Question

I have a very simple unit test that just allocates a lot of Strings:

public class AllocationSpeedTest extends TestCase {

    public void testAllocation() throws Exception {

        for (int i = 0; i < 1000; i++) {
            long startTime = System.currentTimeMillis();
            String a = "dummy";
            for (int j = 0; j < 1000; j++) {
                a += "allocation driven";
            }
            System.out.println(i + ": " + (System.currentTimeMillis() - startTime) + "ms " + a.length());
        }

    }

}

On my Windows PC (Intel Core Duo, 2.2GHz, 2GB) this prints on average:

...
71: 47ms 17005
72: 47ms 17005
73: 46ms 17005
74: 47ms 17005
75: 47ms 17005
76: 47ms 17005
77: 47ms 17005
78: 47ms 17005
79: 47ms 17005
80: 62ms 17005
81: 47ms 17005
...

On SunOS (5.10 Generic_138888-03 sun4v sparc SUNW, SPARC-Enterprise-T5120):

...
786: 227ms 17005
787: 294ms 17005
788: 300ms 17005
789: 224ms 17005
790: 260ms 17005
791: 242ms 17005
792: 263ms 17005
793: 287ms 17005
794: 219ms 17005
795: 279ms 17005
796: 278ms 17005
797: 231ms 17005
798: 291ms 17005
799: 246ms 17005
800: 327ms 17005
...

JDK version is 1.4.2_18 on both machines. JVM parameters are the same and are:

–server –Xmx256m –Xms256m

Can anyone explain why SUN super server is slower?

(http://www.sun.com/servers/coolthreads/t5120/performance.xml)

Answer 1

The CPU is indeed slower on SPARC (1.2Ghz) and as answered by one of the Sun’s engineers T2 is usualy 3 times slower for single-threaded application than modern Intel processors. Though, he also stated that in a multi-threaded environment SPARC should be faster.

I have made a multi-threaded test using GroboUtils library and tested both allocations (through concatenations) and simple calculations ( a += j*j ) to test processor. And I’ve got the following results:

1 thread : Intel : Calculations test : 43ms
100 threads : Intel : Calculations test : 225ms

1 thread : Intel : Allocations test : 35ms
100 threads : Intel : Allocations test : 1754ms

1 thread : SPARC : Calculations test : 197ms
100 threads : SPARC : Calculations test : 261ms

1 thread : SPARC : Allocations test : 236ms
100 threads : SPARC : Allocations test : 1517ms

SPARC shows its power here by outperforming Intel on 100 threads.

Here goes the multi-threaded calculation test:

import java.util.ArrayList;
import java.util.List;

import net.sourceforge.groboutils.junit.v1.MultiThreadedTestRunner;
import net.sourceforge.groboutils.junit.v1.TestRunnable;
import junit.framework.TestCase;

public class TM1_CalculationSpeedTest extends TestCase {

    public void testCalculation() throws Throwable {

        List threads = new ArrayList();
        for (int i = 0; i < 100; i++) {
            threads.add(new Requester());
        }
        MultiThreadedTestRunner mttr = new MultiThreadedTestRunner((TestRunnable[]) threads.toArray(new TestRunnable[threads.size()]));
        mttr.runTestRunnables(2 * 60 * 1000);

    }

    public class Requester extends TestRunnable {

        public void runTest() throws Exception {
            long startTime = System.currentTimeMillis();
            long a = 0;
            for (int j = 0; j < 10000000; j++) {
                a += j * j;
            }
            long endTime = System.currentTimeMillis();
            System.out.println(this + ": " + (endTime - startTime) + "ms " + a);
        }

    }

}

Here goes the multi-threaded allocation test:

import java.util.ArrayList;
import java.util.List;

import junit.framework.TestCase;
import net.sourceforge.groboutils.junit.v1.MultiThreadedTestRunner;
import net.sourceforge.groboutils.junit.v1.TestRunnable;

public class TM2_AllocationSpeedTest extends TestCase {

    public void testAllocation() throws Throwable {

        List threads = new ArrayList();
        for (int i = 0; i < 100; i++) {
            threads.add(new Requester());   
        }
        MultiThreadedTestRunner mttr = new MultiThreadedTestRunner((TestRunnable[]) threads.toArray(new TestRunnable[threads.size()]));
        mttr.runTestRunnables(2 * 60 * 1000);

    }

    public class Requester extends TestRunnable {

        public void runTest() throws Exception {
            long startTime = System.currentTimeMillis();
            String a = "dummy";
            for (int j = 0; j < 1000; j++) {
                a += "allocation driven";
            }
            long endTime = System.currentTimeMillis();
            System.out.println(this + ": " + (endTime - startTime) + "ms " + a.length());
        }

    }

}