fair.c 248.3 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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	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 (cfs_rq->rb_leftmost) {
		struct sched_entity *se = rb_entry(cfs_rq->rb_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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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	int leftmost = 1;

	/*
	 * 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;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
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	if (leftmost)
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		cfs_rq->rb_leftmost = &se->run_node;
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	rb_link_node(&se->run_node, parent, link);
	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
}

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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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	if (cfs_rq->rb_leftmost == &se->run_node) {
		struct rb_node *next_node;

		next_node = rb_next(&se->run_node);
		cfs_rq->rb_leftmost = next_node;
	}
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	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

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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 = cfs_rq->rb_leftmost;

	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);
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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)
{
676 677 678 679
	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
680 681
}

682 683 684 685
/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
686
 * s = p*P[w/rw]
687
 */
P
Peter Zijlstra 已提交
688
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
689
{
M
Mike Galbraith 已提交
690
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
691

M
Mike Galbraith 已提交
692
	for_each_sched_entity(se) {
L
Lin Ming 已提交
693
		struct load_weight *load;
694
		struct load_weight lw;
L
Lin Ming 已提交
695 696 697

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
698

M
Mike Galbraith 已提交
699
		if (unlikely(!se->on_rq)) {
700
			lw = cfs_rq->load;
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Mike Galbraith 已提交
701 702 703 704

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
705
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
706 707
	}
	return slice;
708 709
}

710
/*
A
Andrei Epure 已提交
711
 * We calculate the vruntime slice of a to-be-inserted task.
712
 *
713
 * vs = s/w
714
 */
715
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
716
{
717
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
718 719
}

720
#ifdef CONFIG_SMP
721 722 723

#include "sched-pelt.h"

724
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
725 726
static unsigned long task_h_load(struct task_struct *p);

727 728
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
729
{
730
	struct sched_avg *sa = &se->avg;
731

732 733 734 735 736 737 738
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
739 740 741 742 743 744 745 746
	/*
	 * 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))
		sa->load_avg = scale_load_down(se->load.weight);
747
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
748 749 750 751 752
	/*
	 * At this point, util_avg won't be used in select_task_rq_fair anyway
	 */
	sa->util_avg = 0;
	sa->util_sum = 0;
753
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
754
}
755

756
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
757
static void attach_entity_cfs_rq(struct sched_entity *se);
758

759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787
/*
 * 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;
788
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
789 790 791 792 793 794 795 796 797 798 799 800 801

	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;
		}
		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
	}
802 803 804 805 806 807 808 809 810 811 812 813 814 815

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
			update_cfs_rq_load_avg(now, cfs_rq, false);
			attach_entity_load_avg(cfs_rq, se);
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
816
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
817 818 819 820
			return;
		}
	}

821
	attach_entity_cfs_rq(se);
822 823
}

824
#else /* !CONFIG_SMP */
825
void init_entity_runnable_average(struct sched_entity *se)
826 827
{
}
828 829 830
void post_init_entity_util_avg(struct sched_entity *se)
{
}
831 832 833
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
834
#endif /* CONFIG_SMP */
835

836
/*
837
 * Update the current task's runtime statistics.
838
 */
839
static void update_curr(struct cfs_rq *cfs_rq)
840
{
841
	struct sched_entity *curr = cfs_rq->curr;
842
	u64 now = rq_clock_task(rq_of(cfs_rq));
843
	u64 delta_exec;
844 845 846 847

	if (unlikely(!curr))
		return;

848 849
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
850
		return;
851

I
Ingo Molnar 已提交
852
	curr->exec_start = now;
853

854 855 856 857
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
858
	schedstat_add(cfs_rq->exec_clock, delta_exec);
859 860 861 862

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

863 864 865
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

866
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
867
		cpuacct_charge(curtask, delta_exec);
868
		account_group_exec_runtime(curtask, delta_exec);
869
	}
870 871

	account_cfs_rq_runtime(cfs_rq, delta_exec);
872 873
}

874 875 876 877 878
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

879
static inline void
880
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
881
{
882 883 884 885 886 887 888
	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);
889 890

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
891 892
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
893

894
	schedstat_set(se->statistics.wait_start, wait_start);
895 896
}

897
static inline void
898 899 900
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
901 902
	u64 delta;

903 904 905 906
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
907 908 909 910 911 912 913 914 915

	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.
			 */
916
			schedstat_set(se->statistics.wait_start, delta);
917 918 919 920 921
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

922 923 924 925 926
	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);
927 928
}

929
static inline void
930 931 932
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
933 934 935 936 937 938 939
	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);
940 941 942 943

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

944 945
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
946 947 948 949

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

950 951
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
			schedstat_set(se->statistics.sleep_max, delta);
952

953 954
		schedstat_set(se->statistics.sleep_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
955 956 957 958 959 960

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
961 962
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
963 964 965 966

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

967 968
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
			schedstat_set(se->statistics.block_max, delta);
969

970 971
		schedstat_set(se->statistics.block_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
972 973 974

		if (tsk) {
			if (tsk->in_iowait) {
975 976
				schedstat_add(se->statistics.iowait_sum, delta);
				schedstat_inc(se->statistics.iowait_count);
977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994
				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);
		}
	}
995 996
}

997 998 999
/*
 * Task is being enqueued - update stats:
 */
1000
static inline void
1001
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1002
{
1003 1004 1005
	if (!schedstat_enabled())
		return;

1006 1007 1008 1009
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
1010
	if (se != cfs_rq->curr)
1011
		update_stats_wait_start(cfs_rq, se);
1012 1013 1014

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
1015 1016 1017
}

static inline void
1018
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1019
{
1020 1021 1022 1023

	if (!schedstat_enabled())
		return;

1024 1025 1026 1027
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
1028
	if (se != cfs_rq->curr)
1029
		update_stats_wait_end(cfs_rq, se);
1030

1031 1032
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
1033

1034 1035 1036 1037 1038 1039
		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)));
1040 1041 1042
	}
}

1043 1044 1045 1046
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1047
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1048 1049 1050 1051
{
	/*
	 * We are starting a new run period:
	 */
1052
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1053 1054 1055 1056 1057 1058
}

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

1059 1060
#ifdef CONFIG_NUMA_BALANCING
/*
1061 1062 1063
 * 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.
1064
 */
1065 1066
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1067 1068 1069

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1070

1071 1072 1073
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097
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)
{
1098
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1099 1100 1101
	unsigned int scan, floor;
	unsigned int windows = 1;

1102 1103
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119
	floor = 1000 / windows;

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

static unsigned int task_scan_max(struct task_struct *p)
{
	unsigned int smin = task_scan_min(p);
	unsigned int smax;

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
	return max(smin, smax);
}

1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131
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));
}

1132 1133 1134 1135 1136
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
1137
	pid_t gid;
1138
	int active_nodes;
1139 1140

	struct rcu_head rcu;
1141
	unsigned long total_faults;
1142
	unsigned long max_faults_cpu;
1143 1144 1145 1146 1147
	/*
	 * 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.
	 */
1148
	unsigned long *faults_cpu;
1149
	unsigned long faults[0];
1150 1151
};

1152 1153 1154 1155 1156 1157 1158 1159 1160
/* 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)

1161 1162 1163 1164 1165
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1166 1167 1168 1169 1170 1171 1172
/*
 * 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)
1173
{
1174
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1175 1176 1177 1178
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1179
	if (!p->numa_faults)
1180 1181
		return 0;

1182 1183
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1184 1185
}

1186 1187 1188 1189 1190
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1191 1192
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1193 1194
}

1195 1196
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1197 1198
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1199 1200
}

1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
/*
 * 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;
}

1213 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 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277
/* 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;
}

1278 1279 1280 1281 1282 1283
/*
 * 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.
 */
1284 1285
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1286
{
1287
	unsigned long faults, total_faults;
1288

1289
	if (!p->numa_faults)
1290 1291 1292 1293 1294 1295 1296
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1297
	faults = task_faults(p, nid);
1298 1299
	faults += score_nearby_nodes(p, nid, dist, true);

1300
	return 1000 * faults / total_faults;
1301 1302
}

1303 1304
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1305
{
1306 1307 1308 1309 1310 1311 1312 1313
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1314 1315
		return 0;

1316
	faults = group_faults(p, nid);
1317 1318
	faults += score_nearby_nodes(p, nid, dist, false);

1319
	return 1000 * faults / total_faults;
1320 1321
}

1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361
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;

	/*
1362 1363
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1364
	 */
1365 1366
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1367 1368 1369
		return true;

	/*
1370 1371 1372 1373 1374 1375
	 * 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)
1376
	 */
1377 1378
	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;
1379 1380
}

1381
static unsigned long weighted_cpuload(const int cpu);
1382 1383
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1384
static unsigned long capacity_of(int cpu);
1385 1386
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1387
/* Cached statistics for all CPUs within a node */
1388
struct numa_stats {
1389
	unsigned long nr_running;
1390
	unsigned long load;
1391 1392

	/* Total compute capacity of CPUs on a node */
1393
	unsigned long compute_capacity;
1394 1395

	/* Approximate capacity in terms of runnable tasks on a node */
1396
	unsigned long task_capacity;
1397
	int has_free_capacity;
1398
};
1399

1400 1401 1402 1403 1404
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1405 1406
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1407 1408 1409 1410 1411 1412 1413

	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;
		ns->load += weighted_cpuload(cpu);
1414
		ns->compute_capacity += capacity_of(cpu);
1415 1416

		cpus++;
1417 1418
	}

1419 1420 1421 1422 1423
	/*
	 * 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.
	 *
1424 1425
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1426 1427 1428 1429
	 */
	if (!cpus)
		return;

1430 1431 1432 1433 1434 1435
	/* 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));
1436
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1437 1438
}

1439 1440
struct task_numa_env {
	struct task_struct *p;
1441

1442 1443
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1444

1445
	struct numa_stats src_stats, dst_stats;
1446

1447
	int imbalance_pct;
1448
	int dist;
1449 1450 1451

	struct task_struct *best_task;
	long best_imp;
1452 1453 1454
	int best_cpu;
};

1455 1456 1457 1458 1459
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);
1460 1461
	if (p)
		get_task_struct(p);
1462 1463 1464 1465 1466 1467

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

1468
static bool load_too_imbalanced(long src_load, long dst_load,
1469 1470
				struct task_numa_env *env)
{
1471 1472
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483
	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;
1484 1485

	/* We care about the slope of the imbalance, not the direction. */
1486 1487
	if (dst_load < src_load)
		swap(dst_load, src_load);
1488 1489

	/* Is the difference below the threshold? */
1490 1491
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1492 1493 1494 1495 1496
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1497
	 * Compare it with the old imbalance.
1498
	 */
1499
	orig_src_load = env->src_stats.load;
1500
	orig_dst_load = env->dst_stats.load;
1501

1502 1503
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1504

1505 1506 1507 1508 1509
	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);
1510 1511
}

1512 1513 1514 1515 1516 1517
/*
 * 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
 */
1518 1519
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1520 1521 1522 1523
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1524
	long src_load, dst_load;
1525
	long load;
1526
	long imp = env->p->numa_group ? groupimp : taskimp;
1527
	long moveimp = imp;
1528
	int dist = env->dist;
1529 1530

	rcu_read_lock();
1531 1532
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1533 1534
		cur = NULL;

1535 1536 1537 1538 1539 1540 1541
	/*
	 * 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;

1542 1543 1544 1545 1546 1547 1548 1549 1550
	/*
	 * "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 */
1551
		if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1552 1553
			goto unlock;

1554 1555
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1556
		 * in any group then look only at task weights.
1557
		 */
1558
		if (cur->numa_group == env->p->numa_group) {
1559 1560
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1561 1562 1563 1564 1565 1566
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1567
		} else {
1568 1569 1570 1571 1572 1573
			/*
			 * 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)
1574 1575
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1576
			else
1577 1578
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1579
		}
1580 1581
	}

1582
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1583 1584 1585 1586
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1587
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1588
		    !env->dst_stats.has_free_capacity)
1589 1590 1591 1592 1593 1594
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1595 1596
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1597 1598 1599 1600 1601 1602
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1603 1604 1605
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1606

1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
	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;

1624
	if (cur) {
1625 1626 1627
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1628 1629
	}

1630
	if (load_too_imbalanced(src_load, dst_load, env))
1631 1632
		goto unlock;

1633 1634 1635 1636
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1637 1638 1639 1640 1641 1642
	if (!cur) {
		/*
		 * select_idle_siblings() uses an per-cpu cpumask that
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1643 1644
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1645 1646
		local_irq_enable();
	}
1647

1648 1649 1650 1651 1652 1653
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1654 1655
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1656 1657 1658 1659 1660
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1661
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1662 1663 1664
			continue;

		env->dst_cpu = cpu;
1665
		task_numa_compare(env, taskimp, groupimp);
1666 1667 1668
	}
}

1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685
/* 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
	 */
1686 1687 1688
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1689 1690 1691 1692 1693
		return true;

	return false;
}

1694 1695 1696 1697
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1698

1699
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1700
		.src_nid = task_node(p),
1701 1702 1703 1704 1705

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1706
		.best_cpu = -1,
1707 1708
	};
	struct sched_domain *sd;
1709
	unsigned long taskweight, groupweight;
1710
	int nid, ret, dist;
1711
	long taskimp, groupimp;
1712

1713
	/*
1714 1715 1716 1717 1718 1719
	 * 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.
1720 1721
	 */
	rcu_read_lock();
1722
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1723 1724
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1725 1726
	rcu_read_unlock();

1727 1728 1729 1730 1731 1732 1733
	/*
	 * 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)) {
1734
		p->numa_preferred_nid = task_node(p);
1735 1736 1737
		return -EINVAL;
	}

1738
	env.dst_nid = p->numa_preferred_nid;
1739 1740 1741 1742 1743 1744
	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;
1745
	update_numa_stats(&env.dst_stats, env.dst_nid);
1746

1747
	/* Try to find a spot on the preferred nid. */
1748 1749
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1750

1751 1752 1753 1754 1755 1756 1757
	/*
	 * 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.
	 */
1758
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1759 1760 1761
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1762

1763
			dist = node_distance(env.src_nid, env.dst_nid);
1764 1765 1766 1767 1768
			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);
			}
1769

1770
			/* Only consider nodes where both task and groups benefit */
1771 1772
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1773
			if (taskimp < 0 && groupimp < 0)
1774 1775
				continue;

1776
			env.dist = dist;
1777 1778
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1779 1780
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1781 1782 1783
		}
	}

1784 1785 1786 1787 1788 1789 1790 1791
	/*
	 * 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.
	 */
1792
	if (p->numa_group) {
1793 1794
		struct numa_group *ng = p->numa_group;

1795 1796 1797 1798 1799
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1800
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1801 1802 1803 1804 1805 1806
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1807

1808 1809 1810 1811 1812 1813
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
	p->numa_scan_period = task_scan_min(p);

1814
	if (env.best_task == NULL) {
1815 1816 1817
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1818 1819 1820 1821
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1822 1823
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1824 1825
	put_task_struct(env.best_task);
	return ret;
1826 1827
}

1828 1829 1830
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1831 1832
	unsigned long interval = HZ;

1833
	/* This task has no NUMA fault statistics yet */
1834
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1835 1836
		return;

1837
	/* Periodically retry migrating the task to the preferred node */
1838 1839
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1840 1841

	/* Success if task is already running on preferred CPU */
1842
	if (task_node(p) == p->numa_preferred_nid)
1843 1844 1845
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1846
	task_numa_migrate(p);
1847 1848
}

1849
/*
1850
 * Find out how many nodes on the workload is actively running on. Do this by
1851 1852 1853 1854
 * 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.
 */
1855
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1856 1857
{
	unsigned long faults, max_faults = 0;
1858
	int nid, active_nodes = 0;
1859 1860 1861 1862 1863 1864 1865 1866 1867

	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);
1868 1869
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1870
	}
1871 1872 1873

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1874 1875
}

1876 1877 1878
/*
 * 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
1879 1880 1881
 * 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.
1882 1883
 */
#define NUMA_PERIOD_SLOTS 10
1884
#define NUMA_PERIOD_THRESHOLD 7
1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904

/*
 * 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;
	int ratio;
	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
1905 1906 1907
	 * 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
1908
	 */
1909
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942
		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);
	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	if (ratio >= NUMA_PERIOD_THRESHOLD) {
		int slot = ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;

		/*
		 * Scale scan rate increases based on sharing. There is an
		 * inverse relationship between the degree of sharing and
		 * the adjustment made to the scanning period. Broadly
		 * speaking the intent is that there is little point
		 * scanning faster if shared accesses dominate as it may
		 * simply bounce migrations uselessly
		 */
1943
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1944 1945 1946 1947 1948 1949 1950 1951
		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
	}

