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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>,
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Date: Tue, 14 Mar 2006 08:06:19 +0100
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On Tue, 2006-03-14 at 01:50 -0500, Lee Revell wrote:
> On Tue, 2006-03-14 at 07:40 +0100, Mike Galbraith wrote:
> >> > 
> > > 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.
> 
> It's only a big problem if LBA48 is in use which allows 32MB of IO to be
> in flight at once, this depends on the size of the drive.

This is a 120G drive.

> 
> What does that value default to?

512.

> >   I _can_ generate mp3 player audio dropout though,
> > despite mp3 files living on a separate drive/controller.
> > 
> 
> Does this go away if you run the mp3 player at nice -20?

Nope.

	-Mike