1285839 - Investigate why an earlier first-paint notification results in Talos regressions

Status: RESOLVED INCOMPLETE

(Core :: Layout, defect, P3)

Description

[Jet Villegas (inactive)]

The fix for bug 1283302 results in Gecko firing the before-first-paint notification earlier than before. The before-first-paint notification initializes the APZC painting code. By design, APZC will paint an area beyond the viewport bounds, which may account for some of the startup hit here. 

However, Firefox would incur this startup cost anyway (after 250ms today) so it seems wrong for Talos to be testing page performance without the first-paint step. 

Filing this bug to track that down.

Comment 1

[Joel Maher ( :jmaher ) (UTC -8)]

added more alerts to this, we see this in Android as well, overall, I suspect whatever fixes we do for desktop will have the same effect on Android.

Comment 2

[Emma Humphries ☕️🎸🧞‍♀️✨ (she/they) [:emceeaich] (Pacific Time) use needinfo]

This is a P1 bug without an assignee. 

P1 are bugs which are being worked on for the current release cycle/iteration/sprint. 

If the bug is not assigned by Monday, 28 August, the bug's priority will be reset to '--'.

Comment 3

[Astley Chen (inactive)]

Is it still P1?

Comment 4

[Maire Reavy [:mreavy]]

Jet -- How important is this bug?  I know it's not a P1, but...

Comment 5

[Jet Villegas (inactive)]

P3 sounds right.

Comment 6

[Mike Conley (:mconley) (:⚙️)]

Closing this as INCOMPLETE - we ended up landing the patch in bug 1283302, and this bug doesn't have much actionable data (which test regressed? No profiles, etc).