CPU usage very high with many tabs open. Pages are idle, content is 100% loaded, CPU is veryhigh.




7 years ago
8 months ago


(Reporter: Mick Russom, Unassigned)



4.0 Branch
Mac OS X

Firefox Tracking Flags

(Not tracked)




7 years ago
User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_6; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.133 Safari/534.16
Build Identifier: ftp://ftp.mozilla.org/pub/firefox/releases/4.0rc1/mac/en-US/Firefox%204.0%20RC%201.dmg

I loaded 67 tabs in chrome, safari and Firefox 3.6.15 and Firefox 4.0 RC1. The Firefox 4.0 RC1 build uses at least one complete core just being idle and sometimes goes over 100% of one CPU and 50% into the second CPU without even counting what the plugin container is doing, thats another 20%.

These pages are not loaded with dynamic content, JS, or flash that is outrageous, so I dont understand how CPU usage could be this high.

I noticed this when testing firefox 4.0 as the laptop got hot for the first time since I've owned it, over 4 months now. 

Reproducible: Always

Steps to Reproduce:
1. start 67 tabs - should not be overly rich, just basic news sites
2. let them finish loading
3. watch how bad idle CPU is
Actual Results:  
results now is that firefox 4.0 rc1 is at least triple 3.6.15 was in the same situation. safari and chrome are much better as well.

Expected Results:  
Why should idle pages and idle content melt the CPU. CPU usage should be at most 25% of one CPU core. 

Please take these seriously - with all the browsers being optimized for embedded usage, tablets, phones, laptops, its CRITICAL that browsers respect power usage and heat creation in portable devices.

Comment 1

7 years ago
This might be the defect I'm seeing. Sometimes when I load a new page, Firefox's CPU usage goes to 50% and becomes unresponsive until it finishes doing...something. I have no idea what Firefox is trying to do, because nothing seems different immediately after the page finishes loading. It does seem like the longer the browser's been open, the longer and more frequent the hangs are, but I have no idea. Mine doesn't seem to be affected by number of tabs, because I just had a hang of at least a minute and I have seven tabs open


7 years ago
Version: unspecified → 4.0 Branch

Comment 2

3 years ago
This seems to be similar to other requests for some way to monitor per-tab CPU usage.  3 years later I still see the same kinds of problems and have to shut down my whole browser periodically due to CPU leakage.

Comment 3

3 years ago
There's "about:performance" page in the current Nightly builds, which tries to track down web pages and add-ons that use CPU.
Duplicate of this bug: 1268864
Mick, do you still see this problem?
Flags: needinfo?(mickrussom)
Keywords: perf
Whiteboard: [closeme 2017-01-15]

Comment 6

a year ago
Resolved per whiteboard
Last Resolved: a year ago
Flags: needinfo?(mickrussom)
Resolution: --- → INCOMPLETE
Whiteboard: [closeme 2017-01-15]
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