From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.9 required=5.0 tests=DKIM_SIGNED, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 5FAD97D043 for ; Thu, 31 May 2018 16:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932714AbeEaQTq (ORCPT ); Thu, 31 May 2018 12:19:46 -0400 Received: from mail-yw0-f195.google.com ([209.85.161.195]:33808 "EHLO mail-yw0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932710AbeEaQTp (ORCPT ); Thu, 31 May 2018 12:19:45 -0400 Received: by mail-yw0-f195.google.com with SMTP id b125-v6so4390667ywe.1; Thu, 31 May 2018 09:19:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=iXsud8AO/VqPMP/AUI6IhoSYiSKrR2rIe4R3EMYxks8=; b=I1wD6JR/fg78umobxEsQSa/wh4sKp9DwYzSCEkFiLV7TUTM0UhIn0CsfOcXpPXyryj ITajAI2mLRooBLku3CeTLiw0hpuDwmgs+pjbWU8CyS7JsVAT2po2UNVLD0n+OIgdn59J nYma4et5+pklxkZzMS9paLVAoU6NkHp+F5owp1nEruNJdfDxhIv0ToDYzpPjI807v6Qw IVQT4D9KxLWXrPA8EF/cI73kQODdarKAQwf2UFB4oRV46+TMc0bCs87iIjfZSu8Ipd9r BKo98jyPQlkVuhBBghHuqTvhxa48Ncl1EBrwutTj9v6JxEC7MiJ6ejrhzlVJMk6Uk7nK q4Zw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=iXsud8AO/VqPMP/AUI6IhoSYiSKrR2rIe4R3EMYxks8=; b=iHMYrbcyDIdt768BHH+1N2SaR6aGAGmTiUK/vWnG7eqlYg6rw6BqF4XnDHvvN+Djr2 JHZ+2ZRBdPnj+xNh5V/23U53au56an7gBpo78zhjyI5yjEz1NmrMJqD3cvEs17X8GMZN 2Rm1OZFX6j5ldPPxD5671UnrmS6zmuFn7QkteMPA3XcQHMeZHAYXx85QNKvkpTBu7uGH UCCM0nlZdNZTJp9AqZfWFyvUruLsuUNtF6zwp1o8zlRybrVeS9uxPiKRAx5LmAref/ct acmhTLuaWz88R7LsWVcv6dbVC/WS/6Y+lDH1ng7nTdWZoVsqBol2tOjvXvaYmo3hNLJR NVgw== X-Gm-Message-State: ALKqPwfOOw0jwRjdwdsRW5pVwCnPdL1lroaaY15UWgEiX6JwaicOHzd/ vOtFDl6FlxcLnPtzz+Ze60Y= X-Google-Smtp-Source: ADUXVKJTMohDSqvMI8SwfRnPqYYitonBefnZ7ZlvIFfMsh/H4l15uZ2/1Okdui90kEykr/FN8mtomQ== X-Received: by 2002:a81:7b0a:: with SMTP id w10-v6mr4057231ywc.70.1527783584749; Thu, 31 May 2018 09:19:44 -0700 (PDT) Received: from localhost ([2620:10d:c091:200::3:bd3d]) by smtp.gmail.com with ESMTPSA id v141-v6sm7527435ywc.65.2018.05.31.09.19.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 May 2018 09:19:43 -0700 (PDT) Date: Thu, 31 May 2018 09:19:42 -0700 From: Tejun Heo To: Peter Zijlstra Cc: Waiman Long , Zefan Li , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli , Patrick Bellasi Subject: Re: [PATCH] cpuset: Enforce that a child's cpus must be a subset of the parent Message-ID: <20180531161942.GW1351649@devbig577.frc2.facebook.com> References: <1527687991-1431-1-git-send-email-longman@redhat.com> <5B0F4F09.9050100@huawei.com> <5B0FAE72.1090204@huawei.com> <20180531082613.GF12180@hirez.programming.kicks-ass.net> <5B0FB58C.9030705@huawei.com> <4dc718bc-4bd5-4998-853b-9c6ba67b89a0@redhat.com> <20180531155807.GU1351649@devbig577.frc2.facebook.com> <20180531161645.GN12180@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180531161645.GN12180@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hello, On Thu, May 31, 2018 at 06:16:45PM +0200, Peter Zijlstra wrote: > > So, let's please stay away from it even if that means a bit of > > overhead in terms of interface. > > Urgh, that again :/ Yeah, well, it's pretty important. > I'm still not convinced by your arguments though. The root container can > access all the sub-groups anyway and can grub around in them to take > away resources if it really wants to. That's really messy and if you delegated away a subtree, you can't walk the subtree in a race free way, not easily anyway. > For cpuset in particular randomly restricting on the ancestor level can > create an unrecoverable trainwreck inside a container. Affinities are > not recoverable. Once a runnable task ends up with an empty set, its > affinities are reset and the smaller (empty) set is lost. Yeah, for cpuset, it's messier, but it isn't different from hotunplug scenario, right? I think the best we can do there is putting ancestor operation on an equal footing as hotplug ops. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html