Swap

Swap

Swap usage can lead to performance degradation of your server. So we highly recommend to disable swap space and increase the memory.

How to disable

root@vmsniff:~# swapoff -a

Then edit the /etc/fstab file and comment out the swap lines. E.g.

proc            /proc           proc    defaults        0       0
# / was on /dev/md0 during installation
UUID=17e56a9a-0f42-44ca-90e8-570315708def /               xfs     relatime        0       1
# swap was on /dev/sda2 during installation
#UUID=0a403f5e-0505-4055-a219-70217b6b74d1 none            swap    sw              0       0
# swap was on /dev/sdb2 during installation
#UUID=4cf42564-4339-42ed-b7ec-29644a3085f1 none            swap    sw              0       0

Note: use dmesg (or dmeg -T) command to ensure there is no service crashing because of no ram free.

How to configure

Most distributions have set by default to use swap when Ram usage exceeds 40% check your swappiness values with

cat /pro/sys/vm/swappiness

(the value 60 here means to use the swap only when there is less then 60% of free RAM)

You can change it in a run-time,effect is instant after disable/enable the swap(but not persists restart of a server)

echo '5' > /pro/sys/vm/swappiness

You can set the value permanent by adding the line at end of /etc/sysctl.conf

vm.swappiness=5

(0 value means to use swap only when there is no Ram free)

Make swap empty

swapoff -a
swapon -a