编写了一个样本C多线程程序,该程序运行10个线程,每个线程设置为高优先级和亲和性.在dell机器上编译并运行此代码,该机器具有16个内核,运行centos 7( Linux内核 – 3.10.0-229),禁用超线程.在我运行此代码之后,几秒钟内,我们的Linux机器变得没有响应,从某种意义上说,如果我打开Eclipse编辑器,保存文件或在vi编辑器中保存文件,那些应用程序就会挂起.有趣的是,一旦我停止了这个程序/过程,那么所有其他应用程序将从他们停止的地方恢复.如果我从这10个线程中删除优先级,我也不会看到这个问题.

问题：

1)在16个内核中,6个内核仍留在机器上(cpu使用情况显示,cpu执行了62.9％的用户空间,并且闲置了37.1％.有趣的是内核空间中0％的cpu使用率),所以理想情况下应该使用内核那6个内核处理其他应用程序,可能是其他应用程序无法运行的原因？如何在不引入睡眠/更改优先级的情况下解决此问题？

2)想知道更好的方法,除了在线程中引入睡眠/等待事件(由于内核上下文切换引入最小延迟)以实现并行性？

跑顶命令(顶部-H)：

%cpu(s):  62.9 us,0.0 sy,0.0 ni,37.1 id,0.0 wa,0.0 hi,0.0 si,0.0 st

1107 arun      rt   0   96748   1112    932 R 99.9  0.0   0:25.78 PthreadTest
1115 arun      rt   0   96748   1112    932 R 99.9  0.0   0:24.79 PthreadTest
1118 arun      rt   0   96748   1112    932 R 99.9  0.0   0:22.79 PthreadTest
1120 arun      rt   0   96748   1112    932 R 99.9  0.0   0:20.79 PthreadTest
1123 arun      rt   0   96748   1112    932 R 99.9  0.0   0:18.79 PthreadTest
1117 arun      rt   0   96748   1112    932 R 94.1  0.0   0:23.78 PthreadTest
1119 arun      rt   0   96748   1112    932 R 94.1  0.0   0:21.78 PthreadTest
1122 arun      rt   0   96748   1112    932 R 94.1  0.0   0:19.78 PthreadTest
1124 arun      rt   0   96748   1112    932 R 94.1  0.0   0:17.78 PthreadTest
1125 arun      rt   0   96748   1112    932 R 94.1  0.0   0:16.76 PthreadTest

代码如下：

#include <unistd.h>
#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define NUM_THREADS 10

void *PrintHello(void *threadid)
{
   long tid;
   tid = (long)threadid;

   cout << "Hello World! Thread ID," << tid << endl;
   while(true)
   {
        continue;
   }
   pthread_exit(NULL);
}

int main ()
{
   pthread_t threads[NUM_THREADS];
   pthread_attr_t  threads_attr[NUM_THREADS];
   struct sched_param     params;
   params.sched_priority = sched_get_priority_max(SCHED_FIFO);
   int rc;
   int i;
   int cpu_num = 0;

   for( i=0; i < NUM_THREADS; i++ ){

      cpu_set_t cpu;
      cpu_ZERO(&cpu);
      cpu_SET(cpu_num,&cpu);
      cout << "main() : creating thread," << i << "cpu_num : "<<cpu_num<<endl;
      pthread_attr_init(&threads_attr[i]);
      pthread_attr_setscope(&threads_attr[i],PTHREAD_SCOPE_SYSTEM);
      rc = pthread_create(&threads[i],NULL,PrintHello,(void *)i);
      if (rc){
         cout << "Error:unable to create thread," << rc << endl;
         exit(-1);
      }

      sleep(1);


      int ret = pthread_setaffinity_np(threads[i],sizeof(cpu_set_t),&cpu);
      if(ret == 0 && cpu_ISSET(cpu_num,&cpu))
      {
        cout << "Thread " << i << " affinity set " <<endl;
      }


      ret = pthread_setschedparam(threads[i],SCHED_FIFO,&params);
      if(ret == 0)
      {
        cout << "Thread " << i << " priority set " <<endl;
      }
      cpu_num++;
   }


// free attribute and wait for the other threads
   void *status;
   for( i=0; i < NUM_THREADS; i++ )
   {
        rc = pthread_join(threads[i],&status);
        if (rc){
            cout << "Error:unable to join," << rc << endl;
            exit(-1);
        }
        cout << "Main: completed thread id :" << i ;
        cout << "  exiting with status :" << status << endl;
   }

   pthread_exit(NULL);
}

编译：

g++ -std=c++14 -g -o PthreadTest busywait.cpp -lpthread