[Spice-devel] [SOLVED again] video performance in rhel/centos 7 vs fedora 20

[David Mansfield]

On 08/06/2014 01:47 PM, David Mansfield wrote:
>
> On 07/16/2014 05:39 PM, David Mansfield wrote:
>>
>> On 07/15/2014 11:22 AM, Marc-André Lureau wrote:
>>> Hi
>>>
>>> ----- Original Message -----
>>>> Hi All,
>>>>
>>>> We have been piloting deployments of VM using Fedora 20 host and guest
>>>> and have been very happy with performance and stability in almost 
>>>> every
>>>> respect, so a big thanks to all for this hard work. Things are looking
>>>> great.
>>>>
>>>> Now we have been testing deployments of these same VMs (F20 guests) on
>>>> rhel 7 (centos 7). We migrated one over and one of the issues seems to
>>>> be a severe degradation of video performance vis-a-vis the F20 host.
>>> The difference between rhel7 and f20 host is quite surprising. I get
>>> quite bad performance with f20 host as well (spice 0.12.4-3, qemu 
>>> 2.0.0-5)
>>>
>>> Are your host configured with the same spice settings (in particular
>>> streaming-video and other compression settings) ?
>> I have not specified any specific settings on the host for spice. If 
>> there are differences in the defaults then I could play around with 
>> that. Do you know what the differences might be?
>>
>> In particular on the F20 side I have:
>> spice-server-0.12.5-2.fc20.x86_64
>> qemu-kvm-1.6.2-6.fc20.x86_64
>>
>> And everything is peachy.
>>
>> On c7 host I have:
>> spice-server-0.12.4-5.el7.x86_64
>> qemu-kvm-1.5.3-60.el7_0_0.2.x86_64
>>
>>
>>>> The setup is a C7 host, F20 guest and either C7 or F20 client, either
>>>> local to the host or on the LAN.
>>>>
>>>> In this setup, the video plays fine for a few seconds, but eventually
>>>> degrades to about 1fps with severe tearing of the video. Video does
>>>> remain in sync with audio and there are no audio breakups.
>>>>
>>>> Any pointers on things to try?
>>> I have been investigating some video rendering issues with rhel7 guest
>>> on rhel7 host, seehttps://bugzilla.redhat.com/show_bug.cgi?id=1030024
>>>
>>> However, even with the cogl fix and "PutImage BIG-REQUEST", the video
>>> regions seems to vary too much for the Spice video filter to perform
>>> well (using firefox/html5 video youtube). I believe it will need to be
>>> improved.
>> I think these are both guest side fixes/changes, and my guest is F20, 
>> (actually the exact same VM as was running before on F20 host, but 
>> now on C7 host).
>>
>> So I think the cogl fix is not relevant (and I'm not permitted to see 
>> the PutImage BIG-REQUEST issue because it's a restricted bug).
>>
>> I have tried rebuilding the spice-server package from F20 and 
>> installing on C7 host, but it doesn't change anything.
>>
>> Which leaves me with qemu changes.  Is there a "version" of the qxl 
>> hardware that's implemented in qemu that may be different?
>>
>>
>>> Your help would be most welcome to investigate and improve this 
>>> further.
>> I'll do my best :-) .  Sometimes it's just a maze of twisty little 
>> passages, all alike...
>>
> As a follow up to this, I finally got qemu 1.6.2 (SRPM from F20) 
> rebuilt on Centos 7. "Quite an ordeal" is an understatement BTW, but I 
> did get it built finally along with a bunch of pre-req.
>
> Summary: video issues are fixed.
>
> So something different between qemu 1.5.3 (from RHEL which includes 
> 100s of patches) and qemu 1.6.2 (from Fedora which includes 100s of 
> patches) has fixed the problem.  spice-server was *not* touched.
>
> If there's any way to narrow this down, I'll try it, but I have no 
> idea how to compare these two SW versions effectively.
>
> On a side note, how/why is Fedora/RH carrying all of these downstream 
> fixes for QEMU? It's staggering. Are the upstream maintainers highly 
> unresponsive?
>
Finally a follow up to my follow up and a really "SOLVED". It turns out 
that the solution to this issue was much more simple than expected.  The 
addition of:

       <streaming mode='off'/>

solves it, and that's now the default in Fedora qemu (it carries a patch 
to set the default to off), so when the fedora package was recompiled to 
Centos 7, this was probably the only part relevant to video performance.

The above configuration change was tested on a "vanilla" qemu on centos 
7 with very satisfactory video performance.

-- 
Thanks,
David Mansfield
Cobite, INC.