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Date: Fri, 15 Oct 2010 10:15:52 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: Bharata B Rao <bharata@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org,
Dhaval Giani <dhaval.giani@...il.com>,
Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
Srivatsa Vaddagiri <vatsa@...ibm.com>,
Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Pavel Emelyanov <xemul@...nvz.org>,
Herbert Poetzl <herbert@...hfloor.at>,
Avi Kivity <avi@...hat.com>,
Chris Friesen <cfriesen@...tel.com>,
Paul Menage <menage@...gle.com>,
Mike Waychison <mikew@...gle.com>,
Paul Turner <pjt@...gle.com>, Nikhil Rao <ncrao@...gle.com>
Subject: Re: [PATCH v3 4/7] sched: unthrottle cfs_rq(s) who ran out of quota
at period refresh
* Bharata B Rao <bharata@...ux.vnet.ibm.com> [2010-10-12 13:22:47]:
> sched: unthrottle cfs_rq(s) who ran out of quota at period refresh
>
> From: Paul Turner <pjt@...gle.com>
>
> At the start of a new period there are several actions we must take:
> - Refresh global bandwidth pool
> - Unthrottle entities who ran out of quota as refreshed bandwidth permits
>
> Unthrottled entities have the cfs_rq->throttled flag set and are re-enqueued
> into the cfs entity hierarchy.
>
Am I reading this right?
> sched_rt_period_mask() is refactored slightly into sched_bw_period_mask()
> since it is now shared by both cfs and rt bandwidth period timers.
>
> The !CONFIG_RT_GROUP_SCHED && CONFIG_SMP case has been collapsed to use
> rd->span instead of cpu_online_mask since I think that was incorrect before
> (don't want to hit cpu's outside of your root_domain for RT bandwidth).
>
> Signed-off-by: Paul Turner <pjt@...gle.com>
> Signed-off-by: Nikhil Rao <ncrao@...gle.com>
> Signed-off-by: Bharata B Rao <bharata@...ux.vnet.ibm.com>
> ---
> kernel/sched.c | 16 ++++++++++++
> kernel/sched_fair.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> kernel/sched_rt.c | 19 --------------
> 3 files changed, 84 insertions(+), 19 deletions(-)
>
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -1565,6 +1565,8 @@ static int tg_nop(struct task_group *tg,
> }
> #endif
>
> +static inline const struct cpumask *sched_bw_period_mask(void);
> +
> #ifdef CONFIG_SMP
> /* Used instead of source_load when we know the type == 0 */
> static unsigned long weighted_cpuload(const int cpu)
> @@ -1933,6 +1935,18 @@ static inline void __set_task_cpu(struct
>
> static const struct sched_class rt_sched_class;
>
> +#ifdef CONFIG_SMP
> +static inline const struct cpumask *sched_bw_period_mask(void)
> +{
> + return cpu_rq(smp_processor_id())->rd->span;
> +}
> +#else
> +static inline const struct cpumask *sched_bw_period_mask(void)
> +{
> + return cpu_online_mask;
> +}
> +#endif
> +
> #ifdef CONFIG_CFS_BANDWIDTH
> /*
> * default period for cfs group bandwidth.
