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Commit 8811b596 authored by Shaohua Li's avatar Shaohua Li Committed by NeilBrown
Browse files

raid5: make_request use batch stripe release 



make_request() does stripe release for every stripe and the stripe usually has
count 1, which makes previous release_stripe() optimization not work. In my
test, this release_stripe() becomes the heaviest pleace to take
conf->device_lock after previous patches applied.

Below patch makes stripe release batch. All the stripes will be released in
unplug. The STRIPE_ON_UNPLUG_LIST bit is to protect concurrent access stripe
lru.

Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 74018dc3

drivers/md/raid5.c

+59 −3
Original line number Diff line number Diff line
@@ -471,7 +471,8 @@ get_active_stripe(struct r5conf *conf, sector_t sector, 
		} else {

			if (atomic_read(&sh->count)) {

				BUG_ON(!list_empty(&sh->lru)

				    && !test_bit(STRIPE_EXPANDING, &sh->state));

				    && !test_bit(STRIPE_EXPANDING, &sh->state)

				    && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state));

			} else {

				if (!test_bit(STRIPE_HANDLE, &sh->state))

					atomic_inc(&conf->active_stripes);
@@ -3988,6 +3989,62 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf) 
	return sh;

}



struct raid5_plug_cb {

	struct blk_plug_cb	cb;

	struct list_head	list;

};



static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)

{

	struct raid5_plug_cb *cb = container_of(

		blk_cb, struct raid5_plug_cb, cb);

	struct stripe_head *sh;

	struct mddev *mddev = cb->cb.data;

	struct r5conf *conf = mddev->private;



	if (cb->list.next && !list_empty(&cb->list)) {

		spin_lock_irq(&conf->device_lock);

		while (!list_empty(&cb->list)) {

			sh = list_first_entry(&cb->list, struct stripe_head, lru);

			list_del_init(&sh->lru);

			/*

			 * avoid race release_stripe_plug() sees

			 * STRIPE_ON_UNPLUG_LIST clear but the stripe

			 * is still in our list

			 */

			smp_mb__before_clear_bit();

			clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);

			__release_stripe(conf, sh);

		}

		spin_unlock_irq(&conf->device_lock);

	}

	kfree(cb);

}



static void release_stripe_plug(struct mddev *mddev,

				struct stripe_head *sh)

{

	struct blk_plug_cb *blk_cb = blk_check_plugged(

		raid5_unplug, mddev,

		sizeof(struct raid5_plug_cb));

	struct raid5_plug_cb *cb;



	if (!blk_cb) {

		release_stripe(sh);

		return;

	}



	cb = container_of(blk_cb, struct raid5_plug_cb, cb);



	if (cb->list.next == NULL)

		INIT_LIST_HEAD(&cb->list);



	if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))

		list_add_tail(&sh->lru, &cb->list);

	else

		release_stripe(sh);

}



static void make_request(struct mddev *mddev, struct bio * bi)

{

	struct r5conf *conf = mddev->private;
@@ -4116,8 +4173,7 @@ static void make_request(struct mddev *mddev, struct bio * bi) 
			if ((bi->bi_rw & REQ_SYNC) &&

			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))

				atomic_inc(&conf->preread_active_stripes);

			mddev_check_plugged(mddev);

			release_stripe(sh);

			release_stripe_plug(mddev, sh);

		} else {

			/* cannot get stripe for read-ahead, just give-up */

			clear_bit(BIO_UPTODATE, &bi->bi_flags);

drivers/md/raid5.h

+1 −0
Original line number Diff line number Diff line
@@ -319,6 +319,7 @@ enum { 
	STRIPE_BIOFILL_RUN,

	STRIPE_COMPUTE_RUN,

	STRIPE_OPS_REQ_PENDING,

	STRIPE_ON_UNPLUG_LIST,

};



/*