On Thu, Aug 03, 2017 at 05:57:50PM +0800, Ming Lei wrote: > On Thu, Aug 3, 2017 at 5:42 PM, Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Aug 03, 2017 at 05:17:21PM +0800, Ming Lei 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 > >> > > > > That series is dealing with problems with legacy-deadline vs mq-none where > > as the bulk of the problems reported in this mail are related to > > legacy-CFQ vs mq-BFQ. > > The serials deals with none and all mq schedulers, and you can see > the improvement on mq-deadline in cover letter, :-) > Would it be expected to fix a 2x to 4x slowdown as experienced by BFQ that was not observed on other schedulers? -- Mel Gorman SUSE Labs
