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Date: Fri, 15 Mar 2002 21:57:06 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: mingo@elte.hu
To: Joe Korty <joe.korty@ccur.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        Linus Torvalds <torvalds@transmeta.com>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] 2.4.18 scheduler bugs
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On Fri, 15 Mar 2002, Joe Korty wrote:

> > > [...] But on the Athlon the IPI isnt going down a little side channel
> > > between cpus.
> > 
> > but even in the Athlon case an IPI is still an IRQ entry, which will add
> > at least 200 cycles or more to the idle wakeup latency.
> 
> It is an idle cpu that is spending those 200 cycles.

wrong. When it's woken up it's *not* an idle CPU anymore, and it's the
freshly woken up task that is going to execute 200 cycles later...

	Ingo

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