linux-kernel - Re: [PATCH v2 1/2] memcg: break out event counters from other stats

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Message-Id: <20110217144116.58d71a7d.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 17 Feb 2011 14:41:16 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Greg Thelen <gthelen@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] memcg: break out event counters from other stats

On Thu, 17 Feb 2011 14:33:15 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Wed, 16 Feb 2011 21:34:01 -0800
> Greg Thelen <gthelen@...gle.com> wrote:
> 
> > From: Johannes Weiner <hannes@...xchg.org>
> > 
> > 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@...xchg.org>
> > Signed-off-by: Greg Thelen <gthelen@...gle.com>
> 
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 

Hmm..but not mentioning the change "s64 -> unsigned long(may 32bit)" clearly
isn't good behavior. 

Could you clarify both of changes in patch description as
==
This patch
  - devides counters to signed and unsigned ones(increase only).
  - makes unsigned one to be 'unsigned long' rather than 'u64'
and
  - then next patch will make 'signed' part to be 'long'
==
for changelog ?

Thanks,
-Kame


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