I just took a profile of scrolling my facebook timeline. I noticed that about 0.1% of the total time in the profile (including idle) was getting frame properties in FrameLayerBuilder::GetPaintedLayerScaleForFrame. This is called a *lot* because we call it multiple times when we reflow a scroll frame, as a result of bug 1012752: nsHTMLScrollFrame::Reflow -> ScrollFrameHelper::GetScrolledRect -> FrameLayerBuilder::GetPaintedLayerScaleForFrame ScrollFrameHelper::ReflowFinished -> ScrollFrameHelper::ScrollToImpl -> FrameLayerBuilder::GetPaintedLayerScaleForFrame It seems like we could consider avoiding this computation, e.g., by: * guarding the LayerManagerDataProperty() with a frame state bit (or bool:1 on nsIFrame if we're out of bits) that says that we have it, if my suspicion that most frames don't have it is correct * storing the scale in the ReflowInput during reflow (and mostly copying from parent to child) -- although I'm not sure how this helps with the ReflowFinished case Or maybe there's something more clever we can do based on where this scale changes? Any ideas, Markus?

See bug 1293031 comment 17 - I think some caching should help a lot here. Milan was playing with this a little but I don't know how far he got. I'll ask him tomorrow.

It looks like tn wrote a patch in bug 1159459 that fixes this, but couldn't measure any improvement so didn't land it.

I wonder if we could avoid the pixel-snapping accuracy when we're: * determining the height of the scrollbar * scrolling somewhere not near the edge of the scrollport

I think tnikkel was going to look into resurrecting his patch.

Probably caching the information we need, and then invalidating it appropriately, is the best option, though.

load-balance to jwatt

No reply from Jwatt on ETA for this bug to be fixed within fx57. Moving to qf:p2

Sorry, Jean, I didn't see a question regarding ETA. I hope to have some patches up for review shortly though.

Note that the work in bug 1363922 may have made this obsolete.

Yeah, I'm not seeing this on Windows 10 any more.