| Message ID | 20220127100047.1763746-1-qiulaibin@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next] blk-mq: Fix wrong wakeup batch configuration which will cause hang | expand |
Excerpts from Laibin Qiu's message of January 27, 2022 5:00 am: > Commit 180dccb0dba4f ("blk-mq: fix tag_get wait task can't be > awakened") will recalculating wake_batch when inc or dec active_queues > to avoid wake_batch is > 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 will increase wakeup batch, which will lead to 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/78cafe94-a787-e006-8851-69906f0c2128@huawei.com/T/#t > Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> > Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> > --- > lib/sbitmap.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/lib/sbitmap.c b/lib/sbitmap.c > index 6220fa67fb7e..09d293c30fd2 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); > -- > 2.22.0 > > Tested-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
On Thu, 27 Jan 2022 18:00:47 +0800, Laibin Qiu wrote: > Commit 180dccb0dba4f ("blk-mq: fix tag_get wait task can't be > awakened") will recalculating wake_batch when inc or dec active_queues > to avoid wake_batch is > 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 will increase wakeup batch, which will lead to hang. > > [...] Applied, thanks! [1/1] blk-mq: Fix wrong wakeup batch configuration which will cause hang commit: 10825410b956dc1ed8c5fbc8bbedaffdadde7f20 Best regards,
diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 6220fa67fb7e..09d293c30fd2 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);
Commit 180dccb0dba4f ("blk-mq: fix tag_get wait task can't be awakened") will recalculating wake_batch when inc or dec active_queues to avoid wake_batch is > 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 will increase wakeup batch, which will lead to 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/78cafe94-a787-e006-8851-69906f0c2128@huawei.com/T/#t Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> --- lib/sbitmap.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)