	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));
}

1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969
/*
 * 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 {
1970 1971
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1972 1973 1974 1975 1976 1977 1978 1979
	}

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

	return delta;
}

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026
/*
 * 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;
2027
		nodemask_t max_group = NODE_MASK_NONE;
2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060
		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. */
2061 2062
		if (!max_faults)
			break;
2063 2064 2065 2066 2067
		nodes = max_group;
	}
	return nid;
}

2068 2069
static void task_numa_placement(struct task_struct *p)
{
2070 2071
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2072
	unsigned long fault_types[2] = { 0, 0 };
2073 2074
	unsigned long total_faults;
	u64 runtime, period;
2075
	spinlock_t *group_lock = NULL;
2076

2077 2078 2079 2080 2081
	/*
	 * 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:
	 */
2082
	seq = READ_ONCE(p->mm->numa_scan_seq);
2083 2084 2085
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2086
	p->numa_scan_period_max = task_scan_max(p);
2087

2088 2089 2090 2091
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2092 2093 2094
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2095
		spin_lock_irq(group_lock);
2096 2097
	}

2098 2099
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2100 2101
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2102
		unsigned long faults = 0, group_faults = 0;
2103
		int priv;
2104

2105
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2106
			long diff, f_diff, f_weight;
2107

2108 2109 2110 2111
			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);
2112

2113
			/* Decay existing window, copy faults since last scan */
2114 2115 2116
			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;
2117

2118 2119 2120 2121 2122 2123 2124 2125
			/*
			 * 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);
2126
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2127
				   (total_faults + 1);
2128 2129
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2130

2131 2132 2133
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2134
			p->total_numa_faults += diff;
2135
			if (p->numa_group) {
2136 2137 2138 2139 2140 2141 2142 2143 2144
				/*
				 * 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;
2145
				p->numa_group->total_faults += diff;
2146
				group_faults += p->numa_group->faults[mem_idx];
2147
			}
2148 2149
		}

2150 2151 2152 2153
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2154 2155 2156 2157 2158 2159 2160

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

2161 2162
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2163
	if (p->numa_group) {
2164
		numa_group_count_active_nodes(p->numa_group);
2165
		spin_unlock_irq(group_lock);
2166
		max_nid = preferred_group_nid(p, max_group_nid);
2167 2168
	}

2169 2170 2171 2172 2173 2174 2175
	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);
2176
	}
2177 2178
}

2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189
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);
}

2190 2191
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2192 2193 2194 2195 2196 2197 2198 2199 2200
{
	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) +
2201
				    4*nr_node_ids*sizeof(unsigned long);
2202 2203 2204 2205 2206 2207

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

		atomic_set(&grp->refcount, 1);
2208 2209
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2210
		spin_lock_init(&grp->lock);
2211
		grp->gid = p->pid;
2212
		/* Second half of the array tracks nids where faults happen */
2213 2214
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2215

2216
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2217
			grp->faults[i] = p->numa_faults[i];
2218

2219
		grp->total_faults = p->total_numa_faults;
2220

2221 2222 2223 2224 2225
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2226
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2227 2228

	if (!cpupid_match_pid(tsk, cpupid))
2229
		goto no_join;
2230 2231 2232

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2233
		goto no_join;
2234 2235 2236

	my_grp = p->numa_group;
	if (grp == my_grp)
2237
		goto no_join;
2238 2239 2240 2241 2242 2243

	/*
	 * 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)
2244
		goto no_join;
2245 2246 2247 2248 2249

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2250
		goto no_join;
2251

2252 2253 2254 2255 2256 2257 2258
	/* 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;
2259

2260 2261 2262
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2263
	if (join && !get_numa_group(grp))
2264
		goto no_join;
2265 2266 2267 2268 2269 2270

	rcu_read_unlock();

	if (!join)
		return;

2271 2272
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2273

2274
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2275 2276
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2277
	}
2278 2279
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2280 2281 2282 2283 2284

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

	spin_unlock(&my_grp->lock);
2285
	spin_unlock_irq(&grp->lock);
2286 2287 2288 2289

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2290 2291 2292 2293 2294
	return;

no_join:
	rcu_read_unlock();
	return;
2295 2296 2297 2298 2299
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2300
	void *numa_faults = p->numa_faults;
2301 2302
	unsigned long flags;
	int i;
2303 2304

	if (grp) {
2305
		spin_lock_irqsave(&grp->lock, flags);
2306
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2307
			grp->faults[i] -= p->numa_faults[i];
2308
		grp->total_faults -= p->total_numa_faults;
2309

2310
		grp->nr_tasks--;
2311
		spin_unlock_irqrestore(&grp->lock, flags);
2312
		RCU_INIT_POINTER(p->numa_group, NULL);
2313 2314 2315
		put_numa_group(grp);
	}

2316
	p->numa_faults = NULL;
2317
	kfree(numa_faults);
2318 2319
}

2320 2321 2322
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2323
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2324 2325
{
	struct task_struct *p = current;
2326
	bool migrated = flags & TNF_MIGRATED;
2327
	int cpu_node = task_node(current);
2328
	int local = !!(flags & TNF_FAULT_LOCAL);
2329
	struct numa_group *ng;
2330
	int priv;
2331

2332
	if (!static_branch_likely(&sched_numa_balancing))
2333 2334
		return;

2335 2336 2337 2338
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2339
	/* Allocate buffer to track faults on a per-node basis */
2340 2341
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2342
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2343

2344 2345
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2346
			return;
2347

2348
		p->total_numa_faults = 0;
2349
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2350
	}
2351

2352 2353 2354 2355 2356 2357 2358 2359
	/*
	 * 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);
2360
		if (!priv && !(flags & TNF_NO_GROUP))
2361
			task_numa_group(p, last_cpupid, flags, &priv);
2362 2363
	}

2364 2365 2366 2367 2368 2369
	/*
	 * 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.
	 */
2370 2371 2372 2373
	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))
2374 2375
		local = 1;

2376
	task_numa_placement(p);
2377

2378 2379 2380 2381 2382
	/*
	 * 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))
2383 2384
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2385 2386
	if (migrated)
		p->numa_pages_migrated += pages;
2387 2388
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2389

2390 2391
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2392
	p->numa_faults_locality[local] += pages;
2393 2394
}

2395 2396
static void reset_ptenuma_scan(struct task_struct *p)
{
2397 2398 2399 2400 2401 2402 2403 2404
	/*
	 * 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:
	 */
2405
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2406 2407 2408
	p->mm->numa_scan_offset = 0;
}

2409 2410 2411 2412 2413 2414 2415 2416 2417
/*
 * 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;
2418
	u64 runtime = p->se.sum_exec_runtime;
2419
	struct vm_area_struct *vma;
2420
	unsigned long start, end;
2421
	unsigned long nr_pte_updates = 0;
2422
	long pages, virtpages;
2423

2424
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437

	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;

2438
	if (!mm->numa_next_scan) {
2439 2440
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2441 2442
	}

2443 2444 2445 2446 2447 2448 2449
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2450 2451 2452 2453
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2454

2455
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2456 2457 2458
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2459 2460 2461 2462 2463 2464
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2465 2466 2467
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2468
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2469 2470
	if (!pages)
		return;
2471

2472

2473 2474
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2475
	vma = find_vma(mm, start);
2476 2477
	if (!vma) {
		reset_ptenuma_scan(p);
2478
		start = 0;
2479 2480
		vma = mm->mmap;
	}
2481
	for (; vma; vma = vma->vm_next) {
2482
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2483
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2484
			continue;
2485
		}
2486

2487 2488 2489 2490 2491 2492 2493 2494 2495 2496
		/*
		 * 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
2497 2498 2499 2500 2501 2502
		/*
		 * 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;
2503

2504 2505 2506 2507
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2508
			nr_pte_updates = change_prot_numa(vma, start, end);
2509 2510

			/*
2511 2512 2513 2514 2515 2516
			 * 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.
2517 2518 2519
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2520
			virtpages -= (end - start) >> PAGE_SHIFT;
2521

2522
			start = end;
2523
			if (pages <= 0 || virtpages <= 0)
2524
				goto out;
2525 2526

			cond_resched();
2527
		} while (end != vma->vm_end);
2528
	}
2529

2530
out:
2531
	/*
P
Peter Zijlstra 已提交
2532 2533 2534 2535
	 * 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.
2536 2537
	 */
	if (vma)
2538
		mm->numa_scan_offset = start;
2539 2540 2541
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552

	/*
	 * 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;
	}
2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577
}

/*
 * 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;

2578
	if (now > curr->node_stamp + period) {
2579
		if (!curr->node_stamp)
2580
			curr->numa_scan_period = task_scan_min(curr);
2581
		curr->node_stamp += period;
2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592

		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);
		}
	}
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2593 2594 2595 2596 2597 2598 2599 2600

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)
{
}
2601 2602
#endif /* CONFIG_NUMA_BALANCING */

2603 2604 2605 2606
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2607
	if (!parent_entity(se))
2608
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2609
#ifdef CONFIG_SMP
2610 2611 2612 2613 2614 2615
	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);
	}
2616
#endif
2617 2618 2619 2620 2621 2622 2623
	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);
2624
	if (!parent_entity(se))
2625
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2626
#ifdef CONFIG_SMP
2627 2628
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2629
		list_del_init(&se->group_node);
2630
	}
2631
#endif
2632 2633 2634
	cfs_rq->nr_running--;
}

2635 2636
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2637
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2638
{
2639
	long tg_weight, load, shares;
2640 2641

	/*
2642 2643 2644
	 * This really should be: cfs_rq->avg.load_avg, but instead we use
	 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
	 * the shares for small weight interactive tasks.
2645
	 */
2646
	load = scale_load_down(cfs_rq->load.weight);
2647

2648
	tg_weight = atomic_long_read(&tg->load_avg);
2649

2650 2651 2652
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2653 2654

	shares = (tg->shares * load);
2655 2656
	if (tg_weight)
		shares /= tg_weight;
2657

2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669
	/*
	 * 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.
	 */
2670 2671 2672 2673 2674 2675 2676 2677
	if (shares < MIN_SHARES)
		shares = MIN_SHARES;
	if (shares > tg->shares)
		shares = tg->shares;

	return shares;
}
# else /* CONFIG_SMP */
2678
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2679 2680 2681 2682
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
2683

P
Peter Zijlstra 已提交
2684 2685 2686
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2687 2688 2689 2690
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2691
		account_entity_dequeue(cfs_rq, se);
2692
	}
P
Peter Zijlstra 已提交
2693 2694 2695 2696 2697 2698 2699

	update_load_set(&se->load, weight);

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

2700 2701
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2702
static void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2703
{
2704
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
P
Peter Zijlstra 已提交
2705
	struct task_group *tg;
2706
	long shares;
P
Peter Zijlstra 已提交
2707

2708 2709 2710 2711
	if (!cfs_rq)
		return;

	if (throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2712
		return;
2713 2714 2715

	tg = cfs_rq->tg;

2716 2717 2718 2719
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2720
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2721 2722 2723

	reweight_entity(cfs_rq_of(se), se, shares);
}
2724

P
Peter Zijlstra 已提交
2725
#else /* CONFIG_FAIR_GROUP_SCHED */
2726
static inline void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2727 2728 2729 2730
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2731
#ifdef CONFIG_SMP
2732 2733 2734 2735
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
2736
static u64 decay_load(u64 val, u64 n)
2737
{
2738 2739
	unsigned int local_n;

2740
	if (unlikely(n > LOAD_AVG_PERIOD * 63))
2741 2742 2743 2744 2745 2746 2747
		return 0;

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

	/*
	 * As y^PERIOD = 1/2, we can combine
2748 2749
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2750 2751 2752 2753 2754 2755
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2756 2757
	}

2758 2759
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2760 2761
}

2762
static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
2763
{
2764
	u32 c1, c2, c3 = d3; /* y^0 == 1 */
2765

2766
	/*
P
Peter Zijlstra 已提交
2767
	 * c1 = d1 y^p
2768
	 */
2769
	c1 = decay_load((u64)d1, periods);
2770 2771

	/*
P
Peter Zijlstra 已提交
2772
	 *            p-1
2773 2774
	 * c2 = 1024 \Sum y^n
	 *            n=1
2775
	 *
2776 2777
	 *              inf        inf
	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
P
Peter Zijlstra 已提交
2778
	 *              n=0        n=p
2779
	 */
2780
	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
2781 2782

	return c1 + c2 + c3;
2783 2784
}

2785
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2786

2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797
/*
 * 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
2798 2799 2800
 *                           p-1
 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
 *                           n=1
2801
 *
P
Peter Zijlstra 已提交
2802
 *    = u y^p +					(Step 1)
2803
 *
P
Peter Zijlstra 已提交
2804 2805 2806
 *                     p-1
 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2)
 *                     n=1
2807 2808 2809 2810 2811 2812
 */
static __always_inline u32
accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
	       unsigned long weight, int running, struct cfs_rq *cfs_rq)
{
	unsigned long scale_freq, scale_cpu;
2813
	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832
	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);
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods);
		}
		sa->util_sum = decay_load((u64)(sa->util_sum), periods);

2833 2834 2835 2836 2837 2838 2839
		/*
		 * Step 2
		 */
		delta %= 1024;
		contrib = __accumulate_pelt_segments(periods,
				1024 - sa->period_contrib, delta);
	}
2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853
	sa->period_contrib = delta;

	contrib = cap_scale(contrib, scale_freq);
	if (weight) {
		sa->load_sum += weight * contrib;
		if (cfs_rq)
			cfs_rq->runnable_load_sum += weight * contrib;
	}
	if (running)
		sa->util_sum += contrib * scale_cpu;

	return periods;
}

2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881
/*
 * 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}]
 */
2882
static __always_inline int
2883
___update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2884
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2885
{
2886
	u64 delta;
2887

2888
	delta = now - sa->last_update_time;
2889 2890 2891 2892 2893
	/*
	 * 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) {
2894
		sa->last_update_time = now;
2895 2896 2897 2898 2899 2900 2901 2902 2903 2904
		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;
2905 2906

	sa->last_update_time += delta << 10;
2907

2908 2909 2910 2911 2912 2913 2914 2915 2916
	/*
	 * 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.
	 */
	if (!accumulate_sum(delta, cpu, sa, weight, running, cfs_rq))
		return 0;
2917

2918 2919 2920
	/*
	 * Step 2: update *_avg.
	 */
2921
	sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib);
2922 2923
	if (cfs_rq) {
		cfs_rq->runnable_load_avg =
2924
			div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib);
2925
	}
2926
	sa->util_avg = sa->util_sum / (LOAD_AVG_MAX - 1024 + sa->period_contrib);
2927

2928
	return 1;
2929 2930
}

2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952
static int
__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
{
	return ___update_load_avg(now, cpu, &se->avg, 0, 0, NULL);
}

static int
__update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	return ___update_load_avg(now, cpu, &se->avg,
				  se->on_rq * scale_load_down(se->load.weight),
				  cfs_rq->curr == se, NULL);
}

static int
__update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
{
	return ___update_load_avg(now, cpu, &cfs_rq->avg,
			scale_load_down(cfs_rq->load.weight),
			cfs_rq->curr != NULL, cfs_rq);
}

2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972
/*
 * 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)

2973
#ifdef CONFIG_FAIR_GROUP_SCHED
2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988
/**
 * 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'.
 *
 * Updating tg's load_avg is necessary before update_cfs_share() (which is
 * done) and effective_load() (which is not done because it is too costly).
2989
 */
2990
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2991
{
2992
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2993

2994 2995 2996 2997 2998 2999
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3000 3001 3002
	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;
3003
	}
3004
}
3005

3006 3007 3008 3009 3010 3011 3012 3013
/*
 * 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)
{
3014 3015 3016
	u64 p_last_update_time;
	u64 n_last_update_time;

3017 3018 3019 3020 3021 3022 3023 3024 3025 3026
	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.
	 */
3027 3028
	if (!(se->avg.last_update_time && prev))
		return;
3029 3030

#ifndef CONFIG_64BIT
3031
	{
3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045
		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);
3046
	}
3047
#else
3048 3049
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3050
#endif
3051 3052
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3053
}
3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174

/* Take into account change of utilization of a child task group */
static inline void
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	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;
}

/* Take into account change of load of a child task group */
static inline void
update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long delta, load = gcfs_rq->avg.load_avg;

	/*
	 * If the load of group cfs_rq is null, the load of the
	 * sched_entity will also be null so we can skip the formula
	 */
	if (load) {
		long tg_load;

		/* Get tg's load and ensure tg_load > 0 */
		tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1;

