Difference between revisions of "Swap"
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== Swap == | == Swap == | ||
| − | Swap usage | + | 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=== | ===How to disable=== | ||
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#UUID=4cf42564-4339-42ed-b7ec-29644a3085f1 none swap sw 0 0 | #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. | |
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Latest revision as of 14:22, 21 October 2021
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.