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by lwansbrough 3009 days ago
+1 for Firefox eating CPU. For some reason they can't track down the issue. If there's anyone from Mozilla reading, I'm on a Late 2013 13" rMBP fully loaded. I've made all the recommended changes to improve performance (and undone all of them as well to ensure they weren't the problem.) Firefox consumes most of my CPU and causes my fans to run at the full 6200 RPM while they try to cool my CPU which consistently reaches beyond 80C on any page running any Javascript.
5 comments

Talking about "the issue" is a misunderstanding of how performance of complex software works. Overall performance is the result of the entire codebase, and there can be a varieety of ways that performance problems can manifest for individual users. One of the most productive approaches to improving performance with Quantum was fixing lots and lots of small and medium sized issues across the product that individually didn't have much impact but overall added up to a significant improvement.

There can be all sorts of reasons that specific sites or specific installations might show performance problems that aren't representative of the typical experience. Your specific environment might have some feature (particular hardware, profile data, addons, etc.) that happen to trigger a bad case in some code and so lead to an overall slowdown. Or you might be regularly using a site that happens to do something that's CPU intensive in Firefox but less so in other browsers. This could be a Firefox problem (maybe we implemented a feature using an algorithm with different tradeoffs compared to other browsers and it so happens that everyone avoids the worst case behaviour in Chrome, but not in Firefox, maybe our implementation just has issues that can be fixed), or it could be a site problem (sometimes sites just send buggy, broken code to specific browsers that causes them to use lots of CPU for no reason).

One of the things that was most valuable during the Quantum project was the work to improve the profiling tools. If you can capture a profile using the super-easy-to-use gecko profiler[1] and create a bug with the profile attached it should be possible to figure out what exactly is causing the problem in your case. Without that data it's really hard to make progress because the kind of problem you experience is just not something that would be allowed to ship if it was known.

[1] https://developer.mozilla.org/en-US/docs/Mozilla/Performance...

This. If it's becoming unusable on my pretty beefy i7/16GB (Ubuntu), how does it work for the average Joe?

It is a showstopper. I don't care about new features if it can't handle basic stability.

See, sibling post https://news.ycombinator.com/item?id=16647116 Please record a profile and report this.
Bad logic it works great on my several year old tablet and my 4 year old laptop with 2 cores.

If it was broken for everyone it would already have been fixed.

Works fine on my weak ass thinkpad (i3-4010U) o_0
Whereas on my i5 thinkpad ('14 t430) I had to switch to chrome as my browser, which was annoying, but even on a clean win10 insstall w/ only FF installed, it would peg the cpu hard. Don't know why, as I still use it as my primary browser for my desktop as well as android phone, but ever since Quantum there just seems to be a significant number of systems that are incompatible with firefox.

Oh, and before anyone asks, on the thinkpad the performance issue was still present on a debian stretch install as well.

Just because it works on your system doesn't mean this isn't a bug they need to fix.

One of the actual Firefox processes doing that? On my MBP the problem seems to be plugin-container, or most probably one of the third-party plugins running inside. Which is to say, either Cisco's H.264 codec or Google's video DRM module. `killall plugin-container` helps but also crashes basically all pages requiring video support, requiring reload.
Try opening about:performance from the address bar to see if a particular site is slowing it down
Even with no extension ?