Early work on Firefox's new Javascript engine nets big speed gains

Ever since Google dropped Chrome and the V8 Javascript engine on the performance-hungry masses, developers of other browsers have been working hard at leveling the playing field. Opera 10.50's Carakan engine is blazingly fast and many users report it outperforming V8 on benchmarks.

Firefox users who recently upgraded to 3.6 have seen a nice jump in performance as well, though TraceMonkey still lags behind the big guns. That could be changing soon, however. Mozilla's dev team is hard at work on JägerMonkey, which they hope will shift Firefox's Javascript performance into a whole 'nother gear.

One of the speedbumps for Firefox right now is what happens when TraceMonkey can't trace (check out this post to find out more about what tracing is). Firefox falls back to its basic interpreter when JIT compilation isn't possible, and it's just not all that fast.

They're busily retooling what happens when those fallbacks occur, and early performance testing has yielded positive results. Where JägerMonkey can do its stuff, performance gains of 30-40% have been noted. Mozilla's Dave Mandelin like what he sees so far, reporting the "JägerMonkey implements enough JavaScript to run all of SunSpider in "Jäger mode" and is 18% faster than the interpreter." He adds, "And we haven't done that many optimizations yet–there are many more things we will do."

Mandelin's post is an excellent read if you're interested in digging deeper. The short version: Firefox will burn even hotter once JägerMonkey is on board. Keep an eye on the Firefox nightly builds -- it'll likely appear there first.

Tags: firefox, jaegermonkey, javascript, mozilla, performance, speed, tracemonkey