Re: [RFC PATCH 0/4] dm mpath: vastly improve blk-mq IO performance

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Apr 01 2016 at  4:12am -0400,
Johannes Thumshirn <jthumshirn@suse.de> wrote:

> On 2016-03-31 22:04, Mike Snitzer wrote:
> >I developed these changes some weeks ago but have since focused on
> >regression and performance testing on larger NUMA systems.
> >
> >For regression testing I've been using mptest:
> >https://github.com/snitm/mptest
> >
> >For performance testing I've been using a null_blk device (with
> >various configuration permutations, e.g. pinning memory to a
> >particular NUMA node, and varied number of submit_queues).
> >
> >By eliminating multipath's heavy use of the m->lock spinlock in the
> >fast IO paths serious performance improvements are realized.
> 
> Hi Mike,
> 
> Are this the patches you pointed Hannes to?
> 
> If yes, please add my Tested-by: Johannes Thumshirn <jthumshirn@suse.de>

No they are not.

Hannes seems to have last pulled in my DM mpath changes that (ab)used RCU.
I ended up dropping those changes and this patchset is the replacement.

So please retest with this patchset (I know you guys have a large setup
that these changes are very relevant for).  If you could actually share
_how_ yo've tested that'd help me understand how these changes are
holding up.  So far all looks good for me...

Mike