On Wed, Dec 17 2014 at 4:43pm -0500, Jens Axboe <axboe@xxxxxxxxx> wrote: > On 12/17/2014 02:42 PM, Keith Busch wrote: > > On Tue, 16 Dec 2014, Mike Snitzer wrote: > >> Here is v3 of the request-based DM blk-support patchset. I've also > >> published a git repo here: > >> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-for-3.20-blk-mq > >> > >> > >> I found quite a few issues with v2 for both blk-mq and old > >> request-based DM. I've still attributed the original patches from > >> Keith to him even though I fixed/rewrote significant portions. Keith, > >> I'm happy to leave attribution like this unless you'd prefer I change > >> it. > > > > Thanks a bunch, Mike! I'll need to merge your tree with Jens' for nvme > > blk-mq, and one patch for a nvme scsi translation fix, then I can test > > this out. I get my dual ported nvme controller back tomorrow, so should > > have results before the end of the week. > > All the juicy nvme bits are in Linus' tree now, so that should work! > > BTW, Mike, do you have any perf numbers? Just curious how far along this is. No, not yet. I'll be focusing on the old request-based (non-blk-mq) performance first though to make sure we haven't killed the common case -- which obviously isn't what you're interested in ;) The primary concerns for the old request-based path are: 1) does submission through a new dedicated (per rq-based DM device) kthread hurt? https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-for-3.20-blk-mq&id=aec254b435c9ee78103b90c229644be810274a33 2) does spliiting the request structure out from dm_rq_target_io structure hurt? https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-for-3.20-blk-mq&id=a46bee4179e804b19e581d1b745e467d0ba946c1 I'm suspecting these changes should be fine but we'll see. (Hannes, Christoph, Bart and/or Junichi: if you have some performant multipath setups I'd love for you to try this code to make sure they still perform well). As for blk-mq support... I don't have access to any NVMe hardware, etc. I only tested with virtio-blk (to a ramdisk, scsi-debug, device on the host) so I'm really going to need to lean on Keith and others to validate blk-mq performance. So if you know someone with relevant blk-mq hardware who might benefit from blk-mq multipathing please point them at this code and have them report back! -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
