Even die-hard Mozilla Firefox fans will likely admit that their browser of choice is a memory hog. Firefox often leaks memory like there's no tomorrow, and seeing it eat up half a gig of memory or more isn't an uncommon occurrence. However, the next major release of the browser will be much more spartan in its memory use, according to Ars Technica.
Using the same benchmark mentioned by Mozilla developer Stuart Parmenter in this blog post, Ars set out to compare the memory use of the Firefox 3 beta 4 release with that of Firefox 126.96.36.199, Internet Explorer 7, the Opera 9.5 beta, and the Safari 3.0.4 beta. The results speak for themselves: Firefox 3 is the least memory-hungry by far, so much so that its peak memory usage is lower than Firefox 2's lowest. The highest memory use for Firefox 3 beta 4 was less than 225MB, while Firefox 188.8.131.52 seems to have peaked at around 275MB. Opera 9.5 sat between the two. Meanwhile, IE7 peaked at nearly 500MB and Safari hit nearly 350MB before crashing near the beginning of the test.
Ars also goes into some of the techniques Mozilla employed to trim Firefox 3's memory use, including the use of the FreeBSD jemalloc memory allocator, the reduction of total memory allocations, and an XPCOM cycle collector that "automatically detects unused objects that are persisting as a result of mutual references." Considering Firefox 3 is still at least a few weeks away from release, seeing this level of performance already out of the fourth beta is promising indeed.