1697803 - 6.71 - 8.22% raptor-assorted-dom-firefox (linux64-shippable, linux64-shippable-qr) regression on push a0ee10a962a025723bcf5eb8c92a2412ad54c55f (Fri March 5 2021)

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Ionuț Goldan [:igoldan]]

Perfherder has detected a raptor performance regression from push a0ee10a962a025723bcf5eb8c92a2412ad54c55f. 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)
8%	raptor-assorted-dom-firefox		linux64-shippable	nocondprof	73.66 -> 79.71
7%	raptor-assorted-dom-firefox		linux64-shippable-qr	nocondprof webrender	76.23 -> 81.35

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 1689413

Comment 2

[Jan de Mooij [:jandem]]

I verified we generate exactly the same CacheIR as before. I think what's happening is that for window.performance we call the generic binding getter and this has some checks for proxies/wrappers that require an extra dereference now. This was an intentional trade-off we made in bug 1689413 that's unlikely to affect non-micro-benchmarks as much.

I'm hoping we can optimize this the coming months by checking the shape kind instead of the JSClass flags to determine whether an object is a proxy, that would save us two dereferences and would be faster than before.

For now I'll see if we can use the optimized DOM getter code for this.

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1697803 - Use DOM getter optimization for GetProp on WindowProxy too. r?evilpie!

This is similar to what we do for GetName already.

Comment 4

[Jan de Mooij [:jandem]]

(In reply to Jan de Mooij [:jandem] from comment #2)

For now I'll see if we can use the optimized DOM getter code for this.

I posted a patch for this. It makes the benchmark about 3 times faster than before (and actually very close to what it was before we enabled Warp).

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a71077321e06
Use DOM getter optimization for GetProp on WindowProxy too. r=evilpie

Comment 6

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/a71077321e06

Comment 7

[Florin Strugariu [:Bebe]]

== Change summary for alert #29329 (as of Fri, 19 Mar 2021 10:07:06 GMT) ==

Improvements:

Ratio	Suite	Test	Platform	Options	Absolute values (old vs new)
70%	raptor-assorted-dom-firefox		linux1804-64-shippable	nocondprof	78.60 -> 23.95
67%	raptor-assorted-dom-firefox		linux1804-64-shippable-qr	nocondprof webrender	81.44 -> 26.66
67%	raptor-assorted-dom-firefox		linux1804-64-shippable-qr	nocondprof webrender	80.83 -> 26.59

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=29329