On 06/01/2021 01:28, Ming Lei wrote:
How many LUNs are involved in above test with 260 depth?
For me, there was 12 SAS SSDs; for convenience here is the cover letter with
details:
https://lore.kernel.org/linux-block/1597850436-116171-1-git-send-email-john.garry@xxxxxxxxxx/
IIRC, for megaraid sas, Kashyap used many more LUNs for testing (64) and
high fio depth (128) but did not reduce .can_queue, topic originally raised
here:
https://lore.kernel.org/linux-block/29f8062c1fccace73c45252073232917@xxxxxxxxxxxxxx/
OK, in both tests, nr_luns are big enough wrt. 260 depth. Maybe that is
why very low IOPS is observed in 'Final(hosttag=1)' with 260 depth.
I'd suggest to run your previous test again after applying this patch,
and see if difference can be observed.
Hi Ming,
I tested and didn't see a noticeable difference with the fix when using
the reducing tag queue depth. I got ~500K IOPs with tag queue depth of
260, as opposed to 2M with full tag queue depth. However I was doubtful
on this test method before. Regardless, your change and this feature
still look proper.
@Kashyap, it would be great if you guys could test this also on that
same setup you described previously:
https://lore.kernel.org/linux-block/29f8062c1fccace73c45252073232917@xxxxxxxxxxxxxx/
Thanks,
John
