Stuttering at 60fps

A performance troubleshooting question:

I have a scene with some hap movies, a small amount of texture instancing, and a few particles. It’s playing back smoothly at 60fps with frame rendering time of 16ms. Over a few minutes, the rendering time drifts downwards until it hits 9-10ms - where everything starts stuttering for a few minutes (it always stays 60fps, though) , and it settles around 6-9ms 60fps.

If at any point, I click the mouse ( so clicking on perform window)- render time jumps up to 16ms again, stuttering stops. Though the cycle as described above starts anew.

Any ideas why this might be happening, or some troubleshooting steps to try?
(2) P5000 w/ sync card, 5 portrait monitors at 5400x1920 resolution 1650 xeon, windows 10. Tried vsync on/off/adaptive, one window spanning monitors, always on top.

Thanks.

Is there any chance the Window didn’t have focus before you clicked on it? On Windows 10 the perform window needs to have focus for the driver to take more control of how the contents are displayed to the desktop (you’ll often see the desktop flicker when this happens). Without that we are going through Aero which can cause frame drops.

The solution ended up setting the framerate to 120fps. Not sure why, but it works.

First attachment is with timeline at 120fps.

Second is with timeline at 60fps.
Around 10ms is where I get a lot of stuttering, click mouse at around the 14000 mark, msec jumps to 16ms and smooth rendering, until ms drops around 10ms. At the end of the graph, I clicked the mouse again.

Are the monitors running at 120hz?

No, they’re set to 60hz.