I can see some pretty strong effects (and false positives) from what seem to be TLB misses. On my system, on Firefox, the L2 size is not detected correctly if transparent huge pages are enabled, but on Chromium it is. I'd like to take a closer at what's going on, but the tooling for performance-related debugging in browsers seem to be more or less missing. I've opened a pull request for some fixes to the C implementation though.
It's certainly possible that there are some TLB issues with transparent huge pages that mess up the results. I've had a terrible time debugging the performance across different machines, browsers and OSes, and there seem to be an uncountable number of things that can go wrong, especially with the JITs in play. I'll try to track this one down later today, but I can't make any promises.
