Linux编程之《进程/线程绑定CPU》

Intro
-----

通常我们在编写服务器代码时，可以通过将当前进程绑定到固定的CPU核心或者线程绑定到固定的CPU核心来提高系统调度程序的效率来提高程序执行的效率，下面将完整代码贴上。
```
/************************************************
* 该例程讲解了进程、线程绑定到固定的cpu核心上运行
* 来提高程序运行效率
************************************************/
#include <unistd.h>
#ifndef __USE_GNU
#define __USE_GNU // 为了使用SET_SET()等宏定义，但unistd.h里面好像已经定义了
#endif
#include <sched.h>
#include <pthread.h>
#include <stdio.h>
#include <vector>

unsigned int systemCPUNum()
{
// _SC_NPROCESSORS_CONF的值为CPU个数，基于0开始编号
return sysconf(_SC_NPROCESSORS_CONF);
}

bool currentProcessAffinity(std::vector<unsigned int>& runningCPUVector)
{
cpu_set_t cpuSet;

// 清空一个CPU集合
CPU_ZERO(&cpuSet);

// 得到指定进程ID绑定到哪个CPU
int ret = sched_getaffinity(0, // 0代表当前进程
sizeof(cpuSet),
&cpuSet);
if (ret < 0)
{
return false;
}

unsigned int cpuNum = systemCPUNum();
runningCPUVector.clear();
for (unsigned int i = 0; i < cpuNum; ++i)
{
// 检查一个CPU号是否在一个集合中
if (CPU_ISSET(i, &cpuSet))
{
runningCPUVector.push_back(i);
}
}

return true;
}

bool setCurrentProcessAffinity(const std::vector<unsigned int>& needBindCPUVector)
{
cpu_set_t cpuSet;

// 清空一个CPU集合
CPU_ZERO(&cpuSet);

for (auto& iter : needBindCPUVector)
{
CPU_SET(iter, &cpuSet);
}

// 将指定进程ID绑定到CPU
int ret = sched_setaffinity(0, // 0代表当前进程
sizeof(cpuSet),
&cpuSet);
if (ret < 0)
{
return false;
}

return true;
}

bool currentThreadAffinity(std::vector<unsigned int>& runningCPUVector)
{
cpu_set_t cpuSet;

// 清空一个CPU集合
CPU_ZERO(&cpuSet);

// 得到指定线程ID绑定到哪个CPU
int ret = pthread_getaffinity_np(pthread_self(),
sizeof(cpuSet),
&cpuSet);
if (ret < 0)
{
return false;
}

unsigned int cpuNum = systemCPUNum();
runningCPUVector.clear();
for (unsigned int i = 0; i < cpuNum; ++i)
{
// 检查一个CPU号是否在一个集合中
if (CPU_ISSET(i, &cpuSet))
{
runningCPUVector.push_back(i);
}
}

return true;
}

bool setCurrentThreadAffinity(const std::vector<unsigned int>& needBindCPUVector)
{
cpu_set_t cpuSet;

// 清空一个CPU集合
CPU_ZERO(&cpuSet);

for (auto& iter : needBindCPUVector)
{
CPU_SET(iter, &cpuSet);
}

// 将指定线程ID绑定到CPU
int ret = pthread_setaffinity_np(pthread_self(),
sizeof(cpuSet),
&cpuSet);
if (ret < 0)
{
return false;
}

return true;
}

int main()
{
printf("*****Process bind CPU sample*****\n");
unsigned int cpuNum = systemCPUNum();
printf("Current system has %u CPU(s)\n", cpuNum);

std::vector<unsigned int> runningCPUVector;
if (!currentProcessAffinity(runningCPUVector))
{
printf("Get current process was bound witch CPU failed\n");
return 1;
}

for (auto& iter : runningCPUVector)
{
printf("Current process is running at %u CPU\n", iter);
}

std::vector<unsigned int> needBindCPUVector {0, 2};
if (!setCurrentProcessAffinity(needBindCPUVector))
{
printf("Current process bind CPU failed\n");
return 1;
}

printf("Current process bind CPU success\n");

runningCPUVector.clear();
if (!currentProcessAffinity(runningCPUVector))
{
printf("Get current process was bound witch CPU failed\n");
return 1;
}

for (auto& iter : runningCPUVector)
{
printf("Current process is running at %u CPU\n", iter);
}

printf("\n*****Thread bind CPU sample*****\n");
runningCPUVector.clear();
if (!currentThreadAffinity(runningCPUVector))
{
printf("Get current thread was bound witch CPU failed\n");
return 1;
}

for (auto& iter : runningCPUVector)
{
printf("Thread %lu is running at %u CPU\n", pthread_self(), iter);
}

needBindCPUVector.clear();
needBindCPUVector.push_back(1);
if (!setCurrentThreadAffinity(needBindCPUVector))
{
printf("Current thread bind CPU failed\n");
return 1;
}

printf("Thread %lu bind CPU success\n", pthread_self());

runningCPUVector.clear();
if (!currentThreadAffinity(runningCPUVector))
{
printf("Get current thread was bound witch CPU failed\n");
return 1;
}

for (auto& iter : runningCPUVector)
{
printf("Thread %lu is running at %u CPU\n", pthread_self(), iter);
}

return 0;
}
```

程序执行的输出结果：
```
*****Process bind CPU sample*****
Current system has 4 CPU(s)
Current process is running at 0 CPU
Current process is running at 1 CPU
Current process is running at 2 CPU
Current process is running at 3 CPU
Current process bind CPU success
Current process is running at 0 CPU
Current process is running at 2 CPU

*****Thread bind CPU sample*****
Thread 139871129114432 is running at 0 CPU
Thread 139871129114432 is running at 2 CPU
Thread 139871129114432 bind CPU success
Thread 139871129114432 is running at 1 CPU
```

该例子的github地址：https://github.com/chxuan/samples/blob/master/BindCPU/BindCPU.cpp