Firefox "spins" destroying system performance

Binary package hint: firefox

Originally reported on Ubuntu 9.10; problem persists on 10.04.
Information that may help...

- network link is through Netgear 3G router with AT&T Mercury "air card". Link RTT can vary or even drop briefly (typical cell phone behavior). Most RTTs are in the 180-220ms range.

- I believe the RTT / link status is relevant, because I don't see the problem when I am on the office LAN connecting through a T1 land line.

- Problem reminds me of Java memory fragmentation issues I saw years ago running Firefox on Windows. Then reboots always helped. Not always the case now, i.e, doing a restart may or may not clear the problem.

- Often firefox is sucking cpu cycles, even when window minimized and nothing other than auto refresh of NY Times front page is going on. Here's typical 'ps' output, though the CPU/us number is a bit low compared to what I often see.

Tasks: 196 total, 1 running, 195 sleeping, 0 stopped, 0 zombie
Cpu(s): 27.5%us, 7.9%sy, 0.0%ni, 63.8%id, 0.0%wa, 0.6%hi, 0.1%si, 0.0%st
Mem: 4113120k total, 1100904k used, 3012216k free, 71900k buffers
Swap: 4805624k total, 0k used, 4805624k free, 591028k cached

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
 1750 jak 20 0 386m 97m 31m S 41 2.4 35:55.55 firefox-bin
 1783 jak 20 0 166m 41m 18m S 14 1.0 26:45.58 plugin-containe
 3264 root 20 0 2476 1216 892 R 6 0.0 0:03.10 top
 1333 root 20 0 63124 48m 15m S 4 1.2 20:16.13 Xorg
 1733 jak 20 0 48392 12m 9476 S 4 0.3 1:14.78 gnome-terminal
 2051 jak 20 0 295m 115m 79m S 2 2.9 10:33.04 soffice.bin
  326 root 20 0 0 0 0 S 1 0.0 0:43.68 usb-storage
   62 root 20 0 0 0 0 S 0 0.0 0:03.43 kondemand/1
  296 root 20 0 0 0 0 S 0 0.0 0:10.94 scsi_eh_1
  834 root 20 0 0 0 0 S 0 0.0 0:05.14 iwlagn

- Invariably, Xorg is taking as much CPU as firefox when this occurs, and screen repaints and mouse click responsiveness is painfully slow. It's not uncommon to have the "slow script" warning pop-up too, though that is by no means typical.

- I can find nothing on Ubuntu and Firefox forums that looks like this, but I may have missed something.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: firefox 3.6.6+nobinonly-0ubuntu0.10.04.1
ProcVersionSignature: Ubuntu 2.6.32-23.37-generic-pae 2.6.32.15+drm33.5
Uname: Linux 2.6.32-23-generic-pae i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Tue Jul 27 16:00:38 2010
FirefoxPackages:
 firefox 3.6.6+nobinonly-0ubuntu0.10.04.1
 firefox-gnome-support 3.6.6+nobinonly-0ubuntu0.10.04.1
 firefox-branding 3.6.6+nobinonly-0ubuntu0.10.04.1
 abroswer N/A
 abrowser-branding N/A
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox