Now that actual overlaps are not handled on the wait_for_overlap wq
anymore, the remaining cases when we wait on this wq are limited to
reshape. If reshape is not in progress, don't add to the wq in
raid5_make_request() because add_wait_queue() / remove_wait_queue()
operations take a spinlock and cause noticeable contention when multiple
threads are submitting requests to the mddev.
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
---
drivers/md/raid5.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 1e7dcb6235c7..8e74c455a87d 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6071,6 +6071,7 @@ static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
+ bool on_wq;
struct r5conf *conf = mddev->private;
sector_t logical_sector;
struct stripe_request_ctx ctx = {};
@@ -6144,11 +6145,15 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
* sequential IO pattern. We don't bother with the optimization when
* reshaping as the performance benefit is not worth the complexity.
*/
- if (likely(conf->reshape_progress == MaxSector))
+ if (likely(conf->reshape_progress == MaxSector)) {
logical_sector = raid5_bio_lowest_chunk_sector(conf, bi);
+ on_wq = false;
+ } else {
+ add_wait_queue(&conf->wait_for_overlap, &wait);
+ on_wq = true;
+ }
s = (logical_sector - ctx.first_sector) >> RAID5_STRIPE_SHIFT(conf);
- add_wait_queue(&conf->wait_for_overlap, &wait);
while (1) {
res = make_stripe_request(mddev, conf, &ctx, logical_sector,
bi);
@@ -6159,6 +6164,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
continue;
if (res == STRIPE_SCHEDULE_AND_RETRY) {
+ WARN_ON_ONCE(!on_wq);
/*
* Must release the reference to batch_last before
* scheduling and waiting for work to be done,
@@ -6183,7 +6189,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
logical_sector = ctx.first_sector +
(s << RAID5_STRIPE_SHIFT(conf));
}
- remove_wait_queue(&conf->wait_for_overlap, &wait);
+ if (unlikely(on_wq))
+ remove_wait_queue(&conf->wait_for_overlap, &wait);
if (ctx.batch_last)
raid5_release_stripe(ctx.batch_last);
--
2.43.0
