fair.c 253.8 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */

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#include <linux/sched/mm.h>
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#include <linux/sched/topology.h>

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

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

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

	w = scale_load_down(lw->weight);

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

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


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

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

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/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
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static inline struct task_struct *task_of(struct sched_entity *se)
{
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	SCHED_WARN_ON(!entity_is_task(se));
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	return container_of(se, struct task_struct, se);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

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/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
673
 * s = p*P[w/rw]
674
 */
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Peter Zijlstra 已提交
675
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
676
{
M
Mike Galbraith 已提交
677
	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
678

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

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

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

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

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

707
#ifdef CONFIG_SMP
708 709 710

#include "sched-pelt.h"

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

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

719 720 721 722 723 724 725
	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;
726 727 728 729 730 731 732 733
	/*
	 * 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);
734
	sa->load_sum = LOAD_AVG_MAX;
735 736 737 738 739
	/*
	 * At this point, util_avg won't be used in select_task_rq_fair anyway
	 */
	sa->util_avg = 0;
	sa->util_sum = 0;
740
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
741
}
742

743
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
744
static void attach_entity_cfs_rq(struct sched_entity *se);
745

746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774
/*
 * 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;
775
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
776 777 778 779 780 781 782 783 784 785 786 787 788

	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;
	}
789 790 791 792 793 794 795

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
796
			update_cfs_rq_load_avg(now, cfs_rq);
797 798 799 800 801 802
			attach_entity_load_avg(cfs_rq, se);
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
803
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
804 805 806 807
			return;
		}
	}

808
	attach_entity_cfs_rq(se);
809 810
}

811
#else /* !CONFIG_SMP */
812
void init_entity_runnable_average(struct sched_entity *se)
813 814
{
}
815 816 817
void post_init_entity_util_avg(struct sched_entity *se)
{
}
818 819 820
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
821
#endif /* CONFIG_SMP */
822

823
/*
824
 * Update the current task's runtime statistics.
825
 */
826
static void update_curr(struct cfs_rq *cfs_rq)
827
{
828
	struct sched_entity *curr = cfs_rq->curr;
829
	u64 now = rq_clock_task(rq_of(cfs_rq));
830
	u64 delta_exec;
831 832 833 834

	if (unlikely(!curr))
		return;

835 836
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
837
		return;
838

I
Ingo Molnar 已提交
839
	curr->exec_start = now;
840

841 842 843 844
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
845
	schedstat_add(cfs_rq->exec_clock, delta_exec);
846 847 848 849

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

850 851 852
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

853
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
854
		cpuacct_charge(curtask, delta_exec);
855
		account_group_exec_runtime(curtask, delta_exec);
856
	}
857 858

	account_cfs_rq_runtime(cfs_rq, delta_exec);
859 860
}

861 862 863 864 865
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

866
static inline void
867
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
868
{
869 870 871 872 873 874 875
	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);
876 877

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
878 879
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
880

881
	schedstat_set(se->statistics.wait_start, wait_start);
882 883
}

884
static inline void
885 886 887
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
888 889
	u64 delta;

890 891 892 893
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
894 895 896 897 898 899 900 901 902

	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.
			 */
903
			schedstat_set(se->statistics.wait_start, delta);
904 905 906 907 908
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

909 910 911 912 913
	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);
914 915
}

916
static inline void
917 918 919
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
920 921 922 923 924 925 926
	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);
927 928 929 930

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

931 932
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
933 934 935 936

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

937 938
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
			schedstat_set(se->statistics.sleep_max, delta);
939

940 941
		schedstat_set(se->statistics.sleep_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
942 943 944 945 946 947

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
948 949
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
950 951 952 953

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

954 955
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
			schedstat_set(se->statistics.block_max, delta);
956

957 958
		schedstat_set(se->statistics.block_start, 0);
		schedstat_add(se->statistics.sum_sleep_runtime, delta);
959 960 961

		if (tsk) {
			if (tsk->in_iowait) {
962 963
				schedstat_add(se->statistics.iowait_sum, delta);
				schedstat_inc(se->statistics.iowait_count);
964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981
				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);
		}
	}
982 983
}

984 985 986
/*
 * Task is being enqueued - update stats:
 */
987
static inline void
988
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
989
{
990 991 992
	if (!schedstat_enabled())
		return;

993 994 995 996
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
997
	if (se != cfs_rq->curr)
998
		update_stats_wait_start(cfs_rq, se);
999 1000 1001

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
1002 1003 1004
}

static inline void
1005
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1006
{
1007 1008 1009 1010

	if (!schedstat_enabled())
		return;

1011 1012 1013 1014
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
1015
	if (se != cfs_rq->curr)
1016
		update_stats_wait_end(cfs_rq, se);
1017

1018 1019
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
1020

1021 1022 1023 1024 1025 1026
		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)));
1027 1028 1029
	}
}

1030 1031 1032 1033
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1034
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1035 1036 1037 1038
{
	/*
	 * We are starting a new run period:
	 */
1039
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1040 1041 1042 1043 1044 1045
}

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

1046 1047
#ifdef CONFIG_NUMA_BALANCING
/*
1048 1049 1050
 * 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.
1051
 */
1052 1053
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1054 1055 1056

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1057

1058 1059 1060
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083
struct numa_group {
	atomic_t refcount;

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

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

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

1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107
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)
{
1108
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1109 1110 1111
	unsigned int scan, floor;
	unsigned int windows = 1;

1112 1113
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
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);
}

1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;

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

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

	return max(smin, period);
}

1139 1140
static unsigned int task_scan_max(struct task_struct *p)
{
1141 1142
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1143 1144 1145

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160

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

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

		smax = max(smax, period);
	}

1161 1162 1163
	return max(smin, smax);
}

1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175
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));
}

1176 1177 1178 1179 1180 1181 1182 1183 1184
/* 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)

1185 1186 1187 1188 1189
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1190 1191 1192 1193 1194 1195 1196
/*
 * 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)
1197
{
1198
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1199 1200 1201 1202
}

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

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

1210 1211 1212 1213 1214
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1215 1216
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1217 1218
}

1219 1220
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1221 1222
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
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
static inline unsigned long group_faults_priv(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

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

	return faults;
}

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

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

	return faults;
}

1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260
/*
 * 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;
}

1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325
/* 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;
}

1326 1327 1328 1329 1330 1331
/*
 * 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.
 */
1332 1333
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1334
{
1335
	unsigned long faults, total_faults;
1336

1337
	if (!p->numa_faults)
1338 1339 1340 1341 1342 1343 1344
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1345
	faults = task_faults(p, nid);
1346 1347
	faults += score_nearby_nodes(p, nid, dist, true);

1348
	return 1000 * faults / total_faults;
1349 1350
}

1351 1352
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1353
{
1354 1355 1356 1357 1358 1359 1360 1361
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1362 1363
		return 0;

1364
	faults = group_faults(p, nid);
1365 1366
	faults += score_nearby_nodes(p, nid, dist, false);

1367
	return 1000 * faults / total_faults;
1368 1369
}

1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409
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;

	/*
1410 1411
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1412
	 */
1413 1414
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1415 1416 1417
		return true;

	/*
1418 1419 1420 1421 1422 1423
	 * 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)
1424
	 */
1425 1426
	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;
1427 1428
}

1429
static unsigned long weighted_cpuload(struct rq *rq);
1430 1431
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1432
static unsigned long capacity_of(int cpu);
1433

1434
/* Cached statistics for all CPUs within a node */
1435
struct numa_stats {
1436
	unsigned long nr_running;
1437
	unsigned long load;
1438 1439

	/* Total compute capacity of CPUs on a node */
1440
	unsigned long compute_capacity;
1441 1442

	/* Approximate capacity in terms of runnable tasks on a node */
1443
	unsigned long task_capacity;
1444
	int has_free_capacity;
1445
};
1446

1447 1448 1449 1450 1451
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1452 1453
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1454 1455 1456 1457 1458 1459

	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;
1460
		ns->load += weighted_cpuload(rq);
1461
		ns->compute_capacity += capacity_of(cpu);
1462 1463

		cpus++;
1464 1465
	}

1466 1467 1468 1469 1470
	/*
	 * 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.
	 *
1471 1472
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1473 1474 1475 1476
	 */
	if (!cpus)
		return;

1477 1478 1479 1480 1481 1482
	/* 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));
1483
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1484 1485
}

1486 1487
struct task_numa_env {
	struct task_struct *p;
1488

1489 1490
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1491

1492
	struct numa_stats src_stats, dst_stats;
1493

1494
	int imbalance_pct;
1495
	int dist;
1496 1497 1498

	struct task_struct *best_task;
	long best_imp;
1499 1500 1501
	int best_cpu;
};

1502 1503 1504 1505 1506
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);
1507 1508
	if (p)
		get_task_struct(p);
1509 1510 1511 1512 1513 1514

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

1515
static bool load_too_imbalanced(long src_load, long dst_load,
1516 1517
				struct task_numa_env *env)
{
1518 1519
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530
	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;
1531 1532

	/* We care about the slope of the imbalance, not the direction. */
1533 1534
	if (dst_load < src_load)
		swap(dst_load, src_load);
1535 1536

	/* Is the difference below the threshold? */
1537 1538
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1539 1540 1541 1542 1543
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1544
	 * Compare it with the old imbalance.
1545
	 */
1546
	orig_src_load = env->src_stats.load;
1547
	orig_dst_load = env->dst_stats.load;
1548

1549 1550
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1551

1552 1553 1554 1555 1556
	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);
1557 1558
}

1559 1560 1561 1562 1563 1564
/*
 * 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
 */
1565 1566
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1567 1568 1569 1570
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1571
	long src_load, dst_load;
1572
	long load;
1573
	long imp = env->p->numa_group ? groupimp : taskimp;
1574
	long moveimp = imp;
1575
	int dist = env->dist;
1576 1577

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

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

1589 1590 1591 1592 1593 1594 1595 1596 1597
	/*
	 * "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 */
1598
		if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1599 1600
			goto unlock;

1601 1602
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1603
		 * in any group then look only at task weights.
1604
		 */
1605
		if (cur->numa_group == env->p->numa_group) {
1606 1607
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1608 1609 1610 1611 1612 1613
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1614
		} else {
1615 1616 1617 1618 1619 1620
			/*
			 * 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)
1621 1622
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1623
			else
1624 1625
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1626
		}
1627 1628
	}

1629
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1630 1631 1632 1633
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1634
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1635
		    !env->dst_stats.has_free_capacity)
1636 1637 1638 1639 1640 1641
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1642 1643
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1644 1645 1646 1647 1648 1649
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1650 1651 1652
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1653

1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670
	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;

1671
	if (cur) {
1672 1673 1674
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1675 1676
	}

1677
	if (load_too_imbalanced(src_load, dst_load, env))
1678 1679
		goto unlock;

1680 1681 1682 1683
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1684 1685 1686 1687 1688 1689
	if (!cur) {
		/*
		 * select_idle_siblings() uses an per-cpu cpumask that
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1690 1691
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1692 1693
		local_irq_enable();
	}
1694

1695 1696 1697 1698 1699 1700
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1701 1702
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1703 1704 1705 1706 1707
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1708
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1709 1710 1711
			continue;

		env->dst_cpu = cpu;
1712
		task_numa_compare(env, taskimp, groupimp);
1713 1714 1715
	}
}

1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732
/* 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
	 */
1733 1734 1735
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1736 1737 1738 1739 1740
		return true;

	return false;
}

1741 1742 1743 1744
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1745

1746
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1747
		.src_nid = task_node(p),
1748 1749 1750 1751 1752

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1753
		.best_cpu = -1,
1754 1755
	};
	struct sched_domain *sd;
1756
	unsigned long taskweight, groupweight;
1757
	int nid, ret, dist;
1758
	long taskimp, groupimp;
1759

1760
	/*
1761 1762 1763 1764 1765 1766
	 * 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.
1767 1768
	 */
	rcu_read_lock();
1769
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1770 1771
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1772 1773
	rcu_read_unlock();

1774 1775 1776 1777 1778 1779 1780
	/*
	 * 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)) {
1781
		p->numa_preferred_nid = task_node(p);
1782 1783 1784
		return -EINVAL;
	}

1785
	env.dst_nid = p->numa_preferred_nid;
1786 1787 1788 1789 1790 1791
	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;
1792
	update_numa_stats(&env.dst_stats, env.dst_nid);
1793

1794
	/* Try to find a spot on the preferred nid. */
1795 1796
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1797

1798 1799 1800 1801 1802 1803 1804
	/*
	 * 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.
	 */
1805
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1806 1807 1808
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1809

1810
			dist = node_distance(env.src_nid, env.dst_nid);
1811 1812 1813 1814 1815
			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);
			}
1816

1817
			/* Only consider nodes where both task and groups benefit */
1818 1819
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1820
			if (taskimp < 0 && groupimp < 0)
1821 1822
				continue;

1823
			env.dist = dist;
1824 1825
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1826 1827
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1828 1829 1830
		}
	}

1831 1832 1833 1834 1835 1836 1837 1838
	/*
	 * 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.
	 */
1839
	if (p->numa_group) {
1840 1841
		struct numa_group *ng = p->numa_group;

1842 1843 1844 1845 1846
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1847
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1848 1849 1850 1851 1852 1853
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1854

1855 1856 1857 1858
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
1859
	p->numa_scan_period = task_scan_start(p);
1860

1861
	if (env.best_task == NULL) {
1862 1863 1864
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1865 1866 1867 1868
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1869 1870
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1871 1872
	put_task_struct(env.best_task);
	return ret;
1873 1874
}

1875 1876 1877
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1878 1879
	unsigned long interval = HZ;

1880
	/* This task has no NUMA fault statistics yet */
1881
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1882 1883
		return;

1884
	/* Periodically retry migrating the task to the preferred node */
1885 1886
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1887 1888

	/* Success if task is already running on preferred CPU */
1889
	if (task_node(p) == p->numa_preferred_nid)
1890 1891 1892
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1893
	task_numa_migrate(p);
1894 1895
}

1896
/*
1897
 * Find out how many nodes on the workload is actively running on. Do this by
1898 1899 1900 1901
 * 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.
 */
1902
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1903 1904
{
	unsigned long faults, max_faults = 0;
1905
	int nid, active_nodes = 0;
1906 1907 1908 1909 1910 1911 1912 1913 1914

	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);
1915 1916
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1917
	}
1918 1919 1920

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1921 1922
}

1923 1924 1925
/*
 * 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
1926 1927 1928
 * 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.
1929 1930
 */
#define NUMA_PERIOD_SLOTS 10
1931
#define NUMA_PERIOD_THRESHOLD 7
1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942

/*
 * 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;
1943
	int lr_ratio, ps_ratio;
1944 1945 1946 1947 1948 1949 1950 1951
	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
1952 1953 1954
	 * 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
1955
	 */
1956
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
		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);
1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991
	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);

	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are local. There is no need to
		 * do fast NUMA scanning, since memory is already local.
		 */
		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are shared with other tasks.
		 * There is no point in continuing fast NUMA scanning,
		 * since other tasks may just move the memory elsewhere.
		 */
		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
1992 1993 1994 1995 1996
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1997 1998 1999
		 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
		 * yet they are not on the local NUMA node. Speed up
		 * NUMA scanning to get the memory moved over.
2000
		 */
2001 2002
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2003 2004 2005 2006 2007 2008 2009
	}

	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));
}

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027
/*
 * 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 {
2028
		delta = p->se.avg.load_sum;
2029
		*period = LOAD_AVG_MAX;
2030 2031 2032 2033 2034 2035 2036 2037
	}

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

	return delta;
}

2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084
/*
 * 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;
2085
		nodemask_t max_group = NODE_MASK_NONE;
2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118
		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. */
2119 2120
		if (!max_faults)
			break;
2121 2122 2123 2124 2125
		nodes = max_group;
	}
	return nid;
}

2126 2127
static void task_numa_placement(struct task_struct *p)
{
2128 2129
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2130
	unsigned long fault_types[2] = { 0, 0 };
2131 2132
	unsigned long total_faults;
	u64 runtime, period;
2133
	spinlock_t *group_lock = NULL;
2134

2135 2136 2137 2138 2139
	/*
	 * 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:
	 */
2140
	seq = READ_ONCE(p->mm->numa_scan_seq);
2141 2142 2143
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2144
	p->numa_scan_period_max = task_scan_max(p);
2145

2146 2147 2148 2149
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2150 2151 2152
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2153
		spin_lock_irq(group_lock);
2154 2155
	}

