I took a couple more profiles. They are both from the most recent nightly build (59.0a1).
- https://perfht.ml/2ni19Ic – 180MB Buffer Size
- https://perfht.ml/2nhvJBQ – 360MB Buffer Size
Overall it seems the performance on Nightly is a bit better, though still not great. FWIW, the page load is consistently under 3s when devtools are not open.
Unfortunately I can’t share a direct link to the page, and it’s not open source. I can spend some time this afternoon creating a sample project and see if I can get it replicating that way. I’ll update you with a link if I can reproduce in a small project.
Thanks for looking into this!