fair.c 246.9 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */

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

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

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

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

	w = scale_load_down(lw->weight);

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
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	struct sched_entity *curr = cfs_rq->curr;

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	u64 vruntime = cfs_rq->min_vruntime;

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	if (curr) {
		if (curr->on_rq)
			vruntime = curr->vruntime;
		else
			curr = NULL;
	}
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	if (cfs_rq->rb_leftmost) {
		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
						   struct sched_entity,
						   run_node);

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		if (!curr)
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			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

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

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	int leftmost = 1;

	/*
	 * Find the right place in the rbtree:
	 */
	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_entity, run_node);
		/*
		 * We dont care about collisions. Nodes with
		 * the same key stay together.
		 */
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		if (entity_before(se, entry)) {
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			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

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

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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	if (cfs_rq->rb_leftmost == &se->run_node) {
		struct rb_node *next_node;

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

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struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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/*
 * The idea is to set a period in which each task runs once.
 *
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 * When there are too many tasks (sched_nr_latency) we have to stretch
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 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
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static u64 __sched_period(unsigned long nr_running)
{
676 677 678 679
	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
680 681
}

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

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

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

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

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

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

720
#ifdef CONFIG_SMP
721 722 723

#include "sched-pelt.h"

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

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

732 733 734 735 736 737 738
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
739 740 741 742 743 744 745 746
	/*
	 * Tasks are intialized with full load to be seen as heavy tasks until
	 * they get a chance to stabilize to their real load level.
	 * Group entities are intialized with zero load to reflect the fact that
	 * nothing has been attached to the task group yet.
	 */
	if (entity_is_task(se))
		sa->load_avg = scale_load_down(se->load.weight);
747
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
748 749 750 751 752
	/*
	 * At this point, util_avg won't be used in select_task_rq_fair anyway
	 */
	sa->util_avg = 0;
	sa->util_sum = 0;
753
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
754
}
755

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

759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
788
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
789 790 791 792 793 794 795 796 797 798 799 800 801

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

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
	}
802 803 804 805 806 807 808

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
809
			update_cfs_rq_load_avg(now, cfs_rq);
810 811 812 813 814 815
			attach_entity_load_avg(cfs_rq, se);
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
816
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
817 818 819 820
			return;
		}
	}

821
	attach_entity_cfs_rq(se);
822 823
}

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

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

	if (unlikely(!curr))
		return;

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

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

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

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

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

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

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

	account_cfs_rq_runtime(cfs_rq, delta_exec);
872 873
}

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

879
static inline void
880
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
881
{
882 883 884 885 886 887 888
	u64 wait_start, prev_wait_start;

	if (!schedstat_enabled())
		return;

	wait_start = rq_clock(rq_of(cfs_rq));
	prev_wait_start = schedstat_val(se->statistics.wait_start);
889 890

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

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

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

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

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

	if (entity_is_task(se)) {
		p = task_of(se);
		if (task_on_rq_migrating(p)) {
			/*
			 * Preserve migrating task's wait time so wait_start
			 * time stamp can be adjusted to accumulate wait time
			 * prior to migration.
			 */
916
			schedstat_set(se->statistics.wait_start, delta);
917 918 919 920 921
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

922 923 924 925 926
	schedstat_set(se->statistics.wait_max,
		      max(schedstat_val(se->statistics.wait_max), delta));
	schedstat_inc(se->statistics.wait_count);
	schedstat_add(se->statistics.wait_sum, delta);
	schedstat_set(se->statistics.wait_start, 0);
927 928
}

929
static inline void
930 931 932
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
933 934 935 936 937 938 939
	u64 sleep_start, block_start;

	if (!schedstat_enabled())
		return;

	sleep_start = schedstat_val(se->statistics.sleep_start);
	block_start = schedstat_val(se->statistics.block_start);
940 941 942 943

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

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

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

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

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

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

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

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

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

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

			trace_sched_stat_blocked(tsk, delta);

			/*
			 * Blocking time is in units of nanosecs, so shift by
			 * 20 to get a milliseconds-range estimation of the
			 * amount of time that the task spent sleeping:
			 */
			if (unlikely(prof_on == SLEEP_PROFILING)) {
				profile_hits(SLEEP_PROFILING,
						(void *)get_wchan(tsk),
						delta >> 20);
			}
			account_scheduler_latency(tsk, delta >> 10, 0);
		}
	}
995 996
}

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

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

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

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

	if (!schedstat_enabled())
		return;

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

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

1034 1035 1036 1037 1038 1039
		if (tsk->state & TASK_INTERRUPTIBLE)
			schedstat_set(se->statistics.sleep_start,
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
			schedstat_set(se->statistics.block_start,
				      rq_clock(rq_of(cfs_rq)));
1040 1041 1042
	}
}

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

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

1059 1060
#ifdef CONFIG_NUMA_BALANCING
/*
1061 1062 1063
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
1064
 */
1065 1066
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1067 1068 1069

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

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

1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

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

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

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

static unsigned int task_scan_min(struct task_struct *p)
{
1098
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1099 1100 1101
	unsigned int scan, floor;
	unsigned int windows = 1;

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

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

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

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

1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running += (p->numa_preferred_nid != -1);
	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

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

1132 1133 1134 1135 1136
struct numa_group {
	atomic_t refcount;

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

	struct rcu_head rcu;
1141
	unsigned long total_faults;
1142
	unsigned long max_faults_cpu;
1143 1144 1145 1146 1147
	/*
	 * Faults_cpu is used to decide whether memory should move
	 * towards the CPU. As a consequence, these stats are weighted
	 * more by CPU use than by memory faults.
	 */
1148
	unsigned long *faults_cpu;
1149
	unsigned long faults[0];
1150 1151
};

1152 1153 1154 1155 1156 1157 1158 1159 1160
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

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

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

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

1166 1167 1168 1169 1170 1171 1172
/*
 * The averaged statistics, shared & private, memory & cpu,
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1173
{
1174
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1175 1176 1177 1178
}

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

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

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

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

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

1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

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

1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

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

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

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

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

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

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

		score += faults;
	}

	return score;
}

1278 1279 1280 1281 1282 1283
/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
1284 1285
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1286
{
1287
	unsigned long faults, total_faults;
1288

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

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

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

1300
	return 1000 * faults / total_faults;
1301 1302
}

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

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1314 1315
		return 0;

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

1319
	return 1000 * faults / total_faults;
1320 1321
}

1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

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

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

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

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

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

	/*
1370 1371 1372 1373 1374 1375
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1376
	 */
1377 1378
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1379 1380
}

1381
static unsigned long weighted_cpuload(struct rq *rq);
1382 1383
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1384
static unsigned long capacity_of(int cpu);
1385

1386
/* Cached statistics for all CPUs within a node */
1387
struct numa_stats {
1388
	unsigned long nr_running;
1389
	unsigned long load;
1390 1391

	/* Total compute capacity of CPUs on a node */
1392
	unsigned long compute_capacity;
1393 1394

	/* Approximate capacity in terms of runnable tasks on a node */
1395
	unsigned long task_capacity;
1396
	int has_free_capacity;
1397
};
1398

1399 1400 1401 1402 1403
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1404 1405
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1406 1407 1408 1409 1410 1411

	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;
1412
		ns->load += weighted_cpuload(rq);
1413
		ns->compute_capacity += capacity_of(cpu);
1414 1415

		cpus++;
1416 1417
	}

1418 1419 1420 1421 1422
	/*
	 * 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.
	 *
1423 1424
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1425 1426 1427 1428
	 */
	if (!cpus)
		return;

1429 1430 1431 1432 1433 1434
	/* 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));
1435
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1436 1437
}

1438 1439
struct task_numa_env {
	struct task_struct *p;
1440

1441 1442
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1443

1444
	struct numa_stats src_stats, dst_stats;
1445

1446
	int imbalance_pct;
1447
	int dist;
1448 1449 1450

	struct task_struct *best_task;
	long best_imp;
1451 1452 1453
	int best_cpu;
};

1454 1455 1456 1457 1458
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);
1459 1460
	if (p)
		get_task_struct(p);
1461 1462 1463 1464 1465 1466

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

1467
static bool load_too_imbalanced(long src_load, long dst_load,
1468 1469
				struct task_numa_env *env)
{
1470 1471
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482
	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;
1483 1484

	/* We care about the slope of the imbalance, not the direction. */
1485 1486
	if (dst_load < src_load)
		swap(dst_load, src_load);
1487 1488

	/* Is the difference below the threshold? */
1489 1490
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1491 1492 1493 1494 1495
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1496
	 * Compare it with the old imbalance.
1497
	 */
1498
	orig_src_load = env->src_stats.load;
1499
	orig_dst_load = env->dst_stats.load;
1500

1501 1502
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1503

1504 1505 1506 1507 1508
	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);
1509 1510
}

1511 1512 1513 1514 1515 1516
/*
 * 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
 */
1517 1518
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1519 1520 1521 1522
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1523
	long src_load, dst_load;
1524
	long load;
1525
	long imp = env->p->numa_group ? groupimp : taskimp;
1526
	long moveimp = imp;
1527
	int dist = env->dist;
1528 1529

	rcu_read_lock();
1530 1531
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1532 1533
		cur = NULL;

1534 1535 1536 1537 1538 1539 1540
	/*
	 * 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;

1541 1542 1543 1544 1545 1546 1547 1548 1549
	/*
	 * "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 */
1550
		if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1551 1552
			goto unlock;

1553 1554
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1555
		 * in any group then look only at task weights.
1556
		 */
1557
		if (cur->numa_group == env->p->numa_group) {
1558 1559
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1560 1561 1562 1563 1564 1565
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1566
		} else {
1567 1568 1569 1570 1571 1572
			/*
			 * 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)
1573 1574
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1575
			else
1576 1577
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1578
		}
1579 1580
	}

1581
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1582 1583 1584 1585
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1586
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1587
		    !env->dst_stats.has_free_capacity)
1588 1589 1590 1591 1592 1593
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1594 1595
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1596 1597 1598 1599 1600 1601
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1602 1603 1604
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1605

1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622
	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;

1623
	if (cur) {
1624 1625 1626
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1627 1628
	}

1629
	if (load_too_imbalanced(src_load, dst_load, env))
1630 1631
		goto unlock;

1632 1633 1634 1635
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1636 1637 1638 1639 1640 1641
	if (!cur) {
		/*
		 * select_idle_siblings() uses an per-cpu cpumask that
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1642 1643
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1644 1645
		local_irq_enable();
	}
1646

1647 1648 1649 1650 1651 1652
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1653 1654
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1655 1656 1657 1658 1659
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1660
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1661 1662 1663
			continue;

		env->dst_cpu = cpu;
1664
		task_numa_compare(env, taskimp, groupimp);
1665 1666 1667
	}
}

1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684
/* 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
	 */
1685 1686 1687
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1688 1689 1690 1691 1692
		return true;

	return false;
}

1693 1694 1695 1696
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1697

1698
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1699
		.src_nid = task_node(p),
1700 1701 1702 1703 1704

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1705
		.best_cpu = -1,
1706 1707
	};
	struct sched_domain *sd;
1708
	unsigned long taskweight, groupweight;
1709
	int nid, ret, dist;
1710
	long taskimp, groupimp;
1711

1712
	/*
1713 1714 1715 1716 1717 1718
	 * 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.
1719 1720
	 */
	rcu_read_lock();
1721
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1722 1723
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1724 1725
	rcu_read_unlock();

1726 1727 1728 1729 1730 1731 1732
	/*
	 * 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)) {
1733
		p->numa_preferred_nid = task_node(p);
1734 1735 1736
		return -EINVAL;
	}

1737
	env.dst_nid = p->numa_preferred_nid;
1738 1739 1740 1741 1742 1743
	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;
1744
	update_numa_stats(&env.dst_stats, env.dst_nid);
1745

1746
	/* Try to find a spot on the preferred nid. */
1747 1748
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1749

1750 1751 1752 1753 1754 1755 1756
	/*
	 * 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.
	 */
1757
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1758 1759 1760
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1761

1762
			dist = node_distance(env.src_nid, env.dst_nid);
1763 1764 1765 1766 1767
			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);
			}
1768

1769
			/* Only consider nodes where both task and groups benefit */
1770 1771
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1772
			if (taskimp < 0 && groupimp < 0)
1773 1774
				continue;

1775
			env.dist = dist;
1776 1777
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1778 1779
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1780 1781 1782
		}
	}

1783 1784 1785 1786 1787 1788 1789 1790
	/*
	 * 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.
	 */
1791
	if (p->numa_group) {
1792 1793
		struct numa_group *ng = p->numa_group;

1794 1795 1796 1797 1798
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1799
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1800 1801 1802 1803 1804 1805
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1806

1807 1808 1809 1810 1811 1812
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
	p->numa_scan_period = task_scan_min(p);

1813
	if (env.best_task == NULL) {
1814 1815 1816
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1817 1818 1819 1820
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1821 1822
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1823 1824
	put_task_struct(env.best_task);
	return ret;
1825 1826
}

1827 1828 1829
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1830 1831
	unsigned long interval = HZ;

1832
	/* This task has no NUMA fault statistics yet */
1833
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1834 1835
		return;

1836
	/* Periodically retry migrating the task to the preferred node */
1837 1838
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1839 1840

	/* Success if task is already running on preferred CPU */
1841
	if (task_node(p) == p->numa_preferred_nid)
1842 1843 1844
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1845
	task_numa_migrate(p);
1846 1847
}

1848
/*
1849
 * Find out how many nodes on the workload is actively running on. Do this by
1850 1851 1852 1853
 * 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.
 */
1854
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1855 1856
{
	unsigned long faults, max_faults = 0;
1857
	int nid, active_nodes = 0;
1858 1859 1860 1861 1862 1863 1864 1865 1866

	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);
1867 1868
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1869
	}
1870 1871 1872

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1873 1874
}

1875 1876 1877
/*
 * 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
1878 1879 1880
 * 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.
1881 1882
 */
#define NUMA_PERIOD_SLOTS 10
1883
#define NUMA_PERIOD_THRESHOLD 7
1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894

/*
 * 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;
1895
	int lr_ratio, ps_ratio;
1896 1897 1898 1899 1900 1901 1902 1903
	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
1904 1905 1906
	 * 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
1907
	 */
1908
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924
		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);
1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943
	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;
1944 1945 1946 1947 1948
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1949 1950 1951
		 * 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.
1952
		 */
1953 1954
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1955 1956 1957 1958 1959 1960 1961
	}

	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));
}

1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979
/*
 * 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 {
1980 1981
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1982 1983 1984 1985 1986 1987 1988 1989
	}

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

	return delta;
}

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036
/*
 * 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;
2037
		nodemask_t max_group = NODE_MASK_NONE;
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
		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. */
2071 2072
		if (!max_faults)
			break;
2073 2074 2075 2076 2077
		nodes = max_group;
	}
	return nid;
}

2078 2079
static void task_numa_placement(struct task_struct *p)
{
2080 2081
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2082
	unsigned long fault_types[2] = { 0, 0 };
2083 2084
	unsigned long total_faults;
	u64 runtime, period;
2085
	spinlock_t *group_lock = NULL;
2086

2087 2088 2089 2090 2091
	/*
	 * 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:
	 */
2092
	seq = READ_ONCE(p->mm->numa_scan_seq);
2093 2094 2095
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2096
	p->numa_scan_period_max = task_scan_max(p);
2097

2098 2099 2100 2101
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2102 2103 2104
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2105
		spin_lock_irq(group_lock);
2106 2107
	}

2108 2109
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2110 2111
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2112
		unsigned long faults = 0, group_faults = 0;
2113
		int priv;
2114

2115
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2116
			long diff, f_diff, f_weight;
2117

