memhog.c

memhog.c

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

#define CHUNK (128 * 1024)

void usage(const char *prog, FILE *out)
{
        fprintf(out, "usage: %s allocsize\n", prog);
        fprintf(out, " allocsize is kbytes, or number[KMGP] (P = pages)\n");
        exit(out == stderr);
}

int main(int argc, char *argv[])
{
        long long kbtotal = 0, kballoc;
        int i, j, k, numchunk, alloc, sum, rc = 0;
        char **mem, *tmp;

        if (argc == 2) {
                char *end = NULL;
                kbtotal = strtoull(argv[1], &end, 0);

                switch(*end) {
                case 'g':
                case 'G':
                        kbtotal *= 1024;
                case 'm':
                case 'M':
                        kbtotal *= 1024;
                case '\0':
                case 'k':
                case 'K':
                        break;
                case 'p':
                case 'P':
                        kbtotal *= 4;
                        break;
                default:
                        usage(argv[0], stderr);
                        break;
                }
        }

        if (argc != 2 || kbtotal == 0)
                usage(argv[0], stderr);

        numchunk = (kbtotal + CHUNK - 1) / CHUNK;
        mem = calloc(numchunk, sizeof(*mem));
        if (mem == NULL) {
                fprintf(stderr, "error allocating initial chunk array\n");
                exit(1);
        }

        alloc = CHUNK;
        printf("[%d] allocating %lld kbytes in %u kbyte chunks\n",
               getpid(), kbtotal, alloc);
        fflush(stdout);
        for (i = kballoc = 0; i < numchunk; i++, kballoc += alloc) {
                if (kbtotal - kballoc < alloc)
                        alloc = kbtotal - kballoc;

                tmp = mem[i] = malloc(alloc * 1024);
                if (tmp == NULL) {
                        fprintf(stderr, "malloc(%u) failed (%lld/%lld)\n",
                                alloc * 1024, kballoc, kbtotal);
                } else {
                        printf("touching %p (%lld/%lld)\n",
                               tmp, kballoc, kbtotal);
                        for (j = 0; j < alloc; j += 4) {
                                for (k = 0, sum = 0; k < 4095; k++, tmp++)
                                        sum += *tmp;
                                *tmp = sum;
                        }
                }
        			  fflush(stdout);
        }
        printf("touched %lld kbytes\n", kballoc);

        alloc = CHUNK;
        printf("verifying %lld kbytes in %u kbyte chunks\n", kbtotal, alloc);
        for (i = kballoc = 0; i < numchunk; i++, kballoc += alloc) {
                if (kbtotal - kballoc < alloc)
                        alloc = kbtotal - kballoc;

                tmp = mem[i];
                if (tmp != NULL) {
                        printf("verifying %p (%lld/%lld)\n",
                               tmp, kballoc, kbtotal);
                        for (j = 0; j < alloc; j += 4) {
                                for (k = 0, sum = 0; k < 4095; k++, tmp++)
                                        sum += *tmp;
                                if (*tmp != sum) {
                                        fprintf(stderr, "sum %x != %x at %p\n",
                                                *tmp, sum, tmp - 4092);
                                        rc = 1;
                                }
                        }
                }
        }
        printf("verified %lld kbytes\n", kballoc);
        return rc;
}