Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Ming Lei
On Thu, Oct 12, 2017 at 09:37:11AM -0600, Jens Axboe wrote: > On 10/12/2017 09:33 AM, Bart Van Assche wrote: > > On Thu, 2017-10-12 at 18:01 +0800, Ming Lei wrote: > >> Even EWMA approach isn't good on SCSI-MQ too, because > >> some SCSI's .cmd_per_lun is very small, such as 3 on > >> lpfc and qla2

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Jens Axboe
On 10/12/2017 09:33 AM, Bart Van Assche wrote: > On Thu, 2017-10-12 at 18:01 +0800, Ming Lei wrote: >> Even EWMA approach isn't good on SCSI-MQ too, because >> some SCSI's .cmd_per_lun is very small, such as 3 on >> lpfc and qla2xxx, and one full flush will trigger >> BLK_STS_RESOURCE easily. >> >>

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Bart Van Assche
On Thu, 2017-10-12 at 18:01 +0800, Ming Lei wrote: > Even EWMA approach isn't good on SCSI-MQ too, because > some SCSI's .cmd_per_lun is very small, such as 3 on > lpfc and qla2xxx, and one full flush will trigger > BLK_STS_RESOURCE easily. > > So I suggest to use the way of q->queue_depth first,

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Jens Axboe
On 10/12/2017 09:22 AM, Ming Lei wrote: > On Thu, Oct 12, 2017 at 08:52:12AM -0600, Jens Axboe wrote: >> On 10/12/2017 04:01 AM, Ming Lei wrote: >>> On Tue, Oct 10, 2017 at 11:23:45AM -0700, Omar Sandoval wrote: On Mon, Oct 09, 2017 at 07:24:23PM +0800, Ming Lei wrote: > SCSI devices use h

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Ming Lei
On Thu, Oct 12, 2017 at 08:52:12AM -0600, Jens Axboe wrote: > On 10/12/2017 04:01 AM, Ming Lei wrote: > > On Tue, Oct 10, 2017 at 11:23:45AM -0700, Omar Sandoval wrote: > >> On Mon, Oct 09, 2017 at 07:24:23PM +0800, Ming Lei wrote: > >>> SCSI devices use host-wide tagset, and the shared driver tag

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Jens Axboe
On 10/12/2017 04:01 AM, Ming Lei wrote: > On Tue, Oct 10, 2017 at 11:23:45AM -0700, Omar Sandoval wrote: >> On Mon, Oct 09, 2017 at 07:24:23PM +0800, Ming Lei wrote: >>> SCSI devices use host-wide tagset, and the shared driver tag space is >>> often quite big. Meantime there is also queue depth for

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-12 Thread Ming Lei
On Tue, Oct 10, 2017 at 11:23:45AM -0700, Omar Sandoval wrote: > On Mon, Oct 09, 2017 at 07:24:23PM +0800, Ming Lei wrote: > > SCSI devices use host-wide tagset, and the shared driver tag space is > > often quite big. Meantime there is also queue depth for each lun( > > .cmd_per_lun), which is ofte

Re: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue

2017-10-10 Thread Omar Sandoval
On Mon, Oct 09, 2017 at 07:24:23PM +0800, Ming Lei wrote: > SCSI devices use host-wide tagset, and the shared driver tag space is > often quite big. Meantime there is also queue depth for each lun( > .cmd_per_lun), which is often small, for example, on both lpfc and > qla2xxx, .cmd_per_lun is just