From patchwork Tue Aug 28 13:53:20 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Bellasi X-Patchwork-Id: 10578577 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 7D9E813B8 for ; Tue, 28 Aug 2018 13:55:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6E2AF2A30F for ; Tue, 28 Aug 2018 13:55:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 618492A326; Tue, 28 Aug 2018 13:55:32 +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 A18DF2A30F for ; Tue, 28 Aug 2018 13:55:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728321AbeH1RrL (ORCPT ); Tue, 28 Aug 2018 13:47:11 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38670 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727579AbeH1Rq7 (ORCPT ); Tue, 28 Aug 2018 13:46:59 -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 04C831AC1; Tue, 28 Aug 2018 06:54:37 -0700 (PDT) Received: from e110439-lin.Cambridge.arm.com (e110439-lin.emea.arm.com [10.4.12.126]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 135DB3F5BD; Tue, 28 Aug 2018 06:54:33 -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 , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: [PATCH v4 12/16] sched/core: uclamp: update CPU's refcount on TG's clamp changes Date: Tue, 28 Aug 2018 14:53:20 +0100 Message-Id: <20180828135324.21976-13-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180828135324.21976-1-patrick.bellasi@arm.com> References: <20180828135324.21976-1-patrick.bellasi@arm.com> 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 a task group refcounts a new clamp group, we need to ensure that the new clamp values are immediately enforced to all its tasks which are currently RUNNABLE. This is to ensure that all currently RUNNABLE tasks are boosted and/or clamped as requested as soon as possible. Let's ensure that, whenever a new clamp group is refcounted by a task group, all its RUNNABLE tasks are correctly accounted in their respective CPUs. We do that by slightly refactoring uclamp_group_get() to get an additional parameter *cgroup_subsys_state which, when provided, it's used to walk the list of tasks in the corresponding TGs and update the RUNNABLE ones. This is a "brute force" solution which allows to reuse the same refcount update code already used by the per-task API. That's also the only way to ensure a prompt enforcement of new clamp constraints on RUNNABLE tasks, as soon as a task group attribute is tweaked. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo Cc: Paul Turner Cc: Suren Baghdasaryan Cc: Todd Kjos Cc: Joel Fernandes Cc: Steve Muckle Cc: Juri Lelli Cc: Quentin Perret Cc: Dietmar Eggemann Cc: Morten Rasmussen Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- Changes in v4: Others: - rebased on v4.19-rc1 Changes in v3: - rebased on tip/sched/core - fixed some typos Changes in v2: - rebased on v4.18-rc4 - this code has been split from a previous patch to simplify the review --- kernel/sched/core.c | 52 ++++++++++++++++++++++++++++++++--------- kernel/sched/features.h | 5 ++++ 2 files changed, 46 insertions(+), 11 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fbc8d9fdfdbb..9ca881d1ff9e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1306,9 +1306,30 @@ static inline void uclamp_group_put(int clamp_id, int group_id) raw_spin_unlock_irqrestore(&uc_map[group_id].se_lock, flags); } +static inline void uclamp_group_get_tg(struct cgroup_subsys_state *css, + int clamp_id, unsigned int group_id) +{ + struct css_task_iter it; + struct task_struct *p; + + /* + * In lazy update mode, tasks will be accounted into the right clamp + * group the next time they will be requeued. + */ + if (unlikely(sched_feat(UCLAMP_LAZY_UPDATE))) + return; + + /* Update clamp groups for RUNNABLE tasks in this TG */ + css_task_iter_start(css, 0, &it); + while ((p = css_task_iter_next(&it))) + uclamp_task_update_active(p, clamp_id, group_id); + css_task_iter_end(&it); +} + /** * uclamp_group_get: increase the reference count for a clamp group * @p: the task which clamp value must be tracked + * @css: the task group which clamp value must be tracked * @clamp_id: the clamp index affected by the task * @next_group_id: the clamp group to refcount * @uc_se: the utilization clamp data for the task @@ -1320,6 +1341,7 @@ static inline void uclamp_group_put(int clamp_id, int group_id) * the task to reference count the clamp value on CPUs while enqueued. */ static inline void uclamp_group_get(struct task_struct *p, + struct cgroup_subsys_state *css, int clamp_id, int