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=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 F1FA2C433DB for ; Fri, 22 Jan 2021 08:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9A1D23381 for ; Fri, 22 Jan 2021 08:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727015AbhAVIMS (ORCPT ); Fri, 22 Jan 2021 03:12:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21486 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726904AbhAVIKY (ORCPT ); Fri, 22 Jan 2021 03:10:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611302937; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1r1C6b8Yt+X+h4kUeUrmzS4UC5HaV/EkqiwbM/xr4OU=; b=NtZzJ9KD84xarm0pWCQ7v+CDNl8scVldVnC6hqfVri6m7kjg9ers2NmH73VEcloGMgTtaG 38+Sbl3OspUwbuvZ8YMN9VDQ5t/5Ntrx0Nfmmk0VSRiJP5CbnS/fsZos5E+vNyY5d28puM BdEcwoymDiZaSZaAG5a4MHB2hKLHnhQ= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-325-AsMHF58ZMU2gMq7wpl5nCA-1; Fri, 22 Jan 2021 03:08:55 -0500 X-MC-Unique: AsMHF58ZMU2gMq7wpl5nCA-1 Received: by mail-ed1-f70.google.com with SMTP id g6so2544494edw.13 for ; Fri, 22 Jan 2021 00:08:55 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=1r1C6b8Yt+X+h4kUeUrmzS4UC5HaV/EkqiwbM/xr4OU=; b=FvnNb18UnekeGv6rGNejkKKKSNwZqZLGDvsZ0sd7IS7ENIOKxHo5FTvU2RvbPgH5Ue V1FUgqYHkOtqTG91H/gIZYgWtWyFxR04Bp353/kPNNg1mcDYPcgIvWlpC8dtP13rwATH hGW7+bajffiBsDKYem0iB+8IYCHGj5yXgbDxnfRHC7lzCDLRG+OQZr30qmrhjk3PdOGL 06wPFm9+AbvXEi3OM+uUmKO0Q1T9M5aQSJSYwwQaiSPPAeD6U6RWDjpuTF7QEU++XR78 H47Ox3HycHSq1Q/w6XQINAe2U7YVbnUp1afg1g6LO8tDdUrcQmcK3PQ353/yHw4AEz5c zZrA== X-Gm-Message-State: AOAM531RQeNEcGlQISFwMehz9N5H1G4cXUqDmf4Z/xbSiXvevBWtVUU0 36C5nXzS0DUdMEyPqEwkuh7Vxj99UUScsGycVHHOlCbr+Uh4ymm4T3wnUutBSh7MdGjnEiM4vJs yR2SE73Y1T1SKAtXoSYe4eiZl X-Received: by 2002:a05:6402:490:: with SMTP id k16mr2229223edv.71.1611302934541; Fri, 22 Jan 2021 00:08:54 -0800 (PST) X-Google-Smtp-Source: ABdhPJy4iPl8/f+eb+Pr1AYLOy/jbyis1Gtj5kxSaoayd7OeDLN/a+loD+oNA0ELuCO2YPT68pB8SQ== X-Received: by 2002:a05:6402:490:: with SMTP id k16mr2229200edv.71.1611302934288; Fri, 22 Jan 2021 00:08:54 -0800 (PST) Received: from localhost.localdomain ([151.29.110.43]) by smtp.gmail.com with ESMTPSA id x17sm4706846edq.77.2021.01.22.00.08.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Jan 2021 00:08:53 -0800 (PST) Date: Fri, 22 Jan 2021 09:08:51 +0100 From: Juri Lelli To: Daniel Bristot de Oliveira Cc: linux-kernel@vger.kernel.org, Marco Perronet , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Li Zefan , Tejun Heo , Johannes Weiner , Valentin Schneider , cgroups@vger.kernel.org Subject: Re: [PATCH 3/6] sched/deadline: Allow DL tasks on empty (cgroup v2) cpusets Message-ID: <20210122080851.GK10569@localhost.localdomain> References: <8380113688bd64a6deb3241ff6a0fff62b157f47.1610463999.git.bristot@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8380113688bd64a6deb3241ff6a0fff62b157f47.1610463999.git.bristot@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 12/01/21 16:53, Daniel Bristot de Oliveira wrote: > cgroups v2 allows the cpuset controller to be enabled/disabled on > demand. On Fedora 32, cpuset is disabled by default. To enable it, > a user needs to: > > # cd /sys/fs/cgroup/ > # echo +cpuset > cgroup.subtree_control > > Existing cgroups will expose the cpuset interface (e.g., cpuset.cpus > file). By default, cpuset.cpus has no CPU assigned, which means that > existing tasks will move to a cpuset without cpus. This is kind of confusing, though. Isn't it? > Initially, I thought about returning an error and blocking the > operation. However, that is indeed not needed. The cpuset without > CPUs assigned will be a non-root cpuset, hence its cpu mask will > be the same as the root one. So, the bandwidth was already accounted, > and the task can proceed. > > Signed-off-by: Daniel Bristot de Oliveira > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Juri Lelli > Cc: Vincent Guittot > Cc: Dietmar Eggemann > Cc: Steven Rostedt > Cc: Ben Segall > Cc: Mel Gorman > Cc: Daniel Bristot de Oliveira > Cc: Li Zefan > Cc: Tejun Heo > Cc: Johannes Weiner > Cc: Valentin Schneider > Cc: linux-kernel@vger.kernel.org > Cc: cgroups@vger.kernel.org > --- > kernel/sched/deadline.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 943aa32cc1bc..788a391657a5 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -2871,6 +2871,13 @@ int dl_task_can_attach(struct task_struct *p, > bool overflow; > int ret; > > + /* > + * The cpuset has no cpus assigned, so the thread will not > + * change its affinity. Is this always the case also in the presence of deeper hierarchies? Thanks, Juri