From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753212AbdA3L4z (ORCPT ); Mon, 30 Jan 2017 06:56:55 -0500 Received: from terminus.zytor.com ([65.50.211.136]:47638 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753348AbdA3LzG (ORCPT ); Mon, 30 Jan 2017 06:55:06 -0500 Date: Mon, 30 Jan 2017 03:54:24 -0800 From: tip-bot for Peter Zijlstra Message-ID: Cc: mingo@kernel.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, efault@gmx.de, torvalds@linux-foundation.org, peterz@infradead.org, akpm@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com Reply-To: efault@gmx.de, torvalds@linux-foundation.org, mingo@kernel.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, peterz@infradead.org, akpm@linux-foundation.org In-Reply-To: <20170119174408.GN6485@twins.programming.kicks-ass.net> References: <20170119174408.GN6485@twins.programming.kicks-ass.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/core: Optimize pick_next_task() for idle_sched_class Git-Commit-ID: 49ee576809d837442624ac18804b07943267cd57 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 49ee576809d837442624ac18804b07943267cd57 Gitweb: http://git.kernel.org/tip/49ee576809d837442624ac18804b07943267cd57 Author: Peter Zijlstra AuthorDate: Thu, 19 Jan 2017 18:44:08 +0100 Committer: Ingo Molnar CommitDate: Mon, 30 Jan 2017 11:46:34 +0100 sched/core: Optimize pick_next_task() for idle_sched_class Steve noticed that when we switch from IDLE to SCHED_OTHER we fail to take the shortcut, even though all runnable tasks are of the fair class, because prev->sched_class != &fair_sched_class. Since I reworked the put_prev_task() stuff, we don't really care about prev->class here, so removing that condition will allow this case. This increases the likely case from 78% to 98% correct for Steve's workload. Reported-by: Steven Rostedt (VMware) Tested-by: Steven Rostedt (VMware) Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170119174408.GN6485@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 49ce1cb..51ca21e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3321,15 +3321,14 @@ static inline void schedule_debug(struct task_struct *prev) static inline struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { - const struct sched_class *class = &fair_sched_class; + const struct sched_class *class; struct task_struct *p; /* * Optimization: we know that if all tasks are in * the fair class we can call that function directly: */ - if (likely(prev->sched_class == class && - rq->nr_running == rq->cfs.h_nr_running)) { + if (likely(rq->nr_running == rq->cfs.h_nr_running)) { p = fair_sched_class.pick_next_task(rq, prev, rf); if (unlikely(p == RETRY_TASK)) goto again;