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Date: Tue, 9 Mar 2004 11:41:12 -0500 (EST)
From: Robert Watson <rwatson@freebsd.org>
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To: Bin Ren <br260@cam.ac.uk>
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Subject: Re: a serious error in sched_ule.c?
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On 9 Mar 2004, Bin Ren wrote:

> Hi, all:
> 
> I've been reading sched_ule.c and seem to find a serious error:
> 
> in 'sched_slice()':
> 
>          * Rationale:
>          * KSEs in interactive ksegs get the minimum slice so that we
>          * quickly notice if it abuses its advantage.
> 
> Then, there is:
> 
>         if (!SCHED_INTERACTIVE(kg)) {
>                 .....
>                 .....
>         } else
>                 ke->ke_slice = SCHED_SLICE_INTERACTIVE;
> 
> Then, at the beginning of the file, there is:
> 
> #define SCHED_SLICE_INTERACTIVE         (slice_max)
> 
> 
> (slice_max) for interactive KSEs???? Either this is a serious mistake or 
> I'm seriously missing sth here.

I believe this is a synchronization error in the comment and the code. 
The code was changed to provide a maximum slice to interactive
applications because non-CPU intensive X11 applications will be marked as
interactive, but redraws get interrupted in a short slice.  When the
change went in to increase the time slice I saw an observable improvement
in the redraws of X11 apps under load.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Senior Research Scientist, McAfee Research