Parallel collector

The parallel collector (or throughput collector) uses the parallel version of the young generation collector.

NOTE:

To enable the appropriate GC, use the "+" option. To disable the appropriate GC, use the "—" option.

The following are the valid java command options, that specify or apply to a parallel collector:

-XX:+UseParallelGC

This option enables parallel scavenge for the young generation.

NOTE:

The default GC is the serial GC.

-XX:+UseParallelOldGC

This option enables parallel GC for the old generation. This option automatically enables parallel scavenge (for young generation).

-XX:+UseAdaptiveSizePolicy

This option enables adaptive size policy for the Java heap. By default, this option is disabled in NSJ. However, if the parallel GC is enabled, this option is enabled automatically unless it is disabled it in the command-line.

NOTE:

AdaptiveSizePolicy on NSJ considers only the throughput and pause time goal. The footprint goal is not considered.

-XX:+AggressiveHeap

Obtains the platform resources and configures the heap layout accordingly, uses parallel collector, and enables AdaptiveSizePolicy option. -XX:+AggressiveHeap option is not supported in NSJ. However, if you specify this option the JVM exits with the error:

—XX:+AggressiveHeap option is not supported on this platform.

-XX:MaxGCPauseMillis

Sets a value for a desired pause time. The default value is 200 milliseconds.

–XX:ParallelGCThreads=<n>

This option is used to specify the number of parallel GC threads for the parallel garbage collection. The default number of GC threads created is equal to the number of cores present in the processor. If a value greater than the number of cores is specified, the following warning is displayed and the application continues to run:

WARNING:

Parallel GC thread count (<n>) cannot be greater than the number of cores (<numcore>) in a CPU. Using <numcore> for Parallel GC count.