RFR: [6904367]: (coll) IdentityHashMap is resized before exceeding the expected maximum size

[Jeff Hain]

On 07/08/2014 10:07 PM, Martin Buchholz wrote:
> I updated my webrev and it is again "feature-complete".
> http://cr.openjdk.java.net/~martin/webrevs/openjdk9/IdentityHashMap-capacity/
> <http://cr.openjdk.java.net/%7Emartin/webrevs/openjdk9/IdentityHashMap-capacity/>
> (old webrev at
> http://cr.openjdk.java.net/~martin/webrevs/openjdk9/IdentityHashMap-capacity.0/
> <http://cr.openjdk.java.net/%7Emartin/webrevs/openjdk9/IdentityHashMap-capacity.0/>
> )

The additional loop hurts in my benchmarks (10-15 percents slower).
If removing it and adding a specific putAfterResize() method (without the
"item == k" test), replacing "continue" with "return putAfterResize(k, value)",
it's much better.

NB: In one bench I clear the map each time it hits 1000 mappings,
so that it always fit in some cache, which is about 4 times faster
than going up to 1000*1000 mappings (clear() cost included), and
make put internals costs variations more obvious (hopefully).

-Jeff