		/* Ensure tg_load >= load and updated with current load*/
		tg_load -= gcfs_rq->tg_load_avg_contrib;
		tg_load += load;

		/*
		 * We need to compute a correction term in the case that the
		 * task group is consuming more CPU than a task of equal
		 * weight. A task with a weight equals to tg->shares will have
		 * a load less or equal to scale_load_down(tg->shares).
		 * Similarly, the sched_entities that represent the task group
		 * at parent level, can't have a load higher than
		 * scale_load_down(tg->shares). And the Sum of sched_entities'
		 * load must be <= scale_load_down(tg->shares).
		 */
		if (tg_load > scale_load_down(gcfs_rq->tg->shares)) {
			/* scale gcfs_rq's load into tg's shares*/
			load *= scale_load_down(gcfs_rq->tg->shares);
			load /= tg_load;
		}
	}

	delta = load - se->avg.load_avg;

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

	/* Set new sched_entity's load */
	se->avg.load_avg = load;
	se->avg.load_sum = se->avg.load_avg * LOAD_AVG_MAX;

	/* Update parent cfs_rq load */
	add_positive(&cfs_rq->avg.load_avg, delta);
	cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * LOAD_AVG_MAX;

	/*
	 * If the sched_entity is already enqueued, we also have to update the
	 * runnable load avg.
	 */
	if (se->on_rq) {
		/* Update parent cfs_rq runnable_load_avg */
		add_positive(&cfs_rq->runnable_load_avg, delta);
		cfs_rq->runnable_load_sum = cfs_rq->runnable_load_avg * LOAD_AVG_MAX;
	}
}

static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq)
{
	cfs_rq->propagate_avg = 1;
}

static inline int test_and_clear_tg_cfs_propagate(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = group_cfs_rq(se);

	if (!cfs_rq->propagate_avg)
		return 0;

	cfs_rq->propagate_avg = 0;
	return 1;
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq;

	if (entity_is_task(se))
		return 0;

	if (!test_and_clear_tg_cfs_propagate(se))
		return 0;

	cfs_rq = cfs_rq_of(se);

	set_tg_cfs_propagate(cfs_rq);

	update_tg_cfs_util(cfs_rq, se);
	update_tg_cfs_load(cfs_rq, se);

	return 1;
}

3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204
/*
 * 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:
	 */
	if (gcfs_rq->propagate_avg)
		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;
}

3205
#else /* CONFIG_FAIR_GROUP_SCHED */
3206

3207
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3208 3209 3210 3211 3212 3213 3214 3215

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

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

3216
#endif /* CONFIG_FAIR_GROUP_SCHED */
3217

3218 3219
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
3220
	if (&this_rq()->cfs == cfs_rq) {
3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236
		/*
		 * 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().
		 */
3237
		cpufreq_update_util(rq_of(cfs_rq), 0);
3238 3239 3240
	}
}

3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257
/*
 * 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)

3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269
/**
 * 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
 * @update_freq: should we call cfs_rq_util_change() or will the call do so
 *
 * 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.
 *
3270 3271 3272 3273
 * 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.
3274
 */
3275 3276
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
3277
{
3278
	struct sched_avg *sa = &cfs_rq->avg;
3279
	int decayed, removed_load = 0, removed_util = 0;
3280

3281
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
3282
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
3283 3284
		sub_positive(&sa->load_avg, r);
		sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
3285
		removed_load = 1;
3286
		set_tg_cfs_propagate(cfs_rq);
3287
	}
3288

3289 3290
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
3291 3292
		sub_positive(&sa->util_avg, r);
		sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
3293
		removed_util = 1;
3294
		set_tg_cfs_propagate(cfs_rq);
3295
	}
3296

3297
	decayed = __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3298

3299 3300 3301 3302
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3303

3304 3305
	if (update_freq && (decayed || removed_util))
		cfs_rq_util_change(cfs_rq);
3306

3307
	return decayed || removed_load;
3308 3309
}

3310 3311 3312 3313 3314 3315
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2

3316
/* Update task and its cfs_rq load average */
3317
static inline void update_load_avg(struct sched_entity *se, int flags)
3318 3319 3320 3321 3322
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);
3323
	int decayed;
3324 3325 3326 3327 3328

	/*
	 * 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
	 */
3329 3330
	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
		__update_load_avg_se(now, cpu, cfs_rq, se);
3331

3332 3333 3334 3335
	decayed  = update_cfs_rq_load_avg(now, cfs_rq, true);
	decayed |= propagate_entity_load_avg(se);

	if (decayed && (flags & UPDATE_TG))
3336
		update_tg_load_avg(cfs_rq, 0);
3337 3338
}

3339 3340 3341 3342 3343 3344 3345 3346
/**
 * 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.
 */
3347 3348 3349 3350 3351 3352 3353
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3354
	set_tg_cfs_propagate(cfs_rq);
3355 3356

	cfs_rq_util_change(cfs_rq);
3357 3358
}

3359 3360 3361 3362 3363 3364 3365 3366
/**
 * 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.
 */
3367 3368 3369
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{

3370 3371 3372 3373
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3374
	set_tg_cfs_propagate(cfs_rq);
3375 3376

	cfs_rq_util_change(cfs_rq);
3377 3378
}

3379 3380 3381
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3382
{
3383
	struct sched_avg *sa = &se->avg;
3384

3385 3386 3387
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3388
	if (!sa->last_update_time) {
3389
		attach_entity_load_avg(cfs_rq, se);
3390
		update_tg_load_avg(cfs_rq, 0);
3391
	}
3392 3393
}

3394 3395 3396 3397 3398 3399 3400
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
3401
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3402 3403
}

3404
#ifndef CONFIG_64BIT
3405 3406
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3407
	u64 last_update_time_copy;
3408
	u64 last_update_time;
3409

3410 3411 3412 3413 3414
	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);
3415 3416 3417

	return last_update_time;
}
3418
#else
3419 3420 3421 3422
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3423 3424
#endif

3425 3426 3427 3428 3429 3430 3431 3432 3433 3434
/*
 * 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);
3435
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3436 3437
}

3438 3439 3440 3441 3442 3443 3444 3445 3446
/*
 * 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);

	/*
3447 3448 3449 3450 3451 3452 3453
	 * 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.
3454 3455
	 */

3456
	sync_entity_load_avg(se);
3457 3458
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3459
}
3460

3461 3462 3463 3464 3465 3466 3467 3468 3469 3470
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

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

3471
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3472

3473 3474
#else /* CONFIG_SMP */

3475 3476 3477 3478 3479 3480
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
{
	return 0;
}

3481 3482 3483 3484
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0

static inline void update_load_avg(struct sched_entity *se, int not_used1)
3485
{
3486
	cpufreq_update_util(rq_of(cfs_rq_of(se)), 0);
3487 3488
}

3489 3490
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3491 3492
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3493
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3494

3495 3496 3497 3498 3499
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) {}

3500
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3501 3502 3503 3504
{
	return 0;
}

3505
#endif /* CONFIG_SMP */
3506

P
Peter Zijlstra 已提交
3507 3508 3509 3510 3511 3512 3513 3514 3515
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)
3516
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3517 3518 3519
#endif
}

3520 3521 3522
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3523
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3524

3525 3526 3527 3528 3529 3530
	/*
	 * 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
3531
	if (initial && sched_feat(START_DEBIT))
3532
		vruntime += sched_vslice(cfs_rq, se);
3533

3534
	/* sleeps up to a single latency don't count. */
3535
	if (!initial) {
3536
		unsigned long thresh = sysctl_sched_latency;
3537

3538 3539 3540 3541 3542 3543
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3544

3545
		vruntime -= thresh;
3546 3547
	}

3548
	/* ensure we never gain time by being placed backwards. */
3549
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3550 3551
}

3552 3553
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565
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())  {
3566
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3567 3568 3569 3570 3571 3572 3573
			     "stat_blocked and stat_runtime require the "
			     "kernel parameter schedstats=enabled or "
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592

/*
 * 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)
 *
3593
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604
 *	  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.
 */

3605
static void
3606
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3607
{
3608 3609 3610
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3611
	/*
3612 3613
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3614
	 */
3615
	if (renorm && curr)
3616 3617
		se->vruntime += cfs_rq->min_vruntime;

3618 3619
	update_curr(cfs_rq);

3620
	/*
3621 3622 3623 3624
	 * 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.
3625
	 */
3626 3627 3628
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3629 3630 3631 3632 3633 3634 3635 3636
	/*
	 * 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
	 */
3637
	update_load_avg(se, UPDATE_TG);
3638
	enqueue_entity_load_avg(cfs_rq, se);
3639
	update_cfs_shares(se);
3640
	account_entity_enqueue(cfs_rq, se);
3641

3642
	if (flags & ENQUEUE_WAKEUP)
3643
		place_entity(cfs_rq, se, 0);
3644

3645
	check_schedstat_required();
3646 3647
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3648
	if (!curr)
3649
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3650
	se->on_rq = 1;
3651

3652
	if (cfs_rq->nr_running == 1) {
3653
		list_add_leaf_cfs_rq(cfs_rq);
3654 3655
		check_enqueue_throttle(cfs_rq);
	}
3656 3657
}

3658
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3659
{
3660 3661
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3662
		if (cfs_rq->last != se)
3663
			break;
3664 3665

		cfs_rq->last = NULL;
3666 3667
	}
}
P
Peter Zijlstra 已提交
3668

3669 3670 3671 3672
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3673
		if (cfs_rq->next != se)
3674
			break;
3675 3676

		cfs_rq->next = NULL;
3677
	}
P
Peter Zijlstra 已提交
3678 3679
}

3680 3681 3682 3683
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3684
		if (cfs_rq->skip != se)
3685
			break;
3686 3687

		cfs_rq->skip = NULL;
3688 3689 3690
	}
}

P
Peter Zijlstra 已提交
3691 3692
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3693 3694 3695 3696 3697
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3698 3699 3700

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3701 3702
}

3703
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3704

3705
static void
3706
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3707
{
3708 3709 3710 3711
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3712 3713 3714 3715 3716 3717 3718 3719 3720

	/*
	 * 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.
	 */
3721
	update_load_avg(se, UPDATE_TG);
3722
	dequeue_entity_load_avg(cfs_rq, se);
3723

3724
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3725

P
Peter Zijlstra 已提交
3726
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3727

3728
	if (se != cfs_rq->curr)
3729
		__dequeue_entity(cfs_rq, se);
3730
	se->on_rq = 0;
3731
	account_entity_dequeue(cfs_rq, se);
3732 3733

	/*
3734 3735 3736 3737
	 * 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.
3738
	 */
3739
	if (!(flags & DEQUEUE_SLEEP))
3740
		se->vruntime -= cfs_rq->min_vruntime;
3741

3742 3743 3744
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3745
	update_cfs_shares(se);
3746 3747 3748 3749 3750 3751 3752 3753 3754

	/*
	 * 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);
3755 3756 3757 3758 3759
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3760
static void
I
Ingo Molnar 已提交
3761
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3762
{
3763
	unsigned long ideal_runtime, delta_exec;
3764 3765
	struct sched_entity *se;
	s64 delta;
3766

P
Peter Zijlstra 已提交
3767
	ideal_runtime = sched_slice(cfs_rq, curr);
3768
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3769
	if (delta_exec > ideal_runtime) {
3770
		resched_curr(rq_of(cfs_rq));
3771 3772 3773 3774 3775
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786
		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;

3787 3788
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3789

3790 3791
	if (delta < 0)
		return;
3792

3793
	if (delta > ideal_runtime)
3794
		resched_curr(rq_of(cfs_rq));
3795 3796
}

3797
static void
3798
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3799
{
3800 3801 3802 3803 3804 3805 3806
	/* '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.
		 */
3807
		update_stats_wait_end(cfs_rq, se);
3808
		__dequeue_entity(cfs_rq, se);
3809
		update_load_avg(se, UPDATE_TG);
3810 3811
	}

3812
	update_stats_curr_start(cfs_rq, se);
3813
	cfs_rq->curr = se;
3814

I
Ingo Molnar 已提交
3815 3816 3817 3818 3819
	/*
	 * 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):
	 */
3820
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3821 3822 3823
		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
3824
	}
3825

3826
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3827 3828
}

3829 3830 3831
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3832 3833 3834 3835 3836 3837 3838
/*
 * 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
 */
3839 3840
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3841
{
3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852
	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 */
3853

3854 3855 3856 3857 3858
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3859 3860 3861 3862 3863 3864 3865 3866 3867 3868
		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;
		}

3869 3870 3871
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3872

3873 3874 3875 3876 3877 3878
	/*
	 * 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;

3879 3880 3881 3882 3883 3884
	/*
	 * 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;

3885
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3886 3887

	return se;
3888 3889
}

3890
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3891

3892
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3893 3894 3895 3896 3897 3898
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3899
		update_curr(cfs_rq);
3900

3901 3902 3903
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3904
	check_spread(cfs_rq, prev);
3905

3906
	if (prev->on_rq) {
3907
		update_stats_wait_start(cfs_rq, prev);
3908 3909
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3910
		/* in !on_rq case, update occurred at dequeue */
3911
		update_load_avg(prev, 0);
3912
	}
3913
	cfs_rq->curr = NULL;
3914 3915
}

P
Peter Zijlstra 已提交
3916 3917
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3918 3919
{
	/*
3920
	 * Update run-time statistics of the 'current'.
3921
	 */
3922
	update_curr(cfs_rq);
3923

3924 3925 3926
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3927
	update_load_avg(curr, UPDATE_TG);
3928
	update_cfs_shares(curr);
3929

P
Peter Zijlstra 已提交
3930 3931 3932 3933 3934
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3935
	if (queued) {
3936
		resched_curr(rq_of(cfs_rq));
3937 3938
		return;
	}
P
Peter Zijlstra 已提交
3939 3940 3941 3942 3943 3944 3945 3946
	/*
	 * 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
3947
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3948
		check_preempt_tick(cfs_rq, curr);
3949 3950
}

3951 3952 3953 3954 3955 3956

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

#ifdef CONFIG_CFS_BANDWIDTH
3957 3958

#ifdef HAVE_JUMP_LABEL
3959
static struct static_key __cfs_bandwidth_used;
3960 3961 3962

static inline bool cfs_bandwidth_used(void)
{
3963
	return static_key_false(&__cfs_bandwidth_used);
3964 3965
}

3966
void cfs_bandwidth_usage_inc(void)
3967
{
3968 3969 3970 3971 3972 3973
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3974 3975 3976 3977 3978 3979 3980
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3981 3982
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3983 3984
#endif /* HAVE_JUMP_LABEL */

3985 3986 3987 3988 3989 3990 3991 3992
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3993 3994 3995 3996 3997 3998

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

P
Paul Turner 已提交
3999 4000 4001 4002 4003 4004 4005
/*
 * 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
 */
4006
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017
{
	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);
}

4018 4019 4020 4021 4022
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4023 4024 4025 4026
/* 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))
4027
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4028

4029
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4030 4031
}

4032 4033
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4034 4035 4036
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4037
	u64 amount = 0, min_amount, expires;
4038 4039 4040 4041 4042 4043 4044

	/* 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;
4045
	else {
P
Peter Zijlstra 已提交
4046
		start_cfs_bandwidth(cfs_b);
4047 4048 4049 4050 4051 4052

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4053
	}
P
Paul Turner 已提交
4054
	expires = cfs_b->runtime_expires;
4055 4056 4057
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4058 4059 4060 4061 4062 4063 4064
	/*
	 * 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;
4065 4066

	return cfs_rq->runtime_remaining > 0;
4067 4068
}

P
Paul Turner 已提交
4069 4070 4071 4072 4073
/*
 * 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)
4074
{
P
Paul Turner 已提交
4075 4076 4077
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4078
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4079 4080
		return;

P
Paul Turner 已提交
4081 4082 4083 4084 4085 4086 4087 4088 4089
	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
4090 4091 4092
	 * 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
4093 4094
	 */

4095
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
4096 4097 4098 4099 4100 4101 4102 4103
		/* 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;
	}
}

4104
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4105 4106
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4107
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4108 4109 4110
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4111 4112
		return;

4113 4114 4115 4116 4117
	/*
	 * 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))
4118
		resched_curr(rq_of(cfs_rq));
4119 4120
}

4121
static __always_inline
4122
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4123
{
4124
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4125 4126 4127 4128 4129
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4130 4131
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4132
	return cfs_bandwidth_used() && cfs_rq->throttled;
4133 4134
}

4135 4136 4137
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4138
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165
}

/*
 * 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) {
4166
		/* adjust cfs_rq_clock_task() */
4167
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4168
					     cfs_rq->throttled_clock_task;
4169 4170 4171 4172 4173 4174 4175 4176 4177 4178
	}

