280144 2024-09-21 22:43:12 -0700 Deleting existing entry from Map/Set followed by re-adding is 30x slower than in v8 2024-09-29 22:42:19 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Local Build Mac (Apple Silicon) macOS 14 RESOLVED DUPLICATE 280600 InRadar P2 Normal --- 1 dylan.conway567 webkit-unassigned webkit-bug-importer ysuzuki oldest_to_newest 2062164 0 dylan.conway567 2024-09-21 22:43:12 -0700 Example minified from https://github.com/oven-sh/bun/issues/14063 ``` var map = new Set(); for (var i = 0; i < 1000; i++) { for (var j = 0; j < 1000; j++) { map.delete(j); map.add(j); } } ``` Running this on an m1 max takes about 1 second with JSC. With v8 it takes about 100 milliseconds. Switching the order of `delete` and `add`, or combining the loops into a single loop to 1000000 does not seem to repro this behavior. 2062971 1 dylan.conway567 2024-09-25 01:07:48 -0700 I suspect this is a bug causing the table to resize too frequently. Removing `shrinkIfNeeded` in `OrderedHashTableHelper::removeImpl` almost brings performance back to normal 2064065 2 webkit-bug-importer 2024-09-28 22:44:18 -0700 <rdar://problem/136912759> 2064159 3 ysuzuki 2024-09-29 22:42:19 -0700 Thanks. Oops, I accidentally opened a new bugzilla for patch upload. Merging it to that as it already has GitHub link. *** This bug has been marked as a duplicate of bug 280600 ***