blk-mq: Fix wrong wakeup batch configuration which will cause hang
Commit 180dccb0dba4f ("blk-mq: fix tag_get wait task can't be
awakened") will recalculate wake_batch when incrementing or decrementing
active_queues to avoid wake_batch > hctx_max_depth. At the same time, in
order to not affect performance as much as possible, the minimum wakeup
batch is set to 4. But when the QD is small (such as QD=1), if inc or dec
active_queues increases wakeup batch, that can lead to a hang:
Fix this problem with the following strategies:
QD : >= 32 | < 32
---------------------------------
wakeup batch: 8~4 | 3~1
Fixes: 180dccb0dba4f ("blk-mq: fix tag_get wait task can't be awakened")
Link: https://lore.kernel.org/linux-block/[email protected]/T/#t
Reported-by: Alex Xu (Hello71) <[email protected]>
Signed-off-by: Laibin Qiu <[email protected]>
Tested-by: Alex Xu (Hello71) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 6220fa6..09d293c 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -488,9 +488,13 @@ void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
unsigned int users)
{
unsigned int wake_batch;
+ unsigned int min_batch;
+ unsigned int depth = (sbq->sb.depth + users - 1) / users;
- wake_batch = clamp_val((sbq->sb.depth + users - 1) /
- users, 4, SBQ_WAKE_BATCH);
+ min_batch = sbq->sb.depth >= (4 * SBQ_WAIT_QUEUES) ? 4 : 1;
+
+ wake_batch = clamp_val(depth / SBQ_WAIT_QUEUES,
+ min_batch, SBQ_WAKE_BATCH);
__sbitmap_queue_update_wake_batch(sbq, wake_batch);
}
EXPORT_SYMBOL_GPL(sbitmap_queue_recalculate_wake_batch);
