From patchwork Fri Feb 8 10:05:41 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Bellasi X-Patchwork-Id: 10802619 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C9BF414E1 for ; Fri, 8 Feb 2019 10:06:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B948C2DC81 for ; Fri, 8 Feb 2019 10:06:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AD2C52DCD4; Fri, 8 Feb 2019 10:06:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 270DB2DC81 for ; Fri, 8 Feb 2019 10:06:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727168AbfBHKGV (ORCPT ); Fri, 8 Feb 2019 05:06:21 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47480 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726022AbfBHKGU (ORCPT ); Fri, 8 Feb 2019 05:06:20 -0500 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 DBD6D1596; Fri, 8 Feb 2019 02:06:19 -0800 (PST) Received: from e110439-lin.cambridge.arm.com (e110439-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C539C3F557; Fri, 8 Feb 2019 02:06:16 -0800 (PST) From: Patrick Bellasi To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: [PATCH v7 02/15] sched/core: uclamp: Enforce last task UCLAMP_MAX Date: Fri, 8 Feb 2019 10:05:41 +0000 Message-Id: <20190208100554.32196-3-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190208100554.32196-1-patrick.bellasi@arm.com> References: <20190208100554.32196-1-patrick.bellasi@arm.com> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When the task sleeps, it removes its max utilization clamp from its CPU. However, the blocked utilization on that CPU can be higher than the max clamp value enforced while the task was running. This allows undesired CPU frequency increases while a CPU is idle, for example, when another CPU on the same frequency domain triggers a frequency update, since schedutil can now see the full not clamped blocked utilization of the idle CPU. Fix this by using uclamp_rq_dec_id(p, rq, UCLAMP_MAX) uclamp_rq_update(rq, UCLAMP_MAX, clamp_value) to detect when a CPU has no more RUNNABLE clamped tasks and to flag this condition. Don't track any minimum utilization clamps since an idle CPU never requires a minimum frequency. The decay of the blocked utilization is good enough to reduce the CPU frequency. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra --- kernel/sched/core.c | 52 ++++++++++++++++++++++++++++++++++++++++---- kernel/sched/sched.h | 2 ++ 2 files changed, 50 insertions(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8ecf5470058c..e4f5e8c426ab 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -741,11 +741,47 @@ static inline unsigned int uclamp_none(int clamp_id) return SCHED_CAPACITY_SCALE; } -static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id) +static inline unsigned int +uclamp_idle_value(struct rq *rq, unsigned int clamp_id, unsigned int clamp_value) +{ + /* + * Avoid blocked utilization pushing up the frequency when we go + * idle (which drops the max-clamp) by retaining the last known + * max-clamp. + */ + if (clamp_id == UCLAMP_MAX) { + rq->uclamp_flags |= UCLAMP_FLAG_IDLE; + return clamp_value; + } + + return uclamp_none(UCLAMP_MIN); +} + +static inline void uclamp_idle_reset(struct rq *rq, unsigned int clamp_id, + unsigned int clamp_value) +{ + /* Reset max-clamp retention only on idle exit */ + if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE)) + return; + + WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value); + + /* + * This function is called for both UCLAMP_MIN (before) and UCLAMP_MAX + * (after). The idle flag is reset only the second time, when we know + * that UCLAMP_MIN has been already updated. + */ + if (clamp_id == UCLAMP_MAX) + rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; +} + +static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id, + unsigned int clamp_value) { struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket; unsigned int max_value = uclamp_none(clamp_id); unsigned int bucket_id; + bool active = false; /* * Both min and max clamps are MAX aggregated, thus the topmost @@ -757,9 +793,13 @@ static inline void uclamp_rq_update(struct rq *rq, unsigned int clamp_id) if (!rq->uclamp[clamp_id].bucket[bucket_id].tasks) continue; max_value = bucket[bucket_id].value; + active = true; break; } while (bucket_id); + if (unlikely(!active)) + max_value = uclamp_idle_value(rq, clamp_id, clamp_value); + WRITE_ONCE(rq->uclamp[clamp_id].value, max_value); } @@ -781,12 +821,14 @@ static inline void uclamp_rq_inc_id(struct task_struct *p, struct rq *rq, unsigned int rq_clamp, bkt_clamp, tsk_clamp; rq->uclamp[clamp_id].bucket[bucket_id].tasks++; + /* Reset clamp holds on idle exit */ + tsk_clamp = p->uclamp[clamp_id].value; + uclamp_idle_reset(rq, clamp_id, tsk_clamp); /* * Local clamping: rq's buckets always track the max "requested" * clamp value from all RUNNABLE tasks in that bucket. */ - tsk_clamp = p->uclamp[clamp_id].value; bkt_clamp = rq->uclamp[clamp_id].bucket[bucket_id].value; rq->uclamp[clamp_id].bucket[bucket_id].value = max(bkt_clamp, tsk_clamp); @@ -830,7 +872,7 @@ static inline void uclamp_rq_dec_id(struct task_struct *p, struct rq *rq, */ rq->uclamp[clamp_id].bucket[bucket_id].value = uclamp_bucket_value(rq_clamp); - uclamp_rq_update(rq, clamp_id); + uclamp_rq_update(rq, clamp_id, bkt_clamp); } } @@ -861,8 +903,10 @@ static void __init init_uclamp(void) unsigned int clamp_id; int cpu; - for_each_possible_cpu(cpu) + for_each_possible_cpu(cpu) { memset(&cpu_rq(cpu)->uclamp, 0, sizeof(struct uclamp_rq)); + cpu_rq(cpu)->uclamp_flags = 0; + } for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { unsigned int clamp_value = uclamp_none(clamp_id); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ea9e28723946..b3274b2423f8 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -880,6 +880,8 @@ struct rq { #ifdef CONFIG_UCLAMP_TASK /* Utilization clamp values based on CPU's RUNNABLE tasks */ struct uclamp_rq uclamp[UCLAMP_CNT] ____cacheline_aligned; + unsigned int uclamp_flags; +#define UCLAMP_FLAG_IDLE 0x01 #endif struct cfs_rq cfs;