From patchwork Tue Jan 15 10:15:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Patrick Bellasi X-Patchwork-Id: 10764207 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 C3AD014E5 for ; Tue, 15 Jan 2019 10:16:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B14312AFB3 for ; Tue, 15 Jan 2019 10:16:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A54FA2B175; Tue, 15 Jan 2019 10:16:32 +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 109AF2AFB3 for ; Tue, 15 Jan 2019 10:16:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728353AbfAOKQT (ORCPT ); Tue, 15 Jan 2019 05:16:19 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47044 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728950AbfAOKQS (ORCPT ); Tue, 15 Jan 2019 05:16:18 -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 3096C1596; Tue, 15 Jan 2019 02:16:17 -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 1A0A23F70D; Tue, 15 Jan 2019 02:16:13 -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 v6 15/16] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Date: Tue, 15 Jan 2019 10:15:12 +0000 Message-Id: <20190115101513.2822-16-patrick.bellasi@arm.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20190115101513.2822-1-patrick.bellasi@arm.com> References: <20190115101513.2822-1-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 a task specific clamp value is configured via sched_setattr(2), this value is accounted in the corresponding clamp bucket every time the task is {en,de}qeued. However, when cgroups are also in use, the task specific clamp values could be restricted by the task_group (TG) clamp values. Update uclamp_cpu_inc() to aggregate task and TG clamp values. Every time a task is enqueued, it's accounted in the clamp_bucket defining the smaller clamp between the task specific value and its TG effective value. This allows to: 1. ensure cgroup clamps are always used to restrict task specific requests, i.e. boosted only up to the effective granted value or clamped at least to a certain value 2. implement a "nice-like" policy, where tasks are still allowed to request less then what enforced by their current TG This mimics what already happens for a task's CPU affinity mask when the task is also in a cpuset, i.e. cgroup attributes are always used to restrict per-task attributes. Do this by exploiting the concept of "effective" clamp, which is already used by a TG to track parent enforced restrictions. Apply task group clamp restrictions only to tasks belonging to a child group. While, for tasks in the root group or in an autogroup, only system defaults are enforced. Signed-off-by: Patrick Bellasi Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Tejun Heo --- Changes in v6: Others: - wholesale s/group/bucket/ --- include/linux/sched.h | 10 ++++++++++ kernel/sched/core.c | 42 +++++++++++++++++++++++++++++++++++++++++- 2 files changed, 51 insertions(+), 1 deletion(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 3f02128fe6b2..bb4e3b1085f9 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -602,6 +602,7 @@ struct sched_dl_entity { * @bucket_id: the bucket index used by the fast-path * @mapped: the bucket index is valid * @active: the se is currently refcounted in a CPU's clamp bucket + * @user_defined: calmp value explicitly required from user-space * * A utilization clamp bucket maps a: * clamp value (value), i.e. @@ -619,12 +620,21 @@ struct sched_dl_entity { * The active bit is set whenever a task has got an effective clamp bucket * and value assigned, and it allows to know a task is actually refcounting a * CPU's clamp bucket. + * + * The user_defined bit is set whenever a task has got a task-specific clamp + * value requested from userspace, i.e. the system defaults apply to this + * task just as a restriction. This allows to relax TG's clamps when a less + * restrictive task specific value has been defined, thus allowing to + * implement a "nice" semantic when both task bucket and task specific values + * are used. For example, a task running on a 20% boosted TG can still drop + * its own boosting to 0%. */ struct uclamp_se { unsigned int value : bits_per(SCHED_CAPACITY_SCALE); unsigned int bucket_id : bits_per(UCLAMP_BUCKETS); unsigned int mapped : 1; unsigned int active : 1; + unsigned int user_defined : 1; /* * Clamp bucket and value actually used by a scheduling entity, * i.e. a (RUNNABLE) task or a task group. diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 734b769db2ca..c8d1fc9880ff 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -845,10 +845,23 @@ static inline void uclamp_cpu_update(struct rq *rq, unsigned int clamp_id, WRITE_ONCE(rq->uclamp[clamp_id].value, max_value); } +static inline bool uclamp_apply_defaults(struct task_struct *p) +{ + if (!IS_ENABLED(CONFIG_UCLAMP_TASK_GROUP)) + return true; + if (task_group_is_autogroup(task_group(p))) + return true; + if (task_group(p) == &root_task_group) + return true; + return false; +} + /* * The effective clamp bucket index of a task depends on, by increasing * priority: * - the task specific clamp value, explicitly requested from userspace + * - the task group effective clamp value, for tasks not in the root group or + * in an autogroup * - the system default clamp value, defined by the sysadmin * * As a side effect, update the task's effective value: @@ -865,6 +878,29 @@ uclamp_effective_get(struct task_struct *p, unsigned int clamp_id, *clamp_value = p->uclamp[clamp_id].value; *bucket_id = p->uclamp[clamp_id].bucket_id; + if (!uclamp_apply_defaults(p)) { +#ifdef CONFIG_UCLAMP_TASK_GROUP + unsigned int clamp_max, bucket_max; + struct uclamp_se *tg_clamp; + + tg_clamp = &task_group(p)->uclamp[clamp_id]; + clamp_max = tg_clamp->effective.value; + bucket_max = tg_clamp->effective.bucket_id; + + if (!p->uclamp[clamp_id].user_defined || + *clamp_value > clamp_max) { + *clamp_value = clamp_max; + *bucket_id = bucket_max; + } +#endif + /* + * If we have task groups and we are running in a child group, + * system default does not apply anymore since we assume task + * group clamps are properly configured. + */ + return; + } + /* RT tasks have different default values */ default_clamp = task_has_rt_policy(p) ? uclamp_default_perf @@ -1223,10 +1259,12 @@ static int __setscheduler_uclamp(struct task_struct *p, mutex_lock(&uclamp_mutex); if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { + p->uclamp[UCLAMP_MIN].user_defined = true; uclamp_bucket_inc(p, &p->uclamp[UCLAMP_MIN], UCLAMP_MIN, lower_bound); } if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) { + p->uclamp[UCLAMP_MAX].user_defined = true; uclamp_bucket_inc(p, &p->uclamp[UCLAMP_MAX], UCLAMP_MAX, upper_bound); } @@ -1259,8 +1297,10 @@ static void uclamp_fork(struct task_struct *p, bool reset) for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { unsigned int clamp_value = p->uclamp[clamp_id].value; - if (unlikely(reset)) + if (unlikely(reset)) { clamp_value = uclamp_none(clamp_id); + p->uclamp[clamp_id].user_defined = false; + } p->uclamp[clamp_id].mapped = false; p->uclamp[clamp_id].active = false;