WCS V5.1 Performance Tuning

200 WCS V5.1 Performance Tuning

GCStats.java

// GCStats.java

// This utility tabulates data generated from a verbose garbage collection

trace.

// To run this utility type:

// java GCStats inputfile [total_time]

//

// Gennaro (Jerry) Cuomo - IBM Corp. 03/2000

// Carmine F. Greco 3/17/00 - JDK1.2.2 compatibility

//

import java.io.*;

import java.util.*;

public class GCStats {

static int total_time=-1; // total time of run in ms

static long total_gctime=0, total_gctime1=0; // total time spent in GCs

static long total_bytes=0, total_bytes1=0; // total bytes collected

static long total_free=0, total_free1=0; // total

static int total_gc=0; // total number of GCs

static boolean verbose=false; // debug trace on/off

public static void parseLine(String line) {

// parsing a string that looks like this...

// <GC(31): freed 16407744 bytes in 107 ms, 97% free

(16417112/16777208)>

if (isGCStatsLine(line)) { // First test if line starts with "<GC..."

if (verbose) System.out.println("GOT a GC - "+line);

long temp=numberBefore(line, " bytes")/1024; // get total memory

collected

total_bytes+=temp; total_bytes1+=(temp*temp);

temp=numberBefore(line, " ms"); // get time in GC

total_gctime+=temp; total_gctime1+=(temp*temp);

temp=numberBefore(line, "% free"); // get time % free

total_free+=temp; total_free1+=(temp*temp);

if (temp!=0) {

total_gc++; // total number of GCs

}

}

}

public static int numberBefore( String line, String s) {

int ret = 0;

int idx = line.indexOf(s);

Appendix D. GCStats.java 201

int idx1= idx-1;

if (idx>0) {

// the string was found, now walk backwards until we find the blank

while (idx1!=0 && line.charAt(idx1)!=' ') idx1--;

if (idx1>0) {

String temp=line.substring(idx1+1,idx);

if (temp!=null) {

ret=Integer.parseInt(temp); // convert from string to number

}

} else {

if (verbose) System.out.println("ERROR: numberBefore() - Parse

Error looking for "+s);

}

}

return ret;

}

public static boolean isGCStatsLine(String line) {

return ( (line.indexOf("<GC") > -1) && (line.indexOf(" freed")>0) &&

(line.indexOf(" bytes")>0));

}

public static void main (String args[]) {

String filename=null;

BufferedReader foS=null;

boolean keepgoing=true;

if (args.length==0) {

System.out.println("GCStats - ");

System.out.println(" - ");

System.out.println(" - Syntax: GCStats filename

[run_duration(ms)]");

System.out.println(" - filename = file containing -verbosegc

data");

System.out.println(" - run_duration(ms) = duration of fixed work

run in which GCs took place");

return;

}

if (args.length>0) {

filename=args[0];

}

if (args.length>1) {

total_time=Integer.parseInt(args[1]);

}

if (verbose) System.out.println("Filename="+filename);

try {

foS = new BufferedReader(new FileReader(filename));

202 WCS V5.1 Performance Tuning

} catch (Throwable e) {

System.out.println("Error opening file="+filename);

return;

}

while (keepgoing) {

String nextLine;

try {

nextLine=foS.readLine();

} catch (Throwable e) {

System.out.println("Cannot read file="+filename);

return;

}

if (nextLine!=null) {

parseLine(nextLine);

} else {

keepgoing=false;

}

}

try {

foS.close();

} catch (Throwable e) {

System.out.println("Cannot close file="+filename);

return;

}

System.out.println("-------------------------------------------------");

System.out.println("- GC Statistics for file - "+filename);

System.out.println("-------------------------------------------------");

System.out.println("-**** Totals ***");

System.out.println("- "+total_gc+" Total number of GCs");

System.out.println("- "+total_gctime+" ms. Total time in GCs");

System.out.println("- "+total_bytes+" Kbytes. Total memory collected

during GCs");

System.out.println("- ");

System.out.println("-**** Averages ***");

double mean=total_gctime/total_gc,

stddev=Math.sqrt((total_gctime1-2*mean*total_gctime+total_gc*mean*mean)/total_g

c);

int imean=new Double(mean).intValue(), istddev=new

Double(stddev).intValue();

System.out.println("- "+imean+" ms. Average time per GC.

(stddev="+istddev+" ms.)");

mean=total_bytes/total_gc;

stddev=Math.sqrt((total_bytes1-2*mean*total_bytes+total_gc*mean*mean)/total_gc)

;

imean=new Double(mean).intValue(); istddev=new Double(stddev).intValue();

Appendix D. GCStats.java 203

System.out.println("- "+imean+" Kbytes. Average memory collected per GC.

(stddev="+istddev+" Kbytes)");

mean=total_free/total_gc;

stddev=Math.sqrt((total_free1-2*mean*total_free+total_gc*mean*mean)/total_gc);

imean=new Double(mean).intValue(); istddev=new Double(stddev).intValue();

System.out.println("- "+imean+"%. Free memory after each GC.

(stddev="+istddev+"%)");

if (total_time>0 && total_gctime>0) {

System.out.println("- "+((total_gctime*1.0)/(total_time*1.0))*100.0+"%

of total time ("+total_time+"ms.) spent in GC.");

}

System.out.println("___________________________ "+new Date());

System.out.println("");

}

204 WCS V5.1 Performance Tuning