Re: [PATCH 0/7] hisi_sas: Misc bugfixes and an optimisation patch

[John Garry]

On 11/10/2018 07:36, Christoph Hellwig wrote:
> On Wed, Oct 10, 2018 at 09:58:25PM -0400, Martin K. Petersen wrote:
> > > This is because the IPTT index must be a unique value per HBA. However,
> > > if we switched to SCSI MQ, the block layer tag becomes unique per queue,
> > > and not per HBA.
> >
> > That doesn't sound right.

Hmmm, well this is what I was told ...

> blk-mq tags are always per-host (which has actually caused problems for
> ATA, which is now using its own per-device tags).

So, for example, if Scsi_host.can_queue = 2048 and 
Scsi_host.nr_hw_queues = 16, then rq tags are still in range [0, 2048) 
for that HBA, i.e. invariant on queue count?

> .

Thanks,
John