1873768 - Creating JS wrappers for DOM nodes (e.g. when accessing nextSibling) is slower than in Safari

Status: NEW

(Core :: JavaScript Engine, enhancement, P3)

Description

[Markus Stange [:mstange]]

Attachment: testcase

Steps to reproduce:

1. In the attached testcase, click the buttons in the following order: iterate, iterate, setprop, iterate, iterate

Firefox:
iterate: 75ms
iterate: 75ms
setprop: 70ms
iterate: 55ms
iterate: 52ms

Safari:
iterate: 12ms
iterate: 9ms
setprop: 11ms
iterate: 10ms
iterate: 11ms

Comment 1

[Iain Ireland [:iain]]

I don't think this is the primary difference, but I notice that we are spending a lot of time in LookupStdName, which does a linear scan through a reasonably long list of prototypes. I wonder if a binary search would be faster there.

Comment 2

[Matthew Gaudet (he/him) [:mgaudet]]

Profile from a mozregression launched build.

https://share.firefox.dev/3DpjCtW

Puts 70% of time in LinkedList::asT, called from IncrementalFinalizeRunnable::ReleaseNow

O.o