186193 2018-06-01 06:33:10 -0700 [JSC] NewArrayBuffer should have non-CoW mode 2018-06-19 07:01:45 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Nightly Build Unspecified Unspecified NEW P2 Normal --- 186724 1 ysuzuki webkit-unassigned fpizlo keith_miller mark.lam msaboff saam ysuzuki oldest_to_newest 1429205 0 ysuzuki 2018-06-01 06:33:10 -0700 In some program, array created by new_array_buffer is not immutable (I think Kraken/crypto-aes and SixSpeed spread-literal.es5 are). But ArrayifyToStructure's array copying is really slow compared to non CoW array creation in NewArrayBuffer. I think we should have non-CoW mode for NewArrayBuffer / new_array_buffer. ArrayAllocationProfile should carefully profile the use of resulted array, and tell us whether using CoW mode is profitable. 1429232 1 saam 2018-06-01 08:55:24 -0700 Why is arrayify to structure slow? 1429357 2 keith_miller 2018-06-01 14:10:27 -0700 It seems like if this is a problem the fix is to make Arrayification faster. Since the total amount of work duplicating the butterfly should be the same either way, I don't see any obvious reason to eagerly copy.