Re: [PATCH v7] libgfortran: Replace mutex with rwlock

[Jakub Jelinek <jakub@redhat.com>]

On Sat, Dec 09, 2023 at 10:39:45AM -0500, Lipeng Zhu wrote:
> This patch try to introduce the rwlock and split the read/write to
> unit_root tree and unit_cache with rwlock instead of the mutex to
> increase CPU efficiency. In the get_gfc_unit function, the percentage
> to step into the insert_unit function is around 30%, in most instances,
> we can get the unit in the phase of reading the unit_cache or unit_root
> tree. So split the read/write phase by rwlock would be an approach to
> make it more parallel.
> 
> BTW, the IPC metrics can gain around 9x in our test
> server with 220 cores. The benchmark we used is
> https://github.com/rwesson/NEAT
> 
> libgcc/ChangeLog:
> 
> 	* gthr-posix.h (__GTHREAD_RWLOCK_INIT): New macro.
> 	(__gthrw): New function.
> 	(__gthread_rwlock_rdlock): New function.
> 	(__gthread_rwlock_tryrdlock): New function.
> 	(__gthread_rwlock_wrlock): New function.
> 	(__gthread_rwlock_trywrlock): New function.
> 	(__gthread_rwlock_unlock): New function.
> 
> libgfortran/ChangeLog:
> 
> 	* io/async.c (DEBUG_LINE): New macro.
> 	* io/async.h (RWLOCK_DEBUG_ADD): New macro.
> 	(CHECK_RDLOCK): New macro.
> 	(CHECK_WRLOCK): New macro.
> 	(TAIL_RWLOCK_DEBUG_QUEUE): New macro.
> 	(IN_RWLOCK_DEBUG_QUEUE): New macro.
> 	(RDLOCK): New macro.
> 	(WRLOCK): New macro.
> 	(RWUNLOCK): New macro.
> 	(RD_TO_WRLOCK): New macro.
> 	(INTERN_RDLOCK): New macro.
> 	(INTERN_WRLOCK): New macro.
> 	(INTERN_RWUNLOCK): New macro.
> 	* io/io.h (struct gfc_unit): Change UNIT_LOCK to UNIT_RWLOCK in
> 	a comment.
> 	(unit_lock): Remove including associated internal_proto.
> 	(unit_rwlock): New declarations including associated internal_proto.
> 	(dec_waiting_unlocked): Use WRLOCK and RWUNLOCK on unit_rwlock
> 	instead of __gthread_mutex_lock and __gthread_mutex_unlock on
> 	unit_lock.
> 	* io/transfer.c (st_read_done_worker): Use WRLOCK and RWUNLOCK on
> 	unit_rwlock instead of LOCK and UNLOCK on unit_lock.
> 	(st_write_done_worker): Likewise.
> 	* io/unit.c: Change UNIT_LOCK to UNIT_RWLOCK in 'IO locking rules'
> 	comment. Use unit_rwlock variable instead of unit_lock variable.
> 	(get_gfc_unit_from_unit_root): New function.
> 	(get_gfc_unit): Use RDLOCK, WRLOCK and RWUNLOCK on unit_rwlock
> 	instead of LOCK and UNLOCK on unit_lock.
> 	(close_unit_1): Use WRLOCK and RWUNLOCK on unit_rwlock instead of
> 	LOCK and UNLOCK on unit_lock.
> 	(close_units): Likewise.
> 	(newunit_alloc): Use RWUNLOCK on unit_rwlock instead of UNLOCK on
> 	unit_lock.
> 	* io/unix.c (find_file): Use RDLOCK and RWUNLOCK on unit_rwlock
> 	instead of LOCK and UNLOCK on unit_lock.
> 	(flush_all_units): Use WRLOCK and RWUNLOCK on unit_rwlock instead
> 	of LOCK and UNLOCK on unit_lock.

Ok for trunk, thanks.

	Jakub