The swappiness parameter controls how aggressively the kernel swaps processes out of physical memory and onto the swap disk.
When swappiness=0, the server kernel avoids swapping programs out of physical memory for as long as possible. When swappiness=100, the server aggressively swaps processes out of physical memory.
The Ubuntu default is 60 at time of writing. You can check this through the following command:
cat /proc/sys/vm/swappiness
We want to change this value, and lower it to (typically) 20, as swap space is much slower than physical memory and involves expensive I/O writes. Also, the constant swapping heats up the hard drive and lowers its life expectancy.
You can change this value temporarily ( till the next reboot ) through the following command:
sudo sysctl vm.swappiness=20
To make this change permanent, we’ll need to edit /etc/sysctl.conf
gksudo gedit /etc/sysctl.conf
and add or modify this parameter.
vm.swappiness=20
If this parameter does not exist in the file, add it at the end. You’ll need to reboot to have this change take effect. Authoritative source for this tip is the Ubuntu Community Documentation Swap FAQ.
Open a terminal, and run the free command to check how much swap space is being used after implementing this tweak.
Sample output on my system after the tweak:
$free total used free shared buffers cached Mem: 1017416 1001440 15976 0 14304 233252 -/+ buffers/cache: 753884 263532 Swap: 1004020 133460 870560
