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 S1751027AbdLSReA (ORCPT <rfc822;w@1wt.eu>);
        Tue, 19 Dec 2017 12:34:00 -0500
Received: from mail-qk0-f170.google.com ([209.85.220.170]:33686 "EHLO
        mail-qk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750733AbdLSRd5 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 19 Dec 2017 12:33:57 -0500
X-Google-Smtp-Source: ACJfBov9D6TRuujiWZM+zcd2U68tvyVou+5ck+Qd9Gfek16ne2hzV/7riwjXm0DWJ2Iiu2odQbrqTg==
Date: Tue, 19 Dec 2017 09:33:54 -0800
From: Tejun Heo <tj@kernel.org>
To: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Roman Gushchin <guro@fb.com>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Greg Thelen <gthelen@google.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        Cgroups <cgroups@vger.kernel.org>, linux-doc@vger.kernel.org
Subject: Re: [RFC PATCH] mm: memcontrol: memory+swap accounting for cgroup-v2
Message-ID: <20171219173354.GQ3919388@devbig577.frc2.facebook.com>
References: <20171219000131.149170-1-shakeelb@google.com>
 <20171219124908.GS2787@dhcp22.suse.cz>
 <CALvZod5jU9vPoJaf44TVT0_HQpEESiELJU5MD_DDRbcOkPNQbg@mail.gmail.com>
 <20171219152444.GP3919388@devbig577.frc2.facebook.com>
 <CALvZod5sWWBX69QovOeLBSx9vij7=5cmoSocdTUvh2Uq8=noyQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALvZod5sWWBX69QovOeLBSx9vij7=5cmoSocdTUvh2Uq8=noyQ@mail.gmail.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

Hello,

On Tue, Dec 19, 2017 at 09:23:29AM -0800, Shakeel Butt wrote:
> To provide consistent memory usage history using the current
> cgroup-v2's 'swap' interface, an additional metric expressing the
> intersection of memory and swap has to be exposed. Basically memsw is
> the union of memory and swap. So, if that additional metric can be

Exposing anonymous pages with swap backing sounds pretty trivial.

> used to find the union. However for consistent memory limit
> enforcement, I don't think there is an easy way to use current 'swap'
> interface.

Can you please go into details on why this is important?  I get that
you can't do it as easily w/o memsw but I don't understand why this is
a critical feature.  Why is that?

Thanks.

-- 
tejun