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

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Date:	Tue, 22 May 2007 20:37:54 +1000
From:	Con Kolivas <kernel@...ivas.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Antonino Ingargiola <tritemio@...il.com>,
	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

On Tuesday 22 May 2007 20:25, Ingo Molnar wrote:
> * Con Kolivas <kernel@...ivas.org> wrote:
> > > > 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.
> > >
> > > I've noted burst swapins separated by some seconds of pause in my
> > > desktop system too (with sp_tester and an idle gnome).
> >
> > That really is expected, as just about anything, including journal
> > writeout, would be enough to put it back to sleep for 5 more seconds.
>
> note that nothing like that happened on my system - in the
> swap-prefetch-off case there was _zero_ IO activity during the sleep
> period.

Ok, granted it's _very_ conservative. I really don't want to risk its presence 
being a burden on anything, and the iowait it induces probably makes it turn 
itself off for another PREFETCH_DELAY (5s). I really don't want to cross the 
line to where it is detrimental in any way. Not dropping out on a 
cond_resched and perhaps making the delay tunable should be enough to make it 
a little less "sleepy".

-- 
-ck
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