I was curious so I took a look at firefox's profiler. It looks like it does a hybrid render, using a couple of canvas elements for the flame graph and the stack

I was curious so I took a look at firefox's profiler. It looks like it does a hybrid render, using a couple of canvas elements for the flame graph and the stack trace (up the top), but the rest of the UI is rendered using plain old DOM elements. It performs great, despite the whole thing being pure javascript. Example: https://share.firefox.dev/40QUthv https://share.firefox.dev/40QUthv . (Though this trace is probably smaller than the profiling traces you're demoing.)