[Linux] process use multi-core CPU

/*
 * The following code use sched_setaffinity to set CPU mask
 * it will fork process and each process will run on only one core
 *
 * you can read from /proc/cpuinfo to get the number of processor
 */
int setup_multicore(int n)
{
    cpu_set_t *cpuset = CPU_ALLOC(n);
    size_t size = CPU_ALLOC_SIZE(n);
    CPU_ZERO_S(size, cpuset);
    CPU_SET_S(0, size, cpuset);
    if (sched_setaffinity(getpid(), size, cpuset) < 0) {
        CPU_FREE(cpuset);
        return -1;
    }
    pid_t pid = 0;
    // fork a child for each core
    for (int i = 1; i < n; ++i) {
        pid = fork();
        if (pid  0)
            continue;
        CPU_ZERO_S(size, cpuset);
        CPU_SET_S(i, size, cpuset);
        if (sched_setaffinity(getpid(), size, cpuset) < 0) {
            CPU_FREE(cpuset);
            return -1;
        }
        break;
    }
    CPU_FREE(cpuset);
}