一、如下所示，内存cache大

ubuntu@VM-10-13-ubuntu:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881      15441        439          2        157       8161
-/+ buffers/cache:       7122       8758
Swap:            0          0          0

二、清理cache

1. 执行同步

sudo sync

2. 清理cache

ubuntu@VM-10-13-ubuntu:~$ cat /proc/sys/vm/drop_caches
0

ubuntu@VM-10-13-ubuntu:~$ sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'

ubuntu@VM-10-13-ubuntu:~$ cat /proc/sys/vm/drop_caches
3

3. 观察结果

ubuntu@VM-10-13-ubuntu:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881       6697       9183          2          4         73
-/+ buffers/cache:       6618       9262
Swap:            0          0          0

附

ubuntu@VM-4-13-ubuntu:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881      15453        427          1        141      13421
-/+ buffers/cache:       1889      13991
Swap:            0          0          0
ubuntu@VM-4-13-ubuntu:~$ sudo sync 
ubuntu@VM-4-13-ubuntu:~$ sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'
ubuntu@VM-4-13-ubuntu:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881       1746      14134          1          4         57
-/+ buffers/cache:       1684      14196
Swap:            0          0          0

ubuntu@work1:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881      15423        457          2        138       8184
-/+ buffers/cache:       7100       8780
Swap:            0          0          0
ubuntu@work1:~$ sudo sync
ubuntu@work1:~$ sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'
ubuntu@work1:~$ free -m
             total       used       free     shared    buffers     cached
Mem:         15881       6643       9237          2          1         53
-/+ buffers/cache:       6589       9292
Swap:            0          0          0

参考文档

https://zhuanlan.zhihu.com/p/95813254
https://www.cnblogs.com/hellokitty2/p/10088042.html