Re: [CFS Bandwidth Control v4 1/7] sched: introduce primitives toaccount for CFS bandwidth tracking

From: Balbir Singh
Date: Wed Feb 16 2011 - 11:53:58 EST

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* Paul Turner <pjt@xxxxxxxxxx> [2011-02-15 19:18:32]:

> In this patch we introduce the notion of CFS bandwidth, to account for the
> realities of SMP this is 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_rq's can allocate from. It uses the new cfs_bandwidth
> structure.
> - The local bandwidth is tracked per-cfs_rq, this represents allotments from
> the global pool
> bandwidth assigned to a task_group, this is tracked using the
> new cfs_bandwidth structure.
>
> Bandwidth is managed via cgroupfs via two new files in 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@xxxxxxxxxx>
> Signed-off-by: Nikhil Rao <ncrao@xxxxxxxxxx>
> Signed-off-by: Bharata B Rao <bharata@xxxxxxxxxxxxxxxxxx>
> ---

Looks good, minor nits below

Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>

> init/Kconfig | 9 +
> kernel/sched.c | 264 +++++++++++++++++++++++++++++++++++++++++++++++-----
> kernel/sched_fair.c | 19 +++
> 3 files changed, 269 insertions(+), 23 deletions(-)
>
> Index: tip/init/Kconfig
> ===================================================================
> --- tip.orig/init/Kconfig
> +++ tip/init/Kconfig
> @@ -698,6 +698,15 @@ 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);
>
> +#ifdef CONFIG_CFS_BANDWIDTH
> +struct 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 +288,10 @@ struct task_group {
> #ifdef CONFIG_SCHED_AUTOGROUP
> struct autogroup *autogroup;
> #endif
> +
> +#ifdef CONFIG_CFS_BANDWIDTH
> + struct cfs_bandwidth cfs_bandwidth;
> +#endif
> };
>
> /* task_group_lock serializes the addition/removal of task groups */
> @@ -370,9 +386,76 @@ struct cfs_rq {
>
> unsigned long load_contribution;
> #endif
> +#ifdef CONFIG_CFS_BANDWIDTH
> + u64 quota_assigned, quota_used;
> +#endif
> #endif
> };
>
> +#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);

This patch just sets up to return do_sched_cfs_period_timer to return
1. I am afraid I don't understand why this function is introduced
here.

