Talos has detected a Firefox performance regression from push: https://hg.mozilla.org/integration/autoland/rev/566486a3aa57 As author of one of the patches included in that push, we need your help to address this regression. Regressions: 16% tabpaint linux64 opt e10s stylo 37.75 -> 43.97 Improvements: 16% tp5o responsiveness windows7-32 pgo e10s stylo 0.59 -> 0.50 10% tp5o responsiveness linux64 opt e10s stylo 0.95 -> 0.86 9% tps windows10-64-qr opt e10s stylo 9.96 -> 9.06 8% tps windows10-64 opt e10s stylo 13.42 -> 12.35 8% tps windows10-64 pgo e10s stylo 11.84 -> 10.92 7% tps linux64-qr opt e10s stylo 9.03 -> 8.39 7% tps windows7-32 opt e10s stylo 11.98 -> 11.18 6% tps linux64 opt e10s stylo 11.06 -> 10.43 6% tp5o responsiveness linux64-qr opt e10s stylo 1.35 -> 1.28 5% tps linux64 pgo e10s stylo 10.71 -> 10.14 4% tps windows7-32 pgo e10s stylo 10.62 -> 10.17 2% tp5o linux64 pgo e10s stylo 133.47 -> 130.29 2% tp5o linux64-qr opt e10s stylo 146.24 -> 143.13 2% tp5o linux64 opt e10s stylo 140.11 -> 137.26 You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=15302 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

This bug was introduced by reverting the patch for bug 1466575. I've re-landed that patch, which should resolve this bug.