[Spice-devel] troubleshooting performance and latency issues?

[Daniel Pocock]

On 02/05/17 15:22, Frediano Ziglio wrote:
>>
>>
>>
>> Hi,
>>
>> I've observed some latency issues, for example, changing focus from one
>> terminal to another is a bit sluggish.  Typing isn't too bad.
>> Interaction with the sliding GNOME unlock screen and drawing the desktop
>> after unlock is painfully slow.
>>
> 
> Looks like your problems are due to a low bandwidth instead of high
> latency. Does spice detect a low bandwidth (should be written in the logs) ?
> 

Can you suggest which log file to check, or journalctl and a possible
grep command?


>> The virtual server I connect to runs Debian jessie and GNOME 3 desktop,
>> it is a default install:
>> Xorg = 2:1.16.4-1
>> xserver-xorg-video-qxl = 0.1.1-2+b1
>> spice-vdagent = 0.15.0-1.2
>>
>> I'm monitoring the latency of the connection to the KVM/libvirt/SPICE
>> server with Smokeping, average ping time is about 0.8ms, no packet loss.
>>
> 
> With such network latency you should not have much network latency
> issues, unless ssh (which seems you are using add a lot of it) add this
> issue.
> 
>>
>> I've setup the KVM/libvirt/SPICE host like this:
>> Debian stretch
>> Kernel = 4.9.13
>> libspice-server1 = 0.12.8-2.1
>> libvirt0 = 3.0.0-3
>>
>>
>> I've tried using both virt-manager and virt-viewer as clients on a
>> Debian jessie system, connecting over SSH to the KVM host, these are the
>> client versions:
>>
>> virt-manager = 1:1.0.1-5
>> virt-viewer = 1.0-1
>>
> 
> Can you try without SSH?
> 

OK, I tried this:

  virsh edit <domain>   and changed the listen IP to 0.0.0.0

Then I used spicy to connect directly to the port as I wasn't sure how
to tell virt-manager or virt-viewer to connect directly to the SPICE port.

I found some things are a bit faster but it is still not ideal

In particular, rendering the gray background of the GNOME unlock screen
appears very slow, it renders one line at a time from top to bottom, it
takes several seconds.  Rendering the desktop background image (default
Debian theme) was also slow.  I understand that I could change the
background image, but the gray lock screen, being a single colour,
shouldn't that render more quickly?

Unfortunately, before I could test it more, Xorg crashed again, I've
submitted the core dump now.

>> I noticed it appears a little better with virt-manager than virt-viewer,
>> should there be any difference between these two products if they both
>> use the same protocol?
>>
> 
> Maybe is due to some compression settings difference. Not sure which
> compression algorithms are used by virt-manager/virt-viewer.
> 
>> Can I do anything to tweak the .ssh/config to make it better?  It
>> occurred to me that adding "IPQoS lowdelay" might be useful as it
>> defaults to "throughput" for non-interactive connections.  Maybe
>> virt-manager should add that on the ssh command line?
>>
> 
> display requires quite lot of bandwidth, if you set network to
> low delay but you use a lot of bandwidth you'll get worst performance.
> 
>> Is there any way to see SPICE latency statistics in the virt-manager GUI?
>>
>> Would any other SPICE viewer make a difference?
>>
>> Are there any changes I should make to the GNOME desktop configuration
>> to make it work better through SPICE?  I've heard people comment on
>> changing to fvwm.
>>
>> Can anybody make any other suggestions?
>>
>> Regards,
>>
>> Daniel
> 
> Frediano
>