * scale_cpu;

	return periods;
}

3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185
/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
3186
static __always_inline int
3187
___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
3188
		  unsigned long load, unsigned long runnable, int running)
3189
{
3190
	u64 delta;
3191

3192
	delta = now - sa->last_update_time;
3193 3194 3195 3196 3197
	/*
	 * This should only happen when time goes backwards, which it
	 * unfortunately does during sched clock init when we swap over to TSC.
	 */
	if ((s64)delta < 0) {
3198
		sa->last_update_time = now;
3199 3200 3201 3202 3203 3204 3205 3206 3207 3208
		return 0;
	}

	/*
	 * Use 1024ns as the unit of measurement since it's a reasonable
	 * approximation of 1us and fast to compute.
	 */
	delta >>= 10;
	if (!delta)
		return 0;
3209 3210

	sa->last_update_time += delta << 10;
3211

3212 3213 3214 3215 3216 3217 3218 3219 3220
	/*
	 * running is a subset of runnable (weight) so running can't be set if
	 * runnable is clear. But there are some corner cases where the current
	 * se has been already dequeued but cfs_rq->curr still points to it.
	 * This means that weight will be 0 but not running for a sched_entity
	 * but also for a cfs_rq if the latter becomes idle. As an example,
	 * this happens during idle_balance() which calls
	 * update_blocked_averages()
	 */
3221 3222
	if (!load)
		runnable = running = 0;
3223

3224 3225 3226 3227 3228 3229 3230
	/*
	 * Now we know we crossed measurement unit boundaries. The *_avg
	 * accrues by two steps:
	 *
	 * Step 1: accumulate *_sum since last_update_time. If we haven't
	 * crossed period boundaries, finish.
	 */
3231
	if (!accumulate_sum(delta, cpu, sa, load, runnable, running))
3232
		return 0;
3233

3234 3235 3236 3237
	return 1;
}

static __always_inline void
3238
___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
3239 3240 3241
{
	u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;

3242 3243 3244
	/*
	 * Step 2: update *_avg.
	 */
3245 3246
	sa->load_avg = div_u64(load * sa->load_sum, divider);
	sa->runnable_load_avg =	div_u64(runnable * sa->runnable_load_sum, divider);
3247 3248
	sa->util_avg = sa->util_sum / divider;
}
3249

3250 3251 3252
/*
 * sched_entity:
 *
3253 3254 3255 3256 3257 3258 3259
 *   task:
 *     se_runnable() == se_weight()
 *
 *   group: [ see update_cfs_group() ]
 *     se_weight()   = tg->weight * grq->load_avg / tg->load_avg
 *     se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
 *
3260 3261 3262
 *   load_sum := runnable_sum
 *   load_avg = se_weight(se) * runnable_avg
 *
3263 3264 3265 3266 3267
 *   runnable_load_sum := runnable_sum
 *   runnable_load_avg = se_runnable(se) * runnable_avg
 *
 * XXX collapse load_sum and runnable_load_sum
 *
3268 3269 3270 3271
 * cfq_rs:
 *
 *   load_sum = \Sum se_weight(se) * se->avg.load_sum
 *   load_avg = \Sum se->avg.load_avg
3272 3273 3274
 *
 *   runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
 *   runnable_load_avg = \Sum se->avg.runable_load_avg
3275 3276
 */

3277 3278 3279
static int
__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
{
3280 3281 3282 3283 3284
	if (entity_is_task(se))
		se->runnable_weight = se->load.weight;

	if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) {
		___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3285 3286 3287 3288
		return 1;
	}

	return 0;
3289 3290 3291 3292 3293
}

static int
__update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3294 3295 3296 3297 3298
	if (entity_is_task(se))
		se->runnable_weight = se->load.weight;

	if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq,
				cfs_rq->curr == se)) {
3299

3300
		___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3301 3302 3303 3304
		return 1;
	}

	return 0;
3305 3306 3307 3308 3309
}

static int
__update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
{
3310 3311
	if (___update_load_sum(now, cpu, &cfs_rq->avg,
				scale_load_down(cfs_rq->load.weight),
3312 3313 3314 3315
				scale_load_down(cfs_rq->runnable_weight),
				cfs_rq->curr != NULL)) {

		___update_load_avg(&cfs_rq->avg, 1, 1);
3316 3317 3318 3319
		return 1;
	}

	return 0;
3320 3321
}

3322
#ifdef CONFIG_FAIR_GROUP_SCHED
3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335
/**
 * 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'.
 *
3336
 * Updating tg's load_avg is necessary before update_cfs_share().
3337
 */
3338
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3339
{
3340
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3341

3342 3343 3344 3345 3346 3347
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3348 3349 3350
	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;
3351
	}
3352
}
3353

3354 3355 3356 3357 3358 3359 3360 3361
/*
 * Called within set_task_rq() right before setting a task's cpu. The
 * 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)
{
3362 3363 3364
	u64 p_last_update_time;
	u64 n_last_update_time;

3365 3366 3367 3368 3369 3370 3371 3372 3373 3374
	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.
	 */
3375 3376
	if (!(se->avg.last_update_time && prev))
		return;
3377 3378

#ifndef CONFIG_64BIT
3379
	{
3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393
		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);
3394
	}
3395
#else
3396 3397
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3398
#endif
3399 3400
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3401
}
3402

3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470

/*
 * 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.
 *
 *
 * Per the above update_tg_cfs_util() is trivial (and still 'wrong') and
 * simply copies the running sum over.
 *
 * 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:
 *
 *   grq->avg.load_avg = grq->load.weight * grq->avg.running_avg	(3)
 *
 * And per (1) we have:
 *
 *   ge->avg.running_avg == grq->avg.running_avg
 *
 * 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).
 *
 * OK, so what then?
 *
 *
 * Another way to look at things is:
 *
 *   grq->avg.load_avg = \Sum se->avg.load_avg
 *
 * Therefore, per (2):
 *
 *   grq->avg.load_avg = \Sum se->load.weight * se->avg.runnable_avg
 *
 * And the very thing we're propagating is a change in that sum (someone
 * joined/left). So we can easily know the runnable change, which would be, per
 * (2) the already tracked se->load_avg divided by the corresponding
 * se->weight.
 *
 * Basically (4) but in differential form:
 *
 *   d(runnable_avg) += se->avg.load_avg / se->load.weight
 *								   (5)
 *   ge->avg.load_avg += ge->load.weight * d(runnable_avg)
 */

3471
static inline void
3472
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

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

	/* 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
3490
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3491
{
3492
	long runnable_sum = gcfs_rq->prop_runnable_sum;
3493 3494
	long runnable_load_avg, load_avg;
	s64 runnable_load_sum, load_sum;
3495

3496 3497
	if (!runnable_sum)
		return;
3498

3499
	gcfs_rq->prop_runnable_sum = 0;
3500

3501 3502
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3503

3504 3505
	add_positive(&se->avg.load_sum, runnable_sum);
	add_positive(&se->avg.load_avg, load_avg);
3506

3507 3508
	add_positive(&cfs_rq->avg.load_avg, load_avg);
	add_positive(&cfs_rq->avg.load_sum, load_sum);
3509

3510 3511 3512 3513 3514 3515
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);

	add_positive(&se->avg.runnable_load_sum, runnable_sum);
	add_positive(&se->avg.runnable_load_avg, runnable_load_avg);

3516
	if (se->on_rq) {
3517 3518
		add_positive(&cfs_rq->avg.runnable_load_avg, runnable_load_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, runnable_load_sum);
3519 3520 3521
	}
}

3522
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3523
{
3524 3525
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3526 3527 3528 3529 3530
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3531
	struct cfs_rq *cfs_rq, *gcfs_rq;
3532 3533 3534 3535

	if (entity_is_task(se))
		return 0;

3536 3537
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3538 3539
		return 0;

3540 3541
	gcfs_rq->propagate = 0;

3542 3543
	cfs_rq = cfs_rq_of(se);

3544
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3545

3546 3547
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3548 3549 3550 3551

	return 1;
}

3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570
/*
 * 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:
	 */
3571
	if (gcfs_rq->propagate)
3572 3573 3574 3575 3576 3577 3578 3579 3580 3581
		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;
}

3582
#else /* CONFIG_FAIR_GROUP_SCHED */
3583

3584
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3585 3586 3587 3588 3589 3590

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

3591
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3592

3593
#endif /* CONFIG_FAIR_GROUP_SCHED */
3594

3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605
/**
 * 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.
 *
3606 3607 3608 3609
 * 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.
3610
 */
3611
static inline int
3612
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3613
{
3614
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3615
	struct sched_avg *sa = &cfs_rq->avg;
3616
	int decayed = 0;
3617

3618 3619
	if (cfs_rq->removed.nr) {
		unsigned long r;
3620
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3621 3622 3623 3624

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3625
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3626 3627 3628 3629
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3630
		sub_positive(&sa->load_avg, r);
3631
		sub_positive(&sa->load_sum, r * divider);
3632

3633
		r = removed_util;
3634
		sub_positive(&sa->util_avg, r);
3635
		sub_positive(&sa->util_sum, r * divider);
3636

3637
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3638 3639

		decayed = 1;
3640
	}
3641

3642
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3643

3644 3645 3646 3647
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3648

3649
	if (decayed)
3650
		cfs_rq_util_change(cfs_rq);
3651

3652
	return decayed;
3653 3654
}

3655 3656 3657 3658 3659 3660 3661 3662
/**
 * 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.
 */
3663 3664
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3665 3666 3667 3668 3669 3670 3671 3672 3673
	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
	 */
3674
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692
	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;

3693
	enqueue_load_avg(cfs_rq, se);
3694 3695
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3696 3697

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3698 3699

	cfs_rq_util_change(cfs_rq);
3700 3701
}

3702 3703 3704 3705 3706 3707 3708 3709
/**
 * 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.
 */
3710 3711
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3712
	dequeue_load_avg(cfs_rq, se);
3713 3714
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3715 3716

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3717 3718

	cfs_rq_util_change(cfs_rq);
3719 3720
}

3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754
/*
 * 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)) {

		attach_entity_load_avg(cfs_rq, se);
		update_tg_load_avg(cfs_rq, 0);

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

3755
#ifndef CONFIG_64BIT
3756 3757
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3758
	u64 last_update_time_copy;
3759
	u64 last_update_time;
3760

3761 3762 3763 3764 3765
	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);
3766 3767 3768

	return last_update_time;
}
3769
#else
3770 3771 3772 3773
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3774 3775
#endif

3776 3777 3778 3779 3780 3781 3782 3783 3784 3785
/*
 * 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);
3786
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3787 3788
}

3789 3790 3791 3792 3793 3794 3795
/*
 * 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);
3796
	unsigned long flags;
3797 3798

	/*
3799 3800 3801 3802 3803 3804 3805
	 * 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.
3806 3807
	 */

3808
	sync_entity_load_avg(se);
3809 3810 3811 3812 3813

	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;
3814
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3815
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3816
}
3817

3818 3819
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3820
	return cfs_rq->avg.runnable_load_avg;
3821 3822 3823 3824 3825 3826 3827
}

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

3828
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3829

3830 3831
#else /* CONFIG_SMP */

3832
static inline int
3833
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3834 3835 3836 3837
{
	return 0;
}

3838 3839
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3840
#define DO_ATTACH	0x0
3841

3842
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3843
{
3844
	cfs_rq_util_change(cfs_rq);
3845 3846
}

3847
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3848

3849 3850 3851 3852 3853
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3854
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3855 3856 3857 3858
{
	return 0;
}

3859
#endif /* CONFIG_SMP */
3860

P
Peter Zijlstra 已提交
3861 3862 3863 3864 3865 3866 3867 3868 3869
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)
3870
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3871 3872 3873
#endif
}

3874 3875 3876
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3877
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3878

3879 3880 3881 3882 3883 3884
	/*
	 * 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
3885
	if (initial && sched_feat(START_DEBIT))
3886
		vruntime += sched_vslice(cfs_rq, se);
3887

3888
	/* sleeps up to a single latency don't count. */
3889
	if (!initial) {
3890
		unsigned long thresh = sysctl_sched_latency;
3891

3892 3893 3894 3895 3896 3897
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3898

3899
		vruntime -= thresh;
3900 3901
	}

3902
	/* ensure we never gain time by being placed backwards. */
3903
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3904 3905
}

3906 3907
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919
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())  {
3920
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3921
			     "stat_blocked and stat_runtime require the "
3922
			     "kernel parameter schedstats=enable or "
3923 3924 3925 3926 3927
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946

/*
 * 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)
 *
3947
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958
 *	  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.
 */

3959
static void
3960
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3961
{
3962 3963 3964
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3965
	/*
3966 3967
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3968
	 */
3969
	if (renorm && curr)
3970 3971
		se->vruntime += cfs_rq->min_vruntime;

3972 3973
	update_curr(cfs_rq);

3974
	/*
3975 3976 3977 3978
	 * 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.
3979
	 */
3980 3981 3982
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3983 3984 3985 3986 3987 3988 3989 3990
	/*
	 * 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
	 */
3991
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3992
	update_cfs_group(se);
3993
	enqueue_runnable_load_avg(cfs_rq, se);
3994
	account_entity_enqueue(cfs_rq, se);
3995

