Configuring VC++ Multithreaded Memory Management

Listing 1: heaptest.c — Multithreaded memory tester.

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <process.h>
#include <stdio.h>
#include <stdlib.h>

/* compile with cl /MT heaptest.c */

/* to switch to the system heap issue the following command
   before starting heaptest from the same command line
   set __MSVCRT_HEAP_SELECT=__GLOBAL_HEAP_SELECTED,1 */

/* structure transfers variables to the worker threads */
typedef struct tData
{
    int maximumLength;
    int allocCount;
} threadData;

void printUsage(char** argv)
{
    fprintf(stderr,"Wrong number of parameters.\nUsage:\n");
    fprintf(stderr,"%s threadCount maxAllocLength allocCount\n\n",
        argv[0]);
    exit(1);
}

unsigned __stdcall workerThread(void* myThreadData)
{
    int count;
    threadData* myData;
    char* dummy;

    srand(GetTickCount()*GetCurrentThreadId());
    myData=(threadData*)myThreadData;

    /* now let us do the real work */
    for(count=0;count<myData->allocCount;count++)
    {
        dummy=(char*)malloc((rand()%myData->maximumLength)+1);
        free(dummy);
    }
    _endthreadex(0);

    /* to satisfy compiler */
    return 0;
}

int main(int argc,char** argv)
{
    int threadCount;
    int count;
    threadData actData;
    HANDLE* threadHandles;
    DWORD startTime;
    DWORD stopTime;
    DWORD retValue;
    unsigned dummy;

    /* check parameters */
    if(argc<4 || argc>4)
        printUsage(argv);

    /* get parameters for this run */
    threadCount=atoi(argv[1]);
    if(threadCount>64)
        threadCount=64;
    actData.maximumLength=atoi(argv[2])-1;
    actData.allocCount=atoi(argv[3]);

    threadHandles=(HANDLE*)malloc(threadCount*sizeof(HANDLE));

    printf("Test run with %d simultaneous threads:\n",threadCount);
    startTime=GetTickCount();
    for(count=0;count<threadCount;count++)
    {
        threadHandles[count]=(HANDLE)_beginthreadex(0,0,
            &workerThread, (void*)&actData,0,&dummy);
        if(threadHandles[count]==(HANDLE)-1)
        {
            fprintf(stderr,"Error starting worker threads.\n");
            exit(2);
        }
    }

    /* wait until all threads are done */
    retValue=WaitForMultipleObjects(threadCount,threadHandles
        ,1,INFINITE);
    stopTime=GetTickCount();
    printf("Total time elapsed was: %d milliseconds",
        stopTime-startTime);
    printf(" for %d alloc operations.\n",
        actData.allocCount*threadCount);
    /* cleanup */
    for(count=0;count<threadCount;count++)
        CloseHandle(threadHandles[count]);
    free(threadHandles);
    return 0;
}
/* End of File */