Would you be interested in help to profile the issue and file a detailed bug? This would help fix it.
What i don't get is that it's an unknown problem, many people have already filed bug reports on the tracker:
https://news.ycombinator.com/item?id=18626325
(also see several blog posts like: https://www.kamshin.com/2018/07/firefox-on-macos-insane-batt...)
I think it has to do with running the Macbook Pro at scaled resolution which is pretty much standard among devs on MB pro no? (otherwise you will have very little screen real estate).
I just created i Profile through the Gecko profiler once again but i don't know if that captures the CPU data? What external profiler do you use?
Profile here from Firefox nightly, 1 minute of scrolling around https://fs8.transfernow.net/download/5c0a9b99f98e/master/Fir...
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Very non scientific test below that i need to external profiler to confirm:
Symptoms:
I get a hot computer when browsing / working normally
high CPU usage leading to
fans constantly running and battery drain
Doesn't happen in other browsers
Comparative methodology:
Open 20 tabs and scroll a bit up and down for 1 minute.
Check CPU usage in Activity monitor.
Check fan speed an temp.
Repeat in all major browsers.
Result:
Safari, Chrome and Opera the fans stays silent and i get moderate CPU usage.
Firefox the fans kick in quickly (also ran first to have a fair baseline temperature).
Do I understand correctly that you're checking CPU usage immediately after having scrolled up/down, or while scrolling up/down, right?
Apparently, there are already people working on that bug. If I understand things correctly, Firefox uses transparent windows, but transparent windows use lots of CPU on some macOS configurations, and this somehow wasn't detected during testing (I imagine that the computers used for testing didn't have these configurations).
If this is the same bug, as is likely, the bug is identified and developers are working on it: https://bugzilla.mozilla.org/show_bug.cgi?id=1429522 . If you wish, you may leave a message on that bug mentioning that you are available for profiling and testing a fix.
It is my impression (but don't take my word on it) that the fix will ship in Firefox 65, which is currently in Nightly. Now, I'm not sure that the fix has already landed in the current Nightlies, but do you have the possibility of testing on Firefox Nightly if the problem is still present?
(usual caveat: Nightly has Telemetry activated by default – if you don't like Telemetry, don't forget to disable it)
Apparently, the bug is already identified, so this might not be necessary. More details in my answer here: https://news.ycombinator.com/item?id=18634165 .
If you wish, you may leave a message on https://bugzilla.mozilla.org/show_bug.cgi?id=1429522 mentioning that you are available for profiling and testing a fix.