2156 2157
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2158 2159
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2160
		unsigned long faults = 0, group_faults = 0;
2161
		int priv;
2162

2163
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2164
			long diff, f_diff, f_weight;
2165

2166 2167 2168 2169
			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);
2170

2171
			/* Decay existing window, copy faults since last scan */
2172 2173 2174
			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;
2175

2176 2177 2178 2179 2180 2181 2182 2183
			/*
			 * 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);
2184
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2185
				   (total_faults + 1);
2186 2187
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2188

2189 2190 2191
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2192
			p->total_numa_faults += diff;
2193
			if (p->numa_group) {
2194 2195 2196 2197 2198 2199 2200 2201 2202
				/*
				 * 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;
2203
				p->numa_group->total_faults += diff;
2204
				group_faults += p->numa_group->faults[mem_idx];
2205
			}
2206 2207
		}

2208 2209 2210 2211
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2212 2213 2214 2215 2216 2217 2218

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

2219 2220
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2221
	if (p->numa_group) {
2222
		numa_group_count_active_nodes(p->numa_group);
2223
		spin_unlock_irq(group_lock);
2224
		max_nid = preferred_group_nid(p, max_group_nid);
2225 2226
	}

2227 2228 2229 2230 2231 2232 2233
	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);
2234
	}
2235 2236
}

2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247
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);
}

2248 2249
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2250 2251 2252 2253 2254 2255 2256 2257 2258
{
	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) +
2259
				    4*nr_node_ids*sizeof(unsigned long);
2260 2261 2262 2263 2264 2265

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

		atomic_set(&grp->refcount, 1);
2266 2267
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2268
		spin_lock_init(&grp->lock);
2269
		grp->gid = p->pid;
2270
		/* Second half of the array tracks nids where faults happen */
2271 2272
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2273

2274
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2275
			grp->faults[i] = p->numa_faults[i];
2276

2277
		grp->total_faults = p->total_numa_faults;
2278

2279 2280 2281 2282 2283
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2284
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2285 2286

	if (!cpupid_match_pid(tsk, cpupid))
2287
		goto no_join;
2288 2289 2290

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2291
		goto no_join;
2292 2293 2294

	my_grp = p->numa_group;
	if (grp == my_grp)
2295
		goto no_join;
2296 2297 2298 2299 2300 2301

	/*
	 * 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)
2302
		goto no_join;
2303 2304 2305 2306 2307

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2308
		goto no_join;
2309

2310 2311 2312 2313 2314 2315 2316
	/* 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;
2317

2318 2319 2320
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2321
	if (join && !get_numa_group(grp))
2322
		goto no_join;
2323 2324 2325 2326 2327 2328

	rcu_read_unlock();

	if (!join)
		return;

2329 2330
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2331

2332
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2333 2334
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2335
	}
2336 2337
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2338 2339 2340 2341 2342

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

	spin_unlock(&my_grp->lock);
2343
	spin_unlock_irq(&grp->lock);
2344 2345 2346 2347

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2348 2349 2350 2351 2352
	return;

no_join:
	rcu_read_unlock();
	return;
2353 2354 2355 2356 2357
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2358
	void *numa_faults = p->numa_faults;
2359 2360
	unsigned long flags;
	int i;
2361 2362

	if (grp) {
2363
		spin_lock_irqsave(&grp->lock, flags);
2364
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2365
			grp->faults[i] -= p->numa_faults[i];
2366
		grp->total_faults -= p->total_numa_faults;
2367

2368
		grp->nr_tasks--;
2369
		spin_unlock_irqrestore(&grp->lock, flags);
2370
		RCU_INIT_POINTER(p->numa_group, NULL);
2371 2372 2373
		put_numa_group(grp);
	}

2374
	p->numa_faults = NULL;
2375
	kfree(numa_faults);
2376 2377
}

2378 2379 2380
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2381
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2382 2383
{
	struct task_struct *p = current;
2384
	bool migrated = flags & TNF_MIGRATED;
2385
	int cpu_node = task_node(current);
2386
	int local = !!(flags & TNF_FAULT_LOCAL);
2387
	struct numa_group *ng;
2388
	int priv;
2389

2390
	if (!static_branch_likely(&sched_numa_balancing))
2391 2392
		return;

2393 2394 2395 2396
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2397
	/* Allocate buffer to track faults on a per-node basis */
2398 2399
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2400
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2401

2402 2403
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2404
			return;
2405

2406
		p->total_numa_faults = 0;
2407
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2408
	}
2409

2410 2411 2412 2413 2414 2415 2416 2417
	/*
	 * 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);
2418
		if (!priv && !(flags & TNF_NO_GROUP))
2419
			task_numa_group(p, last_cpupid, flags, &priv);
2420 2421
	}

2422 2423 2424 2425 2426 2427
	/*
	 * 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.
	 */
2428 2429 2430 2431
	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))
2432 2433
		local = 1;

2434
	task_numa_placement(p);
2435

2436 2437 2438 2439 2440
	/*
	 * 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))
2441 2442
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2443 2444
	if (migrated)
		p->numa_pages_migrated += pages;
2445 2446
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2447

2448 2449
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2450
	p->numa_faults_locality[local] += pages;
2451 2452
}

2453 2454
static void reset_ptenuma_scan(struct task_struct *p)
{
2455 2456 2457 2458 2459 2460 2461 2462
	/*
	 * 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:
	 */
2463
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2464 2465 2466
	p->mm->numa_scan_offset = 0;
}

2467 2468 2469 2470 2471 2472 2473 2474 2475
/*
 * 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;
2476
	u64 runtime = p->se.sum_exec_runtime;
2477
	struct vm_area_struct *vma;
2478
	unsigned long start, end;
2479
	unsigned long nr_pte_updates = 0;
2480
	long pages, virtpages;
2481

2482
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495

	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;

2496
	if (!mm->numa_next_scan) {
2497 2498
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2499 2500
	}

2501 2502 2503 2504 2505 2506 2507
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2508 2509
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2510
		p->numa_scan_period = task_scan_start(p);
2511
	}
2512

2513
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2514 2515 2516
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2517 2518 2519 2520 2521 2522
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2523 2524 2525
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2526
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2527 2528
	if (!pages)
		return;
2529

2530

2531 2532
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2533
	vma = find_vma(mm, start);
2534 2535
	if (!vma) {
		reset_ptenuma_scan(p);
2536
		start = 0;
2537 2538
		vma = mm->mmap;
	}
2539
	for (; vma; vma = vma->vm_next) {
2540
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2541
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2542
			continue;
2543
		}
2544

2545 2546 2547 2548 2549 2550 2551 2552 2553 2554
		/*
		 * 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
2555 2556 2557 2558 2559 2560
		/*
		 * 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;
2561

2562 2563 2564 2565
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2566
			nr_pte_updates = change_prot_numa(vma, start, end);
2567 2568

			/*
2569 2570 2571 2572 2573 2574
			 * 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.
2575 2576 2577
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2578
			virtpages -= (end - start) >> PAGE_SHIFT;
2579

2580
			start = end;
2581
			if (pages <= 0 || virtpages <= 0)
2582
				goto out;
2583 2584

			cond_resched();
2585
		} while (end != vma->vm_end);
2586
	}
2587

2588
out:
2589
	/*
P
Peter Zijlstra 已提交
2590 2591 2592 2593
	 * 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.
2594 2595
	 */
	if (vma)
2596
		mm->numa_scan_offset = start;
2597 2598 2599
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610

	/*
	 * 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;
	}
2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635
}

/*
 * 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;

2636
	if (now > curr->node_stamp + period) {
2637
		if (!curr->node_stamp)
2638
			curr->numa_scan_period = task_scan_start(curr);
2639
		curr->node_stamp += period;
2640 2641 2642 2643 2644 2645 2646

		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);
		}
	}
}
2647

2648 2649 2650 2651
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2652 2653 2654 2655 2656 2657 2658 2659

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)
{
}
2660

2661 2662
#endif /* CONFIG_NUMA_BALANCING */

2663 2664 2665 2666
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2667
	if (!parent_entity(se))
2668
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2669
#ifdef CONFIG_SMP
2670 2671 2672 2673 2674 2675
	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);
	}
2676
#endif
2677 2678 2679 2680 2681 2682 2683
	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);
2684
	if (!parent_entity(se))
2685
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2686
#ifdef CONFIG_SMP
2687 2688
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2689
		list_del_init(&se->group_node);
2690
	}
2691
#endif
2692 2693 2694
	cfs_rq->nr_running--;
}

2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778
/*
 * Signed add and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define add_positive(_ptr, _val) do {                           \
	typeof(_ptr) ptr = (_ptr);                              \
	typeof(_val) val = (_val);                              \
	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
								\
	res = var + val;                                        \
								\
	if (val < 0 && res > var)                               \
		res = 0;                                        \
								\
	WRITE_ONCE(*ptr, res);                                  \
} while (0)

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

#ifdef CONFIG_SMP
/*
 * XXX we want to get rid of this helper and use the full load resolution.
 */
static inline long se_weight(struct sched_entity *se)
{
	return scale_load_down(se->load.weight);
}

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

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	sub_positive(&cfs_rq->runnable_load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->runnable_load_sum, se_weight(se) * se->avg.load_sum);
}

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

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

2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
		account_entity_dequeue(cfs_rq, se);
		dequeue_runnable_load_avg(cfs_rq, se);
	}
	dequeue_load_avg(cfs_rq, se);

	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
	se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum,
				   LOAD_AVG_MAX - 1024 + se->avg.period_contrib);
#endif

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

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

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

2816 2817
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 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
/*
 * All this does is approximate the hierarchical proportion which includes that
 * global sum we all love to hate.
 *
 * That is, the weight of a group entity, is the proportional share of the
 * group weight based on the group runqueue weights. That is:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------               (1)
 *			  \Sum grq->load.weight
 *
 * Now, because computing that sum is prohibitively expensive to compute (been
 * there, done that) we approximate it with this average stuff. The average
 * moves slower and therefore the approximation is cheaper and more stable.
 *
 * So instead of the above, we substitute:
 *
 *   grq->load.weight -> grq->avg.load_avg                         (2)
 *
 * which yields the following:
 *
 *                     tg->weight * grq->avg.load_avg
 *   ge->load.weight = ------------------------------              (3)
 *				tg->load_avg
 *
 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
 *
 * That is shares_avg, and it is right (given the approximation (2)).
 *
 * The problem with it is that because the average is slow -- it was designed
 * to be exactly that of course -- this leads to transients in boundary
 * conditions. In specific, the case where the group was idle and we start the
 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
 * yielding bad latency etc..
 *
 * Now, in that special case (1) reduces to:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = ----------------------------- = tg>weight   (4)
 *			    grp->load.weight
 *
 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
 *
 * So what we do is modify our approximation (3) to approach (4) in the (near)
 * UP case, like:
 *
 *   ge->load.weight =
 *
 *              tg->weight * grq->load.weight
 *     ---------------------------------------------------         (5)
 *     tg->load_avg - grq->avg.load_avg + grq->load.weight
 *
 *
 * And that is shares_weight and is icky. In the (near) UP case it approaches
 * (4) while in the normal case it approaches (3). It consistently
 * overestimates the ge->load.weight and therefore:
 *
 *   \Sum ge->load.weight >= tg->weight
 *
 * hence icky!
 */
2879
static long calc_cfs_shares(struct cfs_rq *cfs_rq)
2880
{
2881 2882 2883 2884
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2885 2886

	/*
2887 2888
	 * Because (5) drops to 0 when the cfs_rq is idle, we need to use (3)
	 * as a lower bound.
2889
	 */
2890
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2891

2892
	tg_weight = atomic_long_read(&tg->load_avg);
2893

2894 2895 2896
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2897

2898
	shares = (tg_shares * load);
2899 2900
	if (tg_weight)
		shares /= tg_weight;
2901

2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913
	/*
	 * 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.
	 */
2914
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
2915 2916
}
# endif /* CONFIG_SMP */
2917

2918 2919
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2920
static void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2921
{
2922
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
2923
	long shares;
P
Peter Zijlstra 已提交
2924

2925 2926 2927 2928
	if (!cfs_rq)
		return;

	if (throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2929
		return;
2930

2931
#ifndef CONFIG_SMP
2932 2933 2934
	shares = READ_ONCE(cfs_rq->tg->shares);

	if (likely(se->load.weight == shares))
2935
		return;
2936 2937
#else
	shares = calc_cfs_shares(cfs_rq);
2938
#endif
P
Peter Zijlstra 已提交
2939 2940 2941

	reweight_entity(cfs_rq_of(se), se, shares);
}
2942

P
Peter Zijlstra 已提交
2943
#else /* CONFIG_FAIR_GROUP_SCHED */
2944
static inline void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2945 2946 2947 2948
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2949 2950
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
2951 2952 2953
	struct rq *rq = rq_of(cfs_rq);

	if (&rq->cfs == cfs_rq) {
2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969
		/*
		 * 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().
		 */
2970
		cpufreq_update_util(rq, 0);
2971 2972 2973
	}
}

2974
#ifdef CONFIG_SMP
2975 2976 2977 2978
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
2979
static u64 decay_load(u64 val, u64 n)
2980
{
2981 2982
	unsigned int local_n;

2983
	if (unlikely(n > LOAD_AVG_PERIOD * 63))
2984 2985 2986 2987 2988 2989 2990
		return 0;

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

	/*
	 * As y^PERIOD = 1/2, we can combine
2991 2992
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2993 2994 2995 2996 2997 2998
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2999 3000
	}

3001 3002
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
3003 3004
}

3005
static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
3006
{
3007
	u32 c1, c2, c3 = d3; /* y^0 == 1 */
3008

3009
	/*
P
Peter Zijlstra 已提交
3010
	 * c1 = d1 y^p
3011
	 */
3012
	c1 = decay_load((u64)d1, periods);
3013 3014

	/*
P
Peter Zijlstra 已提交
3015
	 *            p-1
3016 3017
	 * c2 = 1024 \Sum y^n
	 *            n=1
3018
	 *
3019 3020
	 *              inf        inf
	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
P
Peter Zijlstra 已提交
3021
	 *              n=0        n=p
3022
	 */
3023
	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
3024 3025

	return c1 + c2 + c3;
3026 3027
}

3028
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
3029

3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040
/*
 * 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
3041 3042 3043
 *                           p-1
 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
 *                           n=1
3044
 *
P
Peter Zijlstra 已提交
3045
 *    = u y^p +					(Step 1)
3046
 *
P
Peter Zijlstra 已提交
3047 3048 3049
 *                     p-1
 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2)
 *                     n=1
3050 3051 3052 3053 3054 3055
 */
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;
3056
	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075
	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);

3076 3077 3078 3079 3080 3081 3082
		/*
		 * Step 2
		 */
		delta %= 1024;
		contrib = __accumulate_pelt_segments(periods,
				1024 - sa->period_contrib, delta);
	}
3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096
	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;
}

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
/*
 * 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}]
 */
3125
static __always_inline int
3126 3127
___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
		   unsigned long weight, int running, struct cfs_rq *cfs_rq)
3128
{
3129
	u64 delta;
3130

3131
	delta = now - sa->last_update_time;
3132 3133 3134 3135 3136
	/*
	 * 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) {
3137
		sa->last_update_time = now;
3138 3139 3140 3141 3142 3143 3144 3145 3146 3147
		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;
3148 3149

	sa->last_update_time += delta << 10;
3150

3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162
	/*
	 * running is a subset of runnable (weight) so running can't be set if
	 * runnable is clear. But there are some corner cases where the current
	 * se has been already dequeued but cfs_rq->curr still points to it.
	 * This means that weight will be 0 but not running for a sched_entity
	 * but also for a cfs_rq if the latter becomes idle. As an example,
	 * this happens during idle_balance() which calls
	 * update_blocked_averages()
	 */
	if (!weight)
		running = 0;

3163 3164 3165 3166 3167 3168 3169 3170 3171
	/*
	 * 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;
3172

3173 3174 3175 3176 3177 3178 3179 3180
	return 1;
}

static __always_inline void
___update_load_avg(struct sched_avg *sa, unsigned long weight, struct cfs_rq *cfs_rq)
{
	u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;

3181 3182 3183
	/*
	 * Step 2: update *_avg.
	 */
3184
	sa->load_avg = div_u64(weight * sa->load_sum, divider);
3185 3186
	if (cfs_rq) {
		cfs_rq->runnable_load_avg =
3187
			div_u64(cfs_rq->runnable_load_sum, divider);
3188
	}
3189 3190
	sa->util_avg = sa->util_sum / divider;
}
3191

