Re: [Qemu-devel] Lock contention in QEMU

[Weiwei Jia]

Hi Stefan,

I still have another concern like following.

Has x-data-plane been used (or accepted) widely in systems. I have
this concern since if it hasn't been widely accepted, it may
have/cause some problems we don't know. Do you know some hidden
problems which may caused by QEMU x-data-plane feature in systems?

Thanks,
Weiwei Jia

On Fri, Dec 16, 2016 at 9:32 AM, Weiwei Jia <address@hidden> wrote:
> On Fri, Dec 16, 2016 at 4:48 AM, Stefan Hajnoczi <address@hidden> wrote:
>> On Thu, Dec 15, 2016 at 11:04:23AM -0500, Weiwei Jia wrote:
>>> On Thu, Dec 15, 2016 at 3:06 AM, Stefan Hajnoczi <address@hidden> wrote:
>>> > On Thu, Dec 15, 2016 at 12:17:09AM -0500, Weiwei Jia wrote:
>>> >> BTW, do we have an example to show users how to config following
>>> >> virtio-blk dataplane commands into XML configuration file?
>>> >>
>>> >> qemu -object iothread,id=iothread0 \
>>> >>       -drive if=none,id=drive0,file=test.img,format=raw,cache=none \
>>> >>       -device virtio-blk-pci,iothread=iothread0,drive=drive0
>>> >
>>> > https://libvirt.org/formatdomain.html#elementsIOThreadsAllocation
>>> >
>>> > See also <cputune><iothreadpin> and <driver iothread=>.
>>>
>>> It seems that the libvirt XML configuration in above link [1] is
>>> different from the configuration which you said in your blog [2]. Your
>>> blog just said how to use x-data-plane for virtio-blk but libvirt XML
>>> configuration doesn't say anything about x-data-plane. Does it in
>>> default support by latest QEMU version. If I want to test virtio-blk
>>> or virtio-scsi data-plane to make timeslice more stable, what version
>>> of QEMU/KVM should I use? Would you please give me some suggestions?
>>> Thank you.
>>>
>>> [1] https://libvirt.org/formatdomain.html#elementsIOThreadsAllocation
>>> [2] 
>>> http://blog.vmsplice.net/2013/03/new-in-qemu-14-high-performance-virtio.html
>>
>> I will update the blog post (from 2013) with the modern libvirt XML
>> syntax.
>>
>> Please use the
>> https://libvirt.org/formatdomain.html#elementsIOThreadsAllocation
>> documentation (unless you are using a really old QEMU and libvirt!).
>
> I have tried the old libvirt XML way in your blog with QEMU v2.2.0 and
> Libvirt v1.2.2. It seems that everything works well for me. I will try
> the modern libvirt XML syntax with latest QEMU and libvirt.
>
> Thank you,
> Weiwei Jia