[LSF/MM TOPIC] Two blk-mq related topics

[Mel Gorman]

On Tue, Jan 30, 2018 at 11:08:28AM +0100, Johannes Thumshirn wrote:
> [+Cc Mel]
> Jens Axboe <axboe at kernel.dk> writes:
> > On 1/29/18 1:56 PM, James Bottomley wrote:
> >> On Mon, 2018-01-29 at 23:46 +0800, Ming Lei wrote:
> >> [...]
> >>> 2. When to enable SCSI_MQ at default again?
> >> 
> >> I'm not sure there's much to discuss ... I think the basic answer is as
> >> soon as Christoph wants to try it again.
> >
> > FWIW, internally I've been running various IO intensive workloads on
> > what is essentially 4.12 upstream with scsi-mq the default (with
> > mq-deadline as the scheduler) and comparing IO workloads with a
> > previous 4.6 kernel (without scsi-mq), and things are looking
> > great.
> >
> > We're never going to iron out the last kinks with it being off
> > by default, I think we should attempt to flip the switch again
> > for 4.16.
> 
> The 4.12 sounds interesting. I remember Mel ran some test with 4.12 as
> we where considering to flip the config option for SLES and it showed
> several road blocks.
> 

Mostly due to slow storage and BFQ where mq-deadline was not a universal
win as an alternative default. I don't have current data and I archived
what I had, but it was based on 4.13-rc7 at the time and BFQ has changed
a lot since so it would need to be redone.

> I'm not sure whether he re-evaluated 4.13/4.14 on his grid though.
> 

No, it hasn't. Grid time for performance testing has been tight during
the last few months to say the least.

> But I'm definitively interested in this discussion and can even possibly
> share some benchmark results we did in our FC Lab.
> 

If you remind me, I may be able to re-execute the tests in a 4.16-rcX
before LSF/MM so you have other data to work with.  Unfortunately, I'll
not be able to make LSF/MM this time due to personal commitments that
conflict and are unmovable.

-- 
Mel Gorman
SUSE Labs