Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b12pre) Gecko/20110215 Firefox/4.0b12pre Bug 633382 fixed the extreme memory consumption but there is probably still room for improvements. As given on bug 633382 comment 37 Firefox has a double memory usage when opening the given page with PageTweak installed: enabled disabled Memory 350MB 150MB Also the cpu load is way higher and stays at this level for a longer time, nearly twice as long. This is a regression from Firefox 3.6 which also only uses 150MB but with PageTweak enabled.

http://ftp.mozilla.org/pub/mozilla.org/firefox/tryserver-builds/opettay@mozilla.com-9914d1c9a7f8/ is the build I mentioned to you on IRC. It has the patch for bug 630932.

With the GC/CC scheduling fix (630932) this settles down at 150MB for me after an initial spike where pagetweak seems to do all sorts of crazy stuff.

Looks a lot better with this tryserver build. Thanks Olli.