Re: 2.4.19-rc1 + O(1) scheduler

From: Robert Love (
Date: Thu Jun 27 2002 - 15:39:02 EST

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Date: 27 Jun 2002 16:35:46 -0400
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On Thu, 2002-06-27 at 16:23, Alexandre P. Nunes wrote:

> It seems that the version of O(1) scheduler on 2.4.19-pre10-ac2 is not
> perfect (see below), but I asked because it gave me overall performance
> gains, specially in multithreading programs (and now I'm going to try
> with ngpt 2.00). At least that is the first impression, I'm trying it
> for a few days.

Alan has some patches queued and I will continue to send him updates as
we get them into 2.5 and they prove stable.

I also will update my 2.4 O(1) scheduler patches when I return from
OLS. This would allow a 2.4-ac vs 2.4-O(1) test.

> I said "not perfect" because a rather non-important benchmarking called
> quake 3 seens a lot worse in pre10-ac2 with preemptive patches when
> compared against -pre10 with preemptive patches: sound and screen popped
> sometimes, like if there was a background task borrowing some cpu, which
> was not the case, I mean, no other background tasks compared with
> testing against -pre10. That was the only exception to the above
> paragraph that I can remember of.

There is some "rudeness" in the current O(1) scheduler code in 2.4-ac
that could result in poor latency under certain workloads.

The patch should be in a near future 2.4-ac although I will need to
update the preempt-kernel patch to take advantage of it.

        Robert Love

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