2118 2119 2120 2121
			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);
2122

2123
			/* Decay existing window, copy faults since last scan */
2124 2125 2126
			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;
2127

2128 2129 2130 2131 2132 2133 2134 2135
			/*
			 * 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);
2136
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2137
				   (total_faults + 1);
2138 2139
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2140

2141 2142 2143
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2144
			p->total_numa_faults += diff;
2145
			if (p->numa_group) {
2146 2147 2148 2149 2150 2151 2152 2153 2154
				/*
				 * 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;
2155
				p->numa_group->total_faults += diff;
2156
				group_faults += p->numa_group->faults[mem_idx];
2157
			}
2158 2159
		}

2160 2161 2162 2163
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2164 2165 2166 2167 2168 2169 2170

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

2171 2172
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2173
	if (p->numa_group) {
2174
		numa_group_count_active_nodes(p->numa_group);
2175
		spin_unlock_irq(group_lock);
2176
		max_nid = preferred_group_nid(p, max_group_nid);
2177 2178
	}

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

2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199
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);
}

2200 2201
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2202 2203 2204 2205 2206 2207 2208 2209 2210
{
	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) +
2211
				    4*nr_node_ids*sizeof(unsigned long);
2212 2213 2214 2215 2216 2217

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

		atomic_set(&grp->refcount, 1);
2218 2219
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2220
		spin_lock_init(&grp->lock);
2221
		grp->gid = p->pid;
2222
		/* Second half of the array tracks nids where faults happen */
2223 2224
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2225

2226
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2227
			grp->faults[i] = p->numa_faults[i];
2228

2229
		grp->total_faults = p->total_numa_faults;
2230

2231 2232 2233 2234 2235
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2236
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2237 2238

	if (!cpupid_match_pid(tsk, cpupid))
2239
		goto no_join;
2240 2241 2242

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2243
		goto no_join;
2244 2245 2246

	my_grp = p->numa_group;
	if (grp == my_grp)
2247
		goto no_join;
2248 2249 2250 2251 2252 2253

	/*
	 * 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)
2254
		goto no_join;
2255 2256 2257 2258 2259

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2260
		goto no_join;
2261

2262 2263 2264 2265 2266 2267 2268
	/* 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;
2269

2270 2271 2272
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2273
	if (join && !get_numa_group(grp))
2274
		goto no_join;
2275 2276 2277 2278 2279 2280

	rcu_read_unlock();

	if (!join)
		return;

2281 2282
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2283

2284
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2285 2286
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2287
	}
2288 2289
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2290 2291 2292 2293 2294

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

	spin_unlock(&my_grp->lock);
2295
	spin_unlock_irq(&grp->lock);
2296 2297 2298 2299

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2300 2301 2302 2303 2304
	return;

no_join:
	rcu_read_unlock();
	return;
2305 2306 2307 2308 2309
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2310
	void *numa_faults = p->numa_faults;
2311 2312
	unsigned long flags;
	int i;
2313 2314

	if (grp) {
2315
		spin_lock_irqsave(&grp->lock, flags);
2316
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2317
			grp->faults[i] -= p->numa_faults[i];
2318
		grp->total_faults -= p->total_numa_faults;
2319

2320
		grp->nr_tasks--;
2321
		spin_unlock_irqrestore(&grp->lock, flags);
2322
		RCU_INIT_POINTER(p->numa_group, NULL);
2323 2324 2325
		put_numa_group(grp);
	}

2326
	p->numa_faults = NULL;
2327
	kfree(numa_faults);
2328 2329
}

2330 2331 2332
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2333
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2334 2335
{
	struct task_struct *p = current;
2336
	bool migrated = flags & TNF_MIGRATED;
2337
	int cpu_node = task_node(current);
2338
	int local = !!(flags & TNF_FAULT_LOCAL);
2339
	struct numa_group *ng;
2340
	int priv;
2341

2342
	if (!static_branch_likely(&sched_numa_balancing))
2343 2344
		return;

2345 2346 2347 2348
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2349
	/* Allocate buffer to track faults on a per-node basis */
2350 2351
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2352
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2353

2354 2355
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2356
			return;
2357

2358
		p->total_numa_faults = 0;
2359
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2360
	}
2361

2362 2363 2364 2365 2366 2367 2368 2369
	/*
	 * 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);
2370
		if (!priv && !(flags & TNF_NO_GROUP))
2371
			task_numa_group(p, last_cpupid, flags, &priv);
2372 2373
	}

2374 2375 2376 2377 2378 2379
	/*
	 * 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.
	 */
2380 2381 2382 2383
	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))
2384 2385
		local = 1;

2386
	task_numa_placement(p);
2387

2388 2389 2390 2391 2392
	/*
	 * 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))
2393 2394
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2395 2396
	if (migrated)
		p->numa_pages_migrated += pages;
2397 2398
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2399

2400 2401
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2402
	p->numa_faults_locality[local] += pages;
2403 2404
}

2405 2406
static void reset_ptenuma_scan(struct task_struct *p)
{
2407 2408 2409 2410 2411 2412 2413 2414
	/*
	 * 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:
	 */
2415
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2416 2417 2418
	p->mm->numa_scan_offset = 0;
}

2419 2420 2421 2422 2423 2424 2425 2426 2427
/*
 * 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;
2428
	u64 runtime = p->se.sum_exec_runtime;
2429
	struct vm_area_struct *vma;
2430
	unsigned long start, end;
2431
	unsigned long nr_pte_updates = 0;
2432
	long pages, virtpages;
2433

2434
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447

	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;

2448
	if (!mm->numa_next_scan) {
2449 2450
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2451 2452
	}

2453 2454 2455 2456 2457 2458 2459
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2460 2461 2462 2463
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2464

2465
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2466 2467 2468
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2469 2470 2471 2472 2473 2474
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2475 2476 2477
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2478
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2479 2480
	if (!pages)
		return;
2481

2482

2483 2484
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2485
	vma = find_vma(mm, start);
2486 2487
	if (!vma) {
		reset_ptenuma_scan(p);
2488
		start = 0;
2489 2490
		vma = mm->mmap;
	}
2491
	for (; vma; vma = vma->vm_next) {
2492
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2493
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2494
			continue;
2495
		}
2496

2497 2498 2499 2500 2501 2502 2503 2504 2505 2506
		/*
		 * 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
2507 2508 2509 2510 2511 2512
		/*
		 * 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;
2513

2514 2515 2516 2517
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2518
			nr_pte_updates = change_prot_numa(vma, start, end);
2519 2520

			/*
2521 2522 2523 2524 2525 2526
			 * 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.
2527 2528 2529
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2530
			virtpages -= (end - start) >> PAGE_SHIFT;
2531

2532
			start = end;
2533
			if (pages <= 0 || virtpages <= 0)
2534
				goto out;
2535 2536

			cond_resched();
2537
		} while (end != vma->vm_end);
2538
	}
2539

2540
out:
2541
	/*
P
Peter Zijlstra 已提交
2542 2543 2544 2545
	 * 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.
2546 2547
	 */
	if (vma)
2548
		mm->numa_scan_offset = start;
2549 2550 2551
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562

	/*
	 * 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;
	}
2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587
}

/*
 * 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;

2588
	if (now > curr->node_stamp + period) {
2589
		if (!curr->node_stamp)
2590
			curr->numa_scan_period = task_scan_min(curr);
2591
		curr->node_stamp += period;
2592 2593 2594 2595 2596 2597 2598

		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);
		}
	}
}
2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652

/*
 * Can a task be moved from prev_cpu to this_cpu without causing a load
 * imbalance that would trigger the load balancer?
 */
static inline bool numa_wake_affine(struct sched_domain *sd,
				    struct task_struct *p, int this_cpu,
				    int prev_cpu, int sync)
{
	struct numa_stats prev_load, this_load;
	s64 this_eff_load, prev_eff_load;

	update_numa_stats(&prev_load, cpu_to_node(prev_cpu));
	update_numa_stats(&this_load, cpu_to_node(this_cpu));

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

		if (this_load.load > current_load)
			this_load.load -= current_load;
		else
			this_load.load = 0;
	}

	/*
	 * In low-load situations, where this_cpu's node is idle due to the
	 * sync cause above having dropped this_load.load to 0, move the task.
	 * Moving to an idle socket will not create a bad imbalance.
	 *
	 * Otherwise check if the nodes are near enough in load to allow this
	 * task to be woken on this_cpu's node.
	 */
	if (this_load.load > 0) {
		unsigned long task_load = task_h_load(p);

		this_eff_load = 100;
		this_eff_load *= prev_load.compute_capacity;

		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
		prev_eff_load *= this_load.compute_capacity;

		this_eff_load *= this_load.load + task_load;
		prev_eff_load *= prev_load.load - task_load;

		return this_eff_load <= prev_eff_load;
	}

	return true;
}
2653 2654 2655 2656
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2657 2658 2659 2660 2661 2662 2663 2664

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)
{
}
2665

2666
#ifdef CONFIG_SMP
2667 2668 2669 2670 2671 2672
static inline bool numa_wake_affine(struct sched_domain *sd,
				    struct task_struct *p, int this_cpu,
				    int prev_cpu, int sync)
{
	return true;
}
2673
#endif /* !SMP */
2674 2675
#endif /* CONFIG_NUMA_BALANCING */

2676 2677 2678 2679
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2680
	if (!parent_entity(se))
2681
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2682
#ifdef CONFIG_SMP
2683 2684 2685 2686 2687 2688
	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);
	}
2689
#endif
2690 2691 2692 2693 2694 2695 2696
	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);
2697
	if (!parent_entity(se))
2698
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2699
#ifdef CONFIG_SMP
2700 2701
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2702
		list_del_init(&se->group_node);
2703
	}
2704
#endif
2705 2706 2707
	cfs_rq->nr_running--;
}

2708 2709
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2710
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2711
{
2712
	long tg_weight, load, shares;
2713 2714

	/*
2715 2716 2717
	 * This really should be: cfs_rq->avg.load_avg, but instead we use
	 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
	 * the shares for small weight interactive tasks.
2718
	 */
2719
	load = scale_load_down(cfs_rq->load.weight);
2720

2721
	tg_weight = atomic_long_read(&tg->load_avg);
2722

2723 2724 2725
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2726 2727

	shares = (tg->shares * load);
2728 2729
	if (tg_weight)
		shares /= tg_weight;
2730

2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742
	/*
	 * 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.
	 */
2743 2744 2745 2746 2747 2748 2749 2750
	if (shares < MIN_SHARES)
		shares = MIN_SHARES;
	if (shares > tg->shares)
		shares = tg->shares;

	return shares;
}
# else /* CONFIG_SMP */
2751
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2752 2753 2754 2755
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
2756

P
Peter Zijlstra 已提交
2757 2758 2759
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2760 2761 2762 2763
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2764
		account_entity_dequeue(cfs_rq, se);
2765
	}
P
Peter Zijlstra 已提交
2766 2767 2768 2769 2770 2771 2772

	update_load_set(&se->load, weight);

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

2773 2774
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2775
static void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2776
{
2777
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
P
Peter Zijlstra 已提交
2778
	struct task_group *tg;
2779
	long shares;
P
Peter Zijlstra 已提交
2780

2781 2782 2783 2784
	if (!cfs_rq)
		return;

	if (throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2785
		return;
2786 2787 2788

	tg = cfs_rq->tg;

2789 2790 2791 2792
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2793
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2794 2795 2796

	reweight_entity(cfs_rq_of(se), se, shares);
}
2797

P
Peter Zijlstra 已提交
2798
#else /* CONFIG_FAIR_GROUP_SCHED */
2799
static inline void update_cfs_shares(struct sched_entity *se)
P
Peter Zijlstra 已提交
2800 2801 2802 2803
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
	if (&this_rq()->cfs == cfs_rq) {
		/*
		 * 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().
		 */
		cpufreq_update_util(rq_of(cfs_rq), 0);
	}
}

2827
#ifdef CONFIG_SMP
2828 2829 2830 2831
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
2832
static u64 decay_load(u64 val, u64 n)
2833
{
2834 2835
	unsigned int local_n;

2836
	if (unlikely(n > LOAD_AVG_PERIOD * 63))
2837 2838 2839 2840 2841 2842 2843
		return 0;

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

	/*
	 * As y^PERIOD = 1/2, we can combine
2844 2845
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2846 2847 2848 2849 2850 2851
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2852 2853
	}

2854 2855
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2856 2857
}

2858
static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
2859
{
2860
	u32 c1, c2, c3 = d3; /* y^0 == 1 */
2861

2862
	/*
P
Peter Zijlstra 已提交
2863
	 * c1 = d1 y^p
2864
	 */
2865
	c1 = decay_load((u64)d1, periods);
2866 2867

	/*
P
Peter Zijlstra 已提交
2868
	 *            p-1
2869 2870
	 * c2 = 1024 \Sum y^n
	 *            n=1
2871
	 *
2872 2873
	 *              inf        inf
	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
P
Peter Zijlstra 已提交
2874
	 *              n=0        n=p
2875
	 */
2876
	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
2877 2878

	return c1 + c2 + c3;
2879 2880
}

2881
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2882

2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893
/*
 * 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
2894 2895 2896
 *                           p-1
 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
 *                           n=1
2897
 *
P
Peter Zijlstra 已提交
2898
 *    = u y^p +					(Step 1)
2899
 *
P
Peter Zijlstra 已提交
2900 2901 2902
 *                     p-1
 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2)
 *                     n=1
2903 2904 2905 2906 2907 2908
 */
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;
2909
	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928
	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);

2929 2930 2931 2932 2933 2934 2935
		/*
		 * Step 2
		 */
		delta %= 1024;
		contrib = __accumulate_pelt_segments(periods,
				1024 - sa->period_contrib, delta);
	}
2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949
	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;
}

2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977
/*
 * 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}]
 */
2978
static __always_inline int
2979
___update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2980
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2981
{
2982
	u64 delta;
2983

2984
	delta = now - sa->last_update_time;
2985 2986 2987 2988 2989
	/*
	 * 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) {
2990
		sa->last_update_time = now;
2991 2992 2993 2994 2995 2996 2997 2998 2999 3000
		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;
3001 3002

	sa->last_update_time += delta << 10;
3003

3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015
	/*
	 * 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;

3016 3017 3018 3019 3020 3021 3022 3023 3024
	/*
	 * 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;
3025

3026 3027 3028
	/*
	 * Step 2: update *_avg.
	 */
3029
	sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib);
3030 3031
	if (cfs_rq) {
		cfs_rq->runnable_load_avg =
3032
			div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX - 1024 + sa->period_contrib);
3033
	}
3034
	sa->util_avg = sa->util_sum / (LOAD_AVG_MAX - 1024 + sa->period_contrib);
3035

3036
	return 1;
3037 3038
}

3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060
static int
__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
{
	return ___update_load_avg(now, cpu, &se->avg, 0, 0, NULL);
}

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

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

3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080
/*
 * 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)

3081
#ifdef CONFIG_FAIR_GROUP_SCHED
3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094
/**
 * 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'.
 *
3095
 * Updating tg's load_avg is necessary before update_cfs_share().
3096
 */
3097
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3098
{
3099
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3100

3101 3102 3103 3104 3105 3106
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3107 3108 3109
	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;
3110
	}
3111
}
3112

3113 3114 3115 3116 3117 3118 3119 3120
/*
 * 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)
{
3121 3122 3123
	u64 p_last_update_time;
	u64 n_last_update_time;

3124 3125 3126 3127 3128 3129 3130 3131 3132 3133
	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.
	 */
3134 3135
	if (!(se->avg.last_update_time && prev))
		return;
3136 3137

