进程线程与cpu绑定

CPU Affinity


CPU亲合力就是指在Linux系统中能够将一个或多个进程绑定到一个或多个处理器上运行.
一个进程的CPU亲合力掩码决定了该进程将在哪个或哪几个CPU上运行.在一个多处理器系统中,设置CPU亲合力的掩码可能会获得更好的性能.
一个CPU的亲合力掩码用一个cpu_set_t结构体来表示一个CPU集合,下面的几个宏分别对这个掩码集进行操作:
CPU_ZERO() 清空一个集合
CPU_SET()与CPU_CLR()分别对将一个给定的CPU号加到一个集合或者从一个集合中去掉.
CPU_ISSET()检查一个CPU号是否在这个集合中.
其实这几个的用法与select()函数那几个调用差不多.
下面两个函数就是最主要的了:
sched_setaffinity(pid_t pid, unsigned int cpusetsize, cpu_set_t *mask)
该函数设置进程为pid的这个进程,让它运行在mask所设定的CPU上.如果pid的值为0,则表示指定的是当前进程,使当前进程运行在mask所设定的那些CPU上.第二个参数cpusetsize是


mask所指定的数的长度.通常设定为sizeof(cpu_set_t).如果当前pid所指定的CPU此时没有运行在mask所指定的任意一个CPU上,则该指定的进程会从其它CPU上迁移到mask的指定的


一个CPU上运行.
sched_getaffinity(pid_t pid, unsigned int cpusetsize, cpu_set_t *mask)

该函数获得pid所指示的进程的CPU位掩码,并将该掩码返回到mask所指向的结构中.即获得指定pid当前可以运行在哪些CPU上.同样,如果pid的值为0.也表示的是当前进程.

# define __CPU_SETSIZE  1024
# define __NCPUBITS     (8 * sizeof (__cpu_mask))

typedef unsigned long int __cpu_mask;

# define __CPUELT(cpu)  ((cpu) / __NCPUBITS)
# define __CPUMASK(cpu) ((__cpu_mask) 1 << ((cpu) % __NCPUBITS))

typedef struct
{
  __cpu_mask __bits[__CPU_SETSIZE / __NCPUBITS];
} cpu_set_t;

# define __CPU_ZERO(cpusetp) \
  do {                                                                        \
    unsigned int __i;                                                         \
    cpu_set_t *__arr = (cpusetp);                                             \
    for (__i = 0; __i < sizeof (cpu_set_t) / sizeof (__cpu_mask); ++__i)      \
      __arr->__bits[__i] = 0;                                                 \
  } while (0)
# define __CPU_SET(cpu, cpusetp) \
  ((cpusetp)->__bits[__CPUELT (cpu)] |= __CPUMASK (cpu))
# define __CPU_CLR(cpu, cpusetp) \
  ((cpusetp)->__bits[__CPUELT (cpu)] &= ~__CPUMASK (cpu))
# define __CPU_ISSET(cpu, cpusetp) \
  (((cpusetp)->__bits[__CPUELT (cpu)] & __CPUMASK (cpu)) != 0)

例子:

#include<stdlib.h>
#include<stdio.h>
#include<sys/types.h>
#include<sys/sysinfo.h>
#include<unistd.h>

#define __USE_GNU/*注意写法*/
#include<sched.h>
#include<ctype.h>
#include<string.h>

int main(int argc, char* argv[])
{
        int num = sysconf(_SC_NPROCESSORS_CONF);
        int created_thread = 0;
        int myid;
        int i;
        int j = 0;

        cpu_set_t mask;
        cpu_set_t get;

        if (argc != 2)
        {
                printf("usage : ./cpu num\n");
                exit(1);
        }

        myid = atoi(argv[1]);

        printf("system has %i processor(s). \n", num);

        CPU_ZERO(&mask);
        CPU_SET(myid, &mask);

        if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
        {
                printf("warning: could not set CPU affinity, continuing...\n");
        }
        while (1)
        {

                CPU_ZERO(&get);
                if (sched_getaffinity(0, sizeof(get), &get) == -1)
                {
                        printf("warning: cound not get cpu affinity, continuing...\n");
                }
                for (i = 0; i < num; i++)
                {
                        if (CPU_ISSET(i, &get))
                        {
                                printf("this process %d is running processor : %d\n",getpid(), i);
                        }
                }
        }
        return 0;
}

  与进程的情况相似，线程亲和性的设置和获取主要通过下面两个函数来实现：
    int pthread_setaffinity_np(pthread_t thread, size_t cpusetsize，
const cpu_set_t *cpuset);
    int pthread_getaffinity_np(pthread_t thread, size_t cpusetsize, 
cpu_set_t *cpuset);

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

void *myfun(void *arg)
{
    cpu_set_t mask;
    cpu_set_t get;
    char buf[256];
    int i;
    int j;
    int num = sysconf(_SC_NPROCESSORS_CONF);
    printf("system has %d processor(s)\n", num);

    for (i = 0; i < num; i++) {
        CPU_ZERO(&mask);
        CPU_SET(i, &mask);
        if (pthread_setaffinity_np(pthread_self(), sizeof(mask), &mask) < 0) {
            fprintf(stderr, "set thread affinity failed\n");
        }
        CPU_ZERO(&get);
        if (pthread_getaffinity_np(pthread_self(), sizeof(get), &get) < 0) {
            fprintf(stderr, "get thread affinity failed\n");
        }
        for (j = 0; j < num; j++) {
            if (CPU_ISSET(j, &get)) {
                printf("thread %d is running in processor %d\n", (int)pthread_self(), j);
            }
        }
        j = 0;
        while (j++ < 100000000) {
            memset(buf, 0, sizeof(buf));
        }
    }
    pthread_exit(NULL);
}

int main(int argc, char *argv[])
{
    pthread_t tid;
    if (pthread_create(&tid, NULL, (void *)myfun, NULL) != 0) {
        fprintf(stderr, "thread create failed\n");
        return -1;
    }
    pthread_join(tid, NULL);
    return 0;
}