From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932832Ab0EMUMt (ORCPT ); Thu, 13 May 2010 16:12:49 -0400 Received: from smtp-out.google.com ([74.125.121.35]:10928 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932503Ab0EMUMq (ORCPT ); Thu, 13 May 2010 16:12:46 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:x-system-of-record; b=e5Q12pwdiRUfm5wEytVL3z3G3TjON05QQRtNTLFm5UiAJq9fbS/zo4nVs8CiOMyUN Pd61mTcYyW8ACKzGqXDKw== MIME-Version: 1.0 In-Reply-To: References: <1273669541.3086.24.camel@localhost> Date: Thu, 13 May 2010 13:12:42 -0700 Message-ID: Subject: Re: [PATCH/RFC] Have sane default values for cpusets From: Paul Menage To: Dhaval Giani Cc: balbir@linux.vnet.ibm.com, peterz@infradead.org, lennart@poettering.net, jsafrane@redhat.com, tglx@linutronix.de, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 12, 2010 at 12:59 PM, Dhaval Giani wrote: > On Wed, May 12, 2010 at 9:36 PM, Paul Menage wrote: >> On Wed, May 12, 2010 at 12:29 PM, Dhaval Giani wrote: >>>> I think the idea is reasonable - the only way that I could see it >>>> breaking someone would be code that currently does something like: >>>> >>>> mkdir A >>>> mkdir B >>>> echo 1 > A/mem_exclusive >>>> echo 1 > B/mem_exclusive >>>> echo $mems_for_a > A/mems >>>> echo $mems_for_b > B/mems >>>> >>>> The attempts to set the mem_exclusive flags would fail, since A and B >>>> would both have all of the parent's mems. >>>> >>> >>> But would this not fail otherwise? >>> >> >> Assuming that mems_for_a and mems_for_b were disjoint, it would be >> fine currently. >> > > Ah my bad. I misread mems_for_a as taking the value from the parent. > You are right, that was a case I missed. > > Hmm, so how do we fix this? Any solutions? Not fixing the kernel > pushes the problem to the userspace, making it hard for tons of more > applications to use cgroups without jumping through a lot of hoops. > Well, it's not clear to me whether the case I outlined is actually one that would bite people - it's likely a rare case. Balbir's point that some apps might get upset by finding non-empty mems/cpus in a newly-created cgroup is more reasonable. How about a per-cgroup cpuset.inherit_defaults file that defaults to false and is inherited from the parent. If the parent's file is set to true, then the mems/cpus are also inherited? Then the sysadmin who's giving out user-controllable cpuset-based cgroups can just set it to true and the users don't need to worry about setting up the defaults. Paul