CPU亲和性掩码（将线程放置在不同的CPU上）

Question

CPU亲和性掩码（将线程放置在不同的CPU上）

linuxmultithreadingpthreadsparallel-processing

19

我有4个线程，我想把第1个线程设置为在CPU 1上运行，第2个线程在CPU 2上运行，以此类推。但是，当我运行下面的代码时，亲和力掩码返回了正确的值，但是当我对线程进行sched_getcpu()操作时，它们都返回正在CPU 4上运行。

有人知道这里的问题是什么吗？

先感谢一下！

#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;
}

- hwrd

3个回答

5

以下就是你所需要的内容。虽然回答有点晚，但对于其他人可能会有帮助。

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

#include <unistd.h>

int   getNumberOfCpus( void )
{
    long nprocs       = -1;
    long nprocs_max   = -1;

    # ifdef _SC_NPROCESSORS_ONLN
    nprocs = sysconf( _SC_NPROCESSORS_ONLN );
    if ( nprocs < 1 )
    {
        //std::cout << "Could not determine number of CPUs on line. Error is  " << strerror( errno ) << std::endl;
        return 0;
    }

    nprocs_max = sysconf( _SC_NPROCESSORS_CONF );

    if ( nprocs_max < 1 )
    {
        //std::cout << "Could not determine number of CPUs in host. Error is  " << strerror( errno ) << std::endl;
        return 0;
    }

    //std::cout << nprocs < " of " << nprocs_max << " online" << std::endl;
    return nprocs; 

#else
    //std::cout << "Could not determine number of CPUs" << std::endl;
    return 0;
#endif
}

void *pthread_Message( void *ptr )
{
    sleep(10);
    char *message;
    message = (char *) ptr;
    printf("%s \n", message);
    cpu_set_t      l_cpuSet;
    int            l_maxCpus;
    int            j;
    unsigned long  l_cpuBitMask;

    CPU_ZERO( &l_cpuSet );
    printf("get affinity %d\n",pthread_getaffinity_np(pthread_self()  , sizeof( cpu_set_t ), &l_cpuSet ));
    // printf("cpuset %d\n",l_cpuSet);
    printf (" thread id %u\n", pthread_self());      

    if ( pthread_getaffinity_np(pthread_self()  , sizeof( cpu_set_t ), &l_cpuSet ) == 0 )
        for (int i = 0; i < 4; i++)
            if (CPU_ISSET(i, &l_cpuSet))
                printf("XXXCPU: CPU %d\n", i);
    for (long i=0; i< 10000000000; ++i);
}

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

    thread1Create = pthread_create(&thread1, NULL, &pthread_Message, (void*)thread1Msg);
    sleep(1);
    thread2Create = pthread_create(&thread2, NULL, &pthread_Message, (void*)thread2Msg);
    sleep(1);
    thread3Create = pthread_create(&thread3, NULL, &pthread_Message, (void*)thread3Msg);
    sleep(1);
    thread4Create = pthread_create(&thread4, NULL, &pthread_Message, (void*)thread4Msg);


    CPU_ZERO(&cpu1);
    CPU_SET(0, &cpu1);
    temp = pthread_setaffinity_np(thread1, sizeof(cpu_set_t), &cpu1);
    printf("setaffinity=%d\n", temp);
    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(1, &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(2, &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(3, &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);

    // pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpu1);



    // pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpu1);

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

    return 0;
}

- John Samson

2

我认为最简单的方法是将CPU掩码作为参数传递给每个线程，并让线程自己请求所需的亲和力，就像这个例子中的pthread_setaffinity_np(3)一样。

- Nikolai Fetissov

我如何知道哪个线程（在我的情况下，thread1、thread2、thread3或thread4）正在调用pthread_self()函数？ - hwrd

我认为Bahbar已经回答了这个问题 - 使用线程函数参数，它可以指向任何东西，比如一个包含线程请求的亲和掩码的结构体。但要小心，不要在工作线程之间共享相同的结构实例。 - Nikolai Fetissov

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Bahbar · Accepted Answer

您正在尝试设置未初始化的线程的关联性。

编辑：好的，让我给您更多信息：

不要混淆线程句柄（存储在pthread_t变量中的东西）和它们所代表的内容（在某个地方运行的执行线程）。您尝试做的是在启动线程之前设置线程的属性，但该API需要线程对象。实际上，pthread_create会创建对象并同时开始执行，因此尝试使用 pthread_setaffinity_np 不是正确的方法（如果要更改当前正在运行的线程的关联性，则这很有用）。

但是... pthread_create 有一个属性参数（您将其传递为NULL）。这存储了您希望如何创建线程的信息。

关联性是您可以通过该参数设置的属性之一。有关详细信息，请参见 pthread_attr_init 和 pthread_attr_setaffinity_np 的手册文档。