On Sun, Feb 07 2016 at 10:41am -0500, Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx> wrote: > > >FYI, here is the latest revised patch: > >https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.6&id=a5b835282422ec41991c1dbdb88daa4af7d166d2 > > > >(revised patch header and fixed a thinko in the dm.c:rq_completed() > >change from the RFC patch I posted earlier) > > Hi Mike, > > So I gave your patches a go (dm-4.6) but I still don't see the > improvement you reported (while I do see a minor improvement). > > null_blk queue_mode=2 submit_queues=24 > dm_mod blk_mq_nr_hw_queues=24 blk_mq_queue_depth=4096 use_blk_mq=Y > > I see 620K IOPs on dm_mq vs. 1750K IOPs on raw nullb0. blk_mq_nr_hw_queues=24 isn't likely to help you (but with these patches, the first being the most important, it shouldn't hurt either provided you have 24 cpus). Could be you have multiple NUMA nodes and are seeing problems from that? I have 12 cpus (in the same physical cpu) and only a single NUMA node. I get the same results as blk_mq_nr_hw_queues=12 with blk_mq_nr_hw_queues=4 (same goes for null_blk submit_queues). I've seen my IOPs go from ~950K to ~1400K. The peak null_blk can get on my setup is ~1950K. So I'm still seeing a ~25% drop with dm-mq (but that is much better than the over 50% drop I saw seeing). > Is there something I'm missing? Not sure, I just emailed out all my patches (and cc'd you). Please verify you're using the latest here (same as 'dm-4.6' branch): https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=for-next I rebased a couple times... so please diff what you have tested against this latest 'dm-4.6' branch. -- 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