3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203
/*
 * sched_entity:
 *
 *   load_sum := runnable_sum
 *   load_avg = se_weight(se) * runnable_avg
 *
 * cfq_rs:
 *
 *   load_sum = \Sum se_weight(se) * se->avg.load_sum
 *   load_avg = \Sum se->avg.load_avg
 */

3204 3205 3206
static int
__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
{
3207 3208 3209 3210 3211 3212
	if (___update_load_sum(now, cpu, &se->avg, 0, 0, NULL)) {
		___update_load_avg(&se->avg, se_weight(se), NULL);
		return 1;
	}

	return 0;
3213 3214 3215 3216 3217
}

static int
__update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3218 3219 3220 3221 3222 3223 3224 3225
	if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq,
				cfs_rq->curr == se, NULL)) {

		___update_load_avg(&se->avg, se_weight(se), NULL);
		return 1;
	}

	return 0;
3226 3227 3228 3229 3230
}

static int
__update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
{
3231 3232 3233 3234 3235 3236 3237 3238
	if (___update_load_sum(now, cpu, &cfs_rq->avg,
				scale_load_down(cfs_rq->load.weight),
				cfs_rq->curr != NULL, cfs_rq)) {
		___update_load_avg(&cfs_rq->avg, 1, cfs_rq);
		return 1;
	}

	return 0;
3239 3240
}

3241
#ifdef CONFIG_FAIR_GROUP_SCHED
3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254
/**
 * 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'.
 *
3255
 * Updating tg's load_avg is necessary before update_cfs_share().
3256
 */
3257
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3258
{
3259
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3260

3261 3262 3263 3264 3265 3266
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3267 3268 3269
	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;
3270
	}
3271
}
3272

3273 3274 3275 3276 3277 3278 3279 3280
/*
 * 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)
{
3281 3282 3283
	u64 p_last_update_time;
	u64 n_last_update_time;

3284 3285 3286 3287 3288 3289 3290 3291 3292 3293
	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.
	 */
3294 3295
	if (!(se->avg.last_update_time && prev))
		return;
3296 3297

#ifndef CONFIG_64BIT
3298
	{
3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312
		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);
3313
	}
3314
#else
3315 3316
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3317
#endif
3318 3319
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3320
}
3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387

/* 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;
3388
	se->avg.load_sum = LOAD_AVG_MAX;
3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441

	/* 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;
}

3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471
/*
 * 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;
}

3472
#else /* CONFIG_FAIR_GROUP_SCHED */
3473

3474
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3475 3476 3477 3478 3479 3480 3481 3482

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) {}

3483
#endif /* CONFIG_FAIR_GROUP_SCHED */
3484

3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495
/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_task()
 * @cfs_rq: cfs_rq to update
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
3496 3497 3498 3499
 * 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.
3500
 */
3501
static inline int
3502
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3503
{
3504
	struct sched_avg *sa = &cfs_rq->avg;
3505
	int decayed, removed_load = 0, removed_util = 0;
3506

3507
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
3508
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
3509 3510
		sub_positive(&sa->load_avg, r);
		sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
3511
		removed_load = 1;
3512
		set_tg_cfs_propagate(cfs_rq);
3513
	}
3514

3515 3516
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
3517 3518
		sub_positive(&sa->util_avg, r);
		sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
3519
		removed_util = 1;
3520
		set_tg_cfs_propagate(cfs_rq);
3521
	}
3522

3523
	decayed = __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3524

3525 3526 3527 3528
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3529

3530
	if (decayed || removed_util)
3531
		cfs_rq_util_change(cfs_rq);
3532

3533
	return decayed || removed_load;
3534 3535
}

3536 3537 3538 3539 3540 3541 3542 3543
/**
 * 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.
 */
3544 3545 3546
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;
3547
	enqueue_load_avg(cfs_rq, se);
3548 3549
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3550
	set_tg_cfs_propagate(cfs_rq);
3551 3552

	cfs_rq_util_change(cfs_rq);
3553 3554
}

3555 3556 3557 3558 3559 3560 3561 3562
/**
 * 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.
 */
3563 3564
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3565
	dequeue_load_avg(cfs_rq, se);
3566 3567
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3568
	set_tg_cfs_propagate(cfs_rq);
3569 3570

	cfs_rq_util_change(cfs_rq);
3571 3572
}

3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2
#define DO_ATTACH	0x4

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

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

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

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

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

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

3607
#ifndef CONFIG_64BIT
3608 3609
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3610
	u64 last_update_time_copy;
3611
	u64 last_update_time;
3612

3613 3614 3615 3616 3617
	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);
3618 3619 3620

	return last_update_time;
}
3621
#else
3622 3623 3624 3625
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3626 3627
#endif

3628 3629 3630 3631 3632 3633 3634 3635 3636 3637
/*
 * 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);
3638
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3639 3640
}

3641 3642 3643 3644 3645 3646 3647 3648 3649
/*
 * 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);

	/*
3650 3651 3652 3653 3654 3655 3656
	 * 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.
3657 3658
	 */

3659
	sync_entity_load_avg(se);
3660 3661
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3662
}
3663

3664 3665 3666 3667 3668 3669 3670 3671 3672 3673
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;
}

3674
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3675

3676 3677
#else /* CONFIG_SMP */

3678
static inline int
3679
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3680 3681 3682 3683
{
	return 0;
}

3684 3685
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3686
#define DO_ATTACH	0x0
3687

3688
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3689
{
3690
	cfs_rq_util_change(cfs_rq);
3691 3692
}

3693
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3694

3695 3696 3697 3698 3699
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) {}

3700
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3701 3702 3703 3704
{
	return 0;
}

3705
#endif /* CONFIG_SMP */
3706

P
Peter Zijlstra 已提交
3707 3708 3709 3710 3711 3712 3713 3714 3715
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)
3716
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3717 3718 3719
#endif
}

3720 3721 3722
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3723
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3724

3725 3726 3727 3728 3729 3730
	/*
	 * 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
3731
	if (initial && sched_feat(START_DEBIT))
3732
		vruntime += sched_vslice(cfs_rq, se);
3733

3734
	/* sleeps up to a single latency don't count. */
3735
	if (!initial) {
3736
		unsigned long thresh = sysctl_sched_latency;
3737

3738 3739 3740 3741 3742 3743
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3744

3745
		vruntime -= thresh;
3746 3747
	}

3748
	/* ensure we never gain time by being placed backwards. */
3749
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3750 3751
}

3752 3753
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765
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())  {
3766
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3767
			     "stat_blocked and stat_runtime require the "
3768
			     "kernel parameter schedstats=enable or "
3769 3770 3771 3772 3773
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792

/*
 * 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)
 *
3793
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804
 *	  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.
 */

3805
static void
3806
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3807
{
3808 3809 3810
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3811
	/*
3812 3813
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3814
	 */
3815
	if (renorm && curr)
3816 3817
		se->vruntime += cfs_rq->min_vruntime;

3818 3819
	update_curr(cfs_rq);

3820
	/*
3821 3822 3823 3824
	 * 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.
3825
	 */
3826 3827 3828
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3829 3830 3831 3832 3833 3834 3835 3836
	/*
	 * 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
	 */
3837
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3838
	enqueue_runnable_load_avg(cfs_rq, se);
3839
	update_cfs_shares(se);
3840
	account_entity_enqueue(cfs_rq, se);
3841

3842
	if (flags & ENQUEUE_WAKEUP)
3843
		place_entity(cfs_rq, se, 0);
3844

3845
	check_schedstat_required();
3846 3847
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3848
	if (!curr)
3849
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3850
	se->on_rq = 1;
3851

3852
	if (cfs_rq->nr_running == 1) {
3853
		list_add_leaf_cfs_rq(cfs_rq);
3854 3855
		check_enqueue_throttle(cfs_rq);
	}
3856 3857
}

3858
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3859
{
3860 3861
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3862
		if (cfs_rq->last != se)
3863
			break;
3864 3865

		cfs_rq->last = NULL;
3866 3867
	}
}
P
Peter Zijlstra 已提交
3868

3869 3870 3871 3872
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3873
		if (cfs_rq->next != se)
3874
			break;
3875 3876

		cfs_rq->next = NULL;
3877
	}
P
Peter Zijlstra 已提交
3878 3879
}

3880 3881 3882 3883
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3884
		if (cfs_rq->skip != se)
3885
			break;
3886 3887

		cfs_rq->skip = NULL;
3888 3889 3890
	}
}

P
Peter Zijlstra 已提交
3891 3892
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3893 3894 3895 3896 3897
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3898 3899 3900

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3901 3902
}

3903
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3904

3905
static void
3906
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3907
{
3908 3909 3910 3911
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3912 3913 3914 3915 3916 3917 3918 3919 3920

	/*
	 * 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.
	 */
3921
	update_load_avg(cfs_rq, se, UPDATE_TG);
3922
	dequeue_runnable_load_avg(cfs_rq, se);
3923

3924
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3925

P
Peter Zijlstra 已提交
3926
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3927

3928
	if (se != cfs_rq->curr)
3929
		__dequeue_entity(cfs_rq, se);
3930
	se->on_rq = 0;
3931
	account_entity_dequeue(cfs_rq, se);
3932 3933

	/*
3934 3935 3936 3937
	 * 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.
3938
	 */
3939
	if (!(flags & DEQUEUE_SLEEP))
3940
		se->vruntime -= cfs_rq->min_vruntime;
3941

3942 3943 3944
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3945
	update_cfs_shares(se);
3946 3947 3948 3949 3950 3951 3952 3953 3954

	/*
	 * 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);
3955 3956 3957 3958 3959
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3960
static void
I
Ingo Molnar 已提交
3961
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3962
{
3963
	unsigned long ideal_runtime, delta_exec;
3964 3965
	struct sched_entity *se;
	s64 delta;
3966

P
Peter Zijlstra 已提交
3967
	ideal_runtime = sched_slice(cfs_rq, curr);
3968
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3969
	if (delta_exec > ideal_runtime) {
3970
		resched_curr(rq_of(cfs_rq));
3971 3972 3973 3974 3975
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986
		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;

3987 3988
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3989

3990 3991
	if (delta < 0)
		return;
3992

3993
	if (delta > ideal_runtime)
3994
		resched_curr(rq_of(cfs_rq));
3995 3996
}

3997
static void
3998
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3999
{
4000 4001 4002 4003 4004 4005 4006
	/* '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.
		 */
4007
		update_stats_wait_end(cfs_rq, se);
4008
		__dequeue_entity(cfs_rq, se);
4009
		update_load_avg(cfs_rq, se, UPDATE_TG);
4010 4011
	}

4012
	update_stats_curr_start(cfs_rq, se);
4013
	cfs_rq->curr = se;
4014

I
Ingo Molnar 已提交
4015 4016 4017 4018 4019
	/*
	 * 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):
	 */
4020
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4021 4022 4023
		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
4024
	}
4025

4026
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4027 4028
}

4029 4030 4031
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4032 4033 4034 4035 4036 4037 4038
/*
 * 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
 */
4039 4040
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4041
{
4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052
	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 */
4053

4054 4055 4056 4057 4058
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4059 4060 4061 4062 4063 4064 4065 4066 4067 4068
		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;
		}

4069 4070 4071
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4072

4073 4074 4075 4076 4077 4078
	/*
	 * 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;

4079 4080 4081 4082 4083 4084
	/*
	 * 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;

4085
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4086 4087

	return se;
4088 4089
}

4090
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4091

4092
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4093 4094 4095 4096 4097 4098
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4099
		update_curr(cfs_rq);
4100

4101 4102 4103
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4104
	check_spread(cfs_rq, prev);
4105

4106
	if (prev->on_rq) {
4107
		update_stats_wait_start(cfs_rq, prev);
4108 4109
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4110
		/* in !on_rq case, update occurred at dequeue */
4111
		update_load_avg(cfs_rq, prev, 0);
4112
	}
4113
	cfs_rq->curr = NULL;
4114 4115
}

P
Peter Zijlstra 已提交
4116 4117
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4118 4119
{
	/*
4120
	 * Update run-time statistics of the 'current'.
4121
	 */
4122
	update_curr(cfs_rq);
4123

4124 4125 4126
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4127
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4128
	update_cfs_shares(curr);
4129

P
Peter Zijlstra 已提交
4130 4131 4132 4133 4134
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4135
	if (queued) {
4136
		resched_curr(rq_of(cfs_rq));
4137 4138
		return;
	}
P
Peter Zijlstra 已提交
4139 4140 4141 4142 4143 4144 4145 4146
	/*
	 * 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
4147
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4148
		check_preempt_tick(cfs_rq, curr);
4149 4150
}

4151 4152 4153 4154 4155 4156

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

#ifdef CONFIG_CFS_BANDWIDTH
4157 4158

#ifdef HAVE_JUMP_LABEL
4159
static struct static_key __cfs_bandwidth_used;
4160 4161 4162

static inline bool cfs_bandwidth_used(void)
{
4163
	return static_key_false(&__cfs_bandwidth_used);
4164 4165
}

4166
void cfs_bandwidth_usage_inc(void)
4167
{
4168 4169 4170 4171 4172 4173
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
4174 4175 4176 4177 4178 4179 4180
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4181 4182
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4183 4184
#endif /* HAVE_JUMP_LABEL */

4185 4186 4187 4188 4189 4190 4191 4192
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4193 4194 4195 4196 4197 4198

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

P
Paul Turner 已提交
4199 4200 4201 4202 4203 4204 4205
/*
 * 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
 */
4206
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217
{
	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);
}

4218 4219 4220 4221 4222
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4223 4224 4225 4226
/* 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))
4227
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4228

4229
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4230 4231
}

4232 4233
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4234 4235 4236
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4237
	u64 amount = 0, min_amount, expires;
4238 4239 4240 4241 4242 4243 4244

	/* 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;
4245
	else {
P
Peter Zijlstra 已提交
4246
		start_cfs_bandwidth(cfs_b);
4247 4248 4249 4250 4251 4252

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4253
	}
P
Paul Turner 已提交
4254
	expires = cfs_b->runtime_expires;
4255 4256 4257
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4258 4259 4260 4261 4262 4263 4264
	/*
	 * 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;
4265 4266

	return cfs_rq->runtime_remaining > 0;
4267 4268
}

P
Paul Turner 已提交
4269 4270 4271 4272 4273
/*
 * 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)
4274
{
P
Paul Turner 已提交
4275 4276 4277
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4278
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4279 4280
		return;

P
Paul Turner 已提交
4281 4282 4283 4284 4285 4286 4287 4288 4289
	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
4290 4291 4292
	 * 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
4293 4294
	 */

4295
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
4296 4297 4298 4299 4300 4301 4302 4303
		/* 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;
	}
}

4304
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4305 4306
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4307
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4308 4309 4310
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4311 4312
		return;

4313 4314 4315 4316 4317
	/*
	 * 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))
4318
		resched_curr(rq_of(cfs_rq));
4319 4320
}

4321
static __always_inline
4322
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4323
{
4324
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4325 4326 4327 4328 4329
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4330 4331
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4332
	return cfs_bandwidth_used() && cfs_rq->throttled;
4333 4334
}

4335 4336 4337
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4338
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365
}

/*
 * 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) {
4366
		/* adjust cfs_rq_clock_task() */
4367
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4368
					     cfs_rq->throttled_clock_task;
4369 4370 4371 4372 4373 4374 4375 4376 4377 4378
	}

	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)];

4379 4380
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4381
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4382 4383 4384 4385 4386
	cfs_rq->throttle_count++;

	return 0;
}

4387
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4388 4389 4390 4391 4392
{
	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
4393
	bool empty;
4394 4395 4396

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

4397
	/* freeze hierarchy runnable averages while throttled */
4398 4399 4400
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417

	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)
4418
		sub_nr_running(rq, task_delta);
4419 4420

	cfs_rq->throttled = 1;
4421
	cfs_rq->throttled_clock = rq_clock(rq);
4422
	raw_spin_lock(&cfs_b->lock);
4423
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4424

4425 4426 4427 4428 4429
	/*
	 * 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
4430 4431 4432 4433 4434 4435 4436 4437

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

4438 4439 4440
	raw_spin_unlock(&cfs_b->lock);
}

4441
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4442 4443 4444 4445 4446 4447 4448
{
	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;

4449
	se = cfs_rq->tg->se[cpu_of(rq)];
4450 4451

	cfs_rq->throttled = 0;
4452 4453 4454

	update_rq_clock(rq);

4455
	raw_spin_lock(&cfs_b->lock);
4456
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4457 4458 4459
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4460 4461 4462
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480
	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)
4481
		add_nr_running(rq, task_delta);
4482 4483 4484

