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chandlerprall/d8 --harmony_collections --trace_gc --expose_gc

Created April 8, 2014 16:21
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WeakMap values hanging around
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d8 --harmony_collections --trace_gc --expose_gc
wm = new WeakMap();
gc(); // Mark-sweep 2.6 (40.3) -> 2.2 (40.3) MB
// Starting memory usage is 40.3 MB
keys = [];
for ( i = 0; i < 1000000; i++ ) {
var key = {};
keys.push( key );
wm.set( key, true );
}
gc(); // Mark-sweep 105.3 (144.3) -> 105.2 (144.3) MB
// Memory usage with keys + values is 144.3 MB
// Remove keys, let them get collected
keys.length = 0;
gc(); // Mark-sweep 105.2 (144.3) -> 34.2 (77.4) MB
// Keys have been collected, now down to 77.4 MB... which means values are still around
// Force collect the WeakMap
wm = null;
gc(); // Mark-sweep 2.2 (41.3) -> 2.2 (41.3) MB
// Back down to the low 40s
@chandlerprall
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Proper test is to use a real value in the map instead of true, see https://code.google.com/p/v8/issues/detail?can=2&start=0&num=100&q=&colspec=ID%20Type%20Status%20Priority%20Owner%20Summary%20HW%20OS%20Area%20Stars&groupby=&sort=&id=3262

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