RFR: 8271195: Use largest available large page size smaller than LargePageSizeInBytes when available [v8]

[Swati Sharma]

> Hi Team,
> 
> In this patch I have fixed two issues related to large pages, following is the summary of changes :-
> 
> 1. Patch fixes existing large page allocation functionality where if a commit over 1GB pages fails allocation should happen over next small page size i.e. 2M where as currently its happening over 4kb pages resulting into significant TLB miss penalty.
> Patch includes new JTREG Test case covering various scenarios for checking the correct explicit page allocation according ​to the 1G, 2M, 4K priority.
> 2. While attempting commit over larger pages we first try to reserve requested bytes over the virtual address space, in case commit to large page fails we should be un reserving entire reservation to avoid leaving any leaks in virtual address space.
> 
> ​
> Please find below the performance data with and without patch for the JMH benchmark included with the patch.
> 
> ![image](https://user-images.githubusercontent.com/96874289/152189587-4822a4ca-f5e2-4621-b405-0da941485143.png)
> 
> 
> Please review and provide your valuable comments.
> 
> 
> 
> Thanks,
> Swati Sharma
> Runtime Software Development Engineer 
> Intel

Swati Sharma has updated the pull request incrementally with one additional commit since the last revision:

  8271195: Review comments resolved.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7326/files
  - new: https://git.openjdk.java.net/jdk/pull/7326/files/069cca92..f0e9d901

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7326&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7326&range=06-07

  Stats: 29 lines in 3 files changed: 0 ins; 3 del; 26 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7326.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7326/head:pull/7326

PR: https://git.openjdk.java.net/jdk/pull/7326