RCU-ified dm-mpath for testing/review

[Hannes Reinecke]

On 02/11/2016 04:34 PM, Mike Snitzer wrote:
> 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.
> 
> Initial review has uncovered some locking problems with the current code
> (nothing that caused crashes or hangs in my testing but...) so please
> hold off on testing until you hear from me (hopefully tomorrow).
> 
Good news is that I've managed to hit the roof for my array with the
devel2 version of those patches. (And a _heavily_ patched-up lpfc
driver :-)
So from that perspective everything's fine now; we've reached the
hardware limit for my setup.
Which in itself is quite impressive; beating Intel P3700 with 16FC
is not bad methinks :-)

So thanks for all your work here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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