hyper-v + min ubuntu server 高内存占用，开机内存占用 90M，闲置 20 分钟内存占用变成了 579M，又找不到占用进程，什么情况？

min ubuntu server 14.04 空白系统，开机内存占用 90M ，闲置 20 分钟内存占用变成了 579M ， top 又看不到什么程序占用的...

这是什么情况？ hyper-v 动态内存惹的祸？

物理机系统是 win 10
虚拟机是 min ubuntu server 14.04
```
gamexg@min-userver1:~$ free -h
total used free shared buffers cached
Mem: 985M 666M 318M 368K 9.3M 79M
-/+ buffers/cache: 578M 406M
Swap: 1.0G 0B 1.0G

top - 13:49:22 up 18 min, 1 user, load average: 0.00, 0.01, 0.02
Tasks: 98 total, 1 running, 97 sleeping, 0 stopped, 0 zombie
%Cpu (s ): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem: 1008708 total, 684396 used, 324312 free, 9636 buffers
KiB Swap: 1045500 total, 0 used, 1045500 free. 80956 cached Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

689 root 20 0 259728 17328 12640 S 0.0 1.7 0:00.56 docker

651 root 20 0 629780 17092 7936 S 0.0 1.7 0:01.53 daomonit

986 root 20 0 469272 12456 7716 S 0.0 1.2 0:00.34 daotunnel

942 root 20 0 95092 6084 5148 S 0.0 0.6 0:00.01 sshd

955 gamexg 20 0 24612 5624 3384 S 0.0 0.6 0:00.04 bash

790 root 20 0 61372 5344 4664 S 0.0 0.5 0:00.00 sshd

727 syslog 20 0 255848 5024 2448 S 0.0 0.5 0:00.00 rsyslogd

562 root 20 0 10236 4464 2168 S 0.0 0.4 0:00.00 dhclient

1 root 20 0 33512 4056 2724 S 0.0 0.4 0:00.70 init

336 root 20 0 49704 3548 2892 S 0.0 0.4 0:00.03 systemd-udevd

954 gamexg 20 0 95092 3392 2468 S 0.0 0.3 0:00.06 sshd

1049 gamexg 20 0 24412 2836 2416 R 0.0 0.3 0:00.01 top

802 root 20 0 23660 2160 1944 S 0.0 0.2 0:00.00 cron

770 root 20 0 17504 2156 2004 S 0.0 0.2 0:00.00 getty

767 root 20 0 17500 2152 2004 S 0.0 0.2 0:00.00 getty

763 root 20 0 17504 2064 1900 S 0.0 0.2 0:00.00 getty

762 root 20 0 17504 2060 1900 S 0.0 0.2 0:00.00 getty

768 root 20 0 17504 2060 1900 S 0.0 0.2 0:00.00 getty

862 root 20 0 17500 2044 1900 S 0.0 0.2 0:00.00 getty

800 root 20 0 15412 1820 1416 S 0.0 0.2 0:00.00 upstart-file-br

493 root 20 0 15264 1788 1520 S 0.0 0.2 0:00.04 upstart-socket-

331 root 20 0 19480 180 0 S 0.0 0.0 0:00.09 upstart-udev-br

2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd

3 root 20 0 0 0 0 S 0.0 0.0 0:00.02 ksoftirqd/0

5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H

7 root 20 0 0 0 0 S 0.0 0.0 0:00.09 rcu_sched