[Bug 348964] [NEW] Firefox unresponsive even when plenty of resources

[Cefn]

Public bug reported:

Binary package hint: firefox

Latest Firefox on Intrepid 8.10 frequently pauses and becomes
unresponsive for a period of approx 4 seconds when switching windows, or
typing, or scrolling, or practically anything in fact.

I've had this for months across two completely independent installs and
I'm finally getting sick of it, hence this report. I use Firefox a lot,
and it's getting to be an obstacle which will require me to switch to a
new browser soon.

This pausing behaviour is accompanied by greying out when running in
Compiz, but it happens with XFCE4 also, where you simply see it as a
freeze, before your keystrokes or mouse inputs actually make it through
to the application.

It happens when no other windowed apps are running.

If any other windowed apps are running in the OS, they remain totally
unaffected and they continue throughout with full responsiveness.

This suggests to me that it's something firefox-specific, and the OS
seems to be fine for available memory and CPU in general, as long as I
don't switch to Firefox to try and do something, in which case it
spuriously pauses every 30 seconds or so whilst it does something I know
not what.

I'm running Firefox in Xubuntu to make sure that there are plenty of
resources for my apps. I have a 1.2GHz Core Solo and 1gig of ram, so I'd
expect Firefox to be able to run 20 or 30 windows at once. However, it
doesn't seem to make any difference if I'm only running 3 or 4.

It's as if the Firefox thread is entering some kind of 100% CPU loop for
a brief period to do some maintenance/garbage collection or something,
until it frees itself up and decides to run again.

The problem here is that the tasks I'm undertaking are almost zero load
tasks - I'd understand it more if I was rendering video or debugging
with Firebug. However, I have Flashblock installed and configured to
prevent all Flash from loading. Firebug is installed but disabled. More
often than not, there are almost no activities going on in any of the
windows, except me typing or clicking, but still Firefox can't handle
the load and has to pause while it does something.

Happy to serve up whatever extra information needed about my system or
plugins sessions or whatever if anyone knows how best to get this
information out as part of the bug report.

** Affects: firefox (Ubuntu)
     Importance: Undecided
         Status: New

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Firefox unresponsive even when plenty of resources
https://bugs.launchpad.net/bugs/348964
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