Bug: 5.95 - 5.3% welcome loadtime / welcome loadtime (Windows) regression on Fri April 21 2023
Status: RESOLVED
Priority: P1
Resolution: FIXED
Created: 2023-04-25 11:17:18+00:00
Resolved: 2023-05-02 16:09:57+00:00

Perfherder has detected a browsertime performance regression from push [006b14fabebdd378e088d4aedd30340040941d78](https://hg.mozilla.org/integration/autoland/pushloghtml?changeset=006b14fabebdd378e088d4aedd30340040941d78). 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** | 
|--|--|--|--|--|--| 
| [6%](https://treeherder.mozilla.org/perfherder/graphs?timerange=1209600&series=autoland,3913747,1,13)  | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) loadtime | windows10-64-shippable-qr | fission warm webrender | [35.35](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/CmKmDBW8S7-qLAD-iKUFBw/runs/0/artifacts/public/test_info/browsertime-results.tgz) -> [37.46](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/IhBPStDOQsuQiuAPUygqrg/runs/0/artifacts/public/test_info/browsertime-results.tgz) | [Before](https://profiler.firefox.com/from-url/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FCmKmDBW8S7-qLAD-iKUFBw%2Fruns%2F0%2Fartifacts%2Fpublic%2Ftest_info%2Fprofile_welcome.zip)/[After](https://profiler.firefox.com/from-url/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FIhBPStDOQsuQiuAPUygqrg%2Fruns%2F0%2Fartifacts%2Fpublic%2Ftest_info%2Fprofile_welcome.zip) |
| [5%](https://treeherder.mozilla.org/perfherder/graphs?timerange=1209600&series=autoland,3913743,1,13)  | [welcome](https://firefox-source-docs.mozilla.org/testing/perfdocs/raptor.html#welcome-c) loadtime | windows10-64-shippable-qr | cold fission webrender | [54.25](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/CmKmDBW8S7-qLAD-iKUFBw/runs/0/artifacts/public/test_info/browsertime-results.tgz) -> [57.12](https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/IhBPStDOQsuQiuAPUygqrg/runs/0/artifacts/public/test_info/browsertime-results.tgz) | [Before](https://profiler.firefox.com/from-url/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FCmKmDBW8S7-qLAD-iKUFBw%2Fruns%2F0%2Fartifacts%2Fpublic%2Ftest_info%2Fprofile_welcome.zip)/[After](https://profiler.firefox.com/from-url/https%3A%2F%2Ffirefox-ci-tc.services.mozilla.com%2Fapi%2Fqueue%2Fv1%2Ftask%2FIhBPStDOQsuQiuAPUygqrg%2Fruns%2F0%2Fartifacts%2Fpublic%2Ftest_info%2Fprofile_welcome.zip) |


Details of the alert can be found in the [alert summary](https://treeherder.mozilla.org/perfherder/alerts?id=38180), 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) may be backed out** in accordance with our [regression policy](https://www.mozilla.org/en-US/about/governance/policies/regressions/).

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a sheriff to do that for you.

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