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    Subject[patch 01/15] sched: introduce primitives to account for CFS bandwidth tracking
    In this patch we introduce the notion of CFS bandwidth, partitioned into 
    globally unassigned bandwidth, and locally claimed bandwidth.

    - The global bandwidth is per task_group, it represents a pool of unclaimed
    bandwidth that cfs_rqs can allocate from.
    - The local bandwidth is tracked per-cfs_rq, this represents allotments from
    the global pool bandwidth assigned to a specific cpu.

    Bandwidth is managed via cgroupfs, adding two new interfaces to the cpu subsystem:
    - cpu.cfs_period_us : the bandwidth period in usecs
    - cpu.cfs_quota_us : the cpu bandwidth (in usecs) that this tg will be allowed
    to consume over period above.

    A per-cfs_bandwidth timer is also introduced to handle future refresh at
    period expiration. There's some minor refactoring here so that
    start_bandwidth_timer() functionality can be shared

    Signed-off-by: Paul Turner <pjt@google.com>
    Signed-off-by: Nikhil Rao <ncrao@google.com>
    Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
    ---
    init/Kconfig | 9 +
    kernel/sched.c | 277 +++++++++++++++++++++++++++++++++++++++++++++++-----
    kernel/sched_fair.c | 30 +++++
    3 files changed, 294 insertions(+), 22 deletions(-)

    Index: tip/init/Kconfig
    ===================================================================
    --- tip.orig/init/Kconfig
    +++ tip/init/Kconfig
    @@ -720,6 +720,15 @@ config FAIR_GROUP_SCHED
    depends on CGROUP_SCHED
    default CGROUP_SCHED

    +config CFS_BANDWIDTH
    + bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
    + depends on EXPERIMENTAL
    + depends on FAIR_GROUP_SCHED
    + default n
    + help
    + This option allows users to define quota and period for cpu
    + bandwidth provisioning on a per-cgroup basis.
    +
    config RT_GROUP_SCHED
    bool "Group scheduling for SCHED_RR/FIFO"
    depends on EXPERIMENTAL
    Index: tip/kernel/sched.c
    ===================================================================
    --- tip.orig/kernel/sched.c
    +++ tip/kernel/sched.c
    @@ -194,10 +194,28 @@ static inline int rt_bandwidth_enabled(v
    return sysctl_sched_rt_runtime >= 0;
    }

    -static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
    +static void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
    {
    - ktime_t now;
    + unsigned long delta;
    + ktime_t soft, hard, now;
    +
    + for (;;) {
    + if (hrtimer_active(period_timer))
    + break;

    + now = hrtimer_cb_get_time(period_timer);
    + hrtimer_forward(period_timer, now, period);
    +
    + soft = hrtimer_get_softexpires(period_timer);
    + hard = hrtimer_get_expires(period_timer);
    + delta = ktime_to_ns(ktime_sub(hard, soft));
    + __hrtimer_start_range_ns(period_timer, soft, delta,
    + HRTIMER_MODE_ABS_PINNED, 0);
    + }
    +}
    +
    +static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
    +{
    if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
    return;

    @@ -205,22 +223,7 @@ static void start_rt_bandwidth(struct rt
    return;

    raw_spin_lock(&rt_b->rt_runtime_lock);
    - for (;;) {
    - unsigned long delta;
    - ktime_t soft, hard;
    -
    - if (hrtimer_active(&rt_b->rt_period_timer))
    - break;
    -
    - now = hrtimer_cb_get_time(&rt_b->rt_period_timer);
    - hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);
    -
    - soft = hrtimer_get_softexpires(&rt_b->rt_period_timer);
    - hard = hrtimer_get_expires(&rt_b->rt_period_timer);
    - delta = ktime_to_ns(ktime_sub(hard, soft));
    - __hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,
    - HRTIMER_MODE_ABS_PINNED, 0);
    - }
    + start_bandwidth_timer(&rt_b->rt_period_timer, rt_b->rt_period);
    raw_spin_unlock(&rt_b->rt_runtime_lock);
    }

    @@ -245,6 +248,15 @@ struct cfs_rq;

    static LIST_HEAD(task_groups);

