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Date: Thu, 7 May 2009 10:18:47 -0400 (EDT)
From: Christoph Lameter <cl@linux.com>
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To: Peter Zijlstra <peterz@infradead.org>
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       Andrew Morton <akpm@linux-foundation.org>,
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       Nick Piggin <npiggin@suse.de>, Johannes Weiner <hannes@cmpxchg.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first class
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On Thu, 7 May 2009, Peter Zijlstra wrote:

> It re-instates the young bit for PROT_EXEC pages, so that they will only
> be paged when they are really cold, or there is severe pressure.

But they are rescanned until then. Really cold means what exactly? I do a
back up of a few hundred gigabytes and do not use firefox while the backup
is ongoing. Will the firefox pages still be in memory or not?

> This simply gives them an edge over regular data. I don't think the
> extra scanning is a problem, since you rarely have huge amounts of
> executable pages around.
>
> mlock()'ing all code just doesn't sound like a good alternative.

Another possibility may be to put the exec pages on the mlock list
and scan the list if under extreme duress?