Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[~shefty/rdma-dev.git] / kernel / sched / fair.c

/*
 * 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>
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
 */

#include <linux/latencytop.h>
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>

#include <trace/events/sched.h>

#include "sched.h"

/*
 * Targeted preemption latency for CPU-bound tasks:
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
 *
 * NOTE: this latency value is not the same as the concept of
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
 *
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
 */
unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;

/*
 * The initial- and re-scaling of tunables is configurable
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 *
 * Options are:
 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 */
enum sched_tunable_scaling sysctl_sched_tunable_scaling
        = SCHED_TUNABLESCALING_LOG;

/*
 * Minimal preemption granularity for CPU-bound tasks:
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
 */
unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;

/*
 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
static unsigned int sched_nr_latency = 8;

/*
 * After fork, child runs first. If set to 0 (default) then
 * parent will (try to) run first.
 */
unsigned int sysctl_sched_child_runs_first __read_mostly;

/*
 * SCHED_OTHER wake-up granularity.
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;

const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

#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.
 *
 * default: 5 msec, units: microseconds
  */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

/*
 * 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:
 */
static int get_update_sysctl_factor(void)
{
        unsigned int cpus = min_t(int, num_online_cpus(), 8);
        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();
}

#if BITS_PER_LONG == 32
# define WMULT_CONST    (~0UL)
#else
# define WMULT_CONST    (1UL << 32)
#endif

#define WMULT_SHIFT     32

/*
 * Shift right and round:
 */
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))

/*
 * delta *= weight / lw
 */
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
                struct load_weight *lw)
{
        u64 tmp;

        /*
         * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
         * entities since MIN_SHARES = 2. Treat weight as 1 if less than
         * 2^SCHED_LOAD_RESOLUTION.
         */
        if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
                tmp = (u64)delta_exec * scale_load_down(weight);
        else
                tmp = (u64)delta_exec;

        if (!lw->inv_weight) {
                unsigned long 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;
        }

        /*
         * Check whether we'd overflow the 64-bit multiplication:
         */
        if (unlikely(tmp > WMULT_CONST))
                tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
                        WMULT_SHIFT/2);
        else
                tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);

        return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}


const struct sched_class fair_sched_class;

/**************************************************************
 * CFS operations on generic schedulable entities:
 */

#ifdef CONFIG_FAIR_GROUP_SCHED

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

/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)      (!se->my_q)

static inline struct task_struct *task_of(struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
        WARN_ON_ONCE(!entity_is_task(se));
#endif
        return container_of(se, struct task_struct, se);
}

/* 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;
}

static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
        if (!cfs_rq->on_list) {
                /*
                 * Ensure we either appear before our parent (if already
                 * enqueued) or force our parent to appear after us when it is
                 * enqueued.  The fact that we always enqueue bottom-up
                 * reduces this to two cases.
                 */
                if (cfs_rq->tg->parent &&
                    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
                        list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
                                &rq_of(cfs_rq)->leaf_cfs_rq_list);
                } else {
                        list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
                                &rq_of(cfs_rq)->leaf_cfs_rq_list);
                }

                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;
        }
}

/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
        list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
        if (se->cfs_rq == pse->cfs_rq)
                return 1;

        return 0;
}

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

/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
        int depth = 0;

        for_each_sched_entity(se)
                depth++;

        return depth;
}

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 */
        se_depth = depth_se(*se);
        pse_depth = depth_se(*pse);

        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);
        }
}

#else   /* !CONFIG_FAIR_GROUP_SCHED */

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

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

#define entity_is_task(se)      1

#define for_each_sched_entity(se) \
                for (; se; se = NULL)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
        return &task_rq(p)->cfs;
}

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;
}

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)
{
}

#define for_each_leaf_cfs_rq(rq, cfs_rq) \
                for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
        return 1;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
        return NULL;
}

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

#endif  /* CONFIG_FAIR_GROUP_SCHED */

static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);

/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

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

        return min_vruntime;
}

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

        return min_vruntime;
}

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

static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
        u64 vruntime = cfs_rq->min_vruntime;

        if (cfs_rq->curr)
                vruntime = cfs_rq->curr->vruntime;

        if (cfs_rq->rb_leftmost) {
                struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
                                                   struct sched_entity,
                                                   run_node);

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

        cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
#ifndef CONFIG_64BIT
        smp_wmb();
        cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
}

/*
 * Enqueue an entity into the rb-tree:
 */
static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        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.
                 */
                if (entity_before(se, entry)) {
                        link = &parent->rb_left;
                } else {
                        link = &parent->rb_right;
                        leftmost = 0;
                }
        }

        /*
         * Maintain a cache of leftmost tree entries (it is frequently
         * used):
         */
        if (leftmost)
                cfs_rq->rb_leftmost = &se->run_node;

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

static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        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;
        }

        rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

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

        if (!left)
                return NULL;

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

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
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
        struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);

        if (!last)
                return NULL;

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

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

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

        if (ret || !write)
                return ret;

        sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
                                        sysctl_sched_min_granularity);

#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

        return 0;
}
#endif

/*
 * delta /= w
 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
        if (unlikely(se->load.weight != NICE_0_LOAD))
                delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);

        return delta;
}

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

        if (unlikely(nr_running > nr_latency)) {
                period = sysctl_sched_min_granularity;
                period *= nr_running;
        }

        return period;
}

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

        for_each_sched_entity(se) {
                struct load_weight *load;
                struct load_weight lw;

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

                if (unlikely(!se->on_rq)) {
                        lw = cfs_rq->load;

                        update_load_add(&lw, se->load.weight);
                        load = &lw;
                }
                slice = calc_delta_mine(slice, se->load.weight, load);
        }
        return slice;
}

/*
 * We calculate the vruntime slice of a to be inserted task
 *
 * vs = s/w
 */
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        return calc_delta_fair(sched_slice(cfs_rq, se), se);
}

static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
static void update_cfs_shares(struct cfs_rq *cfs_rq);

/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
              unsigned long delta_exec)
{
        unsigned long delta_exec_weighted;

        schedstat_set(curr->statistics.exec_max,
                      max((u64)delta_exec, curr->statistics.exec_max));

        curr->sum_exec_runtime += delta_exec;
        schedstat_add(cfs_rq, exec_clock, delta_exec);
        delta_exec_weighted = calc_delta_fair(delta_exec, curr);

        curr->vruntime += delta_exec_weighted;
        update_min_vruntime(cfs_rq);

#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
        cfs_rq->load_unacc_exec_time += delta_exec;
#endif
}

static void update_curr(struct cfs_rq *cfs_rq)
{
        struct sched_entity *curr = cfs_rq->curr;
        u64 now = rq_of(cfs_rq)->clock_task;
        unsigned long delta_exec;

        if (unlikely(!curr))
                return;

        /*
         * Get the amount of time the current task was running
         * since the last time we changed load (this cannot
         * overflow on 32 bits):
         */
        delta_exec = (unsigned long)(now - curr->exec_start);
        if (!delta_exec)
                return;