    +struct cfs_bandwidth {
    +#ifdef CONFIG_CFS_BANDWIDTH
    + raw_spinlock_t lock;
    + ktime_t period;
    + u64 runtime, quota;
    + struct hrtimer period_timer;
    +#endif
    +};
    +
    /* task group related information */
    struct task_group {
    struct cgroup_subsys_state css;
    @@ -276,6 +288,8 @@ struct task_group {
    #ifdef CONFIG_SCHED_AUTOGROUP
    struct autogroup *autogroup;
    #endif
    +
    + struct cfs_bandwidth cfs_bandwidth;
    };

    /* task_group_lock serializes the addition/removal of task groups */
    @@ -370,9 +384,90 @@ struct cfs_rq {

    unsigned long load_contribution;
    #endif
    +#ifdef CONFIG_CFS_BANDWIDTH
    + int quota_enabled;
    + s64 quota_remaining;
    +#endif
    #endif
    };

    +static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
    +{
    + return &tg->cfs_bandwidth;
    +}
    +
    +#ifdef CONFIG_CFS_BANDWIDTH
    +static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
    +
    +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;
    +}
    +
    +static
    +void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, u64 quota, u64 period)
    +{
    + raw_spin_lock_init(&cfs_b->lock);
    + cfs_b->quota = cfs_b->runtime = quota;
    + cfs_b->period = ns_to_ktime(period);
    +
    + hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    + cfs_b->period_timer.function = sched_cfs_period_timer;
    +}
    +
    +static void init_cfs_rq_quota(struct cfs_rq *cfs_rq)
    +{
    + cfs_rq->quota_remaining = 0;
    + if (tg_cfs_bandwidth(cfs_rq->tg)->quota == RUNTIME_INF)
    + cfs_rq->quota_enabled = 0;
    + else
    + cfs_rq->quota_enabled = 1;
    +}
    +
    +static void start_cfs_bandwidth(struct cfs_rq *cfs_rq)
    +{
    + struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
    +
    + if (cfs_b->quota == RUNTIME_INF)
    + return;
    +
    + if (hrtimer_active(&cfs_b->period_timer))
    + return;
    +
    + raw_spin_lock(&cfs_b->lock);
    + start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
    + raw_spin_unlock(&cfs_b->lock);
    +}
    +
    +static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
    +{
    + hrtimer_cancel(&cfs_b->period_timer);
    +}
    +#else
    +#ifdef CONFIG_FAIR_GROUP_SCHED
    +static void init_cfs_rq_quota(struct cfs_rq *cfs_rq) {}
    +void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, u64 quota, u64 period) {}
    +static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
    +#endif /* CONFIG_FAIR_GROUP_SCHED */
    +static void start_cfs_bandwidth(struct cfs_rq *cfs_rq) {}
    +#endif /* CONFIG_CFS_BANDWIDTH */
    +
    /* Real-Time classes' related field in a runqueue: */
    struct rt_rq {
    struct rt_prio_array active;
    @@ -8048,6 +8143,7 @@ static void init_tg_cfs_entry(struct tas
    tg->cfs_rq[cpu] = cfs_rq;
    init_cfs_rq(cfs_rq, rq);
    cfs_rq->tg = tg;
    + init_cfs_rq_quota(cfs_rq);

    tg->se[cpu] = se;
    /* se could be NULL for root_task_group */
    @@ -8183,6 +8279,8 @@ void __init sched_init(void)
    * We achieve this by letting root_task_group's tasks sit
    * directly in rq->cfs (i.e root_task_group->se[] = NULL).
    */
    + init_cfs_bandwidth(&root_task_group.cfs_bandwidth,
    + RUNTIME_INF, default_cfs_period());
    init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
    #endif /* CONFIG_FAIR_GROUP_SCHED */

    @@ -8425,6 +8523,8 @@ static void free_fair_sched_group(struct
    {
    int i;

    + destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
    +
    for_each_possible_cpu(i) {
    if (tg->cfs_rq)
    kfree(tg->cfs_rq[i]);
    @@ -8453,6 +8553,9 @@ int alloc_fair_sched_group(struct task_g

    tg->shares = NICE_0_LOAD;

