[jdk21u-dev] RFR: 8334371: [AIX] Beginning with AIX 7.3 TL1 mmap() supports 64K memory pages

[Joachim Kern]

Beginning with AIX 7.3 TL1 mmap() supports 64K memory pages. As an enhancement, during the initialization of the VM the availability of this new feature is examined. If the 64K pages are supported the VM will use mmap() with 64K pages instead of shmget()/shmat() with 64K pages due to the bad 256M alignment of shmget()/shmat().

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Commit messages:
 - Backport ced99066354fc6a32c587b9e3c35b07e26d3452e

Changes: https://git.openjdk.org/jdk21u-dev/pull/1362/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1362&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334371
  Stats: 37 lines in 1 file changed: 25 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1362.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1362/head:pull/1362

PR: https://git.openjdk.org/jdk21u-dev/pull/1362