Many users tend to worry when the free memory on a Linux system is very low. Especially when the system is barely active. What many don’t know is that this is normal behavior for Linux. It simply takes your free memory and caches it. This caching behavior makes subsequent memory allocations much faster. So it improves performance overall.

However, if you really really need to flush the cache and buffers, you can run the following two commands on the shell as root:

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.

That’s all folks. I hope you enjoyed this one.