#ifndef CONFIG_64BIT
3138
	{
3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152
		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);
3153
	}
3154
#else
3155 3156
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3157
#endif
3158 3159
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3160
}
3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281

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

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

	/* Set new sched_entity's utilization */
	se->avg.util_avg = gcfs_rq->avg.util_avg;
	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;

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

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

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

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

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

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

	delta = load - se->avg.load_avg;

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

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

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

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

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

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

	if (!cfs_rq->propagate_avg)
		return 0;

	cfs_rq->propagate_avg = 0;
	return 1;
}

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

	if (entity_is_task(se))
		return 0;

	if (!test_and_clear_tg_cfs_propagate(se))
		return 0;

	cfs_rq = cfs_rq_of(se);

	set_tg_cfs_propagate(cfs_rq);

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

	return 1;
}

3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311
/*
 * 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;
}

3312
#else /* CONFIG_FAIR_GROUP_SCHED */
3313

3314
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3315 3316 3317 3318 3319 3320 3321 3322

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) {}

3323
#endif /* CONFIG_FAIR_GROUP_SCHED */
3324

3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341
/*
 * 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)

3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352
/**
 * 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.
 *
3353 3354 3355 3356
 * 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.
3357
 */
3358
static inline int
3359
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3360
{
3361
	struct sched_avg *sa = &cfs_rq->avg;
3362
	int decayed, removed_load = 0, removed_util = 0;
3363

3364
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
3365
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
3366 3367
		sub_positive(&sa->load_avg, r);
		sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
3368
		removed_load = 1;
3369
		set_tg_cfs_propagate(cfs_rq);
3370
	}
3371

3372 3373
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
3374 3375
		sub_positive(&sa->util_avg, r);
		sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
3376
		removed_util = 1;
3377
		set_tg_cfs_propagate(cfs_rq);
3378
	}
3379

3380
	decayed = __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3381

3382 3383 3384 3385
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3386

3387
	if (decayed || removed_util)
3388
		cfs_rq_util_change(cfs_rq);
3389

3390
	return decayed || removed_load;
3391 3392
}

3393 3394 3395 3396 3397 3398
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2

3399
/* Update task and its cfs_rq load average */
3400
static inline void update_load_avg(struct sched_entity *se, int flags)
3401 3402 3403 3404 3405
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);
3406
	int decayed;
3407 3408 3409 3410 3411

	/*
	 * 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
	 */
3412 3413
	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
		__update_load_avg_se(now, cpu, cfs_rq, se);
3414

3415
	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
3416 3417 3418
	decayed |= propagate_entity_load_avg(se);

	if (decayed && (flags & UPDATE_TG))
3419
		update_tg_load_avg(cfs_rq, 0);
3420 3421
}

3422 3423 3424 3425 3426 3427 3428 3429
/**
 * 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.
 */
3430 3431 3432 3433 3434 3435 3436
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3437
	set_tg_cfs_propagate(cfs_rq);
3438 3439

	cfs_rq_util_change(cfs_rq);
3440 3441
}

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

3453 3454 3455 3456
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3457
	set_tg_cfs_propagate(cfs_rq);
3458 3459

	cfs_rq_util_change(cfs_rq);
3460 3461
}

3462 3463 3464
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3465
{
3466
	struct sched_avg *sa = &se->avg;
3467

3468 3469 3470
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3471
	if (!sa->last_update_time) {
3472
		attach_entity_load_avg(cfs_rq, se);
3473
		update_tg_load_avg(cfs_rq, 0);
3474
	}
3475 3476
}

3477 3478 3479 3480 3481 3482 3483
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
3484
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3485 3486
}

3487
#ifndef CONFIG_64BIT
3488 3489
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3490
	u64 last_update_time_copy;
3491
	u64 last_update_time;
3492

3493 3494 3495 3496 3497
	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);
3498 3499 3500

	return last_update_time;
}
3501
#else
3502 3503 3504 3505
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3506 3507
#endif

3508 3509 3510 3511 3512 3513 3514 3515 3516 3517
/*
 * 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);
3518
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3519 3520
}

3521 3522 3523 3524 3525 3526 3527 3528 3529
/*
 * 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);

	/*
3530 3531 3532 3533 3534 3535 3536
	 * 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.
3537 3538
	 */

3539
	sync_entity_load_avg(se);
3540 3541
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3542
}
3543

3544 3545 3546 3547 3548 3549 3550 3551 3552 3553
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;
}

3554
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3555

3556 3557
#else /* CONFIG_SMP */

3558
static inline int
3559
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3560 3561 3562 3563
{
	return 0;
}

3564 3565 3566 3567
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0

static inline void update_load_avg(struct sched_entity *se, int not_used1)
3568
{
3569
	cfs_rq_util_change(cfs_rq_of(se));
3570 3571
}

3572 3573
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3574 3575
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3576
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3577

3578 3579 3580 3581 3582
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) {}

3583
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3584 3585 3586 3587
{
	return 0;
}

3588
#endif /* CONFIG_SMP */
3589

P
Peter Zijlstra 已提交
3590 3591 3592 3593 3594 3595 3596 3597 3598
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)
3599
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3600 3601 3602
#endif
}

3603 3604 3605
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3606
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3607

3608 3609 3610 3611 3612 3613
	/*
	 * 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
3614
	if (initial && sched_feat(START_DEBIT))
3615
		vruntime += sched_vslice(cfs_rq, se);
3616

3617
	/* sleeps up to a single latency don't count. */
3618
	if (!initial) {
3619
		unsigned long thresh = sysctl_sched_latency;
3620

3621 3622 3623 3624 3625 3626
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3627

3628
		vruntime -= thresh;
3629 3630
	}

3631
	/* ensure we never gain time by being placed backwards. */
3632
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3633 3634
}

3635 3636
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648
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())  {
3649
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3650
			     "stat_blocked and stat_runtime require the "
3651
			     "kernel parameter schedstats=enable or "
3652 3653 3654 3655 3656
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675

/*
 * 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)
 *
3676
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687
 *	  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.
 */

3688
static void
3689
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3690
{
3691 3692 3693
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3694
	/*
3695 3696
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3697
	 */
3698
	if (renorm && curr)
3699 3700
		se->vruntime += cfs_rq->min_vruntime;

3701 3702
	update_curr(cfs_rq);

3703
	/*
3704 3705 3706 3707
	 * 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.
3708
	 */
3709 3710 3711
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3712 3713 3714 3715 3716 3717 3718 3719
	/*
	 * 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
	 */
3720
	update_load_avg(se, UPDATE_TG);
3721
	enqueue_entity_load_avg(cfs_rq, se);
3722
	update_cfs_shares(se);
3723
	account_entity_enqueue(cfs_rq, se);
3724

3725
	if (flags & ENQUEUE_WAKEUP)
3726
		place_entity(cfs_rq, se, 0);
3727

3728
	check_schedstat_required();
3729 3730
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3731
	if (!curr)
3732
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3733
	se->on_rq = 1;
3734

3735
	if (cfs_rq->nr_running == 1) {
3736
		list_add_leaf_cfs_rq(cfs_rq);
3737 3738
		check_enqueue_throttle(cfs_rq);
	}
3739 3740
}

3741
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3742
{
3743 3744
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3745
		if (cfs_rq->last != se)
3746
			break;
3747 3748

		cfs_rq->last = NULL;
3749 3750
	}
}
P
Peter Zijlstra 已提交
3751

3752 3753 3754 3755
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3756
		if (cfs_rq->next != se)
3757
			break;
3758 3759

		cfs_rq->next = NULL;
3760
	}
P
Peter Zijlstra 已提交
3761 3762
}

3763 3764 3765 3766
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3767
		if (cfs_rq->skip != se)
3768
			break;
3769 3770

		cfs_rq->skip = NULL;
3771 3772 3773
	}
}

P
Peter Zijlstra 已提交
3774 3775
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3776 3777 3778 3779 3780
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3781 3782 3783

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3784 3785
}

3786
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3787

3788
static void
3789
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3790
{
3791 3792 3793 3794
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3795 3796 3797 3798 3799 3800 3801 3802 3803

	/*
	 * 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.
	 */
3804
	update_load_avg(se, UPDATE_TG);
3805
	dequeue_entity_load_avg(cfs_rq, se);
3806

3807
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3808

P
Peter Zijlstra 已提交
3809
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3810

3811
	if (se != cfs_rq->curr)
3812
		__dequeue_entity(cfs_rq, se);
3813
	se->on_rq = 0;
3814
	account_entity_dequeue(cfs_rq, se);
3815 3816

	/*
3817 3818 3819 3820
	 * 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.
3821
	 */
3822
	if (!(flags & DEQUEUE_SLEEP))
3823
		se->vruntime -= cfs_rq->min_vruntime;
3824

3825 3826 3827
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3828
	update_cfs_shares(se);
3829 3830 3831 3832 3833 3834 3835 3836 3837

	/*
	 * 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);
3838 3839 3840 3841 3842
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3843
static void
I
Ingo Molnar 已提交
3844
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3845
{
3846
	unsigned long ideal_runtime, delta_exec;
3847 3848
	struct sched_entity *se;
	s64 delta;
3849

P
Peter Zijlstra 已提交
3850
	ideal_runtime = sched_slice(cfs_rq, curr);
3851
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3852
	if (delta_exec > ideal_runtime) {
3853
		resched_curr(rq_of(cfs_rq));
3854 3855 3856 3857 3858
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869
		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;

3870 3871
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3872

3873 3874
	if (delta < 0)
		return;
3875

3876
	if (delta > ideal_runtime)
3877
		resched_curr(rq_of(cfs_rq));
3878 3879
}

3880
static void
3881
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3882
{
3883 3884 3885 3886 3887 3888 3889
	/* '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.
		 */
3890
		update_stats_wait_end(cfs_rq, se);
3891
		__dequeue_entity(cfs_rq, se);
3892
		update_load_avg(se, UPDATE_TG);
3893 3894
	}

3895
	update_stats_curr_start(cfs_rq, se);
3896
	cfs_rq->curr = se;
3897

I
Ingo Molnar 已提交
3898 3899 3900 3901 3902
	/*
	 * 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):
	 */
3903
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3904 3905 3906
		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
3907
	}
3908

3909
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3910 3911
}

3912 3913 3914
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3915 3916 3917 3918 3919 3920 3921
/*
 * 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
 */
3922 3923
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3924
{
3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935
	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 */
3936

3937 3938 3939 3940 3941
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3942 3943 3944 3945 3946 3947 3948 3949 3950 3951
		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;
		}

3952 3953 3954
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3955

3956 3957 3958 3959 3960 3961
	/*
	 * 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;

3962 3963 3964 3965 3966 3967
	/*
	 * 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;

3968
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3969 3970

	return se;
3971 3972
}

3973
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3974

3975
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3976 3977 3978 3979 3980 3981
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3982
		update_curr(cfs_rq);
3983

3984 3985 3986
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3987
	check_spread(cfs_rq, prev);
3988

3989
	if (prev->on_rq) {
3990
		update_stats_wait_start(cfs_rq, prev);
3991 3992
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3993
		/* in !on_rq case, update occurred at dequeue */
3994
		update_load_avg(prev, 0);
3995
	}
3996
	cfs_rq->curr = NULL;
3997 3998
}

P
Peter Zijlstra 已提交
3999 4000
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4001 4002
{
	/*
4003
	 * Update run-time statistics of the 'current'.
4004
	 */
4005
	update_curr(cfs_rq);
4006

4007 4008 4009
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4010
	update_load_avg(curr, UPDATE_TG);
4011
	update_cfs_shares(curr);
4012

P
Peter Zijlstra 已提交
4013 4014 4015 4016 4017
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4018
	if (queued) {
4019
		resched_curr(rq_of(cfs_rq));
4020 4021
		return;
	}
P
Peter Zijlstra 已提交
4022 4023 4024 4025 4026 4027 4028 4029
	/*
	 * 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
4030
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4031
		check_preempt_tick(cfs_rq, curr);
4032 4033
}

4034 4035 4036 4037 4038 4039

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

#ifdef CONFIG_CFS_BANDWIDTH
4040 4041

#ifdef HAVE_JUMP_LABEL
4042
static struct static_key __cfs_bandwidth_used;
4043 4044 4045

static inline bool cfs_bandwidth_used(void)
{
4046
	return static_key_false(&__cfs_bandwidth_used);
4047 4048
}

4049
void cfs_bandwidth_usage_inc(void)
4050
{
4051 4052 4053 4054 4055 4056
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
4057 4058 4059 4060 4061 4062 4063
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4064 4065
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4066 4067
#endif /* HAVE_JUMP_LABEL */

4068 4069 4070 4071 4072 4073 4074 4075
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4076 4077 4078 4079 4080 4081

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

P
Paul Turner 已提交
4082 4083 4084 4085 4086 4087 4088
/*
 * 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
 */
4089
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100
{
	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);
}

4101 4102 4103 4104 4105
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4106 4107 4108 4109
/* 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))
4110
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4111

4112
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4113 4114
}

4115 4116
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4117 4118 4119
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4120
	u64 amount = 0, min_amount, expires;
4121 4122 4123 4124 4125 4126 4127

	/* 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;
4128
	else {
P
Peter Zijlstra 已提交
4129
		start_cfs_bandwidth(cfs_b);
4130 4131 4132 4133 4134 4135

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4136
	}
P
Paul Turner 已提交
4137
	expires = cfs_b->runtime_expires;
4138 4139 4140
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4141 4142 4143 4144 4145 4146 4147
	/*
	 * 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;
4148 4149

	return cfs_rq->runtime_remaining > 0;
4150 4151
}

P
Paul Turner 已提交
4152 4153 4154 4155 4156
/*
 * 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)
4157
{
P
Paul Turner 已提交
4158 4159 4160
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4161
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4162 4163
		return;

P
Paul Turner 已提交
4164 4165 4166 4167 4168 4169 4170 4171 4172
	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
4173 4174 4175
	 * 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
4176 4177
	 */

4178
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
4179 4180 4181 4182 4183 4184 4185 4186
		/* 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;
	}
}

4187
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4188 4189
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4190
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4191 4192 4193
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4194 4195
		return;

4196 4197 4198 4199 4200
	/*
	 * 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))
4201
		resched_curr(rq_of(cfs_rq));
4202 4203
}

4204
static __always_inline
4205
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4206
{
4207
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4208 4209 4210 4211 4212
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4213 4214
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4215
	return cfs_bandwidth_used() && cfs_rq->throttled;
4216 4217
}

4218 4219 4220
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4221
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248
}

/*
 * 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) {
4249
		/* adjust cfs_rq_clock_task() */
4250
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4251
					     cfs_rq->throttled_clock_task;
4252 4253 4254 4255 4256 4257 4258 4259 4260 4261
	}

	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)];

4262 4263
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4264
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4265 4266 4267 4268 4269
	cfs_rq->throttle_count++;

	return 0;
}

4270
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4271 4272 4273 4274 4275
{
	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
4276
	bool empty;
4277 4278 4279

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

4280
	/* freeze hierarchy runnable averages while throttled */
4281 4282 4283
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300

	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)
4301
		sub_nr_running(rq, task_delta);
4302 4303

	cfs_rq->throttled = 1;
4304
	cfs_rq->throttled_clock = rq_clock(rq);
4305
	raw_spin_lock(&cfs_b->lock);
4306
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4307

4308 4309 4310 4311 4312
	/*
	 * 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
4313 4314 4315 4316 4317 4318 4319 4320

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

4321 4322 4323
	raw_spin_unlock(&cfs_b->lock);
}

4324
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4325 4326 4327 4328 4329 4330 4331
{
	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;

4332
	se = cfs_rq->tg->se[cpu_of(rq)];
4333 4334

	cfs_rq->throttled = 0;
4335 4336 4337

	update_rq_clock(rq);

