From: Dan Williams Date: Fri, 16 Oct 2009 05:25:22 +0000 (+1100) Subject: md/raid456: downlevel multicore operations to raid_run_ops X-Git-Tag: v2.6.32-rc6~27^2~8 X-Git-Url: https://bbs.cooldavid.org/git/?a=commitdiff_plain;h=417b8d4ac868cf58d6c68f52d72f7648413e0edc;p=net-next-2.6.git md/raid456: downlevel multicore operations to raid_run_ops The percpu conversion allowed a straightforward handoff of stripe processing to the async subsytem that initially showed some modest gains (+4%). However, this model is too simplistic and leads to stripes bouncing between raid5d and the async thread pool for every invocation of handle_stripe(). As reported by Holger this can fall into a pathological situation severely impacting throughput (6x performance loss). By downleveling the parallelism to raid_run_ops the pathological stripe_head bouncing is eliminated. This version still exhibits an average 11% throughput loss for: mdadm --create /dev/md0 /dev/sd[b-q] -n 16 -l 6 echo 1024 > /sys/block/md0/md/stripe_cache_size dd if=/dev/zero of=/dev/md0 bs=1024k count=2048 ...but the results are at least stable and can be used as a base for further multicore experimentation. Reported-by: Holger Kiehl Signed-off-by: Dan Williams Signed-off-by: NeilBrown --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index c3e59677861..25c3c29134d 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -1139,7 +1139,7 @@ static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu &sh->ops.zero_sum_result, percpu->spare_page, &submit); } -static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request) +static void __raid_run_ops(struct stripe_head *sh, unsigned long ops_request) { int overlap_clear = 0, i, disks = sh->disks; struct dma_async_tx_descriptor *tx = NULL; @@ -1204,6 +1204,36 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request) put_cpu(); } +#ifdef CONFIG_MULTICORE_RAID456 +static void async_run_ops(void *param, async_cookie_t cookie) +{ + struct stripe_head *sh = param; + unsigned long ops_request = sh->ops.request; + + clear_bit_unlock(STRIPE_OPS_REQ_PENDING, &sh->state); + wake_up(&sh->ops.wait_for_ops); + + __raid_run_ops(sh, ops_request); + release_stripe(sh); +} + +static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request) +{ + /* since handle_stripe can be called outside of raid5d context + * we need to ensure sh->ops.request is de-staged before another + * request arrives + */ + wait_event(sh->ops.wait_for_ops, + !test_and_set_bit_lock(STRIPE_OPS_REQ_PENDING, &sh->state)); + sh->ops.request = ops_request; + + atomic_inc(&sh->count); + async_schedule(async_run_ops, sh); +} +#else +#define raid_run_ops __raid_run_ops +#endif + static int grow_one_stripe(raid5_conf_t *conf) { struct stripe_head *sh; @@ -1213,6 +1243,9 @@ static int grow_one_stripe(raid5_conf_t *conf) memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev)); sh->raid_conf = conf; spin_lock_init(&sh->lock); + #ifdef CONFIG_MULTICORE_RAID456 + init_waitqueue_head(&sh->ops.wait_for_ops); + #endif if (grow_buffers(sh, conf->raid_disks)) { shrink_buffers(sh, conf->raid_disks); @@ -1329,6 +1362,9 @@ static int resize_stripes(raid5_conf_t *conf, int newsize) nsh->raid_conf = conf; spin_lock_init(&nsh->lock); + #ifdef CONFIG_MULTICORE_RAID456 + init_waitqueue_head(&nsh->ops.wait_for_ops); + #endif list_add(&nsh->lru, &newstripes); } @@ -4342,37 +4378,6 @@ static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio) return handled; } -#ifdef CONFIG_MULTICORE_RAID456 -static void __process_stripe(void *param, async_cookie_t cookie) -{ - struct stripe_head *sh = param; - - handle_stripe(sh); - release_stripe(sh); -} - -static void process_stripe(struct stripe_head *sh, struct list_head *domain) -{ - async_schedule_domain(__process_stripe, sh, domain); -} - -static void synchronize_stripe_processing(struct list_head *domain) -{ - async_synchronize_full_domain(domain); -} -#else -static void process_stripe(struct stripe_head *sh, struct list_head *domain) -{ - handle_stripe(sh); - release_stripe(sh); - cond_resched(); -} - -static void synchronize_stripe_processing(struct list_head *domain) -{ -} -#endif - /* * This is our raid5 kernel thread. @@ -4386,7 +4391,6 @@ static void raid5d(mddev_t *mddev) struct stripe_head *sh; raid5_conf_t *conf = mddev->private; int handled; - LIST_HEAD(raid_domain); pr_debug("+++ raid5d active\n"); @@ -4423,7 +4427,9 @@ static void raid5d(mddev_t *mddev) spin_unlock_irq(&conf->device_lock); handled++; - process_stripe(sh, &raid_domain); + handle_stripe(sh); + release_stripe(sh); + cond_resched(); spin_lock_irq(&conf->device_lock); } @@ -4431,7 +4437,6 @@ static void raid5d(mddev_t *mddev) spin_unlock_irq(&conf->device_lock); - synchronize_stripe_processing(&raid_domain); async_tx_issue_pending_all(); unplug_slaves(mddev); diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index 2390e0e83da..dcefdc9629e 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -214,12 +214,20 @@ struct stripe_head { int disks; /* disks in stripe */ enum check_states check_state; enum reconstruct_states reconstruct_state; - /* stripe_operations + /** + * struct stripe_operations * @target - STRIPE_OP_COMPUTE_BLK target + * @target2 - 2nd compute target in the raid6 case + * @zero_sum_result - P and Q verification flags + * @request - async service request flags for raid_run_ops */ struct stripe_operations { int target, target2; enum sum_check_flags zero_sum_result; + #ifdef CONFIG_MULTICORE_RAID456 + unsigned long request; + wait_queue_head_t wait_for_ops; + #endif } ops; struct r5dev { struct bio req; @@ -294,6 +302,8 @@ struct r6_state { #define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */ #define STRIPE_BIOFILL_RUN 14 #define STRIPE_COMPUTE_RUN 15 +#define STRIPE_OPS_REQ_PENDING 16 + /* * Operation request flags */