On 02/09/2016 03:55 PM, Mike Snitzer wrote: > On Tue, Feb 09 2016 at 2:50am -0500, > Hannes Reinecke <hare@xxxxxxx> wrote: > >> On 02/07/2016 06:20 PM, Mike Snitzer wrote: >>> On Sun, Feb 07 2016 at 11:54am -0500, >>> Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx> wrote: >>> >>>> >>>>>> If so, can you check with e.g. >>>>>> perf record -ags -e LLC-load-misses sleep 10 && perf report whether this >>>>>> workload triggers perhaps lock contention ? What you need to look for in >>>>>> the perf output is whether any functions occupy more than 10% CPU time. >>>>> >>>>> I will, thanks for the tip! >>>> >>>> The perf report is very similar to the one that started this effort.. >>>> >>>> I'm afraid we'll need to resolve the per-target m->lock in order >>>> to scale with NUMA... >>> >>> Could be. Just for testing, you can try the 2 topmost commits I've put >>> here (once applied both __multipath_map and multipath_busy won't have >>> _any_ locking.. again, very much test-only): >>> >>> http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=devel2 >>> >> So, I gave those patches a spin. >> Sad to say, they do _not_ resolve the issue fully. >> >> My testbed (2 paths per LUN, 40 CPUs, 4 cores) yields 505k IOPs with >> those patches. > > That isn't a surprise. We knew the m->lock spinlock contention to be a > problem. And NUMA makes it even worse. > >> Using a single path (without those patches, but still running >> multipath on top of that path) the same testbed yields 550k IOPs. >> Which very much smells like a lock contention ... >> We do get a slight improvement, though; without those patches I >> could only get about 350k IOPs. But still, I would somehow expect 2 >> paths to be faster than just one .. > > https://www.redhat.com/archives/dm-devel/2016-February/msg00036.html > > hint hint... > I hoped they wouldn't be needed with your patches. Plus perf revealed that I first need to address a spinlock contention in the lpfc driver before that even would make sense. So more debugging to follow. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
