From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 27 Jul 2007 20:16:32 +0200
From: Rene Herman <rene.herman@gmail.com>
MIME-Version: 1.0
Subject: Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans
 for 2.6.23]
References: <9a8748490707231608h453eefffx68b9c391897aba70@mail.gmail.com> <20070727030040.0ea97ff7.akpm@linux-foundation.org> <1185531918.8799.17.camel@Homer.simpson.net> <200707271345.55187.dhazelton@enter.net>
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To: Daniel Hazelton <dhazelton@enter.net>
Cc: Mike Galbraith <efault@gmx.de>, Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>, Frank Kingswood <frank@kingswood-consulting.co.uk>, Andi Kleen <andi@firstfloor.org>, Nick Piggin <nickpiggin@yahoo.com.au>, Ray Lee <ray-lk@madrabbit.org>, Jesper Juhl <jesper.juhl@gmail.com>, ck list <ck@vds.kolivas.org>, Paul Jackson <pj@sgi.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On 07/27/2007 07:45 PM, Daniel Hazelton wrote:

> Updatedb or another process that uses the FS heavily runs on a users
> 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
> pressure that causes other applications to be swapped to disk. In the
> morning the user has to wait for the system to swap those applications
> back in.
> 
> Questions about it:
> Q) Does swap-prefetch help with this? 
> A) [From all reports I've seen (*)] Yes, it does. 

No it does not. If updatedb filled memory to the point of causing swapping 
(which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch 
hasn't any memory to prefetch into -- updatedb itself doesn't use any 
significant memory.

Here's swap-prefetch's author saying the same:

http://lkml.org/lkml/2007/2/9/112

| It can't help the updatedb scenario. Updatedb leaves the ram full and
| swap prefetch wants to cost as little as possible so it will never
| move anything out of ram in preference for the pages it wants to swap
| back in.

Now please finally either understand this, or tell us how we're wrong.

Rene.

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