On Mon, Jun 20, 2016 at 01:42:14PM +0200, Paolo Bonzini wrote: > > > On 20/06/2016 12:36, Stefan Hajnoczi wrote: > > On Tue, Jun 07, 2016 at 05:28:24PM +0100, Stefan Hajnoczi wrote: > >> v3: > >> * Drop Patch 1 to batch guest notify for non-dataplane > >> > >> The Linux AIO completion BH and the virtio-blk batch notify BH changed > >> order > >> in the AioContext->first_bh list as a side-effect of moving the BH from > >> hw/block/dataplane/virtio-blk.c to hw/block/virtio-blk.c. This caused a > >> serious performance regression for both dataplane and non-dataplane. > >> > >> I've decided not to move the BH in this series and work on a separate > >> solution for making batch notify generic. > >> > >> The remaining patches have been reordered and cleaned up. > >> > >> * See performance data below. > >> > >> v2: > >> * Simplify s->rq live migration [Paolo] > >> * Use more efficient bitmap ops for batch notification [Paolo] > >> * Fix perf regression due to batch notify BH in wrong AioContext > >> [Christian] > >> > >> The virtio_blk guest driver has supported multiple virtqueues since Linux > >> 3.17. > >> This patch series adds multiple virtqueues to QEMU's virtio-blk emulated > >> device. > >> > >> Ming Lei sent patches previously but these were not merged. This series > >> implements virtio-blk multiqueue for QEMU from scratch since the codebase > >> has > >> changed. Live migration support for s->rq was also missing from the > >> previous > >> series and has been added. > >> > >> It's important to note that QEMU's block layer does not support multiqueue > >> yet. > >> Therefore virtio-blk device processes all virtqueues in the same AioContext > >> (IOThread). Further work is necessary to take advantage of multiqueue > >> support > >> in QEMU's block layer once it becomes available. > >> > >> Performance results: > >> > >> Using virtio-blk-pci,num-queues=4 can produce a speed-up but -smp 4 > >> introduces a lot of variance across runs. No pinning was performed. > >> > >> Results show that there is no regression anymore, thanks to dropping the > >> batch notify BH patch. > >> > >> RHEL 7.2 guest on RHEL 7.2 host with 1 vcpu and 1 GB RAM unless otherwise > >> noted. The default configuration of the Linux null_blk driver is used as > >> /dev/vdb. > >> > >> $ cat files/fio.job > >> [global] > >> filename=/dev/vdb > >> ioengine=libaio > >> direct=1 > >> runtime=60 > >> ramp_time=5 > >> gtod_reduce=1 > >> > >> [job1] > >> numjobs=4 > >> iodepth=16 > >> rw=randread > >> bs=4K > >> > >> $ ./analyze.py runs/ > >> Name IOPS Error > >> unpatched-d6550e9ed2 19269820.2 ± 1.36% > >> unpatched-dataplane-d6550e9ed2 22351400.4 ± 1.07% > >> v3-dataplane 22318511.2 ± 0.77% > >> v3-no-dataplane 18936103.8 ± 1.12% > >> v3-queues-4-no-dataplane 19177021.8 ± 1.45% > >> v3-smp-4-no-dataplane 25509585.2 ± 29.50% > >> v3-smp-4-no-dataplane-no-mq 12466177.2 ± 7.88% > >> > >> Configuration: > >> Name Patched? Dataplane? SMP? MQ? > >> unpatched-d6550e9ed2 N N N N > >> unpatched-dataplane-d6550e9ed2 N Y N N > >> v3-dataplane Y Y N N > >> v3-no-dataplane Y N N N > >> v3-queues-4-no-dataplane Y N N Y > >> v3-smp-4-no-dataplane Y N Y Y > >> v3-smp-4-no-dataplane-no-mq Y N Y N > >> > >> SMP means -smp 4. > >> MQ means virtio-blk-pci,num-queues=4. > >> > >> Stefan Hajnoczi (7): > >> virtio-blk: add VirtIOBlockConf->num_queues > >> virtio-blk: multiqueue batch notify > >> virtio-blk: tell dataplane which vq to notify > >> virtio-blk: associate request with a virtqueue > >> virtio-blk: live migrate s->rq with multiqueue > >> virtio-blk: dataplane multiqueue support > >> virtio-blk: add num-queues device property > >> > >> hw/block/dataplane/virtio-blk.c | 81 > >> +++++++++++++++++++++++++++++------------ > >> hw/block/dataplane/virtio-blk.h | 2 +- > >> hw/block/virtio-blk.c | 52 +++++++++++++++++++++----- > >> include/hw/virtio/virtio-blk.h | 6 ++- > >> 4 files changed, 105 insertions(+), 36 deletions(-) > > > > Ping? > > > > Looks good to me, but I'll never understand who's supposed to apply > virtio-blk patches. :)
I'll rebase this series and include it for QEMU 2.7. Stefan
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