Re: [PATCH V4 00/14] blk-mq-sched: improve SCSI-MQ performance

On Tue, Sep 19, 2017 at 12:25:15PM -0700, Omar Sandoval wrote:

On Sat, Sep 02, 2017 at 11:17:15PM +0800, Ming Lei wrote:

quoted

Hi,

In Red Hat internal storage test wrt. blk-mq scheduler, we
found that I/O performance is much bad with mq-deadline, especially
about sequential I/O on some multi-queue SCSI devcies(lpfc, qla2xxx,
SRP...)

Turns out one big issue causes the performance regression: requests
are still dequeued from sw queue/scheduler queue even when ldd's
queue is busy, so I/O merge becomes quite difficult to make, then
sequential IO degrades a lot.

The 1st five patches improve this situation, and brings back
some performance loss.

Sorry it took so long, I've reviewed or commented on patches 1-6. When
you send v5, could you just send patches 1-6, and split the rest as
their own series?

Sure, no problem.

Thanks for your review!

-- 
Ming