PaintTouchActionRects has been enabled!

[Philip Rogers]

PaintTouchActionRects is a project to re-implement how Blink sets the compositor touch-action regions by re-using the paint system to "paint" touch action rects. It's been enabled by default for about two weeks (https://crrev.com/607991) and is on-track to be in M72.

Here's a summary of the project's goals, results, and implementation: https://docs.google.com/document/d/1ksiqEPkDeDuI_l5HvWlq1MfzFyDxSnsNB8YXIaXa3sE/view

Early results are looking great, including a 5% reduction in Canary Android's total Mainframe.UpdateTime metric. Canary Android's ScrollingCoordinator.UpdateTime 99th %ile went from 14ms to 3ms.

[Chris Harrelson]

Awesome work! Really amazing.

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[Adrienne Walker]

Holy moly, those are some nice perf numbers!

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[dan...@chromium.org]

So awesome :) 🙌

 

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[Robert Flack]

This is great! Thanks for all the hard work! I'm amazed by how significant the impact of this has been.

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[Timothy Dresser]

Awesome work!

Was the impact here large enough to show up in any of our top level metrics?
Maybe one of: 

• Event.Latency.ScrollBegin.Touch.TimeToScrollUpdateSwapBegin42
  
• Event.Latency.ScrollUpdate.Touch.TimeToScrollUpdateSwapBegin42
  
• Scheduling.Renderer.DrawInterval2
  

Tim

[Philip Rogers]

The change is just hitting dev channel and it's possible we're seeing a small-percentage drop in Event.Latency.ScrollBegin.Touch.TimeToScrollUpdateSwapBegin4 at the 50% but it's a little too early to tell. Blink changes are more likely to affect the lower-percentiles (<=50%) of TimeToScrollUpdateSwapBegin4 because the higher-percentiles are dominated by something else (see: histograms), likely script.

[Rick Byers]

Awesome work everyone! 

Ever since I overhauled this system back in 2013 I had wanted to see it re-implemented in terms of the paint system - it's clearly the right architecture. Thank you for finally removing all my terrible hacks and heuristics!

Perhaps someone should update the public compositor touch hit testing design docs page to at least indicate it's now obsolete and to reference the new design?

Thanks!

   Rick

[oj...@google.com]

\o/ any progress on the initiating link navigation network requests on the compositor thread experiment?

[Philip Rogers]

No progress but I plan to do the investigation in Q1. The potential benefits have been estimated but it may be complex to actually implement, so the plan is to figure out how implementable it is.

For others, https://docs.google.com/document/d/14P2mK2JnH0LzvD5CiXWz29P6dlimT2Rg_7fgPzgA5wo has more information about this project.