> + }
> +
> + 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_used = 0;
> + if (cfs_rq->tg->cfs_bandwidth.quota == RUNTIME_INF)
> + cfs_rq->quota_assigned = RUNTIME_INF;
> + else
> + cfs_rq->quota_assigned = 0;
> +}
> +
> +static void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
> +{
> + 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);
> +}
> +#endif
> +
> /* Real-Time classes' related field in a runqueue: */
> struct rt_rq {
> struct rt_prio_array active;
> @@ -8038,6 +8121,9 @@ static void init_tg_cfs_entry(struct tas
> tg->cfs_rq[cpu] = cfs_rq;
> init_cfs_rq(cfs_rq, rq);
> cfs_rq->tg = tg;
> +#ifdef CONFIG_CFS_BANDWIDTH
> + init_cfs_rq_quota(cfs_rq);
> +#endif
>
> tg->se[cpu] = se;
> /* se could be NULL for root_task_group */
> @@ -8173,6 +8259,10 @@ 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).
> */
> +#ifdef CONFIG_CFS_BANDWIDTH
> + init_cfs_bandwidth(&root_task_group.cfs_bandwidth,
> + RUNTIME_INF, sched_cfs_bandwidth_period);
> +#endif
> init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
> #endif /* CONFIG_FAIR_GROUP_SCHED */
>
> @@ -8415,6 +8505,10 @@ static void free_fair_sched_group(struct
> {
> int i;
>
> +#ifdef CONFIG_CFS_BANDWIDTH
> + destroy_cfs_bandwidth(&tg->cfs_bandwidth);
> +#endif
> +
> for_each_possible_cpu(i) {
> if (tg->cfs_rq)
> kfree(tg->cfs_rq[i]);
> @@ -8442,7 +8536,10 @@ int alloc_fair_sched_group(struct task_g
> goto err;
>
> tg->shares = NICE_0_LOAD;
> -
> +#ifdef CONFIG_CFS_BANDWIDTH
> + init_cfs_bandwidth(&tg->cfs_bandwidth, RUNTIME_INF,
> + sched_cfs_bandwidth_period);
> +#endif
> for_each_possible_cpu(i) {
> rq = cpu_rq(i);
>
> @@ -8822,7 +8919,7 @@ 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;
> @@ -8861,7 +8958,7 @@ 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)
> @@ -8886,7 +8983,7 @@ 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)
> @@ -9107,6 +9204,116 @@ static u64 cpu_shares_read_u64(struct cg
>
> return (u64) tg->shares;
> }
> +
> +#ifdef CONFIG_CFS_BANDWIDTH
> +static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
> +{
> + int i;
> + static DEFINE_MUTEX(mutex);
> +
> + if (tg == &root_task_group)
> + return -EINVAL;
> +
> + if (!period)
> + return -EINVAL;
> +
> + /*
> + * Ensure we have at least one tick 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 (NS_TO_JIFFIES(quota) < 1)
> + return -EINVAL;
> +
> + mutex_lock(&mutex);
> + raw_spin_lock_irq(&tg->cfs_bandwidth.lock);
> + tg->cfs_bandwidth.period = ns_to_ktime(period);
> + tg->cfs_bandwidth.runtime = tg->cfs_bandwidth.quota = quota;
> + raw_spin_unlock_irq(&tg->cfs_bandwidth.lock);
> +
> + for_each_possible_cpu(i) {

Why for each possible cpu - to avoid hotplug handling?

> + 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_runtime_us)
> +{
> + u64 quota, period;
> +
> + period = ktime_to_ns(tg->cfs_bandwidth.period);
> + if (cfs_runtime_us < 0)
> + quota = RUNTIME_INF;
> + else
> + quota = (u64)cfs_runtime_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.quota == RUNTIME_INF)
> + return -1;
> +
> + quota_us = tg->cfs_bandwidth.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.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.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
> @@ -9141,6 +9348,18 @@ 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",
> @@ -9450,4 +9669,3 @@ 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
> @@ -88,6 +88,15 @@ const_debug unsigned int sysctl_sched_mi
> */
> unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
>
> +
> +#ifdef CONFIG_CFS_BANDWIDTH
> +/*
> + * default period for cfs group bandwidth.
> + * default: 0.5s, units: nanoseconds
> + */
> +static u64 sched_cfs_bandwidth_period = 500000000ULL;
> +#endif
> +
> static const struct sched_class fair_sched_class;
>
> /**************************************************************
> @@ -397,6 +406,9 @@ static void __enqueue_entity(struct cfs_
>
> rb_link_node(&se->run_node, parent, link);
> rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
> +#ifdef CONFIG_CFS_BANDWIDTH
> + start_cfs_bandwidth(&cfs_rq->tg->cfs_bandwidth);
> +#endif
> }
>
> static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
> @@ -1369,6 +1381,13 @@ static void dequeue_task_fair(struct rq
> hrtick_update(rq);
> }
>
> +#ifdef CONFIG_CFS_BANDWIDTH
> +static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
> +{
> + return 1;
> +}
> +#endif
> +
> #ifdef CONFIG_SMP
>
> static void task_waking_fair(struct rq *rq, struct task_struct *p)
>
>

--
Three Cheers,
Balbir
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Next message: Frederic Weisbecker: "Re: Regression with dataloss: Reiserfs deadlock in 2.6.36 and2.6.37, know working 2.6.33"
Previous message: Mark Brown: "Re: platform data and mfd design question"
Next in thread: Bharata B Rao: "Re: [CFS Bandwidth Control v4 1/7] sched: introduce primitives toaccount for CFS bandwidth tracking"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]