Subject: Re: UVM/other problems for desktop users in current?
To: None <>
From: Wolfgang Rupprecht <>
List: current-users
Date: 12/17/2002 21:31:34 (Greg A. Woods) writes:
> Sure you can get away with running Xserver and one big application at a
> time like Mozilla or what have you on a workstation, but that's because
> you're essentially doing primarily GUI stuff.  However once you start
> compiling and running I/O intensive stuff like CVS then you're doing
> more what's done on a multi-user general-purpose server.  Those two
> kinds of application just do not mix well on a single CPU system -- you
> can't expect to get good compiler throughput and at the same time have
> sub-second GUI response, especially when you context switch through a
> half dozen big GUI applications all at once too!

Perhaps one has to break the loads down into at least two major
categories.  1) CPU saturating loads 2) disk-arm saturating loads.
I've seen no problem with running cpu-intensive tasks such as "nice
-20" userland builds while XFree86 was running.  On the other hand,
things do get slow when someone is saturating the disk arm.  

I've always had a sneaking suspicion that the disk arm could use a
better scheduler.  I bet it would make things feel quite a bit
snappier if all the interactive tasks got first dibs on the disk arm
and the non-interactive things (like 'cvs update') got last dibs.
Some niceness-like value that trickled down into the disk buffers
could allow the sweep algorithm to favor buffers that came from
interactive tasks.

Wolfgang Rupprecht

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