Drop cached memory

drop_memcache.sh

#!/bin/bash
#
# Writing to this will cause the kernel to
# free pagecache, dentries and inodes.
# This causes that memory to become free.
#
# non-destructive & safe for production:
# ref: https://www.kernel.org/doc/Documentation/sysctl/vm.txt

freebefore=`free -k | awk '/^Mem:/{print $4}'`

# need to sync first
sync
echo 3 > /proc/sys/vm/drop_caches

freeafter=`free -k | awk '/^Mem:/{print $4}'`

freekb=`expr $freeafter - $freebefore`
let freemb=($freekb/1024)

echo "freed $freekb kilobytes ($freemb MB)"