Configure Swapiness in Linux

Setting swapiness means that virtual swap memory is not used until the physical memory gets full. To avoid this you can set swapiness value.

Linux system comes with a default of 60, meaning that the swap file will be used fairly often if the memory usage is around half of my RAM.


You can check your system's swappiness value by running:

[root@test ~]# cat /proc/sys/vm/swappiness
60

So If i have 4 GB of RAM, and I like to turn that down to 10 or 15. The swap file will then only be used when my RAM usage is around 85 or 90 percent.

To change the system swappiness value

vim /etc/sysctl.conf as root. Then, change or add this line to the file:

vm.swappiness = 10

Reboot for the change to take effect

You can also change the value while your system is still running

sysctl vm.swappiness=10

You can also clear your swap by running swapoff -a and then swapon -a as root instead of rebooting to achieve the same effect.

To calculate your swap Formula

free -m (total) / 100 = A

A * 10


[root@test ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          3950       2262       1687          0        407        952
-/+ buffers/cache:        903       3047
Swap:         1953          0       1953

    so total is 3950 / 100 = 39.5 * 10 = 395

It means that when 10 % 395 MB of ram left, then it start using swapiness.