On Mon, 07/20 16:54, Stefan Hajnoczi wrote:
> The raw-posix block driver implements Linux AIO batching so multiple
> requests can be submitted with a single io_submit(2) system call.
> Batching is currently only used by virtio-scsi and
> virtio-blk-data-plane.
>
> Enable batching for regular virtio-blk so the number of io_submit(2)
> system calls is reduced for workloads with queue depth > 1.
>
> In 4KB random read performance tests with queue depth 32, the CPU
> utilization on the host is reduced by 9.4%. The fio job is as follows:
>
> [global]
> bs=4k
> ioengine=libaio
> iodepth=32
> direct=1
> sync=0
> time_based=1
> runtime=30
> clocksource=gettimeofday
> ramp_time=5
>
> [job1]
> rw=randread
> filename=/dev/vdb
> size=4096M
> write_bw_log=fio
> write_iops_log=fio
> write_lat_log=fio
> log_avg_msec=1000
>
> This benchmark was run on an raw image on LVM. The disk was an SSD
> drive and -drive cache=none,aio=native was used.
>
> Tested-by: Pradeep Surisetty <psuri...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> hw/block/virtio-blk.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 6aefda4..a2137c8 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -600,6 +600,8 @@ static void virtio_blk_handle_output(VirtIODevice *vdev,
> VirtQueue *vq)
> return;
> }
>
> + blk_io_plug(s->blk);
> +
> while ((req = virtio_blk_get_request(s))) {
> virtio_blk_handle_request(req, &mrb);
> }
> @@ -607,6 +609,8 @@ static void virtio_blk_handle_output(VirtIODevice *vdev,
> VirtQueue *vq)
> if (mrb.num_reqs) {
> virtio_blk_submit_multireq(s->blk, &mrb);
> }
> +
> + blk_io_unplug(s->blk);
> }
>
> static void virtio_blk_dma_restart_bh(void *opaque)
> --
> 2.4.3
>
>
Reviewed-by: Fam Zheng <f...@redhat.com>
