Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753452AbbLIGUw (ORCPT ); Wed, 9 Dec 2015 01:20:52 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:36105 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752474AbbLIGTv (ORCPT ); Wed, 9 Dec 2015 01:19:51 -0500 From: Steve Muckle X-Google-Original-From: Steve Muckle To: Peter Zijlstra , Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Vincent Guittot , Morten Rasmussen , Dietmar Eggemann , Juri Lelli , Patrick Bellasi , Michael Turquette Subject: [RFCv6 PATCH 10/10] sched: rt scheduler sets capacity requirement Date: Tue, 8 Dec 2015 22:19:31 -0800 Message-Id: <1449641971-20827-11-git-send-email-smuckle@linaro.org> X-Mailer: git-send-email 2.4.10 In-Reply-To: <1449641971-20827-1-git-send-email-smuckle@linaro.org> References: <1449641971-20827-1-git-send-email-smuckle@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3026 Lines: 103 From: Vincent Guittot RT tasks don't provide any running constraints like deadline ones except their running priority. The only current usable input to estimate the capacity needed by RT tasks is the rt_avg metric. We use it to estimate the CPU capacity needed for the RT scheduler class. In order to monitor the evolution for RT task load, we must peridiocally check it during the tick. Then, we use the estimated capacity of the last activity to estimate the next one which can not be that accurate but is a good starting point without any impact on the wake up path of RT tasks. Signed-off-by: Vincent Guittot Signed-off-by: Steve Muckle --- kernel/sched/rt.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 48 insertions(+), 1 deletion(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 8ec86ab..9694204 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1426,6 +1426,41 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag #endif } +#ifdef CONFIG_SMP +static void sched_rt_update_capacity_req(struct rq *rq) +{ + u64 total, used, age_stamp, avg; + s64 delta; + + if (!sched_freq()) + return; + + sched_avg_update(rq); + /* + * Since we're reading these variables without serialization make sure + * we read them once before doing sanity checks on them. + */ + age_stamp = READ_ONCE(rq->age_stamp); + avg = READ_ONCE(rq->rt_avg); + delta = rq_clock(rq) - age_stamp; + + if (unlikely(delta < 0)) + delta = 0; + + total = sched_avg_period() + delta; + + used = div_u64(avg, total); + if (unlikely(used > SCHED_CAPACITY_SCALE)) + used = SCHED_CAPACITY_SCALE; + + set_rt_cpu_capacity(rq->cpu, 1, (unsigned long)(used)); +} +#else +static inline void sched_rt_update_capacity_req(struct rq *rq) +{ } + +#endif + static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq, struct rt_rq *rt_rq) { @@ -1494,8 +1529,17 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev) if (prev->sched_class == &rt_sched_class) update_curr_rt(rq); - if (!rt_rq->rt_queued) + if (!rt_rq->rt_queued) { + /* + * The next task to be picked on this rq will have a lower + * priority than rt tasks so we can spend some time to update + * the capacity used by rt tasks based on the last activity. + * This value will be the used as an estimation of the next + * activity. + */ + sched_rt_update_capacity_req(rq); return NULL; + } put_prev_task(rq, prev); @@ -2212,6 +2256,9 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued) update_curr_rt(rq); + if (rq->rt.rt_nr_running) + sched_rt_update_capacity_req(rq); + watchdog(rq, p); /* -- 2.4.10 -- 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/