system | page cache

Clearing Cache

Synchronize cached writes to persistent storage:

sudo sync

Free pagecache:

sudo sh -c 'echo 1 >/proc/sys/vm/drop_caches'

Free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

Free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

Add to crontab (every 50 minutes):

sudo crontab -e

*/50 * * * * sync && sleep 5 && echo 1 >/proc/sys/vm/drop_caches

Reference: stackexchange