Over time I have been collecting various Firefox tweaks… this is my collection of performance tweaks that i used to tame down Firefox 2.x on Mac. These work on all platforms but they really helped with the mac version too
Firefox Excessive Memory Usage
1. Within Firefox, enter “about:config” (minus the quotation marks) in the address bar
2. Scroll down to the entry “browser.sessionhistory.max_total_viewers” and double-click it.
3. In “Enter integer value” field, type..
* “0” to disable the cache
* “1” through “8” to set the maximum cache as 1 through 8 previously-viewed pages
* “-1″ to return the cache to its default
Max Total Viewers
To improve performance when navigating (studies show that 39% of all page navigations are renavigations to pages visited < 10 pages ago, usually using the back button), Firefox 1.5 implements a Back-Forward cache that retains the rendered document for the last few session history entries. This can be a lot of data. It’s a trade-off. What you get out of it is faster performance as you navigate the web.
For those who remain concerned, here’s how the feature works. Firefox has a preference browser.sessionhistory.max_total_viewers which by default is set to -1. When set to this value, Firefox calculates the amount of memory in the system, according to this breakdown:
RAM Number of Cached Pages
No more than 8 pages are ever cached in this fashion, by default. If you set this preference to another value, e.g. 25, 25 pages will be cached. You can set it to 0 to disable the feature, but your page load performance will suffer.