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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 2F6D8C2D0D1 for ; Thu, 19 Dec 2019 21:46:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 08E7D24679 for ; Thu, 19 Dec 2019 21:46:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727562AbfLSVqQ (ORCPT ); Thu, 19 Dec 2019 16:46:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:35764 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727460AbfLSVqA (ORCPT ); Thu, 19 Dec 2019 16:46:00 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 07B6B24687; Thu, 19 Dec 2019 21:46:00 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.92.3) (envelope-from ) id 1ii3cN-000Un0-56; Thu, 19 Dec 2019 16:45:59 -0500 Message-Id: <20191219214559.014320534@goodmis.org> User-Agent: quilt/0.65 Date: Thu, 19 Dec 2019 16:44:55 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Kirill Tkhai , Kirill Tkhai , Peter Zijlstra , "mingo@redhat.com" , "juri.lelli@redhat.com" , "vincent.guittot@linaro.org" , "dietmar.eggemann@arm.com" , "bsegall@google.com" , "mgorman@suse.de" , Ingo Molnar , Andrew Morton Subject: [RFC][PATCH 4/4] sched: Micro optimization in pick_next_task() and in check_preempt_curr() References: <20191219214451.340746474@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kirill Tkhai This introduces an optimization based on xxx_sched_class addresses in two hot scheduler functions: pick_next_task() and check_preempt_curr(). It is possible to compare pointers to sched classes to check, which of them has a higher priority, instead of current iterations using for_each_class(). One more result of the patch is that size of object file becomes a little less (excluding added BUG_ON(), which goes in __init section): $size kernel/sched/core.o text data bss dec hex filename before: 66446 18957 676 86079 1503f kernel/sched/core.o after: 66398 18957 676 86031 1500f kernel/sched/core.o Link: http://lkml.kernel.org/r/711a9c4b-ff32-1136-b848-17c622d548f3@yandex.ru Signed-off-by: Kirill Tkhai Signed-off-by: Steven Rostedt (VMware) --- kernel/sched/core.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 90e4b00ace89..63401807fcf0 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1416,20 +1416,10 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p, void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) { - const struct sched_class *class; - - if (p->sched_class == rq->curr->sched_class) { + if (p->sched_class == rq->curr->sched_class) rq->curr->sched_class->check_preempt_curr(rq, p, flags); - } else { - for_each_class(class) { - if (class == rq->curr->sched_class) - break; - if (class == p->sched_class) { - resched_curr(rq); - break; - } - } - } + else if (p->sched_class > rq->curr->sched_class) + resched_curr(rq); /* * A queue event has occurred, and we're going to schedule. In @@ -3914,8 +3904,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) * higher scheduling class, because otherwise those loose the * opportunity to pull in more work from other CPUs. */ - if (likely((prev->sched_class == &idle_sched_class || - prev->sched_class == &fair_sched_class) && + if (likely(prev->sched_class <= &fair_sched_class && rq->nr_running == rq->cfs.h_nr_running)) { p = pick_next_task_fair(rq, prev, rf); @@ -6569,6 +6558,11 @@ void __init sched_init(void) unsigned long ptr = 0; int i; + BUG_ON(&idle_sched_class > &fair_sched_class || + &fair_sched_class > &rt_sched_class || + &rt_sched_class > &dl_sched_class || + &dl_sched_class > &stop_sched_class); + wait_bit_init(); #ifdef CONFIG_FAIR_GROUP_SCHED -- 2.24.0