1. J2SE 5.0 Performance White Paper
Java™ Platform Performance Engineering
Sun Microsystems, Inc.
Table of Contents
1 Introduction
2 New Features and Performance Enhancements
2.1 Ergonomics in the 5.0 Java Virtual Machine
2.2 High Precision Timing
2.3 StringBuilder Class
2.4 Java 2D Technology Improvements
2.5 Image I/O Improvements
2.6 Thread Priority on the Solaris Platform
2.7 Class Data Sharing
2.8 Monitoring and Management for the Java Platform
2.9 Optimizations for x86 / x64
2.10 HotSpot™ Reliability
2.11 Concurrent Low Pause Garbage Collector Improvements
3 New Platform Support
3.1 Hardware
3.1.1 AMD Opteron
3.2 Operating Environments
3.2.1 Solaris 10
3.2.2 Sun Java Desktop System, Release 2
3.2.3 Windows Server 2003
3.2.4 Red Hat Enterprise Linux AS 3.0
3.2.5 SuSE Linux Enterprise Server 9
4 Going Further
4.1 Java Performance Portal
4.1.1 Ergonomics in the 5.0 Java Virtual Machine
4.1.2 Tuning Garbage Collection with the 5.0 Java Virtual Machine
4.1.3 jvmstat 3.0
4.2 J2SE 5.0 Documentation
4.3 Performance Articles
4.3.1 Using JConsole to Monitor Applications
4.3.2 The JVMPI Transition to JVMTI
4.4 Benchmark Disclosures

2. 4.4.1 SPECjbb 2000
4.4.2 VolanoMark™ 2.5
1 Introduction
While J2SE 5.0 has added many new features Sun Microsystems has also been working to
continue to improve scalability and performance, with a new emphasis on startup time and
memory footprint.
This guide gives an overview of the performance and scalability improvements made in the
J2SE 5.0 release along with various benchmarks to demonstrate the impact of these
improvements.
2 New Features and Performance
Enhancements
J2SE 5.0 includes a number of new features and enhancements to improve performance in
many areas of the platform. Improvements to new language features include: additions to the
virtual machine, enhancements to the base and integration libraries, the user interface,
deployment, tools and architectures, and OS & hardware platforms. Enhancements to
program execution speed include: Garbage collection ergonomics, StringBuilder class, Java
2D technology enhancements, and performance and memory usage improvements to image
I/O.
2.1 Ergonomics in the 5.0 Java Virtual Machine
Getting the best performance out of the JVM has often required detailed hand tuning of
command line options. Yet many users never set command line options for performance. In
order to give the best possible performance in a variety of situations Sun Microsystems has
improved the performance of the JVM even when no command line options are used.
In J2SE 5.0 the default selection for the garbage collector, heap size, and runtime compiler
are now chosen automatically. These new selections better match the needs of different types
of applications while requiring less command line tuning.
In addition a different way of tuning the heap has been added for the throughput garbage

3. collector. This new tuning allows the user to specify performance and memory utilization
criteria to dynamically tune the sizes of the heap. This "self tuning" behavior is referred to in
this document as "ergonomics". For more on ergonomics please see the Ergonomics in the
5.0 Java Virtual Machine document.
The performance improvements from ergonomics are significant. Here we compare
SPECjbb2000 performance between J2SE 1.4.2 and J2SE 5.0. This test was conducted on a
Sun Fire V40z with 4 x 2.4 GHz AMD Opteron CPU's and 8 GB RAM running Solaris 10:
In each case we ran the benchmark without any performance arguments (except that -
Xmx512m was required for proper benchmark execution with J2SE 1.4.2).
Please see the SPECjbb 2000 Benchmark Disclosure
We also compared VolanoMark™ 2.5 performance between J2SE 1.4.2 and J2SE 5.0. This
test was conducted on
a Sun Fire V40z with 4 x 2.4 GHz AMD Opteron CPU's and 8 GB RAM running Solaris 10:

4. In each case we ran the benchmark in loopback mode without any performance arguments.
The result shown is based upon relative throughput (messages per second with 400 loopback
connections)
The full java version for J2SE 1.4.2 is:
java version "1.4.2_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_06-b03)
Java HotSpot(TM) Client VM (build 1.4.2_06-b03, mixed mode)
The full java version for J2SE 5.0 is:
java version "1.5.0_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_01-b08)
Java HotSpot(TM) Server VM (build 1.5.0_01-b08, mixed mode)
Please see the VolanoMark™ 2.5 Benchmark Disclosure
2.2 High Precision Timing
The method System.nanoTime() has been added, providing access to a nanosecond-
granularity time source for relative time measurements. The actual precision of the time
values returned by System.nanoTime() is platform-dependent.
2.3 StringBuilder Class

