On Wed, Aug 17, 2022 at 10:30:39PM -0400, Chris Murphy wrote:

On Wed, Aug 17, 2022, at 9:03 PM, Ming Lei wrote:

quoted

On Wed, Aug 17, 2022 at 12:34:42PM -0400, Chris Murphy wrote:

quoted

On Wed, Aug 17, 2022, at 11:34 AM, Ming Lei wrote:

quoted

From the 2nd log of blockdebugfs-all.txt, still not see any in-flight IO on
request based block devices, but sda is _not_ included in this log, and
only sdi, sdg and sdf are collected, is that expected?

While the problem was happening I did

cd /sys/kernel/debug/block
find . -type f -exec grep -aH . {} \;

The file has the nodes out of order, but I don't know enough about the interface to see if there are things that are missing, or what it means.

quoted

BTW, all request based block devices should be observed in blk-mq debugfs.

/sys/kernel/debug/block contains

drwxr-xr-x.  2 root root 0 Aug 17 15:20 md0
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sda
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdb
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdc
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdd
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sde
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdf
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdg
drwxr-xr-x. 51 root root 0 Aug 17 15:20 sdh
drwxr-xr-x.  4 root root 0 Aug 17 15:20 sdi
drwxr-xr-x.  2 root root 0 Aug 17 15:20 zram0

OK, so lots of devices are missed in your log, and the following command
is supposed to work for collecting log from all block device's debugfs:

(cd /sys/kernel/debug/block/ && find . -type f -exec grep -aH . {} \;)

OK here it is:

https://drive.google.com/file/d/18nEOx2Ghsqx8uII6nzWpCFuYENHuQd-f/view?usp=sharing

The above log shows that the io stall happens on sdd, where:

1) 616 requests pending from scheduler queue

grep "busy=" blockdebugfs-all2.txt | grep sdd | grep sched | awk -F "=" '{s+=$2} END {print s}'
616

2) 11 requests pending from ./sdd/hctx2/dispatch for more than 300 seconds

Recently we seldom observe io hang from dispatch list, except for the
following two:

https://lore.kernel.org/linux-block/20220803023355.3687360-1-yuyufen@huaweicloud.com/ (local)
https://lore.kernel.org/linux-block/20220726122224.1790882-1-yukuai1@huaweicloud.com/ (local)

BTW, what is the output of the following log?

	(cd /sys/block/sdd/device && find . -type f -exec grep -aH . {} \;)

Also the above log shows that host_tagset_enable support is still
crippled on v5.12, I guess the issue may not be triggered(or pretty hard)
after you update to d97e594c5166 ("blk-mq: Use request queue-wide tags for
tagset-wide sbitmap"), or v5.14.



thanks,
Ming