4338
	raw_spin_lock(&cfs_b->lock);
4339
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4340 4341 4342
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4343 4344 4345
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363
	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)
4364
		add_nr_running(rq, task_delta);
4365 4366 4367

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4368
		resched_curr(rq);
4369 4370 4371 4372 4373 4374
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4375 4376
	u64 runtime;
	u64 starting_runtime = remaining;
4377 4378 4379 4380 4381

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4382
		struct rq_flags rf;
4383

4384
		rq_lock(rq, &rf);
4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400
		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:
4401
		rq_unlock(rq, &rf);
4402 4403 4404 4405 4406 4407

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

4408
	return starting_runtime - remaining;
4409 4410
}

4411 4412 4413 4414 4415 4416 4417 4418
/*
 * 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)
{
4419
	u64 runtime, runtime_expires;
4420
	int throttled;
4421 4422 4423

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4424
		goto out_deactivate;
4425

4426
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4427
	cfs_b->nr_periods += overrun;
4428

4429 4430 4431 4432 4433 4434
	/*
	 * 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
4435 4436 4437

	__refill_cfs_bandwidth_runtime(cfs_b);

4438 4439 4440
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4441
		return 0;
4442 4443
	}

4444 4445 4446
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4447 4448 4449
	runtime_expires = cfs_b->runtime_expires;

	/*
4450 4451 4452 4453 4454
	 * 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.
4455
	 */
4456 4457
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4458 4459 4460 4461 4462 4463 4464
		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);
4465 4466

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4467
	}
4468

4469 4470 4471 4472 4473 4474 4475
	/*
	 * 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;
4476

4477 4478 4479 4480
	return 0;

out_deactivate:
	return 1;
4481
}
4482

4483 4484 4485 4486 4487 4488 4489
/* 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;

4490 4491 4492 4493
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4494
 * hrtimer base being cleared by hrtimer_start. In the case of
4495 4496
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521
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
4522 4523 4524
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553
}

/* 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)
{
4554 4555 4556
	if (!cfs_bandwidth_used())
		return;

4557
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572
		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 */
4573 4574 4575
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4576
		return;
4577
	}
4578

4579
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4580
		runtime = cfs_b->runtime;
4581

4582 4583 4584 4585 4586 4587 4588 4589 4590 4591
	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)
4592
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4593 4594 4595
	raw_spin_unlock(&cfs_b->lock);
}

4596 4597 4598 4599 4600 4601 4602
/*
 * 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)
{
4603 4604 4605
	if (!cfs_bandwidth_used())
		return;

4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619
	/* 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);
}

4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633
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;
4634
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4635 4636
}

4637
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4638
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4639
{
4640
	if (!cfs_bandwidth_used())
4641
		return false;
4642

4643
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4644
		return false;
4645 4646 4647 4648 4649 4650

	/*
	 * 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))
4651
		return true;
4652 4653

	throttle_cfs_rq(cfs_rq);
4654
	return true;
4655
}
4656 4657 4658 4659 4660

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
4661

4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673
	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;

4674
	raw_spin_lock(&cfs_b->lock);
4675
	for (;;) {
P
Peter Zijlstra 已提交
4676
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4677 4678 4679 4680 4681
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4682 4683
	if (idle)
		cfs_b->period_active = 0;
4684
	raw_spin_unlock(&cfs_b->lock);
4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

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

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4697
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

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

P
Peter Zijlstra 已提交
4709
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4710
{
P
Peter Zijlstra 已提交
4711
	lockdep_assert_held(&cfs_b->lock);
4712

P
Peter Zijlstra 已提交
4713 4714 4715 4716 4717
	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);
	}
4718 4719 4720 4721
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4722 4723 4724 4725
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4726 4727 4728 4729
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4730 4731 4732 4733 4734 4735 4736 4737
/*
 * 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 */
4738 4739
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4740
	struct task_group *tg;
4741

4742 4743 4744 4745 4746 4747
	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)];
4748 4749 4750 4751 4752

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4753
	rcu_read_unlock();
4754 4755
}

4756
/* cpu offline callback */
4757
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4758
{
4759 4760 4761 4762 4763 4764 4765
	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)];
4766 4767 4768 4769 4770 4771 4772 4773

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4774
		cfs_rq->runtime_remaining = 1;
4775 4776 4777 4778 4779 4780
		/*
		 * 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;

4781 4782 4783
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
4784
	rcu_read_unlock();
4785 4786 4787
}

#else /* CONFIG_CFS_BANDWIDTH */
4788 4789
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4790
	return rq_clock_task(rq_of(cfs_rq));
4791 4792
}

4793
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4794
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4795
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4796
static inline void sync_throttle(struct task_group *tg, int cpu) {}
4797
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4798 4799 4800 4801 4802

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813

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;
}
4814 4815 4816 4817 4818

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) {}
4819 4820
#endif

4821 4822 4823 4824 4825
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) {}
4826
static inline void update_runtime_enabled(struct rq *rq) {}
4827
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4828 4829 4830

#endif /* CONFIG_CFS_BANDWIDTH */

4831 4832 4833 4834
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4835 4836 4837 4838 4839 4840
#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);

4841
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
4842

4843
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
4844 4845 4846 4847 4848 4849
		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)
4850
				resched_curr(rq);
P
Peter Zijlstra 已提交
4851 4852
			return;
		}
4853
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4854 4855
	}
}
4856 4857 4858 4859 4860 4861 4862 4863 4864 4865

/*
 * 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;

4866
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4867 4868 4869 4870 4871
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4872
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
4873 4874 4875 4876
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4877 4878 4879 4880

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4881 4882
#endif

4883 4884 4885 4886 4887
/*
 * 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:
 */
4888
static void
4889
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4890 4891
{
	struct cfs_rq *cfs_rq;
4892
	struct sched_entity *se = &p->se;
4893

4894 4895 4896 4897 4898 4899 4900 4901
	/*
	 * If in_iowait is set, the code below may not trigger any cpufreq
	 * utilization updates, so do it here explicitly with the IOWAIT flag
	 * passed.
	 */
	if (p->in_iowait)
		cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT);

4902
	for_each_sched_entity(se) {
4903
		if (se->on_rq)
4904 4905
			break;
		cfs_rq = cfs_rq_of(se);
4906
		enqueue_entity(cfs_rq, se, flags);
4907 4908 4909 4910 4911 4912

		/*
		 * 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.
4913
		 */
4914 4915
		if (cfs_rq_throttled(cfs_rq))
			break;
4916
		cfs_rq->h_nr_running++;
4917

4918
		flags = ENQUEUE_WAKEUP;
4919
	}
P
Peter Zijlstra 已提交
4920

P
Peter Zijlstra 已提交
4921
	for_each_sched_entity(se) {
4922
		cfs_rq = cfs_rq_of(se);
4923
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4924

4925 4926 4927
		if (cfs_rq_throttled(cfs_rq))
			break;

4928
		update_load_avg(se, UPDATE_TG);
4929
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
4930 4931
	}

Y
Yuyang Du 已提交
4932
	if (!se)
4933
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4934

4935
	hrtick_update(rq);
4936 4937
}

4938 4939
static void set_next_buddy(struct sched_entity *se);

4940 4941 4942 4943 4944
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4945
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4946 4947
{
	struct cfs_rq *cfs_rq;
4948
	struct sched_entity *se = &p->se;
4949
	int task_sleep = flags & DEQUEUE_SLEEP;
4950 4951 4952

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4953
		dequeue_entity(cfs_rq, se, flags);
4954 4955 4956 4957 4958 4959 4960 4961 4962

		/*
		 * 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;
4963
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4964

4965
		/* Don't dequeue parent if it has other entities besides us */
4966
		if (cfs_rq->load.weight) {
4967 4968
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
4969 4970 4971 4972
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
4973 4974
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
4975
			break;
4976
		}
4977
		flags |= DEQUEUE_SLEEP;
4978
	}
P
Peter Zijlstra 已提交
4979

P
Peter Zijlstra 已提交
4980
	for_each_sched_entity(se) {
4981
		cfs_rq = cfs_rq_of(se);
4982
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4983

4984 4985 4986
		if (cfs_rq_throttled(cfs_rq))
			break;

4987
		update_load_avg(se, UPDATE_TG);
4988
		update_cfs_shares(se);
P
Peter Zijlstra 已提交
4989 4990
	}

Y
Yuyang Du 已提交
4991
	if (!se)
4992
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4993

4994
	hrtick_update(rq);
4995 4996
}

4997
#ifdef CONFIG_SMP
4998 4999 5000 5001 5002

/* 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);

5003
#ifdef CONFIG_NO_HZ_COMMON
5004 5005 5006 5007 5008
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5009
 * The exact cpuload calculated at every tick would be:
5010
 *
5011 5012 5013 5014 5015 5016 5017
 *   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
5018 5019 5020
 *
 * decay_load_missed() below does efficient calculation of
 *
5021 5022 5023 5024 5025 5026
 *   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())
5027
 *
5028
 * The calculation is approximated on a 128 point scale.
5029 5030
 */
#define DEGRADE_SHIFT		7
5031 5032 5033 5034 5035 5036 5037 5038 5039

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 }
};
5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068

/*
 * 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;
}
5069
#endif /* CONFIG_NO_HZ_COMMON */
5070

5071
/**
5072
 * __cpu_load_update - update the rq->cpu_load[] statistics
5073 5074 5075 5076
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5077
 * Update rq->cpu_load[] statistics. This function is usually called every
5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103
 * 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
5104
 * term.
5105
 */
5106 5107
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5108
{
5109
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120
	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 */

5121
		old_load = this_rq->cpu_load[i];
5122
#ifdef CONFIG_NO_HZ_COMMON
5123
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5124 5125 5126 5127 5128 5129 5130 5131 5132
		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;
		}
5133
#endif
5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148
		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);
}

5149
/* Used instead of source_load when we know the type == 0 */
5150
static unsigned long weighted_cpuload(struct rq *rq)
5151
{
5152
	return cfs_rq_runnable_load_avg(&rq->cfs);
5153 5154
}

5155
#ifdef CONFIG_NO_HZ_COMMON
5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172
/*
 * 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)
5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183
{
	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.
		 */
5184
		cpu_load_update(this_rq, load, pending_updates);
5185 5186 5187
	}
}

5188 5189 5190 5191
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5192
static void cpu_load_update_idle(struct rq *this_rq)
5193 5194 5195 5196
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5197
	if (weighted_cpuload(this_rq))
5198 5199
		return;

5200
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5201 5202 5203
}

/*
5204 5205 5206 5207
 * 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.
5208
 */
5209
void cpu_load_update_nohz_start(void)
5210 5211
{
	struct rq *this_rq = this_rq();
5212 5213 5214 5215 5216 5217

	/*
	 * 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.
	 */
5218
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5219 5220 5221 5222 5223 5224 5225
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5226
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5227 5228
	struct rq *this_rq = this_rq();
	unsigned long load;
5229
	struct rq_flags rf;
5230 5231 5232 5233

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

5234
	load = weighted_cpuload(this_rq);
5235
	rq_lock(this_rq, &rf);
5236
	update_rq_clock(this_rq);
5237
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5238
	rq_unlock(this_rq, &rf);
5239
}
5240 5241 5242 5243 5244 5245 5246 5247
#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)
{
5248
#ifdef CONFIG_NO_HZ_COMMON
5249 5250
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5251
#endif
5252 5253
	cpu_load_update(this_rq, load, 1);
}
5254 5255 5256 5257

/*
 * Called from scheduler_tick()
 */
5258
void cpu_load_update_active(struct rq *this_rq)
5259
{
5260
	unsigned long load = weighted_cpuload(this_rq);
5261 5262 5263 5264 5265

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5266 5267
}

5268 5269 5270 5271 5272 5273 5274 5275 5276 5277
/*
 * 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);
5278
	unsigned long total = weighted_cpuload(rq);
5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292

	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);
5293
	unsigned long total = weighted_cpuload(rq);
5294 5295 5296 5297 5298 5299 5300

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

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

5301
static unsigned long capacity_of(int cpu)
5302
{
5303
	return cpu_rq(cpu)->cpu_capacity;
5304 5305
}

5306 5307 5308 5309 5310
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5311 5312 5313
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5314
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5315
	unsigned long load_avg = weighted_cpuload(rq);
5316 5317

	if (nr_running)
5318
		return load_avg / nr_running;
5319 5320 5321 5322

	return 0;
}

P
Peter Zijlstra 已提交
5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339
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
5340 5341
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5342
 *
M
Mike Galbraith 已提交
5343
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355
 * 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
5356
 */
5357 5358
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5359 5360
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5361
	int factor = this_cpu_read(sd_llc_size);
5362

M
Mike Galbraith 已提交
5363 5364 5365 5366 5367
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5368 5369
}

5370 5371
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
		       int prev_cpu, int sync)
5372
{
5373 5374
	int this_cpu = smp_processor_id();
	bool affine = false;
5375

5376 5377 5378 5379 5380
	/*
	 * Common case: CPUs are in the same socket, and select_idle_sibling()
	 * will do its thing regardless of what we return:
	 */
	if (cpus_share_cache(prev_cpu, this_cpu))
5381 5382 5383
		affine = true;
	else
		affine = numa_wake_affine(sd, p, this_cpu, prev_cpu, sync);
5384

5385
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5386 5387 5388 5389
	if (affine) {
		schedstat_inc(sd->ttwu_move_affine);
		schedstat_inc(p->se.statistics.nr_wakeups_affine);
	}
5390

5391
	return affine;
5392 5393
}

5394 5395 5396 5397 5398 5399 5400 5401
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);
}

5402 5403 5404 5405 5406
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5407
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5408
		  int this_cpu, int sd_flag)
5409
{
5410
	struct sched_group *idlest = NULL, *group = sd->groups;
5411
	struct sched_group *most_spare_sg = NULL;
5412 5413
	unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0;
5414
	unsigned long most_spare = 0, this_spare = 0;
5415
	int load_idx = sd->forkexec_idx;
5416 5417 5418
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5419

5420 5421 5422
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5423
	do {
5424 5425
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5426 5427
		int local_group;
		int i;
5428

5429
		/* Skip over this group if it has no CPUs allowed */
5430
		if (!cpumask_intersects(sched_group_span(group),
5431
					&p->cpus_allowed))
5432 5433 5434
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5435
					       sched_group_span(group));
5436

5437 5438 5439 5440
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5441
		avg_load = 0;
5442
		runnable_load = 0;
5443
		max_spare_cap = 0;
5444

5445
		for_each_cpu(i, sched_group_span(group)) {
5446 5447 5448 5449 5450 5451
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5452 5453 5454
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5455 5456 5457 5458 5459

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5460 5461
		}

5462
		/* Adjust by relative CPU capacity of the group */
5463 5464 5465 5466
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5467 5468

		if (local_group) {
5469 5470
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5471 5472
			this_spare = max_spare_cap;
		} else {
5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487
			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;
5488 5489 5490 5491 5492 5493 5494
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5495 5496 5497
		}
	} while (group = group->next, group != sd->groups);

5498 5499 5500 5501 5502 5503
	/*
	 * 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.
5504 5505 5506 5507
	 *
	 * 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.
5508
	 */
5509 5510 5511
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5512
	if (this_spare > task_util(p) / 2 &&
5513
	    imbalance_scale*this_spare > 100*most_spare)
5514
		return NULL;
5515 5516

	if (most_spare > task_util(p) / 2)
5517 5518
		return most_spare_sg;

5519
skip_spare:
5520 5521 5522 5523
	if (!idlest)
		return NULL;

	if (min_runnable_load > (this_runnable_load + imbalance))
5524
		return NULL;
5525 5526 5527 5528 5529

