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=-4.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 A3262C433E0 for ; Fri, 24 Jul 2020 11:53:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7867D206E3 for ; Fri, 24 Jul 2020 11:53:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DVzMykgb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726768AbgGXLxd (ORCPT ); Fri, 24 Jul 2020 07:53:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726280AbgGXLxc (ORCPT ); Fri, 24 Jul 2020 07:53:32 -0400 Received: from mail-wm1-x344.google.com (mail-wm1-x344.google.com [IPv6:2a00:1450:4864:20::344]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB311C0619D3 for ; Fri, 24 Jul 2020 04:53:31 -0700 (PDT) Received: by mail-wm1-x344.google.com with SMTP id a6so8438515wmm.0 for ; Fri, 24 Jul 2020 04:53:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=9fkc7zQHbUKv6oJjCYqFeYv2U4+eCFKPgmt6sjvkA0s=; b=DVzMykgb/gQhd0NTWcO/irYJ0RTSihM6KanWZg+kdl5fqcHifyMc1zLr75yPskD6AJ w3qrbSY4CSOE7riMxfVvngn1gN2Gi5BdAcv6eKZh7CM8LfWKKjvf/OnGHl4o4mmiE7lM WZ8osSabsAlWVyOn35cEwktdnz/QM2wMURw3030CfoXq2qq8hmtmAebkKEitDXtall3M 71dE/3dBBZEPFf8cYkAU4OrTcXVbuHW0MT3ZFl/BbtzZ5iO1+DtqmgpjQC20PuNlBob+ 0R/26x3A0+1mgXLSq23uy5q7gmcjzkEnU9Mm7RU3mYJtpvk9YBVSEkfw/JFdRYAn9MCm Nt6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=9fkc7zQHbUKv6oJjCYqFeYv2U4+eCFKPgmt6sjvkA0s=; b=e1UhX/Phyhg/rHDZ8MmHNA7OIrxcox4X+LAEK1ZlIfcjD6olXmvFpwKtboT7YH5uDR VhV/BUY6CWgrVz2JevFL6tou58xp+vCxvBsRpcP+vQTGnwkNPwfgkBFLbsYzAnCvUK7m xzTb6lwrMhIAFl4sqUpw87PLo/GK73el8hP/zht5tcd6gLQGLEWrm1svYKVCIqkrgwy8 BrVGUAvIh/Yi8jsothLXeogDDuPfl+Kr+jmRtWvJtAT9m4AheJVaNCZlv+zEGvgEiPuk AZXsKAE5/VZC1GXfpSbsd0JFioO7JCqUP0Gr5u1mM5Z+I/I55XqVMXD31Gt9WDSiguHn TRNQ== X-Gm-Message-State: AOAM532JQrCWU97T1AnhUZ3gencOWdvaLtJSEIi5FCm4ffV3n+MlwkGi 7t2gS5/V8bEfbEuglPbfNC+N4GOEMHp0myYMX9A= X-Google-Smtp-Source: ABdhPJw/p5FV5jm6je4FzYrCOdZubGFdTWc/Z4paicIz9b3b1hQzYh1I4zb8wpZP216HoFQqtQdZ5vth1u9LRwSHSlU= X-Received: by 2002:a1c:28a:: with SMTP id 132mr8308761wmc.109.1595591610712; Fri, 24 Jul 2020 04:53:30 -0700 (PDT) MIME-Version: 1.0 References: <20200723233853.48815-1-humjb_1983@163.com> In-Reply-To: From: Jiang Biao Date: Fri, 24 Jul 2020 19:53:19 +0800 Message-ID: Subject: Re: [PATCH] sched/fair: consider sched-idle CPU when selecting idle core To: Vincent Guittot Cc: Jiang Biao , Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , linux-kernel , Jiang Biao Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 24 Jul 2020 at 18:34, Vincent Guittot wrote: > > On Fri, 24 Jul 2020 at 10:12, Jiang Biao wrote: > > > > On Fri, 24 Jul 2020 at 15:24, Vincent Guittot > > wrote: > > > > > > On Fri, 24 Jul 2020 at 01:39, Jiang Biao wrote: > > > > > > > > From: Jiang Biao > > > > > > > > Sched-idle CPU has been considered in select_idle_cpu and > > > > select_idle_smt, it also needs to be considered in select_idle_core to > > > > be consistent and keep the same *idle* policy. > > > > > > In the case of select_idle_core, we are looking for a core that is > > > fully idle but if one CPU of the core is running a sched_idle task, > > > the core will not be idle and we might end up having the wakeup task > > > on a CPU and a sched_idle task on another CPU of the core which is not > > > what we want > > Got it. sched_idle task may interfere its sibling, which brings me > > another question, > > If there's a core with smt1 running sched_idle task and smt2 idle, > > selecting smt1 > > rather than smt2 should be more helpful for wakee task, because wakee task > > could suppress the sched_idle task without neighbour interfering. > > But the sched_idle will then probably quickly move on the idle smt2 > > > And there seems to be no consideration about that currently. > > Is it worth improving that? > > This will complexify and extend the duration of the search loop and > as mentioned above, it will most probably be a nop at the end because > of sched_idle task moving on smt2 Indeed, the complexity is not worth. Thanks for the explanation. Regards, Jiang > > > > > Thanks a lot. > > > > Regards, > > Jiang