5. This class provides an API compatible with StringBuffer, but with no guarantee of
synchronization. This class is designed for use as a drop-in replacement for StringBuffer in
places where the string buffer was being used by a single thread (as is generally the case).
Where possible, it is recommended that this class be used in preference to StringBuffer as it
will be faster under most implementations. See the API documentation on StringBuilder for
more information.
2.4 Java 2D Technology Improvements
Added 2D features include expanded Linux and Solaris printer support, new methods for
creating fonts from files and streams, and new methods related to VolatileImages and
hardware acceleration of images. A number of internal changes to text rendering code greatly
improve its robustness, performance, and scalability. Other performance work includes
hardware-accelerated rendering using OpenGL (disabled by default). See the Java 2D
documentation for more information.
2.5 Image I/O Improvements
J2SE 5.0 improves image processing performance and adds readers and writers for new file
formats to the Image I/O system. For more information see the Image I/O documentation.
2.6 Thread Priority on the Solaris Platform
JRE 5.0 updates the priority mapping such that Java threads at NORM_PRIORITY can now
compete as expected with native threads. An excellent reference for these topics is Chapter 9,
"Threads," in Joshua Bloch's book Effective Java Programming Language Guide. See also the
Thread Priority on the Solaris Platform document.
2.7 Class Data Sharing
The class data sharing feature is aimed at reducing application startup time and footprint. The
installation process loads a set of classes from the system jar file into a private, internal
representation, then dumps that representation to a "shared archive" file. During subsequent
JVM invocations, the shared archive is memory-mapped in, saving the cost of loading those
classes and allowing much of the JVM's metadata for these classes to be shared among
multiple JVM processes. For more information see the Class Data Sharing documentation.
Java Virtual Machine performance improvements in J2SE 5.0, including Class Data Sharing,
have contributed to improved startup and footprint performance. Here we compare startup
performance between J2SE 1.4.2 and J2SE 5.0. This test was conducted on a Pentium 4 2.8

6. GHz system with 1 GB memory. The benchmark measures the time necessary to initialize the
NetBeans IDE version 3.5.1:
The startup comparison above shows relative performance (bigger is better): for Windows XP
J2SE 5.0 starts 8% faster,
and on the Sun Java Desktop System J2SE 5.0 starts 22% faster than J2SE 1.4.2, respectively.
Below we compare memory footprint required between J2SE 1.4.2 and J2SE 5.0 for starting
up a rich client Swing-based application:

7. The footprint comparison above shows relative performance (smaller is better). Measuring the
real memory impact of a Java application is often quite difficult. Perhaps the first hurdle in
understanding footprint is that conventional system utilities, such as Task Manager on
Windows, only tell part of the footprint story. Memory reported depends on whether
application data and programs are read as conventional files or memory mapped files. In other
words often the true memory footprint of an application includes all the files that have been
brought into the operating system's file system memory cache... Often memory pages that are
shared by other processes or in the file system cache are not reported by conventional tools.
Getting consistent footprint measurements is further complicated by accurately measuring the
same moment in an application's lifetime. Clearly the longer an application operates the more
likely it is to perform classloading, compilation or other activities that affect footprint. The
fantastic news for users of J2SE 5.0 is that despite adding massive new functionality Java
Engineering has actually pared down core JVM memory usage and leveraged Class Data
Sharing to make the actual memory impact on your system lower than with J2SE 1.4.2!
The systems used for this benchmark included:
Windows XP Professional, Version 2002, Service Pack 1
running on a 930 Mhz Pentium III system with 384MB of RAM
Red Hat Linux 3.0 Advanced Server
running on a 1.4 GHz system with 512 MB of RAM
Solaris 9 running on a SunBlade 2000, 900 Mhz UltraSPARC IV machine with 1GB