	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)];

4179 4180
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4181
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4182 4183 4184 4185 4186
	cfs_rq->throttle_count++;

	return 0;
}

4187
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4188 4189 4190 4191 4192
{
	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
4193
	bool empty;
4194 4195 4196

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

4197
	/* freeze hierarchy runnable averages while throttled */
4198 4199 4200
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217

	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)
4218
		sub_nr_running(rq, task_delta);
4219 4220

	cfs_rq->throttled = 1;
4221
	cfs_rq->throttled_clock = rq_clock(rq);
4222
	raw_spin_lock(&cfs_b->lock);
4223
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4224

4225 4226 4227 4228 4229
	/*
	 * 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
4230 4231 4232 4233 4234 4235 4236 4237

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

4238 4239 4240
	raw_spin_unlock(&cfs_b->lock);
}

4241
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4242 4243 4244 4245 4246 4247 4248
{
	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;

4249
	se = cfs_rq->tg->se[cpu_of(rq)];
4250 4251

	cfs_rq->throttled = 0;
4252 4253 4254

	update_rq_clock(rq);

4255
	raw_spin_lock(&cfs_b->lock);
4256
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4257 4258 4259
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4260 4261 4262
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280
	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)
4281
		add_nr_running(rq, task_delta);
4282 4283 4284

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4285
		resched_curr(rq);
4286 4287 4288 4289 4290 4291
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4292 4293
	u64 runtime;
	u64 starting_runtime = remaining;
4294 4295 4296 4297 4298

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4299
		struct rq_flags rf;
4300

4301
		rq_lock(rq, &rf);
4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317
		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:
4318
		rq_unlock(rq, &rf);
4319 4320 4321 4322 4323 4324

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

4325
	return starting_runtime - remaining;
4326 4327
}

4328 4329 4330 4331 4332 4333 4334 4335
/*
 * 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)
{
4336
	u64 runtime, runtime_expires;
4337
	int throttled;
4338 4339 4340

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4341
		goto out_deactivate;
4342

4343
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4344
	cfs_b->nr_periods += overrun;
4345

4346 4347 4348 4349 4350 4351
	/*
	 * 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
4352 4353 4354

	__refill_cfs_bandwidth_runtime(cfs_b);

4355 4356 4357
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4358
		return 0;
4359 4360
	}

4361 4362 4363
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4364 4365 4366
	runtime_expires = cfs_b->runtime_expires;

	/*
4367 4368 4369 4370 4371
	 * 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.
4372
	 */
4373 4374
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4375 4376 4377 4378 4379 4380 4381
		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);
4382 4383

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4384
	}
4385

4386 4387 4388 4389 4390 4391 4392
	/*
	 * 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;
4393

4394 4395 4396 4397
	return 0;

out_deactivate:
	return 1;
4398
}
4399

4400 4401 4402 4403 4404 4405 4406
/* 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;

4407 4408 4409 4410
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4411
 * hrtimer base being cleared by hrtimer_start. In the case of
4412 4413
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

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

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

	return 0;
}

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

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

P
Peter Zijlstra 已提交
4439 4440 4441
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470
}

/* 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)
{
4471 4472 4473
	if (!cfs_bandwidth_used())
		return;

4474
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489
		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 */
4490 4491 4492
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4493
		return;
4494
	}
4495

4496
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4497
		runtime = cfs_b->runtime;
4498

4499 4500 4501 4502 4503 4504 4505 4506 4507 4508
	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)
4509
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4510 4511 4512
	raw_spin_unlock(&cfs_b->lock);
}

4513 4514 4515 4516 4517 4518 4519
/*
 * 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)
{
4520 4521 4522
	if (!cfs_bandwidth_used())
		return;

4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536
	/* 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);
}

4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550
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;
4551
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4552 4553
}

4554
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4555
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4556
{
4557
	if (!cfs_bandwidth_used())
4558
		return false;
4559

4560
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4561
		return false;
4562 4563 4564 4565 4566 4567

	/*
	 * 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))
4568
		return true;
4569 4570

	throttle_cfs_rq(cfs_rq);
4571
	return true;
4572
}
4573 4574 4575 4576 4577

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
P
Peter Zijlstra 已提交
4578

4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590
	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;

4591
	raw_spin_lock(&cfs_b->lock);
4592
	for (;;) {
P
Peter Zijlstra 已提交
4593
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4594 4595 4596 4597 4598
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4599 4600
	if (idle)
		cfs_b->period_active = 0;
4601
	raw_spin_unlock(&cfs_b->lock);
4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613

	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);
P
Peter Zijlstra 已提交
4614
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625
	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);
}

P
Peter Zijlstra 已提交
4626
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4627
{
P
Peter Zijlstra 已提交
4628
	lockdep_assert_held(&cfs_b->lock);
4629

P
Peter Zijlstra 已提交
4630 4631 4632 4633 4634
	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);
	}
4635 4636 4637 4638
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4639 4640 4641 4642
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4643 4644 4645 4646
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4647 4648 4649 4650 4651 4652 4653 4654
/*
 * 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 */
4655 4656
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4657
	struct task_group *tg;
4658

4659 4660 4661 4662 4663 4664
	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)];
4665 4666 4667 4668 4669

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4670
	rcu_read_unlock();
4671 4672
}

4673
/* cpu offline callback */
4674
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4675
{
4676 4677 4678 4679 4680 4681 4682
	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)];
4683 4684 4685 4686 4687 4688 4689 4690

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4691
		cfs_rq->runtime_remaining = 1;
4692 4693 4694 4695 4696 4697
		/*
		 * 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;

4698 4699 4700
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
4701
	rcu_read_unlock();
4702 4703 4704
}

#else /* CONFIG_CFS_BANDWIDTH */
4705 4706
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4707
	return rq_clock_task(rq_of(cfs_rq));
4708 4709
}

4710
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4711
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4712
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4713
static inline void sync_throttle(struct task_group *tg, int cpu) {}
4714
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4715 4716 4717 4718 4719

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730

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;
}
4731 4732 4733 4734 4735

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) {}
4736 4737
#endif

4738 4739 4740 4741 4742
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) {}
4743
static inline void update_runtime_enabled(struct rq *rq) {}
4744
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4745 4746 4747

#endif /* CONFIG_CFS_BANDWIDTH */

4748 4749 4750 4751
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4752 4753 4754 4755 4756 4757
#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);

4758
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
4759

4760
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
4761 4762 4763 4764 4765 4766
		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)
4767
				resched_curr(rq);
P
Peter Zijlstra 已提交
4768 4769
			return;
		}
4770
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4771 4772
	}
}
4773 4774 4775 4776 4777 4778 4779 4780 4781 4782

/*
 * 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;

4783
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4784 4785 4786 4787 4788
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4789
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
4790 4791 4792 4793
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4794 4795 4796 4797

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4798 4799
#endif

4800 4801 4802 4803 4804
/*
 * 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:
 */
4805
static void
4806
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4807 4808
{
	struct cfs_rq *cfs_rq;
4809
	struct sched_entity *se = &p->se;
4810

4811 4812 4813 4814 4815 4816 4817 4818
	/*
	 * 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)
		cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT);

4819
	for_each_sched_entity(se) {
4820
		if (se->on_rq)
4821 4822
			break;
		cfs_rq = cfs_rq_of(se);
4823
		enqueue_entity(cfs_rq, se, flags);
4824 4825 4826 4827 4828 4829

		/*
		 * 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.
4830
		 */
4831 4832
		if (cfs_rq_throttled(cfs_rq))
			break;
4833
		cfs_rq->h_nr_running++;
4834

4835
		flags = ENQUEUE_WAKEUP;
4836
	}
P
Peter Zijlstra 已提交
4837

P
Peter Zijlstra 已提交
4838
	for_each_sched_entity(se) {
4839
		cfs_rq = cfs_rq_of(se);
4840
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4841

4842 4843 4844
		if (cfs_rq_throttled(cfs_rq))
			break;

4845
		update_load_avg(se, UPDATE_TG);
4846
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
4847 4848
	}

Y
Yuyang Du 已提交
4849
	if (!se)
4850
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4851

4852
	hrtick_update(rq);
4853 4854
}

4855 4856
static void set_next_buddy(struct sched_entity *se);

4857 4858 4859 4860 4861
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4862
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4863 4864
{
	struct cfs_rq *cfs_rq;
4865
	struct sched_entity *se = &p->se;
4866
	int task_sleep = flags & DEQUEUE_SLEEP;
4867 4868 4869

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4870
		dequeue_entity(cfs_rq, se, flags);
4871 4872 4873 4874 4875 4876 4877 4878 4879

		/*
		 * 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;
4880
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4881

4882
		/* Don't dequeue parent if it has other entities besides us */
4883
		if (cfs_rq->load.weight) {
4884 4885
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
4886 4887 4888 4889
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
4890 4891
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
4892
			break;
4893
		}
4894
		flags |= DEQUEUE_SLEEP;
4895
	}
P
Peter Zijlstra 已提交
4896

P
Peter Zijlstra 已提交
4897
	for_each_sched_entity(se) {
4898
		cfs_rq = cfs_rq_of(se);
4899
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4900

4901 4902 4903
		if (cfs_rq_throttled(cfs_rq))
			break;

4904
		update_load_avg(se, UPDATE_TG);
4905
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
4906 4907
	}

Y
Yuyang Du 已提交
4908
	if (!se)
4909
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4910

4911
	hrtick_update(rq);
4912 4913
}

4914
#ifdef CONFIG_SMP
4915 4916 4917 4918 4919

/* 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);

4920
#ifdef CONFIG_NO_HZ_COMMON
4921 4922 4923 4924 4925
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
4926
 * The exact cpuload calculated at every tick would be:
4927
 *
4928 4929 4930 4931 4932 4933 4934
 *   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
4935 4936 4937
 *
 * decay_load_missed() below does efficient calculation of
 *
4938 4939 4940 4941 4942 4943
 *   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())
4944
 *
4945
 * The calculation is approximated on a 128 point scale.
4946 4947
 */
#define DEGRADE_SHIFT		7
4948 4949 4950 4951 4952 4953 4954 4955 4956

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 }
};
4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985

/*
 * 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;
}
4986
#endif /* CONFIG_NO_HZ_COMMON */
4987

4988
/**
4989
 * __cpu_load_update - update the rq->cpu_load[] statistics
4990 4991 4992 4993
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
4994
 * Update rq->cpu_load[] statistics. This function is usually called every
4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020
 * 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
5021
 * term.
5022
 */
5023 5024
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5025
{
5026
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037
	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 */

5038
		old_load = this_rq->cpu_load[i];
5039
#ifdef CONFIG_NO_HZ_COMMON
5040
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5041 5042 5043 5044 5045 5046 5047 5048 5049
		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;
		}
5050
#endif
5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065
		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);
}

5066 5067 5068 5069 5070 5071
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

5072
#ifdef CONFIG_NO_HZ_COMMON
5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089
/*
 * 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)
5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100
{
	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.
		 */
5101
		cpu_load_update(this_rq, load, pending_updates);
5102 5103 5104
	}
}

5105 5106 5107 5108
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5109
static void cpu_load_update_idle(struct rq *this_rq)
5110 5111 5112 5113
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5114
	if (weighted_cpuload(cpu_of(this_rq)))
5115 5116
		return;

5117
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5118 5119 5120
}

/*
5121 5122 5123 5124
 * 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.
5125
 */
5126
void cpu_load_update_nohz_start(void)
5127 5128
{
	struct rq *this_rq = this_rq();
5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142

	/*
	 * 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.
	 */
	this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq));
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5143
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5144 5145
	struct rq *this_rq = this_rq();
	unsigned long load;
5146
	struct rq_flags rf;
5147 5148 5149 5150

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

5151
	load = weighted_cpuload(cpu_of(this_rq));
5152
	rq_lock(this_rq, &rf);
5153
	update_rq_clock(this_rq);
5154
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5155
	rq_unlock(this_rq, &rf);
5156
}
5157 5158 5159 5160 5161 5162 5163 5164
#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)
{
5165
#ifdef CONFIG_NO_HZ_COMMON
5166 5167
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5168
#endif
5169 5170
	cpu_load_update(this_rq, load, 1);
}
5171 5172 5173 5174

/*
 * Called from scheduler_tick()
 */
5175
void cpu_load_update_active(struct rq *this_rq)
5176
{
5177
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
5178 5179 5180 5181 5182

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5183 5184
}

5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217
/*
 * 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);
	unsigned long total = weighted_cpuload(cpu);

	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);
	unsigned long total = weighted_cpuload(cpu);

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

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

5218
static unsigned long capacity_of(int cpu)
5219
{
5220
	return cpu_rq(cpu)->cpu_capacity;
5221 5222
}

5223 5224 5225 5226 5227
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5228 5229 5230
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5231
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5232
	unsigned long load_avg = weighted_cpuload(cpu);
5233 5234

	if (nr_running)
5235
		return load_avg / nr_running;
5236 5237 5238 5239

	return 0;
}

5240
#ifdef CONFIG_FAIR_GROUP_SCHED
5241 5242 5243 5244 5245 5246
/*
 * effective_load() calculates the load change as seen from the root_task_group
 *
 * Adding load to a group doesn't make a group heavier, but can cause movement
 * of group shares between cpus. Assuming the shares were perfectly aligned one
 * can calculate the shift in shares.
5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289
 *
 * Calculate the effective load difference if @wl is added (subtracted) to @tg
 * on this @cpu and results in a total addition (subtraction) of @wg to the
 * total group weight.
 *
 * Given a runqueue weight distribution (rw_i) we can compute a shares
 * distribution (s_i) using:
 *
 *   s_i = rw_i / \Sum rw_j						(1)
 *
 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
 * shares distribution (s_i):
 *
 *   rw_i = {   2,   4,   1,   0 }
 *   s_i  = { 2/7, 4/7, 1/7,   0 }
 *
 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
 * task used to run on and the CPU the waker is running on), we need to
 * compute the effect of waking a task on either CPU and, in case of a sync
 * wakeup, compute the effect of the current task going to sleep.
 *
 * So for a change of @wl to the local @cpu with an overall group weight change
 * of @wl we can compute the new shares distribution (s'_i) using:
 *
 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)				(2)
 *
 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
 * differences in waking a task to CPU 0. The additional task changes the
 * weight and shares distributions like:
 *
 *   rw'_i = {   3,   4,   1,   0 }
 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
 *
 * We can then compute the difference in effective weight by using:
 *
 *   dw_i = S * (s'_i - s_i)						(3)
 *
 * Where 'S' is the group weight as seen by its parent.
 *
 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
 * 4/7) times the weight of the group.
5290
 */
P
Peter Zijlstra 已提交
5291
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
5292
{
P
Peter Zijlstra 已提交
5293
	struct sched_entity *se = tg->se[cpu];
5294

5295
	if (!tg->parent)	/* the trivial, non-cgroup case */
5296 5297
		return wl;

P
Peter Zijlstra 已提交
5298
	for_each_sched_entity(se) {
5299 5300
		struct cfs_rq *cfs_rq = se->my_q;
		long W, w = cfs_rq_load_avg(cfs_rq);
P
Peter Zijlstra 已提交
5301

5302
		tg = cfs_rq->tg;
5303

5304 5305 5306
		/*
		 * W = @wg + \Sum rw_j
		 */
5307 5308 5309 5310 5311
		W = wg + atomic_long_read(&tg->load_avg);

		/* Ensure \Sum rw_j >= rw_i */
		W -= cfs_rq->tg_load_avg_contrib;
		W += w;
P
Peter Zijlstra 已提交
5312

5313 5314 5315
		/*
		 * w = rw_i + @wl
		 */
5316
		w += wl;
5317

5318 5319 5320 5321
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
5322
			wl = (w * (long)scale_load_down(tg->shares)) / W;
5323
		else
5324
			wl = scale_load_down(tg->shares);
5325

5326 5327 5328 5329 5330
		/*
		 * Per the above, wl is the new se->load.weight value; since
		 * those are clipped to [MIN_SHARES, ...) do so now. See
		 * calc_cfs_shares().
		 */
5331 5332
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
5333 5334 5335 5336

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
5337
		wl -= se->avg.load_avg;
5338 5339 5340 5341 5342 5343 5344 5345

		/*
		 * Recursively apply this logic to all parent groups to compute
		 * the final effective load change on the root group. Since
		 * only the @tg group gets extra weight, all parent groups can
		 * only redistribute existing shares. @wl is the shift in shares
		 * resulting from this level per the above.
		 */
P
Peter Zijlstra 已提交
5346 5347
		wg = 0;
	}
5348

