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From: James A Sutherland <jas88@cam.ac.uk>
To: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: Swap
Date: Tue, 20 Nov 2001 09:16:04 +0000
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Cc: Erik Gustavsson <cyrano@algonet.se>, linux-kernel@vger.kernel.org
In-Reply-To: <3BF82443.5D3E2E11@starband.net> <E165tpy-0002Dm-00@mauve.csi.cam.ac.uk> <m1ofly6tvb.fsf@frodo.biederman.org>
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On Tuesday 20 November 2001 2:47 am, Eric W. Biederman wrote:
> James A Sutherland <jas88@cam.ac.uk> writes:
> > On Monday 19 November 2001 6:12 pm, Eric W. Biederman wrote:
> > > Erik Gustavsson <cyrano@algonet.se> writes:
> > > > I agree...   After a while it always seems that 80% or more of my RAM
> > > > is used for cache and buffers while my open, but not currently used
> > > > apps get pushed onto disk. Then when I decide to switch to that
> > > > mozilla window of emacs session I have to wait for it to be loaded
> > > > from disk again. Also considering the kind of disk activity this box
> > > > has, the data in the cache is mostly the last few hour's MP3's, in
> > > > other words utterly useless as that data will not be used again. I'd
> > > > rather my apps stayed in RAM...
> > > >
> > > >
> > > > Is there a way to limit the size of the cache?
> > >
> > > Reasonable.  It looks like the use once heuristics are failing for your
> > > mp3 files.   Find out why that is happening and they should push the
> > > rest of your system into swap.
> >
> > Getting clobbered by the mp3 player accessing the ID3 tag? That way, at
> > least part of the file is used twice, so use-ONCE won't matter...
>
> For that page perhaps.  But that is only 4K.  That doesn't explain the rest
> of it.  use-once is per page.

True - the ID3 can be in several different places, so that could account for 
a couple of pages, but mp3 players certainly DON'T read the whole file in 
before playing...

Does the mp3 player in question try to pre-read the pages using one 
process/thread, before the actual player thread reaches them? How far apart 
would two accesses need to be to disable read-once?


James.
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