        __update_curr(cfs_rq, curr, delta_exec);
        curr->exec_start = now;

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

                trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
                cpuacct_charge(curtask, delta_exec);
                account_group_exec_runtime(curtask, delta_exec);
        }

        account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
}

/*
 * Task is being enqueued - update stats:
 */
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * Are we enqueueing a waiting task? (for current tasks
         * a dequeue/enqueue event is a NOP)
         */
        if (se != cfs_rq->curr)
                update_stats_wait_start(cfs_rq, se);
}

static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
                        rq_of(cfs_rq)->clock - se->statistics.wait_start));
        schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
        schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
                        rq_of(cfs_rq)->clock - se->statistics.wait_start);
#ifdef CONFIG_SCHEDSTATS
        if (entity_is_task(se)) {
                trace_sched_stat_wait(task_of(se),
                        rq_of(cfs_rq)->clock - se->statistics.wait_start);
        }
#endif
        schedstat_set(se->statistics.wait_start, 0);
}

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * Mark the end of the wait period if dequeueing a
         * waiting task:
         */
        if (se != cfs_rq->curr)
                update_stats_wait_end(cfs_rq, se);
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /*
         * We are starting a new run period:
         */
        se->exec_start = rq_of(cfs_rq)->clock_task;
}

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

static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        update_load_add(&cfs_rq->load, se->load.weight);
        if (!parent_entity(se))
                update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
#ifdef CONFIG_SMP
        if (entity_is_task(se))
                list_add_tail(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
#endif
        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);
        if (!parent_entity(se))
                update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
        if (entity_is_task(se))
                list_del_init(&se->group_node);
        cfs_rq->nr_running--;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/* we need this in update_cfs_load and load-balance functions below */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
# ifdef CONFIG_SMP
static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
                                            int global_update)
{
        struct task_group *tg = cfs_rq->tg;
        long load_avg;

        load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
        load_avg -= cfs_rq->load_contribution;

        if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
                atomic_add(load_avg, &tg->load_weight);
                cfs_rq->load_contribution += load_avg;
        }
}

static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
        u64 period = sysctl_sched_shares_window;
        u64 now, delta;
        unsigned long load = cfs_rq->load.weight;

        if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq))
                return;

        now = rq_of(cfs_rq)->clock_task;
        delta = now - cfs_rq->load_stamp;

        /* truncate load history at 4 idle periods */
        if (cfs_rq->load_stamp > cfs_rq->load_last &&
            now - cfs_rq->load_last > 4 * period) {
                cfs_rq->load_period = 0;
                cfs_rq->load_avg = 0;
                delta = period - 1;
        }

        cfs_rq->load_stamp = now;
        cfs_rq->load_unacc_exec_time = 0;
        cfs_rq->load_period += delta;
        if (load) {
                cfs_rq->load_last = now;
                cfs_rq->load_avg += delta * load;
        }

        /* consider updating load contribution on each fold or truncate */
        if (global_update || cfs_rq->load_period > period
            || !cfs_rq->load_period)
                update_cfs_rq_load_contribution(cfs_rq, global_update);

        while (cfs_rq->load_period > period) {
                /*
                 * Inline assembly required to prevent the compiler
                 * optimising this loop into a divmod call.
                 * See __iter_div_u64_rem() for another example of this.
                 */
                asm("" : "+rm" (cfs_rq->load_period));
                cfs_rq->load_period /= 2;
                cfs_rq->load_avg /= 2;
        }

        if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
                list_del_leaf_cfs_rq(cfs_rq);
}

static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
        long tg_weight;

        /*
         * Use this CPU's actual weight instead of the last load_contribution
         * to gain a more accurate current total weight. See
         * update_cfs_rq_load_contribution().
         */
        tg_weight = atomic_read(&tg->load_weight);
        tg_weight -= cfs_rq->load_contribution;
        tg_weight += cfs_rq->load.weight;

        return tg_weight;
}

static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
        long tg_weight, load, shares;

        tg_weight = calc_tg_weight(tg, cfs_rq);
        load = cfs_rq->load.weight;

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

        if (shares < MIN_SHARES)
                shares = MIN_SHARES;
        if (shares > tg->shares)
                shares = tg->shares;

        return shares;
}

static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
        if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
                update_cfs_load(cfs_rq, 0);
                update_cfs_shares(cfs_rq);
        }
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
{
        return tg->shares;
}

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
# endif /* CONFIG_SMP */
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
                            unsigned long weight)
{
        if (se->on_rq) {
                /* commit outstanding execution time */
                if (cfs_rq->curr == se)
                        update_curr(cfs_rq);
                account_entity_dequeue(cfs_rq, se);
        }

        update_load_set(&se->load, weight);

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

static void update_cfs_shares(struct cfs_rq *cfs_rq)
{
        struct task_group *tg;
        struct sched_entity *se;
        long shares;

        tg = cfs_rq->tg;
        se = tg->se[cpu_of(rq_of(cfs_rq))];
        if (!se || throttled_hierarchy(cfs_rq))
                return;
#ifndef CONFIG_SMP
        if (likely(se->load.weight == tg->shares))
                return;
#endif
        shares = calc_cfs_shares(cfs_rq, tg);

        reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

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

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHEDSTATS
        struct task_struct *tsk = NULL;

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

        if (se->statistics.sleep_start) {
                u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;

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

                if (unlikely(delta > se->statistics.sleep_max))
                        se->statistics.sleep_max = delta;

                se->statistics.sleep_start = 0;
                se->statistics.sum_sleep_runtime += delta;

                if (tsk) {
                        account_scheduler_latency(tsk, delta >> 10, 1);
                        trace_sched_stat_sleep(tsk, delta);
                }
        }
        if (se->statistics.block_start) {
                u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;

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

                if (unlikely(delta > se->statistics.block_max))
                        se->statistics.block_max = delta;

                se->statistics.block_start = 0;
                se->statistics.sum_sleep_runtime += delta;

                if (tsk) {
                        if (tsk->in_iowait) {
                                se->statistics.iowait_sum += delta;
                                se->statistics.iowait_count++;
                                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);
                }
        }
#endif
}

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)
                schedstat_inc(cfs_rq, nr_spread_over);
#endif
}

static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
        u64 vruntime = cfs_rq->min_vruntime;

        /*
         * 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.
         */
        if (initial && sched_feat(START_DEBIT))
                vruntime += sched_vslice(cfs_rq, se);

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

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

                vruntime -= thresh;
        }

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

        se->vruntime = vruntime;
}

static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
        /*
         * Update the normalized vruntime before updating min_vruntime
         * through callig update_curr().
         */
        if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
                se->vruntime += cfs_rq->min_vruntime;

