My Firefox instance has recently picked up the nasty habit of every time I move to a different tab, the web area is white save for a spinning grey loading icon in the center for a good half second. I've never seen anything like this before recently and it's a real bummer on speed
The spinner means the UI process has switched tabs but the content process hasn't painted the tab content yet. Possibly because it's doing something else (like running script).
Is there a particular site that causes this to happen when you have it loaded? If you're willing to spend some time troubleshooting or profiling this, please let me know and I'll walk you through some ways to do that...
If you're using a nightly, you should be able to use https://developer.mozilla.org/en-US/docs/Mozilla/Performance... to profile it, because nightlies have useful symbols. Might be worth capturing a profile at the point when the spinner stops and the page is finally shown.
The issue appears to have resolved itself with a fresh install. I could not replicate the behavior in the nightly, and when I reinstalled the main release it did not manifest again either. Sorry to not be a better help, I'm trying to wrap my head around it...
It's an e10s (multiprocess) thing. Shame that you don't percieve the overall performance as improved, since that's something that e10s promises. But I know that the tab spinner stuff is something they're working on actively, hopefully it'll improve with time.
