Re: [PATCH 5/6] scsi: core: don't limit per-LUN queue depth for SSD when HBA needs

Martin K. Petersen
2020-01-28T04:23:37Z

Sumanesh,

> Instead of relying on QUEUE_FULL and some complex heuristics of when
> to start tracking device_busy, why can't we simply use "
> track_queue_depth" ( along with the other flag that Ming added) to
> decide which devices need queue depth tracking, and track device_busy
> only for them?

Because I am interested in addressing the device_busy contention problem
for all of our non-legacy drivers. I.e. not just for controllers that
happen to queue internally.

> I am not sure how we can suddenly start tracking device_busy on the fly,
> if we do not know how many IO are already pending for that device?

We know that from the tags. It's just not hot path material.

--
Martin K. Petersen Oracle Linux Engineering