cpu_affinity_thread.c

#define _GNU_SOURCE
#include <stdio.h>
#include <math.h>
#include <unistd.h>
#include <pthread.h>


double waste_time(long n){
    double res = 0;
    long i = 0;
    while(i < n * 200000){
        i++;
        res += sqrt(i);
    }
    return res;
}

void *thread_func(void *param){
    unsigned long mask = 0b0001; /* process 0 */
    /* bind process to processor 0 */
    if(pthread_setaffinity_np(pthread_self(), sizeof(mask), (cpu_set_t *)&mask) < 0){
        perror("pthread_setaffinity_np");
    }
    /* waste some time so the work is visible with "top" */
    printf("result: %f\n", waste_time(2000));
    mask = 0b0010;
    sleep(2);
    if(pthread_setaffinity_np(pthread_self(), sizeof(mask), (cpu_set_t *)&mask)){
        perror("pthread_setaffinity_np");
    }
    /* waste some more time to see the processor switch */
    printf("result: %f\n", waste_time(2000));

    mask = 0b0100;
    sleep(2);
    if(pthread_setaffinity_np(pthread_self(), sizeof(mask), (cpu_set_t *)&mask)){
        perror("pthread_setaffinity_np");
    }
    /* waste some more time to see the processor switch */
    printf("result: %f\n", waste_time(2000));

    mask = 0b1000;
    sleep(2);
    if(pthread_setaffinity_np(pthread_self(), sizeof(mask), (cpu_set_t *)&mask)){
        perror("pthread_setaffinity_np");
    }
    /* waste some more time to see the processor switch */
    printf("result: %f\n", waste_time(2000));


    return 0;
}

int main(int argc, char * argv[]){
    pthread_t my_thread;

    if(pthread_create(&my_thread, NULL, thread_func, NULL) != 0){
        perror("pthread_create");
    }

    // pthread_exit(NULL);
    pthread_join(my_thread, NULL);
    return 0;
}