rtji

Issues in the Design and Implementation

of Real-Time Java™

Published on July 19, 1996 by Kelvin Nilsen

Notes on Feb 15, 1999 by X. Ma (maxi@cs.cornell.edu)

Goals

Standardization of Java extensions for supporting development of reliable real-time software

Challenge in Real-Time System

Portability

Dynamic adaptability

Fault tolerance

A Real-Time Activity in JAVA

Configuration manager : adjust for the local computing environment

Administrator : continuously reevaluate resource budget

Atomic code segments

Real time tasks and runnable threads

Cyclic real-time tasks
Sporadic real-time tasks
Spontaneous real-time tasks
Ongoing real-time tasks

The real-time executive : allocate time and memory with efficient algorithms
Real-time management of dynamic memory

Implementation Details

The Java Virtual Machine

The byte-code analyzer and translator

The real-time executive

Run-time services

Real-time garbage collection

Conservative mark and sweep GC
Copying GC and Brook’s optimization
Accurate incremental mark and sweep GC
Mostly stationary real-time GC
Real-time generational GC
Hardware-assistanted real-time GC

Discussion Points

What is the ideal real-time system?

What is the ideal garbage collector?

What is the current state of GC technique?

Will the Java HotSpot have big impact on RTJ business?

What are the main applications in the RTJ business?

To build a RTJ system, it is desirable to integrate a custom software implementation with custom hardware designed to support real-time GC and fine-grained control of time. How does this activity impact on the portability of JAVA?