[winswitch] xpra session to other account on localhost

Antoine Martin antoine at nagafix.co.uk
Tue Dec 11 04:25:55 GMT 2018

On 08/12/2018 11:39, Marc Haber via shifter-users wrote:
> Hi,
> I would like to do an xpra connection to an xpra server running under a
> different account on the same host. I am running Debian unstable and
> have xpra 2.4.2. The box is a strong Six-Core machine with plenty of
> free RAM and a fast SSD.
> Running a Firefox browser over this connection is quite slow. I have to
> wait multiple hundreds of milliseconds before the reaction to a click
> can be seen. Scrolling a window takes like ten seconds until the picture
> is completely re-drawn at full resolution. Is that the expected behavior
> on a local host with no network involved, plenty of CPU and plenty of
> RAM?
No. It should be almost indistinguishable from native for all but the
most extreme use cases.

The most important thing for local connections is to enable mmap. (see
mmap command line options and use "-d mmap" to enable debug logging)

> I notice that the server complains twice on startup:
> 2018-12-08 20:19:08,741 cannot use uinput for virtual devices:
> 2018-12-08 20:19:08,741  [Errno 13] Failed to open the uinput device: Permission denied
Harmless and completely safe to ignore.
> WARNING: no 'numpy' module, HyBi protocol will be slower
This one is bogus.

Both have been added to the FAQ:

> python-numpy 1.15.4-2 is installed, and the /dev/uinput device is
> root:root 600, so it is not accessible by a regular user. Should I make
> /dev/uinput root:uinput 660 and put myself into the uinput group? Or is
> that a security disk? What is the recommended way to handle uinput? I
> don't even know what that is...
Don't bother with it. It is only really useful for simulating special
input devices. (and I have found some bugs in this code just today)

> Here is what the server logs:
> marc at fan:~$ xpra start --daemon=no --speaker=off --webcam=no --mdns=no --pulseaudio=no --start=konsole :100
> 2018-12-08 20:20:27,121 cannot use uinput for virtual devices:
> 2018-12-08 20:20:27,121  [Errno 13] Failed to open the uinput device: Permission denied
(..)> 2018-12-08 20:23:57,360 DPI set to 51 x 48 (wanted 54 x 77)
> 2018-12-08 20:23:57,361  you may experience scaling problems, such as huge or small fonts, etc
> 2018-12-08 20:23:57,361  to fix this issue, try the dpi switch, or use a patched Xorg dummy driver
That's odd. Make sure to use the patched dummy driver from the repository.

> 2018-12-08 20:23:57,417 client @09.176 Attached to localhost:22 via ssh
> 2018-12-08 20:23:57,417 client @09.177  (press Control-C to detach)
> 2018-12-08 20:23:57,510 client @09.284 server does not support xi input devices
> 2018-12-08 20:23:57,513 client @09.284  server uses: xtest
> 2018-12-08 20:23:57,706 New unix-domain connection received on /run/user/1002/xpra/fan-100
> 2018-12-08 20:23:57,708 New unix-domain connection received on /run/xpra/fan-100
> 2018-12-08 20:24:06,527 Warning: limited clipboard support for CLIPBOARD
> 2018-12-08 20:24:06,528  virtual method Gtk.Widget.selection_get not implemented
(..)> In the panel applet, I have set Picture => Fixed speed to "Lowest
> latency". The session information claims that I have 60 ms frame total
> latency, but it feels like a multiple of that. Any networked RDP session
> to a Windows machine feels much faster.
Even remote connections should be as fast as RDP, let alone local ones.

> This is not fun at all. What am I doing wrong?
Enable mmap and you should be fine.
Feel free to create a ticket to fix the non-mmap case.


> Greetings
> Marc

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