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Commit bfc90cb0 authored by Shaohua Li's avatar Shaohua Li Committed by NeilBrown
Browse files

raid5: only wakeup necessary threads 



If there are not enough stripes to handle, we'd better not always
queue all available work_structs. If one worker can only handle small
or even none stripes, it will impact request merge and create lock
contention.

With this patch, the number of work_struct running will depend on
pending stripes number. Note: some statistics info used in the patch
are accessed without locking protection. This should doesn't matter,
we just try best to avoid queue unnecessary work_struct.

Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 4d77e3ba

drivers/md/raid5.c

+35 −6
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ static struct workqueue_struct *raid5_wq; 
#define BYPASS_THRESHOLD	1

#define NR_HASH			(PAGE_SIZE / sizeof(struct hlist_head))

#define HASH_MASK		(NR_HASH - 1)

#define MAX_STRIPE_BATCH	8



static inline struct hlist_head *stripe_hash(struct r5conf *conf, sector_t sect)

{
@@ -209,6 +210,7 @@ static void raid5_wakeup_stripe_thread(struct stripe_head *sh) 
{

	struct r5conf *conf = sh->raid_conf;

	struct r5worker_group *group;

	int thread_cnt;

	int i, cpu = sh->cpu;



	if (!cpu_online(cpu)) {
@@ -220,6 +222,8 @@ static void raid5_wakeup_stripe_thread(struct stripe_head *sh) 
		struct r5worker_group *group;

		group = conf->worker_groups + cpu_to_group(cpu);

		list_add_tail(&sh->lru, &group->handle_list);

		group->stripes_cnt++;

		sh->group = group;

	}



	if (conf->worker_cnt_per_group == 0) {
@@ -229,8 +233,20 @@ static void raid5_wakeup_stripe_thread(struct stripe_head *sh) 


	group = conf->worker_groups + cpu_to_group(sh->cpu);



	for (i = 0; i < conf->worker_cnt_per_group; i++)

		queue_work_on(sh->cpu, raid5_wq, &group->workers[i].work);

	group->workers[0].working = true;

	/* at least one worker should run to avoid race */

	queue_work_on(sh->cpu, raid5_wq, &group->workers[0].work);



	thread_cnt = group->stripes_cnt / MAX_STRIPE_BATCH - 1;

	/* wakeup more workers */

	for (i = 1; i < conf->worker_cnt_per_group && thread_cnt > 0; i++) {

		if (group->workers[i].working == false) {

			group->workers[i].working = true;

			queue_work_on(sh->cpu, raid5_wq,

				      &group->workers[i].work);

			thread_cnt--;

		}

	}

}



static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh)
@@ -589,6 +605,10 @@ get_active_stripe(struct r5conf *conf, sector_t sector, 
				    !test_bit(STRIPE_EXPANDING, &sh->state))

					BUG();

				list_del_init(&sh->lru);

				if (sh->group) {

					sh->group->stripes_cnt--;

					sh->group = NULL;

				}

			}

		}

	} while (sh == NULL);
@@ -4153,15 +4173,18 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group) 
{

	struct stripe_head *sh = NULL, *tmp;

	struct list_head *handle_list = NULL;

	struct r5worker_group *wg = NULL;



	if (conf->worker_cnt_per_group == 0) {

		handle_list = &conf->handle_list;

	} else if (group != ANY_GROUP) {

		handle_list = &conf->worker_groups[group].handle_list;

		wg = &conf->worker_groups[group];

	} else {

		int i;

		for (i = 0; i < conf->group_cnt; i++) {

			handle_list = &conf->worker_groups[i].handle_list;

			wg = &conf->worker_groups[i];

			if (!list_empty(handle_list))

				break;

		}
@@ -4208,11 +4231,16 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group) 
			if (conf->bypass_count < 0)

				conf->bypass_count = 0;

		}

		wg = NULL;

	}



	if (!sh)

		return NULL;



	if (wg) {

		wg->stripes_cnt--;

		sh->group = NULL;

	}

	list_del_init(&sh->lru);

	atomic_inc(&sh->count);

	BUG_ON(atomic_read(&sh->count) != 1);
@@ -4919,8 +4947,8 @@ static int retry_aligned_read(struct r5conf *conf, struct bio *raid_bio) 
	return handled;

}



#define MAX_STRIPE_BATCH 8

static int handle_active_stripes(struct r5conf *conf, int group)

static int handle_active_stripes(struct r5conf *conf, int group,

				 struct r5worker *worker)

{

	struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;

	int i, batch_size = 0;
@@ -4963,7 +4991,8 @@ static void raid5_do_work(struct work_struct *work) 


		released = release_stripe_list(conf);



		batch_size = handle_active_stripes(conf, group_id);

		batch_size = handle_active_stripes(conf, group_id, worker);

		worker->working = false;

		if (!batch_size && !released)

			break;

		handled += batch_size;
@@ -5025,7 +5054,7 @@ static void raid5d(struct md_thread *thread) 
			handled++;

		}



		batch_size = handle_active_stripes(conf, ANY_GROUP);

		batch_size = handle_active_stripes(conf, ANY_GROUP, NULL);

		if (!batch_size && !released)

			break;

		handled += batch_size;

drivers/md/raid5.h

+3 −0
Original line number Diff line number Diff line
@@ -213,6 +213,7 @@ struct stripe_head { 
	enum reconstruct_states reconstruct_state;

	spinlock_t		stripe_lock;

	int			cpu;

	struct r5worker_group	*group;

	/**

	 * struct stripe_operations

	 * @target - STRIPE_OP_COMPUTE_BLK target
@@ -369,12 +370,14 @@ struct disk_info { 
struct r5worker {

	struct work_struct work;

	struct r5worker_group *group;

	bool working;

};



struct r5worker_group {

	struct list_head handle_list;

	struct r5conf *conf;

	struct r5worker *workers;

	int stripes_cnt;

};



struct r5conf {