630057 - Some pages take much CPU time, even in background tabs

Status: RESOLVED INCOMPLETE

(Firefox :: General, defect)

Description

[Vincent Lefevre]

User-Agent:       Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.4; en-GB; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.4; en-GB; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13

I've found that some pages constantly take much CPU time, even in background tabs. This makes Firefox very slow to react (e.g. it can take several seconds to switch a tab).

Reproducible: Always

Steps to Reproduce:
1. Open http://strangestone.livejournal.com/110451.html in several tabs (in case something changes with this page, the problem can also be seen with YouTube, but this is less visible: one probably needs more tabs).
Actual Results:  
Firefox takes more and more CPU time and is more and more slow to react when one opens more and more tabs.

Expected Results:  
Firefox should always be fast to react. It can possibly take CPU time if need be, but the priorities should be such a way that this should not affect the UI responsiveness and/or what happens in the active (foreground) tab.

I was initially wondering what was happening, because according to the htop utility, the execution time is almost constant, even when it says that Firefox takes 100% CPU time. But it seems to be a bug in htop (perhaps something wrong with threads). The top utility is more reliable; it shows that Firefox takes CPU time, both in % and in execution time.

Bug 622024 may be related to this bug.

Comment 1

[Vincent Lefevre]

Note: this problem seems to be specific to Mac OS X (at least it doesn't seem to occur under GNU/Linux).

Comment 2

[Wayne Mery (:wsmwk)]

http://strangestone.livejournal.com/110451.html no longer exists.
Do you have another failing testcase?

Comment 3

[Vincent Lefevre]

No other testcases for exactly the same problem and I no longer have my Mac OS X machine, but it is known that similar problems happen, e.g. testcase in bug 1193074 shows how to hang the UI for several seconds.

Comment 4

[Wayne Mery (:wsmwk)]

(In reply to Vincent Lefevre from comment #3)
> No other testcases for exactly the same problem and I no longer have my Mac
> OS X machine, but it is known that similar problems happen, e.g. testcase in
> bug 1193074 shows how to hang the UI for several seconds.

That bug is also marked invalid