On Sat, Oct 14, 2017 at 09:39:21AM -0600, Jens Axboe wrote: > On 10/14/2017 03:22 AM, Ming Lei wrote: > > Hi Jens, > > > > 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 > > performance degrades a lot. > > > > This issue becomes one of mains reasons for reverting default SCSI_MQ > > in V4.13. > > > > This 8 patches improve this situation, and brings back performance loss. > > > > With this change, SCSI-MQ sequential I/O performance is improved much, Paolo > > reported that mq-deadline performance improved much[2] in his dbench test > > wrt V2. Also performance improvement on lpfc/qla2xx was observed with V1.[1] > > Looks good to me, and the kyber fix looks obviously correct to me. I have > applied this series for 4.15. Thanks Ming. That is great, thanks for making this patchset in! -- Ming
