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

["H.J. Lu" <hjl.tools@gmail.com>]

On Sat, Dec 9, 2023 at 7:25 PM Zhu, Lipeng <lipeng.zhu@intel.com> wrote:
>
> On 2023/12/9 23:23, Jakub Jelinek wrote:
> > 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
>
> Thanks! Looking forward to landing to trunk.
>
> Lipeng Zhu

Pushed for you.

Thanks.

-- 
H.J.