From 10825410b956dc1ed8c5fbc8bbedaffdadde7f20 Mon Sep 17 00:00:00 2001
From: Laibin Qiu <qiulaibin@huawei.com>
Date: Thu, 27 Jan 2022 18:00:47 +0800
Subject: [PATCH] blk-mq: Fix wrong wakeup batch configuration which will cause
hang
Git-commit: 10825410b956dc1ed8c5fbc8bbedaffdadde7f20
Patch-mainline: v5.17-rc2
References: bsc#1200263
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
Acked-by: Jan Kara <jack@suse.cz>
---------------------------------
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>
Tested-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Link: https://lore.kernel.org/r/20220127100047.1763746-1-qiulaibin@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
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);
--
2.35.3