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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 9D8D6C4743E for ; Tue, 8 Jun 2021 18:35:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D0D261441 for ; Tue, 8 Jun 2021 18:35:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234876AbhFHShh (ORCPT ); Tue, 8 Jun 2021 14:37:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:57560 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234858AbhFHSf1 (ORCPT ); Tue, 8 Jun 2021 14:35:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6CD3A613F9; Tue, 8 Jun 2021 18:32:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623177139; bh=shz5xA4uenEmO6NUnq5K3dZdPpj+Lg6KmyzudpB8yJQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=orHyf/g370ppLl4oP0LHq/IHZw6Z4EGGjiXOIgawjtPLWl23OxYRs+0QDl8DztRA9 Nsi9MO16qeF3oFdUDCQ91Ju16x8DciuwOpgf6jLhjGCoq9Pfwh4578kF3zcAjAh+a3 1hFEeOqQTC4hXnNZ3ICQ7tvKktlXrjA0dvB/AQlk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Cheng Jian , "Peter Zijlstra (Intel)" , Srikar Dronamraju , Vincent Guittot , Valentin Schneider , Yang Wei Subject: [PATCH 4.14 46/47] sched/fair: Optimize select_idle_cpu Date: Tue, 8 Jun 2021 20:27:29 +0200 Message-Id: <20210608175932.005035051@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210608175930.477274100@linuxfoundation.org> References: <20210608175930.477274100@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Cheng Jian commit 60588bfa223ff675b95f866249f90616613fbe31 upstream. 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 Signed-off-by: Yang Wei Tested-by: Yang Wei Signed-off-by: Greg Kroah-Hartman --- kernel/sched/fair.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5779,6 +5779,7 @@ static inline int select_idle_smt(struct */ 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; @@ -5809,11 +5810,11 @@ static int select_idle_cpu(struct task_s time = local_clock(); - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { + cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); + + for_each_cpu_wrap(cpu, cpus, target) { if (!--nr) return -1; - if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) - continue; if (idle_cpu(cpu)) break; }