304759 - Avoid link map maintenance when tearing down document

Status: RESOLVED FIXED

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

Description

[Robert O'Callahan (:roc) (email my personal email if necessary)]

bz's profile shows the fix for bug 78510 added significant cost when tearing
down documents. In particular, for every link, UnbindFromTree calls ForgetLink
which constructs a new URI for the link, which is expensive.

We can fix this by destroying the link map before calling UnbindFromTree when we
know that all the document's elements are being unbound. Then in ForgetLink we
just check to see if the map is empty before we do anything.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Attachment: fix

This fix appears quite straightforward.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 192872 [details] [diff] [review]
fix

Excellent.  r+sr=bzbarsky if you also fix nsDocument::ReplaceChild (see the
code at
http://lxr.mozilla.org/seamonkey/source/content/base/src/nsDocument.cpp#3640
which removes and unbinds the node and then possibly resets mRootContent; in
the case when it would do this last, you want to clear the link map before
removing and unbinding).

Comment 3

[Robert O'Callahan (:roc) (email my personal email if necessary)]

checked into trunk. Let's look for branch approval once we see the trunk Tp impact.

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Comment on attachment 192872 [details] [diff] [review]
fix

This seems to have reduced the impact of 78510 to almost zero. definitely
should go on the branch.

Comment 5

[jag (Peter Annema)]

WOOT!

Comment 6

[Robert O'Callahan (:roc) (email my personal email if necessary)]

checked in on branch

Comment 7

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

bz's review comment didn't seem to make it into the version checked in to the
branch.

Comment 8

[Robert O'Callahan (:roc) (email my personal email if necessary)]

oops, I'll fix that. Thanks for picking it up!

Comment 9

[Robert O'Callahan (:roc) (email my personal email if necessary)]

checked that in.