Date: Wed, 17 Nov 2004 21:30:02 +0200 From: Petri Helenius <pete@he.iki.fi> To: Daniel Eischen <deischen@freebsd.org> Cc: freebsd-threads@freebsd.org Subject: Re: mutex performance Message-ID: <419BA6BA.4060304@he.iki.fi> In-Reply-To: <Pine.GSO.4.43.0411171409360.3786-100000@sea.ntplx.net> References: <Pine.GSO.4.43.0411171409360.3786-100000@sea.ntplx.net>
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Daniel Eischen wrote: >On Wed, 17 Nov 2004, Petri Helenius wrote: > > > >>Do you feel that mutex performance could be improved from the current >>2-3 million lock/unlock operations per second on uncontested mutexes on >>~2.4Ghz prescott? Which seems to be about 1000 cycles per lock/unlock. >> >> > >I'm not sure what you're trying to say above. > > I have this: #include <pthread.h> main() { register int i; pthread_mutexattr_t attr; pthread_mutex_t onepacket; pthread_mutexattr_init (&attr); pthread_mutexattr_settype (&attr,PTHREAD_MUTEX_ERRORCHECK); pthread_mutex_init (&onepacket,&attr); for (i = 0; i < 20000000;i++) { pthread_mutex_lock (&onepacket); pthread_mutex_unlock (&onepacket); } } And run it: > gcc -O3 -std=c99 -g -march=pentiumpro mutextest.c -o mutextest -lthr > time ./mutextest 12.291u 0.000s 0:12.29 100.0% 5+189k 0+0io 0pf+0w > gcc -O3 -std=c99 -g -march=pentiumpro mutextest.c -o mutextest -lpthread > time ./mutextest 7.008u 0.000s 0:07.01 99.8% 5+230k 0+0io 0pf+0w > gcc -O3 -std=c99 -g -march=pentiumpro mutextest.c -o mutextest -lc_r > time ./mutextest 5.887u 0.000s 0:05.88 100.0% 5+389k 0+0io 0pf+0w And I'm wondering how much I need to engineer around mutexes or holding them for longer and releasing just before yielding. I'm not saying it should/must be better, just trying to ask for the feel where to go. >I want to change libpthread locks to drop the 80386 support >and just use the atomic primitives for default mutex types. >In 6.0, we'll also change all the mutexes, CVs, and semaphores >so they aren't pointers -- that will save an indirection and >also allow them to be process shared. > > Do you have patches or is this on planning stage? Pete
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