Using the Pablo Java PCF: A Tutorial

The Pablo Java Performance Capture Facility (Java PCF) is a set of Java classes that can be substituted for the Java classes FileInputStream, FileOutputStream, FileReader, FileWriter and RandomAccessFile so that I/O performance data in Java codes can be captured and measured. These programs perform exactly the same functions as their standard counterparts, but they have been augmented by instrumentation software, attached before and after the call itself, to capture internal data. Programmers compile their instrumented source code linked it with the PabloIOTracing.jar Java archive, then execute in the normal manner. During program execution, performance data captured by the instrumentation is recorded in SDDF trace files.  Each operation of the instrumented classes is then recorded. This allows the user to analyze the I/O behavior of the application over time..

Instrumenting A Java Code

In profiling the performance of an application's I/O behavior, the Java PCF can be used to capture performance metrics for the FileInputStream, FIleOutputStream, FileReader, FileWriter and RandomAccessFile classes during program execution. An event, in this context, occurs each time a method in these classes is invoked that performs disk I/O.  

• Begin by obtaining the package PabloJavaIOTracing.zip from the Pablo website. The package contains the PabloIOTracing.jar and PabloIOTracing.jarContent files. Unzip the package into a folder declared in your classpath or add the PabloIOTracing.jar file to the File Systems with the NetBeans IDE. . 
•  In any class to be instrumented, substitute the class names FileInputStream with PabloFileInputStream, FileOutputStream with PabloFileOutputStream, FileReader with PabloFileReader, FileWriter with PabloFileWriter, and RandomAccessFile with PabloRandomAccessFile. Add the import statement to your code:

import PabloIOTracing.*;

• In the main class, before invoking any methods performing I/O operations, instantiate a PabloTracer object specifying the name of the trace file to be generated and a processor number (use 0 if in doubt):

PabloTracer pt = PabloTracer("C:/MyJavaFolder/myTraceFile",procNumber);

Output will be generated in the file C:/MyJavaFolder/myTraceFile.p where p is the value of procNumber in the declaration.  The code can then be built in the usual manor using javac or NetBeans.

• Finally, in the main class, after all methods of the instrumented classes have been invoked, add a call to the end( ) method of the PabloTracer object:

pt.end();

Failure to make this call will result in an incomplete trace.

Select from the following links for examples of Java code before and after I/O instrumentation.

Sample Java Code Before Pablo I/O Instrumentation

Sample Java Code After Pablo I/O Instrumentation