OPTIMIZE THE USE OF RAM for BETTER Performance on High Load Linux Server

Swapiness which is a kernel module that defines when linux has to start to write in the SWAP (an allocated space in the disk) to relieve the RAM.
It may seem obvious that with access times in milliseconds for Hard Disk and in nanoseconds for RAM, it is better to write in the RAM.

Swap Values are defined below   

vm.swappiness = 0 : Swapping will be activated urgently only to avoid out of memory condition.
vm.swappiness = 60 : This is the default value and means that from 40% of Ram occupancy, the kernel writes to the swap.
vm.swappiness = 10 : This what is recommended to improve performance.
vm.swappiness = 100 : The kernel will swap aggressively.

To see your swappiness setting :

cat /proc/sys/vm/swappiness
60
Let’s consider that we have a server having 156G of RAM. fixing the swappiness to 5 is enough since kernel will use swap only when the free RAM space is less or equal to 7.8G.

As root set the swappiness value:

echo 5 > /proc/sys/vm/swappiness

or alternatively, run:

sysctl -w vm.swappiness=5

Verify your changes:

cat /proc/sys/vm/swappiness
5

or:

sysctl vm.swappiness
vm.swappiness = 5

To change this value permanently edit /etc/sysctl.conf and modify (or add if not exist):

vm.swappiness = 5
apply modification:

sysctl -p
swappoff -a && swapon -a