Optimize the memory footprint of MapMakerInternalMap entries by special-casing linked entries.
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Optimize the memory footprint of
MapMakerInternalMapentries by special-casing linked entries.The first entry in each bucket does not need a
nextfield because it will only ever be the tail of the bucket's linked list. BecauseMapMakerInternalMapuses a load factor of 0.75, we can expect that most entries are tails, so long as the hash function is good.For the common use case of a weak interner with compressed OOPs, omitting the
nextfield reduces the shallow heap ofWeakKeyDummyValueEntryfrom 40 bytes to 32 bytes.RELNOTES=Memory optimizations for
InternerandMapMaker