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

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Message-ID: <4A04580B.5050501@redhat.com>
Date:	Fri, 08 May 2009 12:04:27 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Elladan <elladan@...imo.com>
CC:	Christoph Lameter <cl@...ux.com>,
	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>,
	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

Elladan wrote:

>> 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.
> 
> I don't think this sort of DOS is relevant for a single user or trusted user
> system.  

Which not all systems are, meaning that the mechanism
Christoph proposes can never be enabled by default and
would have to be tweaked by the user.

I prefer code that should work just as well 99% of the
time, but can be enabled by default for everybody.
That way people automatically get the benefit.

-- 
All rights reversed.
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