Closed Bug 1247100 Opened 4 years ago Closed 4 years ago

5.08% sessionrestore (linux64) regression on push cb036027df84 (Mon Feb 8 2016)


(Firefox :: Disability Access, defect)

Not set



Firefox 47


(Reporter: wlach, Unassigned)



(Keywords: perf, regression, Whiteboard: [talos_regression])


(1 file)

Talos has detected a Firefox performance regression from push cb036027df84. As author of one of the patches included in that push, we need your help to address this regression.

This is a list of all known regressions and improvements related to the push:

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:

Reproducing and debugging the regression:

If you would like to re-run this Talos test on a potential fix, use try with the following syntax:

try: -b o -p linux64 -u none -t other --rebuild 5  # add "mozharness: --spsProfile" to generate profile data

(we suggest --rebuild 5 to be more confident in the results)

To run the test locally and do a more in-depth investigation, first set up a local Talos environment:


Then run the following command from the directory where you set up Talos:

talos --develop -e <path>/firefox -a sessionrestore

(add --e10s to run tests in e10s mode)

Making a decision:

As the patch author we need your feedback to help us handle this regression.
*** Please let us know your plans by Friday, or the offending patch(es) will be backed out! ***

Our wiki page outlines the common responses and expectations:
I was borderline on even reporting this, since it seems to be linux64 non-e10s only (which I assume isn't a configuration we'll be actively supporting soon?), but I figured I should file it at least to acknowledge what happened. 

While its importance may be dubious, it's unmistably a regression, see this comparison view:

mconley: Can you give this a quick gander? Feel free to resolve as wontfix if you think it's not relevant.
Blocks: 1244255
Flags: needinfo?(mconley)
Looking. I'll get some profiles.
Strangely, the back-out of bug 1221144 for bug 1246396 seems to have put us back to where we were... and with that backout landed, the JSM technique I was trying on the 10th in comment 3 no longer has any effect.

I suspect my patch exacerbated a JS problem that was introduced when bug 1221144 landed, and when that was backed out, I think the regression went with it.

Here's where we're currently at:[mozilla-inbound,d8bde8adc167a1143cf99d33f679eb734f3dedc7,1]&series=[fx-team,d8bde8adc167a1143cf99d33f679eb734f3dedc7,1]&highlightedRevisions=dd847049b535&zoom=1454304889313.5518,1455904437303.8086,2016.8115588201993,2364.637645776721

jmaher, do you agree with my assessment?
Flags: needinfo?(mconley) → needinfo?(jmaher)
yes, this seems valid.  This is the second time in 2016 that we have multiple patches playing off each other.  I am just glad that we have this resolved :)
Closed: 4 years ago
Flags: needinfo?(jmaher)
Resolution: --- → FIXED
Target Milestone: --- → Firefox 47
Version: unspecified → Trunk
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