Limiting the maximal virtual memory of a process within itself on Linux.

limit-virtual-memory.c

//
// Limits the maximal virtual memory of the process to half of the total
// amount of RAM on the system.
//
// Linux only.
//
// Compilation:
//
//   gcc -std=c11 -pedantic limit-virtual-memory.c -o limit-virtual-memory
//

#include <stdio.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/sysinfo.h>

int main() {
    // Find the total amount of RAM on the system.
    struct sysinfo system_info;
    int rc = sysinfo(&system_info);
    if (rc != 0) {
        perror("error: sysinfo() failed");
        exit(1);
    }

    size_t total_ram = system_info.totalram;
    printf("Total RAM:   %4lu GB\n", total_ram / 1024 / 1024 / 1024);
    size_t limited_ram = total_ram / 2;
    printf("Limiting to: %4lu GB\n", limited_ram / 1024 / 1024 / 1024);

    // Limit the virtual memory for the process.
    struct rlimit limit = {
        .rlim_cur = limited_ram,  // Soft limit.
        .rlim_max = RLIM_INFINITY // Hard limit (ceiling for rlim_cur).
    };
    rc = setrlimit(RLIMIT_AS, &limit);
    if (rc != 0) {
        perror("error: setrlimit() failed");
        exit(1);
    }

    // Verification.
    // This should succeed:
    void* mem1 = malloc(limited_ram / 2);
    if (mem1 == NULL) {
        fprintf(stderr, "error: unexpectedly failed to allocate memory\n");
        exit(1);
    }
    free(mem1);
    // This should fail:
    void* mem2 = malloc(limited_ram);
    if (mem2 != NULL) {
        free(mem2);
        fprintf(stderr, "error: unexpectedly succeeded to allocate memory\n");
        exit(1);
    }
    free(mem2);

    return 0;
}