C program to allocate memory as a way of testing system limits.

glom.c

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

#include <sys/resource.h>

void print_rlims(char* name, struct rlimit* const rl)
{
    if (rl->rlim_cur == RLIM_INFINITY)
        printf("    cur %s = unlimited\n", name);
    else
        printf("    cur %s = %ld = %ld MiB\n", name, rl->rlim_cur, rl->rlim_cur/(1024*1024));

    if (rl->rlim_max == RLIM_INFINITY)
        printf("    max %s = unlimited\n", name);
    else
        printf("    max %s = %ld = %ld MiB\n", name, rl->rlim_max, rl->rlim_max/(1024*1024));
}

int main(int argc, char** argv)
{
    size_t i = 0;
    size_t n = 1024;
    size_t interval = 128;
    size_t* x = NULL;

    struct rlimit rl;
    int lim;

    if (argc == 2) {
        n = strtoul(argv[1], NULL, 0);
    } else {
        fprintf(stderr, "Usage: glom N\n");
        fprintf(stderr, "       N = amount of memory in MiB\n");
        exit(1);
    }

    rl.rlim_cur = 700 * 1024 * 1024;
    rl.rlim_max = 700 * 1024 * 1024;
    setrlimit(RLIMIT_DATA, &rl);

    printf("Memory allocation test\n");
    printf("======================\n");
    printf("\n");
    printf("Current system limits:\n");
    lim = getrlimit(RLIMIT_AS, &rl);
    print_rlims("as", &rl);
    lim = getrlimit(RLIMIT_DATA, &rl);
    print_rlims("data", &rl);
    printf("\n");

    /* try to allocate */
    printf("Allocating %ld MiB\n", n);
    n *= 1024 * 1024 / sizeof(size_t);
    fflush(stdout);

    x = (size_t*)calloc(n, sizeof(size_t));
    if (x == (size_t*)NULL) {
        perror("allocation failed");
        exit(1);
    }

    /* fill array */
    for (i = 0; i < n; ++i) {
        x[i] = i;
    }

    interval = n/8; /* want only 8 printouts */
    for (i = 0; i < n; ++i) {
        if (i % interval == 0)
            printf("\tx[%ld] = %ld\n", i, x[i]);
    }

    printf("Sleeping...");
    fflush(stdout);
    for (i = 0; i < 250; ++i) {
        printf(".");
        fflush(stdout);
        sleep(3); /* no. of seconds */
    }
    printf(" Done.\n");

    free(x);

    return 0;
}