Question

significant regression in scrolling performance in firefox 15

I immediately noticed a significant performance regression after upgrading from 14.0.1 to 15. I've seen various comments on input.mozilla.org but it's now a week after release and the latest firefox planning meeting made no mention of it (https://wiki.mozilla.org/Firefox/Planning/2012-09-05) so I thought I would try here.

The first thing I noticed was slow and jerky scrolling of a web page (the same one I was looking at immediately before the upgrade). I tried restarting in safe mode, and while this improved things somewhat, it was still noticeably worse. I also tried with a clean profile with similar results. It was bad enough that I reinstalled 14.0.1 and everything went back to normal.

Now I'm back in 15 to submit this report and I've noticed that the performance is bad in other places too.

  • scrolling in all web pages, even simple ones
  • scrolling the tab bar is also slow and jerky
  • selecting text is so slow that the highlight lags half a second behind the cursor
  • key repeat is now half the speed of other applications
  • youtube videos drop frames all over the place, and WindowServer is the top CPU user when playing

I'm going to revert to 14 again for the time being but if you want me to try anything in 15 I can do that. I'm a developer but don't have any experience with ff so don't know what to try next.

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