Many dropped frames

So i did a lot of work to optimize my rendering, and it runs really fast, until it doesnt.

When i profile it looks like this:

From what i can tell, my code executes fast, but there are all these dropped frames. I’m on a mac.

if you scroll further down, does it show the green bar for GPU utilization?

Do you have any other tabs open with webGL stuff in them?

possibly related: https://forum.unity.com/threads/webgl-performance-issue-on-macos-on-chrome-and-safari.1501532/