Date: Tue, 6 Apr 2004 23:41:15 -0400 (EDT) From: Jeff Roberson <jroberson@chesapeake.net> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/conf options src/sys/kern kern_mutex.c Message-ID: <20040406234035.U72393@mail.chesapeake.net> In-Reply-To: <200404061912.i36JCP1m036228@repoman.freebsd.org> References: <200404061912.i36JCP1m036228@repoman.freebsd.org>
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On Tue, 6 Apr 2004, John Baldwin wrote: > jhb 2004/04/06 12:12:25 PDT > > FreeBSD src repository > > Modified files: > sys/conf options > sys/kern kern_mutex.c > Log: > Add a new kernel option MUTEX_WAKE_ALL that changes the mutex unlock code > to awaken all waiters when a contested mutex is released instead of just > the highest priority waiter. If the various threads are awakened in > sequence then each thread may acquire and release the lock in question > without contention resulting in fewer expensive unlock and lock > operations. This old behavior of waking just the highest priority is > still used if this option is specified. Making the algorithm conditional > on a kernel option will allows us to benchmark both cases later and > determine which one should be used by default. This seems like an optimization on UP and a pessimization on SMP. Perhaps you should make it conditional on mp_ncpus? > > Requested by: tanimura-san > > Revision Changes Path > 1.439 +1 -0 src/sys/conf/options > 1.138 +10 -0 src/sys/kern/kern_mutex.c >
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