Re: concurrency, threads and objects

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On 16.11.2006 18:45, Tom Forsmo wrote:


Yep, threads on modern systems are very cheap. I once cooked up a small
program (attached) to collect thread stats. On my 3GHz P4D with Win XP
Pro x64 it yields

max t11 - start time in thread: 140
avg t11 - start time in thread: 4.14126
max t2 - creation time : 78
avg t2 - creation time : 0.03084
max t3 - start time in main : 78
avg t3 - start time in main : 0.1558

max t11 - start time in thread: 204
avg t11 - start time in thread: 5.35656
max t2 - creation time : 16
avg t2 - creation time : 0.0282
max t3 - start time in main : 16
avg t3 - start time in main : 0.15657

5ms as average starting time for a thread isn't really much.


I do not think so - rather it is consciously trying to find a good OO
design. OOA/D/P are quite different from procedural. While I do agree
that thought has to be given to issues of memory consumption and CPU
usage during design of performance critical applications, overdoing it
is certainly doing more harm than good. Considering the overhead of one
object created per thread to be too much will definitively harm the
design of the application. And this is even more so true in Java where
the overhead of object creation on modern VM's is negligible.
Performance might be one goal but there are tons of other goals. If you
have the ultra performant application that nobody can maintain then
you're getting nowhere.

 > I don't mean to be rude and condescending towards java or


I would be very carefully carrying over knowledge from a C environment
to a Java or other OO environment. While there are similarities and
general principles one must be aware of the platform and adjust to its
specifics.

Regards

    robert

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package threads;

import java.util.Iterator;
import java.util.List;
import java.util.Vector;

/**
 * @author robert.klemme
 * @created 04.07.2005 10:29:35
 * @version $Id:$
 */
public class ThreadCreationOverhead {

    private static final int THREADS = 100000;

    private static class Maximizer {
        private long max = 0;
        private long sum = 0;
        private int count = 0;

        public synchronized void update( long n ) {
            if ( n > max ) {
                max = n;
            }

            sum += n;
            ++count;
        }

        public synchronized long getMax() {
            return max;
        }

        public synchronized double getAvg() {
            return ( ( double ) sum ) / count;
        }
    }

    private static void print( String msg ) {
        // System.out.println( Thread.currentThread().getName() + ": " + msg );
    }

    public static void main( String[] args ) {
        testRun();
        System.out.println();
        testRun();
    }

    private static void testRun() {
        final Maximizer mt11 = new Maximizer();
        final Maximizer mt2 = new Maximizer();
        final Maximizer mt3 = new Maximizer();

        List threads = new Vector();

        for ( int i = 0; i < THREADS; ++i ) {
// System.out.println( "Run " + i );
            final long t1 = System.currentTimeMillis();
            Thread th = new Thread(
                new Runnable() {
                    public void run() {
                        long t11 = System.currentTimeMillis() - t1;
                        mt11.update( t11 );
                        print( "in thread: " + t11 );
                    }
                } );
            long t2 = System.currentTimeMillis() - t1;
            th.start();
            long t3 = System.currentTimeMillis() - t1;
            mt2.update( t2 );
            print( "after creation: " + t2 );
            mt3.update( t3 );
            print( "after start: " + t3 );
// System.out.println();

            threads.add( th );
        }

        for ( Iterator iter = threads.iterator(); iter.hasNext(); ) {
            Thread th = ( Thread ) iter.next();
            try {
                th.join();
            }
            catch ( InterruptedException e ) {
                e.printStackTrace();
            }
        }

        System.out.println( "max t11 - start time in thread: " + mt11.getMax() );
        System.out.println( "avg t11 - start time in thread: " + mt11.getAvg() );
        System.out.println( "max t2 - creation time : " + mt2.getMax() );
        System.out.println( "avg t2 - creation time : " + mt2.getAvg() );
        System.out.println( "max t3 - start time in main : " + mt3.getMax() );
        System.out.println( "avg t3 - start time in main : " + mt3.getAvg() );
    }
}

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