On 09/11/2014 08:42, Ming Lei wrote:
> 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?).
Ming,
these patches are interesting. I would like to compare them with the
opposite approach (and, I think, more similar to your old work) where
the qemu_laio_state API is moved entirely into AioContext, with lazy
allocation (reference-counted too, probably).
Most of the patches would be the same, but you would replace
aio_attach_aio_bs/aio_detach_aio_bs with something like
aio_native_get/aio_native_unref. Ultimately block/{linux,win32}-aio.c
could be merged into block/aio-{posix,win32}.c, but you do not have to
do that now.
Could you try that? This way we can see which API turns out to be nicer.
Thanks,
Paolo
> 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
>