3996
	if (flags & ENQUEUE_WAKEUP)
3997
		place_entity(cfs_rq, se, 0);
3998

3999
	check_schedstat_required();
4000 4001
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
4002
	if (!curr)
4003
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
4004
	se->on_rq = 1;
4005

4006
	if (cfs_rq->nr_running == 1) {
4007
		list_add_leaf_cfs_rq(cfs_rq);
4008 4009
		check_enqueue_throttle(cfs_rq);
	}
4010 4011
}

4012
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
4013
{
4014 4015
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4016
		if (cfs_rq->last != se)
4017
			break;
4018 4019

		cfs_rq->last = NULL;
4020 4021
	}
}
P
Peter Zijlstra 已提交
4022

4023 4024 4025 4026
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4027
		if (cfs_rq->next != se)
4028
			break;
4029 4030

		cfs_rq->next = NULL;
4031
	}
P
Peter Zijlstra 已提交
4032 4033
}

4034 4035 4036 4037
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4038
		if (cfs_rq->skip != se)
4039
			break;
4040 4041

		cfs_rq->skip = NULL;
4042 4043 4044
	}
}

P
Peter Zijlstra 已提交
4045 4046
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
4047 4048 4049 4050 4051
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
4052 4053 4054

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
4055 4056
}

4057
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4058

4059
static void
4060
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4061
{
4062 4063 4064 4065
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
4066 4067 4068 4069 4070 4071 4072 4073 4074

	/*
	 * 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.
	 */
4075
	update_load_avg(cfs_rq, se, UPDATE_TG);
4076
	dequeue_runnable_load_avg(cfs_rq, se);
4077

4078
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
4079

P
Peter Zijlstra 已提交
4080
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4081

4082
	if (se != cfs_rq->curr)
4083
		__dequeue_entity(cfs_rq, se);
4084
	se->on_rq = 0;
4085
	account_entity_dequeue(cfs_rq, se);
4086 4087

	/*
4088 4089 4090 4091
	 * 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.
4092
	 */
4093
	if (!(flags & DEQUEUE_SLEEP))
4094
		se->vruntime -= cfs_rq->min_vruntime;
4095

4096 4097 4098
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

4099
	update_cfs_group(se);
4100 4101 4102 4103 4104 4105 4106 4107 4108

	/*
	 * 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);
4109 4110 4111 4112 4113
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
4114
static void
I
Ingo Molnar 已提交
4115
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4116
{
4117
	unsigned long ideal_runtime, delta_exec;
4118 4119
	struct sched_entity *se;
	s64 delta;
4120

P
Peter Zijlstra 已提交
4121
	ideal_runtime = sched_slice(cfs_rq, curr);
4122
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4123
	if (delta_exec > ideal_runtime) {
4124
		resched_curr(rq_of(cfs_rq));
4125 4126 4127 4128 4129
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140
		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;

4141 4142
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
4143

4144 4145
	if (delta < 0)
		return;
4146

4147
	if (delta > ideal_runtime)
4148
		resched_curr(rq_of(cfs_rq));
4149 4150
}

4151
static void
4152
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4153
{
4154 4155 4156 4157 4158 4159 4160
	/* '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.
		 */
4161
		update_stats_wait_end(cfs_rq, se);
4162
		__dequeue_entity(cfs_rq, se);
4163
		update_load_avg(cfs_rq, se, UPDATE_TG);
4164 4165
	}

4166
	update_stats_curr_start(cfs_rq, se);
4167
	cfs_rq->curr = se;
4168

I
Ingo Molnar 已提交
4169 4170 4171 4172 4173
	/*
	 * 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):
	 */
4174
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4175 4176 4177
		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
4178
	}
4179

4180
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4181 4182
}

4183 4184 4185
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4186 4187 4188 4189 4190 4191 4192
/*
 * 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
 */
4193 4194
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4195
{
4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206
	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 */
4207

4208 4209 4210 4211 4212
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4213 4214 4215 4216 4217 4218 4219 4220 4221 4222
		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;
		}

4223 4224 4225
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4226

4227 4228 4229 4230 4231 4232
	/*
	 * 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;

4233 4234 4235 4236 4237 4238
	/*
	 * 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;

4239
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4240 4241

	return se;
4242 4243
}

4244
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4245

4246
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4247 4248 4249 4250 4251 4252
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4253
		update_curr(cfs_rq);
4254

4255 4256 4257
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4258
	check_spread(cfs_rq, prev);
4259

4260
	if (prev->on_rq) {
4261
		update_stats_wait_start(cfs_rq, prev);
4262 4263
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4264
		/* in !on_rq case, update occurred at dequeue */
4265
		update_load_avg(cfs_rq, prev, 0);
4266
	}
4267
	cfs_rq->curr = NULL;
4268 4269
}

P
Peter Zijlstra 已提交
4270 4271
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4272 4273
{
	/*
4274
	 * Update run-time statistics of the 'current'.
4275
	 */
4276
	update_curr(cfs_rq);
4277

4278 4279 4280
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4281
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4282
	update_cfs_group(curr);
4283

P
Peter Zijlstra 已提交
4284 4285 4286 4287 4288
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4289
	if (queued) {
4290
		resched_curr(rq_of(cfs_rq));
4291 4292
		return;
	}
P
Peter Zijlstra 已提交
4293 4294 4295 4296 4297 4298 4299 4300
	/*
	 * 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
4301
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4302
		check_preempt_tick(cfs_rq, curr);
4303 4304
}

4305 4306 4307 4308 4309 4310

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

#ifdef CONFIG_CFS_BANDWIDTH
4311 4312

#ifdef HAVE_JUMP_LABEL
4313
static struct static_key __cfs_bandwidth_used;
4314 4315 4316

static inline bool cfs_bandwidth_used(void)
{
4317
	return static_key_false(&__cfs_bandwidth_used);
4318 4319
}

4320
void cfs_bandwidth_usage_inc(void)
4321
{
4322 4323 4324 4325 4326 4327
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
4328 4329 4330 4331 4332 4333 4334
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4335 4336
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4337 4338
#endif /* HAVE_JUMP_LABEL */

4339 4340 4341 4342 4343 4344 4345 4346
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4347 4348 4349 4350 4351 4352

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

P
Paul Turner 已提交
4353 4354 4355 4356 4357 4358 4359
/*
 * 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
 */
4360
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371
{
	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);
}

4372 4373 4374 4375 4376
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4377 4378 4379 4380
/* 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))
4381
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4382

4383
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4384 4385
}

4386 4387
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4388 4389 4390
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4391
	u64 amount = 0, min_amount, expires;
4392 4393 4394 4395 4396 4397 4398

	/* 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;
4399
	else {
P
Peter Zijlstra 已提交
4400
		start_cfs_bandwidth(cfs_b);
4401 4402 4403 4404 4405 4406

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4407
	}
P
Paul Turner 已提交
4408
	expires = cfs_b->runtime_expires;
4409 4410 4411
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4412 4413 4414 4415 4416 4417 4418
	/*
	 * we may have advanced our local expiration to account for allowed
	 * spread between our sched_clock and the one on which runtime was
	 * issued.
	 */
	if ((s64)(expires - cfs_rq->runtime_expires) > 0)
		cfs_rq->runtime_expires = expires;
4419 4420

	return cfs_rq->runtime_remaining > 0;
4421 4422
}

P
Paul Turner 已提交
4423 4424 4425 4426 4427
/*
 * 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)
4428
{
P
Paul Turner 已提交
4429 4430 4431
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4432
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4433 4434
		return;

P
Paul Turner 已提交
4435 4436 4437 4438 4439 4440 4441 4442 4443
	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
4444 4445 4446
	 * whether the global deadline has advanced. It is valid to compare
	 * cfs_b->runtime_expires without any locks since we only care about
	 * exact equality, so a partial write will still work.
P
Paul Turner 已提交
4447 4448
	 */

4449
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
4450 4451 4452 4453 4454 4455 4456 4457
		/* 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;
	}
}

4458
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4459 4460
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4461
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4462 4463 4464
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4465 4466
		return;

4467 4468 4469 4470 4471
	/*
	 * 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))
4472
		resched_curr(rq_of(cfs_rq));
4473 4474
}

4475
static __always_inline
4476
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4477
{
4478
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4479 4480 4481 4482 4483
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4484 4485
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4486
	return cfs_bandwidth_used() && cfs_rq->throttled;
4487 4488
}

4489 4490 4491
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4492
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519
}

/*
 * 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);
}

/* updated child weight may affect parent so we have to do this bottom up */
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) {
4520
		/* adjust cfs_rq_clock_task() */
4521
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4522
					     cfs_rq->throttled_clock_task;
4523 4524 4525 4526 4527 4528 4529 4530 4531 4532
	}

	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)];

4533 4534
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4535
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4536 4537 4538 4539 4540
	cfs_rq->throttle_count++;

	return 0;
}

4541
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4542 4543 4544 4545 4546
{
	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
4547
	bool empty;
4548 4549 4550

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

4551
	/* freeze hierarchy runnable averages while throttled */
4552 4553 4554
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571

	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)
4572
		sub_nr_running(rq, task_delta);
4573 4574

	cfs_rq->throttled = 1;
4575
	cfs_rq->throttled_clock = rq_clock(rq);
4576
	raw_spin_lock(&cfs_b->lock);
4577
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4578

4579 4580 4581 4582 4583
	/*
	 * 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
4584 4585 4586 4587 4588 4589 4590 4591

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

4592 4593 4594
	raw_spin_unlock(&cfs_b->lock);
}

4595
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4596 4597 4598 4599 4600 4601 4602
{
	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;

4603
	se = cfs_rq->tg->se[cpu_of(rq)];
4604 4605

	cfs_rq->throttled = 0;
4606 4607 4608

	update_rq_clock(rq);

4609
	raw_spin_lock(&cfs_b->lock);
4610
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4611 4612 4613
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4614 4615 4616
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634
	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)
4635
		add_nr_running(rq, task_delta);
4636 4637 4638

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4639
		resched_curr(rq);
4640 4641 4642 4643 4644 4645
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4646 4647
	u64 runtime;
	u64 starting_runtime = remaining;
4648 4649 4650 4651 4652

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4653
		struct rq_flags rf;
4654

4655
		rq_lock(rq, &rf);
4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671
		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:
4672
		rq_unlock(rq, &rf);
4673 4674 4675 4676 4677 4678

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

4679
	return starting_runtime - remaining;
4680 4681
}

4682 4683 4684 4685 4686 4687 4688 4689
/*
 * 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)
{
4690
	u64 runtime, runtime_expires;
4691
	int throttled;
4692 4693 4694

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4695
		goto out_deactivate;
4696

4697
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4698
	cfs_b->nr_periods += overrun;
4699

4700 4701 4702 4703 4704 4705
	/*
	 * 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
4706 4707 4708

	__refill_cfs_bandwidth_runtime(cfs_b);

4709 4710 4711
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4712
		return 0;
4713 4714
	}

4715 4716 4717
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4718 4719 4720
	runtime_expires = cfs_b->runtime_expires;

	/*
4721 4722 4723 4724 4725
	 * 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.
4726
	 */
4727 4728
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4729 4730 4731 4732 4733 4734 4735
		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);
4736 4737

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4738
	}
4739

4740 4741 4742 4743 4744 4745 4746
	/*
	 * 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;
4747

4748 4749 4750 4751
	return 0;

out_deactivate:
	return 1;
4752
}
4753

4754 4755 4756 4757 4758 4759 4760
/* 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;

4761 4762 4763 4764
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4765
 * hrtimer base being cleared by hrtimer_start. In the case of
4766 4767
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792
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;

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Peter Zijlstra 已提交
4793 4794 4795
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824
}

/* 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)
{
4825 4826 4827
	if (!cfs_bandwidth_used())
		return;

4828
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843
		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 */
4844 4845 4846
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4847
		return;
4848
	}
4849

4850
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4851
		runtime = cfs_b->runtime;
4852

4853 4854 4855 4856 4857 4858 4859 4860 4861 4862
	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)
4863
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4864 4865 4866
	raw_spin_unlock(&cfs_b->lock);
}

4867 4868 4869 4870 4871 4872 4873
/*
 * 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)
{
4874 4875 4876
	if (!cfs_bandwidth_used())
		return;

4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890
	/* 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);
}

4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904
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;
4905
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4906 4907
}

4908
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4909
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4910
{
4911
	if (!cfs_bandwidth_used())
4912
		return false;
4913

4914
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4915
		return false;
4916 4917 4918 4919 4920 4921

	/*
	 * 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))
4922
		return true;
4923 4924

	throttle_cfs_rq(cfs_rq);
4925
	return true;
4926
}
4927 4928 4929 4930 4931

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
4932

4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944
	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;

4945
	raw_spin_lock(&cfs_b->lock);
4946
	for (;;) {
P
Peter Zijlstra 已提交
4947
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4948 4949 4950 4951 4952
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4953 4954
	if (idle)
		cfs_b->period_active = 0;
4955
	raw_spin_unlock(&cfs_b->lock);
4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967

	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
4968
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979
	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
4980
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4981
{
P
Peter Zijlstra 已提交
4982
	lockdep_assert_held(&cfs_b->lock);
4983

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Peter Zijlstra 已提交
4984 4985 4986 4987 4988
	if (!cfs_b->period_active) {
		cfs_b->period_active = 1;
		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}
4989 4990 4991 4992
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4993 4994 4995 4996
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4997 4998 4999 5000
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

