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

[Stefan Hajnoczi]

On Thu, May 20, 2021 at 03:13:02PM +0100, Stefan Hajnoczi wrote:
> 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(-)

Christoph and Jens: Any more thoughts on this irq toggling approach?

Stefan

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