From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S933283Ab3AIVjj (ORCPT <rfc822;w@1wt.eu>);
	Wed, 9 Jan 2013 16:39:39 -0500
Received: from mail-da0-f41.google.com ([209.85.210.41]:54480 "EHLO
	mail-da0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S933209Ab3AIVji (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 9 Jan 2013 16:39:38 -0500
Date: Wed, 9 Jan 2013 13:36:04 -0800
From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Glauber Costa <glommer@parallels.com>
Cc: Tejun Heo <tj@kernel.org>, David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@kernel.org>, Mel Gorman <mgorman@suse.de>,
        Michal Hocko <mhocko@suse.cz>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Thelen <gthelen@google.com>,
        Leonid Moiseichuk <leonid.moiseichuk@nokia.com>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        Minchan Kim <minchan@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        John Stultz <john.stultz@linaro.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org,
        patches@linaro.org, kernel-team@android.com
Subject: Re: [PATCH 1/2] Add mempressure cgroup
Message-ID: <20130109213604.GA9475@lizard.fhda.edu>
References: <20130104082751.GA22227@lizard.gateway.2wire.net>
 <1357288152-23625-1-git-send-email-anton.vorontsov@linaro.org>
 <20130109203731.GA20454@htj.dyndns.org>
 <50EDDF1E.6010705@parallels.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <50EDDF1E.6010705@parallels.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Jan 10, 2013 at 01:20:30AM +0400, Glauber Costa wrote:
[...]
> Given the above, I believe that ideally we should use this pressure
> mechanism in memcg replacing the current memcg notification mechanism.

Just a quick wonder: why would we need to place it into memcg, when we
don't need any of the memcg stuff for it? I see no benefits, not
design-wise, not implementation-wise or anything-wise. :)

We can use mempressure w/o memcg, and even then it can (or should :) be
useful (for cpuset, for example).

> More or less like timer expiration happens: you could still write
> numbers for compatibility, but those numbers would be internally mapped
> into the levels Anton is proposing, that makes *way* more sense.
> 
> If that is not possible, they should coexist as "notification" and a
> "pressure" mechanism inside memcg.
> 
> The main argument against it centered around cpusets also being able to
> participate in the play. I haven't yet understood how would it take
> place. In particular, I saw no mention to cpusets in the patches.

I didn't test it, but as I see it, once a process in a specific cpuset,
the task can only use a specific allowed zones for reclaim/alloc, i.e.
various checks like this in vmscan:

         if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
                     continue;

So, vmscan simply won't call vmpressure() if the zone is not allowed (so
we won't account that pressure, from that zone).

Thanks,
Anton