On 24/06/2020 09:13, Kashyap Desai wrote:
Hi Hannes,
Do you have any issue with splitting the undocumented changes into
another patch as so:
No, that's perfectly fine.
Kashyap, I've also attached an updated patch for the elevator_count patch;
if
you agree John can include it in the next version.
ok, but I need to check it myself.
Hannes - Patch looks good. Header does not include problem statement. How
about adding below in header ?
High CPU utilization on "native_queued_spin_lock_slowpath" due to lock
contention is possible in mq-deadline and bfq io scheduler when nr_hw_queues
is more than one.
It is because kblockd work queue can submit IO from all online CPUs (through
blk_mq_run_hw_queues) even though only one hctx has pending commands.
Elevator callback "has_work" for mq-deadline and bfq scheduler consider
pending work if there are any IOs on request queue and it does not account
hctx context.
I have not seen performance drop after this patch, but I will continue
further testing.
John - One more thing, I am working on megaraid_sas driver to provide both
host_tagset = 1 and 0 option through module parameter.
I was hoping that we wouldn't have this, and have host_tagset = 1
always. Or maybe host_tagset = 1 by default, and allow module param to
set = 0. Your choice, though.
Thanks,
John
