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Date: Thu, 6 Mar 2003 23:00:24 -0800
From: Andrew Morton <akpm@digeo.com>
To: Aaron Lehmann <aaronl@vitelus.com>
Cc: torvalds@transmeta.com, mingo@elte.hu, rml@tech9.net,
       linux-kernel@vger.kernel.org
Subject: Re: [patch] "HT scheduler", sched-2.5.63-B3
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Aaron Lehmann <aaronl@vitelus.com> wrote:
>
> On Thu, Mar 06, 2003 at 09:42:03AM -0800, Linus Torvalds wrote:
> > But it was definitely there. 3-5 second _pauses_. Not slowdowns.
> 
> I can second this. Using Linux 2.5.5x, untarring a file while
> compiling could cause X to freeze for several seconds at a time.

This may be a VM/block/IO scheduler thing.  If the X server is trying to page
some text in and the disk is busy writing some stuff out then yes, the X
server can freeze for some time.

Of course, a ton of work has gone into this problem, and more work continues
to be done.

If your machine has a small amount of memory, or is heavily overcommitted
then it is more likely to happen.

Using the CFQ or AS IO schedulers will help a bit.  And decreasing
/proc/sys/vm/swappiness may help too.

I'd be interested in feedback on the latter.  The default policy of 60% seems
to be about right for the 128M to 256M desktops, but I am running 85% on
larger memory machines so that a bit more stuff gets paged out.


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