In testing out Firefox 3.0 over the last several months I realized that when loading up a page in a foreground tab when two or more tabs were present, my single core CPU maxed out and loading slowed to a crawl making the browser unresponsive until I switched the tab into the background to let it finish loading. At that point, CPU usage returned to normal. As long as the tab that was loading remained in the background, the CPU never rose above an average of 20% max not counting the occasional spike or two from flash and script content.
Other folks were having these problems also which included high initial memory use for some as well so after much troubleshooting and constructive cursing I finally found the culprit that was causing this high CPU/memory use problem and I’m passing it on.
The fix is actually pretty simple and involves changing the state of “browser.cache.memory.enable” in Firefox’s “about:config“. Just follow the simple instructions under the image below:
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Type “about:config” into the FIrefox 3 RC1 location bar and tell it you’ll be careful (you’ll see what I mean).
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When the list of configuration options shows up, type “cache” without the quotes into the search bar as shown above. A list of all entries will appear with the word “cache” in them.
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Change the state of the “browser.cache.memory.enable” entry to “false” by double clicking on the entry itself. Make sure the state has indeed changed to “false”.
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Restart the browser and you’re done.
Firefox 3 should now run right along nice and fast no matter what tab is loading in the foreground and without the high CPU use as I saw before the change and apparently the memory problem is also fixed. Performance does not seem to be degraded at all by this change and speeds things up nicely.
If this fix helps anyone running Firefox 3.0.*, please leave a comment and let me know as I’m really curious if this works for others as well. You might also leave your two cents worth at the Mozillazine forum thread I started for this problem and if you really wish to make a difference you can post your findings or add your vote on the bug report I also filed.
Note (07/15/09): This fix is only for the Firefox 3.0.* series as Firefox 3.5 and above does not suffer from this problem. Also, not all Firefox 3.0.* users will experience this problem as it seems to be dependent on certain hardware configurations. Unfortunately, due to the numerous possible configurations of PC hardware (and yes, the acronym PC also includes Macs as PC simply stands for “Personal Computer”) it’s next to impossible to track down the exact cause.
Thanks!
Tags: Firefox, Firefox 3, Firefox high CPU, Firefox high memory
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thanks this is a nice article.
Your fix works great for me so far. I am using CachemanXP to monitor my cpu and memory usage. While ordering a new cellphone on Verizon’s website, I had to wait for close to 5 minutes for the payment to go through. That made me look at CachemanXP to see what was going on. And there it was, my beloved Firefox was two timing me! lol. Anyway thanks for the fix!
How does disabling Firefox’s memory cache help with CPU usage? My answer is that it doesn’t. If Firefox is suffering from high CPU usage, maybe you have a crappy extension installed. Or maybe your profile is corrupt and you should try reinstalling Firefox into a new profile.
This tip does work for me. Thanks so much. Using FF v3.5.
Gustavo – My pleasure.
Thanks. It works…
rgds.
Is this fix for any version of Firefox? Or is this just for the new updated version that hasn’t been released?
Dee
Hi Dee – This fix is only for the Firefox 3.0.* series of the browser and I’ve updated the post to reflect this (thanks for reminding me to do this). Firefox 3.5 doesn’t exhibit the same problem. Firefox 3.5 does have it’s own bugs that can cause High CPU usage and slow start up time which can be solved by clearing Internet Explorer’s cookies, cache and browsing history along with Firefox’s as well and that should solve the problem (Firefox 3.5 shares some of it’s cache with IE when installed on Windows by what I understand so if IE is clogged up it will affect Firefox 3.5 as well).
HTH
geeknik – Sorry for the late reply. And yes, what you’ve stated are the standard things that can cause trouble with any version of Firefox and should be checked by any user experiencing a problem with a Firefox install but as a tester of Mozilla products I can assure you that all this was done long before any bug report was filed. It’s just standard troubleshooting for those who are experienced in troubleshooting. This problem was well researched and disabling extensions, using fresh profiles, starting in safe mode, etc had no effect on it. If you read the bug report or the forum thread you would see that the problem was tracked down between 2 nightly builds.
I only posted the fix for those experiencing the problem, troubleshooting other user’s installs was not my intention.