This patch implements AioContext wide IO submission as batch, and
the idea behind is very simple:
- linux native aio(io_submit) supports to enqueue read/write requests
to different files
- in one AioContext, I/O requests from VM can be submitted to different
backend in host, one typical example is multi-lun scsi
This patch changes 'struct qemu_laio_state' as per AioContext, and
multiple 'bs' can be associted with one single instance of
'struct qemu_laio_state', then AioContext wide IO submission as batch
becomes easy to implement.
One simple test in my laptop shows ~20% throughput improvement
on randread from VM(using AioContext wide IO batch vs. not using io batch)
with below config:
-drive
id=drive_scsi1-0-0-0,if=none,format=raw,cache=none,aio=native,file=/dev/nullb2 \
-drive
id=drive_scsi1-0-0-1,if=none,format=raw,cache=none,aio=native,file=/dev/nullb3 \
-device
virtio-scsi-pci,num_queues=4,id=scsi1,addr=07,iothread=iothread0 \
-device
scsi-disk,bus=scsi1.0,channel=0,scsi-id=1,lun=0,drive=drive_scsi1-0-0-0,id=scsi1-0-0-0
\
-device
scsi-disk,bus=scsi1.0,channel=0,scsi-id=1,lun=1,drive=drive_scsi1-0-0-1,id=scsi1-0-0-1
\
BTW, maybe more boost can be obtained since ~33K/sec write() system call
can be observed when this test case is running, and it might be a recent
regression(BH?).
This patchset can be found on below tree too:
git://kernel.ubuntu.com/ming/qemu.git aio-io-batch.2
and these patches depend on "linux-aio: fix batch submission" patches
in below link:
http://marc.info/?l=qemu-devel&m=141528663106557&w=2
Any comments and suggestions are welcome.
async.c | 1 +
block.c | 16 +++
block/linux-aio.c | 251 ++++++++++++++++++++++++++++++---------
block/raw-aio.h | 6 +-
block/raw-posix.c | 4 +-
hw/scsi/virtio-scsi-dataplane.c | 8 ++
hw/scsi/virtio-scsi.c | 2 -
include/block/aio.h | 27 +++++
include/block/block.h | 3 +
9 files changed, 259 insertions(+), 59 deletions(-)
Thanks,
Ming Lei