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

5530 5531 5532 5533 5534 5535 5536 5537 5538 5539
	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;
5540 5541 5542 5543
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5544 5545
	int i;

5546 5547
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5548
		return cpumask_first(sched_group_span(group));
5549

5550
	/* Traverse only the allowed CPUs */
5551
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573
		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;
			}
5574
		} else if (shallowest_idle_cpu == -1) {
5575
			load = weighted_cpuload(cpu_rq(i));
5576 5577 5578 5579
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5580 5581 5582
		}
	}

5583
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5584
}
5585

5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614
#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
5615
void __update_idle_core(struct rq *rq)
5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644
{
	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);
5645
	int core, cpu;
5646

P
Peter Zijlstra 已提交
5647 5648 5649
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5650 5651 5652
	if (!test_idle_cores(target, false))
		return -1;

5653
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
5654

5655
	for_each_cpu_wrap(core, cpus, target) {
5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682
		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
5683 5684 5685
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5686
	for_each_cpu(cpu, cpu_smt_mask(target)) {
5687
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713
			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).
5714
 */
5715 5716
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
5717
	struct sched_domain *this_sd;
5718
	u64 avg_cost, avg_idle;
5719 5720
	u64 time, cost;
	s64 delta;
5721
	int cpu, nr = INT_MAX;
5722

5723 5724 5725 5726
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

5727 5728 5729 5730
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
5731 5732 5733 5734
	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)
5735 5736
		return -1;

5737 5738 5739 5740 5741 5742 5743 5744
	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;
	}

5745 5746
	time = local_clock();

5747
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
5748 5749
		if (!--nr)
			return -1;
5750
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765
			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.
5766
 */
5767
static int select_idle_sibling(struct task_struct *p, int prev, int target)
5768
{
5769
	struct sched_domain *sd;
5770
	int i;
5771

5772 5773
	if (idle_cpu(target))
		return target;
5774 5775

	/*
5776
	 * If the previous cpu is cache affine and idle, don't be stupid.
5777
	 */
5778 5779
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
5780

5781
	sd = rcu_dereference(per_cpu(sd_llc, target));
5782 5783
	if (!sd)
		return target;
5784

5785 5786 5787
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
5788

5789 5790 5791 5792 5793 5794 5795
	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;
5796

5797 5798
	return target;
}
5799

5800
/*
5801
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5802
 * tasks. The unit of the return value must be the one of capacity so we can
5803 5804
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824
 *
 * 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).
5825
 */
5826
static int cpu_util(int cpu)
5827
{
5828
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5829 5830
	unsigned long capacity = capacity_orig_of(cpu);

5831
	return (util >= capacity) ? capacity : util;
5832
}
5833

5834 5835 5836 5837 5838
static inline int task_util(struct task_struct *p)
{
	return p->se.avg.util_avg;
}

5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856
/*
 * 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;
}

5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874
/*
 * 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;

5875 5876 5877
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

5878 5879 5880
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

5881
/*
5882 5883 5884
 * 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.
5885
 *
5886 5887
 * 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.
5888
 *
5889
 * Returns the target cpu number.
5890 5891 5892
 *
 * preempt must be disabled.
 */
5893
static int
5894
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5895
{
5896
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5897
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5898
	int new_cpu = prev_cpu;
5899
	int want_affine = 0;
5900
	int sync = wake_flags & WF_SYNC;
5901

P
Peter Zijlstra 已提交
5902 5903
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
5904
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
5905
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
5906
	}
5907

5908
	rcu_read_lock();
5909
	for_each_domain(cpu, tmp) {
5910
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5911
			break;
5912

5913
		/*
5914 5915
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5916
		 */
5917 5918 5919
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5920
			break;
5921
		}
5922

5923
		if (tmp->flags & sd_flag)
5924
			sd = tmp;
M
Mike Galbraith 已提交
5925 5926
		else if (!want_affine)
			break;
5927 5928
	}

M
Mike Galbraith 已提交
5929 5930
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
5931 5932 5933 5934
		if (cpu == prev_cpu)
			goto pick_cpu;

		if (wake_affine(affine_sd, p, prev_cpu, sync))
M
Mike Galbraith 已提交
5935
			new_cpu = cpu;
5936
	}
5937

M
Mike Galbraith 已提交
5938
	if (!sd) {
5939
 pick_cpu:
M
Mike Galbraith 已提交
5940
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5941
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
5942 5943

	} else while (sd) {
5944
		struct sched_group *group;
5945
		int weight;
5946

5947
		if (!(sd->flags & sd_flag)) {
5948 5949 5950
			sd = sd->child;
			continue;
		}
5951

5952
		group = find_idlest_group(sd, p, cpu, sd_flag);
5953 5954 5955 5956
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5957

5958
		new_cpu = find_idlest_cpu(group, p, cpu);
5959 5960 5961 5962
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5963
		}
5964 5965 5966

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5967
		weight = sd->span_weight;
5968 5969
		sd = NULL;
		for_each_domain(cpu, tmp) {
5970
			if (weight <= tmp->span_weight)
5971
				break;
5972
			if (tmp->flags & sd_flag)
5973 5974 5975
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5976
	}
5977
	rcu_read_unlock();
5978

5979
	return new_cpu;
5980
}
5981 5982 5983 5984

/*
 * 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
5985
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5986
 */
5987
static void migrate_task_rq_fair(struct task_struct *p)
5988
{
5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014
	/*
	 * 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;
	}

6015
	/*
6016 6017 6018 6019 6020
	 * 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.
6021
	 */
6022 6023 6024 6025
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6026 6027

	/* We have migrated, no longer consider this task hot */
6028
	p->se.exec_start = 0;
6029
}
6030 6031 6032 6033 6034

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6035 6036
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
6037 6038
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6039 6040 6041 6042
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6043 6044
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6045 6046 6047 6048 6049 6050 6051 6052 6053
	 *
	 * 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.
6054
	 */
6055
	return calc_delta_fair(gran, se);
6056 6057
}

6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079
/*
 * 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
6080
	gran = wakeup_gran(curr, se);
6081 6082 6083 6084 6085 6086
	if (vdiff > gran)
		return 1;

	return 0;
}

6087 6088
static void set_last_buddy(struct sched_entity *se)
{
6089 6090 6091
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6092 6093 6094
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6095
		cfs_rq_of(se)->last = se;
6096
	}
6097 6098 6099 6100
}

static void set_next_buddy(struct sched_entity *se)
{
6101 6102 6103
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6104 6105 6106
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6107
		cfs_rq_of(se)->next = se;
6108
	}
6109 6110
}

6111 6112
static void set_skip_buddy(struct sched_entity *se)
{
6113 6114
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6115 6116
}

6117 6118 6119
/*
 * Preempt the current task with a newly woken task if needed:
 */
6120
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6121 6122
{
	struct task_struct *curr = rq->curr;
6123
	struct sched_entity *se = &curr->se, *pse = &p->se;
6124
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6125
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6126
	int next_buddy_marked = 0;
6127

I
Ingo Molnar 已提交
6128 6129 6130
	if (unlikely(se == pse))
		return;

6131
	/*
6132
	 * This is possible from callers such as attach_tasks(), in which we
6133 6134 6135 6136 6137 6138 6139
	 * 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;

6140
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6141
		set_next_buddy(pse);
6142 6143
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6144

6145 6146 6147
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6148 6149 6150 6151 6152 6153
	 *
	 * 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.
6154 6155 6156 6157
	 */
	if (test_tsk_need_resched(curr))
		return;

6158 6159 6160 6161 6162
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6163
	/*
6164 6165
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6166
	 */
6167
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6168
		return;
6169

6170
	find_matching_se(&se, &pse);
6171
	update_curr(cfs_rq_of(se));
6172
	BUG_ON(!pse);
6173 6174 6175 6176 6177 6178 6179
	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);
6180
		goto preempt;
6181
	}
6182

6183
	return;
6184

6185
preempt:
6186
	resched_curr(rq);
6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200
	/*
	 * 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);
6201 6202
}

6203
static struct task_struct *
6204
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6205 6206 6207
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6208
	struct task_struct *p;
6209
	int new_tasks;
6210

6211
again:
6212
	if (!cfs_rq->nr_running)
6213
		goto idle;
6214

6215
#ifdef CONFIG_FAIR_GROUP_SCHED
6216
	if (prev->sched_class != &fair_sched_class)
6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232 6233 6234 6235
		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.
		 */
6236 6237 6238 6239 6240
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6241

6242 6243 6244
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6245
			 * Therefore the nr_running test will indeed
6246 6247
			 * be correct.
			 */
6248 6249 6250 6251 6252 6253
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6254
				goto simple;
6255
			}
6256
		}
6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295

		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
6296

6297
	put_prev_task(rq, prev);
6298

6299
	do {
6300
		se = pick_next_entity(cfs_rq, NULL);
6301
		set_next_entity(cfs_rq, se);
6302 6303 6304
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6305
	p = task_of(se);
6306

6307 6308
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6309 6310

	return p;
6311 6312

idle:
6313 6314
	new_tasks = idle_balance(rq, rf);

6315 6316 6317 6318 6319
	/*
	 * 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.
	 */
6320
	if (new_tasks < 0)
6321 6322
		return RETRY_TASK;

6323
	if (new_tasks > 0)
6324 6325 6326
		goto again;

	return NULL;
6327 6328 6329 6330 6331
}

/*
 * Account for a descheduled task:
 */
6332
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6333 6334 6335 6336 6337 6338
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6339
		put_prev_entity(cfs_rq, se);
6340 6341 6342
	}
}

6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367
/*
 * 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);
6368 6369 6370 6371 6372
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6373
		rq_clock_skip_update(rq, true);
6374 6375 6376 6377 6378
	}

	set_skip_buddy(se);
}

6379 6380 6381 6382
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6383 6384
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6385 6386 6387 6388 6389 6390 6391 6392 6393 6394
		return false;

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

	yield_task_fair(rq);

	return true;
}

6395
#ifdef CONFIG_SMP
6396
/**************************************************
P
Peter Zijlstra 已提交
6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412
 * 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
6413
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6414 6415 6416 6417 6418 6419
 *
 * 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)
 *
6420
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
6421 6422 6423 6424 6425 6426
 * 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):
 *
6427
 *   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
6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465
 *
 * 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:
 *
6466
 *             log_2 n
P
Peter Zijlstra 已提交
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 6508 6509 6510 6511
 *   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.]
6512
 */
6513

6514 6515
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6516 6517
enum fbq_type { regular, remote, all };

6518
#define LBF_ALL_PINNED	0x01
6519
#define LBF_NEED_BREAK	0x02
6520 6521
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6522 6523 6524 6525 6526

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6527
	int			src_cpu;
6528 6529 6530 6531

	int			dst_cpu;
	struct rq		*dst_rq;

6532 6533
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6534
	enum cpu_idle_type	idle;
6535
	long			imbalance;
6536 6537 6538
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6539
	unsigned int		flags;
6540 6541 6542 6543

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6544 6545

	enum fbq_type		fbq_type;
6546
	struct list_head	tasks;
6547 6548
};

6549 6550 6551
/*
 * Is this task likely cache-hot:
 */
6552
static int task_hot(struct task_struct *p, struct lb_env *env)
6553 6554 6555
{
	s64 delta;

6556 6557
	lockdep_assert_held(&env->src_rq->lock);

6558 6559 6560 6561 6562 6563 6564 6565 6566
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
6567
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6568 6569 6570 6571 6572 6573 6574 6575 6576
			(&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;

6577
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6578 6579 6580 6581

	return delta < (s64)sysctl_sched_migration_cost;
}

6582
#ifdef CONFIG_NUMA_BALANCING
6583
/*
6584 6585 6586
 * 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.
6587
 */
6588
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6589
{
6590
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6591
	unsigned long src_faults, dst_faults;
6592 6593
	int src_nid, dst_nid;

6594
	if (!static_branch_likely(&sched_numa_balancing))
6595 6596
		return -1;

6597
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6598
		return -1;
6599 6600 6601 6602

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

6603
	if (src_nid == dst_nid)
6604
		return -1;
6605

6606 6607 6608 6609 6610 6611 6612
	/* 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;
	}
6613

6614 6615
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6616
		return 0;
6617

6618 6619 6620 6621
	/* Leaving a core idle is often worse than degrading locality. */
	if (env->idle != CPU_NOT_IDLE)
		return -1;

6622 6623 6624 6625 6626 6627
	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);
6628 6629
	}

6630
	return dst_faults < src_faults;
6631 6632
}

6633
#else
6634
static inline int migrate_degrades_locality(struct task_struct *p,
6635 6636
					     struct lb_env *env)
{
6637
	return -1;
6638
}
6639 6640
#endif

6641 6642 6643 6644
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6645
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6646
{
6647
	int tsk_cache_hot;
6648 6649 6650

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

6651 6652
	/*
	 * We do not migrate tasks that are:
6653
	 * 1) throttled_lb_pair, or
6654
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6655 6656
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6657
	 */
6658 6659 6660
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6661
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
6662
		int cpu;
6663

6664
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
6665

6666 6667
		env->flags |= LBF_SOME_PINNED;

6668 6669 6670 6671 6672
		/*
		 * 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.
		 *
6673 6674
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
6675
		 */
6676
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
6677 6678
			return 0;

6679 6680
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6681
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
6682
				env->flags |= LBF_DST_PINNED;
6683 6684 6685
				env->new_dst_cpu = cpu;
				break;
			}
6686
		}
6687

6688 6689
		return 0;
	}
6690 6691

	/* Record that we found atleast one task that could run on dst_cpu */
6692
	env->flags &= ~LBF_ALL_PINNED;
6693

6694
	if (task_running(env->src_rq, p)) {
6695
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
6696 6697 6698 6699 6700
		return 0;
	}

	/*
	 * Aggressive migration if:
6701 6702 6703
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6704
	 */
6705 6706 6707
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6708

6709
	if (tsk_cache_hot <= 0 ||
6710
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6711
		if (tsk_cache_hot == 1) {
6712 6713
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
6714
		}
6715 6716 6717
		return 1;
	}

6718
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
6719
	return 0;
6720 6721
}

6722
/*
6723 6724 6725 6726 6727 6728 6729
 * 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;
6730
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
6731 6732 6733
	set_task_cpu(p, env->dst_cpu);
}

6734
/*
6735
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6736 6737
 * part of active balancing operations within "domain".
 *
6738
 * Returns a task if successful and NULL otherwise.
6739
 */
6740
static struct task_struct *detach_one_task(struct lb_env *env)
6741 6742 6743
{
	struct task_struct *p, *n;

6744 6745
	lockdep_assert_held(&env->src_rq->lock);

6746 6747 6748
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6749

6750
		detach_task(p, env);
6751

6752
		/*
6753
		 * Right now, this is only the second place where
6754
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6755
		 * so we can safely collect stats here rather than
6756
		 * inside detach_tasks().
6757
		 */
6758
		schedstat_inc(env->sd->lb_gained[env->idle]);
6759
		return p;
6760
	}
6761
	return NULL;
6762 6763
}

6764 6765
static const unsigned int sched_nr_migrate_break = 32;

6766
/*
6767 6768
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6769
 *
6770
 * Returns number of detached tasks if successful and 0 otherwise.
6771
 */
6772
static int detach_tasks(struct lb_env *env)
6773
{
6774 6775
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6776
	unsigned long load;
6777 6778 6779
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6780

6781
	if (env->imbalance <= 0)
6782
		return 0;
6783

6784
	while (!list_empty(tasks)) {
6785 6786 6787 6788 6789 6790 6791
		/*
		 * 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;

6792
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6793

6794 6795
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6796
		if (env->loop > env->loop_max)
6797
			break;
6798 6799

