1584138 - 0.76 - 0.76% Base Content JS (windows7-32, windows7-32-shippable) regression on push e35199501a974eb8c6582d4c5a0e87e3d4932f68 (Mon September 23 2019)

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine, defect)

Description

[Marian Raiciof [:marauder]]

We have detected an awsy regression from push:

https://hg.mozilla.org/integration/autoland/pushloghtml?changeset=e35199501a974eb8c6582d4c5a0e87e3d4932f68

As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

1% Base Content JS windows7-32 opt 3,214,357.33 -> 3,238,944.00
1% Base Content JS windows7-32-shippable opt 3,214,368.00 -> 3,238,933.33
1% Base Content JS windows7-32-shippable opt 3,214,368.00 -> 3,238,944.00

You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=23235

On the page above you can see an alert for each affected platform as well as a link to a graph showing the history of scores for this test. There is also a link to a treeherder page showing the jobs in a pushlog format.

To learn more about the regressing test(s), please see: https://wiki.mozilla.org/AWSY/Tests

Comment 1

[Ted Campbell [:tcampbell]]

This is due to js::BaseScript having an odd number of fields so padding is added on 32-bit to make the BaseScript type gc::Cell-aligned.

BaseScript is a transition data structure until the work of Bug 1529456 is complete. It is expected to land long before Fission is enabled, so I'm marking this as WONTFIX. The next field that gets moved from LazyScript to BaseScript will remove the regression.

Comment 2

[Marian Raiciof [:marauder]]

Thanks for the details, Ted!