RFR: 8236847: CDS archive with 4K alignment unusable on machines with 64k pages [v8]

[Yumin Qi]

> Hi, Please review
>   Usually most OSes are configured with page size of 4K, but some others are configured with 64K. If jdk binary is built on 4K platform and run on different configured platforms, CDS fails to be loaded due to region alignment mismatch:
>   Unable to map CDS archive -- os::vm_allocation_granularity() expected: 4096 actual: 65536
>   This change uses 64K as region alignment if OS page size is less than 64K. For most of the current OSes, means always use 64K as file map region alignment.
>    The archive size will increase about 300K due to the change. 
>    Tests: tier1-4
>               Run MacOS/X64 binary on MacOS/aarch64 
> 
>    Thanks
>    Yumin

Yumin Qi has updated the pull request incrementally with one additional commit since the last revision:

  Fix core region alignment for macosx-x64 and comment

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2651/files
  - new: https://git.openjdk.java.net/jdk/pull/2651/files/b717055a..d7591634

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2651&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2651&range=06-07

  Stats: 4 lines in 2 files changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2651.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2651/head:pull/2651

PR: https://git.openjdk.java.net/jdk/pull/2651