Date: Tue, 2 Nov 2004 15:50:25 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Andre Oppermann <andre@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/i386 pmap.c Message-ID: <200411021550.25945.jhb@FreeBSD.org> In-Reply-To: <41874ED1.662A02@freebsd.org> References: <200410291910.i9TJAlNf089795@repoman.freebsd.org> <200411011434.28141.jhb@FreeBSD.org> <41874ED1.662A02@freebsd.org>
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On Tuesday 02 November 2004 04:09 am, Andre Oppermann wrote: > 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. No, pin/unpin just bounce a per-thread private counter with no locks needed. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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