Bug: 89.75 - 3.43% imgur ContentfulSpeedIndex / nytimes PerceptualSpeedIndex + 10 more (Linux, OSX, Windows) regression on Wed April 7 2021
Status: RESOLVED
Priority: P3
Resolution: WONTFIX
Created: 2021-04-12 10:07:25+00:00
Resolved: 2024-11-21 17:38:57+00:00

Perfherder has detected a browsertime performance regression from push [1716229005d8b97f305bd663b8bc8d3fec4a4f3a](https://hg.mozilla.org/integration/autoland/pushloghtml?changeset=1716229005d8b97f305bd663b8bc8d3fec4a4f3a). As author of one of the patches included in that push, we need your help to address this regression.

### Regressions:

| **Ratio** | **Suite** | **Test** | **Platform** | **Options** | **Absolute values (old vs new)**| 
|--|--|--|--|--|--| 
| 90% | imgur | ContentfulSpeedIndex | linux1804-64-shippable-qr | cold webrender | 1,352.75 -> 2,566.83 |
| 80% | imgur | ContentfulSpeedIndex | linux1804-64-shippable-qr | cold webrender | 1,352.92 -> 2,437.92 |
| 72% | imgur | LastVisualChange | linux1804-64-shippable-qr | cold webrender | 3,096.67 -> 5,330.00 |
| 23% | youtube | SpeedIndex | windows10-64-shippable-qr | warm webrender | 827.08 -> 1,020.75 |
| 19% | youtube | SpeedIndex | windows10-64-shippable-qr | cold webrender | 1,286.42 -> 1,536.92 |
| 7% | cnn | ContentfulSpeedIndex | linux1804-64-shippable-qr | warm webrender | 1,246.58 -> 1,328.75 |
| 6% | reddit | ContentfulSpeedIndex | windows10-64-shippable-qr | warm webrender | 361.17 -> 384.17 |
| 5% | twitch | ContentfulSpeedIndex | macosx1015-64-shippable-qr | warm webrender | 977.00 -> 1,028.25 |
| 4% | bing-search | ContentfulSpeedIndex | linux1804-64-shippable-qr | cold webrender | 320.08 -> 333.50 |
| 4% | twitch | ContentfulSpeedIndex | macosx1015-64-shippable-qr | cold webrender | 1,009.21 -> 1,047.50 |
| 4% | google-docs | ContentfulSpeedIndex | linux1804-64-shippable-qr | warm webrender | 1,390.08 -> 1,441.58 |
| 3% | nytimes | PerceptualSpeedIndex | linux1804-64-shippable-qr | warm webrender | 851.83 -> 881.08 |

### Improvements:

| **Ratio** | **Suite** | **Test** | **Platform** | **Options** | **Absolute values (old vs new)**| 
|--|--|--|--|--|--| 
| 20% | outlook | ContentfulSpeedIndex | linux1804-64-shippable | warm | 926.88 -> 737.25 |
| 20% | outlook | ContentfulSpeedIndex | linux1804-64-shippable-qr | warm webrender | 991.42 -> 790.58 |
| 19% | yahoo-mail | LastVisualChange | linux1804-64-shippable | warm | 1,096.67 -> 886.67 |
| 19% | youtube | SpeedIndex | linux1804-64-shippable-qr | warm webrender | 1,044.50 -> 849.50 |
| 17% | yahoo-mail | LastVisualChange | linux1804-64-shippable-qr | warm webrender | 1,163.33 -> 960.00 |
| 17% | outlook | ContentfulSpeedIndex | macosx1015-64-shippable-qr | warm webrender | 919.62 -> 763.17 |
| 15% | yahoo-mail | LastVisualChange | linux1804-64-shippable | cold | 1,566.67 -> 1,333.33 |
| 15% | yahoo-mail | LastVisualChange | macosx1015-64-shippable-qr | warm webrender | 1,096.67 -> 933.33 |
| 15% | youtube | SpeedIndex | linux1804-64-shippable-qr | cold webrender | 1,488.75 -> 1,267.67 |
| 14% | yahoo-mail | LastVisualChange | linux1804-64-shippable-qr | cold webrender | 1,626.67 -> 1,403.33 |
| 10% | yahoo-mail | LastVisualChange | macosx1015-64-shippable-qr | cold webrender | 1,603.33 -> 1,450.00 |
| 9% | yahoo-mail | ContentfulSpeedIndex | windows10-64-shippable-qr | warm webrender | 354.12 -> 321.17 |
| 8% | paypal | ContentfulSpeedIndex | windows10-64-shippable-qr | cold webrender | 738.88 -> 682.75 |
| 4% | fandom | ContentfulSpeedIndex | windows10-64-shippable-qr | warm webrender | 219.58 -> 211.08 |
| 4% | imdb | loadtime | android-hw-g5-7-0-arm7-api-16-shippable-qr | warm webrender | 4,221.24 -> 4,061.46 |
| 3% | twitch | ContentfulSpeedIndex | windows10-64-shippable-qr | warm webrender | 1,331.00 -> 1,297.67 |


Details of the alert can be found in the [alert summary](https://treeherder.mozilla.org/perfherder/alerts?id=29667), 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).