From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: [patch 06/10 v3] raid5: reduce chance release_stripe() taking device_lock Date: Mon, 25 Jun 2012 15:24:53 +0800 Message-ID: <20120625072641.504876596@kernel.org> References: <20120625072447.268095276@kernel.org> Return-path: Content-Disposition: inline; filename=raid5-reduce-release_stripe-lock.patch Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org Cc: neilb@suse.de, axboe@kernel.dk, dan.j.williams@intel.com, shli@fusionio.com List-Id: linux-raid.ids release_stripe() is a place conf->device_lock is heavily contended. We take the lock even stripe count isn't 1, which isn't required. Signed-off-by: Shaohua Li --- drivers/md/raid5.c | 73 +++++++++++++++++++++++++++++------------------------ 1 file changed, 40 insertions(+), 33 deletions(-) Index: linux/drivers/md/raid5.c =================================================================== --- linux.orig/drivers/md/raid5.c 2012-06-25 14:37:21.000000000 +0800 +++ linux/drivers/md/raid5.c 2012-06-25 14:38:13.899130571 +0800 @@ -196,49 +196,56 @@ static int stripe_operations_active(stru test_bit(STRIPE_COMPUTE_RUN, &sh->state); } -static void __release_stripe(struct r5conf *conf, struct stripe_head *sh) +static void handle_release_stripe(struct r5conf *conf, struct stripe_head *sh) { - if (atomic_dec_and_test(&sh->count)) { - BUG_ON(!list_empty(&sh->lru)); - BUG_ON(atomic_read(&conf->active_stripes)==0); - if (test_bit(STRIPE_HANDLE, &sh->state)) { - if (test_bit(STRIPE_DELAYED, &sh->state) && - !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) - list_add_tail(&sh->lru, &conf->delayed_list); - else if (test_bit(STRIPE_BIT_DELAY, &sh->state) && - sh->bm_seq - conf->seq_write > 0) - list_add_tail(&sh->lru, &conf->bitmap_list); - else { - clear_bit(STRIPE_DELAYED, &sh->state); - clear_bit(STRIPE_BIT_DELAY, &sh->state); - list_add_tail(&sh->lru, &conf->handle_list); - } - md_wakeup_thread(conf->mddev->thread); - } else { - BUG_ON(stripe_operations_active(sh)); - if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) - if (atomic_dec_return(&conf->preread_active_stripes) - < IO_THRESHOLD) - md_wakeup_thread(conf->mddev->thread); - atomic_dec(&conf->active_stripes); - if (!test_bit(STRIPE_EXPANDING, &sh->state)) { - list_add_tail(&sh->lru, &conf->inactive_list); - wake_up(&conf->wait_for_stripe); - if (conf->retry_read_aligned) - md_wakeup_thread(conf->mddev->thread); - } + BUG_ON(!list_empty(&sh->lru)); + BUG_ON(atomic_read(&conf->active_stripes)==0); + if (test_bit(STRIPE_HANDLE, &sh->state)) { + if (test_bit(STRIPE_DELAYED, &sh->state) && + !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) + list_add_tail(&sh->lru, &conf->delayed_list); + else if (test_bit(STRIPE_BIT_DELAY, &sh->state) && + sh->bm_seq - conf->seq_write > 0) + list_add_tail(&sh->lru, &conf->bitmap_list); + else { + clear_bit(STRIPE_DELAYED, &sh->state); + clear_bit(STRIPE_BIT_DELAY, &sh->state); + list_add_tail(&sh->lru, &conf->handle_list); + } + md_wakeup_thread(conf->mddev->thread); + } else { + BUG_ON(stripe_operations_active(sh)); + if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) + if (atomic_dec_return(&conf->preread_active_stripes) + < IO_THRESHOLD) + md_wakeup_thread(conf->mddev->thread); + atomic_dec(&conf->active_stripes); + if (!test_bit(STRIPE_EXPANDING, &sh->state)) { + list_add_tail(&sh->lru, &conf->inactive_list); + wake_up(&conf->wait_for_stripe); + if (conf->retry_read_aligned) + md_wakeup_thread(conf->mddev->thread); } } } +static void __release_stripe(struct r5conf *conf, struct stripe_head *sh) +{ + if (atomic_dec_and_test(&sh->count)) + handle_release_stripe(conf, sh); +} + static void release_stripe(struct stripe_head *sh) { struct r5conf *conf = sh->raid_conf; unsigned long flags; - spin_lock_irqsave(&conf->device_lock, flags); - __release_stripe(conf, sh); - spin_unlock_irqrestore(&conf->device_lock, flags); + local_irq_save(flags); + if (atomic_dec_and_lock(&sh->count, &conf->device_lock)) { + handle_release_stripe(conf, sh); + spin_unlock(&conf->device_lock); + } + local_irq_restore(flags); } static inline void remove_hash(struct stripe_head *sh)