5001 5002 5003 5004 5005 5006 5007 5008
/*
 * Both these cpu hotplug callbacks race against unregister_fair_sched_group()
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
5009 5010
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
5011
	struct task_group *tg;
5012

5013 5014 5015 5016 5017 5018
	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)];
5019 5020 5021 5022 5023

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
5024
	rcu_read_unlock();
5025 5026
}

5027
/* cpu offline callback */
5028
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5029
{
5030 5031 5032 5033 5034 5035 5036
	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)];
5037 5038 5039 5040 5041 5042 5043 5044

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
5045
		cfs_rq->runtime_remaining = 1;
5046 5047 5048 5049 5050 5051
		/*
		 * Offline rq is schedulable till cpu is completely disabled
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

5052 5053 5054
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
5055
	rcu_read_unlock();
5056 5057 5058
}

#else /* CONFIG_CFS_BANDWIDTH */
5059 5060
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
5061
	return rq_clock_task(rq_of(cfs_rq));
5062 5063
}

5064
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5065
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5066
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5067
static inline void sync_throttle(struct task_group *tg, int cpu) {}
5068
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5069 5070 5071 5072 5073

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084

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;
}
5085 5086 5087 5088 5089

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) {}
5090 5091
#endif

5092 5093 5094 5095 5096
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) {}
5097
static inline void update_runtime_enabled(struct rq *rq) {}
5098
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5099 5100 5101

#endif /* CONFIG_CFS_BANDWIDTH */

5102 5103 5104 5105
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
5106 5107 5108 5109 5110 5111
#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);

5112
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
5113

5114
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
5115 5116 5117 5118 5119 5120
		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)
5121
				resched_curr(rq);
P
Peter Zijlstra 已提交
5122 5123
			return;
		}
5124
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
5125 5126
	}
}
5127 5128 5129 5130 5131 5132 5133 5134 5135 5136

/*
 * 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;

5137
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5138 5139 5140 5141 5142
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5143
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
5144 5145 5146 5147
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5148 5149 5150 5151

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
5152 5153
#endif

5154 5155 5156 5157 5158
/*
 * 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:
 */
5159
static void
5160
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5161 5162
{
	struct cfs_rq *cfs_rq;
5163
	struct sched_entity *se = &p->se;
5164

5165 5166 5167 5168 5169 5170
	/*
	 * 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)
5171
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5172

5173
	for_each_sched_entity(se) {
5174
		if (se->on_rq)
5175 5176
			break;
		cfs_rq = cfs_rq_of(se);
5177
		enqueue_entity(cfs_rq, se, flags);
5178 5179 5180 5181 5182 5183

		/*
		 * 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.
5184
		 */
5185 5186
		if (cfs_rq_throttled(cfs_rq))
			break;
5187
		cfs_rq->h_nr_running++;
5188

5189
		flags = ENQUEUE_WAKEUP;
5190
	}
P
Peter Zijlstra 已提交
5191

P
Peter Zijlstra 已提交
5192
	for_each_sched_entity(se) {
5193
		cfs_rq = cfs_rq_of(se);
5194
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5195

5196 5197 5198
		if (cfs_rq_throttled(cfs_rq))
			break;

5199
		update_load_avg(cfs_rq, se, UPDATE_TG);
5200
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5201 5202
	}

Y
Yuyang Du 已提交
5203
	if (!se)
5204
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5205

5206
	hrtick_update(rq);
5207 5208
}

5209 5210
static void set_next_buddy(struct sched_entity *se);

5211 5212 5213 5214 5215
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5216
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5217 5218
{
	struct cfs_rq *cfs_rq;
5219
	struct sched_entity *se = &p->se;
5220
	int task_sleep = flags & DEQUEUE_SLEEP;
5221 5222 5223

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5224
		dequeue_entity(cfs_rq, se, flags);
5225 5226 5227 5228 5229 5230 5231 5232 5233

		/*
		 * 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;
5234
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5235

5236
		/* Don't dequeue parent if it has other entities besides us */
5237
		if (cfs_rq->load.weight) {
5238 5239
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5240 5241 5242 5243
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5244 5245
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5246
			break;
5247
		}
5248
		flags |= DEQUEUE_SLEEP;
5249
	}
P
Peter Zijlstra 已提交
5250

P
Peter Zijlstra 已提交
5251
	for_each_sched_entity(se) {
5252
		cfs_rq = cfs_rq_of(se);
5253
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5254

5255 5256 5257
		if (cfs_rq_throttled(cfs_rq))
			break;

5258
		update_load_avg(cfs_rq, se, UPDATE_TG);
5259
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5260 5261
	}

Y
Yuyang Du 已提交
5262
	if (!se)
5263
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5264

5265
	hrtick_update(rq);
5266 5267
}

5268
#ifdef CONFIG_SMP
5269 5270 5271 5272 5273

/* 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);

5274
#ifdef CONFIG_NO_HZ_COMMON
5275 5276 5277 5278 5279
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5280
 * The exact cpuload calculated at every tick would be:
5281
 *
5282 5283 5284 5285 5286 5287 5288
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
 * 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:
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
5289 5290 5291
 *
 * decay_load_missed() below does efficient calculation of
 *
5292 5293 5294 5295 5296 5297
 *   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())
5298
 *
5299
 * The calculation is approximated on a 128 point scale.
5300 5301
 */
#define DEGRADE_SHIFT		7
5302 5303 5304 5305 5306 5307 5308 5309 5310

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 }
};
5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339

/*
 * 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;
}
5340
#endif /* CONFIG_NO_HZ_COMMON */
5341

5342
/**
5343
 * __cpu_load_update - update the rq->cpu_load[] statistics
5344 5345 5346 5347
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5348
 * Update rq->cpu_load[] statistics. This function is usually called every
5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374
 * 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
5375
 * term.
5376
 */
5377 5378
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5379
{
5380
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391
	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 */

5392
		old_load = this_rq->cpu_load[i];
5393
#ifdef CONFIG_NO_HZ_COMMON
5394
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5395 5396 5397 5398 5399 5400 5401 5402 5403
		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;
		}
5404
#endif
5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419
		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;
	}

	sched_avg_update(this_rq);
}

5420
/* Used instead of source_load when we know the type == 0 */
5421
static unsigned long weighted_cpuload(struct rq *rq)
5422
{
5423
	return cfs_rq_runnable_load_avg(&rq->cfs);
5424 5425
}

5426
#ifdef CONFIG_NO_HZ_COMMON
5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * 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)
5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454
{
	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.
		 */
5455
		cpu_load_update(this_rq, load, pending_updates);
5456 5457 5458
	}
}

5459 5460 5461 5462
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5463
static void cpu_load_update_idle(struct rq *this_rq)
5464 5465 5466 5467
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5468
	if (weighted_cpuload(this_rq))
5469 5470
		return;

5471
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5472 5473 5474
}

/*
5475 5476 5477 5478
 * 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.
5479
 */
5480
void cpu_load_update_nohz_start(void)
5481 5482
{
	struct rq *this_rq = this_rq();
5483 5484 5485 5486 5487 5488

	/*
	 * 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.
	 */
5489
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5490 5491 5492 5493 5494 5495 5496
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5497
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5498 5499
	struct rq *this_rq = this_rq();
	unsigned long load;
5500
	struct rq_flags rf;
5501 5502 5503 5504

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

5505
	load = weighted_cpuload(this_rq);
5506
	rq_lock(this_rq, &rf);
5507
	update_rq_clock(this_rq);
5508
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5509
	rq_unlock(this_rq, &rf);
5510
}
5511 5512 5513 5514 5515 5516 5517 5518
#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)
{
5519
#ifdef CONFIG_NO_HZ_COMMON
5520 5521
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5522
#endif
5523 5524
	cpu_load_update(this_rq, load, 1);
}
5525 5526 5527 5528

/*
 * Called from scheduler_tick()
 */
5529
void cpu_load_update_active(struct rq *this_rq)
5530
{
5531
	unsigned long load = weighted_cpuload(this_rq);
5532 5533 5534 5535 5536

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5537 5538
}

5539 5540 5541 5542 5543 5544 5545 5546 5547 5548
/*
 * Return a low guess at the load of a migration-source cpu weighted
 * 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);
5549
	unsigned long total = weighted_cpuload(rq);
5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563

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

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

/*
 * Return a high guess at the load of a migration-target cpu weighted
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5564
	unsigned long total = weighted_cpuload(rq);
5565 5566 5567 5568 5569 5570 5571

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

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

5572
static unsigned long capacity_of(int cpu)
5573
{
5574
	return cpu_rq(cpu)->cpu_capacity;
5575 5576
}

5577 5578 5579 5580 5581
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5582 5583 5584
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5585
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5586
	unsigned long load_avg = weighted_cpuload(rq);
5587 5588

	if (nr_running)
5589
		return load_avg / nr_running;
5590 5591 5592 5593

	return 0;
}

P
Peter Zijlstra 已提交
5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610
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
5611 5612
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5613
 *
M
Mike Galbraith 已提交
5614
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626
 * 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
5627
 */
5628 5629
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5630 5631
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5632
	int factor = this_cpu_read(sd_llc_size);
5633

M
Mike Galbraith 已提交
5634 5635 5636 5637 5638
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5639 5640
}

5641
/*
5642 5643 5644
 * 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.
5645
 *
5646 5647
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is (or
 *			will be) idle.
5648 5649 5650 5651
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5652 5653 5654
 */

static bool
5655 5656
wake_affine_idle(struct sched_domain *sd, struct task_struct *p,
		 int this_cpu, int prev_cpu, int sync)
5657
{
5658
	if (idle_cpu(this_cpu))
5659 5660
		return true;

5661 5662
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
		return true;
5663

5664
	return false;
5665 5666 5667
}

static bool
5668 5669
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5670 5671 5672 5673
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5674 5675
	this_eff_load = target_load(this_cpu, sd->wake_idx);
	prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5676 5677 5678 5679

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

5680
		if (current_load > this_eff_load)
5681 5682
			return true;

5683
		this_eff_load -= current_load;
5684 5685 5686 5687
	}

	task_load = task_h_load(p);

5688 5689 5690 5691
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5692

5693 5694 5695 5696
	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);
5697 5698 5699 5700

	return this_eff_load <= prev_eff_load;
}

5701 5702
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
		       int prev_cpu, int sync)
5703
{
5704
	int this_cpu = smp_processor_id();
5705
	bool affine = false;
5706

5707 5708
	if (sched_feat(WA_IDLE) && !affine)
		affine = wake_affine_idle(sd, p, this_cpu, prev_cpu, sync);
5709

5710 5711
	if (sched_feat(WA_WEIGHT) && !affine)
		affine = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5712

5713
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5714 5715 5716 5717
	if (affine) {
		schedstat_inc(sd->ttwu_move_affine);
		schedstat_inc(p->se.statistics.nr_wakeups_affine);
	}
5718

5719
	return affine;
5720 5721
}

5722 5723 5724 5725 5726 5727 5728 5729
static inline int task_util(struct task_struct *p);
static int cpu_util_wake(int cpu, struct task_struct *p);

static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
{
	return capacity_orig_of(cpu) - cpu_util_wake(cpu, p);
}

5730 5731 5732 5733 5734
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5735
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5736
		  int this_cpu, int sd_flag)
5737
{
5738
	struct sched_group *idlest = NULL, *group = sd->groups;
5739
	struct sched_group *most_spare_sg = NULL;
5740 5741
	unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0;
5742
	unsigned long most_spare = 0, this_spare = 0;
5743
	int load_idx = sd->forkexec_idx;
5744 5745 5746
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5747

5748 5749 5750
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5751
	do {
5752 5753
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5754 5755
		int local_group;
		int i;
5756

5757
		/* Skip over this group if it has no CPUs allowed */
5758
		if (!cpumask_intersects(sched_group_span(group),
5759
					&p->cpus_allowed))
5760 5761 5762
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5763
					       sched_group_span(group));
5764

5765 5766 5767 5768
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5769
		avg_load = 0;
5770
		runnable_load = 0;
5771
		max_spare_cap = 0;
5772

5773
		for_each_cpu(i, sched_group_span(group)) {
5774 5775 5776 5777 5778 5779
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5780 5781 5782
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5783 5784 5785 5786 5787

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5788 5789
		}

5790
		/* Adjust by relative CPU capacity of the group */
5791 5792 5793 5794
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5795 5796

		if (local_group) {
5797 5798
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5799 5800
			this_spare = max_spare_cap;
		} else {
5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
				 * so we can pick this new cpu
				 */
				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
				 * blocked load into account through avg_load.
				 */
				min_avg_load = avg_load;
5816 5817 5818 5819 5820 5821 5822
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5823 5824 5825
		}
	} while (group = group->next, group != sd->groups);

5826 5827 5828 5829 5830 5831
	/*
	 * 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.
5832 5833 5834 5835
	 *
	 * 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.
5836
	 */
5837 5838 5839
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5840
	if (this_spare > task_util(p) / 2 &&
5841
	    imbalance_scale*this_spare > 100*most_spare)
5842
		return NULL;
5843 5844

	if (most_spare > task_util(p) / 2)
5845 5846
		return most_spare_sg;

5847
skip_spare:
5848 5849 5850 5851
	if (!idlest)
		return NULL;

	if (min_runnable_load > (this_runnable_load + imbalance))
5852
		return NULL;
5853 5854 5855 5856 5857

