Re: Using POSIX mutex-es

Added to TODO.detail/performance.

> 1. Just changed
>     TAS(lock) to pthread_mutex_trylock(lock)
>     S_LOCK(lock) to pthread_mutex_lock(lock)
>     S_UNLOCK(lock) to pthread_mutex_unlock(lock)
> (and S_INIT_LOCK to share mutex-es between processes).
> 
> 2. pgbench was initialized with scale 10.
>    SUN WS 10 (512Mb), Solaris 2.6 (I'm unable to test on E4500 -:()
>    -B 16384, wal_files 8, wal_buffers 256,
>    checkpoint_segments 64, checkpoint_timeout 3600
>    50 clients x 100 transactions
>    (after initialization DB dir was saved and before each test
>     copyed back and vacuum-ed).
> 
> 3. No difference.
>    Mutex version maybe 0.5-1 % faster (eg: 37.264238 tps vs 37.083339 tps).
> 
> So - no gain, but no performance loss "from using pthread library"
> (I've also run tests with 1 client), at least on Solaris.
> 
> And so - looks like we can use POSIX mutex-es and conditional variables
> (not semaphores; man pthread_cond_wait) and should implement light lmgr,
> probably with priority locking.
> 
> Vadim
> 
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