How to clear cache memory(RAM) in linux

Clear cache memory.

You can use the command given below to clear the pagecache
echo 1 > /proc/sys/vm/drop_caches

To  free dentries and inodes, you can use the command
echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:
echo 3 > /proc/sys/vm/drop_caches