Parallel Collector Stops Application for Minor/Major GC

Java 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 want to confirm is stop-the-world behavior of the Parallel Collector. There seems to be no easy way to do this in JVM 9 or higher releases. I could not find any "-Xlog" options to generate any log messages about when and for how long application gets stopped by the Parallel Collector.

But if you are still using JVM 8 or older releases, you can confirm stop-the-world behavior of the Parallel Collector 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

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 (Full GCs).
This second stop lasted for 0.0255083 seconds for a combination of minor and major GCs (Full 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.
Application stopped a longer period of time for Full GCs than Minor GCs.