last results using the java instrumentation suite

Last results using the Java Instrumentation Suite
Jordi Guitart, Jordi Torres, Eduard Ayguadé, José Ol iver and Jesús Labarta
European Center for Parallel ism of Barcelona (CEPBA)
Computer Architecture Department, Technical Universi ty of Catal oni a
C/ Jordi Girona 1-3, Campus Nord UPC, Mòdul C6, E-08034 Barcelona (Spain)
{ jguitart, torres, eduard, j oseo, j esus} @ac.upc.es
Abstract. This report presents the Java Instrumentati on Sui te (JIS), a set of tools designed to
instrument Java threaded applications using dynamic code interposition (avoiding the
instrumentation and recompi lation of the source code and/or the Java Virtual Machine JVM).
The report descri bes the desi gn of JIS and hi ghl ights the results obtained usi ng JIS for
improving threaded appl ications performance.
1. Introduction
The rapi d maturing process of the Java technology is encouraging users the development of
portabl e applicati ons using the Java l anguage. As an i mportant part of the defi nition of the Java
language, the use of threads is becomi ng commonplace when programming this kind of
appli cations. Understanding and tuning threaded applications requires the use of effective tools
for detecting possi bl e performance bottlenecks.
The support for this mul tithreaded environment requires, for each platform, an effici ent
mapping of Java threads to the underlying system threads. Thread support traverses many layers:
from the appl ication, through various Java cl asses (e.g., Thread and ThreadGroup), then through
the platform-independent layer, the platform-speci fic layer, and final ly to the operating system
itsel f. While this layering provides a clean separati on of responsi bi liti es and allows many
platforms to "pl ug i n" their support, it also contributes to extra overhead.
The Java Instrumentation Suite (JIS) enables a detail ed analysis of the applicati on behavior by
recordi ng the state of each thread al ong the execution of the appli cation. The instrumentation is
done using dynami c code interposition at the JVM level (avoiding modificati ons in the source
code and its recompilati on).
Current i mpl ementati ons of the JVM allow Java threads to be scheduled by the virtual machine
itsel f (the so-called green threads model) or by the operating system (the so-called native threads
model). When using green threads, the operati ng system does not know anything about threads
that are handl ed by the virtual machi ne. From the point of view of the operating system, there is a
single process and a singl e thread; i t is up to the virtual machine to handle all the detai ls of the
threadi ng API. In the native threads model, threads are scheduled by the operati ng system that is
hosting the vi rtual machine. JIS allows the analysis of threaded appl ications running on these two
execution model s.
To our knowl edge, i t is the first tool that handles the Java thread schedul ing representation of
an appli cation [GTAO00]. JIS is a part of Barcelona Java Suite (BJS) currently under
development at CEPBA. The main purpose of BJS is to serve as platform for doi ng research on
scheduling mechanisms and policies oriented towards the efficient executi on of multithreaded
Java applicati ons on parallel servers.