diff options
| author | Waiman Long <longman@redhat.com> | 2019-04-04 13:43:19 -0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-04-10 10:56:06 +0200 |
| commit | a8654596f0371c2604c4d475422c48f4fc6a56c9 (patch) | |
| tree | 6d021c1c7c2d39594ad5f080059920949afd8160 /kernel/locking/rwsem.h | |
| parent | bf20616f46e536fe8affed6f138db4b3040b55a6 (diff) | |
locking/rwsem: Enable lock event counting
Add lock event counting calls so that we can track the number of lock
events happening in the rwsem code.
With CONFIG_LOCK_EVENT_COUNTS on and booting a 4-socket 112-thread x86-64
system, the rwsem counts after system bootup were as follows:
rwsem_opt_fail=261
rwsem_opt_wlock=50636
rwsem_rlock=445
rwsem_rlock_fail=0
rwsem_rlock_fast=22
rwsem_rtrylock=810144
rwsem_sleep_reader=441
rwsem_sleep_writer=310
rwsem_wake_reader=355
rwsem_wake_writer=2335
rwsem_wlock=261
rwsem_wlock_fail=0
rwsem_wtrylock=20583
It can be seen that most of the lock acquisitions in the slowpath were
write-locks in the optimistic spinning code path with no sleeping at
all. For this system, over 97% of the locks are acquired via optimistic
spinning. It illustrates the importance of optimistic spinning in
improving the performance of rwsem.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-11-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking/rwsem.h')
| -rw-r--r-- | kernel/locking/rwsem.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h index 3059a2dc39f8..37db17890e36 100644 --- a/kernel/locking/rwsem.h +++ b/kernel/locking/rwsem.h @@ -23,6 +23,8 @@ * is involved. Ideally we would like to track all the readers that own * a rwsem, but the overhead is simply too big. */ +#include "lock_events.h" + #define RWSEM_READER_OWNED (1UL << 0) #define RWSEM_ANONYMOUSLY_OWNED (1UL << 1) @@ -200,6 +202,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) */ long tmp = RWSEM_UNLOCKED_VALUE; + lockevent_inc(rwsem_rtrylock); do { if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, tmp + RWSEM_ACTIVE_READ_BIAS)) { @@ -241,6 +244,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem) { long tmp; + lockevent_inc(rwsem_wtrylock); tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS); if (tmp == RWSEM_UNLOCKED_VALUE) { |