1917511 - Demo takes 3mins to run and spends 2.4mins in nsParentNodeChildContentList::ValidateCache. Chrome runs in 20s

Status: VERIFIED FIXED

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

Description

[Mayank Bansal]

Go to https://highlight.xyz/mint/65758ec0c56a0da366b32ab7

AR: It takes 3 minutes on my machine for the demo to render. Chrome renders in ~20seconds.
Profile: https://share.firefox.dev/4cVkSkp

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[Andreas Farre [:farre]]

This could perhaps be improved by making sure there is capacity in the array in ValidateCache but it didn't seem to matter much. :smaug, your good at perf solutions. Do you have an idea?

Comment 3

[Emilio Cobos Álvarez (:emilio)]

We don't need to update the cache to get the child count...

Comment 4

[Emilio Cobos Álvarez (:emilio)]

    function removeChildNodes() {
      _pathCount = 0;

      while (_svg.childNodes.length > 0) {
        _svg.removeChild(_svg.childNodes[0]);
      }
    }

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1917511 - Improve performance of childNodes. r=smaug

Child count is constant so we don't need the cache. Add a fast path for
uncached first / last node.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8312c5570b7e
Improve performance of childNodes. r=smaug

Comment 7

[Mayank Bansal]

Profile with the autoland build now takes 15 seconds: https://share.firefox.dev/4glRt5O
So we are now faster than Chrome here. Pretty nice!

Comment 9

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/8312c5570b7e

Comment 10

[Mayank Bansal]

And with hte latest Nightly: https://share.firefox.dev/3zlzpIj (15s with the profiler) - I think this 15s is more accurate and represents the demo running rather than the whole pageload.

Comment 11

[Ardelean Oana, Desktop Test Engineering [:oardelean]]

Reproducible on a 2024-09-08 Nightly build on Windows 10.
Verified as fixed on Firefox 132.0b7 and Firefox Nightly 133.0a1 on Windows 10, macOS 14, Ubuntu 22.