fair.c

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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <[email protected]>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <[email protected]>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <[email protected]>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <[email protected]>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <[email protected]>
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <[email protected]>
 */

#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 (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(&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);
}

static 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) {}
static inline 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 sync = wake_flags & WF_SYNC;

    if (p->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 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;
            break;
        }

        if (tmp->flags & sd_flag)
            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
#define LBF_SOME_PINNED 0x04

struct lb_env {
    struct sched_domain *sd;

    struct rq       *src_rq;
    int         src_cpu;

    int         dst_cpu;
    struct rq       *dst_rq;

    struct cpumask      *dst_grpmask;
    int         new_dst_cpu;
    enum cpu_idle_type  idle;
    long            imbalance;
    /* The set of CPUs under consideration for load-balancing */
    struct cpumask      *cpus;

    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))) {
        int new_dst_cpu;

        schedstat_inc(p, se.statistics.nr_failed_migrations_affine);

        /*
         * Remember if this task can be migrated to any other cpu in
         * our sched_group. We may want to revisit it if we couldn't
         * meet load balance goals by pulling other tasks on src_cpu.
         *
         * Also avoid computing new_dst_cpu if we have already computed
         * one in current iteration.
         */
        if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
            return 0;

        new_dst_cpu = cpumask_first_and(env->dst_grpmask,
                        tsk_cpus_allowed(p));
        if (new_dst_cpu < nr_cpu_ids) {
            env->flags |= LBF_SOME_PINNED;
            env->new_dst_cpu = new_dst_cpu;
        }
        return 0;
    }

    /* Record that we found atleast one task that could run on dst_cpu */
    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);

static const unsigned int sched_nr_migrate_break = 32;

/*
 * move_tasks tries to move up to imbalance 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->imbalance <= 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 += sched_nr_migrate_break;
            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 (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
            goto next;

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

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

        move_task(p, env);
        pulled++;
        env->imbalance -= 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->imbalance <= 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)
{
    struct rq *rq = cpu_rq(cpu);
    unsigned long now = jiffies;

    if (rq->h_load_throttle == now)
        return;

    rq->h_load_throttle = now;

    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 */

    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 */
};

/*
 * 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? */
};

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;
}

unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
{
    return SCHED_POWER_SCALE;
}

unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
{
    return default_scale_freq_power(sd, cpu);
}

unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
    unsigned long weight = sd->span_weight;
    unsigned long smt_gain = sd->smt_gain;

    smt_gain /= weight;

    return smt_gain;
}

unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
{
    return default_scale_smt_power(sd, cpu);
}

unsigned long scale_rt_power(int cpu)
{
    struct rq *rq = cpu_rq(cpu);
    u64 total, available, age_stamp, avg;

    /*
     * Since we're reading these variables without serialization make sure
     * we read them once before doing sanity checks on them.
     */
    age_stamp = ACCESS_ONCE(rq->age_stamp);
    avg = ACCESS_ONCE(rq->rt_avg);

    total = sched_avg_period() + (rq->clock - age_stamp);

    if (unlikely(total < avg)) {
        /* Ensures that power won't end up being negative */
        available = 0;
    } else {
        available = total - avg;
    }

    if (unlikely((s64)total < SCHED_POWER_SCALE))
        total = SCHED_POWER_SCALE;

    total >>= SCHED_POWER_SHIFT;

    return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
    unsigned long weight = sd->span_weight;
    unsigned long power = SCHED_POWER_SCALE;
    struct sched_group *sdg = sd->groups;

    if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
        if (sched_feat(ARCH_POWER))
            power *= arch_scale_smt_power(sd, cpu);
        else
            power *= default_scale_smt_power(sd, cpu);

        power >>= SCHED_POWER_SHIFT;
    }

    sdg->sgp->power_orig = power;

    if (sched_feat(ARCH_POWER))
        power *= arch_scale_freq_power(sd, cpu);
    else
        power *= default_scale_freq_power(sd, cpu);

    power >>= SCHED_POWER_SHIFT;

    power *= scale_rt_power(cpu);
    power >>= SCHED_POWER_SHIFT;

    if (!power)
        power = 1;

    cpu_rq(cpu)->cpu_power = power;
    sdg->sgp->power = power;
}

void update_group_power(struct sched_domain *sd, int cpu)
{
    struct sched_domain *child = sd->child;
    struct sched_group *group, *sdg = sd->groups;
    unsigned long power;
    unsigned long interval;

    interval = msecs_to_jiffies(sd->balance_interval);
    interval = clamp(interval, 1UL, max_load_balance_interval);
    sdg->sgp->next_update = jiffies + interval;

    if (!child) {
        update_cpu_power(sd, cpu);
        return;
    }

    power = 0;

    if (child->flags & SD_OVERLAP) {
        /*
         * SD_OVERLAP domains cannot assume that child groups
         * span the current group.
         */

        for_each_cpu(cpu, sched_group_cpus(sdg))
            power += power_of(cpu);
    } else  {
        /*
         * !SD_OVERLAP domains can assume that child groups
         * span the current group.
         */ 

        group = child->groups;
        do {
            power += group->sgp->power;
            group = group->next;
        } while (group != child->groups);
    }

    sdg->sgp->power_orig = sdg->sgp->power = power;
}

/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
    /*
     * Only siblings can have significantly less than SCHED_POWER_SCALE
     */
    if (!(sd->flags & SD_SHARE_CPUPOWER))
        return 0;

    /*
     * If ~90% of the cpu_power is still there, we're good.
     */
    if (group->sgp->power * 32 > group->sgp->power_orig * 29)
        return 1;

    return 0;
}

static inline void update_sg_lb_stats(struct lb_env *env,
            struct sched_group *group, int load_idx,
            int local_group, int *balance, struct sg_lb_stats *sgs)
{
    unsigned long nr_running, max_nr_running, min_nr_running;
    unsigned long load, max_cpu_load, min_cpu_load;
    unsigned int balance_cpu = -1, first_idle_cpu = 0;
    unsigned long avg_load_per_task = 0;
    int i;

    if (local_group)
        balance_cpu = group_balance_cpu(group);

