From: Yu Kuai <yukuai3@xxxxxxxxxx>
Commit 0c0be98bbe67 ("md/raid10: prevent unnecessary calls to wake_up()
in fast path") missed one place, for example, with:
fio -direct=1 -rw=write/randwrite -iodepth=1 ...
Plug and unplug are called for each io, then wake_up() from raid10_unplug()
will cause lock contention as well.
Avoid this contention by using wake_up_barrier() instead of wake_up(),
where spin_lock is not held if waitqueue is empty.
Fio test script:
[global]
name=random reads and writes
ioengine=libaio
direct=1
readwrite=randrw
rwmixread=70
iodepth=64
buffered=0
filename=/dev/md0
size=1G
runtime=30
time_based
randrepeat=0
norandommap
refill_buffers
ramp_time=10
bs=4k
numjobs=400
group_reporting=1
[job1]
Test result with ramdisk raid10(By Ali):
Before this patch With this patch
READ IOPS=2033k IOPS=3642k
WRITE IOPS=871k IOPS=1561K
By the way, in this scenario, 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>
Closes: https://lore.kernel.org/all/20231606122233@laper.mirepesht/
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
Changes in v2:
- update commit message;
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;
--
2.39.2
