higher speed mutexes

Petri Helenius pete at he.iki.fi
Thu Jan 6 09:15:59 GMT 2005

David Xu wrote:

> I will have low overhead pthread library available soon, for
> simple mutex, it is only an atomic_cmpset_long() plus a function
> call (pthread_mutex_lock) overhead.
Sounds great. Will this change the performance of rwlocks or is simple 
mutex preferred for performance sensitive applications?
Is this something that I could drop on top of RELENG_5 or RELENG_5_3 or 
is CURRENT required?
Do you have this in some public depository already?


> David Xu
> Petri Helenius wrote:
>> Hi,
>> I have some low-contention mutexes which I'm trying to make perform 
>> better and I'm wondering if the current threading library does have 
>> some primitives I could use or if I'm better off using 
>> atomic_cmpset_* and pthread_yield() if the thread hit's contention 
>> (which should be about 1:10000 of the lock/unlock operation).
>> Any scheduling caveats from above, except obviously it would spin 
>> while waiting for the lock. Most systems I plan on running this on 
>> have dual-hypethreading CPU's.
>> I remember there were some discussion about dropping i386 compatible 
>> support for mutexes and using atomic operations instead. Is there 
>> code/compile time options for this on a branch I could check out and 
>> give it a spin?
>> Pete
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