Re: [PATCH] block: fix race in update_io_ticks causing inflated disk statistics

[Jialin Wang]

On Sat, Feb 28, 2026 at 06:01:44PM +0800, Jialin Wang wrote:
> When multiple threads issue I/O requests concurrently after a period of
> disk idle time, iostat can report abnormal %util spikes (100%+) even
> when the actual I/O load is extremely light.
> 
> This issue can be reproduced using fio. By binding 8 fio threads to
> different CPUs, and having them issue 4KB I/Os every 1 second:
> 
>   fio --name=test --ioengine=sync --rw=randwrite --direct=1 --bs=4k \
>     --numjobs=8 --cpus_allowed=0-7 --cpus_allowed_policy=split \
>     --thinktime=1s --time_based --runtime=60 --group_reporting \
>     --filename=/mnt/sdb/test
> 
> The iostat -d sda 1 output will show a false 100%+ %util randomly:

Sorry, I made a typo. It should be 'iostat -d sdb -x 1'.

[...]

-- 
Regards,
Jialin