From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85660C17441 for ; Mon, 11 Nov 2019 09:33:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 657F520856 for ; Mon, 11 Nov 2019 09:33:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727319AbfKKJdE (ORCPT ); Mon, 11 Nov 2019 04:33:04 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:55822 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727089AbfKKJc6 (ORCPT ); Mon, 11 Nov 2019 04:32:58 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iU63o-00039Q-5Y; Mon, 11 Nov 2019 10:32:36 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id BCCD31C03AB; Mon, 11 Nov 2019 10:32:35 +0100 (CET) Date: Mon, 11 Nov 2019 09:32:35 -0000 From: "tip-bot2 for Peter Zijlstra" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/core: Optimize pick_next_task() Cc: "Peter Zijlstra (Intel)" , Linus Torvalds , Thomas Gleixner , bsegall@google.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, ktkhai@virtuozzo.com, mgorman@suse.de, qais.yousef@arm.com, qperret@google.com, rostedt@goodmis.org, valentin.schneider@arm.com, vincent.guittot@linaro.org, Ingo Molnar , Borislav Petkov , linux-kernel@vger.kernel.org In-Reply-To: <20191108131909.603037345@infradead.org> References: <20191108131909.603037345@infradead.org> MIME-Version: 1.0 Message-ID: <157346475546.29376.4590888474085572805.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 5d7d605642b28a5911198a405a6072f091bfbee6 Gitweb: https://git.kernel.org/tip/5d7d605642b28a5911198a405a6072f091bfbee6 Author: Peter Zijlstra AuthorDate: Fri, 08 Nov 2019 14:15:57 +01:00 Committer: Ingo Molnar CommitterDate: Mon, 11 Nov 2019 08:35:19 +01:00 sched/core: Optimize pick_next_task() Ever since we moved the sched_class definitions into their own files, the constant expression {fair,idle}_sched_class.pick_next_task() is not in fact a compile time constant anymore and results in an indirect call (barring LTO). Fix that by exposing pick_next_task_{fair,idle}() directly, this gets rid of the indirect call (and RETPOLINE) on the fast path. Also remove the unlikely() from the idle case, it is in fact /the/ way we select idle -- and that is a very common thing to do. Performance for will-it-scale/sched_yield improves by 2% (as reported by 0-day). Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: juri.lelli@redhat.com Cc: ktkhai@virtuozzo.com Cc: mgorman@suse.de Cc: qais.yousef@arm.com Cc: qperret@google.com Cc: rostedt@goodmis.org Cc: valentin.schneider@arm.com Cc: vincent.guittot@linaro.org Link: https://lkml.kernel.org/r/20191108131909.603037345@infradead.org Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 6 +++--- kernel/sched/fair.c | 2 +- kernel/sched/idle.c | 2 +- kernel/sched/sched.h | 3 +++ 4 files changed, 8 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 59c4f29..7cf6547 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3917,14 +3917,14 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) prev->sched_class == &fair_sched_class) && rq->nr_running == rq->cfs.h_nr_running)) { - p = fair_sched_class.pick_next_task(rq, prev, rf); + p = pick_next_task_fair(rq, prev, rf); if (unlikely(p == RETRY_TASK)) goto restart; /* Assumes fair_sched_class->next == idle_sched_class */ - if (unlikely(!p)) { + if (!p) { put_prev_task(rq, prev); - p = idle_sched_class.pick_next_task(rq, NULL, NULL); + p = pick_next_task_idle(rq, NULL, NULL); } return p; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c48a695..da81451 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6611,7 +6611,7 @@ preempt: set_last_buddy(se); } -static struct task_struct * +struct task_struct * pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct cfs_rq *cfs_rq = &rq->cfs; diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 179d1d4..0fdceac 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -391,7 +391,7 @@ static void set_next_task_idle(struct rq *rq, struct task_struct *next) schedstat_inc(rq->sched_goidle); } -static struct task_struct * +struct task_struct * pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct task_struct *next = rq->idle; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c8870c5..66172a3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1821,6 +1821,9 @@ static inline bool sched_fair_runnable(struct rq *rq) return rq->cfs.nr_running > 0; } +extern struct task_struct *pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); +extern struct task_struct *pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf); + #ifdef CONFIG_SMP extern void update_group_capacity(struct sched_domain *sd, int cpu);