Scrolling http://www.mac-tv.de/index.lasso?Rubrik=Filme is pretty slow, especially compared to Safari. -[NSView _drawRect:clip:] seems to be getting called a lot more than in Safari which suggests that we are invalidating a lot more than we should be, and therefore doing a lot more work than Safari. I used the following dtrace script to count function calls: pid$target:CoreGraphics:CGContextShowGlyphsWithAdvances:entry { @[probefunc] = count(); } objc$target:NSView:-_drawRect?clip?:entry { @[probefunc] = count(); } Firefox with ~5 seconds of scrolling -_drawRect:clip: 12355 CGContextShowGlyphsWithAdvances 32624 Safari with ~5 seconds of scrolling CGContextShowGlyphsWithAdvances 2778 -_drawRect:clip: 4218

Scrolling on the URL feels good to me (Linux and OSX).

Timothy could you try the dtrace script to see how Firefox compares to Safari? Maybe we still perform worse than Safari, also if the scrolling perf seems good.