Swap usage control
Swappiness is a Linux kernel parameter which defines the balance between swap and memory usage. Swappiness takes a value between 0 and 100 to change the balance.
0 - swap only to avoid out of memory state.
100 - forced swap.
Display the current swappiness value:
# cat /proc/sys/vm/swappiness
Set swappiness value to 20:
# echo 20 >/proc/sys/vm/swappiness
You also can define the default value in /etc/sysctl.conf:
vm.swappiness = 30