        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);
        update_cfs_load(cfs_rq, 0);
        account_entity_enqueue(cfs_rq, se);
        update_cfs_shares(cfs_rq);

        if (flags & ENQUEUE_WAKEUP) {
                place_entity(cfs_rq, se, 0);
                enqueue_sleeper(cfs_rq, se);
        }

        update_stats_enqueue(cfs_rq, se);
        check_spread(cfs_rq, se);
        if (se != cfs_rq->curr)
                __enqueue_entity(cfs_rq, se);
        se->on_rq = 1;

        if (cfs_rq->nr_running == 1) {
                list_add_leaf_cfs_rq(cfs_rq);
                check_enqueue_throttle(cfs_rq);
        }
}

static void __clear_buddies_last(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->last == se)
                        cfs_rq->last = NULL;
                else
                        break;
        }
}

static void __clear_buddies_next(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->next == se)
                        cfs_rq->next = NULL;
                else
                        break;
        }
}

static void __clear_buddies_skip(struct sched_entity *se)
{
        for_each_sched_entity(se) {
                struct cfs_rq *cfs_rq = cfs_rq_of(se);
                if (cfs_rq->skip == se)
                        cfs_rq->skip = NULL;
                else
                        break;
        }
}

static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        if (cfs_rq->last == se)
                __clear_buddies_last(se);

        if (cfs_rq->next == se)
                __clear_buddies_next(se);

        if (cfs_rq->skip == se)
                __clear_buddies_skip(se);
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);

        update_stats_dequeue(cfs_rq, se);
        if (flags & DEQUEUE_SLEEP) {
#ifdef CONFIG_SCHEDSTATS
                if (entity_is_task(se)) {
                        struct task_struct *tsk = task_of(se);

                        if (tsk->state & TASK_INTERRUPTIBLE)
                                se->statistics.sleep_start = rq_of(cfs_rq)->clock;
                        if (tsk->state & TASK_UNINTERRUPTIBLE)
                                se->statistics.block_start = rq_of(cfs_rq)->clock;
                }
#endif
        }

        clear_buddies(cfs_rq, se);

        if (se != cfs_rq->curr)
                __dequeue_entity(cfs_rq, se);
        se->on_rq = 0;
        update_cfs_load(cfs_rq, 0);
        account_entity_dequeue(cfs_rq, se);

        /*
         * Normalize the entity after updating the min_vruntime because the
         * update can refer to the ->curr item and we need to reflect this
         * movement in our normalized position.
         */
        if (!(flags & DEQUEUE_SLEEP))
                se->vruntime -= cfs_rq->min_vruntime;

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

        update_min_vruntime(cfs_rq);
        update_cfs_shares(cfs_rq);
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
        unsigned long ideal_runtime, delta_exec;
        struct sched_entity *se;
        s64 delta;

        ideal_runtime = sched_slice(cfs_rq, curr);
        delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
        if (delta_exec > ideal_runtime) {
                resched_task(rq_of(cfs_rq)->curr);
                /*
                 * The current task ran long enough, ensure it doesn't get
                 * re-elected due to buddy favours.
                 */
                clear_buddies(cfs_rq, curr);
                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;

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

        if (delta < 0)
                return;

        if (delta > ideal_runtime)
                resched_task(rq_of(cfs_rq)->curr);
}

static void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
        /* '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.
                 */
                update_stats_wait_end(cfs_rq, se);
                __dequeue_entity(cfs_rq, se);
        }

        update_stats_curr_start(cfs_rq, se);
        cfs_rq->curr = se;
#ifdef CONFIG_SCHEDSTATS
        /*
         * 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):
         */
        if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
                se->statistics.slice_max = max(se->statistics.slice_max,
                        se->sum_exec_runtime - se->prev_sum_exec_runtime);
        }
#endif
        se->prev_sum_exec_runtime = se->sum_exec_runtime;
}

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

/*
 * 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
 */
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
{
        struct sched_entity *se = __pick_first_entity(cfs_rq);
        struct sched_entity *left = se;

        /*
         * Avoid running the skip buddy, if running something else can
         * be done without getting too unfair.
         */
        if (cfs_rq->skip == se) {
                struct sched_entity *second = __pick_next_entity(se);
                if (second && wakeup_preempt_entity(second, left) < 1)
                        se = second;
        }

        /*
         * 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;

        /*
         * 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;

        clear_buddies(cfs_rq, se);

        return se;
}

static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
{
        /*
         * If still on the runqueue then deactivate_task()
         * was not called and update_curr() has to be done:
         */
        if (prev->on_rq)
                update_curr(cfs_rq);

        /* throttle cfs_rqs exceeding runtime */
        check_cfs_rq_runtime(cfs_rq);

        check_spread(cfs_rq, prev);
        if (prev->on_rq) {
                update_stats_wait_start(cfs_rq, prev);
                /* Put 'current' back into the tree. */
                __enqueue_entity(cfs_rq, prev);
        }
        cfs_rq->curr = NULL;
}

static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
{
        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);

        /*
         * Update share accounting for long-running entities.
         */
        update_entity_shares_tick(cfs_rq);

#ifdef CONFIG_SCHED_HRTICK
        /*
         * queued ticks are scheduled to match the slice, so don't bother
         * validating it and just reschedule.
         */
        if (queued) {
                resched_task(rq_of(cfs_rq)->curr);
                return;
        }
        /*
         * 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

        if (cfs_rq->nr_running > 1)
                check_preempt_tick(cfs_rq, curr);
}


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

#ifdef CONFIG_CFS_BANDWIDTH

#ifdef HAVE_JUMP_LABEL
static struct static_key __cfs_bandwidth_used;

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

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
        /* only need to count groups transitioning between enabled/!enabled */
        if (enabled && !was_enabled)
                static_key_slow_inc(&__cfs_bandwidth_used);
        else if (!enabled && was_enabled)
                static_key_slow_dec(&__cfs_bandwidth_used);
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
        return true;
}

void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
#endif /* HAVE_JUMP_LABEL */

/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
        return 100000000ULL;
}

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

/*
 * 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
 */
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
        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);
}

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
        return &tg->cfs_bandwidth;
}

/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        struct task_group *tg = cfs_rq->tg;
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
        u64 amount = 0, min_amount, expires;

        /* 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;
        else {
                /*
                 * If the bandwidth pool has become inactive, then at least one
                 * period must have elapsed since the last consumption.
                 * Refresh the global state and ensure bandwidth timer becomes
                 * active.
                 */
                if (!cfs_b->timer_active) {
                        __refill_cfs_bandwidth_runtime(cfs_b);
                        __start_cfs_bandwidth(cfs_b);
                }

                if (cfs_b->runtime > 0) {
                        amount = min(cfs_b->runtime, min_amount);
                        cfs_b->runtime -= amount;
                        cfs_b->idle = 0;
                }
        }
        expires = cfs_b->runtime_expires;
        raw_spin_unlock(&cfs_b->lock);

        cfs_rq->runtime_remaining += amount;
        /*
         * 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;

        return cfs_rq->runtime_remaining > 0;
}

/*
 * 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)
{
        struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
        struct rq *rq = rq_of(cfs_rq);

