Re: [announce] [patch] ultra-scalable O(1) SMP and UP scheduler

From: Ingo Molnar (
Date: Sat Jan 05 2002 - 23:01:12 EST

On Sat, 5 Jan 2002, Davide Libenzi wrote:

> Ingo, you don't need that many queues, 32 are more than sufficent. If
> you look at the distribution you'll see that it matters ( for
> interactive feel ) only the very first ( top ) queues, while lower
> ones can very easily tollerate a FIFO pickup w/out bad feelings.

I have no problem with using 32 queues as long as we keep the code
flexible enough to increase the queue length if needed. I think we should
make it flexible and not restrict ourselves to something like word size.
(with this i'm not suggesting that you meant this, i'm just trying to make
sure.) I saw really good (behavioral, latency, not performance) effects of
the longer queue under high load, but this must be weighed against the
cache footprint of the queues.


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