ColloquiaTalk by Y. Charlie Hu, Rice University - Monday, May 7th

[Margery Ishmael]

Monday, May 7th at 2:30 p.m. in Ryerson 251

Y. Charlie Hu
Rice University

presents:
"Run-Time Support For Distributed Sharing in Safe Languages"

Distributed shared memory (DSM) systems support cost-effective parallel
computing on networks of workstations by providing the application with a
shared memory abstraction.  How to build the most efficient DSM systems has
been extensively studied for over a decade.  However, the state-of-the-art
DSM systems are still limited to providing only one granularity with good
performance. Coarse-grained sharing systems are typically page-based from
the use of the VM hardware for access and modification detection, and their
performance suffer from false-sharing for fine-grained applications.
Fine-grained sharing systems typically augment the executable with
instructions to detect reads and writes, freeing them from the large size
of the consistency unit in VM-based systems, but introducing per-access
overhead that reduces performance for coarse-grained applications.

In this talk, I will present the design and evaluation of the first runtime
system (called DOSA) that allows efficient and transparent sharing of data
with both fine-grained and coarse-grained access patterns.  DOSA supports
sharing of objects in a safe language (such as Java) between the different
computers within a cluster. It exploits the key insight that the absence
of pointer arithmetic enables the decoupling of shared
object space from the address space.  Our performance evaluation
demonstrates that the new system performs comparably to a state-of-the-art
page-based DSM (TreadMarks) for coarse-grained applications, and
significantly outperforms TreadMarks for fine-grained applications (up to
98%) and a garbage-collected application (65% for OO7).

In addition, the new system offers many advantages over earlier distributed
object sharing systems.  In the new system, direct access through a
reference to object data is supported, unlike Java/RMI, where remote object
access is restricted to method invocation.  Furthermore, in languages with
suitable multithreading support, such as Java, distributed execution is
transparent: no new API is introduced for distributed sharing.  This
transparency distinguishes this work from many earlier distributed object
sharing systems.

HOSTS: Ian Foster & Ridgway Scott
*The talk will be followed by refreshments in Ryerson 255*
If you would like to meet the speaker, please send e-mail to 
marge at cs.uchicago.edu
-- 
Margery Ishmael
Department of Computer Science
The University of Chicago
1100 E. 58th Street
Chicago, IL. 60637

Tel. 773-834-8977  Fax. 773-702-8487