On 05/01/2021 11:18, Ming Lei wrote:
ot set normally..
It always return true, and might just take a bit more CPU especially the tag queue
depth of magsas_raid and hisi_sas_v3 is quite high.
Hi Ming,
Right, but we actually tested by hacking the host tag queue depth to be
lower such that we should have tag contention, here is an extract from the
original series cover letter for my results:
Tag depth 4000 (default) 260**
Baseline (v5.9-rc1):
none sched: 2094K IOPS 513K
mq-deadline sched: 2145K IOPS 1336K
Final, host_tagset=0 in LLDD *, ***:
none sched: 2120K IOPS 550K
mq-deadline sched: 2121K IOPS 1309K
Final ***:
none sched: 2132K IOPS 1185
mq-deadline sched: 2145K IOPS 2097
Maybe my test did not expose the issue. Kashyap also tested this and
reported the original issue such that we needed this feature, so I'm
confused.
Hi Ming,
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/
Thanks,
John
