JDK-8303210 : [linux, Windows] Make UseSystemMemoryBarrier available as product flag
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 21
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: linux,windows
  • Submitted: 2023-02-25
  • Updated: 2024-05-16
  • Resolved: 2023-04-03
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JDK 21
21 b17Fixed
Related Reports
CSR :  
JDK-8303500 - Make UseSystemMemoryBarrier available as product flag
Relates :  
JDK-8292591 - Experimentally add back barrier-less Java thread transitions
Relates :  
JDK-8289302 - Restore CriticalJNINatives
Description
JDK-8292591 has introduced System Memory Barriers for linux and Windows as experimental feature (released with JDK20). It has been extended by JDK-8293922 and tested on x86_64, aarch64 and PPC64le since September 2022 and there are no known issues.

Explanation and performance results were reported here: https://github.com/openjdk/jdk/pull/10123#issuecomment-1235123012
I originally wanted to enable the feature by default for JDK21, but startup performance is impacted and some benchmarks on some platforms as well (see PR below). So, I only want to make it available as product flag, now.

JFR users who use a very high sampling rate may notice a performance penalty of the System Memory Barrier calls. The feature can get switched off in this case by -XX:-UseSystemMemoryBarrier.

Note: The feature requires at least Linux 4.14. The flag needs to be off for older versions.
Comments
Changeset: 4de24cdb Author: Martin Doerr <mdoerr@openjdk.org> Date: 2023-04-03 09:37:16 +0000 URL: https://git.openjdk.org/jdk/commit/4de24cdbe65289bd99eace30399f20694441f0aa
03-04-2023
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/12753 Date: 2023-02-25 09:17:57 +0000
25-02-2023