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Firefox on OS X (Macbook Pro 2017 and 2015): - uses 100% CPU even when idle - frame rate drops to 2-3 per second for 5-10 seconds when switching tabs - cause

Firefox on OS X (Macbook Pro 2017 and 2015): - uses 100% CPU even when idle - frame rate drops to 2-3 per second for 5-10 seconds when switching tabs - causes other programs to not work properly because it is using too much CPU I have tried uninstalling the browser and re-installing OS X but it didn't solve those issues. I read somewhere it is a bug that pops up when you have display resolution scaling on and I think it applies to me because I have two 4k monitors set at 2x scaling.

pixelrevision 8y ago
Entirely anecdotal but I have noticed huge issues with Firefox when I hook my laptop up to a 4k display. My normal display is 1080p and no issues on the same machine.
JohnBooty 8y ago
uses 100% CPU even when idle That sucks. Anecdotally, I've never seen this, even when I had 1 external 4K and 1 external 2K connected. The whole OS was kind of sluggish at that point, but that was definitely asking a lot out of a puny integrated 3-year old laptop GPU so eh. Just did a quick informal test with my current setup: - MacOS High Sierra. - 2015" MBP with no discrete GPU. - Single 4K external monitor, 3008x1692 scaled resolution. - uBlock is off. With only a single blank tab open FF uses 0% CPU as expected. I opened three tabs: Facebook, Espn.com, and MSNBC.com. There was a brief flurry of CPU activity as the sites loaded, and FF's processes are now idling comfortably at 0-1%. I repeated the process with Chrome and results were similar. One difference is that Chrome spawns 10x as many processes, but they seem to consume less memory each. In both FF and Chrome, there's a palpable (500 or 750ms?) delay when switching tabs. In my experience a lot of Mac apps behave that way at scaled 4K resolutions. I repeated this informal test in Safari and it "feels faster"; less CPU spike on initial site load and switching browser tabs feels close to instant.

pixelrevision 8y ago

Entirely anecdotal but I have noticed huge issues with Firefox when I hook my laptop up to a 4k display. My normal display is 1080p and no issues on the same machine.

JohnBooty 8y ago

uses 100% CPU even when idle That sucks. Anecdotally, I've never seen this, even when I had 1 external 4K and 1 external 2K connected. The whole OS was kind of sluggish at that point, but that was definitely asking a lot out of a puny integrated 3-year old laptop GPU so eh. Just did a quick informal test with my current setup: - MacOS High Sierra. - 2015" MBP with no discrete GPU. - Single 4K external monitor, 3008x1692 scaled resolution. - uBlock is off. With only a single blank tab open FF uses 0% CPU as expected. I opened three tabs: Facebook, Espn.com, and MSNBC.com. There was a brief flurry of CPU activity as the sites loaded, and FF's processes are now idling comfortably at 0-1%. I repeated the process with Chrome and results were similar. One difference is that Chrome spawns 10x as many processes, but they seem to consume less memory each. In both FF and Chrome, there's a palpable (500 or 750ms?) delay when switching tabs. In my experience a lot of Mac apps behave that way at scaled 4K resolutions. I repeated this informal test in Safari and it "feels faster"; less CPU spike on initial site load and switching browser tabs feels close to instant.