		/* take a breather every nr_migrate tasks */
6800
		if (env->loop > env->loop_break) {
6801
			env->loop_break += sched_nr_migrate_break;
6802
			env->flags |= LBF_NEED_BREAK;
6803
			break;
6804
		}
6805

6806
		if (!can_migrate_task(p, env))
6807 6808 6809
			goto next;

		load = task_h_load(p);
6810

6811
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6812 6813
			goto next;

6814
		if ((load / 2) > env->imbalance)
6815
			goto next;
6816

6817 6818 6819 6820
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6821
		env->imbalance -= load;
6822 6823

#ifdef CONFIG_PREEMPT
6824 6825
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6826
		 * kernels will stop after the first task is detached to minimize
6827 6828
		 * the critical section.
		 */
6829
		if (env->idle == CPU_NEWLY_IDLE)
6830
			break;
6831 6832
#endif

6833 6834 6835 6836
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6837
		if (env->imbalance <= 0)
6838
			break;
6839 6840 6841

		continue;
next:
6842
		list_move_tail(&p->se.group_node, tasks);
6843
	}
6844

6845
	/*
6846 6847 6848
	 * 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().
6849
	 */
6850
	schedstat_add(env->sd->lb_gained[env->idle], detached);
6851

6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862
	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);
6863
	activate_task(rq, p, ENQUEUE_NOCLOCK);
6864
	p->on_rq = TASK_ON_RQ_QUEUED;
6865 6866 6867 6868 6869 6870 6871 6872 6873
	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)
{
6874 6875 6876
	struct rq_flags rf;

	rq_lock(rq, &rf);
6877
	update_rq_clock(rq);
6878
	attach_task(rq, p);
6879
	rq_unlock(rq, &rf);
6880 6881 6882 6883 6884 6885 6886 6887 6888 6889
}

/*
 * 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;
6890
	struct rq_flags rf;
6891

6892
	rq_lock(env->dst_rq, &rf);
6893
	update_rq_clock(env->dst_rq);
6894 6895 6896 6897

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
6898

6899 6900 6901
		attach_task(env->dst_rq, p);
	}

6902
	rq_unlock(env->dst_rq, &rf);
6903 6904
}

P
Peter Zijlstra 已提交
6905
#ifdef CONFIG_FAIR_GROUP_SCHED
6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923

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;
}

6924
static void update_blocked_averages(int cpu)
6925 6926
{
	struct rq *rq = cpu_rq(cpu);
6927
	struct cfs_rq *cfs_rq, *pos;
6928
	struct rq_flags rf;
6929

6930
	rq_lock_irqsave(rq, &rf);
6931
	update_rq_clock(rq);
6932

6933 6934 6935 6936
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6937
	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
6938 6939
		struct sched_entity *se;

6940 6941 6942
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6943

6944
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6945
			update_tg_load_avg(cfs_rq, 0);
6946

6947 6948 6949 6950
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
			update_load_avg(se, 0);
6951 6952 6953 6954 6955 6956 6957

		/*
		 * 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);
6958
	}
6959
	rq_unlock_irqrestore(rq, &rf);
6960 6961
}

6962
/*
6963
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6964 6965 6966
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6967
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6968
{
6969 6970
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6971
	unsigned long now = jiffies;
6972
	unsigned long load;
6973

6974
	if (cfs_rq->last_h_load_update == now)
6975 6976
		return;

6977 6978 6979 6980 6981 6982 6983
	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;
	}
6984

6985
	if (!se) {
6986
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6987 6988 6989 6990 6991
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6992 6993
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6994 6995 6996 6997
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6998 6999
}

7000
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7001
{
7002
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7003

7004
	update_cfs_rq_h_load(cfs_rq);
7005
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7006
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7007 7008
}
#else
7009
static inline void update_blocked_averages(int cpu)
7010
{
7011 7012
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7013
	struct rq_flags rf;
7014

7015
	rq_lock_irqsave(rq, &rf);
7016
	update_rq_clock(rq);
7017
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7018
	rq_unlock_irqrestore(rq, &rf);
7019 7020
}

7021
static unsigned long task_h_load(struct task_struct *p)
7022
{
7023
	return p->se.avg.load_avg;
7024
}
P
Peter Zijlstra 已提交
7025
#endif
7026 7027

/********** Helpers for find_busiest_group ************************/
7028 7029 7030 7031 7032 7033 7034

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

7035 7036 7037 7038 7039 7040 7041
/*
 * 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
7042
	unsigned long load_per_task;
7043
	unsigned long group_capacity;
7044
	unsigned long group_util; /* Total utilization of the group */
7045 7046 7047
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7048
	enum group_type group_type;
7049
	int group_no_capacity;
7050 7051 7052 7053
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7054 7055
};

J
Joonsoo Kim 已提交
7056 7057 7058 7059 7060 7061 7062 7063
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *		 during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest;	/* Busiest group in this sd */
	struct sched_group *local;	/* Local group in this sd */
	unsigned long total_load;	/* Total load of all groups in sd */
7064
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7065 7066 7067
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7068
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7069 7070
};

7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
	/*
	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
	 * We must however clear busiest_stat::avg_load because
	 * update_sd_pick_busiest() reads this before assignment.
	 */
	*sds = (struct sd_lb_stats){
		.busiest = NULL,
		.local = NULL,
		.total_load = 0UL,
7083
		.total_capacity = 0UL,
7084 7085
		.busiest_stat = {
			.avg_load = 0UL,
7086 7087
			.sum_nr_running = 0,
			.group_type = group_other,
7088 7089 7090 7091
		},
	};
}

7092 7093 7094
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7095
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7096 7097
 *
 * Return: The load index.
7098 7099 7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119
 */
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;
}

7120
static unsigned long scale_rt_capacity(int cpu)
7121 7122
{
	struct rq *rq = cpu_rq(cpu);
7123
	u64 total, used, age_stamp, avg;
7124
	s64 delta;
7125

7126 7127 7128 7129
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
7130 7131
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
7132
	delta = __rq_clock_broken(rq) - age_stamp;
7133

7134 7135 7136 7137
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
7138

7139
	used = div_u64(avg, total);
7140

7141 7142
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
7143

7144
	return 1;
7145 7146
}

7147
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7148
{
7149
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7150 7151
	struct sched_group *sdg = sd->groups;

7152
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7153

7154
	capacity *= scale_rt_capacity(cpu);
7155
	capacity >>= SCHED_CAPACITY_SHIFT;
7156

7157 7158
	if (!capacity)
		capacity = 1;
7159

7160 7161
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7162
	sdg->sgc->min_capacity = capacity;
7163 7164
}

7165
void update_group_capacity(struct sched_domain *sd, int cpu)
7166 7167 7168
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7169
	unsigned long capacity, min_capacity;
7170 7171 7172 7173
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7174
	sdg->sgc->next_update = jiffies + interval;
7175 7176

	if (!child) {
7177
		update_cpu_capacity(sd, cpu);
7178 7179 7180
		return;
	}

7181
	capacity = 0;
7182
	min_capacity = ULONG_MAX;
7183

P
Peter Zijlstra 已提交
7184 7185 7186 7187 7188 7189
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7190
		for_each_cpu(cpu, sched_group_span(sdg)) {
7191
			struct sched_group_capacity *sgc;
7192
			struct rq *rq = cpu_rq(cpu);
7193

7194
			/*
7195
			 * build_sched_domains() -> init_sched_groups_capacity()
7196 7197 7198
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7199 7200
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7201
			 *
7202
			 * This avoids capacity from being 0 and
7203 7204 7205
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7206
				capacity += capacity_of(cpu);
7207 7208 7209
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7210
			}
7211

7212
			min_capacity = min(capacity, min_capacity);
7213
		}
P
Peter Zijlstra 已提交
7214 7215 7216 7217
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7218
		 */
P
Peter Zijlstra 已提交
7219 7220 7221

		group = child->groups;
		do {
7222 7223 7224 7225
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7226 7227 7228
			group = group->next;
		} while (group != child->groups);
	}
7229

7230
	sdg->sgc->capacity = capacity;
7231
	sdg->sgc->min_capacity = min_capacity;
7232 7233
}

7234
/*
7235 7236 7237
 * 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
7238 7239
 */
static inline int
7240
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7241
{
7242 7243
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7244 7245
}

7246 7247
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7248
 * groups is inadequate due to ->cpus_allowed constraints.
7249 7250 7251 7252 7253
 *
 * 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:
 *
7254 7255
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7256 7257 7258 7259 7260 7261
 *
 * 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
7262 7263
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7264 7265
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7266
 * update_sd_pick_busiest(). And calculate_imbalance() and
7267
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7268 7269 7270 7271 7272 7273 7274
 * 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.
 */

7275
static inline int sg_imbalanced(struct sched_group *group)
7276
{
7277
	return group->sgc->imbalance;
7278 7279
}

7280
/*
7281 7282 7283
 * 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
7284 7285
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7286 7287 7288 7289 7290
 * 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.
7291
 */
7292 7293
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7294
{
7295 7296
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7297

7298
	if ((sgs->group_capacity * 100) >
7299
			(sgs->group_util * env->sd->imbalance_pct))
7300
		return true;
7301

7302 7303 7304 7305 7306 7307 7308 7309 7310 7311 7312 7313 7314 7315 7316 7317
	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;
7318

7319
	if ((sgs->group_capacity * 100) <
7320
			(sgs->group_util * env->sd->imbalance_pct))
7321
		return true;
7322

7323
	return false;
7324 7325
}

7326 7327 7328 7329 7330 7331 7332 7333 7334 7335 7336
/*
 * 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;
}

7337 7338 7339
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7340
{
7341
	if (sgs->group_no_capacity)
7342 7343 7344 7345 7346 7347 7348 7349
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7350 7351
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7352
 * @env: The load balancing environment.
7353 7354 7355 7356
 * @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.
7357
 * @overload: Indicate more than one runnable task for any CPU.
7358
 */
7359 7360
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7361 7362
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7363
{
7364
	unsigned long load;
7365
	int i, nr_running;
7366

7367 7368
	memset(sgs, 0, sizeof(*sgs));

7369
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7370 7371 7372
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
7373
		if (local_group)
7374
			load = target_load(i, load_idx);
7375
		else
7376 7377 7378
			load = source_load(i, load_idx);

		sgs->group_load += load;
7379
		sgs->group_util += cpu_util(i);
7380
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7381

7382 7383
		nr_running = rq->nr_running;
		if (nr_running > 1)
7384 7385
			*overload = true;

7386 7387 7388 7389
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7390
		sgs->sum_weighted_load += weighted_cpuload(rq);
7391 7392 7393 7394
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7395
			sgs->idle_cpus++;
7396 7397
	}

7398 7399
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7400
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7401

7402
	if (sgs->sum_nr_running)
7403
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7404

7405
	sgs->group_weight = group->group_weight;
7406

7407
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7408
	sgs->group_type = group_classify(group, sgs);
7409 7410
}

7411 7412
/**
 * update_sd_pick_busiest - return 1 on busiest group
7413
 * @env: The load balancing environment.
7414 7415
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7416
 * @sgs: sched_group statistics
7417 7418 7419
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7420 7421 7422
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7423
 */
7424
static bool update_sd_pick_busiest(struct lb_env *env,
7425 7426
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7427
				   struct sg_lb_stats *sgs)
7428
{
7429
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7430

7431
	if (sgs->group_type > busiest->group_type)
7432 7433
		return true;

7434 7435 7436 7437 7438 7439
	if (sgs->group_type < busiest->group_type)
		return false;

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

7440 7441 7442 7443 7444 7445 7446 7447 7448 7449 7450 7451 7452 7453
	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:
7454 7455
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7456 7457
		return true;

7458 7459 7460
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
7461
	/*
T
Tim Chen 已提交
7462 7463 7464
	 * 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.
7465
	 */
T
Tim Chen 已提交
7466 7467
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7468 7469 7470
		if (!sds->busiest)
			return true;

T
Tim Chen 已提交
7471 7472 7473
		/* Prefer to move from lowest priority cpu's work */
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7474 7475 7476 7477 7478 7479
			return true;
	}

	return false;
}

7480 7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506 7507 7508 7509
#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 */

7510
/**
7511
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7512
 * @env: The load balancing environment.
7513 7514
 * @sds: variable to hold the statistics for this sched_domain.
 */
7515
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7516
{
7517 7518
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7519
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7520
	struct sg_lb_stats tmp_sgs;
7521
	int load_idx, prefer_sibling = 0;
7522
	bool overload = false;
7523 7524 7525 7526

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

7527
	load_idx = get_sd_load_idx(env->sd, env->idle);
7528 7529

	do {
J
Joonsoo Kim 已提交
7530
		struct sg_lb_stats *sgs = &tmp_sgs;
7531 7532
		int local_group;

7533
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7534 7535
		if (local_group) {
			sds->local = sg;
7536
			sgs = local;
7537 7538

			if (env->idle != CPU_NEWLY_IDLE ||
7539 7540
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7541
		}
7542

7543 7544
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7545

7546 7547 7548
		if (local_group)
			goto next_group;

7549 7550
		/*
		 * In case the child domain prefers tasks go to siblings
7551
		 * first, lower the sg capacity so that we'll try
7552 7553
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7554 7555 7556 7557
		 * 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).
7558
		 */
7559
		if (prefer_sibling && sds->local &&
7560 7561
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7562
			sgs->group_no_capacity = 1;
7563
			sgs->group_type = group_classify(sg, sgs);
7564
		}
7565

7566
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7567
			sds->busiest = sg;
J
Joonsoo Kim 已提交
7568
			sds->busiest_stat = *sgs;
7569 7570
		}

7571 7572 7573
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
7574
		sds->total_capacity += sgs->group_capacity;
7575

7576
		sg = sg->next;
7577
	} while (sg != env->sd->groups);
7578 7579 7580

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7581 7582 7583 7584 7585 7586 7587

	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;
	}

7588 7589 7590 7591
}

/**
 * check_asym_packing - Check to see if the group is packed into the
7592
 *			sched domain.
7593 7594 7595 7596 7597 7598 7599 7600 7601 7602 7603 7604 7605 7606
 *
 * 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.
 *
7607
 * Return: 1 when packing is required and a task should be moved to
7608 7609
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
7610
 * @env: The load balancing environment.
7611 7612
 * @sds: Statistics of the sched_domain which is to be packed
 */
7613
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7614 7615 7616
{
	int busiest_cpu;

7617
	if (!(env->sd->flags & SD_ASYM_PACKING))
7618 7619
		return 0;

7620 7621 7622
	if (env->idle == CPU_NOT_IDLE)
		return 0;

7623 7624 7625
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
7626 7627
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
7628 7629
		return 0;

7630
	env->imbalance = DIV_ROUND_CLOSEST(
7631
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7632
		SCHED_CAPACITY_SCALE);
7633

7634
	return 1;
7635 7636 7637 7638 7639 7640
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
7641
 * @env: The load balancing environment.
7642 7643
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
7644 7645
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7646
{
7647
	unsigned long tmp, capa_now = 0, capa_move = 0;
7648
	unsigned int imbn = 2;
7649
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
7650
	struct sg_lb_stats *local, *busiest;
7651

J
Joonsoo Kim 已提交
7652 7653
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7654

J
Joonsoo Kim 已提交
7655 7656 7657 7658
	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;
7659

J
Joonsoo Kim 已提交
7660
	scaled_busy_load_per_task =
7661
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7662
		busiest->group_capacity;
J
Joonsoo Kim 已提交
7663

7664 7665
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
7666
		env->imbalance = busiest->load_per_task;
7667 7668 7669 7670 7671
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
7672
	 * however we may be able to increase total CPU capacity used by
7673 7674 7675
	 * moving them.
	 */

