imdb on macosx10-14 is bimodal.
Please investigate and fix the dual results on the test

https://treeherder.mozilla.org/perf.html#/graphs?timerange=5184000&series=autoland,2052623,1,10&series=mozilla-inbound,2055663,1,10

The bimodal model has been visible after we updated to mitmproxy 4.0.4

== Change summary for alert #22182 (as of Mon, 29 Jul 2019 14:33:28 GMT) ==

Improvements:

13% raptor-tp6-imdb-firefox loadtime macosx1014-64-shippable opt 1,267.89 -> 1,099.67

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=22182

Linux graph is stable
https://treeherder.mozilla.org/perf.html#/graphs?timerange=5184000&series=autoland,1927314,1,10

I wonder if it's possible that acreskey's findings on settimeout have anything to do with this: https://bugzilla.mozilla.org/show_bug.cgi?id=1564569

It could be interesting to try applying his patch (which removed bimodality from android tp6m tests): https://hg.mozilla.org/try/rev/8868280b9d43efc8955edbd26b14d278d92dc381
And then seeing if the bi-modal results still exist.

See also Bug 1578694

I think this is related with Bug 1578694

patch with acreskey changes
https://treeherder.mozilla.org/#/jobs?repo=try&revision=abc41cb0e95a593292b91df9cca30847cf93993c

https://treeherder.mozilla.org/perf.html#/graphs?timerange=604800&series=autoland,2052623,1,10&series=try,2014373,1,10&highlightedRevisions=abc41cb0e95a593292b91df9cca30847cf93993c&highlightAlerts=1