8. of RAM
2.8 Monitoring and Management for the Java Platform
This release of J2SE offers significant enhancements for monitoring and management for the
Java platform using JMX and SNMP. Please see the Monitoring and Management for the Java
Platform document for details.
2.9 Optimizations for x86 / x64
Many changes were made in J2SE 5.0 to take advantage of the performance features in
modern x86 and x64 CPUs. A good example of this are the optimizations made to
System.arraycopy(). In J2SE 1.4.2 System.arraycopy() was implemented using
memmove() which performed well on Solaris, but was found to be a performance bottleneck
on Linux. In J2SE 5.0, calls to memmove() were replaced with highly optimized x86 and x64
instructions tailored for running Java on these modern processors.
Here we compare array copy performance between J2SE 1.4.2 and J2SE 5.0. This test was
conducted on
a Sun Fire V40z with 4 x 2.4 GHz AMD Opteron CPU's and 8 GB RAM running Solaris 10:

9. The benchmark shown above involves copying large amounts of data in several threads, with
heavy use of System.arraycopy(). The test was conducted using highly tuned parameters
for J2SE 1.4.2 and the exact same parameters for J2SE 5.0 as to eliminate any advantage
J2SE 5.0 would gain from ergonomics. Here we are highlighting the array copy optimization
on x86 platforms while holding the hardware constant.
2.10 HotSpot™ Reliability
The Java™ HotSpot™ virtual machine for J2SE 5.0 benefits from improved reliability. But
how is reliability related to performance, you ask?
Because the performance of a JVM that's down is zero!
During the development cycle for J2SE 5.0 a series of release controls were put in place that
have resulted in much better product reliability.
The J2SE 5.0 release of the HotSpot™ virtual machine includes 8000 bug fixes.

10. 2.11 Concurrent Low Pause Garbage Collector Improvements
As mentioned above Java™ HotSpot™ Ergonomics includes the choice of the garbage
collection algorithm. In certain situations described in the Tuning Garbage Collection with the
5.0 Java Virtual Machine document concurrent low pause collector may be a better choice for
the application at hand.
The Concurrent Low Pause Garbage Collector, also known as CMS, has had several
improvements for J2SE 5.0. Garbage collection pauses are shorter because of better use of
parallelism during collection periods during which application threads are stopped. The
pauses are also more uniform due to deliberately spacing pauses such that there is less impact
on collection latency as seen by application threads. And the heap is better utilized due to
improved promotion failure handling which postpones the need to start collections.
These improvements explain the dramatic performance gains in this CMS Server Benchmark
(a multi-threaded, memory intensive application). This test was conducted on dual CPU Xeon
3 GHz systems with 4 GB of memory:
J2SE 5.0 ergonomics also includes better handling of thread local allocation buffers (TLABs).

11. Adaptive resizing of TLABs reduces young generation fragmentation and wasted space thus
reducing the number of collections. While these TLAB improvements are not specific to
CMS we see here that they produce a dramatic improvement in the thread intensive
VolanoMark™ benchmark:
The result above was conducted on a 4 CPU Ultra 80 running Solaris 9 and comparing
throughput with 400 loopback connections. In each CMS result above we ran the benchmarks
the following options:
-server
-Xmx512m
-XX:+UseConcMarkSweepGC
The full java version for J2SE 1.4.2 is:
java version "1.4.2_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_06-b03)
Java HotSpot(TM) Client VM (build 1.4.2_06-b03, mixed mode)
The full java version for J2SE 5.0 is:
java version "1.5.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-b64)
Java HotSpot(TM) Server VM (build 1.5.0-b64, mixed mode)

12. Please see the VolanoMark™ 2.5 Benchmark Disclosure
3 New Platform Support
The cross-platform capabilities of Java have expanded in J2SE to cover additional hardware
and software platforms.
Please see the Supported System Configurations chart for full details.
3.1 Hardware
As a result of the Sun-AMD Alliance J2SE hardware platform coverage has expanded to
include performance enhancements for AMD Opteron.
3.1.1 AMD Opteron
The AMD Opteron is now supported for J2SE 5.0 with the following operating environments:
Solaris x86 (32-bit), Windows Server 2003 (32 and 64-bit) and Linux (32 and 64-bit).
Sun offers several products based on the AMD Opteron:
Sun Java Workstation W1100z
Sun Java Workstation W2100z
Sun Fire V20z Server
Sun Fire V40z Server
Compute Grid Rack System
3.2 Operating Environments
3.2.1 Solaris 10
Sun is proud to support J2SE 5.0 on Solaris 10 the leading UNIX in the world and sets the
standard for the next generation of operating systems with major breakthroughs in features,
functionality, and performance. Solaris 10 provides a world-class operating system from the

