Date: Mon, 18 Feb 2002 16:09:07 -0500 From: Jake Burkholder <jake@locore.ca> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: "David O'Brien" <obrien@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: Patch to improve mutex collision performance Message-ID: <20020218160907.F96115@locore.ca> In-Reply-To: <200202182043.g1IKhIc36298@apollo.backplane.com>; from dillon@apollo.backplane.com on Mon, Feb 18, 2002 at 12:43:18PM -0800 References: <200202181912.g1IJCGK32122@apollo.backplane.com> <20020218114326.A98974@dragon.nuxi.com> <200202181951.g1IJpip33604@apollo.backplane.com> <20020218153807.E96115@locore.ca> <200202182043.g1IKhIc36298@apollo.backplane.com>
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Apparently, On Mon, Feb 18, 2002 at 12:43:18PM -0800, Matthew Dillon said words to the effect of; > :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. > : > :The only thing that jumped out at me looking at the patch is that critnest cannot > :be 0 here because the sched_lock is held; holding a spin lock implies being in a > :critical section. I need to think about this more and would like you to wait until > :John has a chance to look at it as well. > : > :Jake > > Sure thing. Thanks. > Ah, critnest... you are right. I should be checking for > critnest > 1. I think you should just leave it alone, don't check critnest at all. critnest != 1 is illegal because you can't acquire a sleep lock while in an enclosing critical section. Jake To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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