1872455 - Scrolling a gecko profile on a 1440p monitor subjectively feels janky (blocking on the Compositor?)

Status: RESOLVED FIXED

(Core :: Graphics: Canvas2D, defect)

Description

[Mayank Bansal]

I originally noticed this with DPI=1.5. But to make it easier to repro, follow these STR below:

0. Maximize your monitors resolution and set DPI=1.
1. Open the URL https://share.firefox.dev/41F6Q2k (gecko profile)
2. Maximize the "graph pane" by minimizing the "details pane"(i.e resize the detail pane vertically)
3. Using the touch-pad, scroll the graphs view quickly.
   AR: There is noticeable jank for 100s of milliseconds.

Bad: https://share.firefox.dev/41KgL6L / https://share.firefox.dev/48goMD2
Good: https://share.firefox.dev/3TIshxz

My naive understanding of the bad vs good is that the "bad" moves the blocking to the compositor, instead of the content-process thread (which may be the intended behaviour of the recent canvas changes).
Subjectively, in the good profile during scrolling there is minor jank and "checkerboarding" . In the bad profile, it felt like the page freezes for that duration.

I did a regression, that points to this :
Bug 1871467 - Remove unnecessary CanvasTranslator locking. r=aosmond CLOSED TREE

Differential Revision: https://phabricator.services.mozilla.com/D197112

On retesting, it feels like that the "good" version were somewhat janky too. So the above regression made the page somewhat worse, but in a different way.

This use-case is pretty niche, so the wider user impact is minimal. In any case, this is not an urgent bug.

Edit: Just for reference, https://share.firefox.dev/47h4ecf is with gpu-canvas. This was completely smooth.

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1871467

:lsalzman, since you are the author of the regressor, bug 1871467, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 3

[Mayank Bansal]

Did not improve with bug 1874534. https://share.firefox.dev/3RV4S9H

Comment 4

[Bob Hood [:bhood]]

Soft freeze for Fx123 is this Thursday. Is this something we feel comfortable letting go to Beta?

Comment 5

[Lee Salzman [:lsalzman]]

This is not critical at all.

Comment 6

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1871467

Comment 7

[Mayank Bansal]

Latest profile : https://share.firefox.dev/4568ZWD
Calling this fixed by bug 1863257 and co.