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

[Stefan Hajnoczi]

On Tue, Nov 20, 2012 at 1:21 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Tue, Nov 20, 2012 at 10:02 AM, Asias He <address@hidden> 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 <address@hidden> 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 <address@hidden>
>> 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