From: "John Yau" <jyau_kernel_dev@hotmail.com>
To: "'Robert Love'" <rml@tech9.net>
Cc: <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] Minor scheduler fix to get rid of skipping in xmms
Date: Sat, 6 Sep 2003 18:41:52 -0400
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>The rationale behind Ingo's patch is to "break up" the timeslices to give
better scheduling latency to 
>multiple tasks at the same priority. 
>So it is not "unnecessary context switches," just "extra context switches."

Hmm...my reasoning is that those switches are unnecessary because the
interactivity bonus/penalty will take care of breaking the timeslices up in
case of a CPU hog, albeit not at precise 25 ms granularity.  Though having
regularity in scheduling is nice, I think Ingo's patch somewhat negates the
purpose of having heterogenous time slice lengths.  I suspect Ingo's
approach will thrash the caches quite a bit more than mine; we should
definitely test this a bit to find out for sure.  Any suggestions on how to
go about that?

If we're going to do a context switch every 25 ms no matter what, we might
as well just make the scheduler a true real time scheduler, dump having
different time slice lengths and interactivity recalculations, and go
completely round robin with strictly enforced priorities and a single class
of time slice somewhere 1 to 5 ms long.


John Yau
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