On Wednesday 2013-08-21 20:52 +0800, Thinker K.F. Li wrote: > I am doing profiling for several Apps on b2g, and have found near 1x% ~ > 20% of CPU time when scrolling are spent on building display list. So, > I think we can use cache for display lists to save time of creating the > same display items repeatedly. > > I just have done some studies, and have a rough idea. My idea is > attaching the caches with frames.
Which items would you cache, on which frames, and for how long? > When a frame is > MarkIntrinsicWidthsDirty()ed, the attached cache is deleted if any. For > the frames that their parents are MarkIntrinsicWidthsDirty()ed for last > reflowing, but not themself, the results of their BuildDisplayList() are > kept in the cache. I guess most animation will modify the same set of > subtrees repeatedly. So, we can save time for building display lists. So clearing caches in MarkIntrinsicWidthsDirty isn't sufficient (at least due to style changes that either change rendering only, or change layout without changing intrinsic widths), and it also doesn't seem like the right point, given the patterns in which it is called (see PresShell::FrameNeedsReflow) and the overall architecture (MarkIntrinsicWidthsDirty is really about intrinsic width changes, which aren't especially related to what you care about here, although there's a correlation). I think I'd be more interested in solutions that are more specific to the problem of scrolling, such as updating an existing display list specifically for scrolling (as mattwoodrow mentioned), or perhaps (though this is less an area where I know what's going on) doing scrolling even further down the pipeline, using layers that are drawn with extra area that we are scrolling towards. -David -- π L. David Baron http://dbaron.org/ π π’ Mozilla https://www.mozilla.org/ π Before I built a wall I'd ask to know What I was walling in or walling out, And to whom I was like to give offense. - Robert Frost, Mending Wall (1914)
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