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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 D575AC3F2D1 for ; Tue, 3 Mar 2020 17:50:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0B7720CC7 for ; Tue, 3 Mar 2020 17:50:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583257827; bh=mUqj1wUk/cnaZs6KUcmNgyIVNiPw2nm7mH9rZ9Vfw/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yhjl9c8bUQmb1f2FhS04sf9uGUl50LGU6jL+cwBMY6npYbFde65xJDkI1ODk58Xk9 3atxb/2vy+Z6HH43mOLETOcTDAsSMazU4IDJuFId4aIOye8H5FFNG/kiTlwh88B7VZ T/Z7OkWMrnZus8U651BVMukLKysYwst59dFHZTjI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731906AbgCCRu0 (ORCPT ); Tue, 3 Mar 2020 12:50:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:58020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731893AbgCCRuX (ORCPT ); Tue, 3 Mar 2020 12:50:23 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 BE641208C3; Tue, 3 Mar 2020 17:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583257823; bh=mUqj1wUk/cnaZs6KUcmNgyIVNiPw2nm7mH9rZ9Vfw/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FlxDtlVFjVZ/4bzJUVOzeqs+2W1UVhocl32KPCSWDLIlTHnfiA2s7cGniby0SgYXc p7hJDi9DQRcDDGYVNqcBovWDgKnPAgbyEYP/Zvz0M/8Ses6bfTFA4ppQL8/sC5r5JO jIj7yeJ6FKlx8i59EjwTrwe02Ci4urtGePiRpIu4= 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 Subject: [PATCH 5.5 143/176] sched/fair: Optimize select_idle_cpu Date: Tue, 3 Mar 2020 18:43:27 +0100 Message-Id: <20200303174321.300181988@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200303174304.593872177@linuxfoundation.org> References: <20200303174304.593872177@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org 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: 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 @@ -5828,6 +5828,7 @@ 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; @@ -5859,11 +5860,11 @@ static int select_idle_cpu(struct task_s 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))