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 93F72C2D0C8 for ; Tue, 17 Dec 2019 12:40:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7528824655 for ; Tue, 17 Dec 2019 12:40:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728320AbfLQMkO (ORCPT ); Tue, 17 Dec 2019 07:40:14 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:55303 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728306AbfLQMkL (ORCPT ); Tue, 17 Dec 2019 07:40:11 -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 1ihC8s-0001pj-BH; Tue, 17 Dec 2019 13:39:58 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 6C3D11C2A41; Tue, 17 Dec 2019 13:39:52 +0100 (CET) Date: Tue, 17 Dec 2019 12:39:52 -0000 From: "tip-bot2 for Cheng Jian" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Optimize select_idle_cpu Cc: Cheng Jian , "Peter Zijlstra (Intel)" , Srikar Dronamraju , Vincent Guittot , Valentin Schneider , x86 , LKML In-Reply-To: <20191213024530.28052-1-cj.chengjian@huawei.com> References: <20191213024530.28052-1-cj.chengjian@huawei.com> MIME-Version: 1.0 Message-ID: <157658639229.30329.254182650055773886.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: 60588bfa223ff675b95f866249f90616613fbe31 Gitweb: https://git.kernel.org/tip/60588bfa223ff675b95f866249f90616613fbe31 Author: Cheng Jian AuthorDate: Fri, 13 Dec 2019 10:45:30 +08:00 Committer: Peter Zijlstra CommitterDate: Tue, 17 Dec 2019 13:32:51 +01:00 sched/fair: Optimize select_idle_cpu select_idle_cpu() will scan the LLC domain for idle CPUs, it's always expensive. so the next commit : 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") introduces a way to limit how many CPUs we scan. But it consume some CPUs out of 'nr' that are not allowed for the task and thus waste our attempts. The function always return nr_cpumask_bits, and we can't find a CPU which our task is allowed to run. Cpumask may be too big, similar to select_idle_core(), use per_cpu_ptr 'select_idle_mask' to prevent stack overflow. Fixes: 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") Signed-off-by: Cheng Jian Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Srikar Dronamraju Reviewed-by: Vincent Guittot Reviewed-by: Valentin Schneider Link: https://lkml.kernel.org/r/20191213024530.28052-1-cj.chengjian@huawei.com --- kernel/sched/fair.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 846f50b..280d54c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5828,6 +5828,7 @@ static inline int select_idle_smt(struct task_struct *p, int target) */ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) { + struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); struct sched_domain *this_sd; u64 avg_cost, avg_idle; u64 time, cost; @@ -5859,11 +5860,11 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t time = cpu_clock(this); - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { + cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); + + for_each_cpu_wrap(cpu, cpus, target) { if (!--nr) return si_cpu; - if (!cpumask_test_cpu(cpu, p->cpus_ptr)) - continue; if (available_idle_cpu(cpu)) break; if (si_cpu == -1 && sched_idle_cpu(cpu))