[Spice-devel] Dreadful performance under Windows 10 Enterprise 2016 LTSB

[Frediano Ziglio]

> So, I guess I'm stuck waiting for iGVT-g to go upstream then :-(.

I think would be quite a pity. The fact that our environments are mostly KVM 
should not avoid trying to fix Xen environment. 

First: can you do a video and share somehow? 

One of the difference between KVM and Xen is the schedule. While KVM uses Linux 
Xen rely on Linux + its own. One reason could be this difference. 
Could you same an strace of Qemu while from dom0 while the VM is doing some 
screen updates? A command line this for some seconds could help: 
strace -ff -o trace.txt -tt -T -p <PID> 
(where PID is the pid of your Qemu related to the VM running, you should be root). 
You could compress and the the trace file. 

One thing I noted using Windows is the refresh of the active button (like usually the OK 
on message boxes). It seems that the refresh is quite slow. A bit of background. The actual 
DOD driver is not that accelerated. One of the few base accelerations (the others require 
DirectX support) are Alpha draws. If not implemented Windows will have to read back 
from screen which from some experiment I made (enabling some debugging on the host) 
seems quite slow. I don't know if it's related to the way these commands are sent by the 
Windows driver or the latency of handling them or some other issues (maybe some 
required serialization) but the problem seems to not affect Linux at all. 

Frediano 

> On 19 January 2017 at 15:20, Christophe Fergeau < cfergeau at redhat.com >
> wrote:

> > On Tue, Jan 10, 2017 at 10:06:33AM +0200, George Diamantopoulos wrote:
> 
> > > Hello all,
> 
> > >
> 
> > > I'm trying out qxl-dod in a new installation, and performance is so low
> 
> > > that the guest is practically unusable. Redrawing takes about 4-5
> > > seconds.
> 
> > > I have used qxl-dod in the past on the same hardware with much better
> 
> > > results, although the software stack is different this time. I tried
> 
> > > disabling all visual effects, but apart from the expected gains (fewer
> 
> > > frames to redraw after each action due to the animations' being disabled)
> 
> > > it didn't improve usability much.
> 
> > >
> 
> > > As I have no idea how to provide useful debugging information on this,
> > > I'll
> 
> > > try to outline my configuration here for now. Please let me know if
> > > there's
> 
> > > anything I can do to provide more meaningful information:
> 
> > >
> 
> > > Host: Gentoo linux, kernel 4.9.1
> 
> > > Hypervizor: Xen 4.8.0
> 

> > Oh you are using Xen, you might be the first one testing qxl-wddm-dod on
> 
> > Xen :(( This might explain the guest gets so slow with the driver (ie
> 
> > bug only showing up when using Xen).
> 

> > Christophe
> 

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