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=-8.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 34366C48BDF for ; Thu, 24 Jun 2021 10:29:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17171613E3 for ; Thu, 24 Jun 2021 10:29:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232124AbhFXKcR (ORCPT ); Thu, 24 Jun 2021 06:32:17 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:33011 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231964AbhFXKcP (ORCPT ); Thu, 24 Jun 2021 06:32:15 -0400 Received: from mail-pj1-f70.google.com ([209.85.216.70]) by youngberry.canonical.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1lwMcO-0006y4-4V for linux-kernel@vger.kernel.org; Thu, 24 Jun 2021 10:29:56 +0000 Received: by mail-pj1-f70.google.com with SMTP id g19-20020a17090adb13b029016f4a877b4fso5669757pjv.8 for ; Thu, 24 Jun 2021 03:29:56 -0700 (PDT) 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=Fp8p7HZuUA7dLzTxrkrRGItFpn1kDPBrup/d3fPNHEw=; b=mC34K0ooQZVh1yJSr6g0kkZp+ESGDVm5wWkkAFOv30XFltR/OMNS2MJu2aENS4sTKD OOmx4R98rQvLnE3ahAc6xcWwRAUd7Yf6dsUUsJFImW5vW5Ozsb9BcBhtGP7vHfYqjHp2 oD/mIYM4xijWk9ftyw8HJZt64r3KFzEKD+d+lVv9NZq5O6GFfogPWS8hMNWEWvtwmxj4 w5Ls0I1Gbq93yEcHkxEbEyMIwir+rJ7sZrN07RWLSSB5fXlSpLiJOilB+3k5JZ/oc9ID 8pnbiA7Blok+xtdPdotY1J0fA9E/rXoPbeSd8e7+7gQGj1JR2e9kEI74gWLolz7L/NCt 3j1Q== X-Gm-Message-State: AOAM532ws+i1/lYaoJTWSw6eHUJrclYroeHuOAr71+rB19DDR1TQZwLX OgnTw3R8NudE1VYcJ98Avi8VXDCf3XyVuHMaEb+lJ4ufLkaD4A5XRuxXsRbs2G7lVAbOlKOeKdN pFv7SRXNf0wDRon2uj+Y5JtF61G4ulA43RWc6WGGCWn8hjVhbXNRzMKAT X-Received: by 2002:a65:6659:: with SMTP id z25mr4096762pgv.291.1624530583634; Thu, 24 Jun 2021 03:29:43 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyh/cf8E3LbmxFWhYziPJsbPcYAWsD13MA8K3m3YL5HGEeA5Swn7XRMlE4u/QR2fNpWrqPm8L1B4ZB3DSp0psU= X-Received: by 2002:a65:6659:: with SMTP id z25mr4096713pgv.291.1624530583241; Thu, 24 Jun 2021 03:29:43 -0700 (PDT) MIME-Version: 1.0 References: <17fc60a3-cc50-7cff-eb46-904c2f0c416e@canonical.com> <20201118235015.GB6015@geo.homenetwork> <20201119003319.GA6805@geo.homenetwork> <7c9462c9-8908-8592-0727-9117d4173724@canonical.com> In-Reply-To: From: Po-Hsu Lin Date: Thu, 24 Jun 2021 18:29:29 +0800 Message-ID: Subject: Re: [PATCH v3] sched/fair: fix unthrottle_cfs_rq for leaf_cfs_rq list To: Vincent Guittot Cc: "Guilherme G. Piccoli" , Tao Zhou , "gregkh@linuxfoundation.org" , Sasha Levin , SeongJae Park , Ben Segall , Dietmar Eggemann , Juri Lelli , Tao Zhou , Mel Gorman , Ingo Molnar , Tao Zhou , Phil Auld , Peter Zijlstra , Pavan Kondeti , Steven Rostedt , Jay Vosburgh , Gavin Guo , halves@canonical.com, nivedita.singhvi@canonical.com, linux-kernel , "# v4 . 16+" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Vincent, sorry to resurrect this thread again, I was trying to backport this patch and corresponding fixes to our Ubuntu 4.15 kernel [1] to fix an issue report by LTP cfs_bandwidth01 test[2], my colleague Guilherme told me there once a discussion about backporting this on this thread. You mentioned here this should not be backported to earlier stable kernel, I am curious if there is any specific reason of it? Too risky