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Subject: Re: [PATCH] mm: Implement swap prefetching tweaks
From: Mike Galbraith <efault@gmx.de>
To: Lee Revell <rlrevell@joe-job.com>
Cc: Con Kolivas <kernel@kolivas.org>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org, ck@vds.kolivas.org
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Date: Tue, 14 Mar 2006 07:40:03 +0100
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On Sat, 2006-03-11 at 23:54 -0500, Lee Revell wrote:
> On Sat, 2006-03-11 at 08:51 +0100, Mike Galbraith wrote:
> > There used to be a pages in flight 'restrictor plate' in there that
> > would have probably helped this situation at least a little.  But in
> > any case, it sounds like you'll have to find a way to submit the IO in
> > itty bitty synchronous pieces. 
> 
> echo 64 > /sys/block/hd*/queue/max_sectors_kb
> 
> There is basically a straight linear relation between whatever you set
> this to and the maximum scheduling latency you see.  It was developed to
> solve the exact problem you are describing.

<head-scratching>

Is it possible that you mean pci latency?  I'm unable to measure any
scheduling latency > 5ms while pushing IO for all my little Barracuda
disk is worth.  I _can_ generate mp3 player audio dropout though,
despite mp3 files living on a separate drive/controller.

	-Mike

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