[jdk21u-dev] Integrated: 8313319: [linux] mmap should use MAP_FIXED_NOREPLACE if available

[Sergey Chernyshev]

On Fri, 14 Nov 2025 17:47:07 GMT, Sergey Chernyshev <schernyshev at openjdk.org> wrote:

> Hi all,
> 
> Please review the backport of JDK-8313319 that prevents unnecessary mmap-munmap cycle in systems that do not honor the address hint when mmapping memory without MAP_FIXED. Please see more details in #2475. ~~This is (almost) a clean backport, with only a minor context conflict due to JDK-8315923 hasn't been backported to JDK 21.~~
> 
> UPD: Apart from a minor context issue related to JDK-8315923, there was a second definition of MAP_FIXED_NOREPLACE, introduced by [JDK-8330520](https://github.com/openjdk/jdk21u/commit/fee209491beb07c09119a81c78d86d455c79c58b) backport.
> 
> Testing:
> 
> - jtreg standard test groups passed
> - gtests passed (aarch64 & amd64)

This pull request has now been integrated.

Changeset: b17eef0f
Author:    Sergey Chernyshev <schernyshev at openjdk.org>
Committer: Thomas Stuefe <stuefe at openjdk.org>
URL:       https://git.openjdk.org/jdk21u-dev/commit/b17eef0fb5a8af20b520157ca1ec52d601b6746b
Stats:     39 lines in 2 files changed: 37 ins; 0 del; 2 mod

8313319: [linux] mmap should use MAP_FIXED_NOREPLACE if available

Reviewed-by: stuefe
Backport-of: 3699666c9325b38d287e1d4d2576f8e3a662ae81

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PR: https://git.openjdk.org/jdk21u-dev/pull/2476