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4485
		resched_curr(rq);
4486 4487 4488 4489 4490 4491
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4492 4493
	u64 runtime;
	u64 starting_runtime = remaining;
4494 4495 4496 4497 4498

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4499
		struct rq_flags rf;
4500

4501
		rq_lock(rq, &rf);
4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517
		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:
4518
		rq_unlock(rq, &rf);
4519 4520 4521 4522 4523 4524

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

4525
	return starting_runtime - remaining;
4526 4527
}

4528 4529 4530 4531 4532 4533 4534 4535
/*
 * 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)
{
4536
	u64 runtime, runtime_expires;
4537
	int throttled;
4538 4539 4540

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4541
		goto out_deactivate;
4542

4543
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4544
	cfs_b->nr_periods += overrun;
4545

4546 4547 4548 4549 4550 4551
	/*
	 * 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
4552 4553 4554

	__refill_cfs_bandwidth_runtime(cfs_b);

4555 4556 4557
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4558
		return 0;
4559 4560
	}

4561 4562 4563
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4564 4565 4566
	runtime_expires = cfs_b->runtime_expires;

	/*
4567 4568 4569 4570 4571
	 * 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.
4572
	 */
4573 4574
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4575 4576 4577 4578 4579 4580 4581
		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);
4582 4583

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4584
	}
4585

4586 4587 4588 4589 4590 4591 4592
	/*
	 * 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;
4593

4594 4595 4596 4597
	return 0;

out_deactivate:
	return 1;
4598
}
4599

4600 4601 4602 4603 4604 4605 4606
/* 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;

4607 4608 4609 4610
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4611
 * hrtimer base being cleared by hrtimer_start. In the case of
4612 4613
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638
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
4639 4640 4641
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670
}

/* 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)
{
4671 4672 4673
	if (!cfs_bandwidth_used())
		return;

4674
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689
		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 */
4690 4691 4692
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4693
		return;
4694
	}
4695

4696
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4697
		runtime = cfs_b->runtime;
4698

4699 4700 4701 4702 4703 4704 4705 4706 4707 4708
	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)
4709
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4710 4711 4712
	raw_spin_unlock(&cfs_b->lock);
}

4713 4714 4715 4716 4717 4718 4719
/*
 * 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)
{
4720 4721 4722
	if (!cfs_bandwidth_used())
		return;

4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736
	/* 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);
}

4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750
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;
4751
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4752 4753
}

4754
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4755
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4756
{
4757
	if (!cfs_bandwidth_used())
4758
		return false;
4759

4760
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4761
		return false;
4762 4763 4764 4765 4766 4767

	/*
	 * 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))
4768
		return true;
4769 4770

	throttle_cfs_rq(cfs_rq);
4771
	return true;
4772
}
4773 4774 4775 4776 4777

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
4778

4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790
	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;

4791
	raw_spin_lock(&cfs_b->lock);
4792
	for (;;) {
P
Peter Zijlstra 已提交
4793
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4794 4795 4796 4797 4798
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4799 4800
	if (idle)
		cfs_b->period_active = 0;
4801
	raw_spin_unlock(&cfs_b->lock);
4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

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

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
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Peter Zijlstra 已提交
4814
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

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

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Peter Zijlstra 已提交
4826
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4827
{
P
Peter Zijlstra 已提交
4828
	lockdep_assert_held(&cfs_b->lock);
4829

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Peter Zijlstra 已提交
4830 4831 4832 4833 4834
	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);
	}
4835 4836 4837 4838
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4839 4840 4841 4842
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4843 4844 4845 4846
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4847 4848 4849 4850 4851 4852 4853 4854
/*
 * 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 */
4855 4856
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4857
	struct task_group *tg;
4858

4859 4860 4861 4862 4863 4864
	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)];
4865 4866 4867 4868 4869

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4870
	rcu_read_unlock();
4871 4872
}

4873
/* cpu offline callback */
4874
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4875
{
4876 4877 4878 4879 4880 4881 4882
	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)];
4883 4884 4885 4886 4887 4888 4889 4890

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4891
		cfs_rq->runtime_remaining = 1;
4892 4893 4894 4895 4896 4897
		/*
		 * 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;

4898 4899 4900
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
4901
	rcu_read_unlock();
4902 4903 4904
}

#else /* CONFIG_CFS_BANDWIDTH */
4905 4906
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4907
	return rq_clock_task(rq_of(cfs_rq));
4908 4909
}

4910
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4911
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4912
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4913
static inline void sync_throttle(struct task_group *tg, int cpu) {}
4914
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4915 4916 4917 4918 4919

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930

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;
}
4931 4932 4933 4934 4935

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) {}
4936 4937
#endif

4938 4939 4940 4941 4942
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) {}
4943
static inline void update_runtime_enabled(struct rq *rq) {}
4944
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4945 4946 4947

#endif /* CONFIG_CFS_BANDWIDTH */

4948 4949 4950 4951
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4952 4953 4954 4955 4956 4957
#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);

4958
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
4959

4960
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
4961 4962 4963 4964 4965 4966
		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)
4967
				resched_curr(rq);
P
Peter Zijlstra 已提交
4968 4969
			return;
		}
4970
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4971 4972
	}
}
4973 4974 4975 4976 4977 4978 4979 4980 4981 4982

/*
 * 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;

4983
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4984 4985 4986 4987 4988
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4989
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
4990 4991 4992 4993
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4994 4995 4996 4997

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4998 4999
#endif

5000 5001 5002 5003 5004
/*
 * 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:
 */
5005
static void
5006
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5007 5008
{
	struct cfs_rq *cfs_rq;
5009
	struct sched_entity *se = &p->se;
5010

5011 5012 5013 5014 5015 5016
	/*
	 * 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)
5017
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5018

5019
	for_each_sched_entity(se) {
5020
		if (se->on_rq)
5021 5022
			break;
		cfs_rq = cfs_rq_of(se);
5023
		enqueue_entity(cfs_rq, se, flags);
5024 5025 5026 5027 5028 5029

		/*
		 * 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.
5030
		 */
5031 5032
		if (cfs_rq_throttled(cfs_rq))
			break;
5033
		cfs_rq->h_nr_running++;
5034

5035
		flags = ENQUEUE_WAKEUP;
5036
	}
P
Peter Zijlstra 已提交
5037

P
Peter Zijlstra 已提交
5038
	for_each_sched_entity(se) {
5039
		cfs_rq = cfs_rq_of(se);
5040
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5041

5042 5043 5044
		if (cfs_rq_throttled(cfs_rq))
			break;

5045
		update_load_avg(cfs_rq, se, UPDATE_TG);
5046
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
5047 5048
	}

Y
Yuyang Du 已提交
5049
	if (!se)
5050
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5051

5052
	hrtick_update(rq);
5053 5054
}

5055 5056
static void set_next_buddy(struct sched_entity *se);

5057 5058 5059 5060 5061
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5062
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5063 5064
{
	struct cfs_rq *cfs_rq;
5065
	struct sched_entity *se = &p->se;
5066
	int task_sleep = flags & DEQUEUE_SLEEP;
5067 5068 5069

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5070
		dequeue_entity(cfs_rq, se, flags);
5071 5072 5073 5074 5075 5076 5077 5078 5079

		/*
		 * 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;
5080
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5081

5082
		/* Don't dequeue parent if it has other entities besides us */
5083
		if (cfs_rq->load.weight) {
5084 5085
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5086 5087 5088 5089
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5090 5091
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5092
			break;
5093
		}
5094
		flags |= DEQUEUE_SLEEP;
5095
	}
P
Peter Zijlstra 已提交
5096

P
Peter Zijlstra 已提交
5097
	for_each_sched_entity(se) {
5098
		cfs_rq = cfs_rq_of(se);
5099
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5100

5101 5102 5103
		if (cfs_rq_throttled(cfs_rq))
			break;

5104
		update_load_avg(cfs_rq, se, UPDATE_TG);
5105
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
5106 5107
	}

Y
Yuyang Du 已提交
5108
	if (!se)
5109
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5110

5111
	hrtick_update(rq);
5112 5113
}

5114
#ifdef CONFIG_SMP
5115 5116 5117 5118 5119

/* 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);

5120
#ifdef CONFIG_NO_HZ_COMMON
5121 5122 5123 5124 5125
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5126
 * The exact cpuload calculated at every tick would be:
5127
 *
5128 5129 5130 5131 5132 5133 5134
 *   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
5135 5136 5137
 *
 * decay_load_missed() below does efficient calculation of
 *
5138 5139 5140 5141 5142 5143
 *   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())
5144
 *
5145
 * The calculation is approximated on a 128 point scale.
5146 5147
 */
#define DEGRADE_SHIFT		7
5148 5149 5150 5151 5152 5153 5154 5155 5156

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 }
};
5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185

/*
 * 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;
}
5186
#endif /* CONFIG_NO_HZ_COMMON */
5187

5188
/**
5189
 * __cpu_load_update - update the rq->cpu_load[] statistics
5190 5191 5192 5193
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5194
 * Update rq->cpu_load[] statistics. This function is usually called every
5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220
 * 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
5221
 * term.
5222
 */
5223 5224
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5225
{
5226
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237
	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 */

5238
		old_load = this_rq->cpu_load[i];
5239
#ifdef CONFIG_NO_HZ_COMMON
5240
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5241 5242 5243 5244 5245 5246 5247 5248 5249
		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;
		}
5250
#endif
5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265
		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);
}

5266
/* Used instead of source_load when we know the type == 0 */
5267
static unsigned long weighted_cpuload(struct rq *rq)
5268
{
5269
	return cfs_rq_runnable_load_avg(&rq->cfs);
5270 5271
}

5272
#ifdef CONFIG_NO_HZ_COMMON
5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289
/*
 * 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)
5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300
{
	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.
		 */
5301
		cpu_load_update(this_rq, load, pending_updates);
5302 5303 5304
	}
}

5305 5306 5307 5308
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5309
static void cpu_load_update_idle(struct rq *this_rq)
5310 5311 5312 5313
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5314
	if (weighted_cpuload(this_rq))
5315 5316
		return;

5317
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5318 5319 5320
}

/*
5321 5322 5323 5324
 * 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.
5325
 */
5326
void cpu_load_update_nohz_start(void)
5327 5328
{
	struct rq *this_rq = this_rq();
5329 5330 5331 5332 5333 5334

	/*
	 * 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.
	 */
5335
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5336 5337 5338 5339 5340 5341 5342
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5343
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5344 5345
	struct rq *this_rq = this_rq();
	unsigned long load;
5346
	struct rq_flags rf;
5347 5348 5349 5350

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

5351
	load = weighted_cpuload(this_rq);
5352
	rq_lock(this_rq, &rf);
5353
	update_rq_clock(this_rq);
5354
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5355
	rq_unlock(this_rq, &rf);
5356
}
5357 5358 5359 5360 5361 5362 5363 5364
#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)
{
5365
#ifdef CONFIG_NO_HZ_COMMON
5366 5367
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5368
#endif
5369 5370
	cpu_load_update(this_rq, load, 1);
}
5371 5372 5373 5374

/*
 * Called from scheduler_tick()
 */
5375
void cpu_load_update_active(struct rq *this_rq)
5376
{
5377
	unsigned long load = weighted_cpuload(this_rq);
5378 5379 5380 5381 5382

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5383 5384
}

5385 5386 5387 5388 5389 5390 5391 5392 5393 5394
/*
 * 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);
5395
	unsigned long total = weighted_cpuload(rq);
5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409

	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);
5410
	unsigned long total = weighted_cpuload(rq);
5411 5412 5413 5414 5415 5416 5417

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

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

5418
static unsigned long capacity_of(int cpu)
5419
{
5420
	return cpu_rq(cpu)->cpu_capacity;
5421 5422
}

5423 5424 5425 5426 5427
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5428 5429 5430
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5431
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5432
	unsigned long load_avg = weighted_cpuload(rq);
5433 5434

	if (nr_running)
5435
		return load_avg / nr_running;
5436 5437 5438 5439

	return 0;
}

P
Peter Zijlstra 已提交
5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456
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
5457 5458
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5459
 *
M
Mike Galbraith 已提交
5460
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472
 * 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
5473
 */
5474 5475
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5476 5477
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5478
	int factor = this_cpu_read(sd_llc_size);
5479

M
Mike Galbraith 已提交
5480 5481 5482 5483 5484
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5485 5486
}

5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554
struct llc_stats {
	unsigned long	nr_running;
	unsigned long	load;
	unsigned long	capacity;
	int		has_capacity;
};

static bool get_llc_stats(struct llc_stats *stats, int cpu)
{
	struct sched_domain_shared *sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));

	if (!sds)
		return false;

	stats->nr_running	= READ_ONCE(sds->nr_running);
	stats->load		= READ_ONCE(sds->load);
	stats->capacity		= READ_ONCE(sds->capacity);
	stats->has_capacity	= stats->nr_running < per_cpu(sd_llc_size, cpu);

	return true;
}

/*
 * Can a task be moved from prev_cpu to this_cpu without causing a load
 * imbalance that would trigger the load balancer?
 *
 * Since we're running on 'stale' values, we might in fact create an imbalance
 * but recomputing these values is expensive, as that'd mean iteration 2 cache
 * domains worth of CPUs.
 */
static bool
wake_affine_llc(struct sched_domain *sd, struct task_struct *p,
		int this_cpu, int prev_cpu, int sync)
{
	struct llc_stats prev_stats, this_stats;
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

	if (!get_llc_stats(&prev_stats, prev_cpu) ||
	    !get_llc_stats(&this_stats, this_cpu))
		return false;

	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current LLC.
	 */
	if (sync) {
		unsigned long current_load = task_h_load(current);

		/* in this case load hits 0 and this LLC is considered 'idle' */
		if (current_load > this_stats.load)
			return true;

		this_stats.load -= current_load;
	}

	/*
	 * The has_capacity stuff is not SMT aware, but by trying to balance
	 * the nr_running on both ends we try and fill the domain at equal
	 * rates, thereby first consuming cores before siblings.
	 */

	/* if the old cache has capacity, stay there */
	if (prev_stats.has_capacity && prev_stats.nr_running < this_stats.nr_running+1)
		return false;

	/* if this cache has capacity, come here */
5555
	if (this_stats.has_capacity && this_stats.nr_running+1 < prev_stats.nr_running)
5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575
		return true;

	/*
	 * Check to see if we can move the load without causing too much
	 * imbalance.
	 */
	task_load = task_h_load(p);

	this_eff_load = 100;
	this_eff_load *= prev_stats.capacity;

	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= this_stats.capacity;

	this_eff_load *= this_stats.load + task_load;
	prev_eff_load *= prev_stats.load - task_load;

	return this_eff_load <= prev_eff_load;
}

5576 5577
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
		       int prev_cpu, int sync)
5578
{
5579
	int this_cpu = smp_processor_id();
5580
	bool affine;
5581

5582
	/*
5583 5584 5585
	 * Default to no affine wakeups; wake_affine() should not effect a task
	 * placement the load-balancer feels inclined to undo. The conservative
	 * option is therefore to not move tasks when they wake up.
5586
	 */
5587 5588 5589 5590 5591 5592 5593 5594 5595
	affine = false;

	/*
	 * If the wakeup is across cache domains, try to evaluate if movement
	 * makes sense, otherwise rely on select_idle_siblings() to do
	 * placement inside the cache domain.
	 */
	if (!cpus_share_cache(prev_cpu, this_cpu))
		affine = wake_affine_llc(sd, p, this_cpu, prev_cpu, sync);
5596

5597
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5598 5599 5600 5601
	if (affine) {
		schedstat_inc(sd->ttwu_move_affine);
		schedstat_inc(p->se.statistics.nr_wakeups_affine);
	}
5602

5603
	return affine;
5604 5605
}

5606 5607 5608 5609 5610 5611 5612 5613
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);
}

5614 5615 5616 5617 5618
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5619
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5620
		  int this_cpu, int sd_flag)
5621
{
5622
	struct sched_group *idlest = NULL, *group = sd->groups;
5623
	struct sched_group *most_spare_sg = NULL;
5624 5625
	unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0;
5626
	unsigned long most_spare = 0, this_spare = 0;
5627
	int load_idx = sd->forkexec_idx;
5628 5629 5630
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5631

5632 5633 5634
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5635
	do {
5636 5637
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5638 5639
		int local_group;
		int i;
5640

