Perfherder has detected a browsertime performance regression from push 8dbbc6a6b494858ae0f76375e2a69b0e1df03a73. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

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 offending patch(es) may be backed out in accordance with our regression policy.

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Set release status flags based on info from the regressing bug 1648158

If this Android regression only affects Fission, we don't need to back out the regressing changeset because we don't enable Fission for any Android users yet.

The final regression there is Linux Fission, but judging from the patch, I don't see how that could be to blame.

P3

Some more information on how these page load performance tests work:

To rerun this on try, the job name is test-android-hw-p2-8-0-android-aarch64-shippable-qr/opt-browsertime-tp6m-geckoview-wikipedia. It uses the browsertime-tp6m config file (https://searchfox.org/mozilla-central/source/testing/raptor/raptor/tests/tp6/mobile/browsertime-tp6m.ini), which specifies things like browser_cycles = 15 and page_cycles = 25. On Try, browsertime uses chimera, which specifies a page_cycle = 2, meaning it loads a webpage cold, measures, then reloads and measures to get a warm page load. You can see in the log (https://firefoxci.taskcluster-artifacts.net/ey8RSsimSGS73pYVCdlDLA/0/public/logs/live_backing.log) cycle 0 and cycle 1 for iteration 1. Since browser cycles are 15, it runs 15 iterations of this cold and warm page load combination.

Navigating to about:blank, count: 0
Navigating to url about:blank iteration 1
Navigating to primary url:https://en.m.wikipedia.org/wiki/Main_Page
Cycle 0, waiting for 1000 ms
Cycle 0, starting the measure
Testing url https://en.m.wikipedia.org/wiki/Main_Page iteration 1
[runs command calls to screen record]
Navigating to about:blank, count: 1
Navigating to url about:blank iteration 1
Navigating to primary url:https://en.m.wikipedia.org/wiki/Main_Page
Cycle 1, waiting for 1000 ms
Cycle 1, starting the measure
Testing url https://en.m.wikipedia.org/wiki/Main_Page iteration 1
[runs command calls to screen record]
Browsertime pageload ended.
https://en.m.wikipedia.org/wiki/Main_Page TTFB: 67ms DOMContentLoaded: 1.50s firstPaint: 1.49s FCP: 1.30s Load: 1.94s
VisualMetrics: FirstVisualChange: 1.67s SpeedIndex: 1.67s PerceptualSpeedIndex: 1.68s ContentfulSpeedIndex: 1.67s VisualComplete85: 1.67s LastVisualChange: 2.55s
https://en.m.wikipedia.org/wiki/Main_Page?browsertime_run=2 TTFB: 150ms DOMContentLoaded: 385ms firstPaint: 288ms FCP: 272ms Load: 581ms
VisualMetrics: FirstVisualChange: 312ms SpeedIndex: 411ms PerceptualSpeedIndex: 379ms ContentfulSpeedIndex: 342ms VisualComplete85: 414ms

The source code for page loads is https://searchfox.org/mozilla-central/source/testing/raptor/browsertime/browsertime_pageload.js#336-412.