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.

This fix appears quite straightforward.

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).

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

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.

WOOT!

checked in on branch

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

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

checked that in.