5641
		/* Skip over this group if it has no CPUs allowed */
5642
		if (!cpumask_intersects(sched_group_span(group),
5643
					&p->cpus_allowed))
5644 5645 5646
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5647
					       sched_group_span(group));
5648

5649 5650 5651 5652
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5653
		avg_load = 0;
5654
		runnable_load = 0;
5655
		max_spare_cap = 0;
5656

5657
		for_each_cpu(i, sched_group_span(group)) {
5658 5659 5660 5661 5662 5663
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5664 5665 5666
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5667 5668 5669 5670 5671

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5672 5673
		}

5674
		/* Adjust by relative CPU capacity of the group */
5675 5676 5677 5678
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5679 5680

		if (local_group) {
5681 5682
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5683 5684
			this_spare = max_spare_cap;
		} else {
5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699
			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;
5700 5701 5702 5703 5704 5705 5706
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5707 5708 5709
		}
	} while (group = group->next, group != sd->groups);

5710 5711 5712 5713 5714 5715
	/*
	 * 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.
5716 5717 5718 5719
	 *
	 * 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.
5720
	 */
5721 5722 5723
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5724
	if (this_spare > task_util(p) / 2 &&
5725
	    imbalance_scale*this_spare > 100*most_spare)
5726
		return NULL;
5727 5728

	if (most_spare > task_util(p) / 2)
5729 5730
		return most_spare_sg;

5731
skip_spare:
5732 5733 5734 5735
	if (!idlest)
		return NULL;

	if (min_runnable_load > (this_runnable_load + imbalance))
5736
		return NULL;
5737 5738 5739 5740 5741

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

5742 5743 5744 5745 5746 5747 5748 5749 5750 5751
	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;
5752 5753 5754 5755
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5756 5757
	int i;

5758 5759
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5760
		return cpumask_first(sched_group_span(group));
5761

5762
	/* Traverse only the allowed CPUs */
5763
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785
		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;
			}
5786
		} else if (shallowest_idle_cpu == -1) {
5787
			load = weighted_cpuload(cpu_rq(i));
5788 5789 5790 5791
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5792 5793 5794
		}
	}

5795
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5796
}
5797

5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826
#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
5827
void __update_idle_core(struct rq *rq)
5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856
{
	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);
5857
	int core, cpu;
5858

P
Peter Zijlstra 已提交
5859 5860 5861
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5862 5863 5864
	if (!test_idle_cores(target, false))
		return -1;

5865
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
5866

5867
	for_each_cpu_wrap(core, cpus, target) {
5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894
		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
5895 5896 5897
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5898
	for_each_cpu(cpu, cpu_smt_mask(target)) {
5899
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925
			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).
5926
 */
5927 5928
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
5929
	struct sched_domain *this_sd;
5930
	u64 avg_cost, avg_idle;
5931 5932
	u64 time, cost;
	s64 delta;
5933
	int cpu, nr = INT_MAX;
5934

5935 5936 5937 5938
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

5939 5940 5941 5942
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
5943 5944 5945 5946
	avg_idle = this_rq()->avg_idle / 512;
	avg_cost = this_sd->avg_scan_cost + 1;

	if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
5947 5948
		return -1;

5949 5950 5951 5952 5953 5954 5955 5956
	if (sched_feat(SIS_PROP)) {
		u64 span_avg = sd->span_weight * avg_idle;
		if (span_avg > 4*avg_cost)
			nr = div_u64(span_avg, avg_cost);
		else
			nr = 4;
	}

5957 5958
	time = local_clock();

5959
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
5960 5961
		if (!--nr)
			return -1;
5962
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977
			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.
5978
 */
5979
static int select_idle_sibling(struct task_struct *p, int prev, int target)
5980
{
5981
	struct sched_domain *sd;
5982
	int i;
5983

5984 5985
	if (idle_cpu(target))
		return target;
5986 5987

	/*
5988
	 * If the previous cpu is cache affine and idle, don't be stupid.
5989
	 */
5990 5991
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
5992

5993
	sd = rcu_dereference(per_cpu(sd_llc, target));
5994 5995
	if (!sd)
		return target;
5996

5997 5998 5999
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6000

6001 6002 6003 6004 6005 6006 6007
	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;
6008

6009 6010
	return target;
}
6011

6012
/*
6013
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
6014
 * tasks. The unit of the return value must be the one of capacity so we can
6015 6016
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036
 *
 * 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).
6037
 */
6038
static int cpu_util(int cpu)
6039
{
6040
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
6041 6042
	unsigned long capacity = capacity_orig_of(cpu);

6043
	return (util >= capacity) ? capacity : util;
6044
}
6045

6046 6047 6048 6049 6050
static inline int task_util(struct task_struct *p)
{
	return p->se.avg.util_avg;
}

6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068
/*
 * 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;
}

6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086
/*
 * 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;

6087 6088 6089
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6090 6091 6092
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6093
/*
6094 6095 6096
 * 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.
6097
 *
6098 6099
 * 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.
6100
 *
6101
 * Returns the target cpu number.
6102 6103 6104
 *
 * preempt must be disabled.
 */
6105
static int
6106
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6107
{
6108
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
6109
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6110
	int new_cpu = prev_cpu;
6111
	int want_affine = 0;
6112
	int sync = wake_flags & WF_SYNC;
6113

P
Peter Zijlstra 已提交
6114 6115
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6116
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6117
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6118
	}
6119

6120
	rcu_read_lock();
6121
	for_each_domain(cpu, tmp) {
6122
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6123
			break;
6124

6125
		/*
6126 6127
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
6128
		 */
6129 6130 6131
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
6132
			break;
6133
		}
6134

6135
		if (tmp->flags & sd_flag)
6136
			sd = tmp;
M
Mike Galbraith 已提交
6137 6138
		else if (!want_affine)
			break;
6139 6140
	}

M
Mike Galbraith 已提交
6141 6142
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
6143 6144 6145 6146
		if (cpu == prev_cpu)
			goto pick_cpu;

		if (wake_affine(affine_sd, p, prev_cpu, sync))
M
Mike Galbraith 已提交
6147
			new_cpu = cpu;
6148
	}
6149

M
Mike Galbraith 已提交
6150
	if (!sd) {
6151
 pick_cpu:
M
Mike Galbraith 已提交
6152
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
6153
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
6154 6155

	} else while (sd) {
6156
		struct sched_group *group;
6157
		int weight;
6158

6159
		if (!(sd->flags & sd_flag)) {
6160 6161 6162
			sd = sd->child;
			continue;
		}
6163

6164
		group = find_idlest_group(sd, p, cpu, sd_flag);
6165 6166 6167 6168
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
6169

6170
		new_cpu = find_idlest_cpu(group, p, cpu);
6171 6172 6173 6174
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
6175
		}
6176 6177 6178

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
6179
		weight = sd->span_weight;
6180 6181
		sd = NULL;
		for_each_domain(cpu, tmp) {
6182
			if (weight <= tmp->span_weight)
6183
				break;
6184
			if (tmp->flags & sd_flag)
6185 6186 6187
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
6188
	}
6189
	rcu_read_unlock();
6190

6191
	return new_cpu;
6192
}
6193 6194 6195 6196

/*
 * 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
6197
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6198
 */
6199
static void migrate_task_rq_fair(struct task_struct *p)
6200
{
6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226
	/*
	 * 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;
	}

6227
	/*
6228 6229 6230 6231 6232
	 * 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.
6233
	 */
6234 6235 6236 6237
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6238 6239

	/* We have migrated, no longer consider this task hot */
6240
	p->se.exec_start = 0;
6241
}
6242 6243 6244 6245 6246

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6247 6248
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
6249 6250
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6251 6252 6253 6254
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6255 6256
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6257 6258 6259 6260 6261 6262 6263 6264 6265
	 *
	 * 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.
6266
	 */
6267
	return calc_delta_fair(gran, se);
6268 6269
}

6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291
/*
 * 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
6292
	gran = wakeup_gran(curr, se);
6293 6294 6295 6296 6297 6298
	if (vdiff > gran)
		return 1;

	return 0;
}

6299 6300
static void set_last_buddy(struct sched_entity *se)
{
6301 6302 6303
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6304 6305 6306
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6307
		cfs_rq_of(se)->last = se;
6308
	}
6309 6310 6311 6312
}

static void set_next_buddy(struct sched_entity *se)
{
6313 6314 6315
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6316 6317 6318
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6319
		cfs_rq_of(se)->next = se;
6320
	}
6321 6322
}

6323 6324
static void set_skip_buddy(struct sched_entity *se)
{
6325 6326
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6327 6328
}

6329 6330 6331
/*
 * Preempt the current task with a newly woken task if needed:
 */
6332
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6333 6334
{
	struct task_struct *curr = rq->curr;
6335
	struct sched_entity *se = &curr->se, *pse = &p->se;
6336
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6337
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6338
	int next_buddy_marked = 0;
6339

I
Ingo Molnar 已提交
6340 6341 6342
	if (unlikely(se == pse))
		return;

6343
	/*
6344
	 * This is possible from callers such as attach_tasks(), in which we
6345 6346 6347 6348 6349 6350 6351
	 * 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;

6352
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6353
		set_next_buddy(pse);
6354 6355
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6356

6357 6358 6359
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6360 6361 6362 6363 6364 6365
	 *
	 * 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.
6366 6367 6368 6369
	 */
	if (test_tsk_need_resched(curr))
		return;

6370 6371 6372 6373 6374
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6375
	/*
6376 6377
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6378
	 */
6379
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6380
		return;
6381

6382
	find_matching_se(&se, &pse);
6383
	update_curr(cfs_rq_of(se));
6384
	BUG_ON(!pse);
6385 6386 6387 6388 6389 6390 6391
	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);
6392
		goto preempt;
6393
	}
6394

6395
	return;
6396

6397
preempt:
6398
	resched_curr(rq);
6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412
	/*
	 * 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);
6413 6414
}

6415
static struct task_struct *
6416
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6417 6418 6419
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6420
	struct task_struct *p;
6421
	int new_tasks;
6422

6423
again:
6424
	if (!cfs_rq->nr_running)
6425
		goto idle;
6426

6427
#ifdef CONFIG_FAIR_GROUP_SCHED
6428
	if (prev->sched_class != &fair_sched_class)
6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447
		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.
		 */
6448 6449 6450 6451 6452
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6453

6454 6455 6456
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6457
			 * Therefore the nr_running test will indeed
6458 6459
			 * be correct.
			 */
6460 6461 6462 6463 6464 6465
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6466
				goto simple;
6467
			}
6468
		}
6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507

		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:
#endif
6508

6509
	put_prev_task(rq, prev);
6510

6511
	do {
6512
		se = pick_next_entity(cfs_rq, NULL);
6513
		set_next_entity(cfs_rq, se);
6514 6515 6516
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6517
	p = task_of(se);
6518

6519 6520
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6521 6522

	return p;
6523 6524

idle:
6525 6526
	new_tasks = idle_balance(rq, rf);

6527 6528 6529 6530 6531
	/*
	 * 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.
	 */
6532
	if (new_tasks < 0)
6533 6534
		return RETRY_TASK;

6535
	if (new_tasks > 0)
6536 6537 6538
		goto again;

	return NULL;
6539 6540 6541 6542 6543
}

/*
 * Account for a descheduled task:
 */
6544
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6545 6546 6547 6548 6549 6550
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6551
		put_prev_entity(cfs_rq, se);
6552 6553 6554
	}
}

6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579
/*
 * 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);
6580 6581 6582 6583 6584
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6585
		rq_clock_skip_update(rq, true);
6586 6587 6588 6589 6590
	}

	set_skip_buddy(se);
}

6591 6592 6593 6594
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6595 6596
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6597 6598 6599 6600 6601 6602 6603 6604 6605 6606
		return false;

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

	yield_task_fair(rq);

	return true;
}

6607
#ifdef CONFIG_SMP
6608
/**************************************************
P
Peter Zijlstra 已提交
6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624
 * 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
6625
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6626 6627 6628 6629 6630 6631
 *
 * 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)
 *
6632
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
6633 6634 6635 6636 6637 6638
 * 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):
 *
6639
 *   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
6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677
 *
 * 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:
 *
6678
 *             log_2 n
P
Peter Zijlstra 已提交
6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723
 *   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.]
6724
 */
6725

6726 6727
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6728 6729
enum fbq_type { regular, remote, all };

6730
#define LBF_ALL_PINNED	0x01
6731
#define LBF_NEED_BREAK	0x02
6732 6733
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6734 6735 6736 6737 6738

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6739
	int			src_cpu;
6740 6741 6742 6743

	int			dst_cpu;
	struct rq		*dst_rq;

6744 6745
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6746
	enum cpu_idle_type	idle;
6747
	long			imbalance;
6748 6749 6750
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6751
	unsigned int		flags;
6752 6753 6754 6755

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6756 6757

	enum fbq_type		fbq_type;
6758
	struct list_head	tasks;
6759 6760
};

6761 6762 6763
/*
 * Is this task likely cache-hot:
 */
6764
static int task_hot(struct task_struct *p, struct lb_env *env)
6765 6766 6767
{
	s64 delta;

6768 6769
	lockdep_assert_held(&env->src_rq->lock);

6770 6771 6772 6773 6774 6775 6776 6777 6778
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
6779
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6780 6781 6782 6783 6784 6785 6786 6787 6788
			(&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;

6789
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6790 6791 6792 6793

	return delta < (s64)sysctl_sched_migration_cost;
}

6794
#ifdef CONFIG_NUMA_BALANCING
6795
/*
6796 6797 6798
 * 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.
6799
 */
6800
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6801
{
6802
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6803
	unsigned long src_faults, dst_faults;
6804 6805
	int src_nid, dst_nid;

6806
	if (!static_branch_likely(&sched_numa_balancing))
6807 6808
		return -1;

6809
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6810
		return -1;
6811 6812 6813 6814

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

6815
	if (src_nid == dst_nid)
6816
		return -1;
6817

6818 6819 6820 6821 6822 6823 6824
	/* 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;
	}
6825

6826 6827
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6828
		return 0;
6829

6830 6831 6832 6833
	/* Leaving a core idle is often worse than degrading locality. */
	if (env->idle != CPU_NOT_IDLE)
		return -1;

6834 6835 6836 6837 6838 6839
	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);
6840 6841
	}

6842
	return dst_faults < src_faults;
6843 6844
}

6845
#else
6846
static inline int migrate_degrades_locality(struct task_struct *p,
6847 6848
					     struct lb_env *env)
{
6849
	return -1;
6850
}
6851 6852
#endif

6853 6854 6855 6856
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6857
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6858
{
6859
	int tsk_cache_hot;
6860 6861 6862

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

6863 6864
	/*
	 * We do not migrate tasks that are:
6865
	 * 1) throttled_lb_pair, or
6866
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6867 6868
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6869
	 */
6870 6871 6872
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6873
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
6874
		int cpu;
6875

6876
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
6877

6878 6879
		env->flags |= LBF_SOME_PINNED;

6880 6881 6882 6883 6884
		/*
		 * 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.
		 *
6885 6886
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
6887
		 */
6888
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
6889 6890
			return 0;

6891 6892
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6893
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
6894
				env->flags |= LBF_DST_PINNED;
6895 6896 6897
				env->new_dst_cpu = cpu;
				break;
			}
6898
		}
6899

6900 6901
		return 0;
	}
6902 6903

	/* Record that we found atleast one task that could run on dst_cpu */
6904
	env->flags &= ~LBF_ALL_PINNED;
6905

6906
	if (task_running(env->src_rq, p)) {
6907
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
6908 6909 6910 6911 6912
		return 0;
	}

	/*
	 * Aggressive migration if:
6913 6914 6915
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6916
	 */
6917 6918 6919
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6920

6921
	if (tsk_cache_hot <= 0 ||
6922
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6923
		if (tsk_cache_hot == 1) {
6924 6925
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
6926
		}
6927 6928 6929
		return 1;
	}

6930
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
6931
	return 0;
6932 6933
}

6934
/*
6935 6936 6937 6938 6939 6940 6941
 * 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;
6942
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
6943 6944 6945
	set_task_cpu(p, env->dst_cpu);
}

6946
/*
6947
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6948 6949
 * part of active balancing operations within "domain".
 *
6950
 * Returns a task if successful and NULL otherwise.
6951
 */
6952
static struct task_struct *detach_one_task(struct lb_env *env)
6953 6954 6955
{
	struct task_struct *p, *n;

6956 6957
	lockdep_assert_held(&env->src_rq->lock);

