JDK-8349549 : Release Note: Removal of sun.rt._sync* Performance Counters
  • Type: Sub-task
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 25
  • Priority: P4
  • Status: Resolved
  • Resolution: Delivered
  • Submitted: 2025-02-06
  • Updated: 2025-03-31
  • Resolved: 2025-03-31
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JDK 25
25Resolved
Description
This release removes old object monitor performance counters, exposed in the `sun.rt._sync*` namespace. These counters were seldom used, and they contributed to performance problems in related VM code. Users who want to track monitor performance are advised to use related JFR events instead. 

The suggested replacements are:
 - `_sync_ContendedLockAttempts`: `JavaMonitorEnter` JFR event
 - `_sync_FutileWakeups`: no replacement
 - `_sync_Parks`: `JavaMonitorWait` JFR event
 - `_sync_Notifications`: `JavaMonitorNotify` JFR event
 - `_sync_Inflations`: `JavaMonitorInflate` JFR event
 - `_sync_Deflations`: `JavaMonitorDeflate` JFR event
 - `_sync_MonExtant`: `JavaMonitorStatistics` JFR event
Comments
I think the process is to mark this closed/delivered and the release note team will get it then.
25-03-2025
Looks good.
19-03-2025
Maybe this looks better in markup but the note looks good to me. Also thank you for adding the replacement JFR events. - Reviewed.
19-03-2025
I think this should be enough for a release note?
18-03-2025