Talos has detected a Firefox performance regression from push: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?changeset=90c70e5122f6da891b59c579a3c7d0c02a6610d4 As author of one of the patches included in that push, we need your help to address this regression. Regressions: 10% dromaeo_dom linux64 pgo e10s stylo 3,759.18 -> 3,375.50 10% dromaeo_dom linux64 opt e10s stylo 3,489.51 -> 3,144.74 8% dromaeo_css linux64 opt e10s stylo 15,933.35 -> 14,699.71 8% dromaeo_css linux64 pgo e10s stylo 17,009.93 -> 15,728.68 5% dromaeo_css osx-10-10 opt e10s stylo 8,939.17 -> 8,481.51 You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=12033 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 Talos jobs in a pushlog format. To learn more about the regressing test(s), please see: https://wiki.mozilla.org/Buildbot/Talos/Tests For information on reproducing and debugging the regression, either on try or locally, see: https://wiki.mozilla.org/Buildbot/Talos/Running *** Please let us know your plans within 3 business days, or the offending patch(es) will be backed out! *** Our wiki page outlines the common responses and expectations: https://wiki.mozilla.org/Buildbot/Talos/RegressionBugsHandling

:nbp I know Dromaeo perf regressions were expected. Please close this bug as WONTFIX unless the magnitude of the regressions is bigger than expected.

Closing this bug as WONTFIX as this matches the previous try result, on which we agreed on in the Spectre meeting. Dromaeo regresses by 10% because it tests the added Spectre mitigation in a tight loop for DOM property getters and methods.