ESR38 isn't going to have jemalloc3. But the code is in the FF tree, well-integrated, and while I wouldn't call it 'supported', the mozilla devs are at least pretty familiar with it. I wanted to see if there was anything that would stop Tor from potentially using it even if FF isn't.
The mozilla bug is https://bugzilla.mozilla.org/show_bug.cgi?id=762449
Their concerns are, at least: - mismatched calls to VirtualAlloc/Free: https://github.com/jemalloc/jemalloc/issues/213 (This can be resolved by a patch in comment #1 which is slower than they'd like) - performance concerns - I think there are issues on mobile platforms, but I'm not entirely clear there
There are probably more, but these were the ones I was able to discern. I decided to test the performance question, with and without the patch. I ran a slew of in-browser benchmark sites on an Ubuntu desktop, running mozilla-release tag FIREFOX_38_0_RELEASE.
The results are close, and it looks like the current jemalloc (2?) outperforms jemalloc3, but that jemalloc3 (even with the patch) is not significantly more painful. Both compare favorably to chromium for instance.
Bigger is better for all but the last chart (which labels it in the title).
If Tor wanted to consider turning on jemalloc3 in TBB, I would suggest the following: 1) Seeing if the heap isolation based on class of object (e.g. js strings/arrays) is implemented, and if not, what it would take to do so. If it's not there and it's hard to do, there's not much point to turning to jemalloc3 2) Round up the mozilla devs and lay it out as a real possibility and get their input
I will work on #1 as I'm able.
-tom
Benchmarks: http://peacekeeper.futuremark.com http://browsermark.rightware.com/ http://dromaeo.com/ http://v8.googlecode.com/svn/data/benchmarks/v7/run.html http://octane-benchmark.googlecode.com/svn/latest/index.html http://browserbench.org/Speedometer/ http://browserbench.org/JetStream/ http://v8.googlecode.com/svn/branches/bleeding_edge/benchmarks/spinning-ball... http://www.webkit.org/perf/sunspider/sunspider.html http://krakenbenchmark.mozilla.org/index.html