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. 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 .. 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) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