next_group_id, struct uclamp_se *uc_se, unsigned int clamp_value) @@ -1339,6 +1361,10 @@ static inline void uclamp_group_get(struct task_struct *p, uc_map[next_group_id].se_count += 1; raw_spin_unlock_irqrestore(&uc_map[next_group_id].se_lock, flags); + /* Newly created TG don't have tasks assigned */ + if (css) + uclamp_group_get_tg(css, clamp_id, next_group_id); + /* Update CPU's clamp group refcounts of RUNNABLE task */ if (p) uclamp_task_update_active(p, clamp_id, next_group_id); @@ -1398,12 +1424,12 @@ int sched_uclamp_handler(struct ctl_table *table, int write, /* Update each required clamp group */ if (old_min != sysctl_sched_uclamp_util_min) { uc_se = &uclamp_default[UCLAMP_MIN]; - uclamp_group_get(NULL, UCLAMP_MIN, group_id[UCLAMP_MIN], + uclamp_group_get(NULL, NULL, UCLAMP_MIN, group_id[UCLAMP_MIN], uc_se, sysctl_sched_uclamp_util_min); } if (old_max != sysctl_sched_uclamp_util_max) { uc_se = &uclamp_default[UCLAMP_MAX]; - uclamp_group_get(NULL, UCLAMP_MAX, group_id[UCLAMP_MAX], + uclamp_group_get(NULL, NULL, UCLAMP_MAX, group_id[UCLAMP_MAX], uc_se, sysctl_sched_uclamp_util_max); } goto done; @@ -1448,7 +1474,7 @@ static inline int alloc_uclamp_sched_group(struct task_group *tg, next_group_id = parent->uclamp[clamp_id].group_id; uc_se->group_id = UCLAMP_NOT_VALID; - uclamp_group_get(NULL, clamp_id, next_group_id, uc_se, + uclamp_group_get(NULL, NULL, clamp_id, next_group_id, uc_se, parent->uclamp[clamp_id].value); } @@ -1536,12 +1562,12 @@ static inline int __setscheduler_uclamp(struct task_struct *p, /* Update each required clamp group */ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { uc_se = &p->uclamp[UCLAMP_MIN]; - uclamp_group_get(p, UCLAMP_MIN, group_id[UCLAMP_MIN], + uclamp_group_get(p, NULL, UCLAMP_MIN, group_id[UCLAMP_MIN], uc_se, attr->sched_util_min); } if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) { uc_se = &p->uclamp[UCLAMP_MAX]; - uclamp_group_get(p, UCLAMP_MAX, group_id[UCLAMP_MAX], + uclamp_group_get(p, NULL, UCLAMP_MAX, group_id[UCLAMP_MAX], uc_se, attr->sched_util_max); } @@ -1593,7 +1619,7 @@ static void uclamp_fork(struct task_struct *p, bool reset) p->uclamp[clamp_id].effective.group_id = UCLAMP_NOT_VALID; p->uclamp[clamp_id].group_id = UCLAMP_NOT_VALID; - uclamp_group_get(NULL, clamp_id, next_group_id, uc_se, + uclamp_group_get(NULL, NULL, clamp_id, next_group_id, uc_se, p->uclamp[clamp_id].value); /* By default we do not want task-specific clamp values */ @@ -1631,7 +1657,7 @@ static void __init init_uclamp(void) /* Init init_task's clamp group */ uc_se = &init_task.uclamp[clamp_id]; uc_se->group_id = UCLAMP_NOT_VALID; - uclamp_group_get(NULL, clamp_id, 0, uc_se, + uclamp_group_get(NULL, NULL, clamp_id, 0, uc_se, uclamp_none(clamp_id)); /* * By default we do not want task-specific clamp values, @@ -1652,14 +1678,14 @@ static void __init init_uclamp(void) * all child groups. */ uc_se->group_id = UCLAMP_NOT_VALID; - uclamp_group_get(NULL, clamp_id, 0, uc_se, + uclamp_group_get(NULL, NULL, clamp_id, 0, uc_se, uclamp_none(UCLAMP_MAX)); #endif /* Init system defaul's clamp group */ uc_se = &uclamp_default[clamp_id]; uc_se->group_id = UCLAMP_NOT_VALID; - uclamp_group_get(NULL, clamp_id, 0, uc_se, + uclamp_group_get(NULL, NULL, clamp_id, 0, uc_se, uclamp_none(clamp_id)); } } @@ -7540,6 +7566,10 @@ static void cpu_util_update_hier(struct cgroup_subsys_state *css, uc_se->effective.value = value; uc_se->effective.group_id = group_id; + + /* Immediately updated descendants active tasks */ + if (css != top_css) + uclamp_group_get_tg(css, clamp_id, group_id); } } @@ -7579,7 +7609,7 @@ static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, /* Update TG's reference count */ uc_se = &tg->uclamp[UCLAMP_MIN]; - uclamp_group_get(NULL, UCLAMP_MIN, group_id, uc_se, min_value); + uclamp_group_get(NULL, css, UCLAMP_MIN, group_id, uc_se, min_value); out: rcu_read_unlock(); @@ -7624,7 +7654,7 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, /* Update TG's reference count */ uc_se = &tg->uclamp[UCLAMP_MAX]; - uclamp_group_get(NULL, UCLAMP_MAX, group_id, uc_se, max_value); + uclamp_group_get(NULL, css, UCLAMP_MAX, group_id, uc_se, max_value); out: rcu_read_unlock(); diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 85ae8488039c..aad826aa55f8 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -90,3 +90,8 @@ SCHED_FEAT(WA_BIAS, true) * UtilEstimation. Use estimated CPU utilization. */ SCHED_FEAT(UTIL_EST, true) + +/* + * Utilization clamping lazy update. + */ +SCHED_FEAT(UCLAMP_LAZY_UPDATE, false)