Current Aurora builds (which will eventually become Firefox 6) have an improved about:memory page, which includes buttons that make Firefox run the garbage collector:
In my experience, hitting the GC button rarely makes any detectable improvement. Right at this very moment my Firefox instance is using about 900MB of memory; hitting all three buttons in a row (garbage-collection, cycle-collection, "minimize memory usage") brings the number down to 892MB, ~750MB of which is apparently allocated to "heap-unclassified" and the JavaScript "gc-heap".
Work on reducing Firefox's memory footprint is ongoing; the most recent effort I know of is MemShrink:
http://blog.mozilla.com/nnethercote/2011/05/23/a-better-abou...
In my experience, hitting the GC button rarely makes any detectable improvement. Right at this very moment my Firefox instance is using about 900MB of memory; hitting all three buttons in a row (garbage-collection, cycle-collection, "minimize memory usage") brings the number down to 892MB, ~750MB of which is apparently allocated to "heap-unclassified" and the JavaScript "gc-heap".
Work on reducing Firefox's memory footprint is ongoing; the most recent effort I know of is MemShrink:
http://blog.mozilla.com/nnethercote/2011/03/10/memshrink/
...and it's beginning to make some progress:
http://blog.mozilla.com/nnethercote/2011/06/22/memshrink-pro...