JDK-8277137 : Set OnSpinWaitInst/OnSpinWaitInstCount defaults to "isb"/1 for Arm Neoverse N1
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 17,18
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • CPU: aarch64
  • Submitted: 2021-11-15
  • Updated: 2022-12-16
  • Resolved: 2021-11-18
The Version table provides details related to the release that this issue/RFE will be addressed.

Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

To download the current JDK release, click here.
JDK 17 JDK 18
17.0.3Fixed 18 b25Fixed
Related Reports
Duplicate :  
JDK-8258604 - Use 'isb' instruction in SpinPause on linux-aarch64
Relates :  
JDK-8277503 - compiler/onSpinWait/TestOnSpinWaitAArch64DefaultFlags.java failed with "OnSpinWaitInst with the expected value 'isb' not found."
Relates :  
JDK-8186670 - Implement _onSpinWait() intrinsic for AArch64
Description
According to perf data, setting OnSpinWaitInst/OnSpinWaitInstCount to "isb"/1 improves performance workloads on Graviton 2(Arm Neoverse N1 implementation) which use Thread.onSpinWait. See https://git.openjdk.java.net/jdk/pull/5562 for details. So they should be used as defaults on Arm Neoverse N1.
Comments
@Goetz, done: https://github.com/openjdk/jdk17u-dev/pull/107
19-01-2022
@Evgeny, please backport 8277503 as dependent pull request, so you can push them at the same time. You must craft the PR on top of branch pr/103.
18-01-2022
A pull request was submitted for review. URL: https://git.openjdk.java.net/jdk17u-dev/pull/103 Date: 2022-01-18 19:45:42 +0000
18-01-2022
Fix Request (17u) Default implementation of spin waits for Neoverse N1.Applies cleanly. JDK-8277503 will be backported to fix a test failure.
18-01-2022
Changeset: 38345bd2 Author: Evgeny Astigeevich <eastig@amazon.com> Committer: Volker Simonis <simonis@openjdk.org> Date: 2021-11-18 11:18:15 +0000 URL: https://git.openjdk.java.net/jdk/commit/38345bd28db83371676f1685806ddc207a833879
18-11-2021