    /* Tally up the load of all CPUs in the group */
    max_cpu_load = 0;
    min_cpu_load = ~0UL;
    max_nr_running = 0;
    min_nr_running = ~0UL;

    for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
        struct rq *rq = cpu_rq(i);

        nr_running = rq->nr_running;

        /* Bias balancing toward cpus of our domain */
        if (local_group) {
            if (idle_cpu(i) && !first_idle_cpu &&
                    cpumask_test_cpu(i, sched_group_mask(group))) {
                first_idle_cpu = 1;
                balance_cpu = i;
            }

            load = target_load(i, load_idx);
        } else {
            load = source_load(i, load_idx);
            if (load > max_cpu_load)
                max_cpu_load = load;
            if (min_cpu_load > load)
                min_cpu_load = load;

            if (nr_running > max_nr_running)
                max_nr_running = nr_running;
            if (min_nr_running > nr_running)
                min_nr_running = nr_running;
        }

        sgs->group_load += load;
        sgs->sum_nr_running += nr_running;
        sgs->sum_weighted_load += weighted_cpuload(i);
        if (idle_cpu(i))
            sgs->idle_cpus++;
    }

    /*
     * First idle cpu or the first cpu(busiest) in this sched group
     * is eligible for doing load balancing at this and above
     * domains. In the newly idle case, we will allow all the cpu's
     * to do the newly idle load balance.
     */
    if (local_group) {
        if (env->idle != CPU_NEWLY_IDLE) {
            if (balance_cpu != env->dst_cpu) {
                *balance = 0;
                return;
            }
            update_group_power(env->sd, env->dst_cpu);
        } else if (time_after_eq(jiffies, group->sgp->next_update))
            update_group_power(env->sd, env->dst_cpu);
    }

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

    /*
     * Consider the group unbalanced when the imbalance is larger
     * than the average weight of a task.
     *
     * APZ: with cgroup the avg task weight can vary wildly and
     *      might not be a suitable number - should we keep a
     *      normalized nr_running number somewhere that negates
     *      the hierarchy?
     */
    if (sgs->sum_nr_running)
        avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;

    if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
        (max_nr_running - min_nr_running) > 1)
        sgs->group_imb = 1;

    sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
                        SCHED_POWER_SCALE);
    if (!sgs->group_capacity)
        sgs->group_capacity = fix_small_capacity(env->sd, group);
    sgs->group_weight = group->group_weight;

    if (sgs->group_capacity > sgs->sum_nr_running)
        sgs->group_has_capacity = 1;
}

static bool update_sd_pick_busiest(struct lb_env *env,
                   struct sd_lb_stats *sds,
                   struct sched_group *sg,
                   struct sg_lb_stats *sgs)
{
    if (sgs->avg_load <= sds->max_load)
        return false;

    if (sgs->sum_nr_running > sgs->group_capacity)
        return true;

    if (sgs->group_imb)
        return true;

    /*
     * ASYM_PACKING needs to move all the work to the lowest
     * numbered CPUs in the group, therefore mark all groups
     * higher than ourself as busy.
     */
    if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
        env->dst_cpu < group_first_cpu(sg)) {
        if (!sds->busiest)
            return true;

        if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
            return true;
    }

    return false;
}

static inline void update_sd_lb_stats(struct lb_env *env,
                    int *balance, struct sd_lb_stats *sds)
{
    struct sched_domain *child = env->sd->child;
    struct sched_group *sg = env->sd->groups;
    struct sg_lb_stats sgs;
    int load_idx, prefer_sibling = 0;

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

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

    do {
        int local_group;

        local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
        memset(&sgs, 0, sizeof(sgs));
        update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);

        if (local_group && !(*balance))
            return;

        sds->total_load += sgs.group_load;
        sds->total_pwr += sg->sgp->power;

        /*
         * In case the child domain prefers tasks go to siblings
         * first, lower the sg capacity to one so that we'll try
         * and move all the excess tasks away. We lower the capacity
         * of a group only if the local group has the capacity to fit
         * these excess tasks, i.e. nr_running < group_capacity. The
         * extra check prevents the case where you always pull from the
         * heaviest group when it is already under-utilized (possible
         * with a large weight task outweighs the tasks on the system).
         */
        if (prefer_sibling && !local_group && sds->this_has_capacity)
            sgs.group_capacity = min(sgs.group_capacity, 1UL);

        if (local_group) {
            sds->this_load = sgs.avg_load;
            sds->this = sg;
            sds->this_nr_running = sgs.sum_nr_running;
            sds->this_load_per_task = sgs.sum_weighted_load;
            sds->this_has_capacity = sgs.group_has_capacity;
            sds->this_idle_cpus = sgs.idle_cpus;
        } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
            sds->max_load = sgs.avg_load;
            sds->busiest = sg;
            sds->busiest_nr_running = sgs.sum_nr_running;
            sds->busiest_idle_cpus = sgs.idle_cpus;
            sds->busiest_group_capacity = sgs.group_capacity;
            sds->busiest_load_per_task = sgs.sum_weighted_load;
            sds->busiest_has_capacity = sgs.group_has_capacity;
            sds->busiest_group_weight = sgs.group_weight;
            sds->group_imb = sgs.group_imb;
        }

        sg = sg->next;
    } while (sg != env->sd->groups);
}

static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
{
    int busiest_cpu;

