372306 - Firefox cause X to take 30%+ CPU while tabbed page waiting to load

Status: RESOLVED INCOMPLETE

(Firefox :: Tabbed Browser, defect)

Description

[Jon Burgess]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9a3pre) Gecko/20070301 Minefield/3.0a3pre
Build Identifier: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9a3pre) Gecko/20070301 Minefield/3.0a3pre

Originally raised by me against FC6 with mozilla-1.5.0.9. Also seen on 2.0.0.2 and 3.0a3pre.

I've noticed that when firefox waits for a page to load the X server often takes
30%+ CPU. After trying a lot of combinations I think i've finally narrowed this
down to a problem with the tabbed window support.

Reproducible: Always

Steps to Reproduce:
1. Launch firefox -ProfileManager
2. create new profile with default options and launch.
3. try accessing a page which does not exist. For me http://10.0.0.1 is a good
one. This causes the browser to try loading the page for ~30 seconds until timeout.
4. While firefox is still trying to load the page, open an xterm run top. Look
at X cpu usage. 
5. After a few seconds of activity X will show ~1% CPU usage (i.e. everything
looks normal now).
6. Stop page load in firefox.
7. Go into preferences->tabs. Enable the "show tabs even when only one window
open" option so that the tab bar appears.
8. Try going to http://10.0.0.1 again.
9. Watch X CPU usage. For me X jumps to 30%+ and stays there for the 30+ seconds
that firefox tries to load the page
Actual Results:  
Having the tab bar open seems to cause firefox to hammer the X server while
loading new pages. 


Expected Results:  
This is running FF on an AMD64 3000 so I don't expect the X server to need 30%+
CPU in order to tell me that FF is waiting for a page to load. When the tab bar is not visible the same page load causes X cpu usage <1%.


I'm using an NVidia FX5200 with the open source 'nv' driver. 
I tried disabling pango with no effect.
The high X CPU still occurs even with firefox minimised so I don't think it is
due to the X driver code trying to repaint the screen.

Also the same occurs when 2+ tabs are open, but only if the page waiting to load is in the foreground.

I tried using xmon to see what Mozilla was doing and I think it was creating and destroying pixmaps very rapidly, but this was the first time i've tried running this tool so i'm not certain about understanding the results.

Comment 1

[Tyler Downer [He/Him]]

This bug was reported using Firefox 3.0 or older, which is no longer supported. The bug has also not been changed in over 500 days and is still in UNCO.
Reporter, please retest this bug in Firefox 3.6.10 or later using a fresh profile, http://support.mozilla.com/en-US/kb/managing+profiles. If you still see this problem, please update the bug. If you no longer see the bug, please set the resolution to RESOLVED, WORKSFORME.

This is a mass search of unconfirmed bugs that have no activity on them, so if you feel a bug was marked in error, just remove the CLOSEME comment in the whiteboard within the next month.

Comment 2

[Tyler Downer [He/Him]]

No reply, INCOMPLETE. Please retest with Firefox 3.6.12 or later and a new profile (http://support.mozilla.com/kb/Managing+profiles). If you continue to see this issue with the newest firefox and a new profile, then please comment on this bug.