The Linux kernel provides a tweakable setting that controls how often the swap file is used, called swappiness.
A swappiness setting of zero means that the disk will be avoided unless absolutely necessary (you run out of memory), while a swappiness setting of 100 means that programs will be swapped to disk almost instantly.
Ubuntu 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 own system’s swappiness value by running:
one@onezero:~$ cat /proc/sys/vm/swappiness 60
As I have 4 GB of RAM, so I’d like to turn that down to 10 or 15. The swap file will then only be used when my RAM usage is around 80 or 90 percent. To change the system swappiness value, open
/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
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@onezero:/home/one# 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