Date: Mon, 18 Feb 2002 12:43:18 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Jake Burkholder <jake@locore.ca> Cc: "David O'Brien" <obrien@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: Patch to improve mutex collision performance Message-ID: <200202182043.g1IKhIc36298@apollo.backplane.com> References: <200202181912.g1IJCGK32122@apollo.backplane.com> <20020218114326.A98974@dragon.nuxi.com> <200202181951.g1IJpip33604@apollo.backplane.com> <20020218153807.E96115@locore.ca>
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: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. Ah, critnest... you are right. I should be checking for
critnest > 1.
-Matt
Matthew Dillon
<dillon@backplane.com>
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