Challenges and Solutions for Embedded Java

Michael Wortley

Computer Integrated Surgery

March 1, 2001

TINI CORBA ORB Project

• Goal: to port Java based CORBA ORB to TINI board

• Problem: Converting from JDK1.3 to TINI’s embedded Java

Goals of this Presentation

• Provide background of Java’s benefits

• Show how embedded environment presents challenges to the Java platform

• Highlight available solutions

Main Sources

• “Challenges to Embedded Java”– Charlie McDowell, UC Santa Cruz– 1998 PowerPoint presentation

• “Technical Overview of Embedded Java”– 4/2000, From Sun Website

Other Sources

• “Java Schism?”– Rick Cook, Java Report 6/99

• “About Java Technology”– Sun Website

• TINI software information from www.iButton.com

Goals of this Presentation

• Provide background of Java’s benefits

• Show how embedded environment presents challenges to the Java platform

• Highlight available solutions

“Write Once, Run Anywhere.”

Why do Programmers like Java?

• Compiled and Interpreted

• Easy Upgrades through API

• JVM = Portability

Goals of this Presentation

• Provide background of Java’s benefits

• Show how embedded environment presents challenges to the Java platform

• Highlight available solutions

“Challenges to Embedded Java”

PowerPoint Presentation by Charlie McDowell, 1998.

Key Points

• Java is superior to C++ in ease of development, maintenance, and portability

• Java API and JVM put too much stress on embedded processors

• Java tends to have slower execution time

Key Points

• Automatic garbage collection causes problems

• Java lacks real-time support

Java Memory Requirements

• Storage of Java API– up to 9 MB for JDK1.1

• JVM– between 300 and 800 KB

• Garbage Collection Overhead– copy collectors -> requires 2x max. heap

usage– conservative collectors -> memory leaks

Java Execution Time

• Interpreted code runs more slowly than compiled code

• Resolving references prior to execution reduces run time

• Using final and static methods can reduce dynamic dispatch of functions

• Garbage Collection eats memory

Garbage Collection

• Part of what makes Java simple

• Problematic for real-time applications

Java and Real-Time Applications

• Java lacks:– reliable methods of estimating worst case– ability to measure CPU time, memory use– enforcement of time and space budgets– real-time garbage collection

• IMPROVEMENTS NEEDED!

Suggested Optimizations for Embedded Java

• Reduce API to free memory

• Use final and static functions to decrease execution time

• Eliminate automatic garbage collection

• Find ways to improve real-time performance

Non-Sun Embedded Java

• PERC by NewMonics– real-time garbage collection

• VxWorks– only 628 KB

• JN from UCSC– JIT from Kaffe– reduced API

Goals of this Presentation

• Provide background of Java’s benefits

• Show how embedded environment presents challenges to the Java platform

• Highlight available solutions

“Technical Overview of Embedded Java Technology”

Sun Microsystems

http://java.sun.com/products/embeddedjava/overview.html

Improvements in Sun’s Embedded Java

• Configurable API

• Configurable JVM

• JavaFilter tool

• JavaCodeCompact

• JavaDataCompact

New Programming Tools

• JavaFilter– input

• source code • Java API

– output• list of necessary API

classes and methods

New Programming Tools

• JavaCodeCompact– input

• Source Code • Java API• list of necessary API

classes and methods

– output• data structures in C

code

New Programming Tools

• JavaDataCompact– input

• associated data files • Java API

– output• data structures in C

code

How this Relates to TINI

• TINI’s embedded Java is Sun compatible.

• Limitted API• Development Tools

– TINI API– TINIConvertor

Conclusions about Embedded Java

• Increasing complexity of embedded devices will force makers to use high level language

• Java’s fast development time and portability are ideal for large manufacturers

• Competition needed to drive advancements

So long, and thanks for all the fish.