6958 6959 6960
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6961

6962
		detach_task(p, env);
6963

6964
		/*
6965
		 * Right now, this is only the second place where
6966
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6967
		 * so we can safely collect stats here rather than
6968
		 * inside detach_tasks().
6969
		 */
6970
		schedstat_inc(env->sd->lb_gained[env->idle]);
6971
		return p;
6972
	}
6973
	return NULL;
6974 6975
}

6976 6977
static const unsigned int sched_nr_migrate_break = 32;

6978
/*
6979 6980
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6981
 *
6982
 * Returns number of detached tasks if successful and 0 otherwise.
6983
 */
6984
static int detach_tasks(struct lb_env *env)
6985
{
6986 6987
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6988
	unsigned long load;
6989 6990 6991
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6992

6993
	if (env->imbalance <= 0)
6994
		return 0;
6995

6996
	while (!list_empty(tasks)) {
6997 6998 6999 7000 7001 7002 7003
		/*
		 * 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;

7004
		p = list_first_entry(tasks, struct task_struct, se.group_node);
7005

7006 7007
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7008
		if (env->loop > env->loop_max)
7009
			break;
7010 7011

		/* take a breather every nr_migrate tasks */
7012
		if (env->loop > env->loop_break) {
7013
			env->loop_break += sched_nr_migrate_break;
7014
			env->flags |= LBF_NEED_BREAK;
7015
			break;
7016
		}
7017

7018
		if (!can_migrate_task(p, env))
7019 7020 7021
			goto next;

		load = task_h_load(p);
7022

7023
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7024 7025
			goto next;

7026
		if ((load / 2) > env->imbalance)
7027
			goto next;
7028

7029 7030 7031 7032
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7033
		env->imbalance -= load;
7034 7035

#ifdef CONFIG_PREEMPT
7036 7037
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7038
		 * kernels will stop after the first task is detached to minimize
7039 7040
		 * the critical section.
		 */
7041
		if (env->idle == CPU_NEWLY_IDLE)
7042
			break;
7043 7044
#endif

7045 7046 7047 7048
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7049
		if (env->imbalance <= 0)
7050
			break;
7051 7052 7053

		continue;
next:
7054
		list_move_tail(&p->se.group_node, tasks);
7055
	}
7056

7057
	/*
7058 7059 7060
	 * 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().
7061
	 */
7062
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7063

7064 7065 7066 7067 7068 7069 7070 7071 7072 7073 7074
	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);
7075
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7076
	p->on_rq = TASK_ON_RQ_QUEUED;
7077 7078 7079 7080 7081 7082 7083 7084 7085
	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)
{
7086 7087 7088
	struct rq_flags rf;

	rq_lock(rq, &rf);
7089
	update_rq_clock(rq);
7090
	attach_task(rq, p);
7091
	rq_unlock(rq, &rf);
7092 7093 7094 7095 7096 7097 7098 7099 7100 7101
}

/*
 * 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;
7102
	struct rq_flags rf;
7103

7104
	rq_lock(env->dst_rq, &rf);
7105
	update_rq_clock(env->dst_rq);
7106 7107 7108 7109

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7110

7111 7112 7113
		attach_task(env->dst_rq, p);
	}

7114
	rq_unlock(env->dst_rq, &rf);
7115 7116
}

P
Peter Zijlstra 已提交
7117
#ifdef CONFIG_FAIR_GROUP_SCHED
7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135

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;
}

7136
static void update_blocked_averages(int cpu)
7137 7138
{
	struct rq *rq = cpu_rq(cpu);
7139
	struct cfs_rq *cfs_rq, *pos;
7140
	struct rq_flags rf;
7141

7142
	rq_lock_irqsave(rq, &rf);
7143
	update_rq_clock(rq);
7144

7145 7146 7147 7148
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7149
	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7150 7151
		struct sched_entity *se;

7152 7153 7154
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7155

7156
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7157
			update_tg_load_avg(cfs_rq, 0);
7158

7159 7160 7161
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7162
			update_load_avg(cfs_rq_of(se), se, 0);
7163 7164 7165 7166 7167 7168 7169

		/*
		 * 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);
7170
	}
7171
	rq_unlock_irqrestore(rq, &rf);
7172 7173
}

7174
/*
7175
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7176 7177 7178
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7179
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7180
{
7181 7182
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7183
	unsigned long now = jiffies;
7184
	unsigned long load;
7185

7186
	if (cfs_rq->last_h_load_update == now)
7187 7188
		return;

7189 7190 7191 7192 7193 7194 7195
	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;
	}
7196

7197
	if (!se) {
7198
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7199 7200 7201 7202 7203
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
7204 7205
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7206 7207 7208 7209
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7210 7211
}

7212
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7213
{
7214
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7215

7216
	update_cfs_rq_h_load(cfs_rq);
7217
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7218
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7219 7220
}
#else
7221
static inline void update_blocked_averages(int cpu)
7222
{
7223 7224
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7225
	struct rq_flags rf;
7226

7227
	rq_lock_irqsave(rq, &rf);
7228
	update_rq_clock(rq);
7229
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7230
	rq_unlock_irqrestore(rq, &rf);
7231 7232
}

7233
static unsigned long task_h_load(struct task_struct *p)
7234
{
7235
	return p->se.avg.load_avg;
7236
}
P
Peter Zijlstra 已提交
7237
#endif
7238 7239

/********** Helpers for find_busiest_group ************************/
7240 7241 7242 7243 7244 7245 7246

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

7247 7248 7249 7250 7251 7252 7253
/*
 * 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
7254
	unsigned long load_per_task;
7255
	unsigned long group_capacity;
7256
	unsigned long group_util; /* Total utilization of the group */
7257 7258 7259
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7260
	enum group_type group_type;
7261
	int group_no_capacity;
7262 7263 7264 7265
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7266 7267
};

J
Joonsoo Kim 已提交
7268 7269 7270 7271 7272 7273 7274
/*
 * 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 */
7275
	unsigned long total_running;
J
Joonsoo Kim 已提交
7276
	unsigned long total_load;	/* Total load of all groups in sd */
7277
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7278 7279 7280
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7281
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7282 7283
};

7284 7285 7286 7287 7288 7289 7290 7291 7292 7293 7294
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,
7295
		.total_running = 0UL,
7296
		.total_load = 0UL,
7297
		.total_capacity = 0UL,
7298 7299
		.busiest_stat = {
			.avg_load = 0UL,
7300 7301
			.sum_nr_running = 0,
			.group_type = group_other,
7302 7303 7304 7305
		},
	};
}

7306 7307 7308
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7309
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7310 7311
 *
 * Return: The load index.
7312 7313 7314 7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332 7333
 */
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;
}

7334
static unsigned long scale_rt_capacity(int cpu)
7335 7336
{
	struct rq *rq = cpu_rq(cpu);
7337
	u64 total, used, age_stamp, avg;
7338
	s64 delta;
7339

7340 7341 7342 7343
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
7344 7345
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
7346
	delta = __rq_clock_broken(rq) - age_stamp;
7347

7348 7349 7350 7351
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
7352

7353
	used = div_u64(avg, total);
7354

7355 7356
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
7357

7358
	return 1;
7359 7360
}

7361
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7362
{
7363
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7364 7365
	struct sched_group *sdg = sd->groups;

7366
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7367

7368
	capacity *= scale_rt_capacity(cpu);
7369
	capacity >>= SCHED_CAPACITY_SHIFT;
7370

7371 7372
	if (!capacity)
		capacity = 1;
7373

7374 7375
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7376
	sdg->sgc->min_capacity = capacity;
7377 7378
}

7379
void update_group_capacity(struct sched_domain *sd, int cpu)
7380 7381 7382
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7383
	unsigned long capacity, min_capacity;
7384 7385 7386 7387
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7388
	sdg->sgc->next_update = jiffies + interval;
7389 7390

	if (!child) {
7391
		update_cpu_capacity(sd, cpu);
7392 7393 7394
		return;
	}

7395
	capacity = 0;
7396
	min_capacity = ULONG_MAX;
7397

P
Peter Zijlstra 已提交
7398 7399 7400 7401 7402 7403
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7404
		for_each_cpu(cpu, sched_group_span(sdg)) {
7405
			struct sched_group_capacity *sgc;
7406
			struct rq *rq = cpu_rq(cpu);
7407

7408
			/*
7409
			 * build_sched_domains() -> init_sched_groups_capacity()
7410 7411 7412
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7413 7414
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7415
			 *
7416
			 * This avoids capacity from being 0 and
7417 7418 7419
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7420
				capacity += capacity_of(cpu);
7421 7422 7423
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7424
			}
7425

7426
			min_capacity = min(capacity, min_capacity);
7427
		}
P
Peter Zijlstra 已提交
7428 7429 7430 7431
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7432
		 */
P
Peter Zijlstra 已提交
7433 7434 7435

		group = child->groups;
		do {
7436 7437 7438 7439
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7440 7441 7442
			group = group->next;
		} while (group != child->groups);
	}
7443

7444
	sdg->sgc->capacity = capacity;
7445
	sdg->sgc->min_capacity = min_capacity;
7446 7447
}

7448
/*
7449 7450 7451
 * 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
7452 7453
 */
static inline int
7454
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7455
{
7456 7457
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7458 7459
}

7460 7461
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7462
 * groups is inadequate due to ->cpus_allowed constraints.
7463 7464 7465 7466 7467
 *
 * 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:
 *
7468 7469
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7470 7471 7472 7473 7474 7475
 *
 * 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
7476 7477
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7478 7479
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7480
 * update_sd_pick_busiest(). And calculate_imbalance() and
7481
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7482 7483 7484 7485 7486 7487 7488
 * 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.
 */

7489
static inline int sg_imbalanced(struct sched_group *group)
7490
{
7491
	return group->sgc->imbalance;
7492 7493
}

7494
/*
7495 7496 7497
 * 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
7498 7499
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7500 7501 7502 7503 7504
 * 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.
7505
 */
7506 7507
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7508
{
7509 7510
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7511

7512
	if ((sgs->group_capacity * 100) >
7513
			(sgs->group_util * env->sd->imbalance_pct))
7514
		return true;
7515

7516 7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531
	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;
7532

7533
	if ((sgs->group_capacity * 100) <
7534
			(sgs->group_util * env->sd->imbalance_pct))
7535
		return true;
7536

7537
	return false;
7538 7539
}

7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550
/*
 * 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;
}

7551 7552 7553
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7554
{
7555
	if (sgs->group_no_capacity)
7556 7557 7558 7559 7560 7561 7562 7563
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7564 7565
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7566
 * @env: The load balancing environment.
7567 7568 7569 7570
 * @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.
7571
 * @overload: Indicate more than one runnable task for any CPU.
7572
 */
7573 7574
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7575 7576
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7577
{
7578
	unsigned long load;
7579
	int i, nr_running;
7580

7581 7582
	memset(sgs, 0, sizeof(*sgs));

7583
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7584 7585 7586
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
7587
		if (local_group)
7588
			load = target_load(i, load_idx);
7589
		else
7590 7591 7592
			load = source_load(i, load_idx);

		sgs->group_load += load;
7593
		sgs->group_util += cpu_util(i);
7594
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7595

7596 7597
		nr_running = rq->nr_running;
		if (nr_running > 1)
7598 7599
			*overload = true;

7600 7601 7602 7603
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7604
		sgs->sum_weighted_load += weighted_cpuload(rq);
7605 7606 7607 7608
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7609
			sgs->idle_cpus++;
7610 7611
	}

7612 7613
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7614
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7615

7616
	if (sgs->sum_nr_running)
7617
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7618

7619
	sgs->group_weight = group->group_weight;
7620

7621
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7622
	sgs->group_type = group_classify(group, sgs);
7623 7624
}

7625 7626
/**
 * update_sd_pick_busiest - return 1 on busiest group
7627
 * @env: The load balancing environment.
7628 7629
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7630
 * @sgs: sched_group statistics
7631 7632 7633
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7634 7635 7636
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7637
 */
7638
static bool update_sd_pick_busiest(struct lb_env *env,
7639 7640
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7641
				   struct sg_lb_stats *sgs)
7642
{
7643
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7644

7645
	if (sgs->group_type > busiest->group_type)
7646 7647
		return true;

7648 7649 7650 7651 7652 7653
	if (sgs->group_type < busiest->group_type)
		return false;

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

7654 7655 7656 7657 7658 7659 7660 7661 7662 7663 7664 7665 7666 7667
	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:
7668 7669
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7670 7671
		return true;

7672 7673 7674
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
7675
	/*
T
Tim Chen 已提交
7676 7677 7678
	 * 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.
7679
	 */
T
Tim Chen 已提交
7680 7681
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7682 7683 7684
		if (!sds->busiest)
			return true;

T
Tim Chen 已提交
7685 7686 7687
		/* Prefer to move from lowest priority cpu's work */
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7688 7689 7690 7691 7692 7693
			return true;
	}

	return false;
}

7694 7695 7696 7697 7698 7699 7700 7701 7702 7703 7704 7705 7706 7707 7708 7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719 7720 7721 7722 7723
#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 */

7724
/**
7725
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7726
 * @env: The load balancing environment.
7727 7728
 * @sds: variable to hold the statistics for this sched_domain.
 */
7729
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7730
{
7731
	struct sched_domain_shared *shared = env->sd->shared;
7732 7733
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7734
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7735
	struct sg_lb_stats tmp_sgs;
7736
	int load_idx, prefer_sibling = 0;
7737
	bool overload = false;
7738 7739 7740 7741

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

7742
	load_idx = get_sd_load_idx(env->sd, env->idle);
7743 7744

	do {
J
Joonsoo Kim 已提交
7745
		struct sg_lb_stats *sgs = &tmp_sgs;
7746 7747
		int local_group;

7748
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7749 7750
		if (local_group) {
			sds->local = sg;
7751
			sgs = local;
7752 7753

			if (env->idle != CPU_NEWLY_IDLE ||
7754 7755
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7756
		}
7757

7758 7759
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7760

7761 7762 7763
		if (local_group)
			goto next_group;

7764 7765
		/*
		 * In case the child domain prefers tasks go to siblings
7766
		 * first, lower the sg capacity so that we'll try
7767 7768
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7769 7770 7771 7772
		 * 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).
7773
		 */
7774
		if (prefer_sibling && sds->local &&
7775 7776
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7777
			sgs->group_no_capacity = 1;
7778
			sgs->group_type = group_classify(sg, sgs);
7779
		}
7780

7781
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7782
			sds->busiest = sg;
J
Joonsoo Kim 已提交
7783
			sds->busiest_stat = *sgs;
7784 7785
		}

7786 7787
next_group:
		/* Now, start updating sd_lb_stats */
7788
		sds->total_running += sgs->sum_nr_running;
7789
		sds->total_load += sgs->group_load;
7790
		sds->total_capacity += sgs->group_capacity;
7791

7792
		sg = sg->next;
7793
	} while (sg != env->sd->groups);
7794 7795 7796

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7797 7798 7799 7800 7801 7802 7803

	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;
	}

7804 7805 7806 7807 7808 7809 7810 7811 7812 7813 7814 7815 7816 7817 7818
	if (!shared)
		return;

	/*
	 * Since these are sums over groups they can contain some CPUs
	 * multiple times for the NUMA domains.
	 *
	 * Currently only wake_affine_llc() and find_busiest_group()
	 * uses these numbers, only the last is affected by this problem.
	 *
	 * XXX fix that.
	 */
	WRITE_ONCE(shared->nr_running,	sds->total_running);
	WRITE_ONCE(shared->load,	sds->total_load);
	WRITE_ONCE(shared->capacity,	sds->total_capacity);
7819 7820 7821 7822
}

/**
 * check_asym_packing - Check to see if the group is packed into the
7823
 *			sched domain.
7824 7825 7826 7827 7828 7829 7830 7831 7832 7833 7834 7835 7836 7837
 *
 * 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.
 *
7838
 * Return: 1 when packing is required and a task should be moved to
7839
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
7840
 *
7841
 * @env: The load balancing environment.
7842 7843
 * @sds: Statistics of the sched_domain which is to be packed
 */
7844
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7845 7846 7847
{
	int busiest_cpu;

7848
	if (!(env->sd->flags & SD_ASYM_PACKING))
7849 7850
		return 0;

7851 7852 7853
	if (env->idle == CPU_NOT_IDLE)
		return 0;

7854 7855 7856
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
7857 7858
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
7859 7860
		return 0;

7861
	env->imbalance = DIV_ROUND_CLOSEST(
7862
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7863
		SCHED_CAPACITY_SCALE);
7864