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

5858 5859 5860 5861
	return idlest;
}

/*
5862
 * find_idlest_group_cpu - find the idlest cpu among the cpus in group.
5863 5864
 */
static int
5865
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5866 5867
{
	unsigned long load, min_load = ULONG_MAX;
5868 5869 5870 5871
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5872 5873
	int i;

5874 5875
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5876
		return cpumask_first(sched_group_span(group));
5877

5878
	/* Traverse only the allowed CPUs */
5879
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901
		if (idle_cpu(i)) {
			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;
			}
5902
		} else if (shallowest_idle_cpu == -1) {
5903
			load = weighted_cpuload(cpu_rq(i));
5904 5905 5906 5907
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5908 5909 5910
		}
	}

5911
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5912
}
5913

5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
	int new_cpu = prev_cpu;

	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);
5936
		if (new_cpu == cpu) {
5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
		}

		/* Now try balancing at a lower domain level of new_cpu */
		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;
		}
		/* while loop will break here if sd == NULL */
	}

	return new_cpu;
}

5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986
#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
5987
void __update_idle_core(struct rq *rq)
5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016
{
	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;

		if (!idle_cpu(cpu))
			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);
6017
	int core, cpu;
6018

P
Peter Zijlstra 已提交
6019 6020 6021
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6022 6023 6024
	if (!test_idle_cores(target, false))
		return -1;

6025
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
6026

6027
	for_each_cpu_wrap(core, cpus, target) {
6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
			if (!idle_cpu(cpu))
				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
6055 6056 6057
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6058
	for_each_cpu(cpu, cpu_smt_mask(target)) {
6059
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085
			continue;
		if (idle_cpu(cpu))
			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).
6086
 */
6087 6088
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
6089
	struct sched_domain *this_sd;
6090
	u64 avg_cost, avg_idle;
6091 6092
	u64 time, cost;
	s64 delta;
6093
	int cpu, nr = INT_MAX;
6094

6095 6096 6097 6098
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

6099 6100 6101 6102
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
6103 6104 6105 6106
	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)
6107 6108
		return -1;

6109 6110 6111 6112 6113 6114 6115 6116
	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;
	}

6117 6118
	time = local_clock();

6119
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6120 6121
		if (!--nr)
			return -1;
6122
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137
			continue;
		if (idle_cpu(cpu))
			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.
6138
 */
6139
static int select_idle_sibling(struct task_struct *p, int prev, int target)
6140
{
6141
	struct sched_domain *sd;
6142
	int i;
6143

6144 6145
	if (idle_cpu(target))
		return target;
6146 6147

	/*
6148
	 * If the previous cpu is cache affine and idle, don't be stupid.
6149
	 */
6150 6151
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
6152

6153
	sd = rcu_dereference(per_cpu(sd_llc, target));
6154 6155
	if (!sd)
		return target;
6156

6157 6158 6159
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6160

6161 6162 6163 6164 6165 6166 6167
	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;
6168

6169 6170
	return target;
}
6171

6172
/*
6173
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
6174
 * tasks. The unit of the return value must be the one of capacity so we can
6175 6176
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196
 *
 * 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.
 *
 * 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).
6197
 */
6198
static int cpu_util(int cpu)
6199
{
6200
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
6201 6202
	unsigned long capacity = capacity_orig_of(cpu);

6203
	return (util >= capacity) ? capacity : util;
6204
}
6205

6206 6207 6208 6209 6210
static inline int task_util(struct task_struct *p)
{
	return p->se.avg.util_avg;
}

6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228
/*
 * cpu_util_wake: Compute cpu utilization with any contributions from
 * the waking task p removed.
 */
static int cpu_util_wake(int cpu, struct task_struct *p)
{
	unsigned long util, capacity;

	/* Task has no contribution or is new */
	if (cpu != task_cpu(p) || !p->se.avg.last_update_time)
		return cpu_util(cpu);

	capacity = capacity_orig_of(cpu);
	util = max_t(long, cpu_rq(cpu)->cfs.avg.util_avg - task_util(p), 0);

	return (util >= capacity) ? capacity : util;
}

6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242 6243 6244 6245 6246
/*
 * 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;

6247 6248 6249
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6250 6251 6252
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6253
/*
6254 6255 6256
 * 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.
6257
 *
6258 6259
 * 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.
6260
 *
6261
 * Returns the target cpu number.
6262 6263 6264
 *
 * preempt must be disabled.
 */
6265
static int
6266
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6267
{
6268
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
6269
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6270
	int new_cpu = prev_cpu;
6271
	int want_affine = 0;
6272
	int sync = wake_flags & WF_SYNC;
6273

P
Peter Zijlstra 已提交
6274 6275
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6276
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6277
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6278
	}
6279

6280
	rcu_read_lock();
6281
	for_each_domain(cpu, tmp) {
6282
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6283
			break;
6284

6285
		/*
6286 6287
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
6288
		 */
6289 6290 6291
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
6292
			break;
6293
		}
6294

6295
		if (tmp->flags & sd_flag)
6296
			sd = tmp;
M
Mike Galbraith 已提交
6297 6298
		else if (!want_affine)
			break;
6299 6300
	}

M
Mike Galbraith 已提交
6301 6302
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
6303 6304 6305 6306
		if (cpu == prev_cpu)
			goto pick_cpu;

		if (wake_affine(affine_sd, p, prev_cpu, sync))
M
Mike Galbraith 已提交
6307
			new_cpu = cpu;
6308
	}
6309

6310 6311 6312 6313 6314 6315 6316 6317 6318
	if (sd && !(sd_flag & SD_BALANCE_FORK)) {
		/*
		 * We're going to need the task's util for capacity_spare_wake
		 * in find_idlest_group. Sync it up to prev_cpu's
		 * last_update_time.
		 */
		sync_entity_load_avg(&p->se);
	}

M
Mike Galbraith 已提交
6319
	if (!sd) {
6320
pick_cpu:
M
Mike Galbraith 已提交
6321
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
6322
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
6323

6324 6325
	} else {
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6326
	}
6327
	rcu_read_unlock();
6328

6329
	return new_cpu;
6330
}
6331

6332 6333
static void detach_entity_cfs_rq(struct sched_entity *se);

6334 6335 6336
/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
6337
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6338
 */
6339
static void migrate_task_rq_fair(struct task_struct *p)
6340
{
6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366
	/*
	 * 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;
	}

6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385
	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);
	}
6386 6387 6388

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6389 6390

	/* We have migrated, no longer consider this task hot */
6391
	p->se.exec_start = 0;
6392
}
6393 6394 6395 6396 6397

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6398 6399
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
6400 6401
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6402 6403 6404 6405
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6406 6407
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6408 6409 6410 6411 6412 6413 6414 6415 6416
	 *
	 * 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.
6417
	 */
6418
	return calc_delta_fair(gran, se);
6419 6420
}

6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442
/*
 * 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;

P
Peter Zijlstra 已提交
6443
	gran = wakeup_gran(curr, se);
6444 6445 6446 6447 6448 6449
	if (vdiff > gran)
		return 1;

	return 0;
}

6450 6451
static void set_last_buddy(struct sched_entity *se)
{
6452 6453 6454
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6455 6456 6457
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6458
		cfs_rq_of(se)->last = se;
6459
	}
6460 6461 6462 6463
}

static void set_next_buddy(struct sched_entity *se)
{
6464 6465 6466
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6467 6468 6469
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6470
		cfs_rq_of(se)->next = se;
6471
	}
6472 6473
}

6474 6475
static void set_skip_buddy(struct sched_entity *se)
{
6476 6477
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6478 6479
}

6480 6481 6482
/*
 * Preempt the current task with a newly woken task if needed:
 */
6483
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6484 6485
{
	struct task_struct *curr = rq->curr;
6486
	struct sched_entity *se = &curr->se, *pse = &p->se;
6487
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6488
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6489
	int next_buddy_marked = 0;
6490

I
Ingo Molnar 已提交
6491 6492 6493
	if (unlikely(se == pse))
		return;

6494
	/*
6495
	 * This is possible from callers such as attach_tasks(), in which we
6496 6497 6498 6499 6500 6501 6502
	 * 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;

6503
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6504
		set_next_buddy(pse);
6505 6506
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6507

6508 6509 6510
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6511 6512 6513 6514 6515 6516
	 *
	 * 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.
6517 6518 6519 6520
	 */
	if (test_tsk_need_resched(curr))
		return;

6521 6522 6523 6524 6525
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6526
	/*
6527 6528
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6529
	 */
6530
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6531
		return;
6532

6533
	find_matching_se(&se, &pse);
6534
	update_curr(cfs_rq_of(se));
6535
	BUG_ON(!pse);
6536 6537 6538 6539 6540 6541 6542
	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);
6543
		goto preempt;
6544
	}
6545

6546
	return;
6547

6548
preempt:
6549
	resched_curr(rq);
6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563
	/*
	 * 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);
6564 6565
}

6566
static struct task_struct *
6567
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6568 6569 6570
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6571
	struct task_struct *p;
6572
	int new_tasks;
6573

6574
again:
6575
	if (!cfs_rq->nr_running)
6576
		goto idle;
6577

6578
#ifdef CONFIG_FAIR_GROUP_SCHED
6579
	if (prev->sched_class != &fair_sched_class)
6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598
		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.
		 */
6599 6600 6601 6602 6603
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6604

6605 6606 6607
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6608
			 * Therefore the nr_running test will indeed
6609 6610
			 * be correct.
			 */
6611 6612 6613 6614 6615 6616
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6617
				goto simple;
6618
			}
6619
		}
6620 6621 6622 6623 6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652

		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);
	}

6653
	goto done;
6654 6655
simple:
#endif
6656

6657
	put_prev_task(rq, prev);
6658

6659
	do {
6660
		se = pick_next_entity(cfs_rq, NULL);
6661
		set_next_entity(cfs_rq, se);
6662 6663 6664
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6665
	p = task_of(se);
6666

6667 6668 6669 6670 6671 6672 6673 6674 6675 6676
done: __maybe_unused
#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

6677 6678
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6679 6680

	return p;
6681 6682

idle:
6683 6684
	new_tasks = idle_balance(rq, rf);

6685 6686 6687 6688 6689
	/*
	 * 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.
	 */
6690
	if (new_tasks < 0)
6691 6692
		return RETRY_TASK;

6693
	if (new_tasks > 0)
6694 6695 6696
		goto again;

	return NULL;
6697 6698 6699 6700 6701
}

/*
 * Account for a descheduled task:
 */
6702
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6703 6704 6705 6706 6707 6708
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6709
		put_prev_entity(cfs_rq, se);
6710 6711 6712
	}
}

6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737
/*
 * 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);
6738 6739 6740 6741 6742
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6743
		rq_clock_skip_update(rq, true);
6744 6745 6746 6747 6748
	}

	set_skip_buddy(se);
}

6749 6750 6751 6752
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6753 6754
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6755 6756 6757 6758 6759 6760 6761 6762 6763 6764
		return false;

	/* Tell the scheduler that we'd really like pse to run next. */
	set_next_buddy(se);

	yield_task_fair(rq);

	return true;
}

6765
#ifdef CONFIG_SMP
6766
/**************************************************
P
Peter Zijlstra 已提交
6767 6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * 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)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6783
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6784 6785 6786 6787 6788 6789
 *
 * 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)
 *
6790
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
6791 6792 6793 6794 6795 6796
 * 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):
 *
6797
 *   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
6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835
 *
 * 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)
 * for all i,j solution, we create a tree of cpus that follows the hardware
 * topology where each level pairs two lower groups (or better). This results
 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
 * tree to only the first of the previous level and we decrease the frequency
 * of load-balance at each level inv. proportional to the number of cpus in
 * 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
 *         |         |     `- number of cpus doing load-balance
 *         |         `- 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
 * to every other cpu in at most O(log n) steps:
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6836
 *             log_2 n
P
Peter Zijlstra 已提交
6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881
 *   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)
 *
 * Showing there's indeed a path between every cpu in at most O(log n) steps.
 * 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
 * balancing is more aggressive and has the newly idle cpu iterate up the domain
 * 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)
 *
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
 *
 * 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.]
6882
 */
6883

6884 6885
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6886 6887
enum fbq_type { regular, remote, all };

6888
#define LBF_ALL_PINNED	0x01
6889
#define LBF_NEED_BREAK	0x02
6890 6891
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6892 6893 6894 6895 6896

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6897
	int			src_cpu;
6898 6899 6900 6901

	int			dst_cpu;
	struct rq		*dst_rq;

6902 6903
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6904
	enum cpu_idle_type	idle;
6905
	long			imbalance;
6906 6907 6908
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6909
	unsigned int		flags;
6910 6911 6912 6913

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6914 6915

	enum fbq_type		fbq_type;
6916
	struct list_head	tasks;
6917 6918
};

6919 6920 6921
/*
 * Is this task likely cache-hot:
 */
6922
static int task_hot(struct task_struct *p, struct lb_env *env)
6923 6924 6925
{
	s64 delta;

6926 6927
	lockdep_assert_held(&env->src_rq->lock);

6928 6929 6930 6931 6932 6933 6934 6935 6936
	if (p->sched_class != &fair_sched_class)
		return 0;

	if (unlikely(p->policy == SCHED_IDLE))
		return 0;

