Re: [PATCH v6 2/2] virtio-blk: support mq_ops->queue_rqs()

Chaitanya Kulkarni
2022-04-07T20:29:03Z

On 4/6/22 08:32, Suwan Kim wrote:
> This patch supports mq_ops->queue_rqs() hook. It has an advantage of
> batch submission to virtio-blk driver. It also helps polling I/O because
> polling uses batched completion of block layer. Batch submission in
> queue_rqs() can boost polling performance.
>
> In queue_rqs(), it iterates plug->mq_list, collects requests that
> belong to same HW queue until it encounters a request from other
> HW queue or sees the end of the list.
> Then, virtio-blk adds requests into virtqueue and kicks virtqueue
> to submit requests.
>
> If there is an error, it inserts error request to requeue_list and
> passes it to ordinary block layer path.
>
> For verification, I did fio test.
> (io_uring, randread, direct=1, bs=4K, iodepth=64 numjobs=N)
> I set 4 vcpu and 2 virtio-blk queues for VM and run fio test 5 times.
> It shows about 2% improvement.
>
> | numjobs=2 | numjobs=4
> -----------------------------------------------------------
> fio without queue_rqs() | 291K IOPS | 238K IOPS
> -----------------------------------------------------------
> fio with queue_rqs() | 295K IOPS | 243K IOPS
>
> For polling I/O performance, I also did fio test as below.
> (io_uring, hipri, randread, direct=1, bs=512, iodepth=64 numjobs=4)
> I set 4 vcpu and 2 poll queues for VM.
> It shows about 2% improvement in polling I/O.
>
> | IOPS | avg latency
> -----------------------------------------------------------
> fio poll without queue_rqs() | 424K | 613.05 usec
> -----------------------------------------------------------
> fio poll with queue_rqs() | 435K | 601.01 usec
>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> ---

Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck