Linux Free Memory Calculation

Free memory can be seen from the "free" command output:

$ free
             total       used       free     shared    buffers     cached
Mem:       2066184    1420776     644600          0      49140     647396
-/+ buffers/cache:     724240    1341136
Swap:      2097144        112    2048136

Real free memory = free + buffers + cached

To clean up buffers and cached memory, use defrag_mem:

$ gcc -o defrag_mem defrag_mem.c
$ ./defrag_mem 1500M
$ free
             total       used       free     shared    buffers     cached
Mem:       2066184     569576    1496608          0        592      70172
-/+ buffers/cache:     498812    1567372
Swap:      2097144     340812    1756332