[PATCH 2/2] powerpc: Optimize lock elision for pthread_mutex_t

[Tulio Magno Quites Machado Filho]

"Paul E. Murphy" <murphyp@linux.vnet.ibm.com> writes:

> With TLE enabled, the adapt count variable update incurs
> an 8% overhead before entering the critical section of an
> elided mutex.
>
> Instead, if it is done right after leaving the critical
> section, this serialization can be avoided.
>
> This alters the existing behavior of __lll_trylock_elision
> as it will only decrement the adapt_count if it successfully
> acquires the lock.
>
> 2015-09-01  Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
> 	* sysdeps/unix/sysv/linux/powerpc/elision-lock.c
> 	(__lll_lock_elision): Remove adapt_count decrement...
> 	* sysdeps/unix/sysv/linux/powerpc/elision-trylock.c
> 	(__lll_trylock_elision): Likewise.
> 	* sysdeps/unix/sysv/linux/powerpc/elision-unlock.c
> 	(__lll_unlock_elision): ... to here. And utilize
> 	new adapt_count parameter.
> 	* sysdeps/unix/sysv/linux/powerpc/lowlevellock.h
> 	(__lll_unlock_elision): Update to include adapt_count
> 	parameter.
> 	(lll_unlock_elision): Pass pointer to adapt_count
> 	variable.

LGTM.

I'm pushing it.

Thanks!

-- 
Tulio Magno