1066255 - 5.46% Win8 Session Restore no Auto Restore regression on v.34 uplift to Aurora September 2, 2014

Status: RESOLVED WONTFIX

(Testing :: Talos, defect)

Description

[Joel Maher ( :jmaher ) (UTC -8)]

This regression is frustrating because it isn't easy to pin down:
http://graphs.mozilla.org/graph.html#tests=[[315,52,31],[315,63,31]]&sel=none&displayrange=90&datatype=running

Looking on this graph, Mozilla-Inbound tracked Mozilla-Aurora until June 22nd (uplift v.32) where Aurora ended up slightly better, but there is no indication of why it is better based on the existing state of mozilla-central merging in.

This stays the same until August 21st where both branches see an improvement.  This is a parallel improvement and they both decline by the same amount.  Now when we uplift v.34 on September 2nd, Inbound stays the same and Aurora regresses (to finally be identical to Inbound).

The problem I have is why did this happen?  Was this some pgo issue (similar or related to bug 1029968)?  It isn't obvious what happened here.

For reference we have session restore [no auto restore] regressions on winxp, win7, win8, osx 10.6, linux32, linux64 as a result of this uplift:
https://docs.google.com/spreadsheets/d/1vjGfGE0GqeX5k3C1XeYfNYP_BEGTpUiux0wgwnGNBro/edit#gid=0

more detailed list of alerts:
http://54.215.155.53:8080/alerts.html?rev=aed50d3edf33&showall=1&testIndex=0&platIndex=0

Comment 1

[Joel Maher ( :jmaher ) (UTC -8)]

Another bug that landed was related to necko: bug 1041511 and bug 354493, this was backed out on inbound June 24th, it seems a bit late, but it also landed and contributed to confusion.

:Yoric, do you know of anything here why session restore is *regressed* and wasn't matched for the last 2 release cycles between aurora and central?

Comment 2

[David Teller [:Yoric] - still alive but not very active]

Normally, neither bug 1041511 nor bug 354493 can have any effect on Session Restore. The only Session Restore-related bug I can think of that my have any effect on startup would be bug 1035557, landed on 34 ~2 weeks ago.

Now, do I read the graph incorrectly, or do I see improvements only?

Comment 3

[Joel Maher ( :jmaher ) (UTC -8)]

on september 2nd (the red line - aurora) goes up a bit, otherwise it is improvements.

Comment 4

[Joel Maher ( :jmaher ) (UTC -8)]

we have already shipped this.