From patchwork Fri Aug 2 09:08:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Bellasi X-Patchwork-Id: 11073015 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 4D43413A4 for ; Fri, 2 Aug 2019 09:09:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 38FFC287C3 for ; Fri, 2 Aug 2019 09:09:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2C20B287D3; Fri, 2 Aug 2019 09:09:38 +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 A9FBC287C3 for ; Fri, 2 Aug 2019 09:09:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390881AbfHBJJR (ORCPT ); Fri, 2 Aug 2019 05:09:17 -0400 Received: from foss.arm.com ([217.140.110.172]:47094 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390876AbfHBJJQ (ORCPT ); Fri, 2 Aug 2019 05:09:16 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CD64F1596; Fri, 2 Aug 2019 02:09:15 -0700 (PDT) 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 2987A3F575; Fri, 2 Aug 2019 02:09:13 -0700 (PDT) From: Patrick Bellasi To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, cgroups@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Michal Koutny , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan , Alessio Balsini Subject: [PATCH v13 3/6] sched/core: uclamp: Propagate system defaults to root group Date: Fri, 2 Aug 2019 10:08:50 +0100 Message-Id: <20190802090853.4810-4-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190802090853.4810-1-patrick.bellasi@arm.com> References: <20190802090853.4810-1-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 The clamp values are not tunable at the level of the root task group. That's for two main reasons: - the root group represents "system resources" which are always entirely available from the cgroup standpoint. - when tuning/restricting "system resources" makes sense, tuning must be done using a system wide API which should also be available when control groups are not. When a system wide restriction is available, cgroups should be aware of its value in order to know exactly how much "system resources" are available for the subgroups. Utilization clamping supports already the concepts of: - system defaults: which define the maximum possible clamp values usable by tasks. - effective clamps: which allows a parent cgroup to constraint (maybe temporarily) its descendants without losing the information related to the values "requested" from them. Exploit these two concepts and bind them together in such a way that, whenever system default are tuned, the new values are propagated to (possibly) restrict or relax the "effective" value of nested cgroups. When cgroups are in use, force an update of all the RUNNABLE tasks. Otherwise, keep things simple and do just a lazy update next time each task will be enqueued. Do that since we assume a more strict resource control is required when cgroups are in use. This allows also to keep "effective" clamp values updated in case we need to expose them to user-space. Signed-off-by: Patrick Bellasi Acked-by: Tejun Heo Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo --- Changes in v13: Message-ID: <20190725114126.GA4130@blackbody.suse.cz> - comment rewording: update all RUNNABLE tasks on system default changes only when cgroups are in use. --- kernel/sched/core.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index de8886ce0f65..5683c8639b4a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1017,10 +1017,30 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) uclamp_rq_dec_id(rq, p, clamp_id); } +#ifdef CONFIG_UCLAMP_TASK_GROUP +static void cpu_util_update_eff(struct cgroup_subsys_state *css); +static void uclamp_update_root_tg(void) +{ + struct task_group *tg = &root_task_group; + + uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN], + sysctl_sched_uclamp_util_min, false); + uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX], + sysctl_sched_uclamp_util_max, false); + + rcu_read_lock(); + cpu_util_update_eff(&root_task_group.css); + rcu_read_unlock(); +} +#else +static void uclamp_update_root_tg(void) { } +#endif + int sysctl_sched_uclamp_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { + bool update_root_tg = false; int old_min, old_max; int result; @@ -1043,16 +1063,23 @@ int sysctl_sched_uclamp_handler(struct ctl_table *table, int write, if (old_min != sysctl_sched_uclamp_util_min) { uclamp_se_set(&uclamp_default[UCLAMP_MIN], sysctl_sched_uclamp_util_min, false); + update_root_tg = true; } if (old_max != sysctl_sched_uclamp_util_max) { uclamp_se_set(&uclamp_default[UCLAMP_MAX], sysctl_sched_uclamp_util_max, false); + update_root_tg = true; } + if (update_root_tg) + uclamp_update_root_tg(); + /* - * Updating all the RUNNABLE task is expensive, keep it simple and do - * just a lazy update at each next enqueue time. + * We update all RUNNABLE tasks only when task groups are in use. + * Otherwise, keep it simple and do just a lazy update at each next + * task enqueue time. */ + goto done; undo: