ctest.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *      The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * SUCH DAMAGE.
 */

/*
 * Performance test from former 161 prof. Brad Chen
 * Stresses VM.
 *
 * Intended for the VM assignment. This should run successfully on a
 * variety of strides when the VM system is complete. Strides that are
 * not a multiple of 2 work better; see below.
 */

#include <stdio.h>
#include <stdlib.h>

/*
 * SIZE is the amount of memory used.
 * DEFAULT is the default stride.
 * Note that SIZE and DEFAULT should be relatively prime.
 */
#define SIZE      (1024*1024/sizeof(struct entry))
#define DEFAULT   477

struct entry {
        struct entry *e;
};

struct entry array[SIZE];

int
main(int argc, char **argv)
{
        volatile struct entry *e;
        unsigned i, stride;

        stride = DEFAULT;
        if (argc == 2) {
                stride = atoi(argv[1]);
        }
        if (stride <= 0 || argc > 2) {
                printf("Usage: ctest [stridesize]\n");
                printf("   stridesize should not be a multiple of 2.\n");
                return 1;
        }

        printf("Starting ctest: stride %d\n", stride);
        
        /*
         * Generate a huge linked list, with each entry pointing to
         * the slot STRIDE entries above it. As long as STRIDE and SIZE
         * are relatively prime, this will put all the entries on one
         * list. Otherwise you will get multiple disjoint lists. (All
         * these lists will be circular.)
         */
        for (i=0; i<SIZE; i++) {
                array[i].e = &array[(i+stride) % SIZE];
        }

        /*
         * Traverse the list. We stop after hitting each element once.
         *
         * (If STRIDE was even, this will hit some elements more than 
         * once and others not at all.)
         */
        e = &array[0];
        for (i=0; i<SIZE; i++) {
                if (i % stride == 0) {
                        putchar('.');
                }
                e = e->e;
        }

        printf("\nDone!\n");
        return 0;
}