cvs commit: src/lib/libthr/thread thr_mutex.c
src/lib/libkse/thread thr_mutex.c src/include pthread.h
David Xu
bsddiy at 126.com
Tue Oct 30 06:02:44 PDT 2007
Kris Kennaway wrote:
>
> PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP is just in <pthread.h>.
>
> /*
> * Static initialization values.
> */
> #define PTHREAD_MUTEX_INITIALIZER NULL
> #define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP NULL
> #define PTHREAD_COND_INITIALIZER NULL
> #define PTHREAD_RWLOCK_INITIALIZER NULL
>
>>>> I remembered mysql uses this macro to initialize spin mutex, and you
>>>> indead needs a patch to let it work
>>>
>>>
>>> No, with the code I committed mysql detects and uses it out of the
>>> box, without requiring any patches. It is easy to measure the
>>> resulting 30% performance improvement at high loads ;-)
>>>
>> see above, I didn't see any code set PTHREAD_MUTEX_ADAPTIVE_NP type.
>
> The code is already in mysql for use with glibc. It basically does
>
> #ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
> /*
> * Use PTHREAD_MUTEX_ADAPTIVE_NP for the mutexes we know will benefit
> * from it
> */
> ...
> #endif
>
> so it just works.
>
I can not find code in libthr set mutex's member field m_type to
PTHREAD_MUTEX_ADAPTIVE_NP by your change, so how can it work as
expected ?
>> My code even needn't to recompile mysql and improve 40% performance. :-)
>
> OK, but that's not good enough. As I have mentioned, you should have
> serious concerns about performance loss in other cases with an approach
> that always spins in userland when acquiring any mutex.
>
>>> > in fact spin mutex in libthr is
>>>
>>>> arguable, normally you can use pthread_mutex_trylock() in
>>>> application to simulate spinning, adding such mutex type it in
>>>> libthr just simplified
>>>> it, but it is not portable.
>>>
>>>
>>> That is what the "_NP" indicates (although remember that this
>>> interface is compatible with glibc).
>>>
>>> Kris
>>>
>> I am waiting for others, since this is first time we have to add a new
>> mutex type.
>
> I don't understand what you are saying here. The glibc interface is
> defined by glibc, so if we want to do something different then either
> compatibility interfaces are needed (so what was the point of being
> different other than "NIH"?), or we need to manually patch the
> applications to do it "our way".
>
> Kris
>
See above, the code is not working ...
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