Swap

Swap

Swap usage leads to performance degradation of your server. So we highly recommend to configure swap space properly or disable it entirely

How to configure

Most of distribution's default settings for swap is to use the swap when Ram usage exceeds 40% check your swappiness value with

cat /proc/sys/vm/swappiness

(the value 60 here means to start to use the swap when there is less then 60% of free RAM - this not makes sense for realtime services)

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' > /proc/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

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.