[Spice-devel] troubleshooting performance and latency issues?

[Frediano Ziglio]

> 
> 
> 
> 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) ?

> 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?

> 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