What can affect server performance (linux)

[Alex Holland]

Hi,

My first post so be gentle :)

I've been using TigerVNC for many years. Headless Linux x64 (RHEL8) server and Windows 10/11 viewer and I've been very happy and productive. At the time I was using TigerVNC 1.13

We just updated our workstations, so newer hardware, newer RHEL kernel, newer TigerVNC (1.15) and *for me* the performance of some applications has gone terrible. Something as simple as an an old editor (NEdit 5.7) the window refresh takes seconds when syntax highlighting and scrolling. The Xvnc CPU utilisation goes to 60% (of i9-14900K!) 

If I use x0vncserver there are no performance issues with nEdit everything is normal.

It's not every application, terminal for example the scrolling seems fine in VSCode.

I'm using X11 Gnome Classic as my Window Manager.

I am launching the server using "vncserver :1"

I'm fairly sure it will be a setting either in VNC or my linux installation but I've failed to find it.

I tried deleting my .config and my .vnc plus my .nedit directories in my home area and nothing seems to be fixing it.

Here is my server screen config :

    xrandr

    Screen 0: minimum 32 x 32, current 5120 x 1441, maximum 32768 x 32768
    VNC-0 connected primary 2560x1440+0+1 0mm x 0mm
       2560x1440     60.00*+

       [snip]
    VNC-1 connected 2560x1440+2560+0 0mm x 0mm
       2560x1440     60.00*+

This is definitely a user setting as other users in the office with identical HW, OS and TigerVNC versions are not seeing this.

If I connect to someone else's VNC session (same resolution) I do not have performance issues so this doesn't seem to be related to the viewer.

Any suggestions? 

Regards

AlexH

[Pierre Ossman]

On 04/06/2025 13:08, Alex Holland wrote:
> Hi,
>
> My first post so be gentle :)
>
> I've been using TigerVNC for many years. Headless Linux x64 (RHEL8) server
> and Windows 10/11 viewer and I've been very happy and productive. At the
> time I was using TigerVNC 1.13
>
> We just updated our workstations, so newer hardware, newer RHEL kernel,
> newer TigerVNC (1.15) and *for me* the performance of some applications has
> gone terrible. Something as simple as an an old editor (NEdit 5.7) the
> window refresh takes seconds when syntax highlighting and scrolling. The
> Xvnc CPU utilisation goes to 60% (of i9-14900K!)
>

My guess would be the new 3D acceleration in TigerVNC 1.15. GNOME tends
to provoke a lot of back and forth between the GPU and CPU that we
haven't optimized yet.

You can disable this by specifying -rendernode="" to Xvnc.

>
> This is definitely a user setting as other users in the office with
> identical HW, OS and TigerVNC versions are not seeing this.
>

That makes it less likely that it's the 3D stuff, though, as it should
be the same for everyone.

But before we get too far in the debugging, please try the rendernode
setting and see if that helps.

Regards,
--
Pierre Ossman Software Development
Cendio AB https://cendio.com
Teknikringen 8 https://twitter.com/ThinLinc
583 30 Linköping https://facebook.com/ThinLinc
Phone: +46-13-214600

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

[Alex Holland]

That fixes it. Thanks.

The gnome settings in my home area must have some option enabled that affects some applications like nEdit that other users have disabled. (but I couldn't find what it was)

Regards

Alex