1044396 - Phantom CPU usage in OSX Yosemite

Status: RESOLVED INCOMPLETE

(Firefox :: General, defect)

Description

[Marijn de Jong]

Attachment: Screen Shot 2014-07-26 at 10.19.42.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Firefox/31.0 (Beta/Release)
Build ID: 20140716183446

Steps to reproduce:

I opened Firefox 31 in OSX Yosemite public beta, while running activity monitor.


Actual results:

Approx. 12-17% of CPU usage when sitting idle with one tab open on a static page and no animations are on screen.


Expected results:

<1% CPU usage when sitting idle on a static page.

Test it at news.ycombinator.com with acitivty monitor open, like in the attached screenshot.

Comment 1

[Damien Glancy]

I'm getting around 6% CPU when on news.ycombinator.com using Firefox 32 beta channel.

Comment 2

[Marijn de Jong]

(In reply to Damien Glancy from comment #1)
> I'm getting around 6% CPU when on news.ycombinator.com using Firefox 32 beta
> channel.

Actual percentage is of course relative, mine was done on a relatively weak 2009 Mac mini, 2,53GHz Core2Duo.

Comment 3

[me]

Sometimes when I launch facebook and keep it for a while, it can go up for a 100% on (at least) one core. The only way to stop it, is to close the tab. I'm not sure if this happens to you too.

Comment 4

[sterkenburg86]

I have also been experiencing serious problems with CPU usage after the Yosemite upgrade: after browsing for a while, it jumps to 100% and stays there indefinitely even with all the tabs closed(!). The only solution is to quit Firefox completely. The problem seems to be randomly triggered by any task which involves a relatively high CPU usage (last time, it happened after I was scrolling a PDF in the browser).

Booting Firefox in safe mode with all extensions disabled does not solve the issue.

Recent Firefox updates (currently on 33.1.1) and OS X updates (10.10.1) did not change the situation either.

Comment 5

[Wayne Mery (:wsmwk)]

Marijn, do you still see this when using a current version of Firefox?
If so, please do a profile and post the profile URL.
see https://developer.mozilla.org/en-US/docs/Mozilla/Performance/Profiling_with_the_Built-in_Profiler

Comment 6

[Phoenix]

Resolved per whiteboard