RFR: 8324573: HashMap::putAll should resize to sum of both map sizes [v2]

[Joshua Cao]

> This change mirrors what we did for ConcurrentHashMap in https://github.com/openjdk/jdk/pull/17116. When we add all entries from one map to anther, we should resize that map to the size of the sum of both maps.
> 
> I used the command below to run the benchmarks. I set a high heap to reduce garbage collection noise.
> 
> java -Xms25G -jar benchmarks.jar -p size=100000 -p addSize=100000 -gc true org.openjdk.bench.java.util.HashMapBench
> 
> 
> Before change
> 
> 
> Benchmark            (addSize)        (mapType)  (size)  Mode  Cnt   Score   Error  Units
> HashMapBench.putAll     100000         HASH_MAP  100000  avgt    4  22.927 ± 3.170  ms/op
> HashMapBench.putAll     100000  LINKED_HASH_MAP  100000  avgt    4  25.198 ± 2.189  ms/op
> 
> 
> After change
> 
> 
> Benchmark            (addSize)        (mapType)  (size)  Mode  Cnt   Score   Error  Units
> HashMapBench.putAll     100000         HASH_MAP  100000  avgt    4  16.780 ± 0.526  ms/op
> HashMapBench.putAll     100000  LINKED_HASH_MAP  100000  avgt    4  19.721 ± 0.349  ms/op
> 
> 
> We see about average time improvements of 26% in HashMap and 20% in LinkedHashMap.

Joshua Cao has updated the pull request incrementally with one additional commit since the last revision:

  Add benchmark with all duplicate keys

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/17544/files
  - new: https://git.openjdk.org/jdk/pull/17544/files/d1ad90cd..a74c10da

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17544&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17544&range=00-01

  Stats: 14 lines in 1 file changed: 14 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17544.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17544/head:pull/17544

PR: https://git.openjdk.org/jdk/pull/17544