1779378 - Avoid unnecessary tenuring via PropertyIteratorObject

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[Jan de Mooij [:jandem]]

PropertyIteratorObject is always tenured. Because we don't null out NativeIterator::objectBeingIterated_ for inactive iterators, we can end up tenuring objects that should be dead.

This happens a fair amount on the matrix-react benchmark.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1779378 part 1 - Add IsEmptyIteratorSingleton flag. r?jonco!

In isEmptyIteratorSingleton() we currently check whether objectBeingIterated == nullptr,
but once we clear this object for inactive iterators this would be a bit confusing and
error-prone.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1779378 part 2 - Clear NativeIterator::objectBeingIterated_ when closing the iterator. r?jonco!

Property iterator objects are always tenured, so this avoids "leaking" the object
via the post-barrier.

Depends on D151705

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c8f77075a0e5
part 1 - Add IsEmptyIteratorSingleton flag. r=jonco
https://hg.mozilla.org/integration/autoland/rev/76d4db257788
part 2 - Clear NativeIterator::objectBeingIterated_ when closing the iterator. r=jonco

Comment 4

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/c8f77075a0e5
https://hg.mozilla.org/mozilla-central/rev/76d4db257788