Document the magic JVM flag to reduce CPU contention etc

performancecopilot / parfait

A Java performance monitoring library, exposing and collecting metrics through a variety of outputs

https://pcp.io

Apache License 2.0

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Document the magic JVM flag to reduce CPU contention etc #10

Closed tallpsmith closed 1 week ago

tallpsmith commented 9 years ago

This issue stems from the discovery many moons ago that for older Java+Linux Kernal combinations some of the Thread CPU metric collections were INSANELY SLOW.

To work around this, an evilly hidden JVM option was discovered: -XX:+UseLinuxPosixThreadCPUClocks

Which when active, drastically improved performance.

myllynen commented 6 years ago

Since the option is enabled by default on OpenJDK 1.7+ perhaps this issue can be closed?

pwinckles commented 1 week ago

The flag has been on by default since java 7 and is now deprecated for removal.

https://bugs.openjdk.org/browse/JDK-8338947