linux-kernel - Re: [PATCH -mmotm-2009-12-10-17-19] Fix wrong rss count of smaps

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Message-ID: <1262142686.3000.2140.camel@calx>
Date:	Tue, 29 Dec 2009 21:11:26 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Minchan Kim <minchan.kim@...il.com>
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>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: Re: [PATCH -mmotm-2009-12-10-17-19] Fix wrong rss count of smaps

On Wed, 2009-12-30 at 10:33 +0900, Minchan Kim wrote:
> Hi, Matt. 
> 
> On Tue, 29 Dec 2009 14:08:59 -0600
> Matt Mackall <mpm@...enic.com> wrote:
> 
> > On Mon, 2009-12-28 at 13:46 +0900, Minchan Kim wrote:
> > > I am not sure we have to account zero page with file_rss. 
> > > Hugh and Kame's new zero page doesn't do it. 
> > > As side effect of this, we can prevent innocent process which have a lot
> > > of zero page when OOM happens. 
> > > (But I am not sure there is a process like this :)
> > > So I think not file_rss counting is not bad. 
> > > 
> > > RSS counting zero page with file_rss helps any program using smaps?
> > > If we have to keep the old behavior, I have to remake this patch. 
> > > 
> > > == CUT_HERE ==
> > > 
> > > Long time ago, We regards zero page as file_rss and
> > > vm_normal_page doesn't return NULL.
> > > 
> > > But now, we reinstated ZERO_PAGE and vm_normal_page's implementation
> > > can return NULL in case of zero page. Also we don't count it with
> > > file_rss any more.
> > > 
> > > Then, RSS and PSS can't be matched.
> > > For consistency, Let's ignore zero page in smaps_pte_range.
> > > 
> > 
> > Not counting the zero page in RSS is fine with me. But will this patch
> > make the total from smaps agree with get_mm_rss()?
> 
> Yes. Anon page fault handler also don't count zero page any more, now. 
> Nonetheless, smaps counts it with resident. 

Ok, great.

Acked-by: Matt Mackall <mpm@...enic.com>

-- 
http://selenic.com : development and support for Mercurial and Linux


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