	/*
	 * Buddy candidates are cache hot:
	 */
6937
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6938 6939 6940 6941 6942 6943 6944 6945 6946
			(&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;

6947
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6948 6949 6950 6951

	return delta < (s64)sysctl_sched_migration_cost;
}

6952
#ifdef CONFIG_NUMA_BALANCING
6953
/*
6954 6955 6956
 * 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.
6957
 */
6958
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6959
{
6960
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6961
	unsigned long src_faults, dst_faults;
6962 6963
	int src_nid, dst_nid;

6964
	if (!static_branch_likely(&sched_numa_balancing))
6965 6966
		return -1;

6967
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6968
		return -1;
6969 6970 6971 6972

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

6973
	if (src_nid == dst_nid)
6974
		return -1;
6975

6976 6977 6978 6979 6980 6981 6982
	/* 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;
	}
6983

6984 6985
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6986
		return 0;
6987

6988 6989 6990 6991
	/* Leaving a core idle is often worse than degrading locality. */
	if (env->idle != CPU_NOT_IDLE)
		return -1;

6992 6993 6994 6995 6996 6997
	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);
6998 6999
	}

7000
	return dst_faults < src_faults;
7001 7002
}

7003
#else
7004
static inline int migrate_degrades_locality(struct task_struct *p,
7005 7006
					     struct lb_env *env)
{
7007
	return -1;
7008
}
7009 7010
#endif

7011 7012 7013 7014
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
7015
int can_migrate_task(struct task_struct *p, struct lb_env *env)
7016
{
7017
	int tsk_cache_hot;
7018 7019 7020

	lockdep_assert_held(&env->src_rq->lock);

7021 7022
	/*
	 * We do not migrate tasks that are:
7023
	 * 1) throttled_lb_pair, or
7024
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
7025 7026
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
7027
	 */
7028 7029 7030
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

7031
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7032
		int cpu;
7033

7034
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7035

7036 7037
		env->flags |= LBF_SOME_PINNED;

7038 7039 7040 7041 7042
		/*
		 * Remember if this task can be migrated to any other cpu in
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
7043 7044
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
7045
		 */
7046
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7047 7048
			return 0;

7049 7050
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7051
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7052
				env->flags |= LBF_DST_PINNED;
7053 7054 7055
				env->new_dst_cpu = cpu;
				break;
			}
7056
		}
7057

7058 7059
		return 0;
	}
7060 7061

	/* Record that we found atleast one task that could run on dst_cpu */
7062
	env->flags &= ~LBF_ALL_PINNED;
7063

7064
	if (task_running(env->src_rq, p)) {
7065
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7066 7067 7068 7069 7070
		return 0;
	}

	/*
	 * Aggressive migration if:
7071 7072 7073
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
7074
	 */
7075 7076 7077
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7078

7079
	if (tsk_cache_hot <= 0 ||
7080
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7081
		if (tsk_cache_hot == 1) {
7082 7083
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7084
		}
7085 7086 7087
		return 1;
	}

7088
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7089
	return 0;
7090 7091
}

7092
/*
7093 7094 7095 7096 7097 7098 7099
 * 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;
7100
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7101 7102 7103
	set_task_cpu(p, env->dst_cpu);
}

7104
/*
7105
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7106 7107
 * part of active balancing operations within "domain".
 *
7108
 * Returns a task if successful and NULL otherwise.
7109
 */
7110
static struct task_struct *detach_one_task(struct lb_env *env)
7111
{
7112
	struct task_struct *p;
7113

7114 7115
	lockdep_assert_held(&env->src_rq->lock);

7116 7117
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7118 7119
		if (!can_migrate_task(p, env))
			continue;
7120

7121
		detach_task(p, env);
7122

7123
		/*
7124
		 * Right now, this is only the second place where
7125
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7126
		 * so we can safely collect stats here rather than
7127
		 * inside detach_tasks().
7128
		 */
7129
		schedstat_inc(env->sd->lb_gained[env->idle]);
7130
		return p;
7131
	}
7132
	return NULL;
7133 7134
}

7135 7136
static const unsigned int sched_nr_migrate_break = 32;

7137
/*
7138 7139
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7140
 *
7141
 * Returns number of detached tasks if successful and 0 otherwise.
7142
 */
7143
static int detach_tasks(struct lb_env *env)
7144
{
7145 7146
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7147
	unsigned long load;
7148 7149 7150
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7151

7152
	if (env->imbalance <= 0)
7153
		return 0;
7154

7155
	while (!list_empty(tasks)) {
7156 7157 7158 7159 7160 7161 7162
		/*
		 * 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;

7163
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7164

7165 7166
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7167
		if (env->loop > env->loop_max)
7168
			break;
7169 7170

		/* take a breather every nr_migrate tasks */
7171
		if (env->loop > env->loop_break) {
7172
			env->loop_break += sched_nr_migrate_break;
7173
			env->flags |= LBF_NEED_BREAK;
7174
			break;
7175
		}
7176

7177
		if (!can_migrate_task(p, env))
7178 7179 7180
			goto next;

		load = task_h_load(p);
7181

7182
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7183 7184
			goto next;

7185
		if ((load / 2) > env->imbalance)
7186
			goto next;
7187

7188 7189 7190 7191
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7192
		env->imbalance -= load;
7193 7194

#ifdef CONFIG_PREEMPT
7195 7196
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7197
		 * kernels will stop after the first task is detached to minimize
7198 7199
		 * the critical section.
		 */
7200
		if (env->idle == CPU_NEWLY_IDLE)
7201
			break;
7202 7203
#endif

7204 7205 7206 7207
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7208
		if (env->imbalance <= 0)
7209
			break;
7210 7211 7212

		continue;
next:
7213
		list_move(&p->se.group_node, tasks);
7214
	}
7215

7216
	/*
7217 7218 7219
	 * 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().
7220
	 */
7221
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7222

7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233
	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);
7234
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7235
	p->on_rq = TASK_ON_RQ_QUEUED;
7236 7237 7238 7239 7240 7241 7242 7243 7244
	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)
{
7245 7246 7247
	struct rq_flags rf;

	rq_lock(rq, &rf);
7248
	update_rq_clock(rq);
7249
	attach_task(rq, p);
7250
	rq_unlock(rq, &rf);
7251 7252 7253 7254 7255 7256 7257 7258 7259 7260
}

/*
 * 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;
7261
	struct rq_flags rf;
7262

7263
	rq_lock(env->dst_rq, &rf);
7264
	update_rq_clock(env->dst_rq);
7265 7266 7267 7268

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7269

7270 7271 7272
		attach_task(env->dst_rq, p);
	}

7273
	rq_unlock(env->dst_rq, &rf);
7274 7275
}

P
Peter Zijlstra 已提交
7276
#ifdef CONFIG_FAIR_GROUP_SCHED
7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288

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;

7289
	if (cfs_rq->avg.runnable_load_sum)
7290 7291 7292 7293 7294
		return false;

	return true;
}

7295
static void update_blocked_averages(int cpu)
7296 7297
{
	struct rq *rq = cpu_rq(cpu);
7298
	struct cfs_rq *cfs_rq, *pos;
7299
	struct rq_flags rf;
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
	rq_unlock_irqrestore(rq, &rf);
7331 7332
}

7333
/*
7334
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7335 7336 7337
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7338
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7339
{
7340 7341
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7342
	unsigned long now = jiffies;
7343
	unsigned long load;
7344

7345
	if (cfs_rq->last_h_load_update == now)
7346 7347
		return;

7348 7349 7350 7351 7352 7353 7354
	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;
	}
7355

7356
	if (!se) {
7357
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7358 7359 7360 7361 7362
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
7363 7364
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7365 7366 7367 7368
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7369 7370
}

7371
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7372
{
7373
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7374

7375
	update_cfs_rq_h_load(cfs_rq);
7376
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7377
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7378 7379
}
#else
7380
static inline void update_blocked_averages(int cpu)
7381
{
7382 7383
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7384
	struct rq_flags rf;
7385

7386
	rq_lock_irqsave(rq, &rf);
7387
	update_rq_clock(rq);
7388
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7389
	rq_unlock_irqrestore(rq, &rf);
7390 7391
}

7392
static unsigned long task_h_load(struct task_struct *p)
7393
{
7394
	return p->se.avg.load_avg;
7395
}
P
Peter Zijlstra 已提交
7396
#endif
7397 7398

/********** Helpers for find_busiest_group ************************/
7399 7400 7401 7402 7403 7404 7405

enum group_type {
	group_other = 0,
	group_imbalanced,
	group_overloaded,
};

7406 7407 7408 7409 7410 7411 7412
/*
 * 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
7413
	unsigned long load_per_task;
7414
	unsigned long group_capacity;
7415
	unsigned long group_util; /* Total utilization of the group */
7416 7417 7418
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7419
	enum group_type group_type;
7420
	int group_no_capacity;
7421 7422 7423 7424
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7425 7426
};

J
Joonsoo Kim 已提交
7427 7428 7429 7430 7431 7432 7433
/*
 * 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 */
7434
	unsigned long total_running;
J
Joonsoo Kim 已提交
7435
	unsigned long total_load;	/* Total load of all groups in sd */
7436
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7437 7438 7439
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7440
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7441 7442
};

7443 7444 7445 7446 7447 7448 7449 7450 7451 7452 7453
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,
7454
		.total_running = 0UL,
7455
		.total_load = 0UL,
7456
		.total_capacity = 0UL,
7457 7458
		.busiest_stat = {
			.avg_load = 0UL,
7459 7460
			.sum_nr_running = 0,
			.group_type = group_other,
7461 7462 7463 7464
		},
	};
}

7465 7466 7467
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7468
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7469 7470
 *
 * Return: The load index.
7471 7472 7473 7474 7475 7476 7477 7478 7479 7480 7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492
 */
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;
}

7493
static unsigned long scale_rt_capacity(int cpu)
7494 7495
{
	struct rq *rq = cpu_rq(cpu);
7496
	u64 total, used, age_stamp, avg;
7497
	s64 delta;
7498

7499 7500 7501 7502
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
7503 7504
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
7505
	delta = __rq_clock_broken(rq) - age_stamp;
7506

7507 7508 7509 7510
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
7511

7512
	used = div_u64(avg, total);
7513

7514 7515
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
7516

7517
	return 1;
7518 7519
}

7520
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7521
{
7522
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7523 7524
	struct sched_group *sdg = sd->groups;

7525
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7526

7527
	capacity *= scale_rt_capacity(cpu);
7528
	capacity >>= SCHED_CAPACITY_SHIFT;
7529

7530 7531
	if (!capacity)
		capacity = 1;
7532

7533 7534
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7535
	sdg->sgc->min_capacity = capacity;
7536 7537
}

7538
void update_group_capacity(struct sched_domain *sd, int cpu)
7539 7540 7541
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7542
	unsigned long capacity, min_capacity;
7543 7544 7545 7546
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7547
	sdg->sgc->next_update = jiffies + interval;
7548 7549

	if (!child) {
7550
		update_cpu_capacity(sd, cpu);
7551 7552 7553
		return;
	}

7554
	capacity = 0;
7555
	min_capacity = ULONG_MAX;
7556

P
Peter Zijlstra 已提交
7557 7558 7559 7560 7561 7562
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7563
		for_each_cpu(cpu, sched_group_span(sdg)) {
7564
			struct sched_group_capacity *sgc;
7565
			struct rq *rq = cpu_rq(cpu);
7566

7567
			/*
7568
			 * build_sched_domains() -> init_sched_groups_capacity()
7569 7570 7571
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7572 7573
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7574
			 *
7575
			 * This avoids capacity from being 0 and
7576 7577 7578
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7579
				capacity += capacity_of(cpu);
7580 7581 7582
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7583
			}
7584

7585
			min_capacity = min(capacity, min_capacity);
7586
		}
P
Peter Zijlstra 已提交
7587 7588 7589 7590
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7591
		 */
P
Peter Zijlstra 已提交
7592 7593 7594

		group = child->groups;
		do {
7595 7596 7597 7598
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7599 7600 7601
			group = group->next;
		} while (group != child->groups);
	}
7602

7603
	sdg->sgc->capacity = capacity;
7604
	sdg->sgc->min_capacity = min_capacity;
7605 7606
}

7607
/*
7608 7609 7610
 * 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
7611 7612
 */
static inline int
7613
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7614
{
7615 7616
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7617 7618
}

7619 7620
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7621
 * groups is inadequate due to ->cpus_allowed constraints.
7622 7623 7624 7625 7626
 *
 * 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.
 * Something like:
 *
7627 7628
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7629 7630 7631 7632 7633 7634
 *
 * 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
 * cpu 3 and leave one of the cpus in the second group unused.
 *
 * The current solution to this issue is detecting the skew in the first group
7635 7636
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7637 7638
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7639
 * update_sd_pick_busiest(). And calculate_imbalance() and
7640
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7641 7642 7643 7644 7645 7646 7647
 * 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.
 */

7648
static inline int sg_imbalanced(struct sched_group *group)
7649
{
7650
	return group->sgc->imbalance;
7651 7652
}

7653
/*
7654 7655 7656
 * 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
7657 7658
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7659 7660 7661 7662 7663
 * 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.
7664
 */
7665 7666
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7667
{
7668 7669
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7670

7671
	if ((sgs->group_capacity * 100) >
7672
			(sgs->group_util * env->sd->imbalance_pct))
7673
		return true;
7674