P
Peter Zijlstra 已提交
5349
	return wl;
5350 5351
}
#else
P
Peter Zijlstra 已提交
5352

5353
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
5354
{
5355
	return wl;
5356
}
P
Peter Zijlstra 已提交
5357

5358 5359
#endif

P
Peter Zijlstra 已提交
5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376
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
5377 5378
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5379
 *
M
Mike Galbraith 已提交
5380
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392
 * 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
5393
 */
5394 5395
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5396 5397
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5398
	int factor = this_cpu_read(sd_llc_size);
5399

M
Mike Galbraith 已提交
5400 5401 5402 5403 5404
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5405 5406
}

5407 5408
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
		       int prev_cpu, int sync)
5409
{
5410
	s64 this_load, load;
5411
	s64 this_eff_load, prev_eff_load;
5412
	int idx, this_cpu;
5413
	struct task_group *tg;
5414
	unsigned long weight;
5415
	int balanced;
5416

5417 5418 5419 5420
	idx	  = sd->wake_idx;
	this_cpu  = smp_processor_id();
	load	  = source_load(prev_cpu, idx);
	this_load = target_load(this_cpu, idx);
5421

5422 5423 5424 5425 5426
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
5427 5428
	if (sync) {
		tg = task_group(current);
5429
		weight = current->se.avg.load_avg;
5430

5431
		this_load += effective_load(tg, this_cpu, -weight, -weight);
5432 5433
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
5434

5435
	tg = task_group(p);
5436
	weight = p->se.avg.load_avg;
5437

5438 5439
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5440 5441 5442
	 * due to the sync cause above having dropped this_load to 0, we'll
	 * always have an imbalance, but there's really nothing you can do
	 * about that, so that's good too.
5443 5444 5445 5446
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
5447 5448
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
5449

5450 5451
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5452

5453
	if (this_load > 0) {
5454 5455 5456 5457
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5458
	}
5459

5460
	balanced = this_eff_load <= prev_eff_load;
5461

5462
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5463

5464 5465
	if (!balanced)
		return 0;
5466

5467 5468
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
5469 5470

	return 1;
5471 5472
}

5473 5474 5475 5476 5477 5478 5479 5480
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);
}

5481 5482 5483 5484 5485
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5486
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5487
		  int this_cpu, int sd_flag)
5488
{
5489
	struct sched_group *idlest = NULL, *group = sd->groups;
5490
	struct sched_group *most_spare_sg = NULL;
5491 5492
	unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0;
5493
	unsigned long most_spare = 0, this_spare = 0;
5494
	int load_idx = sd->forkexec_idx;
5495 5496 5497
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5498

5499 5500 5501
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5502
	do {
5503 5504
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5505 5506
		int local_group;
		int i;
5507

5508
		/* Skip over this group if it has no CPUs allowed */
5509
		if (!cpumask_intersects(sched_group_span(group),
5510
					&p->cpus_allowed))
5511 5512 5513
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5514
					       sched_group_span(group));
5515

5516 5517 5518 5519
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5520
		avg_load = 0;
5521
		runnable_load = 0;
5522
		max_spare_cap = 0;
5523

5524
		for_each_cpu(i, sched_group_span(group)) {
5525 5526 5527 5528 5529 5530
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5531 5532 5533
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5534 5535 5536 5537 5538

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5539 5540
		}

5541
		/* Adjust by relative CPU capacity of the group */
5542 5543 5544 5545
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5546 5547

		if (local_group) {
5548 5549
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5550 5551
			this_spare = max_spare_cap;
		} else {
5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566
			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;
5567 5568 5569 5570 5571 5572 5573
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5574 5575 5576
		}
	} while (group = group->next, group != sd->groups);

5577 5578 5579 5580 5581 5582
	/*
	 * 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.
5583 5584 5585 5586
	 *
	 * 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.
5587
	 */
5588 5589 5590
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5591
	if (this_spare > task_util(p) / 2 &&
5592
	    imbalance_scale*this_spare > 100*most_spare)
5593
		return NULL;
5594 5595

	if (most_spare > task_util(p) / 2)
5596 5597
		return most_spare_sg;

5598
skip_spare:
5599 5600 5601 5602
	if (!idlest)
		return NULL;

	if (min_runnable_load > (this_runnable_load + imbalance))
5603
		return NULL;
5604 5605 5606 5607 5608

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

5609 5610 5611 5612 5613 5614 5615 5616 5617 5618
	return idlest;
}

/*
 * find_idlest_cpu - find the idlest cpu among the cpus in group.
 */
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
	unsigned long load, min_load = ULONG_MAX;
5619 5620 5621 5622
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5623 5624
	int i;

5625 5626
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5627
		return cpumask_first(sched_group_span(group));
5628

5629
	/* Traverse only the allowed CPUs */
5630
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652
		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;
			}
5653
		} else if (shallowest_idle_cpu == -1) {
5654 5655 5656 5657 5658
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5659 5660 5661
		}
	}

5662
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5663
}
5664

5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691 5692 5693
#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
5694
void __update_idle_core(struct rq *rq)
5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723
{
	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);
5724
	int core, cpu;
5725

P
Peter Zijlstra 已提交
5726 5727 5728
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5729 5730 5731
	if (!test_idle_cores(target, false))
		return -1;

5732
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
5733

5734
	for_each_cpu_wrap(core, cpus, target) {
5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761
		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
5762 5763 5764
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5765
	for_each_cpu(cpu, cpu_smt_mask(target)) {
5766
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792
			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).
5793
 */
5794 5795
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
5796 5797
	struct sched_domain *this_sd;
	u64 avg_cost, avg_idle = this_rq()->avg_idle;
5798 5799
	u64 time, cost;
	s64 delta;
5800
	int cpu;
5801

5802 5803 5804 5805 5806 5807
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

	avg_cost = this_sd->avg_scan_cost;

5808 5809 5810 5811
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
5812
	if (sched_feat(SIS_AVG_CPU) && (avg_idle / 512) < avg_cost)
5813 5814 5815 5816
		return -1;

	time = local_clock();

5817
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
5818
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833
			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.
5834
 */
5835
static int select_idle_sibling(struct task_struct *p, int prev, int target)
5836
{
5837
	struct sched_domain *sd;
5838
	int i;
5839

5840 5841
	if (idle_cpu(target))
		return target;
5842 5843

	/*
5844
	 * If the previous cpu is cache affine and idle, don't be stupid.
5845
	 */
5846 5847
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
5848

5849
	sd = rcu_dereference(per_cpu(sd_llc, target));
5850 5851
	if (!sd)
		return target;
5852

5853 5854 5855
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
5856

5857 5858 5859 5860 5861 5862 5863
	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;
5864

5865 5866
	return target;
}
5867

5868
/*
5869
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5870
 * tasks. The unit of the return value must be the one of capacity so we can
5871 5872
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892
 *
 * 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).
5893
 */
5894
static int cpu_util(int cpu)
5895
{
5896
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5897 5898
	unsigned long capacity = capacity_orig_of(cpu);

5899
	return (util >= capacity) ? capacity : util;
5900
}
5901

5902 5903 5904 5905 5906
static inline int task_util(struct task_struct *p)
{
	return p->se.avg.util_avg;
}

5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924
/*
 * 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;
}

5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942
/*
 * 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;

5943 5944 5945
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

5946 5947 5948
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

5949
/*
5950 5951 5952
 * 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.
5953
 *
5954 5955
 * 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.
5956
 *
5957
 * Returns the target cpu number.
5958 5959 5960
 *
 * preempt must be disabled.
 */
5961
static int
5962
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5963
{
5964
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5965
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5966
	int new_cpu = prev_cpu;
5967
	int want_affine = 0;
5968
	int sync = wake_flags & WF_SYNC;
5969

P
Peter Zijlstra 已提交
5970 5971
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
5972
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
5973
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
5974
	}
5975

5976
	rcu_read_lock();
5977
	for_each_domain(cpu, tmp) {
5978
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5979
			break;
5980

5981
		/*
5982 5983
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5984
		 */
5985 5986 5987
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5988
			break;
5989
		}
5990

5991
		if (tmp->flags & sd_flag)
5992
			sd = tmp;
M
Mike Galbraith 已提交
5993 5994
		else if (!want_affine)
			break;
5995 5996
	}

M
Mike Galbraith 已提交
5997 5998
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
5999
		if (cpu != prev_cpu && wake_affine(affine_sd, p, prev_cpu, sync))
M
Mike Galbraith 已提交
6000
			new_cpu = cpu;
6001
	}
6002

M
Mike Galbraith 已提交
6003 6004
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
6005
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
6006 6007

	} else while (sd) {
6008
		struct sched_group *group;
6009
		int weight;
6010

6011
		if (!(sd->flags & sd_flag)) {
6012 6013 6014
			sd = sd->child;
			continue;
		}
6015

6016
		group = find_idlest_group(sd, p, cpu, sd_flag);
6017 6018 6019 6020
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
6021

6022
		new_cpu = find_idlest_cpu(group, p, cpu);
6023 6024 6025 6026
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
6027
		}
6028 6029 6030

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
6031
		weight = sd->span_weight;
6032 6033
		sd = NULL;
		for_each_domain(cpu, tmp) {
6034
			if (weight <= tmp->span_weight)
6035
				break;
6036
			if (tmp->flags & sd_flag)
6037 6038 6039
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
6040
	}
6041
	rcu_read_unlock();
6042

6043
	return new_cpu;
6044
}
6045 6046 6047 6048

/*
 * 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
6049
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6050
 */
6051
static void migrate_task_rq_fair(struct task_struct *p)
6052
{
6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078
	/*
	 * 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;
	}

6079
	/*
6080 6081 6082 6083 6084
	 * 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.
6085
	 */
6086 6087 6088 6089
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6090 6091

	/* We have migrated, no longer consider this task hot */
6092
	p->se.exec_start = 0;
6093
}
6094 6095 6096 6097 6098

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6099 6100
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
6101 6102
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6103 6104 6105 6106
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6107 6108
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6109 6110 6111 6112 6113 6114 6115 6116 6117
	 *
	 * 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.
6118
	 */
6119
	return calc_delta_fair(gran, se);
6120 6121
}

6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143
/*
 * 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
6144
	gran = wakeup_gran(curr, se);
6145 6146 6147 6148 6149 6150
	if (vdiff > gran)
		return 1;

	return 0;
}

6151 6152
static void set_last_buddy(struct sched_entity *se)
{
6153 6154 6155 6156 6157
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
6158 6159 6160 6161
}

static void set_next_buddy(struct sched_entity *se)
{
6162 6163 6164 6165 6166
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
6167 6168
}

6169 6170
static void set_skip_buddy(struct sched_entity *se)
{
6171 6172
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6173 6174
}

6175 6176 6177
/*
 * Preempt the current task with a newly woken task if needed:
 */
6178
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6179 6180
{
	struct task_struct *curr = rq->curr;
6181
	struct sched_entity *se = &curr->se, *pse = &p->se;
6182
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6183
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6184
	int next_buddy_marked = 0;
6185

I
Ingo Molnar 已提交
6186 6187 6188
	if (unlikely(se == pse))
		return;

6189
	/*
6190
	 * This is possible from callers such as attach_tasks(), in which we
6191 6192 6193 6194 6195 6196 6197
	 * 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;

6198
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6199
		set_next_buddy(pse);
6200 6201
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6202

6203 6204 6205
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6206 6207 6208 6209 6210 6211
	 *
	 * 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.
6212 6213 6214 6215
	 */
	if (test_tsk_need_resched(curr))
		return;

6216 6217 6218 6219 6220
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6221
	/*
6222 6223
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6224
	 */
6225
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6226
		return;
6227

6228
	find_matching_se(&se, &pse);
6229
	update_curr(cfs_rq_of(se));
6230
	BUG_ON(!pse);
6231 6232 6233 6234 6235 6236 6237
	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);
6238
		goto preempt;
6239
	}
6240

6241
	return;
6242

6243
preempt:
6244
	resched_curr(rq);
6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258
	/*
	 * 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);
6259 6260
}

6261
static struct task_struct *
6262
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6263 6264 6265
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6266
	struct task_struct *p;
6267
	int new_tasks;
6268

6269
again:
6270 6271
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
6272
		goto idle;
6273

6274
	if (prev->sched_class != &fair_sched_class)
6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293
		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.
		 */
6294 6295 6296 6297 6298
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6299

6300 6301 6302 6303 6304 6305 6306 6307 6308
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
			 * Therefore the 'simple' nr_running test will indeed
			 * be correct.
			 */
			if (unlikely(check_cfs_rq_runtime(cfs_rq)))
				goto simple;
		}
6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348

		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);
	}

	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);

	return p;
simple:
	cfs_rq = &rq->cfs;
#endif
6349

6350
	if (!cfs_rq->nr_running)
6351
		goto idle;
6352

6353
	put_prev_task(rq, prev);
6354

6355
	do {
6356
		se = pick_next_entity(cfs_rq, NULL);
6357
		set_next_entity(cfs_rq, se);
6358 6359 6360
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6361
	p = task_of(se);
6362

6363 6364
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6365 6366

	return p;
6367 6368

idle:
6369 6370
	new_tasks = idle_balance(rq, rf);

6371 6372 6373 6374 6375
	/*
	 * 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.
	 */
6376
	if (new_tasks < 0)
6377 6378
		return RETRY_TASK;

6379
	if (new_tasks > 0)
6380 6381 6382
		goto again;

	return NULL;
6383 6384 6385 6386 6387
}

/*
 * Account for a descheduled task:
 */
6388
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6389 6390 6391 6392 6393 6394
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6395
		put_prev_entity(cfs_rq, se);
6396 6397 6398
	}
}

6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423
/*
 * 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);
6424 6425 6426 6427 6428
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6429
		rq_clock_skip_update(rq, true);
6430 6431 6432 6433 6434
	}

	set_skip_buddy(se);
}

6435 6436 6437 6438
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6439 6440
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6441 6442 6443 6444 6445 6446 6447 6448 6449 6450
		return false;

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

	yield_task_fair(rq);

	return true;
}

6451
#ifdef CONFIG_SMP
6452
/**************************************************
P
Peter Zijlstra 已提交
6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468
 * 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
6469
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6470 6471 6472 6473 6474 6475
 *
 * 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)
 *
6476
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
6477 6478 6479 6480 6481 6482
 * 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):
 *
6483
 *   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
6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521
 *
 * 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:
 *
6522
 *             log_2 n
P
Peter Zijlstra 已提交
6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567
 *   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.]
6568
 */
6569

6570 6571
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6572 6573
enum fbq_type { regular, remote, all };

6574
#define LBF_ALL_PINNED	0x01
6575
#define LBF_NEED_BREAK	0x02
6576 6577
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6578 6579 6580 6581 6582

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6583
	int			src_cpu;
6584 6585 6586 6587

	int			dst_cpu;
	struct rq		*dst_rq;

6588 6589
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6590
	enum cpu_idle_type	idle;
6591
	long			imbalance;
6592 6593 6594
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6595
	unsigned int		flags;
6596 6597 6598 6599

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6600 6601

	enum fbq_type		fbq_type;
6602
	struct list_head	tasks;
6603 6604
};

6605 6606 6607
/*
 * Is this task likely cache-hot:
 */
6608
static int task_hot(struct task_struct *p, struct lb_env *env)
6609 6610 6611
{
	s64 delta;

6612 6613
	lockdep_assert_held(&env->src_rq->lock);

6614 6615 6616 6617 6618 6619 6620 6621 6622
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
6623
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6624 6625 6626 6627 6628 6629 6630 6631 6632
			(&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;

6633
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6634 6635 6636 6637

	return delta < (s64)sysctl_sched_migration_cost;
}

6638
#ifdef CONFIG_NUMA_BALANCING
6639
/*
6640 6641 6642
 * 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.
6643
 */
6644
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6645
{
6646
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6647
	unsigned long src_faults, dst_faults;
6648 6649
	int src_nid, dst_nid;

6650
	if (!static_branch_likely(&sched_numa_balancing))
6651 6652
		return -1;

6653
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6654
		return -1;
6655 6656 6657 6658

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

6659
	if (src_nid == dst_nid)
6660
		return -1;
6661

6662 6663 6664 6665 6666 6667 6668
	/* 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;
	}
6669

6670 6671
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6672
		return 0;
6673

6674 6675 6676 6677 6678 6679
	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);
6680 6681
	}

6682
	return dst_faults < src_faults;
6683 6684
}

6685
#else
6686
static inline int migrate_degrades_locality(struct task_struct *p,
6687 6688
					     struct lb_env *env)
{
6689
	return -1;
6690
}
6691 6692
#endif

6693 6694 6695 6696
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6697
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6698
{
6699
	int tsk_cache_hot;
6700 6701 6702