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

    if (!sds->busiest)
        return 0;

    busiest_cpu = group_first_cpu(sds->busiest);
    if (env->dst_cpu > busiest_cpu)
        return 0;

    env->imbalance = DIV_ROUND_CLOSEST(
        sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);

    return 1;
}

static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
{
    unsigned long tmp, pwr_now = 0, pwr_move = 0;
    unsigned int imbn = 2;
    unsigned long scaled_busy_load_per_task;

    if (sds->this_nr_running) {
        sds->this_load_per_task /= sds->this_nr_running;
        if (sds->busiest_load_per_task >
                sds->this_load_per_task)
            imbn = 1;
    } else {
        sds->this_load_per_task =
            cpu_avg_load_per_task(env->dst_cpu);
    }

    scaled_busy_load_per_task = sds->busiest_load_per_task
                     * SCHED_POWER_SCALE;
    scaled_busy_load_per_task /= sds->busiest->sgp->power;

    if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
            (scaled_busy_load_per_task * imbn)) {
        env->imbalance = sds->busiest_load_per_task;
        return;
    }

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

    pwr_now += sds->busiest->sgp->power *
            min(sds->busiest_load_per_task, sds->max_load);
    pwr_now += sds->this->sgp->power *
            min(sds->this_load_per_task, sds->this_load);
    pwr_now /= SCHED_POWER_SCALE;

    /* Amount of load we'd subtract */
    tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
        sds->busiest->sgp->power;
    if (sds->max_load > tmp)
        pwr_move += sds->busiest->sgp->power *
            min(sds->busiest_load_per_task, sds->max_load - tmp);

    /* Amount of load we'd add */
    if (sds->max_load * sds->busiest->sgp->power <
        sds->busiest_load_per_task * SCHED_POWER_SCALE)
        tmp = (sds->max_load * sds->busiest->sgp->power) /
            sds->this->sgp->power;
    else
        tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
            sds->this->sgp->power;
    pwr_move += sds->this->sgp->power *
            min(sds->this_load_per_task, sds->this_load + tmp);
    pwr_move /= SCHED_POWER_SCALE;

    /* Move if we gain throughput */
    if (pwr_move > pwr_now)
        env->imbalance = sds->busiest_load_per_task;
}

static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
{
    unsigned long max_pull, load_above_capacity = ~0UL;

    sds->busiest_load_per_task /= sds->busiest_nr_running;
    if (sds->group_imb) {
        sds->busiest_load_per_task =
            min(sds->busiest_load_per_task, sds->avg_load);
    }

    /*
     * In the presence of smp nice balancing, certain scenarios can have
     * max load less than avg load(as we skip the groups at or below
     * its cpu_power, while calculating max_load..)
     */
    if (sds->max_load < sds->avg_load) {
        env->imbalance = 0;
        return fix_small_imbalance(env, sds);
    }

    if (!sds->group_imb) {
        /*
         * Don't want to pull so many tasks that a group would go idle.
         */
        load_above_capacity = (sds->busiest_nr_running -
                        sds->busiest_group_capacity);

        load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);

        load_above_capacity /= sds->busiest->sgp->power;
    }

    /*
     * We're trying to get all the cpus to the average_load, so we don't
     * want to push ourselves above the average load, nor do we wish to
     * reduce the max loaded cpu below the average load. At the same time,
     * we also don't want to reduce the group load below the group capacity
     * (so that we can implement power-savings policies etc). Thus we look
     * for the minimum possible imbalance.
     * Be careful of negative numbers as they'll appear as very large values
     * with unsigned longs.
     */
    max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);

    /* How much load to actually move to equalise the imbalance */
    env->imbalance = min(max_pull * sds->busiest->sgp->power,
        (sds->avg_load - sds->this_load) * sds->this->sgp->power)
            / SCHED_POWER_SCALE;

    /*
     * if *imbalance is less than the average load per runnable task
     * there is no guarantee that any tasks will be moved so we'll have
     * a think about bumping its value to force at least one task to be
     * moved
     */
    if (env->imbalance < sds->busiest_load_per_task)
        return fix_small_imbalance(env, sds);

}

/******* find_busiest_group() helpers end here *********************/

static struct sched_group *
find_busiest_group(struct lb_env *env, int *balance)
{
    struct sd_lb_stats sds;

    memset(&sds, 0, sizeof(sds));

    /*
     * Compute the various statistics relavent for load balancing at
     * this level.
     */
    update_sd_lb_stats(env, balance, &sds);

    /*
     * this_cpu is not the appropriate cpu to perform load balancing at
     * this level.
     */
    if (!(*balance))
        goto ret;

    if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
        check_asym_packing(env, &sds))
        return sds.busiest;

    /* There is no busy sibling group to pull tasks from */
    if (!sds.busiest || sds.busiest_nr_running == 0)
        goto out_balanced;

    sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;

    /*
     * If the busiest group is imbalanced the below checks don't
     * work because they assumes all things are equal, which typically
     * isn't true due to cpus_allowed constraints and the like.
     */
    if (sds.group_imb)
        goto force_balance;

    /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
    if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
            !sds.busiest_has_capacity)
        goto force_balance;

    /*
     * If the local group is more busy than the selected busiest group
     * don't try and pull any tasks.
     */
    if (sds.this_load >= sds.max_load)
        goto out_balanced;

    /*
     * Don't pull any tasks if this group is already above the domain
     * average load.
     */
    if (sds.this_load >= sds.avg_load)
        goto out_balanced;

    if (env->idle == CPU_IDLE) {
        /*
         * This cpu is idle. If the busiest group load doesn't
         * have more tasks than the number of available cpu's and
         * there is no imbalance between this and busiest group
         * wrt to idle cpu's, it is balanced.
         */
        if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
            sds.busiest_nr_running <= sds.busiest_group_weight)
            goto out_balanced;
    } else {
        /*
         * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
         * imbalance_pct to be conservative.
         */
        if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
            goto out_balanced;
    }

force_balance:
    /* Looks like there is an imbalance. Compute it */
    calculate_imbalance(env, &sds);
    return sds.busiest;

out_balanced:
ret:
    env->imbalance = 0;
    return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
static struct rq *find_busiest_queue(struct lb_env *env,
                     struct sched_group *group)
{
    struct rq *busiest = NULL, *rq;
    unsigned long max_load = 0;
    int i;

    for_each_cpu(i, sched_group_cpus(group)) {
        unsigned long power = power_of(i);
        unsigned long capacity = DIV_ROUND_CLOSEST(power,
                               SCHED_POWER_SCALE);
        unsigned long wl;

        if (!capacity)
            capacity = fix_small_capacity(env->sd, group);

        if (!cpumask_test_cpu(i, env->cpus))
            continue;

        rq = cpu_rq(i);
        wl = weighted_cpuload(i);

