Dear Yu,
Thank you for your patch. Some minor nits from my side, you can also ignore.
Am 18.06.23 um 16:25 schrieb Yu Kuai:
From: Yu Kuai <yukuai3@xxxxxxxxxx>
Commit 0c0be98bbe67 ("md/raid10: prevent unnecessary calls to wake_up()
in fast path") missed one place, for example, while testing with:
… one place. For example, with
fio -direct=1 -rw=write/randwrite -iodepth=1 ...
Then plug and unplug will be called for each io, then wake_up() from
Maybe:
fio -direct=1 -rw=write/randwrite -iodepth=1 ...
plug und unplug are called for each io, then …
raid10_unplug() will cause lock contention as well.
Maybe paste the perf command and output?
Avoid this contention by using wake_up_barrier() instead of wake_up(),
where spin_lock is not held while waitqueue is empty.
It’d be great if you added also the test results to the commit message.
By the way, in this scenario, each blk_plug_cb() will be allocated and
freed for each io, this seems need to be optimized as well.
Reported-and-tested-by: Ali Gholami Rudi <aligrudi@xxxxxxxxx>
Link: https://lore.kernel.org/all/20231606122233@laper.mirepesht/
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/md/raid10.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index d0de8c9fb3cf..fbaaa5e05edc 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1118,7 +1118,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
spin_lock_irq(&conf->device_lock);
bio_list_merge(&conf->pending_bio_list, &plug->pending);
spin_unlock_irq(&conf->device_lock);
- wake_up(&conf->wait_barrier);
+ wake_up_barrier(conf);
md_wakeup_thread(mddev->thread);
kfree(plug);
return;
@@ -1127,7 +1127,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
/* we aren't scheduling, so we can do the write-out directly. */
bio = bio_list_get(&plug->pending);
raid1_prepare_flush_writes(mddev->bitmap);
- wake_up(&conf->wait_barrier);
+ wake_up_barrier(conf);
while (bio) { /* submit pending writes */
struct bio *next = bio->bi_next;
Reviewed-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
Kind regards,
Paul