7675 7676 7677 7678 7679 7680 7681 7682 7683 7684 7685 7686 7687 7688 7689 7690
	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;
7691

7692
	if ((sgs->group_capacity * 100) <
7693
			(sgs->group_util * env->sd->imbalance_pct))
7694
		return true;
7695

7696
	return false;
7697 7698
}

7699 7700 7701 7702 7703 7704 7705 7706 7707 7708 7709
/*
 * 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;
}

7710 7711 7712
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7713
{
7714
	if (sgs->group_no_capacity)
7715 7716 7717 7718 7719 7720 7721 7722
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7723 7724
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7725
 * @env: The load balancing environment.
7726 7727 7728 7729
 * @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.
7730
 * @overload: Indicate more than one runnable task for any CPU.
7731
 */
7732 7733
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7734 7735
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7736
{
7737
	unsigned long load;
7738
	int i, nr_running;
7739

7740 7741
	memset(sgs, 0, sizeof(*sgs));

7742
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7743 7744 7745
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
7746
		if (local_group)
7747
			load = target_load(i, load_idx);
7748
		else
7749 7750 7751
			load = source_load(i, load_idx);

		sgs->group_load += load;
7752
		sgs->group_util += cpu_util(i);
7753
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7754

7755 7756
		nr_running = rq->nr_running;
		if (nr_running > 1)
7757 7758
			*overload = true;

7759 7760 7761 7762
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7763
		sgs->sum_weighted_load += weighted_cpuload(rq);
7764 7765 7766 7767
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7768
			sgs->idle_cpus++;
7769 7770
	}

7771 7772
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7773
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7774

7775
	if (sgs->sum_nr_running)
7776
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7777

7778
	sgs->group_weight = group->group_weight;
7779

7780
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7781
	sgs->group_type = group_classify(group, sgs);
7782 7783
}

7784 7785
/**
 * update_sd_pick_busiest - return 1 on busiest group
7786
 * @env: The load balancing environment.
7787 7788
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7789
 * @sgs: sched_group statistics
7790 7791 7792
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7793 7794 7795
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7796
 */
7797
static bool update_sd_pick_busiest(struct lb_env *env,
7798 7799
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7800
				   struct sg_lb_stats *sgs)
7801
{
7802
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7803

7804
	if (sgs->group_type > busiest->group_type)
7805 7806
		return true;

7807 7808 7809 7810 7811 7812
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

7813 7814 7815 7816 7817 7818 7819 7820 7821 7822 7823 7824 7825 7826
	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:
7827 7828
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7829 7830
		return true;

7831 7832 7833
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
7834
	/*
T
Tim Chen 已提交
7835 7836 7837
	 * 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.
7838
	 */
T
Tim Chen 已提交
7839 7840
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7841 7842 7843
		if (!sds->busiest)
			return true;

T
Tim Chen 已提交
7844 7845 7846
		/* Prefer to move from lowest priority cpu's work */
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7847 7848 7849 7850 7851 7852
			return true;
	}

	return false;
}

7853 7854 7855 7856 7857 7858 7859 7860 7861 7862 7863 7864 7865 7866 7867 7868 7869 7870 7871 7872 7873 7874 7875 7876 7877 7878 7879 7880 7881 7882
#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 */

7883
/**
7884
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7885
 * @env: The load balancing environment.
7886 7887
 * @sds: variable to hold the statistics for this sched_domain.
 */
7888
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7889
{
7890 7891
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7892
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7893
	struct sg_lb_stats tmp_sgs;
7894
	int load_idx, prefer_sibling = 0;
7895
	bool overload = false;
7896 7897 7898 7899

	if (child && child->flags & SD_PREFER_SIBLING)
		prefer_sibling = 1;

7900
	load_idx = get_sd_load_idx(env->sd, env->idle);
7901 7902

	do {
J
Joonsoo Kim 已提交
7903
		struct sg_lb_stats *sgs = &tmp_sgs;
7904 7905
		int local_group;

7906
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7907 7908
		if (local_group) {
			sds->local = sg;
7909
			sgs = local;
7910 7911

			if (env->idle != CPU_NEWLY_IDLE ||
7912 7913
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7914
		}
7915

7916 7917
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7918

7919 7920 7921
		if (local_group)
			goto next_group;

7922 7923
		/*
		 * In case the child domain prefers tasks go to siblings
7924
		 * first, lower the sg capacity so that we'll try
7925 7926
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7927 7928 7929 7930
		 * 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).
7931
		 */
7932
		if (prefer_sibling && sds->local &&
7933 7934
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7935
			sgs->group_no_capacity = 1;
7936
			sgs->group_type = group_classify(sg, sgs);
7937
		}
7938

7939
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7940
			sds->busiest = sg;
J
Joonsoo Kim 已提交
7941
			sds->busiest_stat = *sgs;
7942 7943
		}

7944 7945
next_group:
		/* Now, start updating sd_lb_stats */
7946
		sds->total_running += sgs->sum_nr_running;
7947
		sds->total_load += sgs->group_load;
7948
		sds->total_capacity += sgs->group_capacity;
7949

7950
		sg = sg->next;
7951
	} while (sg != env->sd->groups);
7952 7953 7954

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7955 7956 7957 7958 7959 7960

	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;
	}
7961 7962 7963 7964
}

/**
 * check_asym_packing - Check to see if the group is packed into the
7965
 *			sched domain.
7966 7967 7968 7969 7970 7971 7972 7973 7974 7975 7976 7977 7978 7979
 *
 * 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.
 *
7980
 * Return: 1 when packing is required and a task should be moved to
7981
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
7982
 *
7983
 * @env: The load balancing environment.
7984 7985
 * @sds: Statistics of the sched_domain which is to be packed
 */
7986
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7987 7988 7989
{
	int busiest_cpu;

7990
	if (!(env->sd->flags & SD_ASYM_PACKING))
7991 7992
		return 0;

7993 7994 7995
	if (env->idle == CPU_NOT_IDLE)
		return 0;

7996 7997 7998
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
7999 8000
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8001 8002
		return 0;

8003
	env->imbalance = DIV_ROUND_CLOSEST(
8004
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8005
		SCHED_CAPACITY_SCALE);
8006

8007
	return 1;
8008 8009 8010 8011 8012 8013
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8014
 * @env: The load balancing environment.
8015 8016
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8017 8018
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8019
{
8020
	unsigned long tmp, capa_now = 0, capa_move = 0;
8021
	unsigned int imbn = 2;
8022
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8023
	struct sg_lb_stats *local, *busiest;
8024

J
Joonsoo Kim 已提交
8025 8026
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8027

J
Joonsoo Kim 已提交
8028 8029 8030 8031
	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;
8032

J
Joonsoo Kim 已提交
8033
	scaled_busy_load_per_task =
8034
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8035
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8036

8037 8038
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8039
		env->imbalance = busiest->load_per_task;
8040 8041 8042 8043 8044
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8045
	 * however we may be able to increase total CPU capacity used by
8046 8047 8048
	 * moving them.
	 */

8049
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8050
			min(busiest->load_per_task, busiest->avg_load);
8051
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8052
			min(local->load_per_task, local->avg_load);
8053
	capa_now /= SCHED_CAPACITY_SCALE;
8054 8055

	/* Amount of load we'd subtract */
8056
	if (busiest->avg_load > scaled_busy_load_per_task) {
8057
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8058
			    min(busiest->load_per_task,
8059
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8060
	}
8061 8062

	/* Amount of load we'd add */
8063
	if (busiest->avg_load * busiest->group_capacity <
8064
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8065 8066
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8067
	} else {
8068
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8069
		      local->group_capacity;
J
Joonsoo Kim 已提交
8070
	}
8071
	capa_move += local->group_capacity *
8072
		    min(local->load_per_task, local->avg_load + tmp);
8073
	capa_move /= SCHED_CAPACITY_SCALE;
8074 8075

	/* Move if we gain throughput */
8076
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8077
		env->imbalance = busiest->load_per_task;
8078 8079 8080 8081 8082
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8083
 * @env: load balance environment
8084 8085
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8086
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8087
{
8088
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8089 8090 8091 8092
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8093

8094
	if (busiest->group_type == group_imbalanced) {
8095 8096 8097 8098
		/*
		 * In the group_imb case we cannot rely on group-wide averages
		 * to ensure cpu-load equilibrium, look at wider averages. XXX
		 */
J
Joonsoo Kim 已提交
8099 8100
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8101 8102
	}

8103
	/*
8104 8105 8106 8107
	 * 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:
8108
	 */
8109 8110
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8111 8112
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8113 8114
	}

8115 8116 8117 8118 8119
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8120
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8121
		if (load_above_capacity > busiest->group_capacity) {
8122
			load_above_capacity -= busiest->group_capacity;
8123
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8124 8125
			load_above_capacity /= busiest->group_capacity;
		} else
8126
			load_above_capacity = ~0UL;
8127 8128 8129 8130 8131 8132
	}

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
8133 8134
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8135
	 */
8136
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8137 8138

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8139
	env->imbalance = min(
8140 8141
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8142
	) / SCHED_CAPACITY_SCALE;
8143 8144 8145

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8146
	 * there is no guarantee that any tasks will be moved so we'll have
8147 8148 8149
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8150
	if (env->imbalance < busiest->load_per_task)
8151
		return fix_small_imbalance(env, sds);
8152
}
8153

8154 8155 8156 8157
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8158
 * if there is an imbalance.
8159 8160 8161 8162
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8163
 * @env: The load balancing environment.
8164
 *
8165
 * Return:	- The busiest group if imbalance exists.
8166
 */
J
Joonsoo Kim 已提交
8167
static struct sched_group *find_busiest_group(struct lb_env *env)
8168
{
J
Joonsoo Kim 已提交
8169
	struct sg_lb_stats *local, *busiest;
8170 8171
	struct sd_lb_stats sds;

8172
	init_sd_lb_stats(&sds);
8173 8174 8175 8176 8177

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8178
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8179 8180
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8181

8182
	/* ASYM feature bypasses nice load balance check */
8183
	if (check_asym_packing(env, &sds))
8184 8185
		return sds.busiest;

8186
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8187
	if (!sds.busiest || busiest->sum_nr_running == 0)
8188 8189
		goto out_balanced;

8190
	/* XXX broken for overlapping NUMA groups */
8191 8192
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8193

P
Peter Zijlstra 已提交
8194 8195
	/*
	 * If the busiest group is imbalanced the below checks don't
8196
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8197 8198
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8199
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8200 8201
		goto force_balance;

8202 8203 8204 8205 8206
	/*
	 * 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) &&
8207
	    busiest->group_no_capacity)
8208 8209
		goto force_balance;

8210
	/*
8211
	 * If the local group is busier than the selected busiest group
8212 8213
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8214
	if (local->avg_load >= busiest->avg_load)
8215 8216
		goto out_balanced;

8217 8218 8219 8220
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8221
	if (local->avg_load >= sds.avg_load)
8222 8223
		goto out_balanced;

8224
	if (env->idle == CPU_IDLE) {
8225
		/*
8226 8227 8228 8229 8230
		 * This cpu is idle. If the busiest group is not overloaded
		 * and there is no imbalance between this and busiest group
		 * wrt idle cpus, it is balanced. The imbalance becomes
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8231
		 */
8232 8233
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8234
			goto out_balanced;
8235 8236 8237 8238 8239
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8240 8241
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8242
			goto out_balanced;
8243
	}
8244

8245
force_balance:
8246
	/* Looks like there is an imbalance. Compute it */
8247
	calculate_imbalance(env, &sds);
8248 8249 8250
	return sds.busiest;

out_balanced:
8251
	env->imbalance = 0;
8252 8253 8254 8255 8256 8257
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
8258
static struct rq *find_busiest_queue(struct lb_env *env,
8259
				     struct sched_group *group)
8260 8261
{
	struct rq *busiest = NULL, *rq;
8262
	unsigned long busiest_load = 0, busiest_capacity = 1;
8263 8264
	int i;

8265
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8266
		unsigned long capacity, wl;
8267 8268 8269 8270
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8271

8272 8273 8274 8275 8276 8277 8278 8279 8280 8281 8282 8283 8284 8285 8286 8287 8288 8289 8290 8291 8292 8293
		/*
		 * 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;

8294
		capacity = capacity_of(i);
8295

8296
		wl = weighted_cpuload(rq);
8297

8298 8299
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8300
		 * which is not scaled with the cpu capacity.
8301
		 */
8302 8303 8304

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8305 8306
			continue;

8307 8308
		/*
		 * For the load comparisons with the other cpu's, consider
8309 8310 8311
		 * the weighted_cpuload() scaled with the cpu capacity, so
		 * that the load can be moved away from the cpu that is
		 * potentially running at a lower capacity.
8312
		 *
8313
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8314
		 * multiplication to rid ourselves of the division works out
8315 8316
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8317
		 */
8318
		if (wl * busiest_capacity > busiest_load * capacity) {
8319
			busiest_load = wl;
8320
			busiest_capacity = capacity;
8321 8322 8323 8324 8325 8326 8327 8328 8329 8330 8331 8332 8333
			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

8334
static int need_active_balance(struct lb_env *env)
8335
{
8336 8337 8338
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8339 8340 8341

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8342 8343
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8344
		 */
T
Tim Chen 已提交
8345 8346
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8347
			return 1;
8348 8349
	}

