linux - 如何在 Linux 中只释放缓冲区缓存

Question

我知道Linux中有页缓存和缓冲区缓存。页缓存用于文件系统，缓冲区缓存用于设备。

释放页面缓存:

echo 1 > /proc/sys/vm/drop_caches

释放 dentry 和 inode:

echo 2 > /proc/sys/vm/drop_caches

释放页面缓存、目录项和 inode :

echo 3 > /proc/sys/vm/drop_caches 

我的问题:

drop_caches 是否覆盖了缓冲区缓存？

如果没有，那么有没有一种方法可以只释放缓冲区缓存，而使页面缓存仍然被缓存？

如果没有，为什么没有必要或不可能？

Answer 1

Ans:-    

sync; echo 3 > /proc/sys/vm/drop_caches

Here’s the output of free before and after running the above command.

Before

# free -m
             total       used       free     shared    buffers     cached
Mem:           502        487         15          0         15        170
-/+ buffers/cache:        301        201
Swap:         3153        375       2777
After

# free -m
             total       used       free     shared    buffers     cached
Mem:           502        345        157          0          1         44
-/+ buffers/cache:        300        202
As you can see the highlighted numbers, the buffers and cached values have dropped significantly after I ran the command. Again, this is not necessary. In fact, it’s not recommended at all but there it is if you’re curious to know.