7676
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
7677
			min(busiest->load_per_task, busiest->avg_load);
7678
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
7679
			min(local->load_per_task, local->avg_load);
7680
	capa_now /= SCHED_CAPACITY_SCALE;
7681 7682

	/* Amount of load we'd subtract */
7683
	if (busiest->avg_load > scaled_busy_load_per_task) {
7684
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
7685
			    min(busiest->load_per_task,
7686
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
7687
	}
7688 7689

	/* Amount of load we'd add */
7690
	if (busiest->avg_load * busiest->group_capacity <
7691
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7692 7693
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
7694
	} else {
7695
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7696
		      local->group_capacity;
J
Joonsoo Kim 已提交
7697
	}
7698
	capa_move += local->group_capacity *
7699
		    min(local->load_per_task, local->avg_load + tmp);
7700
	capa_move /= SCHED_CAPACITY_SCALE;
7701 7702

	/* Move if we gain throughput */
7703
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
7704
		env->imbalance = busiest->load_per_task;
7705 7706 7707 7708 7709
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
7710
 * @env: load balance environment
7711 7712
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
7713
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7714
{
7715
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
7716 7717 7718 7719
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7720

7721
	if (busiest->group_type == group_imbalanced) {
7722 7723 7724 7725
		/*
		 * 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
7726 7727
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
7728 7729
	}

7730
	/*
7731 7732 7733 7734
	 * 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:
7735
	 */
7736 7737
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7738 7739
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7740 7741
	}

7742 7743 7744 7745 7746
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7747
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7748
		if (load_above_capacity > busiest->group_capacity) {
7749
			load_above_capacity -= busiest->group_capacity;
7750
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
7751 7752
			load_above_capacity /= busiest->group_capacity;
		} else
7753
			load_above_capacity = ~0UL;
7754 7755 7756 7757 7758 7759
	}

	/*
	 * 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,
7760 7761
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
7762
	 */
7763
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7764 7765

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7766
	env->imbalance = min(
7767 7768
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
7769
	) / SCHED_CAPACITY_SCALE;
7770 7771 7772

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
7773
	 * there is no guarantee that any tasks will be moved so we'll have
7774 7775 7776
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7777
	if (env->imbalance < busiest->load_per_task)
7778
		return fix_small_imbalance(env, sds);
7779
}
7780

7781 7782 7783 7784
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
7785
 * if there is an imbalance.
7786 7787 7788 7789
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
7790
 * @env: The load balancing environment.
7791
 *
7792
 * Return:	- The busiest group if imbalance exists.
7793
 */
J
Joonsoo Kim 已提交
7794
static struct sched_group *find_busiest_group(struct lb_env *env)
7795
{
J
Joonsoo Kim 已提交
7796
	struct sg_lb_stats *local, *busiest;
7797 7798
	struct sd_lb_stats sds;

7799
	init_sd_lb_stats(&sds);
7800 7801 7802 7803 7804

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7805
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7806 7807
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7808

7809
	/* ASYM feature bypasses nice load balance check */
7810
	if (check_asym_packing(env, &sds))
7811 7812
		return sds.busiest;

7813
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7814
	if (!sds.busiest || busiest->sum_nr_running == 0)
7815 7816
		goto out_balanced;

7817 7818
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7819

P
Peter Zijlstra 已提交
7820 7821
	/*
	 * If the busiest group is imbalanced the below checks don't
7822
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7823 7824
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7825
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7826 7827
		goto force_balance;

7828
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7829 7830
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7831 7832
		goto force_balance;

7833
	/*
7834
	 * If the local group is busier than the selected busiest group
7835 7836
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7837
	if (local->avg_load >= busiest->avg_load)
7838 7839
		goto out_balanced;

7840 7841 7842 7843
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7844
	if (local->avg_load >= sds.avg_load)
7845 7846
		goto out_balanced;

7847
	if (env->idle == CPU_IDLE) {
7848
		/*
7849 7850 7851 7852 7853
		 * 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
7854
		 */
7855 7856
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7857
			goto out_balanced;
7858 7859 7860 7861 7862
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7863 7864
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7865
			goto out_balanced;
7866
	}
7867

7868
force_balance:
7869
	/* Looks like there is an imbalance. Compute it */
7870
	calculate_imbalance(env, &sds);
7871 7872 7873
	return sds.busiest;

out_balanced:
7874
	env->imbalance = 0;
7875 7876 7877 7878 7879 7880
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7881
static struct rq *find_busiest_queue(struct lb_env *env,
7882
				     struct sched_group *group)
7883 7884
{
	struct rq *busiest = NULL, *rq;
7885
	unsigned long busiest_load = 0, busiest_capacity = 1;
7886 7887
	int i;

7888
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7889
		unsigned long capacity, wl;
7890 7891 7892 7893
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7894

7895 7896 7897 7898 7899 7900 7901 7902 7903 7904 7905 7906 7907 7908 7909 7910 7911 7912 7913 7914 7915 7916
		/*
		 * 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;

7917
		capacity = capacity_of(i);
7918

7919
		wl = weighted_cpuload(rq);
7920

7921 7922
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7923
		 * which is not scaled with the cpu capacity.
7924
		 */
7925 7926 7927

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7928 7929
			continue;

7930 7931
		/*
		 * For the load comparisons with the other cpu's, consider
7932 7933 7934
		 * 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.
7935
		 *
7936
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7937
		 * multiplication to rid ourselves of the division works out
7938 7939
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7940
		 */
7941
		if (wl * busiest_capacity > busiest_load * capacity) {
7942
			busiest_load = wl;
7943
			busiest_capacity = capacity;
7944 7945 7946 7947 7948 7949 7950 7951 7952 7953 7954 7955 7956
			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

7957
static int need_active_balance(struct lb_env *env)
7958
{
7959 7960 7961
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
7962 7963 7964

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
7965 7966
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
7967
		 */
T
Tim Chen 已提交
7968 7969
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
7970
			return 1;
7971 7972
	}

7973 7974 7975 7976 7977 7978 7979 7980 7981 7982 7983 7984 7985
	/*
	 * 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;
	}

7986 7987 7988
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7989 7990
static int active_load_balance_cpu_stop(void *data);

7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003
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 */
8004
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8005
		if (!idle_cpu(cpu))
8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018
			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.
	 */
8019
	return balance_cpu == env->dst_cpu;
8020 8021
}

8022 8023 8024 8025 8026 8027
/*
 * 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,
8028
			int *continue_balancing)
8029
{
8030
	int ld_moved, cur_ld_moved, active_balance = 0;
8031
	struct sched_domain *sd_parent = sd->parent;
8032 8033
	struct sched_group *group;
	struct rq *busiest;
8034
	struct rq_flags rf;
8035
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8036

8037 8038
	struct lb_env env = {
		.sd		= sd,
8039 8040
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8041
		.dst_grpmask    = sched_group_span(sd->groups),
8042
		.idle		= idle,
8043
		.loop_break	= sched_nr_migrate_break,
8044
		.cpus		= cpus,
8045
		.fbq_type	= all,
8046
		.tasks		= LIST_HEAD_INIT(env.tasks),
8047 8048
	};

8049
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8050

8051
	schedstat_inc(sd->lb_count[idle]);
8052 8053

redo:
8054 8055
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8056
		goto out_balanced;
8057
	}
8058

8059
	group = find_busiest_group(&env);
8060
	if (!group) {
8061
		schedstat_inc(sd->lb_nobusyg[idle]);
8062 8063 8064
		goto out_balanced;
	}

8065
	busiest = find_busiest_queue(&env, group);
8066
	if (!busiest) {
8067
		schedstat_inc(sd->lb_nobusyq[idle]);
8068 8069 8070
		goto out_balanced;
	}

8071
	BUG_ON(busiest == env.dst_rq);
8072

8073
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8074

8075 8076 8077
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8078 8079 8080 8081 8082 8083 8084 8085
	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.
		 */
8086
		env.flags |= LBF_ALL_PINNED;
8087
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8088

8089
more_balance:
8090
		rq_lock_irqsave(busiest, &rf);
8091
		update_rq_clock(busiest);
8092 8093 8094 8095 8096

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8097
		cur_ld_moved = detach_tasks(&env);
8098 8099

		/*
8100 8101 8102 8103 8104
		 * 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.
8105
		 */
8106

8107
		rq_unlock(busiest, &rf);
8108 8109 8110 8111 8112 8113

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8114
		local_irq_restore(rf.flags);
8115

8116 8117 8118 8119 8120
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139
		/*
		 * 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.
		 */
8140
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8141

8142 8143 8144
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8145
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8146
			env.dst_cpu	 = env.new_dst_cpu;
8147
			env.flags	&= ~LBF_DST_PINNED;
8148 8149
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8150

8151 8152 8153 8154 8155 8156
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8157

8158 8159 8160 8161
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8162
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8163

8164
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8165 8166 8167
				*group_imbalance = 1;
		}

8168
		/* All tasks on this runqueue were pinned by CPU affinity */
8169
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8170
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8171 8172 8173 8174 8175 8176 8177 8178 8179
			/*
			 * 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)) {
8180 8181
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8182
				goto redo;
8183
			}
8184
			goto out_all_pinned;
8185 8186 8187 8188
		}
	}

	if (!ld_moved) {
8189
		schedstat_inc(sd->lb_failed[idle]);
8190 8191 8192 8193 8194 8195 8196 8197
		/*
		 * 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++;
8198

8199
		if (need_active_balance(&env)) {
8200 8201
			unsigned long flags;

8202 8203
			raw_spin_lock_irqsave(&busiest->lock, flags);

8204 8205 8206
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
8207
			 */
8208
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8209 8210
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8211
				env.flags |= LBF_ALL_PINNED;
8212 8213 8214
				goto out_one_pinned;
			}

8215 8216 8217 8218 8219
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8220 8221 8222 8223 8224 8225
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8226

8227
			if (active_balance) {
8228 8229 8230
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8231
			}
8232

8233
			/* We've kicked active balancing, force task migration. */
8234 8235 8236 8237 8238 8239 8240 8241 8242 8243 8244 8245 8246
			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
8247
		 * detach_tasks).
8248 8249 8250 8251 8252 8253 8254 8255
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8256 8257 8258 8259 8260 8261 8262 8263 8264 8265 8266 8267 8268 8269 8270 8271 8272
	/*
	 * 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.
	 */
8273
	schedstat_inc(sd->lb_balanced[idle]);
8274 8275 8276 8277 8278

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8279
	if (((env.flags & LBF_ALL_PINNED) &&
8280
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8281 8282 8283
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8284
	ld_moved = 0;
8285 8286 8287 8288
out:
	return ld_moved;
}

8289 8290 8291 8292 8293 8294 8295 8296 8297 8298 8299 8300 8301 8302 8303 8304
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
8305
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8306 8307 8308
{
	unsigned long interval, next;

8309 8310
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8311 8312 8313 8314 8315 8316
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8317 8318 8319 8320
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
8321
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
8322
{
8323 8324
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
8325 8326
	struct sched_domain *sd;
	int pulled_task = 0;
8327
	u64 curr_cost = 0;
8328

8329 8330 8331 8332 8333 8334
	/*
	 * 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);

8335 8336 8337 8338 8339 8340 8341 8342
	/*
	 * 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);

8343 8344
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
8345 8346 8347
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
8348
			update_next_balance(sd, &next_balance);
8349 8350
		rcu_read_unlock();

8351
		goto out;
8352
	}
8353

8354 8355
	raw_spin_unlock(&this_rq->lock);

8356
	update_blocked_averages(this_cpu);
8357
	rcu_read_lock();
8358
	for_each_domain(this_cpu, sd) {
8359
		int continue_balancing = 1;
8360
		u64 t0, domain_cost;
8361 8362 8363 8364

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8365
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8366
			update_next_balance(sd, &next_balance);
8367
			break;
8368
		}
8369

8370
		if (sd->flags & SD_BALANCE_NEWIDLE) {
8371 8372
			t0 = sched_clock_cpu(this_cpu);

8373
			pulled_task = load_balance(this_cpu, this_rq,
8374 8375
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
8376 8377 8378 8379 8380 8381

			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;
8382
		}
8383

8384
		update_next_balance(sd, &next_balance);
8385 8386 8387 8388 8389 8390

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
8391 8392
			break;
	}
8393
	rcu_read_unlock();
8394 8395 8396

	raw_spin_lock(&this_rq->lock);

8397 8398 8399
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

8400
	/*
8401 8402 8403
	 * 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.
8404
	 */
8405
	if (this_rq->cfs.h_nr_running && !pulled_task)
8406
		pulled_task = 1;
8407

8408 8409 8410
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
8411
		this_rq->next_balance = next_balance;
8412

8413
	/* Is there a task of a high priority class? */
8414
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8415 8416
		pulled_task = -1;

8417
	if (pulled_task)
8418 8419
		this_rq->idle_stamp = 0;

8420 8421
	rq_repin_lock(this_rq, rf);

8422
	return pulled_task;
8423 8424 8425
}

/*
8426 8427 8428 8429
 * 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.
8430
 */
8431
static int active_load_balance_cpu_stop(void *data)
8432
{
8433 8434
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8435
	int target_cpu = busiest_rq->push_cpu;
8436
	struct rq *target_rq = cpu_rq(target_cpu);
8437
	struct sched_domain *sd;
8438
	struct task_struct *p = NULL;
8439
	struct rq_flags rf;
8440

8441
	rq_lock_irq(busiest_rq, &rf);
8442 8443 8444 8445 8446

	/* 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;
8447 8448 8449

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8450
		goto out_unlock;
8451 8452 8453 8454 8455 8456 8457 8458 8459

	/*
	 * 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. */
8460
	rcu_read_lock();
8461 8462 8463 8464 8465 8466 8467
	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)) {
8468 8469
		struct lb_env env = {
			.sd		= sd,
8470 8471 8472 8473
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8474
			.idle		= CPU_IDLE,
8475 8476 8477 8478 8479 8480 8481
			/*
			 * 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,
8482 8483
		};

8484
		schedstat_inc(sd->alb_count);
8485
		update_rq_clock(busiest_rq);
8486

8487
		p = detach_one_task(&env);
8488
		if (p) {
8489
			schedstat_inc(sd->alb_pushed);
8490 8491 8492
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8493
			schedstat_inc(sd->alb_failed);
8494
		}
8495
	}
8496
	rcu_read_unlock();
8497 8498
out_unlock:
	busiest_rq->active_balance = 0;
8499
	rq_unlock(busiest_rq, &rf);
8500 8501 8502 8503 8504 8505

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8506
	return 0;
8507 8508
}

8509 8510 8511 8512 8513
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8514
#ifdef CONFIG_NO_HZ_COMMON
8515 8516 8517 8518 8519 8520
/*
 * 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.
 */
8521
static struct {
8522
	cpumask_var_t idle_cpus_mask;
8523
	atomic_t nr_cpus;
8524 8525
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
8526

8527
static inline int find_new_ilb(void)
8528
{
8529
	int ilb = cpumask_first(nohz.idle_cpus_mask);
8530

8531 8532 8533 8534
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
8535 8536
}

8537 8538 8539 8540 8541
/*
 * 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).
 */
8542
static void nohz_balancer_kick(void)
8543 8544 8545 8546 8547
{
	int ilb_cpu;

	nohz.next_balance++;

8548
	ilb_cpu = find_new_ilb();
8549

8550 8551
	if (ilb_cpu >= nr_cpu_ids)
		return;
8552

8553
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8554 8555 8556 8557 8558 8559 8560 8561
		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);
8562 8563 8564
	return;
}

8565
void nohz_balance_exit_idle(unsigned int cpu)
8566 8567
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8568 8569 8570 8571 8572 8573 8574
		/*
		 * 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);
		}
8575 8576 8577 8578
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