8350 8351 8352 8353 8354 8355 8356 8357 8358 8359 8360 8361 8362
	/*
	 * 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;
	}

8363 8364 8365
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8366 8367
static int active_load_balance_cpu_stop(void *data);

8368 8369 8370 8371 8372
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8373 8374 8375 8376 8377 8378 8379
	/*
	 * 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;

8380 8381 8382 8383 8384 8385 8386 8387
	/*
	 * In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

	/* Try to find first idle cpu */
8388
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8389
		if (!idle_cpu(cpu))
8390 8391 8392 8393 8394 8395 8396 8397 8398 8399 8400 8401 8402
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above domains.
	 */
8403
	return balance_cpu == env->dst_cpu;
8404 8405
}

8406 8407 8408 8409 8410 8411
/*
 * 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,
8412
			int *continue_balancing)
8413
{
8414
	int ld_moved, cur_ld_moved, active_balance = 0;
8415
	struct sched_domain *sd_parent = sd->parent;
8416 8417
	struct sched_group *group;
	struct rq *busiest;
8418
	struct rq_flags rf;
8419
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8420

8421 8422
	struct lb_env env = {
		.sd		= sd,
8423 8424
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8425
		.dst_grpmask    = sched_group_span(sd->groups),
8426
		.idle		= idle,
8427
		.loop_break	= sched_nr_migrate_break,
8428
		.cpus		= cpus,
8429
		.fbq_type	= all,
8430
		.tasks		= LIST_HEAD_INIT(env.tasks),
8431 8432
	};

8433
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8434

8435
	schedstat_inc(sd->lb_count[idle]);
8436 8437

redo:
8438 8439
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8440
		goto out_balanced;
8441
	}
8442

8443
	group = find_busiest_group(&env);
8444
	if (!group) {
8445
		schedstat_inc(sd->lb_nobusyg[idle]);
8446 8447 8448
		goto out_balanced;
	}

8449
	busiest = find_busiest_queue(&env, group);
8450
	if (!busiest) {
8451
		schedstat_inc(sd->lb_nobusyq[idle]);
8452 8453 8454
		goto out_balanced;
	}

8455
	BUG_ON(busiest == env.dst_rq);
8456

8457
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8458

8459 8460 8461
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8462 8463 8464 8465 8466 8467 8468 8469
	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.
		 */
8470
		env.flags |= LBF_ALL_PINNED;
8471
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8472

8473
more_balance:
8474
		rq_lock_irqsave(busiest, &rf);
8475
		update_rq_clock(busiest);
8476 8477 8478 8479 8480

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8481
		cur_ld_moved = detach_tasks(&env);
8482 8483

		/*
8484 8485 8486 8487 8488
		 * 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.
8489
		 */
8490

8491
		rq_unlock(busiest, &rf);
8492 8493 8494 8495 8496 8497

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8498
		local_irq_restore(rf.flags);
8499

8500 8501 8502 8503 8504
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8505 8506 8507 8508 8509 8510 8511 8512 8513 8514 8515 8516 8517 8518 8519 8520 8521 8522 8523
		/*
		 * 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
		 * iterate on same src_cpu is dependent on number of cpus in our
		 * 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.
		 */
8524
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8525

8526 8527 8528
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8529
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8530
			env.dst_cpu	 = env.new_dst_cpu;
8531
			env.flags	&= ~LBF_DST_PINNED;
8532 8533
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8534

8535 8536 8537 8538 8539 8540
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8541

8542 8543 8544 8545
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8546
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8547

8548
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8549 8550 8551
				*group_imbalance = 1;
		}

8552
		/* All tasks on this runqueue were pinned by CPU affinity */
8553
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8554
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8555 8556 8557 8558 8559 8560 8561 8562 8563
			/*
			 * 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)) {
8564 8565
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8566
				goto redo;
8567
			}
8568
			goto out_all_pinned;
8569 8570 8571 8572
		}
	}

	if (!ld_moved) {
8573
		schedstat_inc(sd->lb_failed[idle]);
8574 8575 8576 8577 8578 8579 8580 8581
		/*
		 * 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++;
8582

8583
		if (need_active_balance(&env)) {
8584 8585
			unsigned long flags;

8586 8587
			raw_spin_lock_irqsave(&busiest->lock, flags);

8588 8589 8590
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
8591
			 */
8592
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8593 8594
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8595
				env.flags |= LBF_ALL_PINNED;
8596 8597 8598
				goto out_one_pinned;
			}

8599 8600 8601 8602 8603
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8604 8605 8606 8607 8608 8609
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8610

8611
			if (active_balance) {
8612 8613 8614
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8615
			}
8616

8617
			/* We've kicked active balancing, force task migration. */
8618 8619 8620 8621 8622 8623 8624 8625 8626 8627 8628 8629 8630
			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
8631
		 * detach_tasks).
8632 8633 8634 8635 8636 8637 8638 8639
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8640 8641 8642 8643 8644 8645 8646 8647 8648 8649 8650 8651 8652 8653 8654 8655 8656
	/*
	 * 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.
	 */
8657
	schedstat_inc(sd->lb_balanced[idle]);
8658 8659 8660 8661 8662

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8663
	if (((env.flags & LBF_ALL_PINNED) &&
8664
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8665 8666 8667
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8668
	ld_moved = 0;
8669 8670 8671 8672
out:
	return ld_moved;
}

8673 8674 8675 8676 8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687 8688
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
8689
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8690 8691 8692
{
	unsigned long interval, next;

8693 8694
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8695 8696 8697 8698 8699 8700
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8701 8702 8703 8704
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
8705
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
8706
{
8707 8708
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
8709 8710
	struct sched_domain *sd;
	int pulled_task = 0;
8711
	u64 curr_cost = 0;
8712

8713 8714 8715 8716 8717 8718
	/*
	 * 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);

8719 8720 8721 8722 8723 8724
	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

8725 8726 8727 8728 8729 8730 8731 8732
	/*
	 * 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);

8733 8734
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
8735 8736 8737
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
8738
			update_next_balance(sd, &next_balance);
8739 8740
		rcu_read_unlock();

8741
		goto out;
8742
	}
8743

8744 8745
	raw_spin_unlock(&this_rq->lock);

8746
	update_blocked_averages(this_cpu);
8747
	rcu_read_lock();
8748
	for_each_domain(this_cpu, sd) {
8749
		int continue_balancing = 1;
8750
		u64 t0, domain_cost;
8751 8752 8753 8754

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8755
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8756
			update_next_balance(sd, &next_balance);
8757
			break;
8758
		}
8759

8760
		if (sd->flags & SD_BALANCE_NEWIDLE) {
8761 8762
			t0 = sched_clock_cpu(this_cpu);

8763
			pulled_task = load_balance(this_cpu, this_rq,
8764 8765
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
8766 8767 8768 8769 8770 8771

			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;
8772
		}
8773

8774
		update_next_balance(sd, &next_balance);
8775 8776 8777 8778 8779 8780

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
8781 8782
			break;
	}
8783
	rcu_read_unlock();
8784 8785 8786

	raw_spin_lock(&this_rq->lock);

8787 8788 8789
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

8790
	/*
8791 8792 8793
	 * 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.
8794
	 */
8795
	if (this_rq->cfs.h_nr_running && !pulled_task)
8796
		pulled_task = 1;
8797

8798 8799 8800
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
8801
		this_rq->next_balance = next_balance;
8802

8803
	/* Is there a task of a high priority class? */
8804
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8805 8806
		pulled_task = -1;

8807
	if (pulled_task)
8808 8809
		this_rq->idle_stamp = 0;

8810 8811
	rq_repin_lock(this_rq, rf);

8812
	return pulled_task;
8813 8814 8815
}

/*
8816 8817 8818 8819
 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
 * 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.
8820
 */
8821
static int active_load_balance_cpu_stop(void *data)
8822
{
8823 8824
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8825
	int target_cpu = busiest_rq->push_cpu;
8826
	struct rq *target_rq = cpu_rq(target_cpu);
8827
	struct sched_domain *sd;
8828
	struct task_struct *p = NULL;
8829
	struct rq_flags rf;
8830

8831
	rq_lock_irq(busiest_rq, &rf);
8832 8833 8834 8835 8836 8837 8838
	/*
	 * 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;
8839 8840 8841 8842 8843

	/* make sure the requested cpu hasn't gone down in the meantime */
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
8844 8845 8846

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8847
		goto out_unlock;
8848 8849 8850 8851 8852 8853 8854 8855 8856

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
	 * Bjorn Helgaas on a 128-cpu setup.
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
8857
	rcu_read_lock();
8858 8859 8860 8861 8862 8863 8864
	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)) {
8865 8866
		struct lb_env env = {
			.sd		= sd,
8867 8868 8869 8870
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8871
			.idle		= CPU_IDLE,
8872 8873 8874 8875 8876 8877 8878
			/*
			 * 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,
8879 8880
		};

8881
		schedstat_inc(sd->alb_count);
8882
		update_rq_clock(busiest_rq);
8883

8884
		p = detach_one_task(&env);
8885
		if (p) {
8886
			schedstat_inc(sd->alb_pushed);
8887 8888 8889
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8890
			schedstat_inc(sd->alb_failed);
8891
		}
8892
	}
8893
	rcu_read_unlock();
8894 8895
out_unlock:
	busiest_rq->active_balance = 0;
8896
	rq_unlock(busiest_rq, &rf);
8897 8898 8899 8900 8901 8902

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8903
	return 0;
8904 8905
}

8906 8907 8908 8909 8910
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8911
#ifdef CONFIG_NO_HZ_COMMON
8912 8913 8914 8915 8916 8917
/*
 * 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.
 */
8918
static struct {
8919
	cpumask_var_t idle_cpus_mask;
8920
	atomic_t nr_cpus;
8921 8922
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
8923

8924
static inline int find_new_ilb(void)
8925
{
8926
	int ilb = cpumask_first(nohz.idle_cpus_mask);
8927

8928 8929 8930 8931
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
8932 8933
}

8934 8935 8936 8937 8938
/*
 * 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).
 */
8939
static void nohz_balancer_kick(void)
8940 8941 8942 8943 8944
{
	int ilb_cpu;

	nohz.next_balance++;

8945
	ilb_cpu = find_new_ilb();
8946

8947 8948
	if (ilb_cpu >= nr_cpu_ids)
		return;
8949

8950
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8951 8952 8953 8954 8955 8956 8957 8958
		return;
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
	 * This way we generate a sched IPI on the target cpu which
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
8959 8960 8961
	return;
}

8962
void nohz_balance_exit_idle(unsigned int cpu)
8963 8964
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8965 8966 8967 8968 8969 8970 8971
		/*
		 * Completely isolated CPUs don't ever set, so we must test.
		 */
		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
			atomic_dec(&nohz.nr_cpus);
		}
8972 8973 8974 8975
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

8976 8977 8978
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
8979
	int cpu = smp_processor_id();
8980 8981

	rcu_read_lock();
8982
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8983 8984 8985 8986 8987

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

8988
	atomic_inc(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8989
unlock:
8990 8991 8992 8993 8994 8995
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
8996
	int cpu = smp_processor_id();
8997 8998

	rcu_read_lock();
8999
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9000 9001 9002 9003 9004

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

9005
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9006
unlock:
9007 9008 9009
	rcu_read_unlock();
}

9010
/*
9011
 * This routine will record that the cpu is going idle with tick stopped.
9012
 * This info will be used in performing idle load balancing in the future.
9013
 */
9014
void nohz_balance_enter_idle(int cpu)
9015
{
9016 9017 9018 9019 9020 9021
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

9022 9023 9024 9025
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
	if (!is_housekeeping_cpu(cpu))
		return;

9026 9027
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
9028

9029 9030 9031 9032 9033 9034
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

9035 9036 9037
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
9038 9039 9040 9041 9042
}
#endif

static DEFINE_SPINLOCK(balancing);

9043 9044 9045 9046
/*
 * 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.
 */
9047
void update_max_interval(void)
9048 9049 9050 9051
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

9052 9053 9054 9055
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
9056
 * Balancing parameters are set up in init_sched_domains.
9057
 */
9058
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
9059
{
9060
	int continue_balancing = 1;
9061
	int cpu = rq->cpu;
9062
	unsigned long interval;
9063
	struct sched_domain *sd;
9064 9065 9066
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
9067 9068
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
9069

9070
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
9071

9072
	rcu_read_lock();
9073
	for_each_domain(cpu, sd) {
9074 9075 9076 9077 9078 9079 9080 9081 9082 9083 9084 9085
		/*
		 * 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;

9086 9087 9088
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

9089 9090 9091 9092 9093 9094 9095 9096 9097 9098 9099
		/*
		 * 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;
		}

9100
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9101 9102 9103 9104 9105 9106 9107 9108

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
9109
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
9110
				/*
9111
				 * The LBF_DST_PINNED logic could have changed
9112 9113
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
9114
				 */
9115
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
9116 9117
			}
			sd->last_balance = jiffies;
9118
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9119 9120 9121 9122 9123 9124 9125 9126
		}
		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;
		}
9127 9128
	}
	if (need_decay) {
9129
		/*
9130 9131
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
9132
		 */
9133 9134
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
9135
	}
9136
	rcu_read_unlock();
9137 9138 9139 9140 9141 9142

