Firefox lags when scrolling

[Keepiru]

Binary package hint: firefox-3.0

Scrolling lags badly in Firefox. It's not a consistent problem, but seems to build the longer I keep the browser open. After a day or so, I can spin my scroll wheel ten clicks... Wait... Nothing happens... Start to wonder if it's hung... And then the ten scroll events happen. The delay is very inconsistent, which from a usability standpoint is worse. Instead of just knowing it lags, it has feel like I mistakenly tried to scroll with the wrong window focused. My guess is that there's some garbage collection or something that happens periodically, and if I scroll during it, it has to wait until the *whatever* job is done.

I keep saying scrolling here because it's the most obvious case, but I'm pretty sure all browser operations freeze during the lag time.

This started under 8.10, and seemed to get better when I first switched to 9.04, but it's happening all the time again now. When it gets really bad, Flash videos start having problems too where they'll freeze for several seconds, much like the scrolling freezes. Clicking links to open pages also seems to be affected, again having some sporadic lag. Sadly, Firefox on my old P3-600 with 8.04 feels more responsive than on 9.04 on my Athlon64-5200.

If I exit when it's really bad, Firefox consumes 100% CPU for 10 to 20 seconds after the window closes, but before the process exits. The time seems to be related to how much trouble I'm having with the lag. It'd be awfully interesting to know what it's cleaning up during that time, but I don't know how to find out.

I have a workaround that seems to make it somewhat better: kill firefox, delete localstore.rdf, restart. This seems to work better than just restarting, but it's really hard to do side by side comparisons, since it takes a while to build up to the nasty lag.

I've gone through many gyrations of deleting my profile and reimporting my bookmarks, disabling plugins, and removing Flash, all to no avail.

ProblemType: Bug
Architecture: i386
DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia
Package: firefox-3.0 3.0.10+nobinonly-0ubuntu0.9.04.1
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox-3.0
Uname: Linux 2.6.28-11-generic i686

[Ben Dunlap (bdunlap-agentintellect)]

Similar symptoms here, w/Firefox 3.0.11 & 3.0.12 installed/updated via apt on Ubuntu 9.04 (netbook-remix).

I've noticed that my hard drive is constantly active during the delay. @Keepiru, do you see this as well, or do you just see heavy CPU activity?

"I keep saying scrolling here because it's the most obvious case, but I'm pretty sure all browser operations freeze during the lag time."

Definitely all browser operations cease, or at least all UI ceases. If my mouse cursor is in a non-standard state when the delay starts, it stays that way. Clicks and keyboard operations are ineffective. I *think* mouse and keyboard actions usually queue up and then are all executed when the delay ends.

I see the delay after initial page-loads have completed (almost every time), as well as when scrolling. Unlike the OP, I generally see this behavior immediately after starting Firefox and then throughout the life of the process. I'm not sure that it gets worse over time. So my problem could be different.

Mine Happens on everything from rich AJAX-y pages with multiple external dependencies, to HTML-only pages without any external dependencies. @Keepiru, do you notice any kinds of pages where it doesn't happen, or do you see it across the board?

I suspected Xmarks but not so much now that I've seen a similar report from someone else. Will disable Xmarks all the same and report back.

[Ben Dunlap (bdunlap-agentintellect)]

Hmm, the more I look at this, the more it's starting to look like the following Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=421482

I am seeing loads of fsync() calls when the symptoms occur. @Keepiru, how about you? I'm using strace at the command line to reveal the fsync() calls:

    strace -p <pid of Firefox> -e fsync -tT

[Keepiru (keepiru)]

I do see some very light disk activity during the lag, which I believe is related to profile saves; I don't think it's specifically related to the lag. Mine occurs on any type of page. I typically use a looping gif to test it (no HTML at all).

Nope, this is unrelated to the fsync bug.

I've tracked the problem down to javascript garbage collection. Upstream bug: https://bugzilla.mozilla.org/show_bug.cgi?id=500791

[Launchpad Janitor (janitor)]

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

[Sherif (ali-sherif10)]

The bug remains.

[Sherif (ali-sherif10)]

I experienced lag, while scrolling, after force-enabling hardware acceleration and using AMD's GPU on Fedora also.