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[209.132.180.67]) by mx.google.com with ESMTP id i5-v6si13356612pgg.84.2018.07.16.01.31.28; Mon, 16 Jul 2018 01:31:42 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731571AbeGPI4H (ORCPT + 99 others); Mon, 16 Jul 2018 04:56:07 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54406 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731402AbeGPI4G (ORCPT ); Mon, 16 Jul 2018 04:56:06 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 03F661682; Mon, 16 Jul 2018 01:29:51 -0700 (PDT) Received: from e110439-lin.cambridge.arm.com (e110439-lin.cambridge.arm.com [10.1.210.68]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 374123F5A0; Mon, 16 Jul 2018 01:29:48 -0700 (PDT) From: Patrick Bellasi To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: [PATCH v2 07/12] sched/core: uclamp: enforce last task UCLAMP_MAX Date: Mon, 16 Jul 2018 09:29:01 +0100 Message-Id: <20180716082906.6061-8-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180716082906.6061-1-patrick.bellasi@arm.com> References: <20180716082906.6061-1-patrick.bellasi@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a util_max clamped task sleeps, its clamp constraints are removed from the CPU. However, the blocked utilization on that CPU can still be higher than the max clamp value enforced while that task was running. This max clamp removal when a CPU is going to be idle could thus allow unwanted CPU frequency increases, right while the task is not running. This can happen, for example, where there is another (smaller) task running on a different CPU of the same frequency domain. In this case, when we aggregates the utilization of all the CPUs in a shared frequency domain, schedutil can still see the full non clamped blocked utilization of all the CPUs and thus eventually increase the frequency. Let's fix this by using: uclamp_cpu_put_id(UCLAMP_MAX) uclamp_cpu_update(last_clamp_value) to detect when a CPU has no more RUNNABLE clamped tasks and to flag this condition. Thus, while a CPU is idle, we can still enforce the last used clamp value for it. To the contrary, we do not track any UCLAMP_MIN since, while a CPU is idle, we don't want to enforce any minimum frequency Indeed, we relay just on blocked load decay to smoothly reduce the frequency. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Viresh Kumar Cc: Todd Kjos Cc: Joel Fernandes Cc: Juri Lelli Cc: Dietmar Eggemann Cc: Morten Rasmussen Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- kernel/sched/core.c | 30 ++++++++++++++++++++++++++---- kernel/sched/sched.h | 2 ++ 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b2424eea7990..0cb6e0aa4faa 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -930,7 +930,8 @@ uclamp_group_find(int clamp_id, unsigned int clamp_value) * For the specified clamp index, this method computes the new CPU utilization * clamp to use until the next change on the set of RUNNABLE tasks on that CPU. */ -static inline void uclamp_cpu_update(struct rq *rq, int clamp_id) +static inline void uclamp_cpu_update(struct rq *rq, int clamp_id, + unsigned int last_clamp_value) { struct uclamp_group *uc_grp = &rq->uclamp.group[clamp_id][0]; int max_value = UCLAMP_NONE; @@ -948,6 +949,19 @@ static inline void uclamp_cpu_update(struct rq *rq, int clamp_id) if (max_value >= SCHED_CAPACITY_SCALE) break; } + + /* + * Just for the UCLAMP_MAX value, in case there are no RUNNABLE + * task, we keep the CPU clamped to the last task's clamp value. + * This avoids frequency spikes to MAX when one CPU, with an high + * blocked utilization, sleeps and another CPU, in the same frequency + * domain, do not see anymore the clamp on the first CPU. + */ + if (clamp_id == UCLAMP_MAX && max_value == UCLAMP_NONE) { + rq->uclamp.flags |= UCLAMP_FLAG_IDLE; + max_value = last_clamp_value; + } + rq->uclamp.value[clamp_id] = max_value; } @@ -977,13 +991,21 @@ static inline void uclamp_cpu_get_id(struct task_struct *p, uc_grp = &rq->uclamp.group[clamp_id][0]; uc_grp[group_id].tasks += 1; + /* Force clamp update on idle exit */ + uc_cpu = &rq->uclamp; + clamp_value = p->uclamp[clamp_id].value; + if (unlikely(uc_cpu->flags & UCLAMP_FLAG_IDLE)) { + if (clamp_id == UCLAMP_MAX) + uc_cpu->flags &= ~UCLAMP_FLAG_IDLE; + uc_cpu->value[clamp_id] = clamp_value; + return; + } + /* * If this is the new max utilization clamp value, then we can update * straight away the CPU clamp value. Otherwise, the current CPU clamp * value is still valid and we are done. */ - uc_cpu = &rq->uclamp; - clamp_value = p->uclamp[clamp_id].value; if (uc_cpu->value[clamp_id] < clamp_value) uc_cpu->value[clamp_id] = clamp_value; } @@ -1028,7 +1050,7 @@ static inline void uclamp_cpu_put_id(struct task_struct *p, uc_cpu = &rq->uclamp; clamp_value = uc_grp[group_id].value; if (clamp_value >= uc_cpu->value[clamp_id]) - uclamp_cpu_update(rq, clamp_id); + uclamp_cpu_update(rq, clamp_id, clamp_value); } /** diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 1207add36478..7e4f10c507b7 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -783,6 +783,8 @@ struct uclamp_group { * values, i.e. no min/max clamping at all. */ struct uclamp_cpu { +#define UCLAMP_FLAG_IDLE 0x01 + int flags; int value[UCLAMP_CNT]; struct uclamp_group group[UCLAMP_CNT][CONFIG_UCLAMP_GROUPS_COUNT + 1]; }; -- 2.17.1