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[209.132.180.67]) by mx.google.com with ESMTP id x126si4660566oix.53.2019.12.13.01.49.02; Fri, 13 Dec 2019 01:49:13 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726595AbfLMJrY (ORCPT + 99 others); Fri, 13 Dec 2019 04:47:24 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:7684 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725793AbfLMJrX (ORCPT ); Fri, 13 Dec 2019 04:47:23 -0500 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id D5F2D2A762260A0E853F; Fri, 13 Dec 2019 17:47:20 +0800 (CST) Received: from [127.0.0.1] (10.133.217.236) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.439.0; Fri, 13 Dec 2019 17:47:11 +0800 Subject: Re: [PATCH] sched/fair: Optimize select_idle_cpu To: Valentin Schneider , Peter Zijlstra CC: , , , , , , , , References: <20191212144102.181510-1-cj.chengjian@huawei.com> <20191212152406.GB2827@hirez.programming.kicks-ass.net> <2498b792-8549-5ffd-0d85-179740e356a0@arm.com> From: "chengjian (D)" Message-ID: Date: Fri, 13 Dec 2019 17:47:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <2498b792-8549-5ffd-0d85-179740e356a0@arm.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.133.217.236] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/12/12 23:44, Valentin Schneider wrote: > On 12/12/2019 15:24, Peter Zijlstra wrote: >> On Thu, Dec 12, 2019 at 10:41:02PM +0800, Cheng Jian wrote: >> >>> Fixes: 1ad3aaf3fcd2 ("sched/core: Implement new approach to scale select_idle_cpu()") >> The 'funny' thing is that select_idle_core() actually does the right >> thing. >> >> Copying that should work: >> >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 08a233e97a01..416d574dcebf 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -5828,6 +5837,7 @@ 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 +5869,11 @@ 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)) >> > That looks sane enough. I'd only argue the changelog should directly point > out that the issue is we consume some CPUs out of 'nr' that are not allowed > for the task and thus waste our attempts. > > . Hi,Valentin Yeah,Yours are more clear. Thank you so much. -- Cheng Jian