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

6703 6704
	/*
	 * We do not migrate tasks that are:
6705
	 * 1) throttled_lb_pair, or
6706
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6707 6708
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6709
	 */
6710 6711 6712
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6713
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
6714
		int cpu;
6715

6716
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
6717

6718 6719
		env->flags |= LBF_SOME_PINNED;

6720 6721 6722 6723 6724 6725 6726 6727
		/*
		 * 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.
		 *
		 * Also avoid computing new_dst_cpu if we have already computed
		 * one in current iteration.
		 */
6728
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6729 6730
			return 0;

6731 6732
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6733
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
6734
				env->flags |= LBF_DST_PINNED;
6735 6736 6737
				env->new_dst_cpu = cpu;
				break;
			}
6738
		}
6739

6740 6741
		return 0;
	}
6742 6743

	/* Record that we found atleast one task that could run on dst_cpu */
6744
	env->flags &= ~LBF_ALL_PINNED;
6745

6746
	if (task_running(env->src_rq, p)) {
6747
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
6748 6749 6750 6751 6752
		return 0;
	}

	/*
	 * Aggressive migration if:
6753 6754 6755
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6756
	 */
6757 6758 6759
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6760

6761
	if (tsk_cache_hot <= 0 ||
6762
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6763
		if (tsk_cache_hot == 1) {
6764 6765
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
6766
		}
6767 6768 6769
		return 1;
	}

6770
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
6771
	return 0;
6772 6773
}

6774
/*
6775 6776 6777 6778 6779 6780 6781
 * 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;
6782
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
6783 6784 6785
	set_task_cpu(p, env->dst_cpu);
}

6786
/*
6787
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6788 6789
 * part of active balancing operations within "domain".
 *
6790
 * Returns a task if successful and NULL otherwise.
6791
 */
6792
static struct task_struct *detach_one_task(struct lb_env *env)
6793 6794 6795
{
	struct task_struct *p, *n;

6796 6797
	lockdep_assert_held(&env->src_rq->lock);

6798 6799 6800
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6801

6802
		detach_task(p, env);
6803

6804
		/*
6805
		 * Right now, this is only the second place where
6806
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6807
		 * so we can safely collect stats here rather than
6808
		 * inside detach_tasks().
6809
		 */
6810
		schedstat_inc(env->sd->lb_gained[env->idle]);
6811
		return p;
6812
	}
6813
	return NULL;
6814 6815
}

6816 6817
static const unsigned int sched_nr_migrate_break = 32;

6818
/*
6819 6820
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6821
 *
6822
 * Returns number of detached tasks if successful and 0 otherwise.
6823
 */
6824
static int detach_tasks(struct lb_env *env)
6825
{
6826 6827
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6828
	unsigned long load;
6829 6830 6831
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6832

6833
	if (env->imbalance <= 0)
6834
		return 0;
6835

6836
	while (!list_empty(tasks)) {
6837 6838 6839 6840 6841 6842 6843
		/*
		 * 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;

6844
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6845

6846 6847
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6848
		if (env->loop > env->loop_max)
6849
			break;
6850 6851

		/* take a breather every nr_migrate tasks */
6852
		if (env->loop > env->loop_break) {
6853
			env->loop_break += sched_nr_migrate_break;
6854
			env->flags |= LBF_NEED_BREAK;
6855
			break;
6856
		}
6857

6858
		if (!can_migrate_task(p, env))
6859 6860 6861
			goto next;

		load = task_h_load(p);
6862

6863
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6864 6865
			goto next;

6866
		if ((load / 2) > env->imbalance)
6867
			goto next;
6868

6869 6870 6871 6872
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6873
		env->imbalance -= load;
6874 6875

#ifdef CONFIG_PREEMPT
6876 6877
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6878
		 * kernels will stop after the first task is detached to minimize
6879 6880
		 * the critical section.
		 */
6881
		if (env->idle == CPU_NEWLY_IDLE)
6882
			break;
6883 6884
#endif

6885 6886 6887 6888
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6889
		if (env->imbalance <= 0)
6890
			break;
6891 6892 6893

		continue;
next:
6894
		list_move_tail(&p->se.group_node, tasks);
6895
	}
6896

6897
	/*
6898 6899 6900
	 * 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().
6901
	 */
6902
	schedstat_add(env->sd->lb_gained[env->idle], detached);
6903

6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914
	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);
6915
	activate_task(rq, p, ENQUEUE_NOCLOCK);
6916
	p->on_rq = TASK_ON_RQ_QUEUED;
6917 6918 6919 6920 6921 6922 6923 6924 6925
	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)
{
6926 6927 6928
	struct rq_flags rf;

	rq_lock(rq, &rf);
6929
	update_rq_clock(rq);
6930
	attach_task(rq, p);
6931
	rq_unlock(rq, &rf);
6932 6933 6934 6935 6936 6937 6938 6939 6940 6941
}

/*
 * 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;
6942
	struct rq_flags rf;
6943

6944
	rq_lock(env->dst_rq, &rf);
6945
	update_rq_clock(env->dst_rq);
6946 6947 6948 6949

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
6950

6951 6952 6953
		attach_task(env->dst_rq, p);
	}

6954
	rq_unlock(env->dst_rq, &rf);
6955 6956
}

P
Peter Zijlstra 已提交
6957
#ifdef CONFIG_FAIR_GROUP_SCHED
6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975

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;

	if (cfs_rq->runnable_load_sum)
		return false;

	return true;
}

6976
static void update_blocked_averages(int cpu)
6977 6978
{
	struct rq *rq = cpu_rq(cpu);
6979
	struct cfs_rq *cfs_rq, *pos;
6980
	struct rq_flags rf;
6981

6982
	rq_lock_irqsave(rq, &rf);
6983
	update_rq_clock(rq);
6984

6985 6986 6987 6988
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6989
	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
6990 6991
		struct sched_entity *se;

6992 6993 6994
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6995

6996
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6997
			update_tg_load_avg(cfs_rq, 0);
6998

6999 7000 7001 7002
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
			update_load_avg(se, 0);
7003 7004 7005 7006 7007 7008 7009

		/*
		 * 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);
7010
	}
7011
	rq_unlock_irqrestore(rq, &rf);
7012 7013
}

7014
/*
7015
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7016 7017 7018
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7019
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7020
{
7021 7022
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7023
	unsigned long now = jiffies;
7024
	unsigned long load;
7025

7026
	if (cfs_rq->last_h_load_update == now)
7027 7028
		return;

7029 7030 7031 7032 7033 7034 7035
	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;
	}
7036

7037
	if (!se) {
7038
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7039 7040 7041 7042 7043
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
7044 7045
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7046 7047 7048 7049
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7050 7051
}

7052
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7053
{
7054
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7055

7056
	update_cfs_rq_h_load(cfs_rq);
7057
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7058
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7059 7060
}
#else
7061
static inline void update_blocked_averages(int cpu)
7062
{
7063 7064
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7065
	struct rq_flags rf;
7066

7067
	rq_lock_irqsave(rq, &rf);
7068
	update_rq_clock(rq);
7069
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
7070
	rq_unlock_irqrestore(rq, &rf);
7071 7072
}

7073
static unsigned long task_h_load(struct task_struct *p)
7074
{
7075
	return p->se.avg.load_avg;
7076
}
P
Peter Zijlstra 已提交
7077
#endif
7078 7079

/********** Helpers for find_busiest_group ************************/
7080 7081 7082 7083 7084 7085 7086

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

7087 7088 7089 7090 7091 7092 7093
/*
 * 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
7094
	unsigned long load_per_task;
7095
	unsigned long group_capacity;
7096
	unsigned long group_util; /* Total utilization of the group */
7097 7098 7099
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7100
	enum group_type group_type;
7101
	int group_no_capacity;
7102 7103 7104 7105
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7106 7107
};

J
Joonsoo Kim 已提交
7108 7109 7110 7111 7112 7113 7114 7115
/*
 * 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 */
	unsigned long total_load;	/* Total load of all groups in sd */
7116
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7117 7118 7119
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7120
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7121 7122
};

7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134
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,
		.total_load = 0UL,
7135
		.total_capacity = 0UL,
7136 7137
		.busiest_stat = {
			.avg_load = 0UL,
7138 7139
			.sum_nr_running = 0,
			.group_type = group_other,
7140 7141 7142 7143
		},
	};
}

7144 7145 7146
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7147
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7148 7149
 *
 * Return: The load index.
7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169 7170 7171
 */
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;
}

7172
static unsigned long scale_rt_capacity(int cpu)
7173 7174
{
	struct rq *rq = cpu_rq(cpu);
7175
	u64 total, used, age_stamp, avg;
7176
	s64 delta;
7177

7178 7179 7180 7181
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
7182 7183
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
7184
	delta = __rq_clock_broken(rq) - age_stamp;
7185

7186 7187 7188 7189
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
7190

7191
	used = div_u64(avg, total);
7192

7193 7194
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
7195

7196
	return 1;
7197 7198
}

7199
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7200
{
7201
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7202 7203
	struct sched_group *sdg = sd->groups;

7204
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7205

7206
	capacity *= scale_rt_capacity(cpu);
7207
	capacity >>= SCHED_CAPACITY_SHIFT;
7208

7209 7210
	if (!capacity)
		capacity = 1;
7211

7212 7213
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7214
	sdg->sgc->min_capacity = capacity;
7215 7216
}

7217
void update_group_capacity(struct sched_domain *sd, int cpu)
7218 7219 7220
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7221
	unsigned long capacity, min_capacity;
7222 7223 7224 7225
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7226
	sdg->sgc->next_update = jiffies + interval;
7227 7228

	if (!child) {
7229
		update_cpu_capacity(sd, cpu);
7230 7231 7232
		return;
	}

7233
	capacity = 0;
7234
	min_capacity = ULONG_MAX;
7235

P
Peter Zijlstra 已提交
7236 7237 7238 7239 7240 7241
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7242
		for_each_cpu(cpu, sched_group_span(sdg)) {
7243
			struct sched_group_capacity *sgc;
7244
			struct rq *rq = cpu_rq(cpu);
7245

7246
			/*
7247
			 * build_sched_domains() -> init_sched_groups_capacity()
7248 7249 7250
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7251 7252
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7253
			 *
7254
			 * This avoids capacity from being 0 and
7255 7256 7257
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7258
				capacity += capacity_of(cpu);
7259 7260 7261
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7262
			}
7263

7264
			min_capacity = min(capacity, min_capacity);
7265
		}
P
Peter Zijlstra 已提交
7266 7267 7268 7269
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7270
		 */
P
Peter Zijlstra 已提交
7271 7272 7273

		group = child->groups;
		do {
7274 7275 7276 7277
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7278 7279 7280
			group = group->next;
		} while (group != child->groups);
	}
7281

7282
	sdg->sgc->capacity = capacity;
7283
	sdg->sgc->min_capacity = min_capacity;
7284 7285
}

7286
/*
7287 7288 7289
 * 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
7290 7291
 */
static inline int
7292
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7293
{
7294 7295
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7296 7297
}

7298 7299
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7300
 * groups is inadequate due to ->cpus_allowed constraints.
7301 7302 7303 7304 7305
 *
 * 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:
 *
7306 7307
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7308 7309 7310 7311 7312 7313
 *
 * 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
7314 7315
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7316 7317
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7318
 * update_sd_pick_busiest(). And calculate_imbalance() and
7319
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7320 7321 7322 7323 7324 7325 7326
 * 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.
 */

7327
static inline int sg_imbalanced(struct sched_group *group)
7328
{
7329
	return group->sgc->imbalance;
7330 7331
}

7332
/*
7333 7334 7335
 * 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
7336 7337
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7338 7339 7340 7341 7342
 * 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.
7343
 */
7344 7345
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7346
{
7347 7348
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7349

7350
	if ((sgs->group_capacity * 100) >
7351
			(sgs->group_util * env->sd->imbalance_pct))
7352
		return true;
7353

7354 7355 7356 7357 7358 7359 7360 7361 7362 7363 7364 7365 7366 7367 7368 7369
	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;
7370

7371
	if ((sgs->group_capacity * 100) <
7372
			(sgs->group_util * env->sd->imbalance_pct))
7373
		return true;
7374

7375
	return false;
7376 7377
}

7378 7379 7380 7381 7382 7383 7384 7385 7386 7387 7388
/*
 * 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;
}

7389 7390 7391
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7392
{
7393
	if (sgs->group_no_capacity)
7394 7395 7396 7397 7398 7399 7400 7401
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7402 7403
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7404
 * @env: The load balancing environment.
7405 7406 7407 7408
 * @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.
7409
 * @overload: Indicate more than one runnable task for any CPU.
7410
 */
7411 7412
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7413 7414
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7415
{
7416
	unsigned long load;
7417
	int i, nr_running;
7418

7419 7420
	memset(sgs, 0, sizeof(*sgs));

7421
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7422 7423 7424
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
7425
		if (local_group)
7426
			load = target_load(i, load_idx);
7427
		else
7428 7429 7430
			load = source_load(i, load_idx);

		sgs->group_load += load;
7431
		sgs->group_util += cpu_util(i);
7432
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7433

7434 7435
		nr_running = rq->nr_running;
		if (nr_running > 1)
7436 7437
			*overload = true;

7438 7439 7440 7441
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7442
		sgs->sum_weighted_load += weighted_cpuload(i);
7443 7444 7445 7446
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7447
			sgs->idle_cpus++;
7448 7449
	}

7450 7451
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7452
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7453

7454
	if (sgs->sum_nr_running)
7455
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7456

7457
	sgs->group_weight = group->group_weight;
7458

7459
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7460
	sgs->group_type = group_classify(group, sgs);
7461 7462
}

7463 7464
/**
 * update_sd_pick_busiest - return 1 on busiest group
7465
 * @env: The load balancing environment.
7466 7467
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7468
 * @sgs: sched_group statistics
7469 7470 7471
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7472 7473 7474
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7475
 */
7476
static bool update_sd_pick_busiest(struct lb_env *env,
7477 7478
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7479
				   struct sg_lb_stats *sgs)
7480
{
7481
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7482

7483
	if (sgs->group_type > busiest->group_type)
7484 7485
		return true;

7486 7487 7488 7489 7490 7491
	if (sgs->group_type < busiest->group_type)
		return false;

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

7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505
	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:
7506 7507
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7508 7509
		return true;

7510 7511 7512
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
7513
	/*
T
Tim Chen 已提交
7514 7515 7516
	 * 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.
7517
	 */
T
Tim Chen 已提交
7518 7519
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7520 7521 7522
		if (!sds->busiest)
			return true;

T
Tim Chen 已提交
7523 7524 7525
		/* Prefer to move from lowest priority cpu's work */
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7526 7527 7528 7529 7530 7531
			return true;
	}

	return false;
}

7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558 7559 7560 7561
#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 */

7562
/**
7563
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7564
 * @env: The load balancing environment.
7565 7566
 * @sds: variable to hold the statistics for this sched_domain.
 */
7567
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7568
{
7569 7570
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7571
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7572
	struct sg_lb_stats tmp_sgs;
7573
	int load_idx, prefer_sibling = 0;
7574
	bool overload = false;
7575 7576 7577 7578

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

7579
	load_idx = get_sd_load_idx(env->sd, env->idle);
7580 7581

	do {
J
Joonsoo Kim 已提交
7582
		struct sg_lb_stats *sgs = &tmp_sgs;
7583 7584
		int local_group;

7585
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7586 7587
		if (local_group) {
			sds->local = sg;
7588
			sgs = local;
7589 7590

			if (env->idle != CPU_NEWLY_IDLE ||
7591 7592
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7593
		}
7594

7595 7596
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7597

7598 7599 7600
		if (local_group)
			goto next_group;

7601 7602
		/*
		 * In case the child domain prefers tasks go to siblings
7603
		 * first, lower the sg capacity so that we'll try
7604 7605
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7606 7607 7608 7609
		 * 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).
7610
		 */
7611
		if (prefer_sibling && sds->local &&
7612 7613
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7614
			sgs->group_no_capacity = 1;
7615
			sgs->group_type = group_classify(sg, sgs);
7616
		}
7617

7618
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7619
			sds->busiest = sg;
J
Joonsoo Kim 已提交
7620
			sds->busiest_stat = *sgs;
7621 7622
		}

7623 7624 7625
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
7626
		sds->total_capacity += sgs->group_capacity;
7627

7628
		sg = sg->next;
7629
	} while (sg != env->sd->groups);
7630 7631 7632

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7633 7634 7635 7636 7637 7638 7639

