RFR: JDK-8260200: optimize FreeRegionList::remove_starting_at by removing u…

[Hamlin Li]

optimize FreeRegionList::remove_starting_at by removing unnecessary reading and setting

FreeRegionList::remove_starting_at(...) traverses from a node and removes subsequent N nodes from free list. But when traverses the free list, it removes nodes one by one by setting the prev and next pointers of prev and next node. it's not necessary do these settings for every node, as we can remove target nodes at once and just set prev and next pointers for just 2 nodes.

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

Commit messages:
 - JDK-8260200 optimize FreeRegionList::remove_starting_at by removing unnecessary reading and setting

Changes: https://git.openjdk.java.net/jdk/pull/2181/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2181&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260200
  Stats: 44 lines in 1 file changed: 28 ins; 15 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2181.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2181/head:pull/2181

PR: https://git.openjdk.java.net/jdk/pull/2181