7865
	return 1;
7866 7867 7868 7869 7870 7871
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
7872
 * @env: The load balancing environment.
7873 7874
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
7875 7876
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7877
{
7878
	unsigned long tmp, capa_now = 0, capa_move = 0;
7879
	unsigned int imbn = 2;
7880
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
7881
	struct sg_lb_stats *local, *busiest;
7882

J
Joonsoo Kim 已提交
7883 7884
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7885

J
Joonsoo Kim 已提交
7886 7887 7888 7889
	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;
7890

J
Joonsoo Kim 已提交
7891
	scaled_busy_load_per_task =
7892
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7893
		busiest->group_capacity;
J
Joonsoo Kim 已提交
7894

7895 7896
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
7897
		env->imbalance = busiest->load_per_task;
7898 7899 7900 7901 7902
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
7903
	 * however we may be able to increase total CPU capacity used by
7904 7905 7906
	 * moving them.
	 */

7907
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
7908
			min(busiest->load_per_task, busiest->avg_load);
7909
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
7910
			min(local->load_per_task, local->avg_load);
7911
	capa_now /= SCHED_CAPACITY_SCALE;
7912 7913

	/* Amount of load we'd subtract */
7914
	if (busiest->avg_load > scaled_busy_load_per_task) {
7915
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
7916
			    min(busiest->load_per_task,
7917
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
7918
	}
7919 7920

	/* Amount of load we'd add */
7921
	if (busiest->avg_load * busiest->group_capacity <
7922
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7923 7924
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
7925
	} else {
7926
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7927
		      local->group_capacity;
J
Joonsoo Kim 已提交
7928
	}
7929
	capa_move += local->group_capacity *
7930
		    min(local->load_per_task, local->avg_load + tmp);
7931
	capa_move /= SCHED_CAPACITY_SCALE;
7932 7933

	/* Move if we gain throughput */
7934
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
7935
		env->imbalance = busiest->load_per_task;
7936 7937 7938 7939 7940
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
7941
 * @env: load balance environment
7942 7943
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
7944
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7945
{
7946
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
7947 7948 7949 7950
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7951

7952
	if (busiest->group_type == group_imbalanced) {
7953 7954 7955 7956
		/*
		 * 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
7957 7958
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
7959 7960
	}

7961
	/*
7962 7963 7964 7965
	 * 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:
7966
	 */
7967 7968
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7969 7970
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7971 7972
	}

7973 7974 7975 7976 7977
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7978
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7979
		if (load_above_capacity > busiest->group_capacity) {
7980
			load_above_capacity -= busiest->group_capacity;
7981
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
7982 7983
			load_above_capacity /= busiest->group_capacity;
		} else
7984
			load_above_capacity = ~0UL;
7985 7986 7987 7988 7989 7990
	}

	/*
	 * 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,
7991 7992
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
7993
	 */
7994
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7995 7996

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7997
	env->imbalance = min(
7998 7999
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8000
	) / SCHED_CAPACITY_SCALE;
8001 8002 8003

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8004
	 * there is no guarantee that any tasks will be moved so we'll have
8005 8006 8007
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8008
	if (env->imbalance < busiest->load_per_task)
8009
		return fix_small_imbalance(env, sds);
8010
}
8011

8012 8013 8014 8015
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8016
 * if there is an imbalance.
8017 8018 8019 8020
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8021
 * @env: The load balancing environment.
8022
 *
8023
 * Return:	- The busiest group if imbalance exists.
8024
 */
J
Joonsoo Kim 已提交
8025
static struct sched_group *find_busiest_group(struct lb_env *env)
8026
{
J
Joonsoo Kim 已提交
8027
	struct sg_lb_stats *local, *busiest;
8028 8029
	struct sd_lb_stats sds;

8030
	init_sd_lb_stats(&sds);
8031 8032 8033 8034 8035

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8036
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8037 8038
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8039

8040
	/* ASYM feature bypasses nice load balance check */
8041
	if (check_asym_packing(env, &sds))
8042 8043
		return sds.busiest;

8044
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8045
	if (!sds.busiest || busiest->sum_nr_running == 0)
8046 8047
		goto out_balanced;

8048
	/* XXX broken for overlapping NUMA groups */
8049 8050
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8051

P
Peter Zijlstra 已提交
8052 8053
	/*
	 * If the busiest group is imbalanced the below checks don't
8054
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8055 8056
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8057
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8058 8059
		goto force_balance;

8060
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
8061 8062
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
8063 8064
		goto force_balance;

8065
	/*
8066
	 * If the local group is busier than the selected busiest group
8067 8068
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8069
	if (local->avg_load >= busiest->avg_load)
8070 8071
		goto out_balanced;

8072 8073 8074 8075
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8076
	if (local->avg_load >= sds.avg_load)
8077 8078
		goto out_balanced;

8079
	if (env->idle == CPU_IDLE) {
8080
		/*
8081 8082 8083 8084 8085
		 * 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
8086
		 */
8087 8088
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8089
			goto out_balanced;
8090 8091 8092 8093 8094
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8095 8096
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8097
			goto out_balanced;
8098
	}
8099

8100
force_balance:
8101
	/* Looks like there is an imbalance. Compute it */
8102
	calculate_imbalance(env, &sds);
8103 8104 8105
	return sds.busiest;

out_balanced:
8106
	env->imbalance = 0;
8107 8108 8109 8110 8111 8112
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
8113
static struct rq *find_busiest_queue(struct lb_env *env,
8114
				     struct sched_group *group)
8115 8116
{
	struct rq *busiest = NULL, *rq;
8117
	unsigned long busiest_load = 0, busiest_capacity = 1;
8118 8119
	int i;

8120
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8121
		unsigned long capacity, wl;
8122 8123 8124 8125
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8126

8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143 8144 8145 8146 8147 8148
		/*
		 * 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;

8149
		capacity = capacity_of(i);
8150

8151
		wl = weighted_cpuload(rq);
8152

8153 8154
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8155
		 * which is not scaled with the cpu capacity.
8156
		 */
8157 8158 8159

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8160 8161
			continue;

8162 8163
		/*
		 * For the load comparisons with the other cpu's, consider
8164 8165 8166
		 * 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.
8167
		 *
8168
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8169
		 * multiplication to rid ourselves of the division works out
8170 8171
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8172
		 */
8173
		if (wl * busiest_capacity > busiest_load * capacity) {
8174
			busiest_load = wl;
8175
			busiest_capacity = capacity;
8176 8177 8178 8179 8180 8181 8182 8183 8184 8185 8186 8187 8188
			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

8189
static int need_active_balance(struct lb_env *env)
8190
{
8191 8192 8193
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8194 8195 8196

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8197 8198
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8199
		 */
T
Tim Chen 已提交
8200 8201
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8202
			return 1;
8203 8204
	}

8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217
	/*
	 * 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;
	}

8218 8219 8220
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8221 8222
static int active_load_balance_cpu_stop(void *data);

8223 8224 8225 8226 8227 8228 8229 8230 8231 8232 8233 8234 8235
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 */
8236
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8237
		if (!idle_cpu(cpu))
8238 8239 8240 8241 8242 8243 8244 8245 8246 8247 8248 8249 8250
			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.
	 */
8251
	return balance_cpu == env->dst_cpu;
8252 8253
}

8254 8255 8256 8257 8258 8259
/*
 * 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,
8260
			int *continue_balancing)
8261
{
8262
	int ld_moved, cur_ld_moved, active_balance = 0;
8263
	struct sched_domain *sd_parent = sd->parent;
8264 8265
	struct sched_group *group;
	struct rq *busiest;
8266
	struct rq_flags rf;
8267
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8268

8269 8270
	struct lb_env env = {
		.sd		= sd,
8271 8272
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8273
		.dst_grpmask    = sched_group_span(sd->groups),
8274
		.idle		= idle,
8275
		.loop_break	= sched_nr_migrate_break,
8276
		.cpus		= cpus,
8277
		.fbq_type	= all,
8278
		.tasks		= LIST_HEAD_INIT(env.tasks),
8279 8280
	};

8281
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8282

8283
	schedstat_inc(sd->lb_count[idle]);
8284 8285

redo:
8286 8287
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8288
		goto out_balanced;
8289
	}
8290

8291
	group = find_busiest_group(&env);
8292
	if (!group) {
8293
		schedstat_inc(sd->lb_nobusyg[idle]);
8294 8295 8296
		goto out_balanced;
	}

8297
	busiest = find_busiest_queue(&env, group);
8298
	if (!busiest) {
8299
		schedstat_inc(sd->lb_nobusyq[idle]);
8300 8301 8302
		goto out_balanced;
	}

8303
	BUG_ON(busiest == env.dst_rq);
8304

8305
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8306

8307 8308 8309
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8310 8311 8312 8313 8314 8315 8316 8317
	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.
		 */
8318
		env.flags |= LBF_ALL_PINNED;
8319
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8320

8321
more_balance:
8322
		rq_lock_irqsave(busiest, &rf);
8323
		update_rq_clock(busiest);
8324 8325 8326 8327 8328

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8329
		cur_ld_moved = detach_tasks(&env);
8330 8331

		/*
8332 8333 8334 8335 8336
		 * 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.
8337
		 */
8338

8339
		rq_unlock(busiest, &rf);
8340 8341 8342 8343 8344 8345

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8346
		local_irq_restore(rf.flags);
8347

8348 8349 8350 8351 8352
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8353 8354 8355 8356 8357 8358 8359 8360 8361 8362 8363 8364 8365 8366 8367 8368 8369 8370 8371
		/*
		 * 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.
		 */
8372
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8373

8374 8375 8376
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8377
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8378
			env.dst_cpu	 = env.new_dst_cpu;
8379
			env.flags	&= ~LBF_DST_PINNED;
8380 8381
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8382

8383 8384 8385 8386 8387 8388
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8389

8390 8391 8392 8393
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8394
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8395

8396
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8397 8398 8399
				*group_imbalance = 1;
		}

8400
		/* All tasks on this runqueue were pinned by CPU affinity */
8401
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8402
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8403 8404 8405 8406 8407 8408 8409 8410 8411
			/*
			 * Attempting to continue load balancing at the current
			 * sched_domain level only makes sense if there are
			 * active CPUs remaining as possible busiest CPUs to
			 * pull load from which are not contained within the
			 * destination group that is receiving any migrated
			 * load.
			 */
			if (!cpumask_subset(cpus, env.dst_grpmask)) {
8412 8413
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8414
				goto redo;
8415
			}
8416
			goto out_all_pinned;
8417 8418 8419 8420
		}
	}

	if (!ld_moved) {
8421
		schedstat_inc(sd->lb_failed[idle]);
8422 8423 8424 8425 8426 8427 8428 8429
		/*
		 * 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++;
8430

8431
		if (need_active_balance(&env)) {
8432 8433
			unsigned long flags;

8434 8435
			raw_spin_lock_irqsave(&busiest->lock, flags);

8436 8437 8438
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
8439
			 */
8440
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8441 8442
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8443
				env.flags |= LBF_ALL_PINNED;
8444 8445 8446
				goto out_one_pinned;
			}

8447 8448 8449 8450 8451
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8452 8453 8454 8455 8456 8457
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8458

8459
			if (active_balance) {
8460 8461 8462
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8463
			}
8464

8465
			/* We've kicked active balancing, force task migration. */
8466 8467 8468 8469 8470 8471 8472 8473 8474 8475 8476 8477 8478
			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
8479
		 * detach_tasks).
8480 8481 8482 8483 8484 8485 8486 8487
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8488 8489 8490 8491 8492 8493 8494 8495 8496 8497 8498 8499 8500 8501 8502 8503 8504
	/*
	 * 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.
	 */
8505
	schedstat_inc(sd->lb_balanced[idle]);
8506 8507 8508 8509 8510

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8511
	if (((env.flags & LBF_ALL_PINNED) &&
8512
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8513 8514 8515
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8516
	ld_moved = 0;
8517 8518 8519 8520
out:
	return ld_moved;
}

8521 8522 8523 8524 8525 8526 8527 8528 8529 8530 8531 8532 8533 8534 8535 8536
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
8537
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8538 8539 8540
{
	unsigned long interval, next;

8541 8542
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8543 8544 8545 8546 8547 8548
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8549 8550 8551 8552
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
8553
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
8554
{
8555 8556
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
8557 8558
	struct sched_domain *sd;
	int pulled_task = 0;
8559
	u64 curr_cost = 0;
8560

8561 8562 8563 8564 8565 8566
	/*
	 * 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);

8567 8568 8569 8570 8571 8572
	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

8573 8574 8575 8576 8577 8578 8579 8580
	/*
	 * 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);

8581 8582
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
8583 8584 8585
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
8586
			update_next_balance(sd, &next_balance);
8587 8588
		rcu_read_unlock();

8589
		goto out;
8590
	}
8591

8592 8593
	raw_spin_unlock(&this_rq->lock);

8594
	update_blocked_averages(this_cpu);
8595
	rcu_read_lock();
8596
	for_each_domain(this_cpu, sd) {
8597
		int continue_balancing = 1;
8598
		u64 t0, domain_cost;
8599 8600 8601 8602

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8603
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8604
			update_next_balance(sd, &next_balance);
8605
			break;
8606
		}
8607

8608
		if (sd->flags & SD_BALANCE_NEWIDLE) {
8609 8610
			t0 = sched_clock_cpu(this_cpu);

8611
			pulled_task = load_balance(this_cpu, this_rq,
8612 8613
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
8614 8615 8616 8617 8618 8619

			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;
8620
		}
8621

8622
		update_next_balance(sd, &next_balance);
8623 8624 8625 8626 8627 8628

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
8629 8630
			break;
	}
8631
	rcu_read_unlock();
8632 8633 8634

	raw_spin_lock(&this_rq->lock);

8635 8636 8637
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

8638
	/*
8639 8640 8641
	 * 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.
8642
	 */
8643
	if (this_rq->cfs.h_nr_running && !pulled_task)
8644
		pulled_task = 1;
8645

8646 8647 8648
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
8649
		this_rq->next_balance = next_balance;
8650

8651
	/* Is there a task of a high priority class? */
8652
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8653 8654
		pulled_task = -1;

8655
	if (pulled_task)
8656 8657
		this_rq->idle_stamp = 0;

8658 8659
	rq_repin_lock(this_rq, rf);

8660
	return pulled_task;
8661 8662 8663
}

/*
8664 8665 8666 8667
 * 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.
8668
 */
8669
static int active_load_balance_cpu_stop(void *data)
8670
{
8671 8672
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8673
	int target_cpu = busiest_rq->push_cpu;
8674
	struct rq *target_rq = cpu_rq(target_cpu);
8675
	struct sched_domain *sd;
8676
	struct task_struct *p = NULL;
8677
	struct rq_flags rf;
8678

8679
	rq_lock_irq(busiest_rq, &rf);
8680 8681 8682 8683 8684 8685 8686
	/*
	 * Between queueing the stop-work and running it is a hole in which
	 * CPUs can become inactive. We should not move tasks from or to
	 * inactive CPUs.
	 */
	if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
		goto out_unlock;
8687 8688 8689 8690 8691

	/* 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;
8692 8693 8694

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8695
		goto out_unlock;
8696 8697 8698 8699 8700 8701 8702 8703 8704

	/*
	 * 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. */
8705
	rcu_read_lock();
8706 8707 8708 8709 8710 8711 8712
	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)) {
8713 8714
		struct lb_env env = {
			.sd		= sd,
8715 8716 8717 8718
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8719
			.idle		= CPU_IDLE,
8720 8721 8722 8723 8724 8725 8726
			/*
			 * can_migrate_task() doesn't need to compute new_dst_cpu
			 * for active balancing. Since we have CPU_IDLE, but no
			 * @dst_grpmask we need to make that test go away with lying
			 * about DST_PINNED.
			 */
			.flags		= LBF_DST_PINNED,
8727 8728
		};

8729
		schedstat_inc(sd->alb_count);
8730
		update_rq_clock(busiest_rq);
8731

8732
		p = detach_one_task(&env);
8733
		if (p) {
8734
			schedstat_inc(sd->alb_pushed);
8735 8736 8737
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8738
			schedstat_inc(sd->alb_failed);
8739
		}
8740
	}
8741
	rcu_read_unlock();
8742 8743
out_unlock:
	busiest_rq->active_balance = 0;
8744
	rq_unlock(busiest_rq, &rf);
8745 8746 8747 8748 8749 8750

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8751
	return 0;
8752 8753
}

8754 8755 8756 8757 8758
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8759
#ifdef CONFIG_NO_HZ_COMMON
8760 8761 8762 8763 8764 8765
/*
 * 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.
 */
8766
static struct {
8767
	cpumask_var_t idle_cpus_mask;
8768
	atomic_t nr_cpus;
8769 8770
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
8771