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

        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
         * whether the global deadline has advanced.
         */

        if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
                /* 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;
        }
}

static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
                                     unsigned long delta_exec)
{
        /* dock delta_exec before expiring quota (as it could span periods) */
        cfs_rq->runtime_remaining -= delta_exec;
        expire_cfs_rq_runtime(cfs_rq);

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

        /*
         * 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))
                resched_task(rq_of(cfs_rq)->curr);
}

static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
{
        if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
                return;

        __account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
        return cfs_bandwidth_used() && cfs_rq->throttled;
}

/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
        return cfs_bandwidth_used() && cfs_rq->throttle_count;
}

/*
 * 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--;
#ifdef CONFIG_SMP
        if (!cfs_rq->throttle_count) {
                u64 delta = rq->clock_task - cfs_rq->load_stamp;

                /* leaving throttled state, advance shares averaging windows */
                cfs_rq->load_stamp += delta;
                cfs_rq->load_last += delta;

                /* update entity weight now that we are on_rq again */
                update_cfs_shares(cfs_rq);
        }
#endif

        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)];

        /* group is entering throttled state, record last load */
        if (!cfs_rq->throttle_count)
                update_cfs_load(cfs_rq, 0);
        cfs_rq->throttle_count++;

        return 0;
}

static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
{
        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;

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

        /* account load preceding throttle */
        rcu_read_lock();
        walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
        rcu_read_unlock();

        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)
                rq->nr_running -= task_delta;

        cfs_rq->throttled = 1;
        cfs_rq->throttled_timestamp = rq->clock;
        raw_spin_lock(&cfs_b->lock);
        list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
        raw_spin_unlock(&cfs_b->lock);
}

void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
{
        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;

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

        cfs_rq->throttled = 0;
        raw_spin_lock(&cfs_b->lock);
        cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp;
        list_del_rcu(&cfs_rq->throttled_list);
        raw_spin_unlock(&cfs_b->lock);
        cfs_rq->throttled_timestamp = 0;

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

        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)
                rq->nr_running += task_delta;

        /* determine whether we need to wake up potentially idle cpu */
        if (rq->curr == rq->idle && rq->cfs.nr_running)
                resched_task(rq->curr);
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
                u64 remaining, u64 expires)
{
        struct cfs_rq *cfs_rq;
        u64 runtime = remaining;

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

                raw_spin_lock(&rq->lock);
                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:
                raw_spin_unlock(&rq->lock);

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

        return remaining;
}

/*
 * 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)
{
        u64 runtime, runtime_expires;
        int idle = 1, throttled;

        raw_spin_lock(&cfs_b->lock);
        /* no need to continue the timer with no bandwidth constraint */
        if (cfs_b->quota == RUNTIME_INF)
                goto out_unlock;

        throttled = !list_empty(&cfs_b->throttled_cfs_rq);
        /* idle depends on !throttled (for the case of a large deficit) */
        idle = cfs_b->idle && !throttled;
        cfs_b->nr_periods += overrun;

        /* if we're going inactive then everything else can be deferred */
        if (idle)
                goto out_unlock;

        __refill_cfs_bandwidth_runtime(cfs_b);

        if (!throttled) {
                /* mark as potentially idle for the upcoming period */
                cfs_b->idle = 1;
                goto out_unlock;
        }

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

        /*
         * There are throttled entities so we must first use the new bandwidth
         * to unthrottle them before making it generally available.  This
         * ensures that all existing debts will be paid before a new cfs_rq is
         * allowed to run.
         */
        runtime = cfs_b->runtime;
        runtime_expires = cfs_b->runtime_expires;
        cfs_b->runtime = 0;

        /*
         * 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.
         */
        while (throttled && runtime > 0) {
                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);
        }

        /* return (any) remaining runtime */
        cfs_b->runtime = runtime;
        /*
         * 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;
out_unlock:
        if (idle)
                cfs_b->timer_active = 0;
        raw_spin_unlock(&cfs_b->lock);

        return idle;
}

/* 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;

/* are we near the end of the current quota period? */
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;

        start_bandwidth_timer(&cfs_b->slack_timer,
                                ns_to_ktime(cfs_bandwidth_slack_period));
}

/* 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)
{
        if (!cfs_bandwidth_used())
                return;

        if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
                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 */
        if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
                return;

        raw_spin_lock(&cfs_b->lock);
        if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
                runtime = cfs_b->runtime;
                cfs_b->runtime = 0;
        }
        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)
                cfs_b->runtime = runtime;
        raw_spin_unlock(&cfs_b->lock);
}

/*
 * 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)
{
        if (!cfs_bandwidth_used())
                return;

        /* 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);
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
        if (!cfs_bandwidth_used())
                return;

        if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
                return;

        /*
         * 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))
                return;

        throttle_cfs_rq(cfs_rq);
}

static inline u64 default_cfs_period(void);
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b);

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
        struct cfs_bandwidth *cfs_b =
                container_of(timer, struct cfs_bandwidth, slack_timer);
        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);
        ktime_t now;
        int overrun;
        int idle = 0;

        for (;;) {
                now = hrtimer_cb_get_time(timer);
                overrun = hrtimer_forward(timer, now, cfs_b->period);

                if (!overrun)
                        break;

                idle = do_sched_cfs_period_timer(cfs_b, overrun);
        }

        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);
        hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        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);
}

/* requires cfs_b->lock, may release to reprogram timer */
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
        /*
         * The timer may be active because we're trying to set a new bandwidth
         * period or because we're racing with the tear-down path
         * (timer_active==0 becomes visible before the hrtimer call-back
         * terminates).  In either case we ensure that it's re-programmed
         */
        while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
                raw_spin_unlock(&cfs_b->lock);
                /* ensure cfs_b->lock is available while we wait */
                hrtimer_cancel(&cfs_b->period_timer);

                raw_spin_lock(&cfs_b->lock);
                /* if someone else restarted the timer then we're done */
                if (cfs_b->timer_active)
                        return;
        }

        cfs_b->timer_active = 1;
        start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
        hrtimer_cancel(&cfs_b->period_timer);
        hrtimer_cancel(&cfs_b->slack_timer);
}

void unthrottle_offline_cfs_rqs(struct rq *rq)
{
        struct cfs_rq *cfs_rq;

        for_each_leaf_cfs_rq(rq, cfs_rq) {
                struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

                if (!cfs_rq->runtime_enabled)
                        continue;

                /*
                 * clock_task is not advancing so we just need to make sure
                 * there's some valid quota amount
                 */
                cfs_rq->runtime_remaining = cfs_b->quota;
                if (cfs_rq_throttled(cfs_rq))
                        unthrottle_cfs_rq(cfs_rq);
        }
}

#else /* CONFIG_CFS_BANDWIDTH */
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) {}
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}

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

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;
}

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) {}
#endif

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) {}
void unthrottle_offline_cfs_rqs(struct rq *rq) {}

#endif /* CONFIG_CFS_BANDWIDTH */

/**************************************************
 * CFS operations on tasks:
 */

