/proc/$pid可以看到一个进程的很多信息，比如查看mongo的limit
[admin@server7 ~]$ cat /proc/27640/limits
| Limit | Soft Limit | Hard Limit | Units |
| Max cpu time | unlimited | unlimited | seconds |
| Max file size | unlimited | unlimited | bytes |
| Max data size | unlimited | unlimited | bytes |
| Max stack size | 10485760 | unlimited | bytes |
| Max core file size | 0 | unlimited | bytes |
| Max resident set | unlimited | unlimited | bytes |
| Max processes | 270336 | 270336 | processes |
| Max open files | 65535 | 65535 | bytes |
| Max address space | unlimited | unlimited | bytes |
| Max file locks | unlimited | unlimited | locks |
| Max pending signals | 270336 | 270336 | signals |
| Max msgqueue size | 819200 | 819200 | bytes |