715541 - Figure out how to optimize out DOM tree traversing when tree is kept alive by non-black JS

Status: RESOLVED WORKSFORME

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

Description

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

Attachment: test

The test case doesn't create exactly the same CC graph what ehsan had in his log, but
still somewhat similar. Basically some JS is kept alive by C++ objects, but since the
JS is marked as gray by GC, CC can't optimize out traversing.

Graph: http://mozilla.pettay.fi/d.svg
Zoom in and look at the top right corner. There is a XPCVariant

I think this is similar to the case jst mentioned where Google Reader keeps window objects
alive (that window could then cause a document to be traversed).

(Note this is a case where strong parent node doesn't affect to graph size in any way)

Comment 1

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

I have a patch which fixes the testcase, but there are of course other similar cases which
can cause problems.

Comment 2

[Andrew McCreight [:mccr8]]

I think this is fixed now, by the black-bit-propogation stuff Olli did.