From patchwork Tue Aug 28 13:53:12 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Bellasi X-Patchwork-Id: 10578595 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 E4EC9139B for ; Tue, 28 Aug 2018 14:02:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D5AF42A336 for ; Tue, 28 Aug 2018 14:02:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C931C2A34E; Tue, 28 Aug 2018 14:02:32 +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 121922A336 for ; Tue, 28 Aug 2018 14:02:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727273AbeH1RyU (ORCPT ); Tue, 28 Aug 2018 13:54:20 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38752 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726439AbeH1RyU (ORCPT ); Tue, 28 Aug 2018 13:54:20 -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 563A7ED1; Tue, 28 Aug 2018 06:54:11 -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 64BDF3F5BD; Tue, 28 Aug 2018 06:54:08 -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 04/16] sched/core: uclamp: update CPU's refcount on clamp changes Date: Tue, 28 Aug 2018 14:53:12 +0100 Message-Id: <20180828135324.21976-5-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 Utilization clamp values enforced on a CPU by a task can be updated at run-time, for example via a sched_setattr syscall, while a task is currently RUNNABLE on that CPU. In these cases, the task can be already refcounting a clamp group for its CPU and thus we need to update this reference to ensure the new constraints are immediately enforced. Since a clamp value change always implies a clamp group refcount update, this patch hooks into the clamp group refcount getter to trigger a CPU refcount syncup. Such a syncup is required only by currently RUNNABLE tasks which are also referencing at least one valid clamp group. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Paul Turner Cc: Suren Baghdasaryan Cc: Todd Kjos Cc: Joel Fernandes 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: Message-ID: <20180816132249.GA2960@e110439-lin> - inline uclamp_task_active() code into uclamp_task_update_active() - get rid of the now unused uclamp_task_active() Other: - allow to call uclamp_group_get() without a task pointer, which is used to refcount the initial clamp group for all the global objects (init_task, root_task_group and system_defaults) - rebased on v4.19-rc1 Changes in v3: Message-ID: - rename UCLAMP_NONE into UCLAMP_NOT_VALID Other: - rabased on tip/sched/core Changes in v2: Message-ID: <20180413111900.GF4082@hirez.programming.kicks-ass.net> - get rid of the group_id back annotation which is not requires at this stage where we have only per-task clamping support. It will be introduce later when CGroups support is added. Other: - rabased on v4.18-rc4 - this code has been split from a previous patch to simplify the review --- kernel/sched/core.c | 65 ++++++++++++++++++++++++++++++++++++++++---- kernel/sched/sched.h | 16 +++++++++++ 2 files changed, 76 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8f908035701f..64e5c96bfdaf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1080,6 +1080,54 @@ static inline void uclamp_cpu_put(struct rq *rq, struct task_struct *p) uclamp_cpu_put_id(p, rq, clamp_id); } +/** + * uclamp_task_update_active: update the clamp group of a RUNNABLE task + * @p: the task which clamp groups must be updated + * @clamp_id: the clamp index to consider + * @group_id: the clamp group to update + * + * Each time the clamp value of a task group is changed, the old and new clamp + * groups have to be updated for each CPU containing a RUNNABLE task belonging + * to this tasks group. Sleeping tasks are not updated since they will be + * enqueued with the proper clamp group index at their next activation. + */ +static inline void +uclamp_task_update_active(struct task_struct *p, int clamp_id, int group_id) +{ + struct rq_flags rf; + struct rq *rq; + + /* + * Lock the task and the CPU where the task is (or was) queued. + * + * We might lock the (previous) RQ of a !RUNNABLE task, but that's the + * price to pay to safely serialize util_{min,max} updates with + * enqueues, dequeues and migration operations. + * This is the same locking schema used by __set_cpus_allowed_ptr(). + */ + rq = task_rq_lock(p, &rf); + + /* + * The setting of the clamp group is serialized by task_rq_lock(). + * Thus, if the task is not yet RUNNABLE and its task_struct is not + * affecting a valid clamp group, then the next time it's going to be + * enqueued it will already see the updated clamp group value. + */ + if (!task_on_rq_queued(p) && !p->on_cpu) + goto done; + if (!uclamp_task_affects(p, clamp_id)) + goto done; + + /* Release p's currently referenced clamp group */ + uclamp_cpu_put_id(p, rq, clamp_id); + + /* Get p's new clamp group */ + uclamp_cpu_get_id(p, rq, clamp_id); + +done: + task_rq_unlock(rq, p, &rf); +} + /** * uclamp_group_put: decrease the reference count for a clamp group * @clamp_id: the clamp index which was affected by a task group @@ -1115,6 +1163,7 @@ static inline void uclamp_group_put(int clamp_id, int group_id) /** * uclamp_group_get: increase the reference count for a clamp group + * @p: the task 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 @@ -1125,7 +1174,8 @@ static inline void uclamp_group_put(int clamp_id, int group_id) * this new clamp value. The corresponding clamp group index will be used by * the task to reference count the clamp value on CPUs while enqueued. */ -static inline void uclamp_group_get(int clamp_id, int next_group_id, +static inline void uclamp_group_get(struct task_struct *p, + int clamp_id, int next_group_id, struct uclamp_se *uc_se, unsigned int clamp_value) { @@ -1144,6 +1194,10 @@ static inline void uclamp_group_get(int clamp_id, int next_group_id, uc_map[next_group_id].se_count += 1; raw_spin_unlock_irqrestore(&uc_map[next_group_id].se_lock, flags); + /* Update CPU's clamp group refcounts of RUNNABLE task */ + if (p) + uclamp_task_update_active(p, clamp_id, next_group_id); + /* Release the previous clamp group */ uclamp_group_put(clamp_id, prev_group_id); } @@ -1202,12 +1256,12 @@ 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(UCLAMP_MIN, group_id[UCLAMP_MIN], + uclamp_group_get(p, 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(UCLAMP_MAX, group_id[UCLAMP_MAX], + uclamp_group_get(p, UCLAMP_MAX, group_id[UCLAMP_MAX], uc_se, attr->sched_util_max); } @@ -1255,7 +1309,7 @@ static void uclamp_fork(struct task_struct *p, bool reset) } p->uclamp[clamp_id].group_id = UCLAMP_NOT_VALID; - uclamp_group_get(clamp_id, next_group_id, uc_se, + uclamp_group_get(NULL, clamp_id, next_group_id, uc_se, p->uclamp[clamp_id].value); } } @@ -1289,7 +1343,8 @@ 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(clamp_id, 0, uc_se, uclamp_none(clamp_id)); + uclamp_group_get(NULL, clamp_id, 0, uc_se, + uclamp_none(clamp_id)); } } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 513608ae4908..25d1d218ae10 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2210,6 +2210,22 @@ static inline bool uclamp_group_active(struct uclamp_group *uc_grp, { return uc_grp[group_id].tasks > 0; } + +/** + * uclamp_task_affects: check if a task affects a utilization clamp + * @p: the task to consider + * @clamp_id: the utilization clamp to check + * + * A task affects a clamp index if: + * - it's currently enqueued on a CPU + * - it references a valid clamp group index for the specified clamp index + * + * Return: true if p currently affects the specified clamp_id + */ +static inline bool uclamp_task_affects(struct task_struct *p, int clamp_id) +{ + return (p->uclamp[clamp_id].group_id != UCLAMP_NOT_VALID); +} #endif /* CONFIG_UCLAMP_TASK */ #ifdef CONFIG_CPU_FREQ