1821108 - EmberJS-TodoMVC spends a lot more time in removeListenerFrom doing array splicing than in V8

Status: NEW

(Core :: JavaScript Engine, task, P2)

Description

[Markus Stange [:mstange]]

In the function removeFromListener in the EmberJS-TodoMVC benchmark, we spend 3080 samples inside Array.prototype.splice versus V8's 739 samples.

To reproduce, run index.js inside https://github.com/mozilla/Speedometer/tree/ab0e3b8406bbc0356244f8cd430900e9a346737b/resources/todomvc/architecture-examples/emberjs/dist in the JS shell.

Profiles (focused on removeFromListener's "JS-only self time"):
Spidermonkey: https://share.firefox.dev/3mGyBXK
V8: https://share.firefox.dev/3ylHwR0

Comment 1

[Jan de Mooij [:jandem]]

splice is a very complicated builtin. We probably want to carve out some fast paths with CacheIR based on the number of arguments, for example I think this is called with two arguments and the return value is unused, so we should be able to use a faster VM function for that case.

Comment 2

[Markus Stange [:mstange]]

I've updated the V8 profile link (the previous one had incorrect data because we hadn't turned off inlining) and now the numbers are 2080 vs 739.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

EmberJS has been removed from sp3. Does the issue show up in other tests?

Comment 4

[Markus Stange [:mstange]]

I have not seen Array.prototype.splice show up majorly in profiles of the other sp3 subtests.

Comment 5

[Brian Grinstead [:bgrins]]

For future reference, the ember and ember debug tests can be run at https://6480ea230b807c000893c43c--speedometer-preview.netlify.app/?suites=TodoMVC-Ember,TodoMVC-Ember-Debug#running