FF2 slowdown after installing IE8?

[rob.g.morton]

Okay, I'm about at my wit's end over this one. I installed IE8 yesterday (plus the latest hotfixes for XP SP2). I did it more to get rid of IE6 than anything else, I primarily use FF2. Since installing IE8 I have been having major performance problems with FF2. Stuff that normally should NOT take up 50% of my CPU (full load of one core) IS. I used to be able to hold down Ctrl-T and get a bunch of new tabs opening in my FF window. Now if I do that they appear one at a time, very slowly, and the CPU pegs at 50% while I do so.

As far as I can tell it's looping in the JS engine (js3250.dll); when the CPU is pegged and I get a call trace from process explorer on the main FF2 thread, I usually see a long chain of calls in js3250.dll. Not sure if these call chains are valid or not; VS2008 won't give me better information when I attach it since none of the binaries have debug info anywhere.

I'm at my wit's end trying to figure this one out. I have started a new (clean) profile, and disabled all plugins -- no change. Reinstalled FF 2.0.0.20 -- no change. I tried FF3; it seemed sluggish but I haven't used FF3 enough to be able to tell if it was slower than usual (I hate that browser; FF3 gets many things wrong that FF2 gets right).

Has anyone else seen behavior anything like this -- installing IE8 (or any recent XP updates) causing FF2 to regularly peg at 100% CPU where it previously did not? Or am I just dealing with something totally crazy?

[Bluefang]

First off, Firefox 2 is no longer supported, so it won't get any more security fixes. We recommend upgrading to Firefox 3. If you have problems with it, we can try and help you sort them out.

There is no reason that installing IE8 would cause performance problem in Firefox. In you tried uninstalling/reinstalling and using a new profile, then I doubt it's a Firefox problem.

Have you tried uninstalling IE8 to see if the problem goes away?

[the-edmeister]

I have seen a few other forum threads about problems with Firefox after installing IE8 - no answers, just a mention of a problem.



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[rasmasyean]

It prolly replaces some "outdated" DLL's or something. Don't use IE8 and FF2 together on the computer. Or if you can find the solution you might be able to make a script to swap files arround to run either or I guess.

[Littlemutt]

It prolly replaces some "outdated" DLL's or something. Don't use IE8 and FF2 together on the computer. Or if you can find the solution you might be able to make a script to swap files arround to run either or I guess.

Total F.U.D. I run both IE8 and Firefox 3.6a1pre version at the same time to compare functions between the two, and page layouts etc... They work quite well together...

[rasmasyean]

It prolly replaces some "outdated" DLL's or something. Don't use IE8 and FF2 together on the computer. Or if you can find the solution you might be able to make a script to swap files arround to run either or I guess.

Total F.U.D. I run both IE8 and Firefox 3.6a1pre version at the same time to compare functions between the two, and page layouts etc... They work quite well together...

How is that "F.U.D."??? Based on what he said, I think it's a reasonable thing to investigate. Sorry for trying to help with a suggestion! Maybe we should wait until you give your opinions on the fact that everyone else's computer is like yours...and case closed!

[Bluefang]

Total F.U.D. I run both IE8 and Firefox 3.6a1pre version at the same time to compare functions between the two, and page layouts etc... They work quite well together...

Yes, but Firefox3 uses different DLL versions than Firefox2. So believe it or not, what rasmasyean suggests is potentially possible.

[rob.g.morton]

Still working on this one. I'm wasting too much time on this; I should just downgrade to FF3, even if I hate most of the "improvements" in it.

Anyhow: I tried renaming the IE8 DLLs that were being imported into FF (ones that showed up as version 8.00.xxxx). FF ran as slow as before (no crashes). Then I noticed that MS thoughtfully provided an uninstall option for IE8. I removed IE8 and am now back on IE6. FF2 is still hopelessly broken.

I decided to try a real profiler, so I downloaded the trial of Intel VTune 9.1 and put it on firefox.exe. I'm no VTune expert, but the topline results seem to confirm my ad-hoc procexp 'profiling':

Most Active Functions In Your Application
(Sampling Hotspot Summary by Process)

Function Name Percentage of process "firefox.exe" Module
js_FindProperty 12.81% js3250.dll
JS_vsxprintf 9.51% js_3250.dll
JS_vsmprintf 8.98% js_3250.dll
RtlReAllocateHeap 5.03% ntdll.dll
tan 4.99% ntdll.dll

All other functions 58.67%

That's pretty damning evidence that *something* is broken in js_3250.dll. There's no reason it should be spinning like that when I'm not *doing* anything. I can turn off JavaScript in the browser; I didn't try profiling, but the behavior was just as slow. And, yes, the assembly for tan in ntdll.dll matches a tangent function... what it's doing *there* is a complete mystery to me (assuming the profiler isn't just confused).

I'm at a total loss to explain the behavior I'm seeing. What could change the behavior of FF, and particularly js_3250.dll, without changing their binaries, to cause this? I should just give up, but now I'm driven to understand what caused this bizarre behavior so I'll know *never to do that again*.

I don't suppose there are old prebuilt debug builds of FF2.0.0.20 floating around somewhere? Compiling one myself looks prohibitive, but I'd be willing to try tracing the call stack in one if I could get my hands on a suitable binary.

[rob.g.morton]

Huh.

I had uninstalled and reinstalled a couple of times before, cleaning out (well, archiving) my profiles before doing so. I didn't try purging the Registry of all Firefox-related data, though (cleaning out the registry is kind of tedious, since there are a lot of MRU lists and file extension crap cluttering up the important bits. In a last-ditch effort, I nuked all of the FF-related registry entries from orbit, including the plugin ones.

And upon reinstalling FF2, the browser was nice and snappy, as it used to be.

I guess one of the registry keys got corrupted somehow, or perhaps when I thought I'd disabled all plugins, I really hadn't. Who knows? If I were going to investigate this further, I'd start with the plugins -- especially the .NET framework ones. I do remember that along with IE8 there was a .NET 3.5 SP1 update installed -- perhaps that broke the FF integration?

Whatever it is, it's fixed now, and I get to go back to using the browser I like: Firefox 2!

[Bluefang]

You do realize that Firefox's UI is written in JS and XUL? That could easily explain the high-usage of the JS library.