        /*
         * When comparing with imbalance, use weighted_cpuload()
         * which is not scaled with the cpu power.
         */
        if (capacity && rq->nr_running == 1 && wl > env->imbalance)
            continue;

        /*
         * For the load comparisons with the other cpu's, consider
         * the weighted_cpuload() scaled with the cpu power, so that
         * the load can be moved away from the cpu that is potentially
         * running at a lower capacity.
         */
        wl = (wl * SCHED_POWER_SCALE) / power;

        if (wl > max_load) {
            max_load = wl;
            busiest = rq;
        }
    }

    return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL 512

/* Working cpumask for load_balance and load_balance_newidle. */
DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);

static int need_active_balance(struct lb_env *env)
{
    struct sched_domain *sd = env->sd;

    if (env->idle == CPU_NEWLY_IDLE) {

        /*
         * ASYM_PACKING needs to force migrate tasks from busy but
         * higher numbered CPUs in order to pack all tasks in the
         * lowest numbered CPUs.
         */
        if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
            return 1;
    }

    return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

static int active_load_balance_cpu_stop(void *data);

/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
            struct sched_domain *sd, enum cpu_idle_type idle,
            int *balance)
{
    int ld_moved, cur_ld_moved, active_balance = 0;
    int lb_iterations, max_lb_iterations;
    struct sched_group *group;
    struct rq *busiest;
    unsigned long flags;
    struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);

    struct lb_env env = {
        .sd     = sd,
        .dst_cpu    = this_cpu,
        .dst_rq     = this_rq,
        .dst_grpmask    = sched_group_cpus(sd->groups),
        .idle       = idle,
        .loop_break = sched_nr_migrate_break,
        .cpus       = cpus,
    };

    cpumask_copy(cpus, cpu_active_mask);
    max_lb_iterations = cpumask_weight(env.dst_grpmask);

    schedstat_inc(sd, lb_count[idle]);

redo:
    group = find_busiest_group(&env, balance);

    if (*balance == 0)
        goto out_balanced;

    if (!group) {
        schedstat_inc(sd, lb_nobusyg[idle]);
        goto out_balanced;
    }

    busiest = find_busiest_queue(&env, group);
    if (!busiest) {
        schedstat_inc(sd, lb_nobusyq[idle]);
        goto out_balanced;
    }

    BUG_ON(busiest == env.dst_rq);

    schedstat_add(sd, lb_imbalance[idle], env.imbalance);

    ld_moved = 0;
    lb_iterations = 1;
    if (busiest->nr_running > 1) {
        /*
         * Attempt to move tasks. If find_busiest_group has found
         * an imbalance but busiest->nr_running <= 1, the group is
         * still unbalanced. ld_moved simply stays zero, so it is
         * correctly treated as an imbalance.
         */
        env.flags |= LBF_ALL_PINNED;
        env.src_cpu   = busiest->cpu;
        env.src_rq    = busiest;
        env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);

        update_h_load(env.src_cpu);
more_balance:
        local_irq_save(flags);
        double_rq_lock(env.dst_rq, busiest);

        /*
         * cur_ld_moved - load moved in current iteration
         * ld_moved     - cumulative load moved across iterations
         */
        cur_ld_moved = move_tasks(&env);
        ld_moved += cur_ld_moved;
        double_rq_unlock(env.dst_rq, busiest);
        local_irq_restore(flags);

        if (env.flags & LBF_NEED_BREAK) {
            env.flags &= ~LBF_NEED_BREAK;
            goto more_balance;
        }

        /*
         * some other cpu did the load balance for us.
         */
        if (cur_ld_moved && env.dst_cpu != smp_processor_id())
            resched_cpu(env.dst_cpu);

        /*
         * Revisit (affine) tasks on src_cpu that couldn't be moved to
         * us and move them to an alternate dst_cpu in our sched_group
         * where they can run. The upper limit on how many times we
         * iterate on same src_cpu is dependent on number of cpus in our
         * sched_group.
         *
         * This changes load balance semantics a bit on who can move
         * load to a given_cpu. In addition to the given_cpu itself
         * (or a ilb_cpu acting on its behalf where given_cpu is
         * nohz-idle), we now have balance_cpu in a position to move
         * load to given_cpu. In rare situations, this may cause
         * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
         * _independently_ and at _same_ time to move some load to
         * given_cpu) causing exceess load to be moved to given_cpu.
         * This however should not happen so much in practice and
         * moreover subsequent load balance cycles should correct the
         * excess load moved.
         */
        if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
                lb_iterations++ < max_lb_iterations) {

            env.dst_rq   = cpu_rq(env.new_dst_cpu);
            env.dst_cpu  = env.new_dst_cpu;
            env.flags   &= ~LBF_SOME_PINNED;
            env.loop     = 0;
            env.loop_break   = sched_nr_migrate_break;
            /*
             * Go back to "more_balance" rather than "redo" since we
             * need to continue with same src_cpu.
             */
            goto more_balance;
        }

        /* All tasks on this runqueue were pinned by CPU affinity */
        if (unlikely(env.flags & LBF_ALL_PINNED)) {
            cpumask_clear_cpu(cpu_of(busiest), cpus);
            if (!cpumask_empty(cpus)) {
                env.loop = 0;
                env.loop_break = sched_nr_migrate_break;
                goto redo;
            }
            goto out_balanced;
        }
    }

    if (!ld_moved) {
        schedstat_inc(sd, lb_failed[idle]);
        /*
         * Increment the failure counter only on periodic balance.
         * We do not want newidle balance, which can be very
         * frequent, pollute the failure counter causing
         * excessive cache_hot migrations and active balances.
         */
        if (idle != CPU_NEWLY_IDLE)
            sd->nr_balance_failed++;

        if (need_active_balance(&env)) {
            raw_spin_lock_irqsave(&busiest->lock, flags);

