Date: Wed, 20 Feb 2002 17:46:52 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Greg Lehey <grog@FreeBSD.ORG> Cc: Jake Burkholder <jake@locore.ca>, "David O'Brien" <obrien@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: Patch to improve mutex collision performance Message-ID: <200202210146.g1L1kqg91511@apollo.backplane.com> References: <200202181912.g1IJCGK32122@apollo.backplane.com> <20020218114326.A98974@dragon.nuxi.com> <200202181951.g1IJpip33604@apollo.backplane.com> <20020218153807.E96115@locore.ca> <20020221111915.N65817@wantadilla.lemis.com>
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:On Monday, 18 February 2002 at 15:38:07 -0500, Jake Burkholder wrote:
:> Apparently, On Mon, Feb 18, 2002 at 11:51:44AM -0800,
:> Matthew Dillon said words to the effect of;
:>> I'm fairly sure JHB does not have a patch to address this but, please,
:>> be my guest and check P4.
:>
:> Actually he does. Maybe you should have checked p4 first yourself.
:
:Well, maybe, like me, he doesn't know how. I only recently learnt of
:the existence of this repo, and I still don't know where it is. It
:certainly wasn't announced on the SMP mailing list. I've seen a few
:references to p4 there, but no indication of how to access the repo.
:
:> What John's patch does is spin while the lock owner is running on
:> another cpu. Spinning while there are no other processes on the run
:> queues as well makes sense but you'll also be doing a lot of
:> acquires and releases of sched_lock.
:
:I must be misinterpreting this statement. Under what circumstances do
:you spin? Yes, I read the "while the owner is running in another
:CPU", but the way I read that, it turns the blocking lock into a spin
:lock.
:
:Greg
I'm not interested in using P4. I think it's a mistake. That is, I
think it is being severely overused. At the very least it is preventing
me from comitting simple things to -current because as far as I can tell
when you add up the junk sitting in P4 it touches almost every file
in the kernel tree. Everything I've tried to work on has some hack
sitting in P4 somewhere that somebody hasn't committed.
Well, that sucks folks. I want to be able to work on -current. There
are literally 20 or 30 procedures that I can document and/or instrument
Giant in and commit to the main tree trivially, with almost no chance of
breaking someone and I want to do that to get those routines out of the
way.
I have no interest in taking what should be a day's worth of work and
stretching out into one or two weeks due to having to check P4 to see
what hacks other people might have left sitting there for weeks or months
(half of it stale now). It is a supreme waste of time.
I would like to see John commit his ucred stuff with Giant
instrumentation. If he doesn't want to do it then I would like him
to give me permission to do it from my tree now. I see no reason why
we should have to wait another X days or weeks to see this stuff in
the main tree. It just makes no sense to me.
-Matt
Matthew Dillon
<dillon@backplane.com>
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