Re: Switching to MQ by default may generate some bug reports

[Ming Lei]

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

Thanks,
Ming