13. enterprise to the desktop and everything in between.
J2SE 5.0 update 2 now offers 64-bit support for Solaris x86 on AMD Opteron. Java
engineering has worked overtime to insure that the stack of J2SE 5.0 on Solaris x86 on AMD
Opteron delivers the best possible performance.
3.2.2 Sun Java Desktop System, Release 2
J2SE 5.0 is now supported on Sun Java Desktop System, Release 2.
Sun Java Desktop System, Release 2 delivers the best of open source software with the
technical innovation of Sun to offer an affordable, comprehensive, fully integrated desktop
client environment with administration and developer tools and an enterprise-ready support
offering that lowers business costs, reduces complexities of desktop management, and
provides a secure computing environment.
3.2.3 Windows Server 2003
J2SE 5.0 is supported on Windows Server 2003 Web Edition, Standard Edition, Enterprise
Edition and DataCenter Edition in addition to Windows XP Home and Professional, 2000
Professional, 98 2nd Edition and ME.
3.2.4 Red Hat Enterprise Linux AS 3.0
J2SE 5.0 is supported on Red Hat Enterprise Linux AS 3.0 and also Red Hat Enterprise Linux
AS 2.1, ES 2.1, WS 2.1 and Red Hat 9.0.
3.2.5 SuSE Linux Enterprise Server 9
J2SE 5.0 is supported on SuSE Linux Enterprise Server 9 in addition to SuSE Linux
Enterprise Server 8 and SuSE 8.2 and 9.
4 Going Further
4.1 Java Performance Portal
For the latest in Java Performance best practices, documentation, tools, FAQs, code samples,
White Papers and other Java performance news check out

14. the Java Performance Portal ( http://java.sun.com/performance/ ).
Three especially relevant performance links for J2SE 5.0 are given here:
4.1.1 Ergonomics in the 5.0 Java Virtual Machine
The Ergonomics in the 5.0 Java Virtual Machine (
http://java.sun.com/docs/hotspot/gc5.0/ergo5.html ) document provides an overview of the
new self tuning features of J2SE 5.0.
4.1.2 Tuning Garbage Collection with the 5.0 Java Virtual Machine
The Tuning Garbage Collection with the 5.0 Java Virtual Machine (
http://java.sun.com/docs/hotspot/gc5.0/gc_tuning_5.html ) document expands on GC
concepts for J2SE 5.0 that were introduced in the Tuning Garbage Collection with the 1.4.2
Java Virtual Machine ( http://java.sun.com/docs/hotspot/gc1.4.2/ ) document.
4.1.3 jvmstat 3.0
The jvmstat 3.0 ( http://java.sun.com/performance/jvmstat/ ) home page documents the
lightweight performance monitoring capabilities that are built into J2SE 5.0 and explains how
to use these tools to monitor not only 5.0 HotSpot Java Virtual Machines but also HotSpot
1.4.1 and 1.4.2 JVM's.
4.2 J2SE 5.0 Documentation
Be sure to check out the wealth of J2SE 5.0 Documentation (
http://java.sun.com/j2se/1.5.0/docs/ ) including the
New Features and Enhancements ( http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html )
and the
J2SE 5.0 Overview ( http://java.sun.com/j2se/1.5.0/docs/guide/index.html ).
4.3 Performance Articles
4.3.1 Using JConsole to Monitor Applications
Check out the article on Using JConsole to Monitor Applications (
http://java.sun.com/developer/technicalArticles/J2SE/jconsole.html ) to learn how to use this

15. GUI tool to find out how your Java application is performing.
4.3.2 The JVMPI Transition to JVMTI
Check out the article on The JVMPI Transition to JVMTI (
http://java.sun.com/developer/technicalArticles/Programming/jvmpitransition/ ) to learn more
about how these important interfaces, which are often used for performance analysis, have
changed.
4.4 Benchmark Disclosure
4.4.1 SPECjbb 2000
SPECjbb2000 is benchmark from the Standard Performance Evaluation Corporation (SPEC).
The performance referenced is based on Sun internal software testing conforming to the
testing methodologies listed above.
For the latest SPECjbb2000 results visit http://www.spec.org/osg/jbb2000.
4.4.2 VolanoMark™ 2.5
VolanoMark™ version 2.5 is a benchmark from Volano LLC ( http://www.volano.com/ ).