    + init_cfs_bandwidth(tg_cfs_bandwidth(tg), RUNTIME_INF,
    + default_cfs_period());
    +
    for_each_possible_cpu(i) {
    rq = cpu_rq(i);

    @@ -8832,7 +8935,7 @@ static int __rt_schedulable(struct task_
    return walk_tg_tree(tg_schedulable, tg_nop, &data);
    }

    -static int tg_set_bandwidth(struct task_group *tg,
    +static int tg_set_rt_bandwidth(struct task_group *tg,
    u64 rt_period, u64 rt_runtime)
    {
    int i, err = 0;
    @@ -8871,7 +8974,7 @@ int sched_group_set_rt_runtime(struct ta
    if (rt_runtime_us < 0)
    rt_runtime = RUNTIME_INF;

    - return tg_set_bandwidth(tg, rt_period, rt_runtime);
    + return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
    }

    long sched_group_rt_runtime(struct task_group *tg)
    @@ -8896,7 +8999,7 @@ int sched_group_set_rt_period(struct tas
    if (rt_period == 0)
    return -EINVAL;

    - return tg_set_bandwidth(tg, rt_period, rt_runtime);
    + return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
    }

    long sched_group_rt_period(struct task_group *tg)
    @@ -9118,6 +9221,125 @@ static u64 cpu_shares_read_u64(struct cg

    return (u64) tg->shares;
    }
    +
    +#ifdef CONFIG_CFS_BANDWIDTH
    +const u64 max_cfs_quota_period = 5 * NSEC_PER_SEC; /* 5s */
    +const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
    +
    +static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
    +{
    + int i;
    + struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
    + static DEFINE_MUTEX(mutex);
    +
    + if (tg == &root_task_group)
    + return -EINVAL;
    +
    + /*
    + * Ensure we have at some amount of bandwidth every period. This is
    + * to prevent reaching a state of large arrears when throttled via
    + * entity_tick() resulting in prolonged exit starvation.
    + */
    + if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
    + return -EINVAL;
    +
    + /*
    + * Likewise, bound things on the otherside by preventing insane quota
    + * periods. This also allows us to normalize in computing quota
    + * feasibility.
    + */
    + if (period > max_cfs_quota_period)
    + return -EINVAL;
    +
    + mutex_lock(&mutex);
    + raw_spin_lock_irq(&cfs_b->lock);
    + cfs_b->period = ns_to_ktime(period);
    + cfs_b->runtime = cfs_b->quota = quota;
    + raw_spin_unlock_irq(&cfs_b->lock);
    +
    + for_each_possible_cpu(i) {
    + struct cfs_rq *cfs_rq = tg->cfs_rq[i];
    + struct rq *rq = rq_of(cfs_rq);
    +
    + raw_spin_lock_irq(&rq->lock);
    + init_cfs_rq_quota(cfs_rq);
    + raw_spin_unlock_irq(&rq->lock);
    + }
    + mutex_unlock(&mutex);
    +
    + return 0;
    +}
    +
    +int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
    +{
    + u64 quota, period;
    +
    + period = ktime_to_ns(tg_cfs_bandwidth(tg)->period);
    + if (cfs_quota_us < 0)
    + quota = RUNTIME_INF;
    + else
    + quota = (u64)cfs_quota_us * NSEC_PER_USEC;
    +
    + return tg_set_cfs_bandwidth(tg, period, quota);
    +}
    +
    +long tg_get_cfs_quota(struct task_group *tg)
    +{
    + u64 quota_us;
    +
    + if (tg_cfs_bandwidth(tg)->quota == RUNTIME_INF)
    + return -1;
    +
    + quota_us = tg_cfs_bandwidth(tg)->quota;
    + do_div(quota_us, NSEC_PER_USEC);
    + return quota_us;
    +}
    +
    +int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
    +{
    + u64 quota, period;
    +
    + period = (u64)cfs_period_us * NSEC_PER_USEC;
    + quota = tg_cfs_bandwidth(tg)->quota;
    +
    + if (period <= 0)
    + return -EINVAL;
    +
    + return tg_set_cfs_bandwidth(tg, period, quota);
    +}
    +
    +long tg_get_cfs_period(struct task_group *tg)
    +{
    + u64 cfs_period_us;
    +
    + cfs_period_us = ktime_to_ns(tg_cfs_bandwidth(tg)->period);
    + do_div(cfs_period_us, NSEC_PER_USEC);
    + return cfs_period_us;
    +}
    +
    +static s64 cpu_cfs_quota_read_s64(struct cgroup *cgrp, struct cftype *cft)
    +{
    + return tg_get_cfs_quota(cgroup_tg(cgrp));
    +}
    +
    +static int cpu_cfs_quota_write_s64(struct cgroup *cgrp, struct cftype *cftype,
    + s64 cfs_quota_us)
    +{
    + return tg_set_cfs_quota(cgroup_tg(cgrp), cfs_quota_us);
    +}
    +
    +static u64 cpu_cfs_period_read_u64(struct cgroup *cgrp, struct cftype *cft)
    +{
    + return tg_get_cfs_period(cgroup_tg(cgrp));
    +}
    +
    +static int cpu_cfs_period_write_u64(struct cgroup *cgrp, struct cftype *cftype,
    + u64 cfs_period_us)
    +{
    + return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);
    +}
    +
    +#endif /* CONFIG_CFS_BANDWIDTH */
    #endif /* CONFIG_FAIR_GROUP_SCHED */