#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);

        WARN_ON(task_rq(p) != rq);

        if (cfs_rq->nr_running > 1) {
                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)
                                resched_task(p);
                        return;
                }

                /*
                 * Don't schedule slices shorter than 10000ns, that just
                 * doesn't make sense. Rely on vruntime for fairness.
                 */
                if (rq->curr != p)
                        delta = max_t(s64, 10000LL, delta);

                hrtick_start(rq, delta);
        }
}

/*
 * 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;

        if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
                return;

        if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
                hrtick_start_fair(rq, curr);
}
#else /* !CONFIG_SCHED_HRTICK */
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}

static inline void hrtick_update(struct rq *rq)
{
}
#endif

/*
 * 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:
 */
static void
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;

        for_each_sched_entity(se) {
                if (se->on_rq)
                        break;
                cfs_rq = cfs_rq_of(se);
                enqueue_entity(cfs_rq, se, flags);

                /*
                 * 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.
                */
                if (cfs_rq_throttled(cfs_rq))
                        break;
                cfs_rq->h_nr_running++;

                flags = ENQUEUE_WAKEUP;
        }

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                cfs_rq->h_nr_running++;

                if (cfs_rq_throttled(cfs_rq))
                        break;

                update_cfs_load(cfs_rq, 0);
                update_cfs_shares(cfs_rq);
        }

        if (!se)
                inc_nr_running(rq);
        hrtick_update(rq);
}

static void set_next_buddy(struct sched_entity *se);

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;
        int task_sleep = flags & DEQUEUE_SLEEP;

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                dequeue_entity(cfs_rq, se, flags);

                /*
                 * 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;
                cfs_rq->h_nr_running--;

                /* Don't dequeue parent if it has other entities besides us */
                if (cfs_rq->load.weight) {
                        /*
                         * Bias pick_next to pick a task from this cfs_rq, as
                         * p is sleeping when it is within its sched_slice.
                         */
                        if (task_sleep && parent_entity(se))
                                set_next_buddy(parent_entity(se));

                        /* avoid re-evaluating load for this entity */
                        se = parent_entity(se);
                        break;
                }
                flags |= DEQUEUE_SLEEP;
        }

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                cfs_rq->h_nr_running--;

                if (cfs_rq_throttled(cfs_rq))
                        break;

                update_cfs_load(cfs_rq, 0);
                update_cfs_shares(cfs_rq);
        }

        if (!se)
                dec_nr_running(rq);
        hrtick_update(rq);
}

#ifdef CONFIG_SMP
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
        return cpu_rq(cpu)->load.weight;
}

/*
 * Return a low guess at the load of a migration-source cpu weighted
 * according to the scheduling class and "nice" value.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static unsigned long source_load(int cpu, int type)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long total = weighted_cpuload(cpu);

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

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

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

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

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

static unsigned long power_of(int cpu)
{
        return cpu_rq(cpu)->cpu_power;
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
        struct rq *rq = cpu_rq(cpu);
        unsigned long nr_running = ACCESS_ONCE(rq->nr_running);

        if (nr_running)
                return rq->load.weight / nr_running;

        return 0;
}


static void task_waking_fair(struct task_struct *p)
{
        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;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * effective_load() calculates the load change as seen from the root_task_group
 *
 * Adding load to a group doesn't make a group heavier, but can cause movement
 * of group shares between cpus. Assuming the shares were perfectly aligned one
 * can calculate the shift in shares.
 *
 * Calculate the effective load difference if @wl is added (subtracted) to @tg
 * on this @cpu and results in a total addition (subtraction) of @wg to the
 * total group weight.
 *
 * Given a runqueue weight distribution (rw_i) we can compute a shares
 * distribution (s_i) using:
 *
 *   s_i = rw_i / \Sum rw_j                                             (1)
 *
 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
 * shares distribution (s_i):
 *
 *   rw_i = {   2,   4,   1,   0 }
 *   s_i  = { 2/7, 4/7, 1/7,   0 }
 *
 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
 * task used to run on and the CPU the waker is running on), we need to
 * compute the effect of waking a task on either CPU and, in case of a sync
 * wakeup, compute the effect of the current task going to sleep.
 *
 * So for a change of @wl to the local @cpu with an overall group weight change
 * of @wl we can compute the new shares distribution (s'_i) using:
 *
 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)                            (2)
 *
 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
 * differences in waking a task to CPU 0. The additional task changes the
 * weight and shares distributions like:
 *
 *   rw'_i = {   3,   4,   1,   0 }
 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
 *
 * We can then compute the difference in effective weight by using:
 *
 *   dw_i = S * (s'_i - s_i)                                            (3)
 *
 * Where 'S' is the group weight as seen by its parent.
 *
 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
 * 4/7) times the weight of the group.
 */
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
{
        struct sched_entity *se = tg->se[cpu];

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

        for_each_sched_entity(se) {
                long w, W;

                tg = se->my_q->tg;

                /*
                 * W = @wg + \Sum rw_j
                 */
                W = wg + calc_tg_weight(tg, se->my_q);

                /*
                 * w = rw_i + @wl
                 */
                w = se->my_q->load.weight + wl;

                /*
                 * wl = S * s'_i; see (2)
                 */
                if (W > 0 && w < W)
                        wl = (w * tg->shares) / W;
                else
                        wl = tg->shares;

                /*
                 * Per the above, wl is the new se->load.weight value; since
                 * those are clipped to [MIN_SHARES, ...) do so now. See
                 * calc_cfs_shares().
                 */
                if (wl < MIN_SHARES)
                        wl = MIN_SHARES;

                /*
                 * wl = dw_i = S * (s'_i - s_i); see (3)
                 */
                wl -= se->load.weight;

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

        return wl;
}
#else

static inline unsigned long effective_load(struct task_group *tg, int cpu,
                unsigned long wl, unsigned long wg)
{
        return wl;
}

#endif

static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
{
        s64 this_load, load;
        int idx, this_cpu, prev_cpu;
        unsigned long tl_per_task;
        struct task_group *tg;
        unsigned long weight;
        int balanced;

        idx       = sd->wake_idx;
        this_cpu  = smp_processor_id();
        prev_cpu  = task_cpu(p);
        load      = source_load(prev_cpu, idx);
        this_load = target_load(this_cpu, idx);

        /*
         * If sync wakeup then subtract the (maximum possible)
         * effect of the currently running task from the load
         * of the current CPU:
         */
        if (sync) {
                tg = task_group(current);
                weight = current->se.load.weight;

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

        tg = task_group(p);
        weight = p->se.load.weight;

        /*
         * In low-load situations, where prev_cpu is idle and this_cpu is idle
         * due to the sync cause above having dropped this_load to 0, we'll
         * always have an imbalance, but there's really nothing you can do
         * about that, so that's good too.
         *
         * Otherwise check if either cpus are near enough in load to allow this
         * task to be woken on this_cpu.
         */
        if (this_load > 0) {
                s64 this_eff_load, prev_eff_load;

                this_eff_load = 100;
                this_eff_load *= power_of(prev_cpu);
                this_eff_load *= this_load +
                        effective_load(tg, this_cpu, weight, weight);

                prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
                prev_eff_load *= power_of(this_cpu);
                prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

                balanced = this_eff_load <= prev_eff_load;
        } else
                balanced = true;

