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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2ADFC43334 for ; Thu, 14 Jul 2022 06:19:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234557AbiGNGTv (ORCPT ); Thu, 14 Jul 2022 02:19:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231418AbiGNGTq (ORCPT ); Thu, 14 Jul 2022 02:19:46 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A12B1EECB for ; Wed, 13 Jul 2022 23:19:43 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4Lk47R6CwjzFq0y; Thu, 14 Jul 2022 14:18:43 +0800 (CST) Received: from [10.67.102.169] (10.67.102.169) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 14 Jul 2022 14:19:40 +0800 CC: , Josh Don , Chen Yu , Subject: Re: [PATCH 1/5] sched/fair: ignore SIS_UTIL when has idle core To: Abel Wu , Peter Zijlstra , Mel Gorman , Vincent Guittot References: <20220712082036.5130-1-wuyun.abel@bytedance.com> <20220712082036.5130-2-wuyun.abel@bytedance.com> From: Yicong Yang Message-ID: <8e7d75d4-613e-f35e-e932-323789666fb1@huawei.com> Date: Thu, 14 Jul 2022 14:19:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: <20220712082036.5130-2-wuyun.abel@bytedance.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.169] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500009.china.huawei.com (7.192.105.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/12 16:20, Abel Wu wrote: > When SIS_UTIL is enabled, SIS domain scan will be skipped if > the LLC is overloaded. Since the overloaded status is checked > in the load balancing at LLC level, the interval is llc_size > miliseconds. The duration might be long enough to affect the > overall system throughput if idle cores are out of reach in > SIS domain scan. > > Signed-off-by: Abel Wu > --- > kernel/sched/fair.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index a78d2e3b9d49..cd758b3616bd 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6392,16 +6392,19 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > struct sched_domain *this_sd; > u64 time = 0; > > - this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > - if (!this_sd) > - return -1; > - > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > > - if (sched_feat(SIS_PROP) && !has_idle_core) { > + if (has_idle_core) > + goto scan; > + > + if (sched_feat(SIS_PROP)) { > u64 avg_cost, avg_idle, span_avg; > unsigned long now = jiffies; > > + this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > + if (!this_sd) > + return -1; > + I don't follow the change here. True that this_sd is used only in SIS_PROP, but it seems irrelevant with your commit. Does the position of this make any performance difference? Thanks. > /* > * If we're busy, the assumption that the last idle period > * predicts the future is flawed; age away the remaining > @@ -6436,7 +6439,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > return -1; > } > } > - > +scan: > for_each_cpu_wrap(cpu, cpus, target + 1) { > if (has_idle_core) { > i = select_idle_core(p, cpu, cpus, &idle_cpu); >