[Nrg-l] BU/CS Colloquium by Chandra Krintz: April 4, 2008

Azer Bestavros best at cs.bu.edu
Thu Apr 3 22:22:02 EDT 2008

Boston University
Computer Science Colloquium Series

   Title: XMem -- Safe, Efficient, and Transparent Shared-Memory 
          Communication Across Managed Runtime Systems

 Speaker: Chandra Krintz
          Department of Computer Science
          University of California, Santa Barbara

    When: Friday April 4, 2008 @ 11:00am
   Where: MCS-135 

Developers of contemporary enterprise applications are implemented to
use type-safe component-based platforms, such as J2EE, and architected
to comprise multiple tiers, such as a web container, an application
server, and a database engine. Each tier typically executes in its own
managed runtime environment (MRE) to improve reliability and to manage
system complexity through the fault containment and modularity offered
by isolated MRE instances. Such isolation, however, necessitates
expensive cross-tier communication based on protocols such as object
serialization and remote procedure calls. Administrators commonly
co-locate communicating MREs on a single host to reduce communication
overhead and to better exploit increasing numbers of available
processing cores. However, state-of-the-art MREs offer no support for
more efficient communication between co-located MREs, while fast
inter-process communication mechanisms, such as shared memory, are
widely available as a standard operating system service on most modern

In this talk, we present the design and implementation of XMem --
type-safe, transparent, shared memory support for co-located MREs. XMem
guarantees type-safety through coordinated, yet distributed and
parallel, multi-process class loading and garbage collection. To avoid
introducing any level of indirection, XMem manipulates virtual memory
mapping. In addition, object sharing in XMem is fully transparent:
shared objects are identical to local objects in terms of field access,
synchronization, garbage collection, and method invocation, with the
only difference being that shared-to-private pointers are disallowed.
Moreover, existing communication technologies, such as RMI,
serialization, and network sockets can be transparently integrated with

We have implemented XMem in the open-source, production-quality HotSpot
Java Virtual Machine. Our experimental evaluation, based on core
communication technologies underlying J2EE, as well as using real
applications, indicates that XMem significantly improves throughput and
response time by avoiding the overheads imposed by object serialization
and network transfer. 



Chandra Krintz is an Associate Professor at the University of
California, Santa Barbara (UCSB).  She joined the UCSB faculty in 2001
after receiving her M.S. and Ph.D. degrees in Computer Science from the
University of California, San Diego (UCSD) under the advisement of Dr.
Brad Calder.  Chandra's research interests include automatic and
adaptive compiler, virtual runtime, and operating system techniques that
improve performance (for high-end systems) and increase battery life
(for mobile, resource-constrained devices).  In particular,  her work
focuses on exploiting repeating patterns in the time-varying behavior of
underlying resources, applications, and workloads to guide dynamic
optimization and specialization of program and system components.

Host: Azer Bestavros

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