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Date: Mon, 8 Nov 2010 08:52:41 +0900
Message-ID: <AANLkTikhX+2E5o=vqc6Yb6GGPJJT2FwuzKMiC31GdY0s@mail.gmail.com>
Subject: Re: [patch 3/4] memcg: break out event counters from other stats
From: Minchan Kim <minchan.kim@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dave Young <hidave.darkstar@gmail.com>,
        Andrea Righi <arighi@develer.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Wu Fengguang <fengguang.wu@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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On Mon, Nov 8, 2010 at 7:14 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> For increasing and decreasing per-cpu cgroup usage counters it makes
> sense to use signed types, as single per-cpu values might go negative
> during updates.  But this is not the case for only-ever-increasing
> event counters.
>
> All the counters have been signed 64-bit so far, which was enough to
> count events even with the sign bit wasted.
>
> The next patch narrows the usage counters type (on 32-bit CPUs, that
> is), though, so break out the event counters and make them unsigned
> words as they should have been from the start.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

Fair enough.
We already have used unsigned long in vmstat.

-- 
Kind regards,
Minchan Kim