RFR: 8316493: Make immutable maps @ValueBased [v3]

Per Minborg pminborg at openjdk.org
Thu Sep 21 16:40:59 UTC 2023


> This PR outlines a solution for making immutable maps `@ValueBased` by removing cacheing of certain values in `AbstractMap`.
> 
> By removing these caching fields in `AbstractMap`, we can make the immutable maps `@ValueBased` and at the same time, performance is likely improved because the JVM is probably able to optimize away object creation anyway via escape analysis. Also, all maps will occupy less space as we get rid of a number of objects and references stored for each map.
> 
> We need to benchmark this solution to better understand its implications.

Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Merge branch 'master' into vb-map2
 - Remove redundant impl spec parts
 - Merge pull request #4 from cl4es/HashMapViews
   
   Add simple HashMapViews microbenchmark
 - Add simple HashMapViews microbenchmark
 - Remove caching in AbstractMap and make immutable maps @ValueBased

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15614/files
  - new: https://git.openjdk.org/jdk/pull/15614/files/2cb090b6..18cfff84

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15614&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15614&range=01-02

  Stats: 68207 lines in 2244 files changed: 20382 ins; 12922 del; 34903 mod
  Patch: https://git.openjdk.org/jdk/pull/15614.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15614/head:pull/15614

PR: https://git.openjdk.org/jdk/pull/15614


More information about the core-libs-dev mailing list