Wednesday, February 15, 2006
About the Firefox "memory leak"
A lot of people complain about the Firefox "memory leak(s)". All versions of Firefox no doubt leak memory - it is a common problem with software this complicated. We look to fix the issues where we can. David Baron and others have done a huge amount of excellent work in this area.
What I think many people are talking about however with Firefox 1.5 is not really a memory leak at all. It is in fact a feature.
To improve performance when navigating (studies show that 39% of all page navigations are renavigations to pages visited <>
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 |
| 32MB | 0 |
| 64MB | 1 |
| 128MB | 2 |
| 256MB | 3 |
| 512MB | 5 |
| 1GB | 8 |
| 2GB | 8 |
| 4GB | 8 |
(reference: nsSHistory.cpp)
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.
Edit: In the comments, Boris and David pointed out that I misread the code, and that this is a global preference so that there are no more than 8 cached pages for the entire session, not per tab. My initial posting had claimed that it was per-tab. Oops!
source:http://weblogs.mozillazine.org/ben/archives/009749.html