> @@ -8937,6 +8951,8 @@ static int tg_set_cfs_bandwidth(struct t
>
> raw_spin_lock_irq(&rq->lock);
> init_cfs_rq_quota(cfs_rq);
> + if (cfs_rq_throttled(cfs_rq))
> + unthrottle_cfs_rq(cfs_rq);
> raw_spin_unlock_irq(&rq->lock);
> }
> mutex_unlock(&mutex);
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -268,6 +268,13 @@ find_matching_se(struct sched_entity **s
> #endif /* CONFIG_FAIR_GROUP_SCHED */
>
> #ifdef CONFIG_CFS_BANDWIDTH
> +static inline
> +struct cfs_rq *cfs_bandwidth_cfs_rq(struct cfs_bandwidth *cfs_b, int cpu)
> +{
Nit pick, but I'd call this function cfs_bandwidth_cfs_cpu_rq
> + return container_of(cfs_b, struct task_group,
> + cfs_bandwidth)->cfs_rq[cpu];
> +}
> +
> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
> {
> return &tg->cfs_bandwidth;
> @@ -1219,6 +1226,29 @@ out_throttled:
> cfs_rq->throttled = 1;
> }
>
> +static void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> +{
> + struct sched_entity *se;
> + struct rq *rq = rq_of(cfs_rq);
> +
> + se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
> +
> + cfs_rq->throttled = 0;
> + for_each_sched_entity(se) {
> + if (se->on_rq)
> + break;
> +
> + cfs_rq = cfs_rq_of(se);
> + enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
Should we really enqueue with ENQUEUE_WAKEUP - the task throttled, not
slept.
> + if (cfs_rq_throttled(cfs_rq))
> + break;
> + }
> +
> + /* determine whether we need to wake up potentally idle cpu */
> + if (rq->curr == rq->idle && rq->cfs.nr_running)
> + resched_task(rq->curr);
> +}
> +
> static void account_cfs_rq_quota(struct cfs_rq *cfs_rq,
> unsigned long delta_exec)
> {
> @@ -1241,8 +1271,44 @@ static void account_cfs_rq_quota(struct
>
> static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
> {
> - return 1;
> + int i, idle = 1;
> + u64 delta;
> + const struct cpumask *span;
> +
> + if (cfs_b->quota == RUNTIME_INF)
> + return 1;
I am afraid I don't understand how return codes are being used here.
idle is set to 1 if there are no running tasks across all CPUs. Why do
we return a 1 from here?
> +
> + /* reset group quota */
> + raw_spin_lock(&cfs_b->lock);
> + cfs_b->runtime = cfs_b->quota;
> + raw_spin_unlock(&cfs_b->lock);
> +
> + span = sched_bw_period_mask();
> + for_each_cpu(i, span) {
> + struct rq *rq = cpu_rq(i);
> + struct cfs_rq *cfs_rq = cfs_bandwidth_cfs_rq(cfs_b, i);
> +
> + if (cfs_rq->nr_running)
> + idle = 0;
> +
> + if (!cfs_rq_throttled(cfs_rq))
> + continue;
> +
> + delta = tg_request_cfs_quota(cfs_rq->tg);
> +
> + if (delta) {
> + raw_spin_lock(&rq->lock);
> + cfs_rq->quota_assigned += delta;
> +
> + if (cfs_rq->quota_used < cfs_rq->quota_assigned)
> + unthrottle_cfs_rq(cfs_rq);
> + raw_spin_unlock(&rq->lock);
> + }
> + }
> +
> + return idle;
> }
> +
> #endif
>
> #ifdef CONFIG_SMP
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -241,18 +241,6 @@ static int rt_se_boosted(struct sched_rt
> return p->prio != p->normal_prio;
> }
>
> -#ifdef CONFIG_SMP
> -static inline const struct cpumask *sched_rt_period_mask(void)
> -{
> - return cpu_rq(smp_processor_id())->rd->span;
> -}
> -#else
> -static inline const struct cpumask *sched_rt_period_mask(void)
> -{
> - return cpu_online_mask;
> -}
> -#endif
> -
> static inline
> struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
> {
> @@ -302,11 +290,6 @@ static inline int rt_rq_throttled(struct
> return rt_rq->rt_throttled;
> }
>
> -static inline const struct cpumask *sched_rt_period_mask(void)
> -{
> - return cpu_online_mask;
> -}
> -
> static inline
> struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
> {
> @@ -524,7 +507,7 @@ static int do_sched_rt_period_timer(stru
> if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
> return 1;
>
> - span = sched_rt_period_mask();
> + span = sched_bw_period_mask();
> for_each_cpu(i, span) {
> int enqueue = 0;
> struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
--
Three Cheers,
Balbir
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