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(-)
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