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

[Stefan Hajnoczi]

On Wed, Nov 21, 2012 at 03:00:25PM +0800, Asias He wrote:
> On 11/21/2012 02:44 PM, Stefan Hajnoczi wrote:
> > On Wed, Nov 21, 2012 at 7:42 AM, Asias He <address@hidden> wrote:
> >> On 11/21/2012 01:39 PM, Asias He wrote:
> >>> On 11/20/2012 08:25 PM, Stefan Hajnoczi wrote:
> >>>> 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
> >>>
> >>> Ok, thanks. /me trying
> >>
> >> Hi Stefan,
> >>
> >> If I enable the merge in guest the IOPS for seq read/write goes up to
> >> ~400K/300K. If I disable the merge in guest the IOPS drops to ~17K/24K
> >> for seq read/write (which is similar to the result I posted yesterday,
> >> with merge disalbed). Could you please also share the numbers for rand
> >> read and write in your setup?
> > 
> > Thanks for running the test.  Please send your rand read/write fio
> > jobfile so I can run the exact same test.
> > 
> > BTW I was running the default F18 (host) and RHEL 6.3 (guest) I/O
> > schedulers in my test yesterday.
> 
> Sure, this is the script I used to run the test in guest.

Thanks, will give this a try!

Stefan