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Date: Sun, 6 Jan 2002 05:01:12 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: <mingo@elte.hu>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Linus Torvalds <torvalds@transmeta.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [announce] [patch] ultra-scalable O(1) SMP and UP scheduler
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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.

	Ingo

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