Talos has detected a Firefox performance regression from push 0efb2a2aff2791f08e19eb5f13d6167a8fd44fe0. As author of one of the patches included in that push, we need your help to address this regression. Regressions: 4% tps summary windows7-32 pgo 54.38 -> 56.63 2% damp summary windows7-32 pgo e10s 199.02 -> 203.87 You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=2936 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

After doing some retriggers, this issue might be caused by the patch: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=e11d9697af59672994c6cdc309c97564078b7dc1&tochange=0efb2a2aff2791f08e19eb5f13d6167a8fd44fe0 Hi JW, as you are the patch author, can you take a look at this and determine what is the root cause? Thanks!

https://treeherder.mozilla.org/perf.html#/compare?originalProject=try&originalRevision=64666d844f3c&newProject=try&newRevision=e86d7507ca63&framework=1&showOnlyImportant=0 e86d7507ca63 includes the backout of bug 1299019 and shows no significant improvements. tps opt linux64 63.30 > 62.80 -0.79% osx-10-10 75.77 < 76.83 1.40% windows7-32 70.61 < 71.47 1.22% tps opt e10s linux64 46.26 > 45.41 -1.84% osx-10-10 38.42 < 39.51 2.84% windows7-32 40.83 < 41.62 1.93% In fact, it is even worse on osx-10-10 and windows7-32. I think it is just a false alarm.

I did some retriggers and it showed no difference. This makes a lot of sense since non pgo builds (i.e. opt builds which we don't ship to users) showed no difference. It would be better to push to try with a pgo build: https://wiki.mozilla.org/ReleaseEngineering/TryChooser#What_if_I_want_PGO_for_my_build when you do push (with the hack for pgo), you could do: try -b o -p win32 -u none -t g2 --rebuild-talos 5 that will run just the test in question and give it enough data to be meaningful.

I did some pushes with pgo builds and the backout: https://treeherder.allizom.org/perf.html#/compare?originalProject=try&originalRevision=2ae853d36cd9&newProject=try&newRevision=c713f22d0d1e&framework=1&showOnlyImportant=0 It will be a few hours before we get results in

ok, with data on the backout, I am not seeing any real wins- most likely this is a red herring- we can close as worksforme.