On Sat, Aug 18, 2018 at 1:32 AM Ricardo Ribalda Delgado
[off-list ref] wrote:

Hello

Coming from: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=906328

bmaptools is kind of a "smart dd" tool, that lets you write images
very fast and securely. Since the last Debian Kernel update it has
become 5-8 times slower.

After some debugging, we have figured out that the reason for that
slowness is the Multi-Queue Block IO Queueing Mechanism.

Debian maintainer has pointed out that in the near future the single
queue will be deprecated.

My question is if we can get a similar perfomance for bmaptools with
blk-mq and how?

It suppose to be not worse than non-blk-mq, and maybe there is bug
somewhere.

Could you use 'iostat -dx $DISK_PATH 1' to collect io stat when running
bmaptools in both blk-mq and non-blk-mq?

BTW, don't change the default io scheduler as none, which shouldn't
work well for slow disk, such as non-SSD.

Thanks,
Ming Lei