Proxy compilation of dynamically loaded Java classes with MoJo

  • Authors:

  • Matt Newsome;Des Watson

  • Affiliations:

  • University of Sussex, Falmer, Brighton, BN1 9QH, UK;University of Sussex, Falmer, Brighton, BN1 9QH, UK

  • Venue:
  • Proceedings of the joint conference on Languages, compilers and tools for embedded systems: software and compilers for embedded systems
  • Year:
  • 2002

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Abstract

Interest in Java implementations for resource-constrained environments such as embedded systems has been tempered by concerns regarding its efficiency. Current native compilers for Java offer dramatic increases in efficiency, but have poor support for dynamically-loaded classes, which are typically served by slow interpreters or JIT compilers, the code-size of this latter utterly mismatching the resource constraints of the system.After a brief survey of Ahead-of-Time compilers for Java, we present MoJo --- a new native compiler and the testbed for our proxy compilation scheme, which allows embedded clients to connect to servers and delegate compilation of Java class packages to native code libraries.We also present initial results from experimental testing using MoJo in a resource-constrained, mobile computing environment. We show that MoJo is faster than all surveyed Java implementations for the test platform executing our initial test application. Our proxy compilation scheme results in a 94% speed increase over the fastest tested interpreter system and a 20% speed increase over the fastest tested JIT system.The MoJo-generated binaries for the application are also shown to be 45 times smaller than those required by its nearest iPAQ JRE competitor and 275 times smaller than the Sun JRE v1.3.1 for iPAQ as a direct result of our incremental, on-demand transfer of API classes to the client.