Integrated: 8271195: Use largest available large page size smaller than LargePageSizeInBytes when available

[Swati Sharma]

On Wed, 2 Feb 2022 15:58:53 GMT, Swati Sharma <duke at openjdk.java.net> wrote:

> 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

This pull request has now been integrated.

Changeset: 08cadb47
Author:    Swati Sharma <swati.sharma at intel.com>
Committer: Jatin Bhateja <jbhateja at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/08cadb4754da0d5e68ee2df45f4098d203d14115
Stats:     109 lines in 3 files changed: 87 ins; 14 del; 8 mod

8271195: Use largest available large page size smaller than LargePageSizeInBytes when available

Co-authored-by: Jatin Bhateja <jbhateja at openjdk.org>
Reviewed-by: ayang, tschatzl

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

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