1953717 - High CPU load on GitHub pull request pages when checks actively running and showing the progress spinners

Status: NEW

(Core :: Performance: General, defect)

Description

[Henrik Skupin [:whimboo][⌚️UTC+2]]

On GitHub PR pages when checks are running you can see the spinner icon animating for each and every task. Observing the CPU load on a page like https://github.com/mozilla/mozdownload/pull/713 when the checks for several jobs are running, I can see values around 50% all the time.

Here is a gecko profile as recorded when 4 of the checks were running until all of them are done:
https://share.firefox.dev/4iJwBWt

As Emilio stated on Matrix:

• You have an abnormally high refresh rate (we're ticking vsync every 4ms or so, when it should be each ~16)
• The animations are not getting throttled on the main thread

This should be related to:

@keyframes rotate-keyframes {
  100% {
    transform: rotate(360deg);
  }
}

.SpinnerAnimation {
  animation: rotate-keyframes var(--base-duration-1000) var(--base-easing-linear) infinite;
}

Comment 1

[Florian Quèze [:florian]]

(In reply to Henrik Skupin [:whimboo][⌚️UTC+2] from comment #0)

• You have an abnormally high refresh rate (we're ticking vsync every 4ms or so, when it should be each ~16)

I'm seeing vsync markers every 8 or so ms in the profile. That's 120Hz, which is typical for recent macbooks.

Comment 2

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Please note that I have a MBP M4 and in the display settings ProMotion is selected by default which basically means it's a 120Hz refresh rate.

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Yeah, I was just asking Henrik about that :)

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Attachment: Attempt at a test-case

Can you see the issue with this Henrik? I see more flushes than I'd expect, but not continuous like in your profile...

Comment 5

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Here is a Gecko profile when having this testcase open: https://share.firefox.dev/3DHhONl

Comment 6

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Emilio, is that the information you were looking for? Or do I have to provide something else?

Comment 7

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

The severity field is not set for this bug.
:bas.schouten, could you have a look please?

For more information, please visit BugBot documentation.

Comment 8

[Henrik Skupin [:whimboo][⌚️UTC+2]]

(In reply to Henrik Skupin [:whimboo][⌚️UTC+2] from comment #6)

Emilio, is that the information you were looking for? Or do I have to provide something else?

Happy to further help if more details are needed.

Comment 9

[Emilio Cobos Álvarez (:emilio)]

No, that profile helps, but that means that the throttling is working, and something in the github case is causing the throttling not to work..

Comment 10

[Bas Schouten (:bas.schouten)]

The Performance Impact Calculator has determined this bug's performance impact to be low. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: Windows
Websites affected: Major
Resource impact: Some

Comment 11

[Henrik Skupin [:whimboo][⌚️UTC+2]]

(In reply to Bas Schouten (:bas.schouten) from comment #10)

Platforms: Windows

Please note that this is not only Windows. I can see it - and filed it - on MacOS.