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** <!-- Steps to reproduce the behavior: 1. Connect to VNC Server 2. Check CPU usage for app in Activity Monitor **Expected Behavior** Lower CPU usage **For the Desktop Version (please complete the following information):** - OS and version: MacOS Tahoe

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: <img width="337" height="107" alt="Image" src="https://github.com/user-attachments/assets/1d09ec29-82f1-416b-ac1a-9d9a371ba896" /> And compared to a server without the issue (osx 10.3, vine 2.2): <img width="347" height="101" alt="Image" src="https://github.com/user-attachments/assets/071e8f58-5cb4-4444-8d55-49c255cb6eb5" />

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...)