JVM Tutorials - Herong's Tutorial Examples

∟Garbage Collection Tests

∟441/400/40MB Test on JRockit 28.2

This section provides a tutorial example on running GCTest2.java on JRockit 28.2.7 with 441MB memory limit and a 400MB base plus 40MB fluctuating memory usage with object size of 1.25MB. 1 extra MB is enough for the GC to work.

From the previous tutorial, we learned that JRockit GC behaves better than HotSpot with low free memory. In this tutorial, I want to how low it can go with HotSpot R28.2.7 on my Windows 7 system: 

>\Progra~1\java\jrockit-jdk1.6.0_45-R28.2.7-4.1.0\bin\javac 
   GCTest2.java

>\Progra~1\java\jrockit-jdk1.6.0_45-R28.2.7-4.1.0\bin\java 
   -Xmx441m GCTest2
Test parameters:
   Object size: 1280KB
   Initial objects and data size: 320, 409600KB
   Added objects and data size: 32, 40960KB
Time  Total  Free   Used  Free  Total    Act.  Dead  Over
sec.   Mem.  Mem.   Mem.    %.   Obj.    Obj.  Obj.  Head
  1  451584   790  450794  0%  450560  409600  40960  234
  3  451584   790  450794  0%  450560  409600  40960  234
  4  451584   790  450794  0%  450560  409600  40960  234
  5  451584   792  450792  0%  450560  409600  40960  232
  6  451584   792  450792  0%  450560  409600  40960  232
  7  451584   792  450792  0%  450560  409600  40960  232
  8  451584   792  450792  0%  450560  409600  40960  232
 10  451584   792  450792  0%  450560  409600  40960  232
 11  451584   792  450792  0%  450560  409600  40960  232
 12  451584   790  450794  0%  450560  409600  40960  234
 13  451584   790  450794  0%  450560  409600  40960  234
 14  451584   791  450793  0%  450560  409600  40960  233
 15  451584   790  450794  0%  450560  409600  40960  234
 17  451584   790  450794  0%  450560  409600  40960  234
 18  451584   792  450792  0%  450560  409600  40960  232
 19  451584   792  450792  0%  450560  409600  40960  232
 20  451584   790  450794  0%  450560  409600  40960  234
 21  451584   790  450794  0%  450560  409600  40960  234
 23  451584   790  450794  0%  450560  409600  40960  234
 24  451584   792  450792  0%  450560  409600  40960  232
 25  451584   790  450794  0%  450560  409600  40960  234
 26  451584   790  450794  0%  450560  409600  40960  234
 27  451584   791  450793  0%  450560  409600  40960  233
 29  451584   790  450794  0%  450560  409600  40960  234
 30  451584   790  450794  0%  450560  409600  40960  234
 31  451584   792  450792  0%  450560  409600  40960  232
 32  451584   792  450792  0%  450560  409600  40960  232
 33  451584   790  450794  0%  450560  409600  40960  234
 35  451584   790  450794  0%  450560  409600  40960  234
 36  451584   792  450792  0%  450560  409600  40960  232
 37  451584   792  450792  0%  450560  409600  40960  232
 38  451584   790  450794  0%  450560  409600  40960  234
 39  451584   790  450794  0%  450560  409600  40960  234
 41  451584   792  450792  0%  450560  409600  40960  232
 42  451584   790  450794  0%  450560  409600  40960  234
 43  451584   790  450794  0%  450560  409600  40960  234
 44  451584   792  450792  0%  450560  409600  40960  232
 45  451584   792  450792  0%  450560  409600  40960  232
 47  451584   790  450794  0%  450560  409600  40960  234
 48  451584   790  450794  0%  450560  409600  40960  234
 49  451584   790  450794  0%  450560  409600  40960  234
 50  451584   792  450792  0%  450560  409600  40960  232
 51  451584   792  450792  0%  450560  409600  40960  232
...                                                       
380  451584   790  450794  0%  450560  409600  40960  234
381  451584   792  450792  0%  450560  409600  40960  232
382  451584   790  450794  0%  450560  409600  40960  234
384  451584   792  450792  0%  450560  409600  40960  232
...

The result is very impressive. JRockit JVM R28.2.7 requires only 441MB to run a program that has a 400MB base memory usage plus 40MB fluctuating memory usage with object size of 1.25MB. Basically, the JRockit GC requires only 1MB to manage dead objects and other system tasks.

But please note that JRockit must run GC much more frequently than HotSpot to support this low free memory situation. This will definitely impact the execution time performance of the application.

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

►Garbage Collection Tests

 GCTest2.java - Garbage Collection Test Program

 640/400/40MB Test on HotSpot Client 1.7

 640/400/40MB Test on HotSpot Client 1.6

 640/400/40MB Test on JRockit 28.2

►441/400/40MB Test on JRockit 28.2

 1076/800/80MB Test on HotSpot Client 1.7

 1076/800/80MB Test on HotSpot Client 1.6

 1076/800/80MB Test on JRockit 28.2

 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