Date: Tue, 02 Nov 2004 10:09:37 +0100 From: Andre Oppermann <andre@freebsd.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/i386 pmap.c Message-ID: <41874ED1.662A02@freebsd.org> References: <200410291910.i9TJAlNf089795@repoman.freebsd.org> <200410291549.17355.jhb@FreeBSD.org> <20041029174131.A6530@odysseus.silby.com> <200411011434.28141.jhb@FreeBSD.org>
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John Baldwin wrote: > > That's very easy, it's just critical_enter/exit() without the > cpu_critical_*(). As mentioned in the SMP "design doc", the cpu_critical_*() > are only needed for spin mutexes that are used in both top-half and > bottom-half code (where ithreads are top-half, but "fast" interrupts and the > code that schedules ithreads are bottom-half). I've thought about shoving > cpu_critical_*() off into another API that spin mutexes would use, but that > not all critical sections would use, this would give us critical sections > that don't block interrupts, but just block preempting. For idle page > zeroing though, I'm not sure we really want to use even a cheap critical > section since it would still defer an ithread from running, and ithreads are > more important than idle page zeroing. > > Note that you can easily pin the current thread to its current CPU via > sched_pin/unpin() and that that works across preemptions. Does this involve any mutexes or so? This is very interesting for a couple of cases in the network stack which uses a lot of heavy-weight mutexes at the moment. -- Andre
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