Transient Blocking Synchronization

We introduce Transient Blocking Synchronization (TBS), a new approach to hardware synchronization for mega-scale distributed-memory multiprocessor machines. Such machines, with thousands of processors and controller based memory modules, are essentially distributed networks, and one must search for new paradigms that provide hardware synchronization support with high levels of robustness and minimal protocol and communication overhead. It is our claim that the semantics of non-blocking synchronization primitives such as Compare&Swap; and LoadLinked/StoreConditional on the one hand, and blocking ones such as Full/Empty-bits on the other, will introduce high communication and space costs when implemented on large scale machines. TBS is a novel hardware synchronization paradigm resting between the classic blocking and non-blocking approaches to synchronization. It is an example of how, based on very weak ‘‘transient’’ hardware blocking, that is, blocking that may be revoked at any time, one can provide non-blocking universal synchronization with low communication and space complexity. This paper presents a set of simple TBS single-location synchronization operations and shows that they provide low cost non-blocking emulations of all known read-modify-write operations. Moreover, it shows that the combination of TBS with hardware supported transactional bits, a variation on traditional hardware full/empty bits, can provide low message cost implementations of multi-word transactional operations. email addresses: [email protected] [email protected] © 2005 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, 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/. Transient Blocking Synchronization