	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;
	}

7640 7641 7642 7643
}

/**
 * check_asym_packing - Check to see if the group is packed into the
7644
 *			sched domain.
7645 7646 7647 7648 7649 7650 7651 7652 7653 7654 7655 7656 7657 7658
 *
 * 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.
 *
7659
 * Return: 1 when packing is required and a task should be moved to
7660 7661
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
7662
 * @env: The load balancing environment.
7663 7664
 * @sds: Statistics of the sched_domain which is to be packed
 */
7665
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7666 7667 7668
{
	int busiest_cpu;

7669
	if (!(env->sd->flags & SD_ASYM_PACKING))
7670 7671
		return 0;

7672 7673 7674
	if (env->idle == CPU_NOT_IDLE)
		return 0;

7675 7676 7677
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
7678 7679
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
7680 7681
		return 0;

7682
	env->imbalance = DIV_ROUND_CLOSEST(
7683
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7684
		SCHED_CAPACITY_SCALE);
7685

7686
	return 1;
7687 7688 7689 7690 7691 7692
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
7693
 * @env: The load balancing environment.
7694 7695
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
7696 7697
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7698
{
7699
	unsigned long tmp, capa_now = 0, capa_move = 0;
7700
	unsigned int imbn = 2;
7701
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
7702
	struct sg_lb_stats *local, *busiest;
7703

J
Joonsoo Kim 已提交
7704 7705
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7706

J
Joonsoo Kim 已提交
7707 7708 7709 7710
	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;
7711

J
Joonsoo Kim 已提交
7712
	scaled_busy_load_per_task =
7713
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7714
		busiest->group_capacity;
J
Joonsoo Kim 已提交
7715

7716 7717
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
7718
		env->imbalance = busiest->load_per_task;
7719 7720 7721 7722 7723
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
7724
	 * however we may be able to increase total CPU capacity used by
7725 7726 7727
	 * moving them.
	 */

7728
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
7729
			min(busiest->load_per_task, busiest->avg_load);
7730
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
7731
			min(local->load_per_task, local->avg_load);
7732
	capa_now /= SCHED_CAPACITY_SCALE;
7733 7734

	/* Amount of load we'd subtract */
7735
	if (busiest->avg_load > scaled_busy_load_per_task) {
7736
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
7737
			    min(busiest->load_per_task,
7738
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
7739
	}
7740 7741

	/* Amount of load we'd add */
7742
	if (busiest->avg_load * busiest->group_capacity <
7743
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7744 7745
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
7746
	} else {
7747
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7748
		      local->group_capacity;
J
Joonsoo Kim 已提交
7749
	}
7750
	capa_move += local->group_capacity *
7751
		    min(local->load_per_task, local->avg_load + tmp);
7752
	capa_move /= SCHED_CAPACITY_SCALE;
7753 7754

	/* Move if we gain throughput */
7755
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
7756
		env->imbalance = busiest->load_per_task;
7757 7758 7759 7760 7761
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
7762
 * @env: load balance environment
7763 7764
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
7765
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7766
{
7767
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
7768 7769 7770 7771
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7772

7773
	if (busiest->group_type == group_imbalanced) {
7774 7775 7776 7777
		/*
		 * 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
7778 7779
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
7780 7781
	}

7782
	/*
7783 7784 7785 7786
	 * 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:
7787
	 */
7788 7789
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7790 7791
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7792 7793
	}

7794 7795 7796 7797 7798
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7799
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7800
		if (load_above_capacity > busiest->group_capacity) {
7801
			load_above_capacity -= busiest->group_capacity;
7802
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
7803 7804
			load_above_capacity /= busiest->group_capacity;
		} else
7805
			load_above_capacity = ~0UL;
7806 7807 7808 7809 7810 7811
	}

	/*
	 * 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,
7812 7813
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
7814
	 */
7815
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7816 7817

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7818
	env->imbalance = min(
7819 7820
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
7821
	) / SCHED_CAPACITY_SCALE;
7822 7823 7824

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
7825
	 * there is no guarantee that any tasks will be moved so we'll have
7826 7827 7828
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7829
	if (env->imbalance < busiest->load_per_task)
7830
		return fix_small_imbalance(env, sds);
7831
}
7832

7833 7834 7835 7836
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
7837
 * if there is an imbalance.
7838 7839 7840 7841
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
7842
 * @env: The load balancing environment.
7843
 *
7844
 * Return:	- The busiest group if imbalance exists.
7845
 */
J
Joonsoo Kim 已提交
7846
static struct sched_group *find_busiest_group(struct lb_env *env)
7847
{
J
Joonsoo Kim 已提交
7848
	struct sg_lb_stats *local, *busiest;
7849 7850
	struct sd_lb_stats sds;

7851
	init_sd_lb_stats(&sds);
7852 7853 7854 7855 7856

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7857
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7858 7859
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7860

7861
	/* ASYM feature bypasses nice load balance check */
7862
	if (check_asym_packing(env, &sds))
7863 7864
		return sds.busiest;

7865
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7866
	if (!sds.busiest || busiest->sum_nr_running == 0)
7867 7868
		goto out_balanced;

7869 7870
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7871

P
Peter Zijlstra 已提交
7872 7873
	/*
	 * If the busiest group is imbalanced the below checks don't
7874
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7875 7876
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7877
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7878 7879
		goto force_balance;

7880
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7881 7882
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7883 7884
		goto force_balance;

7885
	/*
7886
	 * If the local group is busier than the selected busiest group
7887 7888
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7889
	if (local->avg_load >= busiest->avg_load)
7890 7891
		goto out_balanced;

7892 7893 7894 7895
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7896
	if (local->avg_load >= sds.avg_load)
7897 7898
		goto out_balanced;

7899
	if (env->idle == CPU_IDLE) {
7900
		/*
7901 7902 7903 7904 7905
		 * 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
7906
		 */
7907 7908
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7909
			goto out_balanced;
7910 7911 7912 7913 7914
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7915 7916
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7917
			goto out_balanced;
7918
	}
7919

7920
force_balance:
7921
	/* Looks like there is an imbalance. Compute it */
7922
	calculate_imbalance(env, &sds);
7923 7924 7925
	return sds.busiest;

out_balanced:
7926
	env->imbalance = 0;
7927 7928 7929 7930 7931 7932
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7933
static struct rq *find_busiest_queue(struct lb_env *env,
7934
				     struct sched_group *group)
7935 7936
{
	struct rq *busiest = NULL, *rq;
7937
	unsigned long busiest_load = 0, busiest_capacity = 1;
7938 7939
	int i;

7940
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7941
		unsigned long capacity, wl;
7942 7943 7944 7945
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7946

7947 7948 7949 7950 7951 7952 7953 7954 7955 7956 7957 7958 7959 7960 7961 7962 7963 7964 7965 7966 7967 7968
		/*
		 * 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;

7969
		capacity = capacity_of(i);
7970

7971
		wl = weighted_cpuload(i);
7972

7973 7974
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7975
		 * which is not scaled with the cpu capacity.
7976
		 */
7977 7978 7979

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7980 7981
			continue;

7982 7983
		/*
		 * For the load comparisons with the other cpu's, consider
7984 7985 7986
		 * 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.
7987
		 *
7988
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7989
		 * multiplication to rid ourselves of the division works out
7990 7991
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7992
		 */
7993
		if (wl * busiest_capacity > busiest_load * capacity) {
7994
			busiest_load = wl;
7995
			busiest_capacity = capacity;
7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008
			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

8009
static int need_active_balance(struct lb_env *env)
8010
{
8011 8012 8013
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8014 8015 8016

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8017 8018
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8019
		 */
T
Tim Chen 已提交
8020 8021
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8022
			return 1;
8023 8024
	}

8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037
	/*
	 * 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;
	}

8038 8039 8040
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8041 8042
static int active_load_balance_cpu_stop(void *data);

8043 8044 8045 8046 8047 8048 8049 8050 8051 8052 8053 8054 8055
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

	/*
	 * 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 */
8056
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8057
		if (!idle_cpu(cpu))
8058 8059 8060 8061 8062 8063 8064 8065 8066 8067 8068 8069 8070
			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.
	 */
8071
	return balance_cpu == env->dst_cpu;
8072 8073
}

8074 8075 8076 8077 8078 8079
/*
 * 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,
8080
			int *continue_balancing)
8081
{
8082
	int ld_moved, cur_ld_moved, active_balance = 0;
8083
	struct sched_domain *sd_parent = sd->parent;
8084 8085
	struct sched_group *group;
	struct rq *busiest;
8086
	struct rq_flags rf;
8087
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8088

8089 8090
	struct lb_env env = {
		.sd		= sd,
8091 8092
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8093
		.dst_grpmask    = sched_group_span(sd->groups),
8094
		.idle		= idle,
8095
		.loop_break	= sched_nr_migrate_break,
8096
		.cpus		= cpus,
8097
		.fbq_type	= all,
8098
		.tasks		= LIST_HEAD_INIT(env.tasks),
8099 8100
	};

8101 8102 8103 8104
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
8105
	if (idle == CPU_NEWLY_IDLE)
8106 8107
		env.dst_grpmask = NULL;

8108 8109
	cpumask_copy(cpus, cpu_active_mask);

8110
	schedstat_inc(sd->lb_count[idle]);
8111 8112

redo:
8113 8114
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8115
		goto out_balanced;
8116
	}
8117

8118
	group = find_busiest_group(&env);
8119
	if (!group) {
8120
		schedstat_inc(sd->lb_nobusyg[idle]);
8121 8122 8123
		goto out_balanced;
	}

8124
	busiest = find_busiest_queue(&env, group);
8125
	if (!busiest) {
8126
		schedstat_inc(sd->lb_nobusyq[idle]);
8127 8128 8129
		goto out_balanced;
	}

8130
	BUG_ON(busiest == env.dst_rq);
8131

8132
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8133

8134 8135 8136
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8137 8138 8139 8140 8141 8142 8143 8144
	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.
		 */
8145
		env.flags |= LBF_ALL_PINNED;
8146
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8147

8148
more_balance:
8149
		rq_lock_irqsave(busiest, &rf);
8150
		update_rq_clock(busiest);
8151 8152 8153 8154 8155

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8156
		cur_ld_moved = detach_tasks(&env);
8157 8158

		/*
8159 8160 8161 8162 8163
		 * 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.
8164
		 */
8165

8166
		rq_unlock(busiest, &rf);
8167 8168 8169 8170 8171 8172

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8173
		local_irq_restore(rf.flags);
8174

8175 8176 8177 8178 8179
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8180 8181 8182 8183 8184 8185 8186 8187 8188 8189 8190 8191 8192 8193 8194 8195 8196 8197 8198
		/*
		 * 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.
		 */
8199
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8200

8201 8202 8203
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8204
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8205
			env.dst_cpu	 = env.new_dst_cpu;
8206
			env.flags	&= ~LBF_DST_PINNED;
8207 8208
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8209

8210 8211 8212 8213 8214 8215
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8216

8217 8218 8219 8220
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8221
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8222

8223
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8224 8225 8226
				*group_imbalance = 1;
		}

8227
		/* All tasks on this runqueue were pinned by CPU affinity */
8228
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8229
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8230 8231 8232
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8233
				goto redo;
8234
			}
8235
			goto out_all_pinned;
8236 8237 8238 8239
		}
	}

	if (!ld_moved) {
8240
		schedstat_inc(sd->lb_failed[idle]);
8241 8242 8243 8244 8245 8246 8247 8248
		/*
		 * 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++;
8249

8250
		if (need_active_balance(&env)) {
8251 8252
			unsigned long flags;

8253 8254
			raw_spin_lock_irqsave(&busiest->lock, flags);

8255 8256 8257
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
8258
			 */
8259
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8260 8261
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8262
				env.flags |= LBF_ALL_PINNED;
8263 8264 8265
				goto out_one_pinned;
			}

8266 8267 8268 8269 8270
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8271 8272 8273 8274 8275 8276
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8277

8278
			if (active_balance) {
8279 8280 8281
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8282
			}
8283

8284
			/* We've kicked active balancing, force task migration. */
8285 8286 8287 8288 8289 8290 8291 8292 8293 8294 8295 8296 8297
			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
8298
		 * detach_tasks).
8299 8300 8301 8302 8303 8304 8305 8306
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8307 8308 8309 8310 8311 8312 8313 8314 8315 8316 8317 8318 8319 8320 8321 8322 8323
	/*
	 * 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.
	 */
8324
	schedstat_inc(sd->lb_balanced[idle]);
8325 8326 8327 8328 8329

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8330
	if (((env.flags & LBF_ALL_PINNED) &&
8331
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8332 8333 8334
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8335
	ld_moved = 0;
8336 8337 8338 8339
out:
	return ld_moved;
}

8340 8341 8342 8343 8344 8345 8346 8347 8348 8349 8350 8351 8352 8353 8354 8355
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
8356
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8357 8358 8359
{
	unsigned long interval, next;

8360 8361
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8362 8363 8364 8365 8366 8367
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8368 8369 8370 8371
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
8372
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
8373
{
8374 8375
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
8376 8377
	struct sched_domain *sd;
	int pulled_task = 0;
8378
	u64 curr_cost = 0;
8379

8380 8381 8382 8383 8384 8385
	/*
	 * 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);

8386 8387 8388 8389 8390 8391 8392 8393
	/*
	 * 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);

8394 8395
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
8396 8397 8398
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
8399
			update_next_balance(sd, &next_balance);
8400 8401
		rcu_read_unlock();

8402
		goto out;
8403
	}
8404

8405 8406
	raw_spin_unlock(&this_rq->lock);

8407
	update_blocked_averages(this_cpu);
8408
	rcu_read_lock();
8409
	for_each_domain(this_cpu, sd) {
8410
		int continue_balancing = 1;
8411
		u64 t0, domain_cost;
8412 8413 8414 8415

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8416
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8417
			update_next_balance(sd, &next_balance);
8418
			break;
8419
		}
8420

8421
		if (sd->flags & SD_BALANCE_NEWIDLE) {
8422 8423
			t0 = sched_clock_cpu(this_cpu);

8424
			pulled_task = load_balance(this_cpu, this_rq,
8425 8426
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
8427 8428 8429 8430 8431 8432

			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;
8433
		}
8434

8435
		update_next_balance(sd, &next_balance);
8436 8437 8438 8439 8440 8441

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
8442 8443
			break;
	}
8444
	rcu_read_unlock();
8445 8446 8447

	raw_spin_lock(&this_rq->lock);

8448 8449 8450
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

8451
	/*
8452 8453 8454
	 * 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.
8455
	 */
8456
	if (this_rq->cfs.h_nr_running && !pulled_task)
8457
		pulled_task = 1;
8458

8459 8460 8461
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
8462
		this_rq->next_balance = next_balance;
8463

8464
	/* Is there a task of a high priority class? */
8465
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8466 8467
		pulled_task = -1;

8468
	if (pulled_task)
8469 8470
		this_rq->idle_stamp = 0;

8471 8472
	rq_repin_lock(this_rq, rf);

8473
	return pulled_task;
8474 8475 8476
}

/*
8477 8478 8479 8480
 * 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.
8481
 */
8482
static int active_load_balance_cpu_stop(void *data)
8483
{
8484 8485
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8486
	int target_cpu = busiest_rq->push_cpu;
8487
	struct rq *target_rq = cpu_rq(target_cpu);
8488
	struct sched_domain *sd;
8489
	struct task_struct *p = NULL;
8490
	struct rq_flags rf;
8491

8492
	rq_lock_irq(busiest_rq, &rf);
8493 8494 8495 8496 8497

	/* 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;
8498 8499 8500

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8501
		goto out_unlock;
8502 8503 8504 8505 8506 8507 8508 8509 8510

	/*
	 * 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. */
8511
	rcu_read_lock();
8512 8513 8514 8515 8516 8517 8518
	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)) {
8519 8520
		struct lb_env env = {
			.sd		= sd,
8521 8522 8523 8524
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8525 8526 8527
			.idle		= CPU_IDLE,
		};

8528
		schedstat_inc(sd->alb_count);
8529
		update_rq_clock(busiest_rq);
8530

8531
		p = detach_one_task(&env);
8532
		if (p) {
8533
			schedstat_inc(sd->alb_pushed);
8534 8535 8536
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8537
			schedstat_inc(sd->alb_failed);
8538
		}
8539
	}
8540
	rcu_read_unlock();
8541 8542
out_unlock:
	busiest_rq->active_balance = 0;
8543
	rq_unlock(busiest_rq, &rf);
8544 8545 8546 8547 8548 8549

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8550
	return 0;
8551 8552
}

8553 8554 8555 8556 8557
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8558
#ifdef CONFIG_NO_HZ_COMMON
8559 8560 8561 8562 8563 8564
/*
 * 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.
 */
8565
static struct {
8566
	cpumask_var_t idle_cpus_mask;
8567
	atomic_t nr_cpus;
8568 8569
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
8570

