High CPU Usage on MacOS Client

[robled]

If you'd like to put out an incentive for fixing this bug, you can do so at https://issuehunt.io/r/bk138/multivnc?tab=idle

Is your bug report about the Desktop Multivnc or the Mobile MultiVNC?

• Desktop MacOS

Which MultiVNC version are you using?
Version 0.11.0 (7)

Which server are you connecting to?

• VNC server vendor: TightVNC
• VNC server version: 1.3.10
• OS version: Windows 98, Windows NT 4.0
• OS language: English

Describe the bug
High CPU usage (~70%) after connecting to VNC server. My CPU is a M1 Max. CPU usage goes back to normal after disconnecting from server.

To Reproduce

[bk138]

@robled we need steps to reproduce - does this happen with other servers as well?

[robled]

Apologies, I filled out the form but must have fat fingered something and deleted the rest of it.

Steps to reproduce:

• Install MacOS client version 0.11.0 (7) from Mac App Store
• Install TightVNC server version 1.3.10 on Windows NT 4.0 or Windows 98
• Start the MacOS client, notice CPU usage is low/normal
• Connect to either VNC server listed above, CPU usage jumps to around 70% on M1 Max CPU
• Disconnect from VNC server and notice CPU usage goes back down again

As far as other servers go, I just tested it on vncserver 1.34-1 on HaikuOS (ported from RealVNC 4.0 apparently), and was able to reproduce.

Now what's interesting is that on Vine Server 2.2 on Mac OS 10.3 the CPU usage is much lower.

I admit that I'm using some pretty old software for retro computing adventures.

[bk138]

Thanks for your swift answer! I can give it a try with TightVNC 1.3.10 on Windows 10 and see if I can experience this as well.

[robled]

Noticed something interesting on the high CPU usage server (win98, tightvnc 1.3.10) with statistics:

And compared to a server without the issue (osx 10.3, vine 2.2):

[bk138]

@robled you can try disabling FastRequest in MultiVNC's settings.

[robled]

Disabling that has no effect on the Updates/second or CPU usage for the win98 scenario.

[bk138]

Sooo, I could test with TightVNC 1.3.10 and Tight 2.8.87 running on Windows 11, connecting with MultiVNC master from an Intel Mac (so not quite the same env, but well):

• TightVNC 1.3.10 : ~30 % CPU usage on the Mac (which is unsually high), but also the Windows screen was not properly updated by this TightVNC version on that host OS.
• TightVNC: 2.8.87: ~5% CPU usage on the Mac (normal I'd say), screen reading on the Windows 11 side worked here

I can try TightVNC 1.3.10 with another viewer at some point, but for now it seems the relatively old TightVNC version is it (sending lots of small rectangles maybe...)