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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
/*
*
* Sample target application for jvmti demos
*
* java Context [threadCount [iterationCount [sleepContention]]]
* Default: java Context 5 10 0
*
* threadCount Number of threads
* iterationCount Total turns taken for all threads
* sleepContention Time for main thread to sleep while holding lock
* (creates monitor contention on all other threads)
*
*/
/* Used to sync up turns and keep track of who's turn it is */
final class TurnChecker {
int thread_index;
TurnChecker(int thread_index) {
this.thread_index = thread_index;
}
}
/* Creates a bunch of threads that sequentially take turns */
public final class Context extends Thread {
/* Used to track threads */
private static long startTime;
private static TurnChecker turn = new TurnChecker(-1);
private static int total_turns_taken;
/* Used for each Context thread */
private final int thread_count;
private final int thread_index;
private final int thread_turns;
/* Main program */
public static void main(String[] argv) throws InterruptedException {
int default_thread_count = 5;
int default_thread_turns = 10;
int default_contention_sleep = 0;
int expected_turns_taken;
long sleepTime = 10L;
/* Override defaults */
if ( argv.length >= 1 ) {
default_thread_count = Integer.parseInt(argv[0]);
}
if ( argv.length >= 2 ) {
expected_turns_taken = Integer.parseInt(argv[1]);
default_thread_turns = expected_turns_taken/default_thread_count;
}
expected_turns_taken = default_thread_count*default_thread_turns;
if ( argv.length >= 3 ) {
default_contention_sleep = Integer.parseInt(argv[2]);
}
System.out.println("Context started with "
+ default_thread_count + " threads and "
+ default_thread_turns + " turns per thread");
/* Get all threads running (they will block until we set turn) */
for (int i = 0; i < default_thread_count; i++) {
new Context(default_thread_count, i, default_thread_turns).start();
}
/* Sleep to make sure thread_index 0 make it to the wait call */
System.out.println("Context sleeping, so threads will start wait");
Thread.yield();
Thread.sleep(sleepTime);
/* Save start time */
startTime = System.currentTimeMillis();
/* This triggers the starting of taking turns */
synchronized (turn) {
turn.thread_index = 0;
turn.notifyAll();
}
System.out.println("Context sleeping, so threads can run");
Thread.yield();
Thread.sleep(sleepTime);
/* Wait for threads to finish (after everyone has had their turns) */
while ( true ) {
boolean done;
done = false;
synchronized (turn) {
if ( total_turns_taken == expected_turns_taken ) {
done = true;
}
/* Create some monitor contention by sleeping with lock */
if ( default_contention_sleep > 0 ) {
System.out.println("Context sleeping, to create contention");
Thread.yield();
Thread.sleep((long)default_contention_sleep);
}
}
if ( done )
break;
System.out.println("Context sleeping, so threads will complete");
Thread.sleep(sleepTime);
}
long endTime = System.currentTimeMillis();
long totalTime = endTime - startTime;
System.out.println("Total time (milliseconds): " + totalTime);
System.out.println("Milliseconds per thread: " +
((double)totalTime / (default_thread_count)));
System.out.println("Context completed");
System.exit(0);
}
/* Thread object to run */
Context(int thread_count, int thread_index, int thread_turns) {
this.thread_count = thread_count;
this.thread_index = thread_index;
this.thread_turns = thread_turns;
}
/* Main for thread */
public void run() {
int next_thread_index = (thread_index + 1) % thread_count;
int turns_taken = 0;
try {
/* Loop until we make sure we get all our turns */
for (int i = 0; i < thread_turns * thread_count; i++) {
synchronized (turn) {
/* Keep waiting for our turn */
while (turn.thread_index != thread_index)
turn.wait();
/* MY TURN! Each thread gets thread_turns */
total_turns_taken++;
turns_taken++;
System.out.println("Turn #" + total_turns_taken
+ " taken by thread " + thread_index
+ ", " + turns_taken
+ " turns taken by this thread");
/* Give next thread a turn */
turn.thread_index = next_thread_index;
turn.notifyAll();
}
/* If we've had all our turns, break out of this loop */
if (thread_turns == turns_taken) {
System.out.println("Loop end: thread got " + turns_taken
+ " turns, expected " + thread_turns);
break;
}
}
} catch (InterruptedException intEx) {
System.out.println("Got an InterruptedException:" + intEx);
/* skip */
}
/* Make sure we got all our turns */
if ( thread_turns != turns_taken ) {
System.out.println("ERROR: thread got " + turns_taken
+ " turns, expected " + thread_turns);
System.exit(1);
}
}
}