[Spice-devel] troubleshooting performance and latency issues?

Tue May 2 14:33:19 UTC 2017

On 02/05/17 16:07, Frediano Ziglio wrote:
>>
>>
>>
>> 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?
>>
> 
> They are in /var/log/libvirt/qemu (at least on my machines).
> Should not be big to require a grep, unless you enable additional
> logs.
> 

Thanks, here is what I found:

grep latency /var/log/libvirt/qemu/${VM}.log | cut -f3 -d:
 latency 6.442000 ms, bitrate 15242858 bps (14.536722 Mbps)
 latency 4.716000 ms, bitrate 18609384 bps (17.747292 Mbps)
 latency 7.116000 ms, bitrate 15983891 bps (15.243426 Mbps)
 latency 12.324000 ms, bitrate 15829951 bps (15.096618 Mbps)
 latency 7.526000 ms, bitrate 19341556 bps (18.445545 Mbps)
 latency 3.726000 ms, bitrate 16404604 bps (15.644650 Mbps)
 latency 6.999000 ms, bitrate 20247558 bps (19.309576 Mbps)
 latency 9.373000 ms, bitrate 22070154 bps (21.047739 Mbps)
 latency 3.819000 ms, bitrate 19262965 bps (18.370595 Mbps)
 latency 5.808000 ms, bitrate 16567434 bps (15.799936 Mbps)
 latency 53.710000 ms, bitrate 4911212 bps (4.683697 Mbps) LOW BANDWIDTH
 latency 100.954000 ms, bitrate 821117 bps (0.783078 Mbps) LOW BANDWIDTH
 latency 41.180000 ms, bitrate 593653 bps (0.566152 Mbps) LOW BANDWIDTH
 latency 6.116000 ms, bitrate 15928322 bps (15.190432 Mbps)
 latency 7.282000 ms, bitrate 13945728 bps (13.299683 Mbps)
 latency 8.717000 ms, bitrate 6145905 bps (5.861192 Mbps) LOW BANDWIDTH
 latency 6.423000 ms, bitrate 14845097 bps (14.157388 Mbps)
 latency 2.085000 ms, bitrate 5363208 bps (5.114754 Mbps) LOW BANDWIDTH
 latency 5.981000 ms, bitrate 3645399 bps (3.476523 Mbps) LOW BANDWIDTH
 latency 13.411000 ms, bitrate 17843917 bps (17.017285 Mbps)
 latency 6.944000 ms, bitrate 11591709 bps (11.054715 Mbps)
 latency 8.826000 ms, bitrate 16924500 bps (16.140461 Mbps)
 latency 13.359000 ms, bitrate 18063947 bps (17.227122 Mbps)
 latency 1.068000 ms, bitrate 20059355 bps (19.130092 Mbps)
 latency 5.237000 ms, bitrate 6574913 bps (6.270326 Mbps) LOW BANDWIDTH
 latency 1.022000 ms, bitrate 6562924 bps (6.258892 Mbps) LOW BANDWIDTH
 latency 1.916000 ms, bitrate 19701969 bps (18.789262 Mbps)
 latency 1.029000 ms, bitrate 17367559 bps (16.562995 Mbps)

>>
>>>> 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?
>>
> 
> weird, looks like is not compressing at all!
> With remote-viewer you can add options like --spice-preferred-compression=glz
> (see "remote-viewer --help-spice" command), you should be able to connect
> with "remote-viewer spice://<ip>:<port>" (not using ssh).
> 

OK, using remote-viewer and not using SSH it now appears a lot faster
rendering the unlock screen and the desktop.

This runs over a WAN connection so most ports, including SPICE, are
firewalled by default, I only tested it briefly with that port open.  Is
it considered safe to allow access to that port?

I would normally consider running something like that over IPsec so that
only trusted hosts can connect, should that have less overhead than
running it over SSH or is there another way to go about it?

Regards,

Daniel