diff options
| author | Tomasz Majchrzak <tomasz.majchrzak@intel.com> | 2016-06-24 15:20:16 +0300 |
|---|---|---|
| committer | Shaohua Li <shli@fb.com> | 2016-07-20 01:20:28 +0300 |
| commit | 0e5313e2d4ef93bdf6c22dad647d28635b86472a (patch) | |
| tree | b470429e5ae7c501d920a12550bf76592bac04d0 | |
| parent | 573275b58ee9e1d2ec89f9608060f58931c3cde3 (diff) | |
| download | linux-0e5313e2d4ef93bdf6c22dad647d28635b86472a.tar.xz | |
raid10: improve random reads performance
RAID10 random read performance is lower than expected due to excessive spinlock
utilisation which is required mostly for rebuild/resync. Simplify allow_barrier
as it's in IO path and encounters a lot of unnecessary congestion.
As lower_barrier just takes a lock in order to decrement a counter, convert
counter (nr_pending) into atomic variable and remove the spin lock. There is
also a congestion for wake_up (it uses lock internally) so call it only when
it's really needed. As wake_up is not called constantly anymore, ensure process
waiting to raise a barrier is notified when there are no more waiting IOs.
Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
| -rw-r--r-- | drivers/md/raid10.c | 21 | ||||
| -rw-r--r-- | drivers/md/raid10.h | 3 |
2 files changed, 14 insertions, 10 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index f7f3c8a63419..cb1d88709ff0 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -905,7 +905,7 @@ static void raise_barrier(struct r10conf *conf, int force) /* Now wait for all pending IO to complete */ wait_event_lock_irq(conf->wait_barrier, - !conf->nr_pending && conf->barrier < RESYNC_DEPTH, + !atomic_read(&conf->nr_pending) && conf->barrier < RESYNC_DEPTH, conf->resync_lock); spin_unlock_irq(&conf->resync_lock); @@ -936,23 +936,23 @@ static void wait_barrier(struct r10conf *conf) */ wait_event_lock_irq(conf->wait_barrier, !conf->barrier || - (conf->nr_pending && + (atomic_read(&conf->nr_pending) && current->bio_list && !bio_list_empty(current->bio_list)), conf->resync_lock); conf->nr_waiting--; + if (!conf->nr_waiting) + wake_up(&conf->wait_barrier); } - conf->nr_pending++; + atomic_inc(&conf->nr_pending); spin_unlock_irq(&conf->resync_lock); } static void allow_barrier(struct r10conf *conf) { - unsigned long flags; - spin_lock_irqsave(&conf->resync_lock, flags); - conf->nr_pending--; - spin_unlock_irqrestore(&conf->resync_lock, flags); - wake_up(&conf->wait_barrier); + if ((atomic_dec_and_test(&conf->nr_pending)) || + (conf->array_freeze_pending)) + wake_up(&conf->wait_barrier); } static void freeze_array(struct r10conf *conf, int extra) @@ -970,13 +970,15 @@ static void freeze_array(struct r10conf *conf, int extra) * we continue. */ spin_lock_irq(&conf->resync_lock); + conf->array_freeze_pending++; conf->barrier++; conf->nr_waiting++; wait_event_lock_irq_cmd(conf->wait_barrier, - conf->nr_pending == conf->nr_queued+extra, + atomic_read(&conf->nr_pending) == conf->nr_queued+extra, conf->resync_lock, flush_pending_writes(conf)); + conf->array_freeze_pending--; spin_unlock_irq(&conf->resync_lock); } @@ -3542,6 +3544,7 @@ static struct r10conf *setup_conf(struct mddev *mddev) spin_lock_init(&conf->resync_lock); init_waitqueue_head(&conf->wait_barrier); + atomic_set(&conf->nr_pending, 0); conf->thread = md_register_thread(raid10d, mddev, "raid10"); if (!conf->thread) diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h index 6fc2c75759bf..18ec1f7a98bf 100644 --- a/drivers/md/raid10.h +++ b/drivers/md/raid10.h @@ -64,10 +64,11 @@ struct r10conf { int pending_count; spinlock_t resync_lock; - int nr_pending; + atomic_t nr_pending; int nr_waiting; int nr_queued; int barrier; + int array_freeze_pending; sector_t next_resync; int fullsync; /* set to 1 if a full sync is needed, * (fresh device added). |