1001469 - Re-enable cycle collector optimization for nodes in the shadow tree

Status: RESOLVED FIXED

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

Description

[Andrew McCreight [:mccr8]]

Currently, we can't optimize nodes in the shadow tree out of the graph based on whether they are in document, because they can return true for being in document even if they are not owned by the document.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Andrew, looks like this got fixed. Can we fix this now? That flag is definitely not needed anymore in problematicFlags, but should the CC optimization be using GetComposedDoc instead? That should allow to really apply the optimization to shadow trees.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

my first "got fixed" is about the "nodes in shadow trees report to be in the document".

Comment 3

[Andrew McCreight [:mccr8]]

I don't know. Hopefully Olli does.

Comment 4

[Olli Pettay [:smaug][[e-mail]](vacation until Nov 16)]

Using IsInComposedDoc should be fine these days, I think

Comment 5

[Olli Pettay [:smaug][[e-mail]](vacation until Nov 16)]

We may want to change OwnedOnlyByTheDOMTree to make optimizations more effective.

Comment 6

[Olli Pettay [:smaug][[e-mail]](vacation until Nov 16)]

these days host element owns the ShadowRoot 
https://searchfox.org/mozilla-central/rev/3f17a234769d25fca5144ebb8abc8e1cb3c56c16/dom/base/FragmentOrElement.h#210
and ShadowRoot owns the host
https://searchfox.org/mozilla-central/rev/3f17a234769d25fca5144ebb8abc8e1cb3c56c16/dom/base/DocumentFragment.h#107

Comment 7

[Olli Pettay [:smaug][[e-mail]](vacation until Nov 16)]

Attachment: optimize_shadow_dom_in_cc.diff

As explained in the previous comment, Shadow Root is handled sort of like another child node, so this should be fine. But let's see what tryserver thinks.
(manually running wpt shadow DOM tests didn't reveal leaks.)

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Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/99e338bc3709
Re-enable cycle collector optimization for nodes in the shadow tree, r=mccr8

Comment 9

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/99e338bc3709