Besides Weekend performance spikes on mac looks like we have this for andoid as well.

== Change summary for alert #23995 (as of Tue, 19 Nov 2019 04:15:08 GMT) ==

Improvements:

31% raptor-tp6m-amazon-geckoview-cold loadtime android-hw-p2-8-0-android-aarch64 pgo 1,090.08 -> 755.58

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=23995

Thank you for spotting this Alexandru -- this is quite interesting and further evidence that the host machine is under such a heavy work load that it's interfering with the android client.
Here I would have to guess mitmproxy is struggling to return the resources, but so far that's just a guess. (Which I'll be able to verify in Bug 1589356)

Alex: Are we still seeing weekend spikes on Android or can we close this?

Dave, it doesn't seems like they are there anymore.