            /* don't kick the active_load_balance_cpu_stop,
             * if the curr task on busiest cpu can't be
             * moved to this_cpu
             */
            if (!cpumask_test_cpu(this_cpu,
                    tsk_cpus_allowed(busiest->curr))) {
                raw_spin_unlock_irqrestore(&busiest->lock,
                                flags);
                env.flags |= LBF_ALL_PINNED;
                goto out_one_pinned;
            }

            /*
             * ->active_balance synchronizes accesses to
             * ->active_balance_work.  Once set, it's cleared
             * only after active load balance is finished.
             */
            if (!busiest->active_balance) {
                busiest->active_balance = 1;
                busiest->push_cpu = this_cpu;
                active_balance = 1;
            }
            raw_spin_unlock_irqrestore(&busiest->lock, flags);

            if (active_balance) {
                stop_one_cpu_nowait(cpu_of(busiest),
                    active_load_balance_cpu_stop, busiest,
                    &busiest->active_balance_work);
            }

            /*
             * We've kicked active balancing, reset the failure
             * counter.
             */
            sd->nr_balance_failed = sd->cache_nice_tries+1;
        }
    } else
        sd->nr_balance_failed = 0;

    if (likely(!active_balance)) {
        /* We were unbalanced, so reset the balancing interval */
        sd->balance_interval = sd->min_interval;
    } else {
        /*
         * If we've begun active balancing, start to back off. This
         * case may not be covered by the all_pinned logic if there
         * is only 1 task on the busy runqueue (because we don't call
         * move_tasks).
         */
        if (sd->balance_interval < sd->max_interval)
            sd->balance_interval *= 2;
    }

    goto out;

out_balanced:
    schedstat_inc(sd, lb_balanced[idle]);

    sd->nr_balance_failed = 0;

out_one_pinned:
    /* tune up the balancing interval */
    if (((env.flags & LBF_ALL_PINNED) &&
            sd->balance_interval < MAX_PINNED_INTERVAL) ||
            (sd->balance_interval < sd->max_interval))
        sd->balance_interval *= 2;

    ld_moved = 0;
out:
    return ld_moved;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
void idle_balance(int this_cpu, struct rq *this_rq)
{
    struct sched_domain *sd;
    int pulled_task = 0;
    unsigned long next_balance = jiffies + HZ;

    this_rq->idle_stamp = this_rq->clock;

    if (this_rq->avg_idle < sysctl_sched_migration_cost)
        return;

    /*
     * Drop the rq->lock, but keep IRQ/preempt disabled.
     */
    raw_spin_unlock(&this_rq->lock);

    update_shares(this_cpu);
    rcu_read_lock();
    for_each_domain(this_cpu, sd) {
        unsigned long interval;
        int balance = 1;

        if (!(sd->flags & SD_LOAD_BALANCE))
            continue;

        if (sd->flags & SD_BALANCE_NEWIDLE) {
            /* If we've pulled tasks over stop searching: */
            pulled_task = load_balance(this_cpu, this_rq,
                           sd, CPU_NEWLY_IDLE, &balance);
        }

        interval = msecs_to_jiffies(sd->balance_interval);
        if (time_after(next_balance, sd->last_balance + interval))
            next_balance = sd->last_balance + interval;
        if (pulled_task) {
            this_rq->idle_stamp = 0;
            break;
        }
    }
    rcu_read_unlock();

    raw_spin_lock(&this_rq->lock);

    if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
        /*
         * We are going idle. next_balance may be set based on
         * a busy processor. So reset next_balance.
         */
        this_rq->next_balance = next_balance;
    }
}

/*
 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
 * running tasks off the busiest CPU onto idle CPUs. It requires at
 * least 1 task to be running on each physical CPU where possible, and
 * avoids physical / logical imbalances.
 */
static int active_load_balance_cpu_stop(void *data)
{
    struct rq *busiest_rq = data;
    int busiest_cpu = cpu_of(busiest_rq);
    int target_cpu = busiest_rq->push_cpu;
    struct rq *target_rq = cpu_rq(target_cpu);
    struct sched_domain *sd;

    raw_spin_lock_irq(&busiest_rq->lock);

    /* make sure the requested cpu hasn't gone down in the meantime */
    if (unlikely(busiest_cpu != smp_processor_id() ||
             !busiest_rq->active_balance))
        goto out_unlock;

    /* Is there any task to move? */
    if (busiest_rq->nr_running <= 1)
        goto out_unlock;

    /*
     * This condition is "impossible", if it occurs
     * we need to fix it. Originally reported by
     * Bjorn Helgaas on a 128-cpu setup.
     */
    BUG_ON(busiest_rq == target_rq);

    /* move a task from busiest_rq to target_rq */
    double_lock_balance(busiest_rq, target_rq);

    /* Search for an sd spanning us and the target CPU. */
    rcu_read_lock();
    for_each_domain(target_cpu, sd) {
        if ((sd->flags & SD_LOAD_BALANCE) &&
            cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
                break;
    }

    if (likely(sd)) {
        struct lb_env env = {
            .sd     = sd,
            .dst_cpu    = target_cpu,
            .dst_rq     = target_rq,
            .src_cpu    = busiest_rq->cpu,
            .src_rq     = busiest_rq,
            .idle       = CPU_IDLE,
        };

        schedstat_inc(sd, alb_count);

        if (move_one_task(&env))
            schedstat_inc(sd, alb_pushed);
        else
            schedstat_inc(sd, alb_failed);
    }
    rcu_read_unlock();
    double_unlock_balance(busiest_rq, target_rq);
out_unlock:
    busiest_rq->active_balance = 0;
    raw_spin_unlock_irq(&busiest_rq->lock);
    return 0;
}

