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

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Message-ID: <4A03164D.90203@redhat.com>
Date:	Thu, 07 May 2009 13:11:41 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Peter Zijlstra <peterz@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"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

Christoph Lameter wrote:

> We need some way to control this. If there would be a way to simply switch
> off eviction of exec pages (via /proc/sys/vm/never_reclaim_exec_pages or
> so) I'd use it.

Nobody (except you) is proposing that we completely disable
the eviction of executable pages.  I believe that your idea
could easily lead to a denial of service attack, with a user
creating a very large executable file and mmaping it.

Giving executable pages some priority over other file cache
pages is nowhere near as dangerous wrt. unexpected side effects
and should work just as well.
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