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What is swappiness in Linux Memory Management and how do we configure that ?

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What is swappiness in Linux Memory Management and how do we configure that ?
posted Oct 13, 2015 by Mohammed Hussain

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The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk. Because disks are much slower than RAM, this can lead to slower response times for system and applications if processes are too aggressively moved out of memory.

swappiness can have a value of between 0 and 100

swappiness=0 tells the kernel to avoid swapping processes out of physical memory for as long as possible

swappiness=100 tells the kernel to aggressively swap processes out of physical memory and move them to swap cache

The default setting in Redhat/Ubuntu based Linux distros is swappiness=60. Reducing the default value of swappiness will probably improve overall performance for a typical Ubuntu desktop installation.

~$ cat /proc/sys/vm/swappiness
60

If we have enough RAM, we can turn that down to 10 or 15. The swap file will then only be used when the 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

sysctl vm.swappiness=10

We can also clear swap by running swapoff -a and then swapon -a as root instead of rebooting to achieve the same effect.

answer Oct 30, 2015 by Manikandan J
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