Some times, you may notice that there is a lot of memory locked in CACHE
To remove the cached memory, login to the server as “root” and execute the below command
/bin/sync ; /bin/echo 3 > /proc/sys/vm/drop_caches
If you are using virtuozzo containers and get the below error, you may have to contact the Support Team of your Hosting Company to clear this as for VZ containers, the memory has to be cleared from the hardware node and not from the container (VPS).
bash: /proc/sys/vm/drop_caches: Permission denied