JDK-8351146 : JFR: JavaMonitorInflate event should default to no threshold and be disabled
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: jfr
  • Affected Version: 25
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2025-03-04
  • Updated: 2025-03-10
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JDK 25
25Unresolved
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Description
In default/profile configurations for the events we have these:

    <event name="jdk.JavaMonitorInflate">
      <setting name="enabled">false</setting>
      <setting name="stackTrace">true</setting>
      <setting name="threshold" control="locking-threshold">20 ms</setting>
    </event>

There is a threshold for inflate event. But the operation that is covered by that event is very fast, and often lock-free, so the threshold would filter many events. This would be important as we add deflation event (JDK-8351142), which should match inflations.
Comments
Originally, we thought to improve locking thresholds as well: "1. The threshold for enter/wait is too high for practical use. [~coleenp] separately said during related CSR review that 5ms is more practical value: https://bugs.openjdk.org/browse/JDK-8348833?focusedId=14744853#comment-14744853 -- I think we should trim those down to say 1ms for them to be useful by default." Erik suggests to leave that part out, because the rate-limited sampling would likely do better here: https://github.com/openjdk/jdk/pull/23891#issuecomment-2699108603 So this RFE is repurposed to only deal with JavaMonitorInflate threshold.
06-03-2025

A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk/pull/23891 Date: 2025-03-04 11:03:03 +0000
04-03-2025