On Tue, 3 Jan 2006, John Baldwin wrote: > On Sunday 01 January 2006 02:21 am, prime wrote: > > Hi hackers, > > I have an idea about remove the kernel option MUTEX_WAKE_ALL. > > When we unlock the mutex(in _mtx_unlock_sleep),we can directly > > give the lock to the first thread waiting on the turnstile.And a > > thread gets the mutex after he returned from turnstile_wait so he > > can simply jump out the _obtain_lock loop in _mtx_lock_sleep. > > This makes a mutex always be owned by a thread when there are threads > > waiting on the turnstile,so priority inheritance can work now. > > This idea need only a few changes in kern/kern_mutex.c .But when > > NO_ADAPTIVE_MUTEXS not set,it makes threads that spinning on other CPU > > to get the mutex have to spin for a long time,and this makes the short > > term mutex more expensive(maybe should use spin mutex instead). > > > > What do think about the idea? Thanks. > > Sun actually found that the performance was better when you did MUTEX_WAKE_ALL > because once you woke up N threads, if they don't all resume at once then > they will acquire the lock in sequence and the lock acquires and releaes will > all be simple ones rather than all being the complicated contested case. > There are more details in _Solaris Internals_.
Yes, but doesn't this partly rely on having the threads spin(*) for a bit if the current lock owner is running on another CPU? Do we currently do that? (*) No, I am not referring to spin mutexes. -- DE _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
