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SubjectRe: Using O(1) scheduler with 600 processes.
On Thu, 2003-01-23 at 20:05, mgross wrote:
> You should definitely give it a try.
> However; boosts in Oracle throughput by going to the O(1) scheduler may end
> up being dependent on your I/O setup.
> I was helping out with a TPCC benchmark effort last fall for Itanium Oracle
> through put on Red Hat AS. For the longest time the guys with the big iron
> hardware would not move to the newer kernels with the O(1) scheduler. They
> had a silly rule of only accepting changes that improved TPCC throughput.
> (oh, this work was on 4-way Itanium 2's with 32Gig of ram, and a large number
> of clarion fiber channel disk array towers)

We've got LSI, so it's very similar.

> Anyway, for the longest time the old 2.4.18 kernel with the 4/10/04 ia-64
> patch was 10% better than the a kernel with O(1) scheduler. I never quite
> figured out what the problem was. I think the difference was in the way
> Oracle likes to be on a Round Robbin scheduler, and the O(1) scheduler tended
> to get unlucky more often than the old scheduler, for those drive arrays.
> However; when we updated the clarion towers to have more drives and to 18K
> RPM drives from the 15K drives, all of a sudden the O(1) scheduler beat the
> the old scheduler.

Well, if I could get a clean patch against 2.4.20, or possibly some help
fixing the one I do have, thanks to Ingo, then we'd have a straight
O(1) sched for 2.4.20. I tried merging the patch that Ingo gave me, and
everything seems OK, but I don't have any menu selection for O(1) stuff
in the kernel config.(0 and 100 priority bits)

So I can't tell if it's enabled.

> Your milage will vary.
> Give it a try.
> --mgross

I agree. In the interest of time, I may have to forego O(1), but maybe
I'll get lucky. :) *hint*hint* :)


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