        /*
         * If the currently running task will sleep within
         * a reasonable amount of time then attract this newly
         * woken task:
         */
        if (sync && balanced)
                return 1;

        schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
        tl_per_task = cpu_avg_load_per_task(this_cpu);

        if (balanced ||
            (this_load <= load &&
             this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
                /*
                 * This domain has SD_WAKE_AFFINE and
                 * p is cache cold in this domain, and
                 * there is no bad imbalance.
                 */
                schedstat_inc(sd, ttwu_move_affine);
                schedstat_inc(p, se.statistics.nr_wakeups_affine);

                return 1;
        }
        return 0;
}

/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
                  int this_cpu, int load_idx)
{
        struct sched_group *idlest = NULL, *group = sd->groups;
        unsigned long min_load = ULONG_MAX, this_load = 0;
        int imbalance = 100 + (sd->imbalance_pct-100)/2;

        do {
                unsigned long load, avg_load;
                int local_group;
                int i;

                /* Skip over this group if it has no CPUs allowed */
                if (!cpumask_intersects(sched_group_cpus(group),
                                        tsk_cpus_allowed(p)))
                        continue;

                local_group = cpumask_test_cpu(this_cpu,
                                               sched_group_cpus(group));

                /* Tally up the load of all CPUs in the group */
                avg_load = 0;

                for_each_cpu(i, sched_group_cpus(group)) {
                        /* Bias balancing toward cpus of our domain */
                        if (local_group)
                                load = source_load(i, load_idx);
                        else
                                load = target_load(i, load_idx);

                        avg_load += load;
                }

                /* Adjust by relative CPU power of the group */
                avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;

                if (local_group) {
                        this_load = avg_load;
                } else if (avg_load < min_load) {
                        min_load = avg_load;
                        idlest = group;
                }
        } while (group = group->next, group != sd->groups);

        if (!idlest || 100*this_load < imbalance*min_load)
                return NULL;
        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;
        int idlest = -1;
        int i;

        /* Traverse only the allowed CPUs */
        for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
                load = weighted_cpuload(i);

                if (load < min_load || (load == min_load && i == this_cpu)) {
                        min_load = load;
                        idlest = i;
                }
        }

        return idlest;
}

/*
 * Try and locate an idle CPU in the sched_domain.
 */
static int select_idle_sibling(struct task_struct *p, int target)
{
        int cpu = smp_processor_id();
        int prev_cpu = task_cpu(p);
        struct sched_domain *sd;
        struct sched_group *sg;
        int i;

        /*
         * If the task is going to be woken-up on this cpu and if it is
         * already idle, then it is the right target.
         */
        if (target == cpu && idle_cpu(cpu))
                return cpu;

        /*
         * If the task is going to be woken-up on the cpu where it previously
         * ran and if it is currently idle, then it the right target.
         */
        if (target == prev_cpu && idle_cpu(prev_cpu))
                return prev_cpu;

        /*
         * Otherwise, iterate the domains and find an elegible idle cpu.
         */
        sd = rcu_dereference(per_cpu(sd_llc, target));
        for_each_lower_domain(sd) {
                sg = sd->groups;
                do {
                        if (!cpumask_intersects(sched_group_cpus(sg),
                                                tsk_cpus_allowed(p)))
                                goto next;

                        for_each_cpu(i, sched_group_cpus(sg)) {
                                if (!idle_cpu(i))
                                        goto next;
                        }

                        target = cpumask_first_and(sched_group_cpus(sg),
                                        tsk_cpus_allowed(p));
                        goto done;
next:
                        sg = sg->next;
                } while (sg != sd->groups);
        }
done:
        return target;
}

/*
 * sched_balance_self: balance the current task (running on cpu) in domains
 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
 * SD_BALANCE_EXEC.
 *
 * Balance, ie. select the least loaded group.
 *
 * Returns the target CPU number, or the same CPU if no balancing is needed.
 *
 * preempt must be disabled.
 */
static int
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
{
        struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
        int cpu = smp_processor_id();
        int prev_cpu = task_cpu(p);
        int new_cpu = cpu;
        int want_affine = 0;
        int want_sd = 1;
        int sync = wake_flags & WF_SYNC;

        if (p->rt.nr_cpus_allowed == 1)
                return prev_cpu;

        if (sd_flag & SD_BALANCE_WAKE) {
                if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
                        want_affine = 1;
                new_cpu = prev_cpu;
        }

        rcu_read_lock();
        for_each_domain(cpu, tmp) {
                if (!(tmp->flags & SD_LOAD_BALANCE))
                        continue;

                /*
                 * If power savings logic is enabled for a domain, see if we
                 * are not overloaded, if so, don't balance wider.
                 */
                if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
                        unsigned long power = 0;
                        unsigned long nr_running = 0;
                        unsigned long capacity;
                        int i;

                        for_each_cpu(i, sched_domain_span(tmp)) {
                                power += power_of(i);
                                nr_running += cpu_rq(i)->cfs.nr_running;
                        }

                        capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);

                        if (tmp->flags & SD_POWERSAVINGS_BALANCE)
                                nr_running /= 2;

                        if (nr_running < capacity)
                                want_sd = 0;
                }

                /*
                 * If both cpu and prev_cpu are part of this domain,
                 * cpu is a valid SD_WAKE_AFFINE target.
                 */
                if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
                    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
                        affine_sd = tmp;
                        want_affine = 0;
                }

                if (!want_sd && !want_affine)
                        break;

                if (!(tmp->flags & sd_flag))
                        continue;

                if (want_sd)
                        sd = tmp;
        }

        if (affine_sd) {
                if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
                        prev_cpu = cpu;

                new_cpu = select_idle_sibling(p, prev_cpu);
                goto unlock;
        }

        while (sd) {
                int load_idx = sd->forkexec_idx;
                struct sched_group *group;
                int weight;

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

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

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

                new_cpu = find_idlest_cpu(group, p, cpu);
                if (new_cpu == -1 || new_cpu == cpu) {
                        /* Now try balancing at a lower domain level of cpu */
                        sd = sd->child;
                        continue;
                }

                /* Now try balancing at a lower domain level of new_cpu */
                cpu = new_cpu;
                weight = sd->span_weight;
                sd = NULL;
                for_each_domain(cpu, tmp) {
                        if (weight <= tmp->span_weight)
                                break;
                        if (tmp->flags & sd_flag)
                                sd = tmp;
                }
                /* while loop will break here if sd == NULL */
        }
unlock:
        rcu_read_unlock();

        return new_cpu;
}
#endif /* CONFIG_SMP */

static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
{
        unsigned long gran = sysctl_sched_wakeup_granularity;

