On Thu, Aug 3, 2017 at 5:17 PM, Ming Lei <tom.leiming@xxxxxxxxx> wrote: > Hi Mel Gorman, > > On Thu, Aug 3, 2017 at 4:51 PM, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: >> Hi Christoph, >> >> I know the reasons for switching to MQ by default but just be aware that it's >> not without hazards albeit it the biggest issues I've seen are switching >> CFQ to BFQ. On my home grid, there is some experimental automatic testing >> running every few weeks searching for regressions. Yesterday, it noticed >> that creating some work files for a postgres simulator called pgioperf >> was 38.33% slower and it auto-bisected to the switch to MQ. This is just >> linearly writing two files for testing on another benchmark and is not >> remarkable. The relevant part of the report is > > We saw some SCSI-MQ performance issue too, please see if the following > patchset fixes your issue: > > http://marc.info/?l=linux-block&m=150151989915776&w=2 BTW, the above patches(V1) can be found in the following tree: https://github.com/ming1/linux/commits/blk-mq-dispatch_for_scsi.V1 V2 has already been done but not posted out yet, because the performance test on SRP isn't completed: https://github.com/ming1/linux/commits/blk-mq-dispatch_for_scsi.V2 Thanks, Ming Lei