639729 - inline GC mark path

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Comment 1

[Andreas Gal :gal]

Attachment: patch

Comment 2

[Andreas Gal :gal]

This inlines the GC mark path. A single call out is made if the slots are > 0 and we have to mark them. Many objects have no own slots, so we win a bit.

Comment 3

[Andreas Gal :gal]

A couple of the dependencies aren't landed yet, so this probably has to wait a day or two.

Comment 4

[Andreas Gal :gal]

The assert meant to be span <= slots of course. Sorry for that.

Comment 5

[Andreas Gal :gal]

Test case:

var prev = null;
for (var i = 0; i < 1000000; ++i) {
    var next = ({});
    next.prev = prev;
    prev = next;
}
var t = Date.now();
for (var i = 0; i < 100; ++i)
    gc();
print(Date.now() - t);

Without any of the dependencies above and this patch applied:

kahoolawe:src gal$ ./Darwin_OPT.OBJ/js x.js
5719
kahoolawe:src gal$ ./Darwin_OPT.OBJ/js x.js
5751

With all of the dependencies and this patch applied:

kahoolawe:src gal$ ./Darwin_OPT.OBJ/js x.js
4690
kahoolawe:src gal$ ./Darwin_OPT.OBJ/js x.js
4735

The speedup is around 22%.

To quote Hannibal, I love it when a plan comes together.

Comment 6

[David Mandelin [:dmandelin]]

Does this get a speedup on Windows, too? I would think PGO would totally do this.

Comment 7

[Bill McCloskey [inactive unless it's an emergency] (:billm)]

Comment on attachment 517635 [details] [diff] [review]
patch

Great!

Comment 8

[Andreas Gal :gal]

http://hg.mozilla.org/tracemonkey/rev/518b607a06cd

Comment 9

[Andreas Gal :gal]

Follow-up fix.

http://hg.mozilla.org/tracemonkey/rev/bb2bd286ef22

Comment 10

[Chris Leary [:cdleary] (not checking bugmail)]

http://hg.mozilla.org/mozilla-central/rev/518b607a06cd
http://hg.mozilla.org/mozilla-central/rev/bb2bd286ef22