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[Discussion] vnc performance degradation

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kent_dorfman766
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[Discussion] vnc performance degradation

#1 Post by kent_dorfman766 »

Apparently I'm not the only one to notice it, based on my web search. There is a noticable slowdown of vnc client response in debian 11 compared to debian 10.

Using vnc connection right now and almost unusable keyboard lag. Also seeing sporatic

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error in the server log

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Re: [Discussion] vnc performance degradation

#2 Post by lindi »

Debian has many VNC clients, which client are you using?

Are you using Wayland or Xorg on the client machine?

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Re: [Discussion] vnc performance degradation

#3 Post by kent_dorfman766 »

always traditional X11, not a fan of wayland...plus not supported by my preferred window managers.

server side is x11vnc as

Code: Select all

# ----------------------------------------------------------------------
runvnc() {
    /usr/bin/x11vnc -display $1 -repeat -noxrecord -nopw \
    -listen 10.1.11.102 -rfbport ${2} -scale 0.96 -solid ${3} -capslock \
    -forever -noxdamage > ${HOME}/.vnc/vnc${1}.log 2>&1 &
}

runvnc :0.0 5900 \#807040
runvnc :0.1 5901 \#407080
client is tigervnc. Tried a variety of different client side options for compression and lowering of color depth to no avail.
Networking is not an issue since I've got a better network than most companies provide and my connections are all hardwired.

This seems a version regression issue, as noted by others online who are experiencing slowdowns under similar conditions.

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Re: [Discussion] vnc performance degradation

#4 Post by jmechnich »

This post put me on the right track:
patch "0003-rfb-increase-update-buf-size.patch: Allow larger screen sizes" in libvncserver either breaks x11vnc or its usage with certain clients.
Personally, I have been using ssvncviewer on macOS and Debian 10.

The patch was already in Bookworm since libvncserver-0.9.13+dfsg-4 and has more recently been backported into Bullseye's version 0.9.13+dfsg-2+deb11u1.
Removing the patch and recompiling the libvncserver package, as well as x11vnc fixed the issue for me.

I am going to try reporting the issue with the x11vnc people hoping that it can be fixed there.

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Re: [Discussion] vnc performance degradation

#5 Post by kent_dorfman766 »

@jmechnich
Cool! Nice to see that someone understands what I was getting at. I'm not in a spot where I want to manually build the vnc clients or viewer but will keep an eye on this.

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Re: [Discussion] vnc performance degradation

#6 Post by jmechnich »

I have opened an issue with x11vnc on GitHub: https://github.com/LibVNC/x11vnc/issues/220

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Re: [Discussion] vnc performance degradation

#7 Post by jmechnich »

Quick update: apparently this is not caused by upstream as it can be fixed by locally rebuilding the package.
I have closed the issue on GitHub and submitted a bug to the Debian x11vnc maintainers.

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Re: [Discussion] vnc performance degradation

#8 Post by jmechnich »

This has been fixed with x11vnc 0.9.16-9 and should be backported to bullseye (see Bug #1027043)
Last edited by jmechnich on 2023-02-07 18:09, edited 1 time in total.

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