Skip to content

CAUTION: This site hosts draft documentation for the next release. For published content of the latest release, visit


Specifies the number of low-priority background threads that are attached to assist the mutator threads in concurrent mark operations. This option maps directly to the HotSpot -XX:ParallelCMSThreads=N and -XX:ConcGCThreads=N options.



Default behavior

The default value is 1.

Note: This value is reported in the header section of a verbose GC log with the entry <attribute name="gcthreads Concurrent Mark" value="1" />.

This option is not supported with the balanced GC policy (-Xgcpolicy:balanced) or metronome GC policy (-Xgcpolicy:metronome).

See also