performance problem with process fork in gcj compiled CNI

[Ricardo Temporal]

performance problem with process fork in gcj compiled CNI

Hello,

    I have a simple C++ program with a main function that fork itself's 
process and then it starts a loop calling some processing in java compiled 
code, using CNI.

   I intend to split processing in a machine with 2 CPUs using fork 
technology, I'm not able to use another solution.

   When I run the program without forking, it takes about T seconds to 
finish consuming 100% of CPU and 50% of the machine.

    When I run the program with a fork in the beginning, it takes more than 
2T seconds to finish with each process consuming 100% of CPU and both 
consuming 100% of the machine.

    What's happening ?

Temporal.

#include <iostream>
#include <string>
#include <sys/types.h>
#include <unistd.h>
#include <gcj/cni.h>
#include <java/lang/Double.h>
#include <java/util/ArrayList.h>

using namespace std;
using namespace java::lang;
using namespace java::util;

int globalVariable = 2;

/*
	Code Templates:

	http://www-personal.umich.edu/~rusekd/articles/soc_prelim.html
	http://www.yolinux.com/TUTORIALS/ForkExecProcesses.html
*/

int	main(int argc, char **argv)
{
	if (argc != 3)
	{
		cerr << "usage: integer bool" << endl;
		return 1;
	}

	cout << "begin" << endl;

	JvCreateJavaVM(NULL);
	JvAttachCurrentThread(NULL, NULL);

   string sIdentifier;
   int    iStackVariable = 20;

   pid_t pID = (atol(argv[2]) ? fork() : 1);

   if (pID == 0)                // child
   {
      // Code only executed by child process

      sIdentifier = "Child Process: ";
      globalVariable++;
      iStackVariable++;
    }
    else if (pID < 0)            // failed to fork
    {
        cerr << "Failed to fork" << endl;
        exit(1);
        // Throw exception
    }
    else                                   // parent
    {
      // Code only executed by parent process

      sIdentifier = "Parent Process:";
    }

    // Code executed by both parent and child.

    cout << sIdentifier;
    cout << " Global variable: " << globalVariable;
    cout << " Stack variable: "  << iStackVariable << endl;

	ArrayList	*arrayList = new ArrayList;

	int	loopSize = atol(argv[1]);
	int	maxArraySize = loopSize >> 3;

	for(int	i = 0, j = 0; i < loopSize; i++, j++)
	{
		arrayList->add(new Double((jdouble)(double)i));

		if (j == maxArraySize)
		{
			j = 0;

			jint	size = arrayList->size();

			arrayList->clear();

			cout << pID << ", clear from " << (int)size << " to " << 
(int)arrayList->size() << endl;
		}
	}

	JvDetachCurrentThread();

	cout << "end" << endl;

	return 0;
}