Introspection of a JavaTM Virtual Machine under Simulation

Virtual machines are commonly used in commercially-significant systems, for example, Sun Microsystems’ Java and Microsoft’s .NET. The virtual machine offers many advantages to the system designer and administrator, but complicates the task of workload characterization: it presents an extra abstraction layer between the application and observed hardware effects. Understanding the behavior of the virtual machine is therefore important for all levels of the system architecture. We have constructed a tool which examines the state of a Sun Java HotSpotTM virtual machine running inside Virtutech’s Simics execution-driven simulator. We can obtain detailed information about the virtual machine and application without disturbing the state of the simulation. For data, we can answer such questions as: Is a given address in the heap? If so, in which object? Of what class? For code, we can map program counter values back to Java methods and approximate Java source line information. Our tool allows us to relate individual events in the simulation, for example, a cache miss, to the higher-level behavior of the application and virtual machine. In this report, we present the design of our tool, including its capabilities and limitations, and demonstrate its application on the simulation’s cache contents and cache misses. email addresses: [email protected] [email protected] [email protected] [email protected] © 2006 Sun Microsystems, Inc. All rights reserved. The SML Technical Report Series is published by Sun Microsystems Laboratories, of Sun Microsystems, Inc. Printed in U.S.A. Unlimited copying without fee is permitted provided that the copies are not made nor distributed for direct commercial advantage, and credit to the source is given. Otherwise, no part of this work covered by copyright hereon may be reproduced in any form or by any means graphic, electronic, or mechanical, including photocopying, recording, taping, or storage in an information retrieval system, without the prior written permission of the copyright owner. TRADEMARKS Sun, Sun Microsystems, the Sun logo, Java, Java HotSpot, Java Native Interface, and Solaris are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. in the U.S. and other countries. Products bearing SPARC trademarks are based upon an architecture developed by Sun Microsystems, Inc. UNIX is a registered trademark in the United States and other countries, exclusively licensed through X/Open Company, Ltd. For information regarding the SML Technical Report Series, contact Jeanie Treichel, Editor-in-Chief .All technical reports are available online on our website, http://research.sun.com/techrep/. Introspection of a Java Virtual Machine under Simulation * Work performed during an internship at Sun Microsystems Greg Wright Sun Microsystems Laboratories Mailstop UMPK16–159 16 Network Circle Menlo Park CA 94025 [email protected] Phil McGachey* Dept. of Computer Sciences Purdue University 250 N. University Street West Lafayette IN 47907-2066 [email protected] Erika Gunadi* Dept. of Electrical & Computer Engineering University of Wisconsin–Madison 1415 Engineering Drive Madison WI 53706 [email protected] Mario Wolczko Sun Microsystems Laboratories Mailstop UMPK16–158 16 Network Circle Menlo Park CA 94025 [email protected]