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To change this value on the fly, you can execute the following command:
sudo sysctl vm.swappiness=30 
This method doesn't set 
swappiness
 permanently, however. When you execute that 
command, 
swappiness
 will immediately be set to the new value and your server will 
act accordingly. Once you reboot, though, the 
swappiness
 value will revert back to 
the default. To make the change permanent, open the following file with your text 
editor:
/etc/sysctl.conf 
A line in that file corresponding to 
swappiness
 will typically not be included by 
default, but you can add it manually. To do so, add a line such as the following to the 
end of the file and save it:
vm.swappiness = 30 
Changing this value is one of many techniques within the realm of performance 
tuning. While the default value of 
60
 is probably fine for most, there may be a 
situation where you're running a performance-minded application and can't afford 
to have it swap any more than it absolutely has to. In such a situation, you would 
try different values for 
swappiness
 and use whichever one works best during your 
performance tests.
In the next section, we'll take a look at another important metric to keep an eye on: 
load average. The load average gives us an idea of how busy the CPU(s) might be, so 
we can better understand how to tell when our server is overwhelmed and we may 
need to take action.