Small jitters with multiple display regions

General Discussion
1

I have a weird problem. I run an application with 3 monitors. The middle monitor runs on one rendering process which I start with:
start /MIN /NORMAL c:\Panda3D-1.10.4.1-x64\python\ppython.exe mainC.py
The left and right monitors run a separate process:
start /MIN /NORMAL c:\Panda3D-1.10.4.1-x64\python\ppython_left.exe mainLR.py
Left monitor uses the default DisplayRegion and the right monitor uses a different display region with a different camera.
The GPU is a Geforce GTX 2080 super and I have 32 Gb RAM.

In both processes the framerate is a stable 60 Hz. However, the images on the left monitor often stutter/jitter while the images on the left and right monitor are very fluently.
So, I tried pstats to see what causes this, but I could see nothing special during those jitter phases, that can last over a minute before the left channel becomes fluently also. In pstats most of the time was WAIT and number of geoms was well below 300 all the time. But the strange thing I noticed was that the jitter was completely gone if I run pstats during the rendering.

I have tried this several times but it is very consistent. While running pstats, images on all 3 channels (monitors) are fluent all the time while the left channel images are jittery regularly when pstats is off.

Could this be related to commands sent to the GPU by both processes which sometimes result in overload of the GPU, and that pstats accidentally results in better synchronization?

I know how strange this sounds, but it is consistent.

2

Try adding a 1ms sleep to a task in both applications; I’m wondering if one of them is using so much CPU that it’s starving the other process, or something like that, and that enabling PStats adds enough I/O to make it yield more time to the other process.

The process that drives the left and right monitors, does it use two separate windows or one window stretched across two monitors?

In both processes the framerate is a stable 60 Hz. However, the images on the left monitor often stutter/jitter while the images on the left and right monitor are very fluently.

To be clear, did you mean that the center one jitters, or the one on the left jitters?

3

I just tried adding a millisecond or a few to both processes but that does not change it. I also set the processor affinity for both processes to different processor cores but that does not help either.
The process that drives the left and right monitors, uses two separate windows. Only the one on the left jitters. Is there a way to control when the data is sent to the GPU? In that case I could send data to the GPU in one process and when this is done send the data from the other process, and communicate between processes via shared memory.

4

Also, total processor load is always below 80%.