504033 - avoiding calling JSFinalizeStub.

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[Igor Bukanov]

+++ This bug was initially created as a clone of Bug #503461 comment 4 +++

When finalizing the objects we are always calling the finalization hook:

static void
js_FinalizeObject(JSContext *cx, JSObject *obj)
{
...
    /* Finalize obj first, in case it needs map and slots. */
    STOBJ_GET_CLASS(obj)->finalize(cx, obj);

For the default objects and arrays the finalization hook is the empty JSFinalizeStub method. We should investigate if avoiding this call via simple check for the sub method can speedup things.

Comment 1

[Igor Bukanov]

Attachment: v1

The patch allows to use null in place of JSFinalizeStub. This speed ups the GC phase of the following test case by about 1%:

function test()
{
    var array = [];
    for (var j = 0; j != 12; ++j) {
        var array2 = [];
        for (var i = 0; i != 1e5; ++i) {
            array2.push({});
        }
        array.push(array2);
    }
    return array;
}

test();
var t = Date.now();
gc();
print(Date.now() - t);

Comment 2

[Igor Bukanov]

http://hg.mozilla.org/tracemonkey/rev/f79e027c3fb1

Comment 3

[Robert Sayre]

http://hg.mozilla.org/mozilla-central/rev/f79e027c3fb1