        /*
         * Since its curr running now, convert the gran from real-time
         * to virtual-time in his units.
         *
         * 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.
         */
        return calc_delta_fair(gran, se);
}

/*
 * 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;

        gran = wakeup_gran(curr, se);
        if (vdiff > gran)
                return 1;

        return 0;
}

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

        for_each_sched_entity(se)
                cfs_rq_of(se)->last = se;
}

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

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

static void set_skip_buddy(struct sched_entity *se)
{
        for_each_sched_entity(se)
                cfs_rq_of(se)->skip = se;
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
        struct task_struct *curr = rq->curr;
        struct sched_entity *se = &curr->se, *pse = &p->se;
        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
        int scale = cfs_rq->nr_running >= sched_nr_latency;
        int next_buddy_marked = 0;

        if (unlikely(se == pse))
                return;

        /*
         * This is possible from callers such as move_task(), in which we
         * 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;

        if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
                set_next_buddy(pse);
                next_buddy_marked = 1;
        }

        /*
         * We can come here with TIF_NEED_RESCHED already set from new task
         * wake up path.
         *
         * 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.
         */
        if (test_tsk_need_resched(curr))
                return;

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

        /*
         * Batch and idle tasks do not preempt non-idle tasks (their preemption
         * is driven by the tick):
         */
        if (unlikely(p->policy != SCHED_NORMAL))
                return;

        find_matching_se(&se, &pse);
        update_curr(cfs_rq_of(se));
        BUG_ON(!pse);
        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);
                goto preempt;
        }

        return;

preempt:
        resched_task(curr);
        /*
         * 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);
}

static struct task_struct *pick_next_task_fair(struct rq *rq)
{
        struct task_struct *p;
        struct cfs_rq *cfs_rq = &rq->cfs;
        struct sched_entity *se;

        if (!cfs_rq->nr_running)
                return NULL;

        do {
                se = pick_next_entity(cfs_rq);
                set_next_entity(cfs_rq, se);
                cfs_rq = group_cfs_rq(se);
        } while (cfs_rq);

        p = task_of(se);
        if (hrtick_enabled(rq))
                hrtick_start_fair(rq, p);

        return p;
}

/*
 * Account for a descheduled task:
 */
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
{
        struct sched_entity *se = &prev->se;
        struct cfs_rq *cfs_rq;

        for_each_sched_entity(se) {
                cfs_rq = cfs_rq_of(se);
                put_prev_entity(cfs_rq, se);
        }
}

/*
 * 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);
                /*
                 * Tell update_rq_clock() that we've just updated,
                 * so we don't do microscopic update in schedule()
                 * and double the fastpath cost.
                 */
                 rq->skip_clock_update = 1;
        }

        set_skip_buddy(se);
}

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

        /* throttled hierarchies are not runnable */
        if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
                return false;

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

        yield_task_fair(rq);

        return true;
}

#ifdef CONFIG_SMP
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

static unsigned long __read_mostly max_load_balance_interval = HZ/10;

#define LBF_ALL_PINNED  0x01
#define LBF_NEED_BREAK  0x02

struct lb_env {
        struct sched_domain     *sd;

        int                     src_cpu;
        struct rq               *src_rq;

        int                     dst_cpu;
        struct rq               *dst_rq;

        enum cpu_idle_type      idle;
        long                    load_move;
        unsigned int            flags;

        unsigned int            loop;
        unsigned int            loop_break;
        unsigned int            loop_max;
};

/*
 * move_task - move a task from one runqueue to another runqueue.
 * Both runqueues must be locked.
 */
static void move_task(struct task_struct *p, struct lb_env *env)
{
        deactivate_task(env->src_rq, p, 0);
        set_task_cpu(p, env->dst_cpu);
        activate_task(env->dst_rq, p, 0);
        check_preempt_curr(env->dst_rq, p, 0);
}

/*
 * Is this task likely cache-hot:
 */
static int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
        s64 delta;

        if (p->sched_class != &fair_sched_class)
                return 0;

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

        /*
         * Buddy candidates are cache hot:
         */
        if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
                        (&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;

        delta = now - p->se.exec_start;

        return delta < (s64)sysctl_sched_migration_cost;
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct lb_env *env)
{
        int tsk_cache_hot = 0;
        /*
         * We do not migrate tasks that are:
         * 1) running (obviously), or
         * 2) cannot be migrated to this CPU due to cpus_allowed, or
         * 3) are cache-hot on their current CPU.
         */
        if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
                schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
                return 0;
        }
        env->flags &= ~LBF_ALL_PINNED;

        if (task_running(env->src_rq, p)) {
                schedstat_inc(p, se.statistics.nr_failed_migrations_running);
                return 0;
        }

        /*
         * Aggressive migration if:
         * 1) task is cache cold, or
         * 2) too many balance attempts have failed.
         */

        tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
        if (!tsk_cache_hot ||
                env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
                if (tsk_cache_hot) {
                        schedstat_inc(env->sd, lb_hot_gained[env->idle]);
                        schedstat_inc(p, se.statistics.nr_forced_migrations);
                }
#endif
                return 1;
        }

        if (tsk_cache_hot) {
                schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
                return 0;
        }
        return 1;
}

/*
 * move_one_task tries to move exactly one task from busiest to this_rq, as
 * part of active balancing operations within "domain".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_one_task(struct lb_env *env)
{
        struct task_struct *p, *n;

        list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
                if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu))
                        continue;

                if (!can_migrate_task(p, env))
                        continue;

                move_task(p, env);
                /*
                 * Right now, this is only the second place move_task()
                 * is called, so we can safely collect move_task()
                 * stats here rather than inside move_task().
                 */
                schedstat_inc(env->sd, lb_gained[env->idle]);
                return 1;
        }
        return 0;
}

static unsigned long task_h_load(struct task_struct *p);

/*
 * move_tasks tries to move up to load_move weighted load from busiest to
 * this_rq, as part of a balancing operation within domain "sd".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(struct lb_env *env)
{
        struct list_head *tasks = &env->src_rq->cfs_tasks;
        struct task_struct *p;
        unsigned long load;
        int pulled = 0;

        if (env->load_move <= 0)
                return 0;

        while (!list_empty(tasks)) {
                p = list_first_entry(tasks, struct task_struct, se.group_node);

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

                /* take a breather every nr_migrate tasks */
                if (env->loop > env->loop_break) {
                        env->loop_break += sysctl_sched_nr_migrate;
                        env->flags |= LBF_NEED_BREAK;
                        break;
                }

                if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
                        goto next;

                load = task_h_load(p);

                if (load < 16 && !env->sd->nr_balance_failed)
                        goto next;

                if ((load / 2) > env->load_move)
                        goto next;

                if (!can_migrate_task(p, env))
                        goto next;

                move_task(p, env);
                pulled++;
                env->load_move -= load;

