[PATCH 0/3] virtio_blk: blk-mq io_poll support

[Stefan Hajnoczi <stefanha@redhat.com>]

This patch series implements blk_mq_ops->poll() so REQ_HIPRI requests can be
polled. IOPS for 4k and 16k block sizes increases by 5-18% on a virtio-blk
device with 4 virtqueues backed by an NVMe drive.

- Benchmark: fio ioengine=pvsync2 numjobs=4 direct=1
- Guest: 4 vCPUs with one virtio-blk device (4 virtqueues)
- Disk: Intel Corporation NVMe Datacenter SSD [Optane] [8086:2701]
- CPU: Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz

rw          bs hipri=0 hipri=1
------------------------------
randread    4k 149,426 170,763 +14%
randread   16k 118,939 134,269 +12%
randread   64k  34,886  34,906   0%
randread  128k  17,655  17,667   0%
randwrite   4k 138,578 163,600 +18%
randwrite  16k 102,089 120,950 +18%
randwrite  64k  32,364  32,561   0%
randwrite 128k  16,154  16,237   0%
read        4k 146,032 170,620 +16%
read       16k 117,097 130,437 +11%
read       64k  34,834  35,037   0%
read      128k  17,680  17,658   0%
write       4k 134,562 151,422 +12%
write      16k 101,796 107,606  +5%
write      64k  32,364  32,594   0%
write     128k  16,259  16,265   0%

Larger block sizes do not benefit from polling as much but the
improvement is worthwhile for smaller block sizes.

Stefan Hajnoczi (3):
  virtio: add virtioqueue_more_used()
  virtio_blk: avoid repeating vblk->vqs[qid]
  virtio_blk: implement blk_mq_ops->poll()

 include/linux/virtio.h       |   2 +
 drivers/block/virtio_blk.c   | 126 +++++++++++++++++++++++++++++------
 drivers/virtio/virtio_ring.c |  17 +++++
 3 files changed, 123 insertions(+), 22 deletions(-)

-- 
2.31.1