On 05/21/2016 01:40 AM, Stefan Hajnoczi wrote: > 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. > > I will post performance results once they are ready. > > Stefan Hajnoczi (9): > virtio-blk: use batch notify in non-dataplane case > virtio-blk: tell dataplane which vq to notify > virtio-blk: associate request with a virtqueue > virtio-blk: add VirtIOBlockConf->num_queues > virtio-blk: multiqueue batch notify > vmstate: add VMSTATE_VARRAY_UINT32_ALLOC > 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 | 68 +++++++------- > hw/block/dataplane/virtio-blk.h | 2 +- > hw/block/virtio-blk.c | 200 > ++++++++++++++++++++++++++++++++++++---- > include/hw/virtio/virtio-blk.h | 13 ++- > include/migration/vmstate.h | 10 ++ > 5 files changed, 241 insertions(+), 52 deletions(-) >
With 2.6 I see 2 host threads consuming a CPU when running fio in a single CPU guest with a null-blk device and iothread for that disk. (the vcpu thread and the iothread). With this patchset the main thread also consumes almost 80% of a CPU doing polling in main_loop_wait. I have not even changes the num-queues values. So in essence 3 vs 2 host cpus. Christian
