Bug: 46.42 - 2.05% welcome fcp / welcome PerceptualSpeedIndex + 5 more (Linux, OSX) regression on Tue December 14 2021
Status: RESOLVED
Priority: --
Resolution: WONTFIX
Created: 2021-12-22 07:30:16+00:00
Resolved: 2021-12-23 10:35:54+00:00

Perfherder has detected a browsertime performance regression from push [0331c56022c9747db6b9abeb3ab6920189cb1044](https://hg.mozilla.org/integration/autoland/pushloghtml?changeset=0331c56022c9747db6b9abeb3ab6920189cb1044). 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)**| 
|--|--|--|--|--| 
| 46% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) fcp | macosx1014-64-shippable-qr | cold webrender | [123.56](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/I1PQ2atzQdWcx7gPV1zmvw/runs/0/artifacts/public/test_info/browsertime-results.tgz) -> [180.92](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/TfDA9mONRhuaumIyXIBvgQ/runs/0/artifacts/public/test_info/browsertime-results.tgz) |
| 46% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) fcp | macosx1014-64-shippable-qr | cold webrender | 117.48 -> 171.04 |
| 4% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) ContentfulSpeedIndex | linux1804-64-shippable-qr | cold webrender | 1,469.17 -> 1,524.67 |
| 4% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) SpeedIndex | macosx1014-64-shippable-qr | cold webrender | 1,453.17 -> 1,505.50 |
| 3% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) ContentfulSpeedIndex | macosx1015-64-shippable-qr | cold webrender | 1,539.62 -> 1,590.83 |
| 3% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) SpeedIndex | linux1804-64-shippable-qr | cold webrender | 1,243.92 -> 1,283.67 |
| 2% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) PerceptualSpeedIndex | macosx1014-64-shippable-qr | cold webrender | 1,585.38 -> 1,617.88 |
### Improvements:

| **Ratio** | **Test** | **Platform** | **Options** | **Absolute values (old vs new)**| 
|--|--|--|--|--| 
| 7% | [amazon](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#amazon-d) PerceptualSpeedIndex | macosx1014-64-shippable-qr | cold fission webrender | 893.46 -> 835.08 |
| 3% | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) ContentfulSpeedIndex | macosx1014-64-shippable-qr | warm webrender | 1,383.89 -> 1,343.00 |


Details of the alert can be found in the [alert summary](https://treeherder.mozilla.org/perfherder/alerts?id=32746), including links to graphs and comparisons for each of the affected tests. Please follow our [guide to handling regression bugs](https://wiki.mozilla.org/TestEngineering/Performance/Handling_regression_bugs) and **let us know your plans within 3 business days, or the offending patch(es) will be backed out** in accordance with our [regression policy](https://www.mozilla.org/en-US/about/governance/policies/regressions/).

For more information on performance sheriffing please see our [FAQ](https://wiki.mozilla.org/TestEngineering/Performance/FAQ).