8579 8580 8581
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
8582
	int cpu = smp_processor_id();
8583 8584

	rcu_read_lock();
8585
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8586 8587 8588 8589 8590

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

8591
	atomic_inc(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8592
unlock:
8593 8594 8595 8596 8597 8598
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
8599
	int cpu = smp_processor_id();
8600 8601

	rcu_read_lock();
8602
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
8603 8604 8605 8606 8607

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

8608
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
8609
unlock:
8610 8611 8612
	rcu_read_unlock();
}

8613
/*
8614
 * This routine will record that the cpu is going idle with tick stopped.
8615
 * This info will be used in performing idle load balancing in the future.
8616
 */
8617
void nohz_balance_enter_idle(int cpu)
8618
{
8619 8620 8621 8622 8623 8624
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

8625 8626 8627 8628
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
	if (!is_housekeeping_cpu(cpu))
		return;

8629 8630
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
8631

8632 8633 8634 8635 8636 8637
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

8638 8639 8640
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8641 8642 8643 8644 8645
}
#endif

static DEFINE_SPINLOCK(balancing);

8646 8647 8648 8649
/*
 * 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.
 */
8650
void update_max_interval(void)
8651 8652 8653 8654
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

8655 8656 8657 8658
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
8659
 * Balancing parameters are set up in init_sched_domains.
8660
 */
8661
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8662
{
8663
	int continue_balancing = 1;
8664
	int cpu = rq->cpu;
8665
	unsigned long interval;
8666
	struct sched_domain *sd;
8667 8668 8669
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8670 8671
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
8672

8673
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
8674

8675
	rcu_read_lock();
8676
	for_each_domain(cpu, sd) {
8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687 8688
		/*
		 * 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;

8689 8690 8691
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8692 8693 8694 8695 8696 8697 8698 8699 8700 8701 8702
		/*
		 * 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;
		}

8703
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8704 8705 8706 8707 8708 8709 8710 8711

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8712
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8713
				/*
8714
				 * The LBF_DST_PINNED logic could have changed
8715 8716
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
8717
				 */
8718
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8719 8720
			}
			sd->last_balance = jiffies;
8721
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8722 8723 8724 8725 8726 8727 8728 8729
		}
		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;
		}
8730 8731
	}
	if (need_decay) {
8732
		/*
8733 8734
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
8735
		 */
8736 8737
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
8738
	}
8739
	rcu_read_unlock();
8740 8741 8742 8743 8744 8745

	/*
	 * 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.
	 */
8746
	if (likely(update_next_balance)) {
8747
		rq->next_balance = next_balance;
8748 8749 8750 8751 8752 8753 8754 8755 8756 8757 8758 8759 8760 8761

#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
	}
8762 8763
}

8764
#ifdef CONFIG_NO_HZ_COMMON
8765
/*
8766
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8767 8768
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
8769
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8770
{
8771
	int this_cpu = this_rq->cpu;
8772 8773
	struct rq *rq;
	int balance_cpu;
8774 8775 8776
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8777

8778 8779 8780
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8781 8782

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8783
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8784 8785 8786 8787 8788 8789 8790
			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.
		 */
8791
		if (need_resched())
8792 8793
			break;

V
Vincent Guittot 已提交
8794 8795
		rq = cpu_rq(balance_cpu);

8796 8797 8798 8799 8800
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
8801 8802 8803
			struct rq_flags rf;

			rq_lock_irq(rq, &rf);
8804
			update_rq_clock(rq);
8805
			cpu_load_update_idle(rq);
8806 8807
			rq_unlock_irq(rq, &rf);

8808 8809
			rebalance_domains(rq, CPU_IDLE);
		}
8810

8811 8812 8813 8814
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8815
	}
8816 8817 8818 8819 8820 8821 8822 8823

	/*
	 * 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;
8824 8825
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8826 8827 8828
}

/*
8829
 * Current heuristic for kicking the idle load balancer in the presence
8830
 * of an idle cpu in the system.
8831
 *   - This rq has more than one task.
8832 8833 8834 8835
 *   - 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.
8836 8837
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8838
 */
8839
static inline bool nohz_kick_needed(struct rq *rq)
8840 8841
{
	unsigned long now = jiffies;
8842
	struct sched_domain_shared *sds;
8843
	struct sched_domain *sd;
T
Tim Chen 已提交
8844
	int nr_busy, i, cpu = rq->cpu;
8845
	bool kick = false;
8846

8847
	if (unlikely(rq->idle_balance))
8848
		return false;
8849

8850 8851 8852 8853
       /*
	* 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.
	*/
8854
	set_cpu_sd_state_busy();
8855
	nohz_balance_exit_idle(cpu);
8856 8857 8858 8859 8860 8861

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8862
		return false;
8863 8864

	if (time_before(now, nohz.next_balance))
8865
		return false;
8866

8867
	if (rq->nr_running >= 2)
8868
		return true;
8869

8870
	rcu_read_lock();
8871 8872 8873 8874 8875 8876 8877
	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);
8878 8879 8880 8881 8882
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8883
	}
8884

8885 8886 8887 8888 8889 8890 8891 8892
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8893

8894
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
T
Tim Chen 已提交
8895 8896 8897 8898 8899
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;
8900

T
Tim Chen 已提交
8901 8902 8903 8904 8905 8906
			if (sched_asym_prefer(i, cpu)) {
				kick = true;
				goto unlock;
			}
		}
	}
8907
unlock:
8908
	rcu_read_unlock();
8909
	return kick;
8910 8911
}
#else
8912
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8913 8914 8915 8916 8917 8918
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8919
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
8920
{
8921
	struct rq *this_rq = this_rq();
8922
	enum cpu_idle_type idle = this_rq->idle_balance ?
8923 8924 8925
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8926
	 * If this cpu has a pending nohz_balance_kick, then do the
8927
	 * balancing on behalf of the other idle cpus whose ticks are
8928 8929 8930 8931
	 * 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.
8932
	 */
8933
	nohz_idle_balance(this_rq, idle);
8934
	rebalance_domains(this_rq, idle);
8935 8936 8937 8938 8939
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8940
void trigger_load_balance(struct rq *rq)
8941 8942
{
	/* Don't need to rebalance while attached to NULL domain */
8943 8944 8945 8946
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8947
		raise_softirq(SCHED_SOFTIRQ);
8948
#ifdef CONFIG_NO_HZ_COMMON
8949
	if (nohz_kick_needed(rq))
8950
		nohz_balancer_kick();
8951
#endif
8952 8953
}

8954 8955 8956
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8957 8958

	update_runtime_enabled(rq);
8959 8960 8961 8962 8963
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
8964 8965 8966

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
8967 8968
}

8969
#endif /* CONFIG_SMP */
8970

8971 8972 8973
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
8974
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8975 8976 8977 8978 8979 8980
{
	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
8981
		entity_tick(cfs_rq, se, queued);
8982
	}
8983

8984
	if (static_branch_unlikely(&sched_numa_balancing))
8985
		task_tick_numa(rq, curr);
8986 8987 8988
}

/*
P
Peter Zijlstra 已提交
8989 8990 8991
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
8992
 */
P
Peter Zijlstra 已提交
8993
static void task_fork_fair(struct task_struct *p)
8994
{
8995 8996
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
8997
	struct rq *rq = this_rq();
8998
	struct rq_flags rf;
8999

9000
	rq_lock(rq, &rf);
9001 9002
	update_rq_clock(rq);

9003 9004
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9005 9006
	if (curr) {
		update_curr(cfs_rq);
9007
		se->vruntime = curr->vruntime;
9008
	}
9009
	place_entity(cfs_rq, se, 1);
9010

P
Peter Zijlstra 已提交
9011
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9012
		/*
9013 9014 9015
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9016
		swap(curr->vruntime, se->vruntime);
9017
		resched_curr(rq);
9018
	}
9019

9020
	se->vruntime -= cfs_rq->min_vruntime;
9021
	rq_unlock(rq, &rf);
9022 9023
}

9024 9025 9026 9027
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9028 9029
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9030
{
9031
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9032 9033
		return;

9034 9035 9036 9037 9038
	/*
	 * 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
9039
	if (rq->curr == p) {
9040
		if (p->prio > oldprio)
9041
			resched_curr(rq);
9042
	} else
9043
		check_preempt_curr(rq, p, 0);
9044 9045
}

9046
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9047 9048 9049 9050
{
	struct sched_entity *se = &p->se;

	/*
9051 9052 9053 9054 9055 9056 9057 9058 9059 9060
	 * 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
9061
	 *
9062 9063 9064 9065
	 * - 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
9066
	 */
9067 9068 9069 9070 9071 9072
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9073 9074 9075 9076 9077 9078 9079 9080 9081 9082 9083 9084 9085 9086 9087 9088 9089 9090 9091 9092 9093 9094 9095 9096 9097
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * Propagate the changes of the sched_entity across the tg tree to make it
 * visible to the root
 */
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq;

	/* Start to propagate at parent */
	se = se->parent;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);

		if (cfs_rq_throttled(cfs_rq))
			break;

		update_load_avg(se, UPDATE_TG);
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9098
static void detach_entity_cfs_rq(struct sched_entity *se)
9099 9100 9101
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9102
	/* Catch up with the cfs_rq and remove our load when we leave */
9103
	update_load_avg(se, 0);
9104
	detach_entity_load_avg(cfs_rq, se);
9105
	update_tg_load_avg(cfs_rq, false);
9106
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9107 9108
}

9109
static void attach_entity_cfs_rq(struct sched_entity *se)
9110
{
9111
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9112 9113

#ifdef CONFIG_FAIR_GROUP_SCHED
9114 9115 9116 9117 9118 9119
	/*
	 * 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
9120

9121
	/* Synchronize entity with its cfs_rq */
9122
	update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9123
	attach_entity_load_avg(cfs_rq, se);
9124
	update_tg_load_avg(cfs_rq, false);
9125
	propagate_entity_cfs_rq(se);
9126 9127 9128 9129 9130 9131 9132 9133 9134 9135 9136 9137 9138 9139 9140 9141 9142 9143 9144 9145 9146 9147 9148 9149 9150
}

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);
9151 9152 9153 9154

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9155

9156 9157 9158 9159 9160 9161 9162 9163
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);
9164

9165
	if (task_on_rq_queued(p)) {
9166
		/*
9167 9168 9169
		 * 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.
9170
		 */
9171 9172 9173 9174
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9175
	}
9176 9177
}

9178 9179 9180 9181 9182 9183 9184 9185 9186
/* 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;

9187 9188 9189 9190 9191 9192 9193
	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);
	}
9194 9195
}

9196 9197 9198 9199 9200 9201 9202
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
	cfs_rq->tasks_timeline = RB_ROOT;
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9203
#ifdef CONFIG_SMP
9204 9205 9206
#ifdef CONFIG_FAIR_GROUP_SCHED
	cfs_rq->propagate_avg = 0;
#endif
9207 9208
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
9209
#endif
9210 9211
}

P
Peter Zijlstra 已提交
9212
#ifdef CONFIG_FAIR_GROUP_SCHED
9213 9214 9215 9216 9217 9218 9219 9220
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;
}

9221
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9222
{
9223
	detach_task_cfs_rq(p);
9224
	set_task_rq(p, task_cpu(p));
9225 9226 9227 9228 9229

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9230
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9231
}
9232

9233 9234 9235 9236 9237 9238 9239 9240 9241 9242 9243 9244 9245
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;
	}
}

9246 9247 9248 9249 9250 9251 9252 9253 9254
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]);
9255
		if (tg->se)
9256 9257 9258 9259 9260 9261 9262 9263 9264 9265
			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;
9266
	struct cfs_rq *cfs_rq;
9267 9268 9269 9270 9271 9272 9273 9274 9275 9276 9277 9278 9279 9280 9281 9282 9283 9284 9285 9286 9287 9288 9289 9290 9291 9292
	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]);
9293
		init_entity_runnable_average(se);
9294 9295 9296 9297 9298 9299 9300 9301 9302 9303
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9304 9305 9306 9307 9308 9309 9310 9311 9312 9313 9314
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);
9315
		update_rq_clock(rq);
9316
		attach_entity_cfs_rq(se);
9317
		sync_throttle(tg, i);
9318 9319 9320 9321
		raw_spin_unlock_irq(&rq->lock);
	}
}

9322
void unregister_fair_sched_group(struct task_group *tg)
9323 9324
{
	unsigned long flags;
9325 9326
	struct rq *rq;
	int cpu;
9327

9328 9329 9330
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
9331

9332 9333 9334 9335 9336 9337 9338 9339 9340 9341 9342 9343 9344
		/*
		 * 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);
	}
9345 9346 9347 9348 9349 9350 9351 9352 9353 9354 9355 9356 9357 9358 9359 9360 9361 9362 9363
}

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
9364
	if (!parent) {
9365
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
9366 9367
		se->depth = 0;
	} else {
9368
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
9369 9370
		se->depth = parent->depth + 1;
	}
9371 9372

	se->my_q = cfs_rq;
9373 9374
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
9375 9376 9377 9378 9379 9380 9381 9382 9383 9384 9385 9386 9387 9388 9389 9390 9391 9392 9393 9394 9395 9396 9397 9398
	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);
9399 9400
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
9401 9402

		/* Propagate contribution to hierarchy */
9403
		rq_lock_irqsave(rq, &rf);
9404
		update_rq_clock(rq);
9405 9406 9407 9408
		for_each_sched_entity(se) {
			update_load_avg(se, UPDATE_TG);
			update_cfs_shares(se);
		}
9409
		rq_unlock_irqrestore(rq, &rf);
9410 9411 9412 9413 9414 9415 9416 9417 9418 9419 9420 9421 9422 9423 9424
	}

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;
}

9425 9426
void online_fair_sched_group(struct task_group *tg) { }

9427
void unregister_fair_sched_group(struct task_group *tg) { }
9428 9429 9430

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
9431

9432
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9433 9434 9435 9436 9437 9438 9439 9440 9441
{
	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)
9442
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9443 9444 9445 9446

	return rr_interval;
}

9447 9448 9449
/*
 * All the scheduling class methods:
 */
9450
const struct sched_class fair_sched_class = {
9451
	.next			= &idle_sched_class,
9452 9453 9454
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
9455
	.yield_to_task		= yield_to_task_fair,
9456

I
Ingo Molnar 已提交
9457
	.check_preempt_curr	= check_preempt_wakeup,
9458 9459 9460 9461

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

9462
#ifdef CONFIG_SMP
L
Li Zefan 已提交
9463
	.select_task_rq		= select_task_rq_fair,
9464
	.migrate_task_rq	= migrate_task_rq_fair,
9465

9466 9467
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
9468

9469
	.task_dead		= task_dead_fair,
9470
	.set_cpus_allowed	= set_cpus_allowed_common,
9471
#endif
9472

9473
	.set_curr_task          = set_curr_task_fair,
9474
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
9475
	.task_fork		= task_fork_fair,
9476 9477

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
9478
	.switched_from		= switched_from_fair,
9479
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
9480

9481 9482
	.get_rr_interval	= get_rr_interval_fair,

9483 9484
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
9485
#ifdef CONFIG_FAIR_GROUP_SCHED
9486
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
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#endif
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};

#ifdef CONFIG_SCHED_DEBUG
9491
void print_cfs_stats(struct seq_file *m, int cpu)
9492
{
9493
	struct cfs_rq *cfs_rq, *pos;
9494

9495
	rcu_read_lock();
9496
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
9497
		print_cfs_rq(m, cpu, cfs_rq);
9498
	rcu_read_unlock();
9499
}
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#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 */
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__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

9527
#ifdef CONFIG_NO_HZ_COMMON
9528
	nohz.next_balance = jiffies;
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	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}