linux-kernel - Re: [PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file

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Message-ID: <28c262361001031649w60a59151m8e210304217d4e35@mail.gmail.com>
Date:	Mon, 4 Jan 2010 09:49:46 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Hugh Dickins <hugh.dickins@...cali.co.uk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file_rss

On Thu, Dec 31, 2009 at 5:43 PM, Hugh Dickins
<hugh.dickins@...cali.co.uk> wrote:
> On Thu, 31 Dec 2009, Minchan Kim wrote:
>> On Thu, Dec 31, 2009 at 1:49 AM, Hugh Dickins
>> <hugh.dickins@...cali.co.uk> wrote:
>> >
>> > You are right that I completely overlooked the issue of whether to
>> > include the ZERO_PAGE in rss counts (now being a !vm_normal_page,
>> > it was just natural to leave it out); and I overlooked the fact that
>> > it used to be counted into file_rss in the old days (being !PageAnon).
>> >
>> > So I'm certainly at fault for that, and thank you for bringing the
>> > issue to attention; but once considered, I can't actually see a good
>> > reason why we should add code to count ZERO_PAGEs into file_rss now.
>> > And if this patch falls, then 1/3 and 3/3 would fall also.
>> >
>> > And the patch below would be incomplete anyway, wouldn't it?
>> > There would need to be a matching change to zap_pte_range(),
>> > but I don't see that.
>>
>> Thanks.
>> If we think this patch is need, I will repost path with fix it.
>>
>> What do you think?
>
> If someone comes up with a convincing case in which their system
> is behaving significantly worse because the zero page is not being
> counted in rss now, then we shall probably want your patch.
> But I still don't yet see a reason to add code just to keep the
> anon_rss+file_rss number looking the same as it was before, in this
> exceptional case where there's a significant number of zero pages.

Okay. I understand your point.
I will repost this patch when we need this. :)
Thanks for careful review, Hugh.

>
> Hugh
>



-- 
Kind regards,
Minchan Kim
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