8772
static inline int find_new_ilb(void)
8773
{
8774
	int ilb = cpumask_first(nohz.idle_cpus_mask);
8775

8776 8777 8778 8779
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
8780 8781
}

8782 8783 8784 8785 8786
/*
 * 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).
 */
8787
static void nohz_balancer_kick(void)
8788 8789 8790 8791 8792
{
	int ilb_cpu;

	nohz.next_balance++;

8793
	ilb_cpu = find_new_ilb();
8794

8795 8796
	if (ilb_cpu >= nr_cpu_ids)
		return;
8797

8798
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8799 8800 8801 8802 8803 8804 8805 8806
		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);
8807 8808 8809
	return;
}

8810
void nohz_balance_exit_idle(unsigned int cpu)
8811 8812
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8813 8814 8815 8816 8817 8818 8819
		/*
		 * 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);
		}
8820 8821 8822 8823
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

8824 8825 8826
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
8827
	int cpu = smp_processor_id();
8828 8829

	rcu_read_lock();
8830
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8831 8832 8833 8834 8835

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

8836
	atomic_inc(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8837
unlock:
8838 8839 8840 8841 8842 8843
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
8844
	int cpu = smp_processor_id();
8845 8846

	rcu_read_lock();
8847
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8848 8849 8850 8851 8852

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

8853
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8854
unlock:
8855 8856 8857
	rcu_read_unlock();
}

8858
/*
8859
 * This routine will record that the cpu is going idle with tick stopped.
8860
 * This info will be used in performing idle load balancing in the future.
8861
 */
8862
void nohz_balance_enter_idle(int cpu)
8863
{
8864 8865 8866 8867 8868 8869
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

8870 8871 8872 8873
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
	if (!is_housekeeping_cpu(cpu))
		return;

8874 8875
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
8876

8877 8878 8879 8880 8881 8882
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

8883 8884 8885
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8886 8887 8888 8889 8890
}
#endif

static DEFINE_SPINLOCK(balancing);

8891 8892 8893 8894
/*
 * 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.
 */
8895
void update_max_interval(void)
8896 8897 8898 8899
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

8900 8901 8902 8903
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
8904
 * Balancing parameters are set up in init_sched_domains.
8905
 */
8906
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8907
{
8908
	int continue_balancing = 1;
8909
	int cpu = rq->cpu;
8910
	unsigned long interval;
8911
	struct sched_domain *sd;
8912 8913 8914
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8915 8916
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
8917

8918
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
8919

8920
	rcu_read_lock();
8921
	for_each_domain(cpu, sd) {
8922 8923 8924 8925 8926 8927 8928 8929 8930 8931 8932 8933
		/*
		 * 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;

8934 8935 8936
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8937 8938 8939 8940 8941 8942 8943 8944 8945 8946 8947
		/*
		 * 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;
		}

8948
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8949 8950 8951 8952 8953 8954 8955 8956

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8957
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8958
				/*
8959
				 * The LBF_DST_PINNED logic could have changed
8960 8961
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
8962
				 */
8963
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8964 8965
			}
			sd->last_balance = jiffies;
8966
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8967 8968 8969 8970 8971 8972 8973 8974
		}
		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;
		}
8975 8976
	}
	if (need_decay) {
8977
		/*
8978 8979
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
8980
		 */
8981 8982
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
8983
	}
8984
	rcu_read_unlock();
8985 8986 8987 8988 8989 8990

	/*
	 * 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.
	 */
8991
	if (likely(update_next_balance)) {
8992
		rq->next_balance = next_balance;
8993 8994 8995 8996 8997 8998 8999 9000 9001 9002 9003 9004 9005 9006

#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
	}
9007 9008
}

9009
#ifdef CONFIG_NO_HZ_COMMON
9010
/*
9011
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
9012 9013
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
9014
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
9015
{
9016
	int this_cpu = this_rq->cpu;
9017 9018
	struct rq *rq;
	int balance_cpu;
9019 9020 9021
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
9022

9023 9024 9025
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
9026 9027

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9028
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9029 9030 9031 9032 9033 9034 9035
			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.
		 */
9036
		if (need_resched())
9037 9038
			break;

V
Vincent Guittot 已提交
9039 9040
		rq = cpu_rq(balance_cpu);

9041 9042 9043 9044 9045
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9046 9047 9048
			struct rq_flags rf;

			rq_lock_irq(rq, &rf);
9049
			update_rq_clock(rq);
9050
			cpu_load_update_idle(rq);
9051 9052
			rq_unlock_irq(rq, &rf);

9053 9054
			rebalance_domains(rq, CPU_IDLE);
		}
9055

9056 9057 9058 9059
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9060
	}
9061 9062 9063 9064 9065 9066 9067 9068

	/*
	 * 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;
9069 9070
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
9071 9072 9073
}

/*
9074
 * Current heuristic for kicking the idle load balancer in the presence
9075
 * of an idle cpu in the system.
9076
 *   - This rq has more than one task.
9077 9078 9079 9080
 *   - 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.
9081 9082
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
9083
 */
9084
static inline bool nohz_kick_needed(struct rq *rq)
9085 9086
{
	unsigned long now = jiffies;
9087
	struct sched_domain_shared *sds;
9088
	struct sched_domain *sd;
T
Tim Chen 已提交
9089
	int nr_busy, i, cpu = rq->cpu;
9090
	bool kick = false;
9091

9092
	if (unlikely(rq->idle_balance))
9093
		return false;
9094

9095 9096 9097 9098
       /*
	* 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.
	*/
9099
	set_cpu_sd_state_busy();
9100
	nohz_balance_exit_idle(cpu);
9101 9102 9103 9104 9105 9106

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
9107
		return false;
9108 9109

	if (time_before(now, nohz.next_balance))
9110
		return false;
9111

9112
	if (rq->nr_running >= 2)
9113
		return true;
9114

9115
	rcu_read_lock();
9116 9117 9118 9119 9120 9121 9122
	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);
9123 9124 9125 9126 9127
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

9128
	}
9129

9130 9131 9132 9133 9134 9135 9136 9137
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
9138

9139
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
T
Tim Chen 已提交
9140 9141 9142 9143 9144
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;
9145

T
Tim Chen 已提交
9146 9147 9148 9149 9150 9151
			if (sched_asym_prefer(i, cpu)) {
				kick = true;
				goto unlock;
			}
		}
	}
9152
unlock:
9153
	rcu_read_unlock();
9154
	return kick;
9155 9156
}
#else
9157
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
9158 9159 9160 9161 9162 9163
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9164
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9165
{
9166
	struct rq *this_rq = this_rq();
9167
	enum cpu_idle_type idle = this_rq->idle_balance ?
9168 9169 9170
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9171
	 * If this cpu has a pending nohz_balance_kick, then do the
9172
	 * balancing on behalf of the other idle cpus whose ticks are
9173 9174 9175 9176
	 * 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.
9177
	 */
9178
	nohz_idle_balance(this_rq, idle);
9179
	rebalance_domains(this_rq, idle);
9180 9181 9182 9183 9184
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9185
void trigger_load_balance(struct rq *rq)
9186 9187
{
	/* Don't need to rebalance while attached to NULL domain */
9188 9189 9190 9191
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9192
		raise_softirq(SCHED_SOFTIRQ);
9193
#ifdef CONFIG_NO_HZ_COMMON
9194
	if (nohz_kick_needed(rq))
9195
		nohz_balancer_kick();
9196
#endif
9197 9198
}

9199 9200 9201
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9202 9203

	update_runtime_enabled(rq);
9204 9205 9206 9207 9208
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9209 9210 9211

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9212 9213
}

9214
#endif /* CONFIG_SMP */
9215

9216 9217 9218
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
9219
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9220 9221 9222 9223 9224 9225
{
	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
9226
		entity_tick(cfs_rq, se, queued);
9227
	}
9228

9229
	if (static_branch_unlikely(&sched_numa_balancing))
9230
		task_tick_numa(rq, curr);
9231 9232 9233
}

/*
P
Peter Zijlstra 已提交
9234 9235 9236
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9237
 */
P
Peter Zijlstra 已提交
9238
static void task_fork_fair(struct task_struct *p)
9239
{
9240 9241
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9242
	struct rq *rq = this_rq();
9243
	struct rq_flags rf;
9244

9245
	rq_lock(rq, &rf);
9246 9247
	update_rq_clock(rq);

9248 9249
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9250 9251
	if (curr) {
		update_curr(cfs_rq);
9252
		se->vruntime = curr->vruntime;
9253
	}
9254
	place_entity(cfs_rq, se, 1);
9255

P
Peter Zijlstra 已提交
9256
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9257
		/*
9258 9259 9260
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9261
		swap(curr->vruntime, se->vruntime);
9262
		resched_curr(rq);
9263
	}
9264

9265
	se->vruntime -= cfs_rq->min_vruntime;
9266
	rq_unlock(rq, &rf);
9267 9268
}

9269 9270 9271 9272
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9273 9274
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9275
{
9276
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9277 9278
		return;

9279 9280 9281 9282 9283
	/*
	 * 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
9284
	if (rq->curr == p) {
9285
		if (p->prio > oldprio)
9286
			resched_curr(rq);
9287
	} else
9288
		check_preempt_curr(rq, p, 0);
9289 9290
}

9291
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9292 9293 9294 9295
{
	struct sched_entity *se = &p->se;

	/*
9296 9297 9298 9299 9300 9301 9302 9303 9304 9305
	 * 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
9306
	 *
9307 9308 9309 9310
	 * - 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
9311
	 */
9312 9313 9314 9315 9316 9317
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9318 9319 9320 9321 9322 9323 9324 9325 9326 9327 9328 9329 9330 9331 9332 9333 9334 9335
#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;

9336
		update_load_avg(cfs_rq, se, UPDATE_TG);
9337 9338 9339 9340 9341 9342
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9343
static void detach_entity_cfs_rq(struct sched_entity *se)
9344 9345 9346
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9347
	/* Catch up with the cfs_rq and remove our load when we leave */
9348
	update_load_avg(cfs_rq, se, 0);
9349
	detach_entity_load_avg(cfs_rq, se);
9350
	update_tg_load_avg(cfs_rq, false);
9351
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9352 9353
}

9354
static void attach_entity_cfs_rq(struct sched_entity *se)
9355
{
9356
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9357 9358

#ifdef CONFIG_FAIR_GROUP_SCHED
9359 9360 9361 9362 9363 9364
	/*
	 * 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
9365

9366
	/* Synchronize entity with its cfs_rq */
9367
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9368
	attach_entity_load_avg(cfs_rq, se);
9369
	update_tg_load_avg(cfs_rq, false);
9370
	propagate_entity_cfs_rq(se);
9371 9372 9373 9374 9375 9376 9377 9378 9379 9380 9381 9382 9383 9384 9385 9386 9387 9388 9389 9390 9391 9392 9393 9394 9395
}

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);
9396 9397 9398 9399

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9400

9401 9402 9403 9404 9405 9406 9407 9408
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);
9409

9410
	if (task_on_rq_queued(p)) {
9411
		/*
9412 9413 9414
		 * 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.
9415
		 */
9416 9417 9418 9419
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9420
	}
9421 9422
}

9423 9424 9425 9426 9427 9428 9429 9430 9431
/* 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;

9432 9433 9434 9435 9436 9437 9438
	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);
	}
9439 9440
}

9441 9442
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9443
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9444 9445 9446 9447
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9448
#ifdef CONFIG_SMP
9449 9450 9451
#ifdef CONFIG_FAIR_GROUP_SCHED
	cfs_rq->propagate_avg = 0;
#endif
9452 9453
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
9454
#endif
9455 9456
}

P
Peter Zijlstra 已提交
9457
#ifdef CONFIG_FAIR_GROUP_SCHED
9458 9459 9460 9461 9462 9463 9464 9465
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;
}

9466
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9467
{
9468
	detach_task_cfs_rq(p);
9469
	set_task_rq(p, task_cpu(p));
9470 9471 9472 9473 9474

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9475
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9476
}
9477

9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488 9489 9490
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;
	}
}

9491 9492 9493 9494 9495 9496 9497 9498 9499
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]);
9500
		if (tg->se)
9501 9502 9503 9504 9505 9506 9507 9508 9509 9510
			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;
9511
	struct cfs_rq *cfs_rq;
9512 9513 9514 9515 9516 9517 9518 9519 9520 9521 9522 9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537
	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]);
9538
		init_entity_runnable_average(se);
9539 9540 9541 9542 9543 9544 9545 9546 9547 9548
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9549 9550 9551 9552 9553 9554 9555 9556 9557 9558 9559
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);
9560
		update_rq_clock(rq);
9561
		attach_entity_cfs_rq(se);
9562
		sync_throttle(tg, i);
9563 9564 9565 9566
		raw_spin_unlock_irq(&rq->lock);
	}
}

9567
void unregister_fair_sched_group(struct task_group *tg)
9568 9569
{
	unsigned long flags;
9570 9571
	struct rq *rq;
	int cpu;
9572

9573 9574 9575
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
9576

9577 9578 9579 9580 9581 9582 9583 9584 9585 9586 9587 9588 9589
		/*
		 * 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);
	}
9590 9591 9592 9593 9594 9595 9596 9597 9598 9599 9600 9601 9602 9603 9604 9605 9606 9607 9608
}

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
9609
	if (!parent) {
9610
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
9611 9612
		se->depth = 0;
	} else {
9613
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
9614 9615
		se->depth = parent->depth + 1;
	}
9616 9617

	se->my_q = cfs_rq;
9618 9619
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
9620 9621 9622 9623 9624 9625 9626 9627 9628 9629 9630 9631 9632 9633 9634 9635 9636 9637 9638 9639 9640 9641 9642 9643
	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);
9644 9645
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
9646 9647

		/* Propagate contribution to hierarchy */
9648
		rq_lock_irqsave(rq, &rf);
9649
		update_rq_clock(rq);
9650
		for_each_sched_entity(se) {
9651
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
9652 9653
			update_cfs_shares(se);
		}
9654
		rq_unlock_irqrestore(rq, &rf);
9655 9656 9657 9658 9659 9660 9661 9662 9663 9664 9665 9666 9667 9668 9669
	}

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;
}

9670 9671
void online_fair_sched_group(struct task_group *tg) { }

9672
void unregister_fair_sched_group(struct task_group *tg) { }
9673 9674 9675

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
9676

9677
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9678 9679 9680 9681 9682 9683 9684 9685 9686
{
	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)
9687
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9688 9689 9690 9691

	return rr_interval;
}

9692 9693 9694
/*
 * All the scheduling class methods:
 */
9695
const struct sched_class fair_sched_class = {
9696
	.next			= &idle_sched_class,
9697 9698 9699
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
9700
	.yield_to_task		= yield_to_task_fair,
9701

I
Ingo Molnar 已提交
9702
	.check_preempt_curr	= check_preempt_wakeup,
9703 9704 9705 9706

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

9707
#ifdef CONFIG_SMP
L
Li Zefan 已提交
9708
	.select_task_rq		= select_task_rq_fair,
9709
	.migrate_task_rq	= migrate_task_rq_fair,
9710

9711 9712
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
9713

9714
	.task_dead		= task_dead_fair,
9715
	.set_cpus_allowed	= set_cpus_allowed_common,
9716
#endif
9717

9718
	.set_curr_task          = set_curr_task_fair,
9719
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
9720
	.task_fork		= task_fork_fair,
9721 9722

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
9723
	.switched_from		= switched_from_fair,
9724
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
9725

9726 9727
	.get_rr_interval	= get_rr_interval_fair,

9728 9729
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
9730
#ifdef CONFIG_FAIR_GROUP_SCHED
9731
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
9732
#endif
9733 9734 9735
};

#ifdef CONFIG_SCHED_DEBUG
9736
void print_cfs_stats(struct seq_file *m, int cpu)
9737
{
9738
	struct cfs_rq *cfs_rq, *pos;
9739

9740
	rcu_read_lock();
9741
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
9742
		print_cfs_rq(m, cpu, cfs_rq);
9743
	rcu_read_unlock();
9744
}
9745 9746 9747 9748 9749 9750 9751 9752 9753 9754 9755 9756 9757 9758 9759 9760 9761 9762 9763 9764 9765

#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 */
9766 9767 9768 9769 9770 9771

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

9772
#ifdef CONFIG_NO_HZ_COMMON
9773
	nohz.next_balance = jiffies;
9774 9775 9776 9777 9778
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}