Clean up buffer and cached memory by defrag_mem

This command is very useful to free buffers when you face lack of memory issue. Free memory can be seen from the output of common linux command “free”:

[root]# free
total       used       free     shared    buffers     cached
Mem:       1033972     987192      46780          0     159204     309176
-/+ buffers/cache:     518812     515160
Swap:      4192956         68    4192888

Here we can see that free memory calculation formula is:

Real free memory = free + buffers + cached
To clean up buffers and cached memory, use defrag_mem:

[root]# gcc -o defrag_mem
[root]# ./defrag_mem 500M

[root]# free
total       used       free     shared    buffers     cached
Mem:       1033972     482504     551468          0        612       7760
-/+ buffers/cache:     474132     559840
Swap:      4192956     112964    4079992