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=-13.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 17EC7C433E3 for ; Mon, 3 Aug 2020 12:34:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6A49204EC for ; Mon, 3 Aug 2020 12:34:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="GZA0wsa4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729534AbgHCMeS (ORCPT ); Mon, 3 Aug 2020 08:34:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729518AbgHCMeC (ORCPT ); Mon, 3 Aug 2020 08:34:02 -0400 Received: from mail-pf1-x444.google.com (mail-pf1-x444.google.com [IPv6:2607:f8b0:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE83BC06174A for ; Mon, 3 Aug 2020 05:34:02 -0700 (PDT) Received: by mail-pf1-x444.google.com with SMTP id y206so7739190pfb.10 for ; Mon, 03 Aug 2020 05:34:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=uM2vZnd6apiHVlprtfwpHKfrja9VsUva5BQDdDFeOqI=; b=GZA0wsa4JHDCBaPz1RKHDehOq/1VUdU66+kj/avxY9pSBZ6SwPyRxoTRf5xwNIZIap Ry3e6JKGWp9kAAQF5HcIef+9j0cmFJ06CDwK2r/m0IsFyh7f2ouyt+pN7gdh+y6SH0xo Ko0Vr7zZPTLwXo51JIYczfh6Oy22JldW2lce4JGo2BKa10FR6HcoQ8o/r/rFQ5MJI8qV NaK+vvZ2Dxdo+fEHfONbFc0jAppOuNd4/7toRnGO17uUxUEtvunzAM8N/NvGAZtfO13/ kY5EbJIF4hu0u2C9CDsgMd5p4ScqYIdwaplaRue3snb9wtpUtoUiBYljOtaPHQ2smzDQ WQaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=uM2vZnd6apiHVlprtfwpHKfrja9VsUva5BQDdDFeOqI=; b=YDc3eciZYB9voWg78JnSmM2l6aO5Ikxwe/w2NRvUjYNMxESJrA2Q6PFBRhEZO1j1Gl 8BsCjygkSF4Kc1VhbI1wINdvRCyyAo3JrcHRfK9Przw5ufZIBNgO1Agrx6pIkc/hTggu 60LkDrj6yVq9Akb+JlOoTjbERmHyq3rnVdm2KRTfTNjnNmHT8nYO2tRXAiUTZoiheea9 T1Eh7vVPQ/auc6UAQnZAaHr0Cp3YdNVnZIvzCjpHiiuBFV36brOZurMk3zi136Iyu1Hv hddSd9AYZOd1B5GbbL+89v6cxlPvsXTpY68r3fcaiqLwX6LeQfnpPpXiB42Lud2fm3Et 2mdQ== X-Gm-Message-State: AOAM530Uh/3YKDjxumDDS7oEMMOI6RwjEr1cJ3JdnoOgiKtto8egzN3D BbQ1qBW74h22CxemAJov+zbfBhyx X-Google-Smtp-Source: ABdhPJyaViM3LU7p5/mxDQhYnuEqgP2PPPQDiqH/iqONh4OFFNM4c3G1wP1TLHilRKlev3rO9g1xUQ== X-Received: by 2002:aa7:94b5:: with SMTP id a21mr15523274pfl.237.1596458042235; Mon, 03 Aug 2020 05:34:02 -0700 (PDT) Received: from [0.0.0.0] ([101.32.42.91]) by smtp.gmail.com with ESMTPSA id r202sm9649046pfc.127.2020.08.03.05.33.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Aug 2020 05:34:01 -0700 (PDT) Subject: Re: [PATCH] sched/fair: Fix the logic about active_balance in load_balance() To: Dietmar Eggemann , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de Cc: linux-kernel@vger.kernel.org References: <20200802045141.130533-1-arch0.zheng@gmail.com> From: Qi Zheng Message-ID: <9b584a64-b419-e7ea-249e-6fed9db804c0@gmail.com> Date: Mon, 3 Aug 2020 20:33:58 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dietmar, I understand, thank you for your review and very detailed explanation. Yours, Qi Zheng On 2020/8/3 下午3:36, Dietmar Eggemann wrote: > On 02/08/2020 06:51, Qi Zheng wrote: >> I think the unbalance scenario here should be that we need to >> do active balance but it is not actually done. So fix it. >> >> Signed-off-by: Qi Zheng >> --- >> kernel/sched/fair.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 2ba8f230feb9..6d8c53718b67 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -9710,7 +9710,7 @@ static int load_balance(int this_cpu, struct rq *this_rq, >> } else >> sd->nr_balance_failed = 0; >> >> - if (likely(!active_balance) || voluntary_active_balance(&env)) { >> + if (likely(!active_balance) && voluntary_active_balance(&env)) { >> /* We were unbalanced, so reset the balancing interval */ >> sd->balance_interval = sd->min_interval; >> } else { >> > > Active balance is potentially already been done when we reach this code. > > See 'if (need_active_balance(&env))' and 'if (!busiest->active_balance)' > further up. > > Here we only reset sd->balance_interval in case: > (A) the last load balance wasn't an active one > (B) the reason for the active load balance was: > (1) asym packing > (2) capacity of src_cpu is reduced compared to the one of dst_cpu > (3) misfit handling > > (B) is done to not unnecessarily increase of balance interval, see > commit 46a745d90585 ("sched/fair: Fix unnecessary increase of balance > interval"). >