As measured in [1], the instruction retirement rate (instructions/cycle or IPC) for paint traversal (LocalFrameView::paintTree) is about 70% of the surrounding code (0.27 vs 0.40). This code path also shows a high number of instruction and data cache misses. We should investigate where the difference in execution speed is coming from and whether it could be optimized.

[1] https://docs.google.com/document/d/15WWzZYFvG-WiZ-Pvrpd4tYYnCmvz5WUmrtg1SQevuPE/edit?pli=1#