linux-kernel - Re: [patch -mm] i386: use pte_update_defer in ptep_test_and_clear

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Message-ID: <Pine.LNX.4.64.0704161956510.13584@blonde.wat.veritas.com>
Date:	Mon, 16 Apr 2007 20:04:29 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	Zachary Amsden <zach@...are.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch -mm] i386: use pte_update_defer in ptep_test_and_clear_{dirty,young}

On Mon, 16 Apr 2007, David Rientjes wrote:
> 
> > Compromise patch below: would that be satisfactory to you, David?
> 
> I really like the patch, but for perhaps a slightly different reason: 
> we're only flushing ranges that have been shown to need it.  We aren't 
> completely flushing the entire mm which is likely to be excessive in 
> situations where we're actually using /proc/pid/clear_refs in combination 
> with /proc/pid/smaps for memory footprint approximation (i.e. it's on a 
> fine granularity).

It would be more of a reason to like the patch, if more architectures
actually implemented flush_tlb_range as anything different from
flush_tlb_mm ;)  Sadly, few can do better than flush_tlb_mm: ia64
is the exception I remember, and maybe a couple of others.  I put
flush_tlb_range there merely because it seems more appropriate,
but it's rather deceptive.

Hugh
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