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dm thin: performance improvement to discard processing

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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: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2014-09-12 11:34:01 +01:00 committed by Mike Snitzer
parent 36f12aeb71
commit 7a7e97ca58
1 changed files with 3 additions and 7 deletions
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10
drivers/md/dm-thin.c
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@ -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);