JVM Tutorials - Herong's Tutorial Examples

∟Memory Management and Garbage Collectors

∟Parallel Compacting Collector GC Log Message Format

This section provides examples of HotSpot Parallel Compacting Collector GC log messages.

As a comparison, here is an example of log messages generated by the Parallel Compacting Collector: 

C:\>\progra~1\java\jdk1.8.0\bin\java -Xms2m -Xmx64m 
   -XX:+UseParallelOldGC
   -XX:+PrintGCDetails GarbageCollection

Step/TotalMemory/FreeMemory/UsedMemory:

   [GC (Allocation Failure) 
      [PSYoungGen: 450K->240K(768K)] 
      1218K->1092K(1792K), 
      0.0009669 secs] 
   [Times: user=0.00 sys=0.00, real=0.00 secs] 

1   1835008   484272   1350736

   [GC (Allocation Failure) 
      [PSYoungGen: 723K->240K(768K)] 
      2087K->2076K(2816K), 
      0.0030646 secs] 
   [Times: user=0.00 sys=0.00, real=0.00 secs] 

   [Full GC (Ergonomics) 
      [PSYoungGen: 240K->0K(768K)] 
      [ParOldGen: 1836K->2037K(3840K)] 
      2076K->2037K(4608K), 
      [Metaspace: 44K->44K(4480K)], 
      0.0204217 secs] 
   [Times: user=0.03 sys=0.00, real=0.02 secs] 

...

Heap
 PSYoungGen      total 14592K, used 13698K [0x066c0000, 0x07c00000...
  eden space 7424K, 88% used [0x066c0000,0x06d24530,0x06e00000)
  from space 7168K, 99% used [0x06e00000,0x074fc2f0,0x07500000)
  to   space 7168K, 0% used [0x07500000,0x07500000,0x07c00000)
 ParOldGen       total 43776K, used 32610K [0x03c00000, 0x066c0000...
  object space 43776K, 74% used [0x03c00000,0x05bd8ae8,0x066c0000)
 Metaspace used 45K, capacity 2242K, committed 2368K, reserved 4480K

Log message format generated by the Parallel Compacting Collector is identical to the Parallel Collector.

Last update: 2014.

Table of Contents

 About This Book

 Downloading and Installing JDK 1.8.0 on Windows

 Downloading and Installing JDK 1.7.0 on Windows

 java.lang.Runtime Class - The JVM Instance

 java.lang.System Class - The Operating System

 ClassLoader Class - Class Loaders

 Class Class - Class Reflections

 Sun's JVM - Java HotSpot VM

 JRockit JVM 28.2.7 by Oracle Corporation

 JVM Runtime Data Areas

►Memory Management and Garbage Collectors

 Memory Management General Rules

 Java Exception: "java.lang.OutOfMemoryError: Java heap space"

 OutOfMemoryError Comparison of HotSpot and JRockit

 Garbage Collection Demonstration

 JVM Memory Manager - Garbage Collector

 Generational Garbage Collection in HotSpot

 Young Generation Collection - Minor Collection

 Tenured Generation Collection - Full Collection

 HotSpot Default Garbage Collector - Serial Collector

 "-XX:+PrintGCDetails" - Garbage Collection Logging

 GC Log Messages on GarbageCollection.java

 Serial, Parallel, Concurrent, and Regionalized Collectors

 Parallel Collector GC Log Message Format

►Parallel Compacting Collector GC Log Message Format

 Concurrent Mark-Sweep Collector GC Log Message Format

 Garbage First GC Log Message Format

 Garbage Collection Tests

 JVM Stack, Frame and Stack Overflow

 Thread Testing Program and Result

 CPU Impact of Multi-Thread Applications

 I/O Impact of Multi-Thread Applications

 CDS (Class Data Sharing)

 Micro Benchmark Runner and JVM Options

 Micro Benchmark Tests on "int" Operations

 Micro Benchmark Tests on "long" Operations

 Micro Benchmark Tests in JIT Compilation Mode

 Micro Benchmark Tests on "float" and "double" Operations

 Outdated Tutorials

 References

 PDF Printing Version