linux-kernel - Re: [patch 1/3 take2] smaps: extract pte walker from smaps code

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Message-ID: <Pine.LNX.4.64.0702070124210.22710@chino.kir.corp.google.com>
Date:	Wed, 7 Feb 2007 01:35:31 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <clameter@....com>
cc:	Andrew Morton <akpm@...l.org>, Hugh Dickins <hugh@...itas.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Paul Davies <pauld@....unsw.edu.au>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/3 take2] smaps: extract pte walker from smaps code

On Wed, 7 Feb 2007, Christoph Lameter wrote:

> Clearing reference bits? Ummm... That is a pretty inaccurate measure since 
> reclaim can remove pages and revert the reference bits. It can never work 
> reliably.
> 

It's not intended to work precisely, it's intended to give a good estimate 
of task memory footprint.  There are several different scenarios that can 
interfere with getting a precise measurement via this method; then again 
/proc/pid/smaps is so expensive already because of the iteration through 
VMA's that it's not something you'd do regularly.

Any other suggestions on how to obtain this data is certainly welcome.

> Would it be possible to sync up with the people doing the page table 
> interface?
> 

(+pauld)

Is there an update on Paul Davies' implementation that would allow us to 
iterate through a set of pte's in a vm_area_struct range?

> Could we somehow consolidate smaps and numa_maps?
> 

Sure, but that's beyond the scope of this patchset.  My intention in 
extracting away a new pte_walker was to prevent having two identical 
implementations and it could easily be extracted even further to lib for 
the ioremap case that Paul mentioned.

		David
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