为线程绑定CPU

// learn gcc atomic variable
#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/syscall.h>
#include <linux/unistd.h>
#include <errno.h>
#include <sched.h>

#define INC_TO 1000000 // every thread adds 1 million times

int global_int = 0;

// get current thread id
pid_t gettid(void){
    return syscall(__NR_gettid);
    //return pthread_self(); // cannot work...
}

void *thread_routine(void *arg){
    int i;
    int proc_num = (int)(long)(arg);
    cpu_set_t set; // A CPU affinity mask

    CPU_ZERO(&set);
    CPU_SET(proc_num, &set);

    // ets the CPU affinity mask of this thread to the value specified by maski.
    //A thread's CPU affinity mask determines the set of CPUs on which it is eligible to run.
    if(sched_setaffinity(gettid(), sizeof(cpu_set_t), &set)){
        perror("sched_setaffinity");
        return NULL;
    }

    for(i = 0; i < INC_TO; i++){
        //global_int ++ ;
        __sync_fetch_and_add(&global_int, 1);
    }

    return NULL;
}

int main(){
    int procs = 0;
    int i;
    pthread_t *threads;

    //get the number of processors currently online (available).
    procs = (int)sysconf(_SC_NPROCESSORS_ONLN);   // mine is 16
    if(procs < 0){
        perror("sysconf");
        return -1;
    }

    threads = malloc(sizeof(pthread_t) * procs);
    if(threads == NULL){
        perror("malloc threads");
        return -1;
    }

    printf("Set up %d threads ....
", procs);
    for( i = 0; i < procs ; i++){
        if(pthread_create(&threads[i], NULL, thread_routine, (void *)(long)i)){
            perror("pthread_create");
            procs = i;
            break;
        }
    }

    for( i = 0; i < procs; i++){
        pthread_join(threads[i], NULL);
    }

    free(threads);

    printf("All threads work done.global_int is %d
", global_int);
    printf("The expected value is %d
" , INC_TO * procs);

    return 0;
}

參考：http://www.alexonlinux.com/multithreaded-simple-data-type-access-and-atomic-variables