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OSDI 2000 Abstract
Processes in KaffeOS:
Isolation, Resource Management, and Sharing in Java
Godmar Back, Wilson C. Hsieh, Jay Lepreau , School of Computing
University of Utah
Abstract
Single-language runtime systems, in the form of Java virtual machines, are widely deployed platforms for executing untrusted mobile code. These
runtimes provide some of the features that operating systems provide: inter-application memory protection and basic system services. They do not,
however, provide the ability to isolate applications from each other, or limit their resource consumption. This paper describes KaffeOS, a Java
runtime system that provides these features. The KaffeOS architecture takes many lessons from operating system design, such as the use of a
user/kernel boundary, and employs garbage collection techniques, such as write barriers.
The KaffeOS architecture supports the OS abstraction of a process in a Java virtual machine. Each process executes as if it were run in its own
virtual machine, including separate garbage collection of its own heap. The difficulty in designing KaffeOS lay in balancing the goals of isolation
and resource management against the goal of allowing direct sharing of objects. Overall, KaffeOS is no more than 11% slower than the freely
available JVM on which it is based, which is an acceptable penalty for the safety that it provides. Because of its implementation base, KaffeOS is
substantially slower than commercial JVMs for trusted code, but it clearly outperforms those JVMs in the presence of denial-of-service attacks or
misbehaving code.
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