1859492 - 30.86% espn ContentfulSpeedIndex (Windows) regression on Fri October 13 2023

Status: RESOLVED WONTFIX

(Testing :: Performance, defect)

Description

[Alexandru Ionescu (needinfo me) [:alexandrui]]

Perfherder has detected a browsertime performance regression from push 576a3a6fd4d4f0f6118d63312df282f4e8d15314. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
31%	espn ContentfulSpeedIndex	windows10-64-shippable-qr	cold fission webrender	755.51 -> 988.67	Before/After

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the patch(es) may be backed out in accordance with our regression policy.

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Comment 1

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 1856449

Comment 2

[Timothy Nikkel (:tnikkel)]

In the screenshots, the "after" profile seems to have action in the little loading panel in the bottom left much later than in the "before" profile. Which is exactly the opposite of what you would expect given the regressing bug.

Comment 3

[Alex Thayer [:alexical] (she/her)]

I think it makes sense actually. Previously, iframe loads would both show and hide the status panel in the bottom left. This meant that if you have one long toplevel load and a very short load in an iframe, the load in the iframe will actually end up hiding the status panel much earlier when it finishes.

I think we either need to exclude the status panel from our ContentfulSpeedIndex calculation or just accept this loss, because it is not actually negatively affecting user experience.

Comment 4

[Ed Lee :Mardak]

Do we want to update the test per comment 3?

Comment 5

[Greg Mierzwinski [:sparky]]

This looks like the same issue we had in the past and we filed bug 1762951 for it.

Comment 6

[Alex Thayer [:alexical] (she/her)]

I'm just going to WONTFIX this, given that 1762951 will fix it, but it's not quite a duplicate. Feel free to reopen.