v4: * Rebased onto qemu.git/master * Included latest performance results 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. 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 v4-smp-4-dataplane 13326598.0 ± 6.31% v4-smp-4-dataplane-no-mq 11483568.0 ± 3.42% v4-smp-4-no-dataplane 18108611.6 ± 1.53% v4-smp-4-no-dataplane-no-mq 13951225.6 ± 7.81% 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(-) -- 2.5.5
