1684434 - 10.6 - 16.1% amazon-search loadtime (android-hw-p2-8-0-android-aarch64-shippable) regression on push 8f99f380963006b37b6662b4d06bfd1a62ac2ad5 (Mon December 21 2020)

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Alexandru Ionescu (needinfo me) [:alexandrui]]

Perfherder has detected a browsertime performance regression from push 8f99f380963006b37b6662b4d06bfd1a62ac2ad5. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
16%	amazon-search	loadtime	android-hw-p2-8-0-android-aarch64-shippable	nocondprof warm	789.62 -> 916.75
11%	amazon-search	loadtime	android-hw-p2-8-0-android-aarch64-shippable	nocondprof warm	812.17 -> 898.28

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the offending patch(es) will be backed out in accordance with our regression policy.

For more information on performance sheriffing please see our FAQ.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1683220

Comment 2

[Steve Fink [:sfink] [:s:]]

(In reply to Alexandru Ionescu (needinfo me) [:alexandrui] from comment #0)

let us know your plans within 3 business days, or the offending patch(es) will be backed out

This should be backed out. I only tested performance with talos and raptor, because browsertime has been hanging perfherder for me and so I haven't been able to see the results there. This week, it's doing better -- it takes a while, but then gives me results. (I will note that some results are labeled as having Infinity confidence, which seems rather suspicious, but that's a separate problem.)

Ugh. This means that the complicated optimization is important. I'll look for a simpler way of getting the same effect. If not, I'll unearth my code to migrate it to the new setup.

Comment 3

[Julien Cristau [:jcristau] (back April 22)]

Fixed by backout as requested:
https://bugzilla.mozilla.org/show_bug.cgi?id=1683220#c6

Comment 4

[Steve Fink [:sfink] [:s:]]

Since I'm continuing to work on this, I'm going to mention here that all changes were on Android, save 4. Of those 4, there were 2 improvements and 2 regressions. (The magnitude of the improvements was slightly more than the regressions, but they're not really comparable, so I'll just say it was a wash.)

Also, bug 1685020 shows +3% and -3%, again no net difference.

Given the dromaeo_css improvements in bug 1683220 comment 5, I'm inclined to conclude that this is a small net improvement other than on Android.

Comment 5

[Florin Strugariu [:Bebe]]

Backout alert:

== Change summary for alert #28384 (as of Tue, 12 Jan 2021 12:11:30 GMT) ==

Regressions:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
6%	bbc	LastVisualChange	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	2,935.83 -> 3,101.08
5%	amazon-search	LastVisualChange	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm	4,842.17 -> 5,107.08

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
14%	amazon		android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	545.72 -> 468.02
14%	amazon		android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	544.03 -> 468.36
13%	amazon	FirstVisualChange	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	592.58 -> 517.08
12%	amazon	SpeedIndex	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	627.25 -> 551.33
12%	amazon	PerceptualSpeedIndex	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	633.33 -> 559.25
12%	amazon	ContentfulSpeedIndex	android-hw-g5-7-0-arm7-api-16-shippable	nocondprof warm webrender	636.33 -> 562.92
8%	amazon-search	loadtime	android-hw-p2-8-0-android-aarch64-shippable	nocondprof warm webrender	739.58 -> 681.33
4%	amazon-search	fcp	android-hw-p2-8-0-android-aarch64-shippable	nocondprof warm webrender	427.52 -> 408.79

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28384