nginx worker_processes 参数设置疑问

CentOS release 6.5 (Final) nginx/1.6.2

worker_processes auto;

ps -ef | grep nginx 进程的情况

root      1100     1  3 18:52 ?        00:01:46 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf      
nginx    31829  1100  0 19:38 ?        00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
nginx    31832  1100  0 19:38 ?        00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
nginx    31833  1100  0 19:38 ?        00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
root     31834  1100  0 19:38 ?        00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf

这个明显不正常，当然也不能正常提供http服务

worker_processes 1;

进程情况

root     24967     1  0 Nov19 ?        00:00:00 nginx: master process /usr/sbin/nginx -c /etc/nginx/nginx.conf
nginx    24968 24967  0 Nov19 ?        00:00:00 nginx: worker process

出现这个问题大概什么原因， 谁遇到过呢？