maybe? Thanks! PHLin [1] https://lists.ubuntu.com/archives/kernel-team/2021-June/121571.html [2] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/sched/cfs-scheduler/cfs_bandwidth01.c On Thu, Nov 19, 2020 at 9:25 PM Vincent Guittot wrote: > > On Thu, 19 Nov 2020 at 12:36, Guilherme G. Piccoli > wrote: > > > > > > > > On 19/11/2020 05:36, Vincent Guittot wrote: > > > On Thu, 19 Nov 2020 at 01:36, Tao Zhou wrote: > > >> > > >> On Thu, Nov 19, 2020 at 07:50:15AM +0800, Tao Zhou wrote: > > >>> On Wed, Nov 18, 2020 at 07:56:38PM -0300, Guilherme G. Piccoli wrote: > > >>>> Hi Vincent (and all CCed), I'm sorry to ping about such "old" patch, but > > >>>> we experienced a similar condition to what this patch addresses; it's an > > >>>> older kernel (4.15.x) but when suggesting the users to move to an > > >>>> updated 5.4.x kernel, we noticed that this patch is not there, although > > >>>> similar ones are (like [0] and [1]). > > >>>> > > >>>> So, I'd like to ask if there's any particular reason to not backport > > >>>> this fix to stable kernels, specially the longterm 5.4. The main reason > > >>>> behind the question is that the code is very complex for non-experienced > > >>>> scheduler developers, and I'm afraid in suggesting such backport to 5.4 > > >>>> and introduce complex-to-debug issues. > > >>>> > > >>>> Let me know your thoughts Vincent (and all CCed), thanks in advance. > > >>>> Cheers, > > >>>> > > >>>> > > >>>> Guilherme > > >>>> > > >>>> > > >>>> P.S. For those that deleted this thread from the email client, here's a > > >>>> link: > > >>>> https://lore.kernel.org/lkml/20200513135528.4742-1-vincent.guittot@linaro.org/ > > >>>> > > >>>> > > >>>> [0] > > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fe61468b2cb > > >>>> > > >>>> [1] > > >>>> https://lore.kernel.org/lkml/20200506141821.GA9773@lorien.usersys.redhat.com/ > > >>>> <- great thread BTW! > > >>> > > >>> 'sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list" failed to apply to > > >>> 5.4-stable tree' > > >>> > > >>> You could check above. But I do not have the link about this. Can't search it > > >>> on LKML web: https://lore.kernel.org/lkml/ > > >>> > > >>> BTW: 'ouwen210@hotmail.com' and 'zohooouoto@zoho.com.cn' all is myself. > > >>> > > >>> Sorry for the confusing.. > > >>> > > >>> Thanks. > > >> > > >> Sorry again. I forget something. It is in the stable. > > >> > > >> Here it is: > > >> > > >> https://lore.kernel.org/stable/159041776924279@kroah.com/ > > > > > > I think it has never been applied to stable. > > > As you mentioned, the backport has been sent : > > > https://lore.kernel.org/stable/20200525172709.GB7427@vingu-book/ > > > > > > I received another emailed in September and pointed out to the > > > backport : https://www.spinics.net/lists/stable/msg410445.html > > > > > > > > >> > > > > Thanks a lot Tao and Vincent! Nice to know that you already worked the > > backport, gives much more confidence when the author does that heheh > > > > So, this should go to stable 5.4.y, but not 4.19.y IIUC? > > Yeah. they should be backported up to v5.1 but not earlier > > Regards, > Vincent > > > Cheers, > > > > > > Guilherme