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author | Jeffle Xu <jefflexu@linux.alibaba.com> | 2019-11-18 04:50:38 +0300 |
---|---|---|
committer | Mike Snitzer <snitzer@redhat.com> | 2019-11-18 18:03:12 +0300 |
commit | d256d796279de0bdc227ff4daef565aa7e80c898 (patch) | |
tree | e26a7ba3db3faacf2515f0b26508c179b401525d /drivers | |
parent | d537858ac8aaf4311b51240893add2fc62003b97 (diff) | |
download | linux-d256d796279de0bdc227ff4daef565aa7e80c898.tar.xz |
dm thin: wakeup worker only when deferred bios exist
Single thread fio test (read, bs=4k, ioengine=libaio, iodepth=128,
numjobs=1) over dm-thin device has poor performance versus bare nvme
device.
Further investigation with perf indicates that queue_work_on() consumes
over 20% CPU time when doing IO over dm-thin device. The call stack is
as follows.
- 40.57% thin_map
+ 22.07% queue_work_on
+ 9.95% dm_thin_find_block
+ 2.80% cell_defer_no_holder
1.91% inc_all_io_entry.isra.33.part.34
+ 1.78% bio_detain.isra.35
In cell_defer_no_holder(), wakeup_worker() is always called, no matter
whether the tc->deferred_bio_list list is empty or not. In single thread
IO model, this list is most likely empty. So skip waking up worker thread
if tc->deferred_bio_list list is empty.
Single thread IO performance improves from 448 MiB/s to 646 MiB/s (+44%)
once the needless wake_worker() calls are properly skipped.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/md/dm-thin.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 85ada5ad2121..5a2c494cb552 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -882,12 +882,15 @@ static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *c { struct pool *pool = tc->pool; unsigned long flags; + int has_work; spin_lock_irqsave(&tc->lock, flags); cell_release_no_holder(pool, cell, &tc->deferred_bio_list); + has_work = !bio_list_empty(&tc->deferred_bio_list); spin_unlock_irqrestore(&tc->lock, flags); - wake_worker(pool); + if (has_work) + wake_worker(pool); } static void thin_defer_bio(struct thin_c *tc, struct bio *bio); |