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

2018-10-15 Thread Martin K. Petersen
John, > As I mentioned in the thread that spawned from this, we actually can't > expose multiple hw queues at the moment. And, if we did, we find a > performance drop due to having to go back to manage this IPTT > internally. > > So how to handle? We're going to continue to work towards exposing

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

2018-10-11 Thread John Garry
On 11/10/2018 14:32, Ming Lei wrote: On Thu, Oct 11, 2018 at 02:12:11PM +0100, John Garry wrote: On 11/10/2018 11:15, Christoph Hellwig wrote: On Thu, Oct 11, 2018 at 10:59:11AM +0100, John Garry wrote: blk-mq tags are always per-host (which has actually caused problems for ATA, which is now

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

2018-10-11 Thread Ming Lei
On Thu, Oct 11, 2018 at 02:12:11PM +0100, John Garry wrote: > On 11/10/2018 11:15, Christoph Hellwig wrote: > > On Thu, Oct 11, 2018 at 10:59:11AM +0100, John Garry wrote: > > > > > > > blk-mq tags are always per-host (which has actually caused problems for > > > > ATA, which is now using its own

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

2018-10-11 Thread John Garry
On 11/10/2018 11:15, Christoph Hellwig wrote: On Thu, Oct 11, 2018 at 10:59:11AM +0100, John Garry wrote: 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

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

2018-10-11 Thread Christoph Hellwig
On Thu, Oct 11, 2018 at 10:59:11AM +0100, John Garry wrote: > > > 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 a

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

2018-10-11 Thread 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

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

2018-10-10 Thread Christoph Hellwig
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. blk-mq tags are always pe

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

2018-10-10 Thread Martin K. Petersen
John, > However it does block us in future from enabling SCSI MQ in the driver. We're going to remove the legacy I/O path so I'm not particularly keen on merging something that's going in the opposite direction. > This is because the IPTT index must be a unique value per HBA. However, > if we