#ifdef CONFIG_NO_HZ
/*
 * idle load balancing details
 * - When one of the busy CPUs notice that there may be an idle rebalancing
 *   needed, they will kick the idle load balancer, which then does idle
 *   load balancing for all the idle CPUs.
 */
static struct {
    cpumask_var_t idle_cpus_mask;
    atomic_t nr_cpus;
    unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;

static inline int find_new_ilb(int call_cpu)
{
    int ilb = cpumask_first(nohz.idle_cpus_mask);

    if (ilb < nr_cpu_ids && idle_cpu(ilb))
        return ilb;

    return nr_cpu_ids;
}

/*
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
 * CPU (if there is one).
 */
static void nohz_balancer_kick(int cpu)
{
    int ilb_cpu;

    nohz.next_balance++;

    ilb_cpu = find_new_ilb(cpu);

    if (ilb_cpu >= nr_cpu_ids)
        return;

    if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
        return;
    /*
     * Use smp_send_reschedule() instead of resched_cpu().
     * This way we generate a sched IPI on the target cpu which
     * is idle. And the softirq performing nohz idle load balance
     * will be run before returning from the IPI.
     */
    smp_send_reschedule(ilb_cpu);
    return;
}

static inline void nohz_balance_exit_idle(int cpu)
{
    if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
        cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
        atomic_dec(&nohz.nr_cpus);
        clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
    }
}

static inline void set_cpu_sd_state_busy(void)
{
    struct sched_domain *sd;
    int cpu = smp_processor_id();

    if (!test_bit(NOHZ_IDLE, nohz_flags(cpu)))
        return;
    clear_bit(NOHZ_IDLE, nohz_flags(cpu));

    rcu_read_lock();
    for_each_domain(cpu, sd)
        atomic_inc(&sd->groups->sgp->nr_busy_cpus);
    rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
    struct sched_domain *sd;
    int cpu = smp_processor_id();

    if (test_bit(NOHZ_IDLE, nohz_flags(cpu)))
        return;
    set_bit(NOHZ_IDLE, nohz_flags(cpu));

    rcu_read_lock();
    for_each_domain(cpu, sd)
        atomic_dec(&sd->groups->sgp->nr_busy_cpus);
    rcu_read_unlock();
}

/*
 * This routine will record that the cpu is going idle with tick stopped.
 * This info will be used in performing idle load balancing in the future.
 */
void nohz_balance_enter_idle(int cpu)
{
    /*
     * If this cpu is going down, then nothing needs to be done.
     */
    if (!cpu_active(cpu))
        return;

    if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
        return;

    cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
    atomic_inc(&nohz.nr_cpus);
    set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
}

static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
                    unsigned long action, void *hcpu)
{
    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_DYING:
        nohz_balance_exit_idle(smp_processor_id());
        return NOTIFY_OK;
    default:
        return NOTIFY_DONE;
    }
}
#endif

static DEFINE_SPINLOCK(balancing);

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
void update_max_interval(void)
{
    max_load_balance_interval = HZ*num_online_cpus()/10;
}

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in arch_init_sched_domains.
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
    int balance = 1;
    struct rq *rq = cpu_rq(cpu);
    unsigned long interval;
    struct sched_domain *sd;
    /* Earliest time when we have to do rebalance again */
    unsigned long next_balance = jiffies + 60*HZ;
    int update_next_balance = 0;
    int need_serialize;

    update_shares(cpu);

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

        interval = sd->balance_interval;
        if (idle != CPU_IDLE)
            interval *= sd->busy_factor;

        /* scale ms to jiffies */
        interval = msecs_to_jiffies(interval);
        interval = clamp(interval, 1UL, max_load_balance_interval);

        need_serialize = sd->flags & SD_SERIALIZE;

        if (need_serialize) {
            if (!spin_trylock(&balancing))
                goto out;
        }

        if (time_after_eq(jiffies, sd->last_balance + interval)) {
            if (load_balance(cpu, rq, sd, idle, &balance)) {
                /*
                 * We've pulled tasks over so either we're no
                 * longer idle.
                 */
                idle = CPU_NOT_IDLE;
            }
            sd->last_balance = jiffies;
        }
        if (need_serialize)
            spin_unlock(&balancing);
out:
        if (time_after(next_balance, sd->last_balance + interval)) {
            next_balance = sd->last_balance + interval;
            update_next_balance = 1;
        }

        /*
         * Stop the load balance at this level. There is another
         * CPU in our sched group which is doing load balancing more
         * actively.
         */
        if (!balance)
            break;
    }
    rcu_read_unlock();

    /*
     * next_balance will be updated only when there is a need.
     * When the cpu is attached to null domain for ex, it will not be
     * updated.
     */
    if (likely(update_next_balance))
        rq->next_balance = next_balance;
}

#ifdef CONFIG_NO_HZ
/*
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
{
    struct rq *this_rq = cpu_rq(this_cpu);
    struct rq *rq;
    int balance_cpu;

    if (idle != CPU_IDLE ||
        !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
        goto end;

    for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
        if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
            continue;

        /*
         * If this cpu gets work to do, stop the load balancing
         * work being done for other cpus. Next load
         * balancing owner will pick it up.
         */
        if (need_resched())
            break;

        rq = cpu_rq(balance_cpu);

        raw_spin_lock_irq(&rq->lock);
        update_rq_clock(rq);
        update_idle_cpu_load(rq);
        raw_spin_unlock_irq(&rq->lock);

        rebalance_domains(balance_cpu, CPU_IDLE);

        if (time_after(this_rq->next_balance, rq->next_balance))
            this_rq->next_balance = rq->next_balance;
    }
    nohz.next_balance = this_rq->next_balance;
end:
    clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
}

/*
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu is the system.
 *   - This rq has more than one task.
 *   - At any scheduler domain level, this cpu's scheduler group has multiple
 *     busy cpu's exceeding the group's power.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
    unsigned long now = jiffies;
    struct sched_domain *sd;

    if (unlikely(idle_cpu(cpu)))
        return 0;