8571
static inline int find_new_ilb(void)
8572
{
8573
	int ilb = cpumask_first(nohz.idle_cpus_mask);
8574

8575 8576 8577 8578
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
8579 8580
}

8581 8582 8583 8584 8585
/*
 * 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).
 */
8586
static void nohz_balancer_kick(void)
8587 8588 8589 8590 8591
{
	int ilb_cpu;

	nohz.next_balance++;

8592
	ilb_cpu = find_new_ilb();
8593

8594 8595
	if (ilb_cpu >= nr_cpu_ids)
		return;
8596

8597
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8598 8599 8600 8601 8602 8603 8604 8605
		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);
8606 8607 8608
	return;
}

8609
void nohz_balance_exit_idle(unsigned int cpu)
8610 8611
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8612 8613 8614 8615 8616 8617 8618
		/*
		 * 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);
		}
8619 8620 8621 8622
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

8623 8624 8625
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
8626
	int cpu = smp_processor_id();
8627 8628

	rcu_read_lock();
8629
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8630 8631 8632 8633 8634

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

8635
	atomic_inc(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8636
unlock:
8637 8638 8639 8640 8641 8642
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
8643
	int cpu = smp_processor_id();
8644 8645

	rcu_read_lock();
8646
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8647 8648 8649 8650 8651

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

8652
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8653
unlock:
8654 8655 8656
	rcu_read_unlock();
}

8657
/*
8658
 * This routine will record that the cpu is going idle with tick stopped.
8659
 * This info will be used in performing idle load balancing in the future.
8660
 */
8661
void nohz_balance_enter_idle(int cpu)
8662
{
8663 8664 8665 8666 8667 8668
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

8669 8670
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
8671

8672 8673 8674 8675 8676 8677
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

8678 8679 8680
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8681 8682 8683 8684 8685
}
#endif

static DEFINE_SPINLOCK(balancing);

8686 8687 8688 8689
/*
 * 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.
 */
8690
void update_max_interval(void)
8691 8692 8693 8694
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

8695 8696 8697 8698
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
8699
 * Balancing parameters are set up in init_sched_domains.
8700
 */
8701
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8702
{
8703
	int continue_balancing = 1;
8704
	int cpu = rq->cpu;
8705
	unsigned long interval;
8706
	struct sched_domain *sd;
8707 8708 8709
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8710 8711
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
8712

8713
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
8714

8715
	rcu_read_lock();
8716
	for_each_domain(cpu, sd) {
8717 8718 8719 8720 8721 8722 8723 8724 8725 8726 8727 8728
		/*
		 * 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;

8729 8730 8731
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8732 8733 8734 8735 8736 8737 8738 8739 8740 8741 8742
		/*
		 * 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;
		}

8743
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8744 8745 8746 8747 8748 8749 8750 8751

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8752
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8753
				/*
8754
				 * The LBF_DST_PINNED logic could have changed
8755 8756
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
8757
				 */
8758
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8759 8760
			}
			sd->last_balance = jiffies;
8761
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8762 8763 8764 8765 8766 8767 8768 8769
		}
		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;
		}
8770 8771
	}
	if (need_decay) {
8772
		/*
8773 8774
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
8775
		 */
8776 8777
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
8778
	}
8779
	rcu_read_unlock();
8780 8781 8782 8783 8784 8785

	/*
	 * 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.
	 */
8786
	if (likely(update_next_balance)) {
8787
		rq->next_balance = next_balance;
8788 8789 8790 8791 8792 8793 8794 8795 8796 8797 8798 8799 8800 8801

#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
	}
8802 8803
}

8804
#ifdef CONFIG_NO_HZ_COMMON
8805
/*
8806
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8807 8808
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
8809
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8810
{
8811
	int this_cpu = this_rq->cpu;
8812 8813
	struct rq *rq;
	int balance_cpu;
8814 8815 8816
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8817

8818 8819 8820
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8821 8822

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8823
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8824 8825 8826 8827 8828 8829 8830
			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.
		 */
8831
		if (need_resched())
8832 8833
			break;

V
Vincent Guittot 已提交
8834 8835
		rq = cpu_rq(balance_cpu);

8836 8837 8838 8839 8840
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
8841 8842 8843
			struct rq_flags rf;

			rq_lock_irq(rq, &rf);
8844
			update_rq_clock(rq);
8845
			cpu_load_update_idle(rq);
8846 8847
			rq_unlock_irq(rq, &rf);

8848 8849
			rebalance_domains(rq, CPU_IDLE);
		}
8850

8851 8852 8853 8854
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8855
	}
8856 8857 8858 8859 8860 8861 8862 8863

	/*
	 * 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;
8864 8865
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8866 8867 8868
}

/*
8869
 * Current heuristic for kicking the idle load balancer in the presence
8870
 * of an idle cpu in the system.
8871
 *   - This rq has more than one task.
8872 8873 8874 8875
 *   - 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.
8876 8877
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8878
 */
8879
static inline bool nohz_kick_needed(struct rq *rq)
8880 8881
{
	unsigned long now = jiffies;
8882
	struct sched_domain_shared *sds;
8883
	struct sched_domain *sd;
T
Tim Chen 已提交
8884
	int nr_busy, i, cpu = rq->cpu;
8885
	bool kick = false;
8886

8887
	if (unlikely(rq->idle_balance))
8888
		return false;
8889

8890 8891 8892 8893
       /*
	* 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.
	*/
8894
	set_cpu_sd_state_busy();
8895
	nohz_balance_exit_idle(cpu);
8896 8897 8898 8899 8900 8901

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8902
		return false;
8903 8904

	if (time_before(now, nohz.next_balance))
8905
		return false;
8906

8907
	if (rq->nr_running >= 2)
8908
		return true;
8909

8910
	rcu_read_lock();
8911 8912 8913 8914 8915 8916 8917
	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);
8918 8919 8920 8921 8922
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8923
	}
8924

8925 8926 8927 8928 8929 8930 8931 8932
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8933

8934
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
T
Tim Chen 已提交
8935 8936 8937 8938 8939
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;
8940

T
Tim Chen 已提交
8941 8942 8943 8944 8945 8946
			if (sched_asym_prefer(i, cpu)) {
				kick = true;
				goto unlock;
			}
		}
	}
8947
unlock:
8948
	rcu_read_unlock();
8949
	return kick;
8950 8951
}
#else
8952
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8953 8954 8955 8956 8957 8958
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8959
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
8960
{
8961
	struct rq *this_rq = this_rq();
8962
	enum cpu_idle_type idle = this_rq->idle_balance ?
8963 8964 8965
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8966
	 * If this cpu has a pending nohz_balance_kick, then do the
8967
	 * balancing on behalf of the other idle cpus whose ticks are
8968 8969 8970 8971
	 * 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.
8972
	 */
8973
	nohz_idle_balance(this_rq, idle);
8974
	rebalance_domains(this_rq, idle);
8975 8976 8977 8978 8979
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8980
void trigger_load_balance(struct rq *rq)
8981 8982
{
	/* Don't need to rebalance while attached to NULL domain */
8983 8984 8985 8986
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8987
		raise_softirq(SCHED_SOFTIRQ);
8988
#ifdef CONFIG_NO_HZ_COMMON
8989
	if (nohz_kick_needed(rq))
8990
		nohz_balancer_kick();
8991
#endif
8992 8993
}

8994 8995 8996
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8997 8998

	update_runtime_enabled(rq);
8999 9000 9001 9002 9003
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9004 9005 9006

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9007 9008
}

9009
#endif /* CONFIG_SMP */
9010

9011 9012 9013
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
9014
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9015 9016 9017 9018 9019 9020
{
	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
9021
		entity_tick(cfs_rq, se, queued);
9022
	}
9023

9024
	if (static_branch_unlikely(&sched_numa_balancing))
9025
		task_tick_numa(rq, curr);
9026 9027 9028
}

/*
P
Peter Zijlstra 已提交
9029 9030 9031
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9032
 */
P
Peter Zijlstra 已提交
9033
static void task_fork_fair(struct task_struct *p)
9034
{
9035 9036
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9037
	struct rq *rq = this_rq();
9038
	struct rq_flags rf;
9039

9040
	rq_lock(rq, &rf);
9041 9042
	update_rq_clock(rq);

9043 9044
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9045 9046
	if (curr) {
		update_curr(cfs_rq);
9047
		se->vruntime = curr->vruntime;
9048
	}
9049
	place_entity(cfs_rq, se, 1);
9050

P
Peter Zijlstra 已提交
9051
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9052
		/*
9053 9054 9055
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9056
		swap(curr->vruntime, se->vruntime);
9057
		resched_curr(rq);
9058
	}
9059

9060
	se->vruntime -= cfs_rq->min_vruntime;
9061
	rq_unlock(rq, &rf);
9062 9063
}

9064 9065 9066 9067
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9068 9069
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9070
{
9071
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9072 9073
		return;

9074 9075 9076 9077 9078
	/*
	 * 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
9079
	if (rq->curr == p) {
9080
		if (p->prio > oldprio)
9081
			resched_curr(rq);
9082
	} else
9083
		check_preempt_curr(rq, p, 0);
9084 9085
}

9086
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9087 9088 9089 9090
{
	struct sched_entity *se = &p->se;

	/*
9091 9092 9093 9094 9095 9096 9097 9098 9099 9100
	 * 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
9101
	 *
9102 9103 9104 9105
	 * - 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
9106
	 */
9107 9108 9109 9110 9111 9112
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9113 9114 9115 9116 9117 9118 9119 9120 9121 9122 9123 9124 9125 9126 9127 9128 9129 9130 9131 9132 9133 9134 9135 9136 9137
#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;

		update_load_avg(se, UPDATE_TG);
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9138
static void detach_entity_cfs_rq(struct sched_entity *se)
9139 9140 9141
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9142
	/* Catch up with the cfs_rq and remove our load when we leave */
9143
	update_load_avg(se, 0);
9144
	detach_entity_load_avg(cfs_rq, se);
9145
	update_tg_load_avg(cfs_rq, false);
9146
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9147 9148
}

9149
static void attach_entity_cfs_rq(struct sched_entity *se)
9150
{
9151
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9152 9153

#ifdef CONFIG_FAIR_GROUP_SCHED
9154 9155 9156 9157 9158 9159
	/*
	 * 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
9160

9161
	/* Synchronize entity with its cfs_rq */
9162
	update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9163
	attach_entity_load_avg(cfs_rq, se);
9164
	update_tg_load_avg(cfs_rq, false);
9165
	propagate_entity_cfs_rq(se);
9166 9167 9168 9169 9170 9171 9172 9173 9174 9175 9176 9177 9178 9179 9180 9181 9182 9183 9184 9185 9186 9187 9188 9189 9190
}

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);
9191 9192 9193 9194

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9195

9196 9197 9198 9199 9200 9201 9202 9203
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);
9204

9205
	if (task_on_rq_queued(p)) {
9206
		/*
9207 9208 9209
		 * 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.
9210
		 */
9211 9212 9213 9214
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9215
	}
9216 9217
}

9218 9219 9220 9221 9222 9223 9224 9225 9226
/* 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;

9227 9228 9229 9230 9231 9232 9233
	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);
	}
9234 9235
}

9236 9237 9238 9239 9240 9241 9242
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
	cfs_rq->tasks_timeline = RB_ROOT;
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9243
#ifdef CONFIG_SMP
9244 9245 9246
#ifdef CONFIG_FAIR_GROUP_SCHED
	cfs_rq->propagate_avg = 0;
#endif
9247 9248
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
9249
#endif
9250 9251
}

P
Peter Zijlstra 已提交
9252
#ifdef CONFIG_FAIR_GROUP_SCHED
9253 9254 9255 9256 9257 9258 9259 9260
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;
}

9261
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9262
{
9263
	detach_task_cfs_rq(p);
9264
	set_task_rq(p, task_cpu(p));
9265 9266 9267 9268 9269

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9270
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9271
}
9272

9273 9274 9275 9276 9277 9278 9279 9280 9281 9282 9283 9284 9285
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;
	}
}

9286 9287 9288 9289 9290 9291 9292 9293 9294
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]);
9295
		if (tg->se)
9296 9297 9298 9299 9300 9301 9302 9303 9304 9305
			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;
9306
	struct cfs_rq *cfs_rq;
9307 9308 9309 9310 9311 9312 9313 9314 9315 9316 9317 9318 9319 9320 9321 9322 9323 9324 9325 9326 9327 9328 9329 9330 9331 9332
	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]);
9333
		init_entity_runnable_average(se);
9334 9335 9336 9337 9338 9339 9340 9341 9342 9343
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9344 9345 9346 9347 9348 9349 9350 9351 9352 9353 9354
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);
9355
		update_rq_clock(rq);
9356
		attach_entity_cfs_rq(se);
9357
		sync_throttle(tg, i);
9358 9359 9360 9361
		raw_spin_unlock_irq(&rq->lock);
	}
}

9362
void unregister_fair_sched_group(struct task_group *tg)
9363 9364
{
	unsigned long flags;
9365 9366
	struct rq *rq;
	int cpu;
9367

9368 9369 9370
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
9371

9372 9373 9374 9375 9376 9377 9378 9379 9380 9381 9382 9383 9384
		/*
		 * 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);
	}
9385 9386 9387 9388 9389 9390 9391 9392 9393 9394 9395 9396 9397 9398 9399 9400 9401 9402 9403
}

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
9404
	if (!parent) {
9405
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
9406 9407
		se->depth = 0;
	} else {
9408
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
9409 9410
		se->depth = parent->depth + 1;
	}
9411 9412

	se->my_q = cfs_rq;
9413 9414
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
9415 9416 9417 9418 9419 9420 9421 9422 9423 9424 9425 9426 9427 9428 9429 9430 9431 9432 9433 9434 9435 9436 9437 9438
	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);
9439 9440
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
9441 9442

		/* Propagate contribution to hierarchy */
9443
		rq_lock_irqsave(rq, &rf);
9444
		update_rq_clock(rq);
9445 9446 9447 9448
		for_each_sched_entity(se) {
			update_load_avg(se, UPDATE_TG);
			update_cfs_shares(se);
		}
9449
		rq_unlock_irqrestore(rq, &rf);
9450 9451 9452 9453 9454 9455 9456 9457 9458 9459 9460 9461 9462 9463 9464
	}

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;
}

9465 9466
void online_fair_sched_group(struct task_group *tg) { }

9467
void unregister_fair_sched_group(struct task_group *tg) { }
9468 9469 9470

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
9471

9472
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9473 9474 9475 9476 9477 9478 9479 9480 9481
{
	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)
9482
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9483 9484 9485 9486

	return rr_interval;
}

9487 9488 9489
/*
 * All the scheduling class methods:
 */
9490
const struct sched_class fair_sched_class = {
9491
	.next			= &idle_sched_class,
9492 9493 9494
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
9495
	.yield_to_task		= yield_to_task_fair,
9496

I
Ingo Molnar 已提交
9497
	.check_preempt_curr	= check_preempt_wakeup,
9498 9499 9500 9501

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

9502
#ifdef CONFIG_SMP
L
Li Zefan 已提交
9503
	.select_task_rq		= select_task_rq_fair,
9504
	.migrate_task_rq	= migrate_task_rq_fair,
9505

9506 9507
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
9508

9509
	.task_dead		= task_dead_fair,
9510
	.set_cpus_allowed	= set_cpus_allowed_common,
9511
#endif
9512

9513
	.set_curr_task          = set_curr_task_fair,
9514
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
9515
	.task_fork		= task_fork_fair,
9516 9517

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
9518
	.switched_from		= switched_from_fair,
9519
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
9520

9521 9522
	.get_rr_interval	= get_rr_interval_fair,

9523 9524
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
9525
#ifdef CONFIG_FAIR_GROUP_SCHED
9526
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
9527
#endif
9528 9529 9530
};

#ifdef CONFIG_SCHED_DEBUG
9531
void print_cfs_stats(struct seq_file *m, int cpu)
9532
{
9533
	struct cfs_rq *cfs_rq, *pos;
9534

9535
	rcu_read_lock();
9536
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
9537
		print_cfs_rq(m, cpu, cfs_rq);
9538
	rcu_read_unlock();
9539
}
9540 9541 9542 9543 9544 9545 9546 9547 9548 9549 9550 9551 9552 9553 9554 9555 9556 9557 9558 9559 9560

#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 */
9561 9562 9563 9564 9565 9566

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

9567
#ifdef CONFIG_NO_HZ_COMMON
9568
	nohz.next_balance = jiffies;
9569 9570 9571 9572 9573
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}