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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 889A5C2D0ED for ; Fri, 27 Mar 2020 01:30:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5FBD620787 for ; Fri, 27 Mar 2020 01:30:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="G5dS7ASB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727809AbgC0B1C (ORCPT ); Thu, 26 Mar 2020 21:27:02 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:27858 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727122AbgC0B1B (ORCPT ); Thu, 26 Mar 2020 21:27:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585272420; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MUJ4EFBey4RnBsubrV8OieVsspJ5+/9YngaSQHIcXsM=; b=G5dS7ASBmByiPynkdns0cjjiamIfAXgpytnr0VBKI7LgddUM6hQBfc+/Cyp9TuZ/jLFzSV pbI9f4aCAy+1qqB2XLiUjENxmbIkKb5NE1F0oUtqlUhQBrrn3e1zIzsxu7GUyQ+KCOjHqW 4SolYuBAT6FJzOr/A40sQgpPcSKi1wA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-305-4cO3SvUDMUK6LNiuW7ZcNA-1; Thu, 26 Mar 2020 21:26:58 -0400 X-MC-Unique: 4cO3SvUDMUK6LNiuW7ZcNA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A6AA6800D6C; Fri, 27 Mar 2020 01:26:55 +0000 (UTC) Received: from llong.remote.csb (ovpn-117-112.rdu2.redhat.com [10.10.117.112]) by smtp.corp.redhat.com (Postfix) with ESMTP id 73F9C60BF3; Fri, 27 Mar 2020 01:26:52 +0000 (UTC) Subject: Re: [PATCH RFC] cpuset: Make cpusets get restored on hotplug To: Joel Fernandes , Tejun Heo Cc: Sonny Rao , linux-kernel@vger.kernel.org, Dmitry Shmidt , Amit Pundir , kernel-team@android.com, Jesse Barnes , vpillai@digitalocean.com, Peter Zijlstra , Guenter Roeck , Greg Kerr , cgroups@vger.kernel.org, Johannes Weiner , Li Zefan References: <20200326191623.129285-1-joel@joelfernandes.org> <20200326192035.GO162390@mtj.duckdns.org> <20200326194448.GA133524@google.com> <972a5c1b-6721-ac20-cec5-617af67e617d@redhat.com> <20200326201649.GQ162390@mtj.duckdns.org> <20200326202340.GA146657@google.com> From: Waiman Long Organization: Red Hat Message-ID: <592d4120-0b42-4607-5efd-fb2d4d29f0cc@redhat.com> Date: Thu, 26 Mar 2020 21:26:51 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200326202340.GA146657@google.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/26/20 4:23 PM, Joel Fernandes wrote: > On Thu, Mar 26, 2020 at 04:18:59PM -0400, Tejun Heo wrote: >> On Thu, Mar 26, 2020 at 01:05:04PM -0700, Sonny Rao wrote: >>> I am surprised if anyone actually wants this behavior, we (Chrome >>> OS) >> >> The behavior is silly but consistent in that it doesn't allow empty >> active cpusets and it has been like that for many many years now. >> >>> found out about it accidentally, and then found that Android had >>> been carrying a patch to fix it. And if it were a desirable >>> behavior then why isn't it an option in v2? >> >> Nobody is saying it's a good behavior (hence the change in cgroup2) >> and there are situations where changing things like this is >> justifiable, but, here: >> >> * The proposed change makes the interface inconsistent and does so >> unconditionally on what is now a mostly legacy interface. >> >> * There already is a newer version of the interface which includes >> the desired behavior. >> >> * I forgot but as Waiman pointed out, you can even opt-in to the >> new behavior, which is more comprehensive without the >> inconsitencies, while staying on cgroup1. > > Thank you Tejun, Waiman and Sonny. I confirmed the cgroup_v2_mode > option fixes cgroup v1's broken behavior. > > We will use this mount option on our systems to fix it. I am glad that it works for you. I think the problem is that the v2_mode mount option is not that well documented. Maybe I should send a patch to add some some description about it in cgroup-v2.rst or cgroup-v1/cpusets.rst. Cheers, Longman