Date: Mon, 03 Jul 2000 10:55:45 -0400 From: "Jeroen C. van Gelderen" <jeroen@vangelderen.org> To: Greg Lehey <grog@lemis.com> Cc: Daniel Eischen <eischen@vigrid.com>, Jason Evans <jasone@canonware.com>, Luoqi Chen <luoqi@watermarkgroup.com>, smp@FreeBSD.ORG Subject: Re: SMP meeting summary Message-ID: <3960A971.982DDF07@vangelderen.org> References: <20000703114535.T39024@wantadilla.lemis.com> <Pine.SUN.3.91.1000703060948.5216A-100000@pcnet1.pcnet.com> <20000703200039.H62680@wantadilla.lemis.com>
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Greg Lehey wrote:
[...]
> That's an assumption. So far we have *never* had a thundering herd,
> because the code don't work yet.
Your position is an assumption too. The difference is that
one usually doesn't optimize until one has profiling
information available. Am I correct in assuming that you
haven't done any profiling yet? Am I correct in assuming
that wake_one is an optimization?
> > then waking everyone is an optimization since you only have to take
> > the scheduling lock once.
>
> No. If I understand things correctly, each process would need to get
> the schedlock, and only one process can get the mutex. Why wake the
> rest? What do you want them to do?
If -on average- there is only one process waiting you don't
want to go trough the trouble of implementing a more complex
wake_one. It would only complicate the code with negligible
gain.
That's my reading of Sun's claims in Solaris and given that
they have a little more experience with this kind of thing
I'm inclined to believe them until I see facts stating the
contrary.
Cheers,
Jeroen
--
Jeroen C. van Gelderen o _ _ _
jeroen@vangelderen.org _o /\_ _ \\o (_)\__/o (_)
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