Debug_high_cpu_loading

追查问题，主要是在：

浮现问题
缩小范围
猜测，修正及验证

我们这里使用如下测试代码演示：

#include <stdio.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <unistd.h>
#define MAX_MONITOR_FILES 4

void main()
{
  int e_fd, fd;
  struct epoll_event event, rdy_event[MAX_MONITOR_FILES];

  if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
      perror("socket");
      goto out1;
  }

  if ((e_fd = epoll_create(MAX_MONITOR_FILES)) == -1) {
    perror("epoll_create");
    goto out2;
  }

  event.events = EPOLLIN;
  if((epoll_ctl(e_fd, EPOLL_CTL_ADD, fd, &event)) == -1) {
    perror("epoll_ctl");
    goto out3;
  }

  int n, j;
  while(1) {
    n = epoll_wait(e_fd, rdy_event, MAX_MONITOR_FILES, 0);
    if(n == -1) {
      perror("epoll_wait");
    }else if(n == 0) {
      //timeout, skip
    }

    for(j=0; j<n; j++) {
      //read it out
    }
  }

out3:
        close(e_fd);
out2:
        close(fd);
out1:
        return;
}