    #ifdef CONFIG_RT_GROUP_SCHED
    @@ -9152,6 +9374,18 @@ static struct cftype cpu_files[] = {
    .write_u64 = cpu_shares_write_u64,
    },
    #endif
    +#ifdef CONFIG_CFS_BANDWIDTH
    + {
    + .name = "cfs_quota_us",
    + .read_s64 = cpu_cfs_quota_read_s64,
    + .write_s64 = cpu_cfs_quota_write_s64,
    + },
    + {
    + .name = "cfs_period_us",
    + .read_u64 = cpu_cfs_period_read_u64,
    + .write_u64 = cpu_cfs_period_write_u64,
    + },
    +#endif
    #ifdef CONFIG_RT_GROUP_SCHED
    {
    .name = "rt_runtime_us",
    @@ -9461,4 +9695,3 @@ struct cgroup_subsys cpuacct_subsys = {
    .subsys_id = cpuacct_subsys_id,
    };
    #endif /* CONFIG_CGROUP_CPUACCT */
    -
    Index: tip/kernel/sched_fair.c
    ===================================================================
    --- tip.orig/kernel/sched_fair.c
    +++ tip/kernel/sched_fair.c
    @@ -995,6 +995,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, st

    if (cfs_rq->nr_running == 1)
    list_add_leaf_cfs_rq(cfs_rq);
    +
    + start_cfs_bandwidth(cfs_rq);
    }

    static void __clear_buddies_last(struct sched_entity *se)
    @@ -1212,6 +1214,8 @@ static void put_prev_entity(struct cfs_r
    update_stats_wait_start(cfs_rq, prev);
    /* Put 'current' back into the tree. */
    __enqueue_entity(cfs_rq, prev);
    +
    + start_cfs_bandwidth(cfs_rq);
    }
    cfs_rq->curr = NULL;
    }
    @@ -1251,6 +1255,32 @@ entity_tick(struct cfs_rq *cfs_rq, struc
    }

    /**************************************************
    + * CFS bandwidth control machinery
    + */
    +
    +#ifdef CONFIG_CFS_BANDWIDTH
    +/*
    + * default period for cfs group bandwidth.
    + * default: 0.5s, units: nanoseconds
    + */
    +static inline u64 default_cfs_period(void)
    +{
    + return 500000000ULL;
    +}
    +
    +static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
    +{
    + return 1;
    +}
    +#else
    +static inline u64 default_cfs_period(void)
    +{
    + return 0;
    +}
    +#endif
    +
    +
    +/**************************************************
    * CFS operations on tasks:
    */




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