linux-kernel - Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or mapped vma clearing

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Message-Id: <1248726609.1374.425.camel@calx>
Date:	Mon, 27 Jul 2009 15:30:09 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	"Moussa A. Ba" <moussa.a.ba@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	akpm@...ux-foundation.org, adobriyan@...il.com, mel@....ul.ie,
	yinghan@...gle.com, npiggin@...e.de, jaredeh@...il.com
Subject: Re: [PATCH 1/1] pagemap clear_refs: modify to specify anon or
 mapped vma clearing

On Mon, 2009-07-27 at 13:19 -0700, Moussa A. Ba wrote:
> This patch makes the clear_refs proc interface a bit more versatile.
> It adds support  for clearing anonymous pages, file mapped pages or both.
> 
> The clear_refs entry is used to reset the Referenced bits on virtual and
> physical pages associated with a process.
> echo 1 > /proc/PID/clear_refs clears all pages associated with the process
> echo 2 > /proc/PID/clear_refs clears anonymous pages only
> echo 3 > /proc/PID/clear_refs clears file mapped pages only
> Any other value written to the proc entry will clear all pages.
> 
> Selective clearing the pages has a measurable impact on performance as it
> limits the number of page walks.  We have been using this interface and  this
> adds flexibility to the user user space application implementing the reference
> clearing.

Looks ok to me.

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

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


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