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Commit 7a7e97ca authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
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dm thin: performance improvement to discard processing 



When processing a discard bio, if the block is already quiesced do the
discard immediately rather than adding the mapping to a list for the
next iteration of the worker thread.

Discarding a fully provisioned 100G thin volume with 64k block size goes
from 860s to 95s with this change.

Clearly there's something wrong with the worker architecture, more
investigation needed.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 36f12aeb

drivers/md/dm-thin.c

+3 −7
Original line number Diff line number Diff line
@@ -1194,7 +1194,6 @@ static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *c 
static void process_discard(struct thin_c *tc, struct bio *bio)

{

	int r;

	unsigned long flags;

	struct pool *pool = tc->pool;

	struct dm_bio_prison_cell *cell, *cell2;

	struct dm_cell_key key, key2;
@@ -1235,12 +1234,9 @@ static void process_discard(struct thin_c *tc, struct bio *bio) 
			m->cell2 = cell2;

			m->bio = bio;



			if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list)) {

				spin_lock_irqsave(&pool->lock, flags);

				list_add_tail(&m->list, &pool->prepared_discards);

				spin_unlock_irqrestore(&pool->lock, flags);

				wake_worker(pool);

			}

			if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list))

				pool->process_prepared_discard(m);



		} else {

			inc_all_io_entry(pool, bio);

			cell_defer_no_holder(tc, cell);