	/*
	 * 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.
	 */
9143
	if (likely(update_next_balance)) {
9144
		rq->next_balance = next_balance;
9145 9146 9147 9148 9149 9150 9151 9152 9153 9154 9155 9156 9157 9158

#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
	}
9159 9160
}

9161
#ifdef CONFIG_NO_HZ_COMMON
9162
/*
9163
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
9164 9165
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
9166
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
9167
{
9168
	int this_cpu = this_rq->cpu;
9169 9170
	struct rq *rq;
	int balance_cpu;
9171 9172 9173
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
9174

9175 9176 9177
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
9178 9179

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9180
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9181 9182 9183 9184 9185 9186 9187
			continue;

		/*
		 * If this cpu gets work to do, stop the load balancing
		 * work being done for other cpus. Next load
		 * balancing owner will pick it up.
		 */
9188
		if (need_resched())
9189 9190
			break;

V
Vincent Guittot 已提交
9191 9192
		rq = cpu_rq(balance_cpu);

9193 9194 9195 9196 9197
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9198 9199 9200
			struct rq_flags rf;

			rq_lock_irq(rq, &rf);
9201
			update_rq_clock(rq);
9202
			cpu_load_update_idle(rq);
9203 9204
			rq_unlock_irq(rq, &rf);

9205 9206
			rebalance_domains(rq, CPU_IDLE);
		}
9207

9208 9209 9210 9211
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9212
	}
9213 9214 9215 9216 9217 9218 9219 9220

	/*
	 * 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;
9221 9222
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
9223 9224 9225
}

/*
9226
 * Current heuristic for kicking the idle load balancer in the presence
9227
 * of an idle cpu in the system.
9228
 *   - This rq has more than one task.
9229 9230 9231 9232
 *   - 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.
9233 9234
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
9235
 */
9236
static inline bool nohz_kick_needed(struct rq *rq)
9237 9238
{
	unsigned long now = jiffies;
9239
	struct sched_domain_shared *sds;
9240
	struct sched_domain *sd;
T
Tim Chen 已提交
9241
	int nr_busy, i, cpu = rq->cpu;
9242
	bool kick = false;
9243

9244
	if (unlikely(rq->idle_balance))
9245
		return false;
9246

9247 9248 9249 9250
       /*
	* 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.
	*/
9251
	set_cpu_sd_state_busy();
9252
	nohz_balance_exit_idle(cpu);
9253 9254 9255 9256 9257 9258

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
9259
		return false;
9260 9261

	if (time_before(now, nohz.next_balance))
9262
		return false;
9263

9264
	if (rq->nr_running >= 2)
9265
		return true;
9266

9267
	rcu_read_lock();
9268 9269 9270 9271 9272 9273 9274
	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);
9275 9276 9277 9278 9279
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

9280
	}
9281

9282 9283 9284 9285 9286 9287 9288 9289
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
9290

9291
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
T
Tim Chen 已提交
9292 9293 9294 9295 9296
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;
9297

T
Tim Chen 已提交
9298 9299 9300 9301 9302 9303
			if (sched_asym_prefer(i, cpu)) {
				kick = true;
				goto unlock;
			}
		}
	}
9304
unlock:
9305
	rcu_read_unlock();
9306
	return kick;
9307 9308
}
#else
9309
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
9310 9311 9312 9313 9314 9315
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9316
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9317
{
9318
	struct rq *this_rq = this_rq();
9319
	enum cpu_idle_type idle = this_rq->idle_balance ?
9320 9321 9322
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9323
	 * If this cpu has a pending nohz_balance_kick, then do the
9324
	 * balancing on behalf of the other idle cpus whose ticks are
9325 9326 9327 9328
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
	 * give the idle cpus a chance to load balance. Else we may
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9329
	 */
9330
	nohz_idle_balance(this_rq, idle);
9331
	rebalance_domains(this_rq, idle);
9332 9333 9334 9335 9336
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9337
void trigger_load_balance(struct rq *rq)
9338 9339
{
	/* Don't need to rebalance while attached to NULL domain */
9340 9341 9342 9343
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9344
		raise_softirq(SCHED_SOFTIRQ);
9345
#ifdef CONFIG_NO_HZ_COMMON
9346
	if (nohz_kick_needed(rq))
9347
		nohz_balancer_kick();
9348
#endif
9349 9350
}

9351 9352 9353
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9354 9355

	update_runtime_enabled(rq);
9356 9357 9358 9359 9360
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9361 9362 9363

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9364 9365
}

9366
#endif /* CONFIG_SMP */
9367

9368 9369 9370
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
9371
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9372 9373 9374 9375 9376 9377
{
	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
9378
		entity_tick(cfs_rq, se, queued);
9379
	}
9380

9381
	if (static_branch_unlikely(&sched_numa_balancing))
9382
		task_tick_numa(rq, curr);
9383 9384 9385
}

/*
P
Peter Zijlstra 已提交
9386 9387 9388
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9389
 */
P
Peter Zijlstra 已提交
9390
static void task_fork_fair(struct task_struct *p)
9391
{
9392 9393
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9394
	struct rq *rq = this_rq();
9395
	struct rq_flags rf;
9396

9397
	rq_lock(rq, &rf);
9398 9399
	update_rq_clock(rq);

9400 9401
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9402 9403
	if (curr) {
		update_curr(cfs_rq);
9404
		se->vruntime = curr->vruntime;
9405
	}
9406
	place_entity(cfs_rq, se, 1);
9407

P
Peter Zijlstra 已提交
9408
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9409
		/*
9410 9411 9412
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9413
		swap(curr->vruntime, se->vruntime);
9414
		resched_curr(rq);
9415
	}
9416

9417
	se->vruntime -= cfs_rq->min_vruntime;
9418
	rq_unlock(rq, &rf);
9419 9420
}

9421 9422 9423 9424
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9425 9426
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9427
{
9428
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9429 9430
		return;

9431 9432 9433 9434 9435
	/*
	 * 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
9436
	if (rq->curr == p) {
9437
		if (p->prio > oldprio)
9438
			resched_curr(rq);
9439
	} else
9440
		check_preempt_curr(rq, p, 0);
9441 9442
}

9443
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9444 9445 9446 9447
{
	struct sched_entity *se = &p->se;

	/*
9448 9449 9450 9451 9452 9453 9454 9455 9456 9457
	 * 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
9458
	 *
9459 9460 9461 9462
	 * - 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
9463
	 */
9464 9465 9466 9467 9468 9469
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9470 9471 9472 9473 9474 9475 9476 9477 9478 9479 9480 9481 9482 9483 9484 9485 9486 9487
#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;

9488
		update_load_avg(cfs_rq, se, UPDATE_TG);
9489 9490 9491 9492 9493 9494
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9495
static void detach_entity_cfs_rq(struct sched_entity *se)
9496 9497 9498
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9499
	/* Catch up with the cfs_rq and remove our load when we leave */
9500
	update_load_avg(cfs_rq, se, 0);
9501
	detach_entity_load_avg(cfs_rq, se);
9502
	update_tg_load_avg(cfs_rq, false);
9503
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9504 9505
}

9506
static void attach_entity_cfs_rq(struct sched_entity *se)
9507
{
9508
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9509 9510

#ifdef CONFIG_FAIR_GROUP_SCHED
9511 9512 9513 9514 9515 9516
	/*
	 * 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
9517

9518
	/* Synchronize entity with its cfs_rq */
9519
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9520
	attach_entity_load_avg(cfs_rq, se);
9521
	update_tg_load_avg(cfs_rq, false);
9522
	propagate_entity_cfs_rq(se);
9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537 9538 9539 9540 9541 9542 9543 9544 9545 9546 9547
}

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);
9548 9549 9550 9551

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9552

9553 9554 9555 9556 9557 9558 9559 9560
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);
9561

9562
	if (task_on_rq_queued(p)) {
9563
		/*
9564 9565 9566
		 * 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.
9567
		 */
9568 9569 9570 9571
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9572
	}
9573 9574
}

9575 9576 9577 9578 9579 9580 9581 9582 9583
/* 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;

9584 9585 9586 9587 9588 9589 9590
	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);
	}
9591 9592
}

9593 9594
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9595
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9596 9597 9598 9599
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9600
#ifdef CONFIG_SMP
9601
	raw_spin_lock_init(&cfs_rq->removed.lock);
9602
#endif
9603 9604
}

P
Peter Zijlstra 已提交
9605
#ifdef CONFIG_FAIR_GROUP_SCHED
9606 9607 9608 9609 9610 9611 9612 9613
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;
}

9614
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9615
{
9616
	detach_task_cfs_rq(p);
9617
	set_task_rq(p, task_cpu(p));
9618 9619 9620 9621 9622

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9623
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9624
}
9625

9626 9627 9628 9629 9630 9631 9632 9633 9634 9635 9636 9637 9638
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;
	}
}

9639 9640 9641 9642 9643 9644 9645 9646 9647
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]);
9648
		if (tg->se)
9649 9650 9651 9652 9653 9654 9655 9656 9657 9658
			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;
9659
	struct cfs_rq *cfs_rq;
9660 9661 9662 9663 9664 9665 9666 9667 9668 9669 9670 9671 9672 9673 9674 9675 9676 9677 9678 9679 9680 9681 9682 9683 9684 9685
	int i;

	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->cfs_rq)
		goto err;
	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
	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]);
9686
		init_entity_runnable_average(se);
9687 9688 9689 9690 9691 9692 9693 9694 9695 9696
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9697 9698 9699 9700 9701 9702 9703 9704 9705 9706 9707
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);
9708
		update_rq_clock(rq);
9709
		attach_entity_cfs_rq(se);
9710
		sync_throttle(tg, i);
9711 9712 9713 9714
		raw_spin_unlock_irq(&rq->lock);
	}
}

9715
void unregister_fair_sched_group(struct task_group *tg)
9716 9717
{
	unsigned long flags;
9718 9719
	struct rq *rq;
	int cpu;
9720

9721 9722 9723
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
9724

9725 9726 9727 9728 9729 9730 9731 9732 9733 9734 9735 9736 9737
		/*
		 * 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);
	}
9738 9739 9740 9741 9742 9743 9744 9745 9746 9747 9748 9749 9750 9751 9752 9753 9754 9755 9756
}

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
9757
	if (!parent) {
9758
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
9759 9760
		se->depth = 0;
	} else {
9761
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
9762 9763
		se->depth = parent->depth + 1;
	}
9764 9765

	se->my_q = cfs_rq;
9766 9767
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
9768 9769 9770 9771 9772 9773 9774 9775 9776 9777 9778 9779 9780 9781 9782 9783 9784 9785 9786 9787 9788 9789 9790 9791
	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);
9792 9793
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
9794 9795

		/* Propagate contribution to hierarchy */
9796
		rq_lock_irqsave(rq, &rf);
9797
		update_rq_clock(rq);
9798
		for_each_sched_entity(se) {
9799
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
9800
			update_cfs_group(se);
9801
		}
9802
		rq_unlock_irqrestore(rq, &rf);
9803 9804 9805 9806 9807 9808 9809 9810 9811 9812 9813 9814 9815 9816 9817
	}

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;
}

9818 9819
void online_fair_sched_group(struct task_group *tg) { }

9820
void unregister_fair_sched_group(struct task_group *tg) { }
9821 9822 9823

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
9824

9825
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9826 9827 9828 9829 9830 9831 9832 9833 9834
{
	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)
9835
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9836 9837 9838 9839

	return rr_interval;
}

9840 9841 9842
/*
 * All the scheduling class methods:
 */
9843
const struct sched_class fair_sched_class = {
9844
	.next			= &idle_sched_class,
9845 9846 9847
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
9848
	.yield_to_task		= yield_to_task_fair,
9849

I
Ingo Molnar 已提交
9850
	.check_preempt_curr	= check_preempt_wakeup,
9851 9852 9853 9854

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

9855
#ifdef CONFIG_SMP
L
Li Zefan 已提交
9856
	.select_task_rq		= select_task_rq_fair,
9857
	.migrate_task_rq	= migrate_task_rq_fair,
9858

9859 9860
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
9861

9862
	.task_dead		= task_dead_fair,
9863
	.set_cpus_allowed	= set_cpus_allowed_common,
9864
#endif
9865

9866
	.set_curr_task          = set_curr_task_fair,
9867
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
9868
	.task_fork		= task_fork_fair,
9869 9870

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
9871
	.switched_from		= switched_from_fair,
9872
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
9873

9874 9875
	.get_rr_interval	= get_rr_interval_fair,

9876 9877
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
9878
#ifdef CONFIG_FAIR_GROUP_SCHED
9879
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
9880
#endif
9881 9882 9883
};

#ifdef CONFIG_SCHED_DEBUG
9884
void print_cfs_stats(struct seq_file *m, int cpu)
9885
{
9886
	struct cfs_rq *cfs_rq, *pos;
9887

9888
	rcu_read_lock();
9889
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
9890
		print_cfs_rq(m, cpu, cfs_rq);
9891
	rcu_read_unlock();
9892
}
9893 9894 9895 9896 9897 9898 9899 9900 9901 9902 9903 9904 9905 9906 9907 9908 9909 9910 9911 9912 9913

#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 */
9914 9915 9916 9917 9918 9919

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

9920
#ifdef CONFIG_NO_HZ_COMMON
9921
	nohz.next_balance = jiffies;
9922 9923 9924 9925 9926
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}