Re: [Qemu-devel] [PATCH 0/7] virtio: virtio-blk data plane

[Asias He <asias@redhat.com>]

On 11/20/2012 08:25 PM, Stefan Hajnoczi wrote:
> On Tue, Nov 20, 2012 at 1:21 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
>> On Tue, Nov 20, 2012 at 10:02 AM, Asias He <asias@redhat.com> wrote:
>>> Hello Stefan,
>>>
>>> On 11/15/2012 11:18 PM, Stefan Hajnoczi wrote:
>>>> This series adds the -device virtio-blk-pci,x-data-plane=on property that
>>>> enables a high performance I/O codepath.  A dedicated thread is used to process
>>>> virtio-blk requests outside the global mutex and without going through the QEMU
>>>> block layer.
>>>>
>>>> Khoa Huynh <khoa@us.ibm.com> reported an increase from 140,000 IOPS to 600,000
>>>> IOPS for a single VM using virtio-blk-data-plane in July:
>>>>
>>>>   http://comments.gmane.org/gmane.comp.emulators.kvm.devel/94580
>>>>
>>>> The virtio-blk-data-plane approach was originally presented at Linux Plumbers
>>>> Conference 2010.  The following slides contain a brief overview:
>>>>
>>>>   http://linuxplumbersconf.org/2010/ocw/system/presentations/651/original/Optimizing_the_QEMU_Storage_Stack.pdf
>>>>
>>>> The basic approach is:
>>>> 1. Each virtio-blk device has a thread dedicated to handling ioeventfd
>>>>    signalling when the guest kicks the virtqueue.
>>>> 2. Requests are processed without going through the QEMU block layer using
>>>>    Linux AIO directly.
>>>> 3. Completion interrupts are injected via irqfd from the dedicated thread.
>>>>
>>>> To try it out:
>>>>
>>>>   qemu -drive if=none,id=drive0,cache=none,aio=native,format=raw,file=...
>>>>        -device virtio-blk-pci,drive=drive0,scsi=off,x-data-plane=on
>>>
>>>
>>> Is this the latest dataplane bits:
>>> (git://github.com/stefanha/qemu.git virtio-blk-data-plane)
>>>
>>> commit 7872075c24fa01c925d4f41faa9d04ce69bf5328
>>> Author: Stefan Hajnoczi <stefanha@redhat.com>
>>> Date:   Wed Nov 14 15:45:38 2012 +0100
>>>
>>>     virtio-blk: add x-data-plane=on|off performance feature
>>>
>>>
>>> With this commit on a ramdisk based box, I am seeing about 10K IOPS with
>>> x-data-plane on and 90K IOPS with x-data-plane off.
>>>
>>> Any ideas?
>>>
>>> Command line I used:
>>>
>>> IMG=/dev/ram0
>>> x86_64-softmmu/qemu-system-x86_64 \
>>> -drive file=/root/img/sid.img,if=ide \
>>> -drive file=${IMG},if=none,cache=none,aio=native,id=disk1 -device
>>> virtio-blk-pci,x-data-plane=off,drive=disk1,scsi=off \
>>> -kernel $KERNEL -append "root=/dev/sdb1 console=tty0" \
>>> -L /tmp/qemu-dataplane/share/qemu/ -nographic -vnc :0 -enable-kvm -m
>>> 2048 -smp 4 -cpu qemu64,+x2apic -M pc
>>
>> Was just about to send out the latest patch series which addresses
>> review comments, so I have tested the latest code
>> (61b70fef489ce51ecd18d69afb9622c110b9315c).
> 
> Rebased onto qemu.git/master before sending out.  The commit ID is now:
> cf6ed6406543ecc43895012a9ac9665e3753d5e8
> 
> https://github.com/stefanha/qemu/commits/virtio-blk-data-plane
> 
> Stefan

Ok, thanks. /me trying

-- 
Asias