The browser causes 20-40% CPU load when displaying an animated gif

[Alexander Broshevich]

When firefox is displaying a gif, for example http://i.imgur.com/MVKsc.gif , the CPU is under constant 20-40% load and system feels to run slower. Same load with and without any addons. When i remove the element which contains the gif via firebug, the load instantly drops to 1-2%.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: firefox 9.0.1+build1-0ubuntu0.11.10.2
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic 3.0.9
Uname: Linux 3.0.0-14-generic x86_64
NonfreeKernelModules: wl fglrx
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: vlad 1888 F.... pulseaudio
 /dev/snd/controlC0: vlad 1888 F.... pulseaudio
BuildID: 20111228084940
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xfbf00000 irq 52'
   Mixer name : 'IDT 92HD81B1X5'
   Components : 'HDA:111d7605,10280447,00100105'
   Controls : 14
   Simple ctrls : 9
Card1.Amixer.info:
 Card hw:1 'Generic'/'HD-Audio Generic at 0xfbe40000 irq 53'
   Mixer name : 'ATI R6xx HDMI'
   Components : 'HDA:1002aa01,00aa0100,00100200'
   Controls : 4
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Channel: release
Date: Sat Jan 14 22:43:13 2012
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
IncompatibleExtensions: LastPass - <email address hidden>, Version=1.80.0, minVersion=1.9a2, maxVersion=1.9.6, Location=app-profile, Type=extension, Active=Yes
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
IpRoute:
 default via 192.168.0.1 dev eth0 proto static
 169.254.0.0/16 dev eth0 scope link metric 1000
 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.3 metric 1
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=9.0.1/20111228084940 (Running)
RunningIncompatibleAddons: True
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/19/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A15
dmi.board.name: 0WK2G6
dmi.board.vendor: Dell Inc.
dmi.board.version: A15
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: A15
dmi.modalias: dmi:bvnDellInc.:bvrA15:bd07/19/2011:svnDellInc.:pnInspironN5010:pvrA15:rvnDellInc.:rn0WK2G6:rvrA15:cvnDellInc.:ct8:cvrA15:
dmi.product.name: Inspiron N5010
dmi.product.version: A15
dmi.sys.vendor: Dell Inc.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[G.M. (sexxxenator)]

I have the same problem, but on an old dual-core desktop machine, firefox takes up to 105% CPU (or more) and often freezes the whole machine.

A typical example is when sufing the:
http://izismile.com/
web site and open a few tabs with some of its pages. There's always a moment where you open a page like:
http://izismile.com/2016/06/03/page,2,daily_gifdump_30_gifs.html
and the whole firefox / computer freezes.

Interestingly, just opening a single tab with the page:
http://izismile.com/2016/06/03/page,2,daily_gifdump_30_gifs.html
alone does not seem to cause any problem.

Also, using about:config and all its options to clean up memory (GC/CC/Minimize) does not help...

So I assume there is a memory leak somewhere that reveals itself under high usage.