“Adblock Plus’ for FireFox won’t give you the detailed readouts we’re fiending for, but it will allow you to switch off SPECIFIC items on page. You can turn off .js files that you think are unnecessary, like urchin.js for google analytics (if you don’t feel the need to be counted), or some stupid image to vote for a site as number 1 at Animegames.com or where ever.

It starts simply. You click “block” on all the repetitive flash ads for Warcraft and other crap. You’ve seen them a hundred times, slowing down your PC, wasting your resources. You’re never going to buy, primarily because they don’t just use a text ad.

Then, you get more advanced. CTRL+Shift+V opens the ‘blockable items’ pane, which you use to start cutting out little blinking animated gif files—How cute!—and image ads for wedding planning services that you don’t want your girlfriend to see (probably still hoping she’ll settle for a second hand dress and lots of glitter).

Finally, you end up admitting that you never had too much of a problem with any of them, in the first place. Right back to where we started: just plain interested in what the heck is going on!

It is multithreaded for all intents and purposes, just not with preemptive native OS/pthreads. It has green threads, like I said in the article.

As long as FireFox knows which javascript function comes from what page (and they have to because of the “window” global variable) then they can keep track of which page is running what code and present me with a list of pages and % of time spent running scripts in them.

No! This sentiment seems to be shared by many people, but it’s just not true. Generally Firefox is perfectly fine with that many windows and tabs open. Which means generally pages are well behaved with regard to javascript.

But sometimes it does what I described above and I wish I had a way to track down which page is the one with the problem.

I do run Flashblock, but I didn’t want to rule out some bit of flash I enabled running somewhere. I actually think it is way more likely that javascript is the culprit.

@baczek:

I’ve been running FF3 beta 3 and I notice that today beta 4 is out. The nightlies make me a bit nervous. We’ll see how beta 4 handles things (so far the betas have been much more memory conscious than FF2, but more prone to CPU spinning).

@Zeev:

That’s a good idea, but it seems a bit tedious. It may eventually come to that.

@mlh:

I don’t really have access to a Solaris machine. But I am running OS X to which dtrace was recently added. Does anyone know if OS X Firefox has dtrace hooks enabled?

@fuffuf:

I do expect it to behave nicely. When there’s no user input the only thing that should be happening is javascript timeouts and animated gif timeouts. Since I use adblock I generally don’t have any animated gifs sitting on pages. If a page has a timeout set and it’s doing a bunch of calculations constantly it’s really a badly designed page. I really think Firefox shouldn’t honor JS timeouts if the tab isn’t even visible.

According to Activity Monitor it is taking 1.1 GB of virtual memory but only 450MB of that is in physical memory. There is no active swap thrashing going on. About once a second something goes and allocates 20MB of RAM and then frees it. But I have enough free RAM that it is not going to swap.

@Robert O’Callahan:

That’s good news. If it doesn’t do what I want it sounds like it could at least be a good piece of code to adapt. Hope it comes out soon…

I normally don’t engage in flamebaits, but I’d like to give just one counter-example to your statement: Firebug. Recently, I read an announcement somewhere that IE8 will include a tool similar to Firebug, so that means that Microsoft did in fact “steal” an original and great idea that a Firefox user had. Not that I have a problem with that, this competition will only increase the quality of both products making it better for the users of both products.

Also, because javascript must run in single threaded mode and objects can reference DOM objects from other tabs/windows, all the javascript in the firefox process runs as a single thread, so they can’t really implement top easily.

What’s really killing me in windows is the svchost process, now that’s stupid.

@EasyAnswer

It’s the other way around, Firefox leaks memory and get copied.

You’re right, this would be a cool tool. There’s some students working on a “PluginWatcher” extension to monitor plugin activity.

Still, a “what’s running where” capability would be nice too — along with some fine-grained control over the JS interpreter.