SHELL

centos 6 vm.min_free_kbytes

# clear page cache (above type 2 and 3)
$ echo 1 > /proc/sys/vm/drop_caches

# clear slab cache (above type 4)
$ echo 2 > /proc/sys/vm/drop_caches

# clear page and slab cache (types 2,3,4)
$ echo 3 > /proc/sys/vm/drop_caches