1372881 - 2.38 - 3.04% sessionrestore / sessionrestore_no_auto_restore / ts_paint (linux64) regression on push 321e5a4f37b5 (Tue Jun 13 2017)

Status: RESOLVED WONTFIX

(Firefox :: Session Restore, defect)

Description

[Ionuț Goldan [:igoldan]]

Talos has detected a Firefox performance regression from push:

https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=92a8b8ce2f728ea5cc4ea8e4d8b3e2c5fe76a9ed&tochange=321e5a4f37b543c73055159b9630621890fc8b4e

As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

  3%  sessionrestore_no_auto_restore linux64 opt e10s     656.08 -> 676.00
  3%  sessionrestore linux64 opt e10s                     629.33 -> 645.83
  2%  ts_paint linux64 opt e10s                           1,069.83 -> 1,095.25


You can find links to graphs and comparison views for each of the above tests at: https://treeherder.mozilla.org/perf.html#/alerts?id=7259

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

Comment 1

[Ionuț Goldan [:igoldan]]

:florian The patch above resolves multiple bugs. The ones I find more related to these regressions are bug 1372152, bug 1372326 
and bug 1371710. Could you confirm the regressions and point to the right bug?

Comment 2

[Florian Quèze [:florian]]

Bug 1372152 is touching Windows-only code, so definitely unrelated.

Bug 1372326 is very likely the cause, as it adds additional instrumentation during startup. This is only for non-release builds (nightly or debug builds), so if that's indeed the cause, this bug is wontfix... unless we find a smart way to make that code run only during mochitests, but not during normal runs or talos runs.

Comment 3

[Ionuț Goldan [:igoldan]]

(In reply to Florian Quèze [:florian] [:flo] from comment #2)
> Bug 1372152 is touching Windows-only code, so definitely unrelated.
Thanks for pointing this out. This helped me identify the improvement source for sessionrestore and tresize from alert https://treeherder.mozilla.org/perf.html#/alerts?id=7261

Comment 4

[Ionuț Goldan [:igoldan]]

(In reply to Florian Quèze [:florian] [:flo] from comment #2)
> Bug 1372326 is very likely the cause, as it adds additional instrumentation
> during startup.

Backout of Bug 1372326 mostly confirms this as the origin.

Baseline results from https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=92a8b8ce2f728ea5cc4ea8e4d8b3e2c5fe76a9ed&tochange=321e5a4f37b543c73055159b9630621890fc8b4e :
https://treeherder.mozilla.org/#/jobs?repo=try&revision=26b10ec38fb2b9cddbe06e77017bcff6b82412d0

Backout of Bug 1372326: https://treeherder.mozilla.org/#/jobs?repo=try&revision=6a568c24ef3df0ab814030f50a3effe8ff7f6230

Comparison view: https://treeherder.mozilla.org/perf.html#/compare?originalProject=try&originalRevision=26b10ec38fb2&newProject=try&newRevision=6a568c24ef3d&framework=1&showOnlyImportant=0

The backout hinted only linux64 improvements on sessionrestore (-1.35%), sessionrestore_no_auto_restore (-2.21%) and ts_paint (-1.67%).