Parallel New (ParNew) Collector for Minor GC

This section demonstrates that the '-XX:+UseConcMarkSweepGC' JVM option invokes the Parallel New (ParNew) collector for Young generation GC.

In previous tutorials, we learned that the "-XX:+UseConcMarkSweepGC" JVM option invokes the "Parallel New (ParNew)" collector for Young generation GC and "Concurrent Mark-Sweep (CMS)" collector to Tenured generation GC.

In this tutorial, let's run our test with plenty of Young generation memory to see how ParNew collector works.

C:\herong>java -Xms2m -Xmx64m -XX:+UseConcMarkSweepGC -Xms1200m -Xmx1200m
   -XX:NewRatio=1 -XX:SurvivorRatio=1 -Xlog:gc,gc+heap=info
   GarbageCollection > output.txt

C:\herong>type output.txt
[info ][gc     ] Using Concurrent Mark Sweep
Step/TotalMemory/FreeMemory/UsedMemory:
1   1048576000   1040187352   8388648

...
185   1048576000   838860800   209715200
[info ][gc,heap] GC(0) ParNew: 204800K->34034K(409600K)
[info ][gc,heap] GC(0) CMS: 0K->0K(614400K)
[info ][gc     ] GC(0) Pause Young (Allocation Failure)
                       200M->33M(1000M) 14.555ms
...
372   1048576000   804009288   244566712
[info ][gc,heap] GC(1) ParNew: 238834K->37404K(409600K)
[info ][gc,heap] GC(1) CMS: 0K->0K(614400K)
[info ][gc     ] GC(1) Pause Young (Allocation Failure)
                       233M->36M(1000M) 11.900ms
...
9874   1048576000   781730152   266845848
[info ][gc,heap] GC(51) ParNew: 259751K->61818K(409600K)
[info ][gc,heap] GC(51) CMS: 840K->840K(614400K)
[info ][gc     ] GC(51) Pause Young (Allocation Failure)
                        254M->61M(1000M) 7.055ms

The output confirms that:

Table of Contents

 About This Book

 Heap Memory Area and Size Control

 JVM Garbage Collection Logging

 Introduction of Garbage Collectors

 Serial Collector - "+XX:+UseSerialGC"

 Parallel Collector - "+XX:+UseParallelGC"

Concurrent Mark-Sweep (CMS) Collector - "+XX:+UseConcMarkSweepGC"

 What Is Concurrent Mark-Sweep (CMS) Collector

 Concurrent Mark-Sweep Collector GC Log Message Format

 Reduce Stop-The-World with Concurrent Mark and Sweep

Parallel New (ParNew) Collector for Minor GC

 ParNew Collector - Tenuring Age Distribution

 Maximium Logging of All Phases on Young GC

 "-XX:ParallelGCThreads=6" - Young GC Parallel Threads

 "-XX:MaxTenuringThreshold=0" - Tenuring Objects Immediately

 "-XX:CMSInitiatingOccupancyFraction=20" - Initiate CMS

 Maximium Logging of All Phases on Old GC

 Maximium Logging of All Phases on Full GC

 "-XX:ParallelGCThreads=6" - Old GC Parallel Threads

 "-XX:ConcGCThreads=3" - Old GC Concurrent Threads

 Garbage First (G1) Collector - "+XX:+UseG1GC"

 The Z Garbage Collector (ZGC) - "+XX:+UseZGC"

 Object References and Garbage Collection

 Garbage Collection Performance Test Program

 Performance Tests on Serial Collector

 Performance Tests on Parallel collector

 Performance Tests on Concurrent collector

 Performance Tests on G1 collector

 Garbage Collection Performance Test Summary

 References

 Full Version in PDF/EPUB