By default, there are various caches like RAM, swap space, Buffer, etc.

Those cache will be saved in /proc/sys/vm/drop_caches

To clear, run the below commands:

# sync; echo 1 > /proc/sys/vm/drop_caches                            [For Pagecache]
# sync; echo 2 > /proc/sys/vm/drop_caches                            [For inodes]
# sync; echo 3 > /proc/sys/vm/drop_caches                            [For both]
# swapoff -a                                                         [For swap cache]