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Message-ID: <44225AB4.4080503@yahoo.com.au>
Date: Thu, 23 Mar 2006 19:22:12 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: jos poortvliet <jos@mijnkamer.nl>
CC: ck@vds.kolivas.org, Con Kolivas <kernel@kolivas.org>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [ck] swap prefetching merge plans
References: <20060322205305.0604f49b.akpm@osdl.org> <200603231804.36334.kernel@kolivas.org> <200603230901.57052.jos@mijnkamer.nl>
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jos poortvliet wrote:
> Op donderdag 23 maart 2006 08:04, schreef Con Kolivas:
> 
>>On Thu, 23 Mar 2006 03:53 pm, Andrew Morton wrote:
>>
>>>A look at the -mm lineup for 2.6.17:
>>>
>>>mm-implement-swap-prefetching.patch
>>>mm-implement-swap-prefetching-fix.patch
>>>mm-implement-swap-prefetching-tweaks.patch
>>>
>>>  Still don't have a compelling argument for this, IMO.
> 
> 
> well, the reason i use it is my computer is much more reactive in the morning. 
> linux uses to get very slow after a night of not-doing-much except some 
> 'sleep 5h && blabla' and cron stuff. in the morning it takes a few HOURS to 
> get up and running smoothly. with swap prefetch, it actually feels faster 
> compared to a fresh boot. now you can force swap prefetch to start working, i 
> use it now and then after some heavy taskts which pulled everything to swap.
> 

I have two issues with this argument (not that I'm trying to say it
couldn't make a difference in your case).

Firstly, swap prefetch actually doesn't handle the midnight updatedb pageout
problem nicely. It doesn't do any prefetching when the pagecache/vfs cache
fills memory (which is what would have to happen for updatedb to push stuff
into swap).

Secondly, with or without swap prefetch, I think we can do a better job of
handling these use-once patterns to begin with.

-- 
SUSE Labs, Novell Inc.
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