Question on Shenandoah GarbageCollectorMXBeans

Michael Nitschinger michael at
Thu Nov 8 09:55:07 UTC 2018


I’ve been trying to get GC information through the GarbageCollectorMXBean instances and it is working great so far, although I have a couple of questions. I couldn’t find any documentation on this topic, so sorry if it is written up somewhere.

I’m adding my NotificationListener to the MXBeans returned by the ManagementFactory with shenandoah enabled and:

when I’m looking at the “cause” of the GarbageCollectionNotificationInfo it always says “No GC” which seems weird to me (both for the Pauses and the Cycles bean) - even that the action contains messages like “end of major GC” or “end of minor GC".
In terms of “action”, Shenandoah Pauses always seems to return “end of major GC” while Shenandoah Cycles returns “end of minor GC”, but is that really accurate? There seems to be only one “shenandoah” memory pool and while the Cycles info has memory usage attached to it, the Pauses one has no memory information whatsoever (all values are zeroed out).

I’m running on 1.8.0_181-b15 that ships with fedora and the only JVM flag that I set was -XX:+UseShenandoahGC.

Happy to provide more information if required,

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