Swappiness

Swappiness is a Linux kernel parameter that controls the relative weight given to swapping out runtime memory, as opposed to dropping pages from the system page cache. Swappiness can be set to values between 0 and 100 inclusive. A low value causes the kernel to avoid swapping, a higher value causes the kernel to try to use swap space. The default value is 60; setting it higher will increase performance of "hot" processes at the cost of making a return to inactive "cold" ones take a long pause, while setting it lower (even 0) may decrease response latency. Systems with more than adequate RAM for any expected task may want to drastically lower the setting.

With kernel version 3.5 and over, as well as kernel version 2.6.32-303 and over, it is likely better to use 1 for cases where 0 used to be optimal.

To temporarily set the swappiness in Linux, write the desired value (e.g. 10) to /proc/sys/vm/swappiness using the following command, running as root user:

# Set the swappiness value as root echo 10 > /proc/sys/vm/swappiness # Alternatively, run this sysctl -w vm.swappiness=10 # Verify the change cat /proc/sys/vm/swappiness 10 # Alternatively, verify the change sysctl vm.swappiness vm.swappiness = 10

Permanent changes are made in /etc/sysctl.conf via the following configuration line (inserted, if not present):

vm.swappiness = 10