JDK-8315061 : Make LockingMode a product flag
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 22
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2023-08-25
  • Updated: 2023-10-07
  • Resolved: 2023-08-30
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JDK 22
22 b14Fixed
Related Reports
CSR :  
JDK-8315275 - Make LockingMode a product flag
Relates :  
JDK-8315880 - Change LockingMode default from LM_LEGACY to LM_LIGHTWEIGHT
Relates :  
JDK-8291555 - Implement alternative fast-locking scheme
Relates :  
JDK-8305999 - Add experimental -XX:LockingMode flag
Description
The LockingMode flag from JDK-8291555 was implemented as an
experimental flag. Make it a regular product flag in JDK22 in
preparation for project Lilliput.

In the next release, we plan to change the default of the LockingMode
flag from LM_LEGACY to LM_LIGHTWEIGHT. Project Lilliput needs
the LockingMode flag to be LM_LIGHTWEIGHT. In a release sometime
after the next release, we place to remove support for LM_LEGACY.

Insert additional justification for Lilliput here.
Comments
Changeset: 3eac8905 Author: Daniel D. Daugherty <dcubed@openjdk.org> Date: 2023-08-30 20:20:17 +0000 URL: https://git.openjdk.org/jdk/commit/3eac8905aee6edecbebcc12a41300d3ce176fbff
30-08-2023
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/15496 Date: 2023-08-30 19:36:45 +0000
30-08-2023
In order to change the default LockingMode value from LM_LEGACY to LM_LIGHTWEIGHT, we have to first change LockingMode to a product flag in JDK22 and then in the next release we can change the default LockingMode value from LM_LEGACY to LM_LIGHTWEIGHT. We can't change the default LockingMode value without making LockingMode into a product flag because we have to give customers a supported means of changing the LockingMode should there be any issues with the new default.
30-08-2023
To be honest, I would not make the LockingMode flag a product flag. This has never been my intention. I’d probably change the default to the new lightweight locking, in preparation for Lilliput, but it is not necessary. It would give the new locking some advance exposure, which might be useful.
30-08-2023