Communicator e3000 MPE/iX Release 7.0 Express 1 (Software Release C.70.01) (30216-90328)

Chapter 5 121

Technical Articles

Introducing the HotSpot Virtual Machine for Java

by Mike Yawn, Commercial Systems Division

The implementation of Java on the HP e3000 just got a lot faster thanks to the new

technology included in the HotSpot Virtual Machine. The HotSpot VM is a completely

compatible alternative to the Classic Java Virtual Machine. The latest Software

Developer’s Kit (SDK) for Java, which is included with this release, contains both the

HotSpot and the Classic JVMs

What’s new?

The primary advantage of the HotSpot VM is performance. Benchmarks show typical

performance improvements of from 2 to 5 times when using the HotSpot VM compared to

the ‘Classic’ virtual machine shipped in all versions of Java to date.

HotSpot VM Features

• Performanc

Faster interpreter than the Classic Java VM

HotSpot compiler is more selective about what code to compile, and then compiles

selected code to higher levels of optimization than JIT compilers

Better garbage collection and thread synchronization performance

• Better scaleability on multiprocessor systems

• Improved reliability

• Platform for future performance improvements

What’s included

The HotSpot and Classic JVMs both co-exist in this release of Java. In a future release,

the Classic JVM will be dropped and HotSpot will be the only JVM provided. There were

changes made to the Java directory structure beginning in JDK 1.2 in order to support the

eventual release of HotSpot.

Java is installed in a directory location beginning with

/usr/local/java/jdk1.3

The portions of Java that change with hotspot are two libraries, libjvm (the Java VM) and

libhpi (the Host Porting Interface). The Classic versions of these ﬁles are in the following

locations:

/usr/local/java/jdk1.3/jre/lib/PA-RISC/classic/libjvm.sl

/usr/local/java/jdk1.3/jre/lib/PA-RISC/green_threads/libhpi.sl

The HotSpot versions of the same two ﬁles are located here:

/usr/local/java/jdk1.3/jre/lib/PA-RISC/hotspot/libjvm.sl

/usr/local/java/jdk1.3/jre/lib/PA-RISC/native_threads/libhpi.sl