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=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 863C6C4743E for ; Tue, 8 Jun 2021 18:40:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6FFF261483 for ; Tue, 8 Jun 2021 18:40:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235073AbhFHSmO (ORCPT ); Tue, 8 Jun 2021 14:42:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:36258 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234674AbhFHSkQ (ORCPT ); Tue, 8 Jun 2021 14:40:16 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D526261351; Tue, 8 Jun 2021 18:34:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623177287; bh=pIIGlN9EPcfE33lJxRnT5yrbrIVU1+ivFW8PN9HZ+A8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uCEfNaNte5AIT705vNBNyw/KDQyyawQhJL7fUyVgo6qaiJDgOC7DOiAbr/AMCOf0x rPFwrw8Y068FaBnd2m158hslSHamz33Oyeq3VGoiUvAXcKqu7Y5MDYt7SJjBKgkUb9 ZD2CaqIqKoCpQVuLqxKSIpj+QNolj6kLsTlEPXBg= 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 4.19 57/58] sched/fair: Optimize select_idle_cpu Date: Tue, 8 Jun 2021 20:27:38 +0200 Message-Id: <20210608175934.158307657@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210608175932.263480586@linuxfoundation.org> References: <20210608175932.263480586@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: stable@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 @@ -6154,6 +6154,7 @@ 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; @@ -6184,11 +6185,11 @@ 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 (available_idle_cpu(cpu)) break; }