RCU-ified dm-mpath for testing/review
Mike Snitzer
snitzer at redhat.com
Wed Feb 10 19:35:41 PST 2016
On Wed, Feb 10 2016 at 8:50pm -0500,
Mike Snitzer <snitzer at redhat.com> wrote:
> On Tue, Feb 09 2016 at 7:45pm -0500,
> Mike Snitzer <snitzer at redhat.com> wrote:
>
> >
> > OK, I took a crack at embracing RCU. Only slightly better performance
> > on my single NUMA node testbed. (But I'll have to track down a system
> > with multiple NUMA nodes to do any justice to the next wave of this
> > optimization effort)
> >
> > This RCU work is very heavy-handed and way too fiddley (there could
> > easily be bugs). Anyway, please see:
> > http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/commit/?h=devel2&id=d80a7e4f8b5be9c81e4d452137623b003fa64745
> >
> > But this might give you something to build on to arrive at something
> > more scalable?
>
> I've a bit more polished version of this work (broken up into multiple
> commits, with some fixes, etc) here:
> http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=devel3
>
> Hannes and/or Sagi, if you get a chance to try this on your NUMA system
> please let me know how it goes.
FYI, with these changes my single NUMA node testbed's read IOPs went
from:
~1310K to ~1410K w/ nr_hw_queues dm-mq=4 and null_blk=4
~1330K to ~1415K w/ nr_hw_queues dm-mq=4 and null_blk=12
~1365K to ~1425K w/ nr_hw_queues dm-mq=12 and null_blk=12
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