Thanks Stefan and Paolo for your response and advice!
Hi Paolo,
As to the virtio-scsi batch I/O submission feature in QEMU which you mentioned,
is this feature turned on by default in QEMU 2.9 or there is a tunable
parameters to turn on/off the feature?
Thanks,
Wei
On 4/26/19, 1:14 AM, "Paolo Bonzini" <pbonz...@redhat.com> wrote:
On 23/04/19 14:04, Stefan Hajnoczi wrote:
>>In addition, does Virtio-scsi support Batch I/O Submission feature
>>which may be able to increase the IOPS via reducing the number of
>>system calls?
>
>I don't see obvious batching support in drivers/scsi/virtio_scsi.c.
>The Linux block layer supports batching but I'm not sure if the SCSI
>layer does.
I think he's referring to QEMU, in which case yes, virtio-scsi does
batch I/O submission. See virtio_scsi_handle_cmd_req_prepare and
virtio_scsi_handle_cmd_req_submit in hw/scsi/virtio-scsi.c, they do
blk_io_plug and blk_io_unplug in order to batch I/O requests from QEMU
to the host kernel.
