linux-kernel - Re: [PATCH] mm: swap prefetch improvements

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Message-ID: <20070521160029.GA28715@elte.hu>
Date:	Mon, 21 May 2007 18:00:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Con Kolivas <kernel@...ivas.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Ray Lee <ray-lk@...rabbit.org>, ck list <ck@....kolivas.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: swap prefetch improvements


* Con Kolivas <kernel@...ivas.org> wrote:

> > A suggestion for improvement: right now swap-prefetch does a small 
> > bit of swapin every 5 seconds and stays idle inbetween. Could this 
> > perhaps be made more agressive (optionally perhaps), if the system 
> > is not swapping otherwise? If block-IO level instrumentation is 
> > needed to determine idleness of block IO then that is justified too 
> > i think.
> 
> Hmm.. The timer waits 5 seconds before trying to prefetch, but then 
> only stops if it detects any activity elsewhere. It doesn't actually 
> try to go idle in between but it doesn't take much activity to put it 
> back to sleep, hence detecting yet another "not quite idle" period and 
> then it goes to sleep again. I guess the sleep interval can actually 
> be changed as another tunable from 5 seconds to whatever the user 
> wanted.

there was nothing else running on the system - so i suspect the swapin 
activity flagged 'itself' as some 'other' activity and stopped? The 
swapins happened in 4 bursts, separated by 5 seconds total idleness.

	Ingo
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