       /*
    * We may be recently in ticked or tickless idle mode. At the first
    * busy tick after returning from idle, we will update the busy stats.
    */
    set_cpu_sd_state_busy();
    nohz_balance_exit_idle(cpu);

    /*
     * None are in tickless mode and hence no need for NOHZ idle load
     * balancing.
     */
    if (likely(!atomic_read(&nohz.nr_cpus)))
        return 0;

    if (time_before(now, nohz.next_balance))
        return 0;

    if (rq->nr_running >= 2)
        goto need_kick;

    rcu_read_lock();
    for_each_domain(cpu, sd) {
        struct sched_group *sg = sd->groups;
        struct sched_group_power *sgp = sg->sgp;
        int nr_busy = atomic_read(&sgp->nr_busy_cpus);

        if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
            goto need_kick_unlock;

        if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
            && (cpumask_first_and(nohz.idle_cpus_mask,
                      sched_domain_span(sd)) < cpu))
            goto need_kick_unlock;

        if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
            break;
    }
    rcu_read_unlock();
    return 0;

need_kick_unlock:
    rcu_read_unlock();
need_kick:
    return 1;
}
#else
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
static void run_rebalance_domains(struct softirq_action *h)
{
    int this_cpu = smp_processor_id();
    struct rq *this_rq = cpu_rq(this_cpu);
    enum cpu_idle_type idle = this_rq->idle_balance ?
                        CPU_IDLE : CPU_NOT_IDLE;

    rebalance_domains(this_cpu, idle);

    /*
     * If this cpu has a pending nohz_balance_kick, then do the
     * balancing on behalf of the other idle cpus whose ticks are
     * stopped.
     */
    nohz_idle_balance(this_cpu, idle);
}

static inline int on_null_domain(int cpu)
{
    return !rcu_dereference_sched(cpu_rq(cpu)->sd);
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
void trigger_load_balance(struct rq *rq, int cpu)
{
    /* Don't need to rebalance while attached to NULL domain */
    if (time_after_eq(jiffies, rq->next_balance) &&
        likely(!on_null_domain(cpu)))
        raise_softirq(SCHED_SOFTIRQ);
#ifdef CONFIG_NO_HZ
    if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
        nohz_balancer_kick(cpu);
#endif
}

static void rq_online_fair(struct rq *rq)
{
    update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
    update_sysctl();

    /* Ensure any throttled groups are reachable by pick_next_task */
    unthrottle_offline_cfs_rqs(rq);
}

#endif /* CONFIG_SMP */

/*
 * scheduler tick hitting a task of our scheduling class:
 */
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &curr->se;

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        entity_tick(cfs_rq, se, queued);
    }
}

/*
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
 */
static void task_fork_fair(struct task_struct *p)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &p->se, *curr;
    int this_cpu = smp_processor_id();
    struct rq *rq = this_rq();
    unsigned long flags;

    raw_spin_lock_irqsave(&rq->lock, flags);

    update_rq_clock(rq);

    cfs_rq = task_cfs_rq(current);
    curr = cfs_rq->curr;

    if (unlikely(task_cpu(p) != this_cpu)) {
        rcu_read_lock();
        __set_task_cpu(p, this_cpu);
        rcu_read_unlock();
    }

    update_curr(cfs_rq);

    if (curr)
        se->vruntime = curr->vruntime;
    place_entity(cfs_rq, se, 1);

    if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
        /*
         * Upon rescheduling, sched_class::put_prev_task() will place
         * 'current' within the tree based on its new key value.
         */
        swap(curr->vruntime, se->vruntime);
        resched_task(rq->curr);
    }

    se->vruntime -= cfs_rq->min_vruntime;

    raw_spin_unlock_irqrestore(&rq->lock, flags);
}

/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
{
    if (!p->se.on_rq)
        return;

    /*
     * Reschedule if we are currently running on this runqueue and
     * our priority decreased, or if we are not currently running on
     * this runqueue and our priority is higher than the current's
     */
    if (rq->curr == p) {
        if (p->prio > oldprio)
            resched_task(rq->curr);
    } else
        check_preempt_curr(rq, p, 0);
}

static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

    /*
     * Ensure the task's vruntime is normalized, so that when its
     * switched back to the fair class the enqueue_entity(.flags=0) will
     * do the right thing.
     *
     * If it was on_rq, then the dequeue_entity(.flags=0) will already
     * have normalized the vruntime, if it was !on_rq, then only when
     * the task is sleeping will it still have non-normalized vruntime.
     */
    if (!se->on_rq && p->state != TASK_RUNNING) {
        /*
         * Fix up our vruntime so that the current sleep doesn't
         * cause 'unlimited' sleep bonus.
         */
        place_entity(cfs_rq, se, 0);
        se->vruntime -= cfs_rq->min_vruntime;
    }
}

/*
 * We switched to the sched_fair class.
 */
static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
    if (!p->se.on_rq)
        return;

    /*
     * We were most likely switched from sched_rt, so
     * kick off the schedule if running, otherwise just see
     * if we can still preempt the current task.
     */
    if (rq->curr == p)
        resched_task(rq->curr);
    else
        check_preempt_curr(rq, p, 0);
}

