linux-kernel - Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen

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Message-ID: <alpine.DEB.1.10.0905071016410.24528@qirst.com>
Date:	Thu, 7 May 2009 10:18:47 -0400 (EDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tytso@....edu" <tytso@....edu>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Elladan <elladan@...imo.com>, Nick Piggin <npiggin@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first class
 citizen

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?

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