Parallel Collector Stops Application for Minor/Major GC

Java 8 GC Tutorials - Herong's Tutorial Examples

∟Parallel Collector - "+XX:+UseParallelGC"

∟Parallel Collector Stops Application for Minor/Major GC

This section provides log messages showing that the Parallel Collector stops the application for both Minor GC and Major GC.

The next thing we confirm is stop-the-world behavior of the Parallel Collector. This can be verified with "-XX:+PrintGCApplicationStoppedTime" and "-XX:+PrintGCApplicationConcurrentTime" JVM options:

herong> \progra~1\java\jdk1.8.0\bin\java -Xms2m -Xmx64m -XX:+UseParallelGC \
   -XX:+PrintGCDetails -XX:+PrintGCTimeStamps \
   -XX:+PrintGCApplicationStoppedTime \
   -XX:+PrintGCApplicationConcurrentTime \
   GarbageCollection > output.txt
(Ctrl-C)

herong> more output.txt
Step/TotalMemory/FreeMemory/UsedMemory:

0.735: Application time: 0.1749388 seconds
0.736: [GC (Allocation Failure) [PSYoungGen: 511K->248K(768K)] 1280...
0.740: [Full GC (Ergonomics) [PSYoungGen: 248K->238K(768K)] [ParOld...
0.755: Total time for which application threads were stopped:
   0.0197849 seconds, Stopping threads took: 0.0000875 seconds

1   3145728   1821016   1324712

1.760: Application time: 1.0048803 seconds
1.760: [GC (Allocation Failure) [PSYoungGen: 748K->248K(768K)] 2189...
1.768: [Full GC (Ergonomics) [PSYoungGen: 248K->0K(768K)] [ParOldGe...
1.786: Total time for which application threads were stopped:
   0.0255083 seconds, Stopping threads took: 0.0001301 seconds

2   5505024   3124776   2380248

2.776: Application time: 0.9903883 seconds
2.776: [GC (Allocation Failure) [PSYoungGen: 474K->224K(768K)] 3156...
2.783: Total time for which application threads were stopped:
   0.0064196 seconds, Stopping threads took: 0.0001250 seconds

3   5505024   2045928   3459096

3.791: Application time: 1.0084043 seconds
3.791: [GC (Allocation Failure) [PSYoungGen: 695K->240K(1024K)] 414...
3.798: Total time for which application threads were stopped:
   0.0065890 seconds, Stopping threads took: 0.0001242 seconds
...

As we can see from the output:

The application were stopped for 4 times within the first 4 seconds.
This first stop lasted for 0.0197849 seconds for a combination of minor and major GCs.
This second stop lasted for 0.0255083 seconds for a combination of minor and major GCs.
This third stop lasted for 0.0064196 seconds for minor GC only.
This forth stop lasted for 0.0065890 seconds for a minor GC only.