CPU亲和力掩码(将线程放入不同的CPU) [英] CPU Affinity Masks (Putting Threads on different CPUs)

问题描述

我有4个线程，并且试图将线程1设置为在CPU 1上运行，线程2在CPU 2上运行，依此类推. 但是，当我在下面运行代码时，相似性掩码返回正确的值，但是当我在线程上执行sched_getcpu()时，它们都返回它们正在CPU 4上运行.

有人知道我的问题在哪里吗?

提前谢谢！

#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <sched.h>
#include <errno.h>

void *pthread_Message(char *message)
{
    printf("%s is running on CPU %d\n", message, sched_getcpu());
}

int main()
{
    pthread_t thread1, thread2, thread3, thread4;
    pthread_t threadArray[4];
    cpu_set_t cpu1, cpu2, cpu3, cpu4;
    char *thread1Msg = "Thread 1";
    char *thread2Msg = "Thread 2";
    char *thread3Msg = "Thread 3";
    char *thread4Msg = "Thread 4";
    int thread1Create, thread2Create, thread3Create, thread4Create, i, temp;

    CPU_ZERO(&cpu1);
    CPU_SET(1, &cpu1);
    temp = pthread_setaffinity_np(thread1, sizeof(cpu_set_t), &cpu1);
    printf("Set returned by pthread_getaffinity_np() contained:\n");
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu1))
            printf("CPU1: CPU %d\n", i);

    CPU_ZERO(&cpu2);
    CPU_SET(2, &cpu2);
    temp = pthread_setaffinity_np(thread2, sizeof(cpu_set_t), &cpu2);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu2))
            printf("CPU2: CPU %d\n", i);

    CPU_ZERO(&cpu3);
    CPU_SET(3, &cpu3);
    temp = pthread_setaffinity_np(thread3, sizeof(cpu_set_t), &cpu3);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu3))
            printf("CPU3: CPU %d\n", i);

    CPU_ZERO(&cpu4);
    CPU_SET(4, &cpu4);
    temp = pthread_setaffinity_np(thread4, sizeof(cpu_set_t), &cpu4);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu4))
            printf("CPU4: CPU %d\n", i);

    thread1Create = pthread_create(&thread1, NULL, (void *)pthread_Message, thread1Msg);
    thread2Create = pthread_create(&thread2, NULL, (void *)pthread_Message, thread2Msg);
    thread3Create = pthread_create(&thread3, NULL, (void *)pthread_Message, thread3Msg);
    thread4Create = pthread_create(&thread4, NULL, (void *)pthread_Message, thread4Msg);

    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);
    pthread_join(thread4, NULL);

    return 0;
}

解决方案

您正在尝试设置未初始化的线程的相似性.

好的，让我给您更多信息:

不要混合使用线程句柄(存储在pthread_t变量中的东西)及其表示的内容(在某个地方运行的执行线程).您试图做的是使用需要线程对象的API在启动之前设置线程的属性.碰巧pthread_create会创建对象并同时开始执行，因此尝试使用pthread_setaffinity_np并不是正确的方法(如果您想更改当前正在运行的线程).

但是... pthread_create有一个属性参数(您正在向其传递NULL).这是存储有关如何创建线程的信息.

亲和力是您可以通过该参数设置的属性之一.请参见 pthread_attr_init 和 pthread_attr_setaffinity_np

I have 4 threads, and I am trying to set thread 1 to run on CPU 1, thread 2 on CPU 2, etc. However, when I run my code below, the affinity masks are returning the correct values, but when I do a sched_getcpu() on the threads, they all return that they are running on CPU 4.

Anybody know what my problem here is?

Thanks in advance!

#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <sched.h>
#include <errno.h>

void *pthread_Message(char *message)
{
    printf("%s is running on CPU %d\n", message, sched_getcpu());
}

int main()
{
    pthread_t thread1, thread2, thread3, thread4;
    pthread_t threadArray[4];
    cpu_set_t cpu1, cpu2, cpu3, cpu4;
    char *thread1Msg = "Thread 1";
    char *thread2Msg = "Thread 2";
    char *thread3Msg = "Thread 3";
    char *thread4Msg = "Thread 4";
    int thread1Create, thread2Create, thread3Create, thread4Create, i, temp;

    CPU_ZERO(&cpu1);
    CPU_SET(1, &cpu1);
    temp = pthread_setaffinity_np(thread1, sizeof(cpu_set_t), &cpu1);
    printf("Set returned by pthread_getaffinity_np() contained:\n");
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu1))
            printf("CPU1: CPU %d\n", i);

    CPU_ZERO(&cpu2);
    CPU_SET(2, &cpu2);
    temp = pthread_setaffinity_np(thread2, sizeof(cpu_set_t), &cpu2);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu2))
            printf("CPU2: CPU %d\n", i);

    CPU_ZERO(&cpu3);
    CPU_SET(3, &cpu3);
    temp = pthread_setaffinity_np(thread3, sizeof(cpu_set_t), &cpu3);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu3))
            printf("CPU3: CPU %d\n", i);

    CPU_ZERO(&cpu4);
    CPU_SET(4, &cpu4);
    temp = pthread_setaffinity_np(thread4, sizeof(cpu_set_t), &cpu4);
    for (i = 0; i < CPU_SETSIZE; i++)
        if (CPU_ISSET(i, &cpu4))
            printf("CPU4: CPU %d\n", i);

    thread1Create = pthread_create(&thread1, NULL, (void *)pthread_Message, thread1Msg);
    thread2Create = pthread_create(&thread2, NULL, (void *)pthread_Message, thread2Msg);
    thread3Create = pthread_create(&thread3, NULL, (void *)pthread_Message, thread3Msg);
    thread4Create = pthread_create(&thread4, NULL, (void *)pthread_Message, thread4Msg);

    pthread_join(thread1, NULL);
    pthread_join(thread2, NULL);
    pthread_join(thread3, NULL);
    pthread_join(thread4, NULL);

    return 0;
}

解决方案

You're trying to set the affinity of threads that you did not initialize.

Edit: Ok, let me give you some more info:

Don't mix thread handles (the thing you store in the pthread_t variable) and what they represent (a thread of execution that runs somewhere). What you were trying to do is to set a property of a thread before it starts, with an API that requires the thread object. As it happens pthread_create creates the object and starts the execution at the same time, so trying to use pthread_setaffinity_np is not the right way to go (this is useful if you want to change the affinity of a currently running thread).

But... pthread_create has an attribute parameter (you're passing NULL to it). This is storing the information of how you want the thread to be created.

Affinity is one of the attributes you can set through that parameter. See the man-page documentation for pthread_attr_init and pthread_attr_setaffinity_np for how exactly

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