I'm trying to nail down a reasonable micro-benchmark we can use
internally at Apple for tracking issues related to File IO Performance.
Note that this test requires junit.jar somewhere on your classpath.
You can get it at www.junit.org
Here's approximately where I'm at just now.
Comments and suggestions welcome.
/**
* Track performance numbers for reading / writing to a file.
*
**/
public static Test suite() {
return new TestSuite(FileIO.class);
}
public static void main (String[] args) {
junit.textui.TestRunner.run(suite());
}
// Constants (twiddled to make the test take about 20 secs on a
fast G5)
static int FILE_LOOPS = 51;
static int IO_LOOPS = 128;
static int SIZE = 1024 * 64;
static int DATA_MEGS = (SIZE * IO_LOOPS) / (1024 * 1024);
// IO Buffers
byte[] w_buffer = new byte[SIZE];
byte[] r_buffer = new byte[SIZE];
// Cache several test times, log average and mean
long starttime;
long writetimes[] = new long[ FILE_LOOPS];
long readtimes[] = new long[ FILE_LOOPS];
//
// fill a buffer with data for later check
//
void doFill(int tag) {
byte data = (byte) (tag % 16);
Arrays.fill(w_buffer, data);
}
//
// check that the file is intact (assuming doFill above was used)
//
void doCheck(int tag) {
byte data = (byte) (tag % 16);
for (int i = 0; i < w_buffer.length; i+=1) {
if ( r_buffer[i] != (byte) data) {
System.out.println("i " + i + " expected " + data +
" actual " + r_buffer[i]);
}
assertTrue( r_buffer[i] == (byte) data);
}
}
//
// Loop, writing and then re-reading several test files withh data.
// Note that this loop doesn't check the contents in any
meaningful way
//
public void testRawSpeed() throws Exception {
// Repeatedly write out buffers to testfiles. Then re-read
said buffers.
for (int j = 0; j < FILE_LOOPS; j+=1) {
File testfile = File.createTempFile("speedcheck", ".dat");
try {
// Check time to fill with data
starttime = System.currentTimeMillis();
FileOutputStream os = new FileOutputStream(testfile);
for( int i = 0; i < IO_LOOPS; i++) {
os.write( w_buffer);
}
os.flush();
writetimes[j] = System.currentTimeMillis() - starttime;
// Check time to pull all data
starttime = System.currentTimeMillis();
FileInputStream is = new FileInputStream(testfile);
while ( is.read( r_buffer) != -1) {
// do nothing...
}
readtimes[j] = System.currentTimeMillis() - starttime;
}
finally {
testfile.delete();
}
}
doRawSpeedReporting();
}
void doRawSpeedReporting() {
// Test is somewhat variable, so run on several files,
reporting average and mean times.
Arrays.sort( writetimes );
Arrays.sort( readtimes );
long net = 0;
for (int j = 0; j < FILE_LOOPS; j+=1) {
net += writetimes[j];
// System.out.println( "time to write " + SIZE *
IO_LOOPS + " was " + writetimes[j]);
}
public void testCheckedSpeed() throws Exception {
// Repeatedly write out buffers to testfiles. Then re-read
said buffers.
for (int j = 0; j < FILE_LOOPS; j+=1) {
File testfile = File.createTempFile("speedcheck", ".dat");
try {
// Check time to fill with data
starttime = System.currentTimeMillis();
FileOutputStream os = new FileOutputStream(testfile);
for( int i = 0; i < IO_LOOPS; i++) {
doFill(i); // <-- not free, time is
included in test
os.write( w_buffer);
}
os.flush();
writetimes[j] = System.currentTimeMillis() - starttime;
// Check time to pull all data
starttime = System.currentTimeMillis();
FileInputStream is = new FileInputStream(testfile);
long netCount = 0;
int currCount = 0;
while ( (currCount = is.read( r_buffer)) != -1) {
netCount += currCount;
int i = (int) (netCount/SIZE) -1;
doCheck(i); // <-- not free, time is included
in test
}
readtimes[j] = System.currentTimeMillis() - starttime;
}
finally {
testfile.delete();
}
}
doCheckedSpeedReporting();
}
void doCheckedSpeedReporting() {
// Test is somewhat variable, so run on several files,
reporting average and mean times.
Arrays.sort( writetimes );
Arrays.sort( readtimes );
long net = 0;
for (int j = 0; j < FILE_LOOPS; j+=1) {
net += writetimes[j];
// System.out.println( "time to write " + SIZE *
IO_LOOPS + " was " + writetimes[j]);
}
System.out.println( "\n");
System.out.println( "FileOutputStream fill and write " +
DATA_MEGS + "K avg " + net / FILE_LOOPS);
System.out.println( "FileOutputStream fill and write " +
DATA_MEGS + "K mean " + writetimes[ (FILE_LOOPS/2) + 1] );
net = 0;
for (int j = 0; j < FILE_LOOPS; j+=1) {
net += readtimes[j];
// System.out.println( "time to read " + SIZE * IO_LOOPS
+ " was " + readtimes[j]);
}
System.out.println( "\n");
System.out.println( "FileInputStream read and check " +
DATA_MEGS + "K avg " + net / FILE_LOOPS);
System.out.println( "FileInputStream read and check " +
DATA_MEGS + "K mean " + readtimes[ (FILE_LOOPS/2) + 1] );
}
}
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