#ifdef CONFIG_PREEMPT
                /*
                 * NEWIDLE balancing is a source of latency, so preemptible
                 * kernels will stop after the first task is pulled to minimize
                 * the critical section.
                 */
                if (env->idle == CPU_NEWLY_IDLE)
                        break;
#endif

                /*
                 * We only want to steal up to the prescribed amount of
                 * weighted load.
                 */
                if (env->load_move <= 0)
                        break;

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

        /*
         * Right now, this is one of only two places move_task() is called,
         * so we can safely collect move_task() stats here rather than
         * inside move_task().
         */
        schedstat_add(env->sd, lb_gained[env->idle], pulled);

        return pulled;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
static int update_shares_cpu(struct task_group *tg, int cpu)
{
        struct cfs_rq *cfs_rq;
        unsigned long flags;
        struct rq *rq;

        if (!tg->se[cpu])
                return 0;

        rq = cpu_rq(cpu);
        cfs_rq = tg->cfs_rq[cpu];

        raw_spin_lock_irqsave(&rq->lock, flags);

        update_rq_clock(rq);
        update_cfs_load(cfs_rq, 1);

        /*
         * We need to update shares after updating tg->load_weight in
         * order to adjust the weight of groups with long running tasks.
         */
        update_cfs_shares(cfs_rq);

        raw_spin_unlock_irqrestore(&rq->lock, flags);

        return 0;
}

static void update_shares(int cpu)
{
        struct cfs_rq *cfs_rq;
        struct rq *rq = cpu_rq(cpu);

        rcu_read_lock();
        /*
         * Iterates the task_group tree in a bottom up fashion, see
         * list_add_leaf_cfs_rq() for details.
         */
        for_each_leaf_cfs_rq(rq, cfs_rq) {
                /* throttled entities do not contribute to load */
                if (throttled_hierarchy(cfs_rq))
                        continue;

                update_shares_cpu(cfs_rq->tg, cpu);
        }
        rcu_read_unlock();
}

/*
 * Compute the cpu's hierarchical load factor for each task group.
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
static int tg_load_down(struct task_group *tg, void *data)
{
        unsigned long load;
        long cpu = (long)data;

        if (!tg->parent) {
                load = cpu_rq(cpu)->load.weight;
        } else {
                load = tg->parent->cfs_rq[cpu]->h_load;
                load *= tg->se[cpu]->load.weight;
                load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
        }

        tg->cfs_rq[cpu]->h_load = load;

        return 0;
}

static void update_h_load(long cpu)
{
        rcu_read_lock();
        walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
        rcu_read_unlock();
}

static unsigned long task_h_load(struct task_struct *p)
{
        struct cfs_rq *cfs_rq = task_cfs_rq(p);
        unsigned long load;

        load = p->se.load.weight;
        load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);

        return load;
}
#else
static inline void update_shares(int cpu)
{
}

static inline void update_h_load(long cpu)
{
}

static unsigned long task_h_load(struct task_struct *p)
{
        return p->se.load.weight;
}
#endif

/********** Helpers for find_busiest_group ************************/
/*
 * 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 *this;  /* Local group in this sd */
        unsigned long total_load;  /* Total load of all groups in sd */
        unsigned long total_pwr;   /*   Total power of all groups in sd */
        unsigned long avg_load;    /* Average load across all groups in sd */

        /** Statistics of this group */
        unsigned long this_load;
        unsigned long this_load_per_task;
        unsigned long this_nr_running;
        unsigned long this_has_capacity;
        unsigned int  this_idle_cpus;

        /* Statistics of the busiest group */
        unsigned int  busiest_idle_cpus;
        unsigned long max_load;
        unsigned long busiest_load_per_task;
        unsigned long busiest_nr_running;
        unsigned long busiest_group_capacity;
        unsigned long busiest_has_capacity;
        unsigned int  busiest_group_weight;

        int group_imb; /* Is there imbalance in this sd */
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
        int power_savings_balance; /* Is powersave balance needed for this sd */
        struct sched_group *group_min; /* Least loaded group in sd */
        struct sched_group *group_leader; /* Group which relieves group_min */
        unsigned long min_load_per_task; /* load_per_task in group_min */
        unsigned long leader_nr_running; /* Nr running of group_leader */
        unsigned long min_nr_running; /* Nr running of group_min */
#endif
};

/*
 * 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_nr_running; /* Nr tasks running in the group */
        unsigned long sum_weighted_load; /* Weighted load of group's tasks */
        unsigned long group_capacity;
        unsigned long idle_cpus;
        unsigned long group_weight;
        int group_imb; /* Is there an imbalance in the group ? */
        int group_has_capacity; /* Is there extra capacity in the group? */
};

/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
 */
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;
}


#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/**
 * init_sd_power_savings_stats - Initialize power savings statistics for
 * the given sched_domain, during load balancing.
 *
 * @sd: Sched domain whose power-savings statistics are to be initialized.
 * @sds: Variable containing the statistics for sd.
 * @idle: Idle status of the CPU at which we're performing load-balancing.
 */
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
        struct sd_lb_stats *sds, enum cpu_idle_type idle)
{
        /*
         * Busy processors will not participate in power savings
         * balance.
         */
        if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
                sds->power_savings_balance = 0;
        else {
                sds->power_savings_balance = 1;
                sds->min_nr_running = ULONG_MAX;
                sds->leader_nr_running = 0;
        }
}

/**
 * update_sd_power_savings_stats - Update the power saving stats for a
 * sched_domain while performing load balancing.
 *
 * @group: sched_group belonging to the sched_domain under consideration.
 * @sds: Variable containing the statistics of the sched_domain
 * @local_group: Does group contain the CPU for which we're performing
 *              load balancing ?
 * @sgs: Variable containing the statistics of the group.
 */
static inline void update_sd_power_savings_stats(struct sched_group *group,
        struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
{

        if (!sds->power_savings_balance)
                return;

        /*
         * If the local group is idle or completely loaded
         * no need to do power savings balance at this domain
         */
        if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
                                !sds->this_nr_running))
                sds->power_savings_balance = 0;

        /*
         * If a group is already running at full capacity or idle,
         * don't include that group in power savings calculations
         */
        if (!sds->power_savings_balance ||
                sgs->sum_nr_running >= sgs->group_capacity ||
                !sgs->sum_nr_running)
                return;

        /*
         * Calculate the group which has the least non-idle load.
         * This is the group from where we need to pick up the load
         * for saving power
         */
        if ((sgs->sum_nr_running < sds->min_nr_running) ||
            (sgs->sum_nr_running == sds->min_nr_running &&
             group_first_cpu(group) > group_first_cpu(sds->group_min))) {
                sds->group_min = group;
                sds->min_nr_running = sgs->sum_nr_running;
                sds->min_load_per_task = sgs->sum_weighted_load /
                                                sgs->sum_nr_running;
        }

        /*
         * Calculate the group which is almost near its
         * capacity but still has some space to pick up some load
         * from other group and save more power
         */
        if (sgs->sum_nr_running + 1 > sgs->group_capacity)