/* Account for a task changing its policy or group.
 *
 * This routine is mostly called to set cfs_rq->curr field when a task
 * migrates between groups/classes.
 */
static void set_curr_task_fair(struct rq *rq)
{
    struct sched_entity *se = &rq->curr->se;

    for_each_sched_entity(se) {
        struct cfs_rq *cfs_rq = cfs_rq_of(se);

        set_next_entity(cfs_rq, se);
        /* ensure bandwidth has been allocated on our new cfs_rq */
        account_cfs_rq_runtime(cfs_rq, 0);
    }
}

void init_cfs_rq(struct cfs_rq *cfs_rq)
{
    cfs_rq->tasks_timeline = RB_ROOT;
    cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
    cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void task_move_group_fair(struct task_struct *p, int on_rq)
{
    /*
     * If the task was not on the rq at the time of this cgroup movement
     * it must have been asleep, sleeping tasks keep their ->vruntime
     * absolute on their old rq until wakeup (needed for the fair sleeper
     * bonus in place_entity()).
     *
     * If it was on the rq, we've just 'preempted' it, which does convert
     * ->vruntime to a relative base.
     *
     * Make sure both cases convert their relative position when migrating
     * to another cgroup's rq. This does somewhat interfere with the
     * fair sleeper stuff for the first placement, but who cares.
     */
    /*
     * When !on_rq, vruntime of the task has usually NOT been normalized.
     * But there are some cases where it has already been normalized:
     *
     * - Moving a forked child which is waiting for being woken up by
     *   wake_up_new_task().
     * - Moving a task which has been woken up by try_to_wake_up() and
     *   waiting for actually being woken up by sched_ttwu_pending().
     *
     * To prevent boost or penalty in the new cfs_rq caused by delta
     * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
     */
    if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
        on_rq = 1;

    if (!on_rq)
        p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
    set_task_rq(p, task_cpu(p));
    if (!on_rq)
        p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
}

void free_fair_sched_group(struct task_group *tg)
{
    int i;

    destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

    for_each_possible_cpu(i) {
        if (tg->cfs_rq)
            kfree(tg->cfs_rq[i]);
        if (tg->se)
            kfree(tg->se[i]);
    }

    kfree(tg->cfs_rq);
    kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se;
    int i;

    tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
    if (!tg->cfs_rq)
        goto err;
    tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
    if (!tg->se)
        goto err;

    tg->shares = NICE_0_LOAD;

    init_cfs_bandwidth(tg_cfs_bandwidth(tg));

    for_each_possible_cpu(i) {
        cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
                      GFP_KERNEL, cpu_to_node(i));
        if (!cfs_rq)
            goto err;

        se = kzalloc_node(sizeof(struct sched_entity),
                  GFP_KERNEL, cpu_to_node(i));
        if (!se)
            goto err_free_rq;

        init_cfs_rq(cfs_rq);
        init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
    }

    return 1;

err_free_rq:
    kfree(cfs_rq);
err:
    return 0;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
    struct rq *rq = cpu_rq(cpu);
    unsigned long flags;

    /*
    * Only empty task groups can be destroyed; so we can speculatively
    * check on_list without danger of it being re-added.
    */
    if (!tg->cfs_rq[cpu]->on_list)
        return;

    raw_spin_lock_irqsave(&rq->lock, flags);
    list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
    raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
            struct sched_entity *se, int cpu,
            struct sched_entity *parent)
{
    struct rq *rq = cpu_rq(cpu);

    cfs_rq->tg = tg;
    cfs_rq->rq = rq;
#ifdef CONFIG_SMP
    /* allow initial update_cfs_load() to truncate */
    cfs_rq->load_stamp = 1;
#endif
    init_cfs_rq_runtime(cfs_rq);

    tg->cfs_rq[cpu] = cfs_rq;
    tg->se[cpu] = se;

    /* se could be NULL for root_task_group */
    if (!se)
        return;

    if (!parent)
        se->cfs_rq = &rq->cfs;
    else
        se->cfs_rq = parent->my_q;

    se->my_q = cfs_rq;
    update_load_set(&se->load, 0);
    se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
    int i;
    unsigned long flags;

    /*
     * We can't change the weight of the root cgroup.
     */
    if (!tg->se[0])
        return -EINVAL;

    shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

    mutex_lock(&shares_mutex);
    if (tg->shares == shares)
        goto done;

    tg->shares = shares;
    for_each_possible_cpu(i) {
        struct rq *rq = cpu_rq(i);
        struct sched_entity *se;

        se = tg->se[i];
        /* Propagate contribution to hierarchy */
        raw_spin_lock_irqsave(&rq->lock, flags);
        for_each_sched_entity(se)
            update_cfs_shares(group_cfs_rq(se));
        raw_spin_unlock_irqrestore(&rq->lock, flags);
    }

done:
    mutex_unlock(&shares_mutex);
    return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
    return 1;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */


static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
{
    struct sched_entity *se = &task->se;
    unsigned int rr_interval = 0;

    /*
     * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
     * idle runqueue:
     */
    if (rq->cfs.load.weight)
        rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));

    return rr_interval;
}

/*
 * All the scheduling class methods:
 */
const struct sched_class fair_sched_class = {
    .next           = &idle_sched_class,
    .enqueue_task       = enqueue_task_fair,
    .dequeue_task       = dequeue_task_fair,
    .yield_task     = yield_task_fair,
    .yield_to_task      = yield_to_task_fair,

    .check_preempt_curr = check_preempt_wakeup,

    .pick_next_task     = pick_next_task_fair,
    .put_prev_task      = put_prev_task_fair,

#ifdef CONFIG_SMP
    .select_task_rq     = select_task_rq_fair,

    .rq_online      = rq_online_fair,
    .rq_offline     = rq_offline_fair,

    .task_waking        = task_waking_fair,
#endif

    .set_curr_task          = set_curr_task_fair,
    .task_tick      = task_tick_fair,
    .task_fork      = task_fork_fair,

    .prio_changed       = prio_changed_fair,
    .switched_from      = switched_from_fair,
    .switched_to        = switched_to_fair,

    .get_rr_interval    = get_rr_interval_fair,

#ifdef CONFIG_FAIR_GROUP_SCHED
    .task_move_group    = task_move_group_fair,
#endif
};

#ifdef CONFIG_SCHED_DEBUG
void print_cfs_stats(struct seq_file *m, int cpu)
{
    struct cfs_rq *cfs_rq;

    rcu_read_lock();
    for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
        print_cfs_rq(m, cpu, cfs_rq);
    rcu_read_unlock();
}
#endif

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
    open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

#ifdef CONFIG_NO_HZ
    nohz.next_balance = jiffies;
    zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
    cpu_notifier(sched_ilb_notifier, 0);
#endif
#endif /* SMP */

}