Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753492Ab0BYIO6 (ORCPT ); Thu, 25 Feb 2010 03:14:58 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:45827 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753376Ab0BYIO4 (ORCPT ); Thu, 25 Feb 2010 03:14:56 -0500 Date: Thu, 25 Feb 2010 13:44:38 +0530 From: Bharata B Rao To: Paul Cc: linux-kernel@vger.kernel.org, Paul Menage , Srivatsa Vaddagiri , Peter Zijlstra , Gautham R Shenoy , Dhaval Giani , Balbir Singh , Herbert Poetzl , Chris Friesen , Avi Kivity , Nikhil Rao , Ingo Molnar , Kamalesh Babulal , Mike Waychison , Vaidyanathan Srinivasan , Pavel Emelyanov Subject: Re: [RFC PATCH v1 1/4] sched: introduce primitives to account for CFS bandwidth tracking Message-ID: <20100225081438.GA9640@in.ibm.com> Reply-To: bharata@linux.vnet.ibm.com References: <20100213025417.23325.90048.stgit@kitami.corp.google.com> <20100213025457.23325.69574.stgit@kitami.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100213025457.23325.69574.stgit@kitami.corp.google.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9669 Lines: 326 On Fri, Feb 12, 2010 at 06:54:57PM -0800, Paul wrote: > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -190,10 +190,28 @@ static inline int rt_bandwidth_enabled(void) > 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; > > @@ -201,22 +219,7 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b) > 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); > } > > @@ -241,6 +244,15 @@ 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 { > #ifdef CONFIG_CGROUP_SCHED > @@ -272,6 +284,10 @@ struct task_group { > struct task_group *parent; > struct list_head siblings; > struct list_head children; > + > +#ifdef CONFIG_CFS_BANDWIDTH > + struct cfs_bandwidth cfs_bandwidth; > +#endif > }; > > #ifdef CONFIG_USER_SCHED > @@ -445,9 +461,76 @@ struct cfs_rq { > */ > unsigned long rq_weight; > #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); > + } > + > + 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 May be you could define some of this functions for !CONFIG_CFS_BANDWIDTH case and avoid them calling under #ifdef ? I was given this comment during my initial iterations. > + > /* Real-Time classes' related field in a runqueue: */ > struct rt_rq { > struct rt_prio_array active; > @@ -1834,6 +1917,14 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu) > #endif > } > > +#ifdef CONFIG_CFS_BANDWIDTH > +/* > + * default period for cfs group bandwidth. > + * default: 0.5s > + */ > +static u64 sched_cfs_bandwidth_period = 500000000ULL; > +#endif > + > #include "sched_stats.h" > #include "sched_idletask.c" > #include "sched_fair.c" > @@ -9422,6 +9513,9 @@ static void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, > 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 > if (add) > list_add(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list); > > @@ -9594,6 +9688,10 @@ void __init sched_init(void) > * We achieve this by letting init_task_group's tasks sit > * directly in rq->cfs (i.e init_task_group->se[] = NULL). > */ > +#ifdef CONFIG_CFS_BANDWIDTH > + init_cfs_bandwidth(&init_task_group.cfs_bandwidth, > + RUNTIME_INF, sched_cfs_bandwidth_period); > +#endif > init_tg_cfs_entry(&init_task_group, &rq->cfs, NULL, i, 1, NULL); > #elif defined CONFIG_USER_SCHED > root_task_group.shares = NICE_0_LOAD; > @@ -9851,6 +9949,10 @@ static void free_fair_sched_group(struct task_group *tg) > { > 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]); > @@ -9878,7 +9980,10 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) > 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); > > @@ -10333,7 +10438,7 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime) > 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; > @@ -10372,7 +10477,7 @@ int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us) > 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) > @@ -10397,7 +10502,7 @@ int sched_group_set_rt_period(struct task_group *tg, long rt_period_us) > 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) > @@ -10604,6 +10709,120 @@ static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft) > > 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 == &init_task_group) > + return -EINVAL; > + > + if (!period) > + return -EINVAL; > + > + mutex_lock(&mutex); What is this mutex for ? So you essentially serializing the bandwidth setting of all groups ? While that iself isn't an issue, just wondering if cfs_bandwidth.lock isn't suffient ? > + /* > + * 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; Return with mutex held ? > + > + 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) { > + struct cfs_rq *cfs_rq = tg->cfs_rq[i]; > + struct rq *rq = rq_of(cfs_rq); > + > + raw_spin_lock_irq(&rq->lock); > + cfs_rq->quota_used = 0; > + if (quota == RUNTIME_INF) > + cfs_rq->quota_assigned = RUNTIME_INF; > + else > + cfs_rq->quota_assigned = 0; > + raw_spin_unlock_irq(&rq->lock); > + } > + mutex_unlock(&mutex); > + > + return 0; > +} > + > static void task_waking_fair(struct rq *rq, struct task_struct *p) > @@ -1172,7 +1180,7 @@ static void task_waking_fair(struct rq *rq, struct task_struct *p) > * We still saw a performance dip, some tracing learned us that between > * cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased > * significantly. Therefore try to bias the error in direction of failing > - * the affine wakeup. > + * the affie wakeup. Unintended change ? Regards, Bharata. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/