Resolved Warning: The swap usage status is critical!

[Azurel]

I received this plesk email today:

The swap usage status is critica!
The current value is 3.6 GiB.

My server have 128 GB RAM

Then why does he use "swap" so much?

#free -m

CentOS Linux 8.4.2105

EDIT:
I used

# swapoff -a && swapon -a

and now its 0K/4G
If anyone wants to do this as well, it may take time. With me almost 1 hour. In a second console window you can watch the swap as it decreases.

 

[mow]

that's normal, you can ignore that message as long as there's always enough "available", see also here: Question - increase swap partition on ubuntu 16 ff.

 

[Azurel]

I would not call it "normal". Swap is hard disk and it should not read almost 4GB of data from hard disk, instead it should be in RAM.
If there is RAM available, why does it use swap?

 

[mow]

There is RAM available, but there is very little RAM free because it's all used for buffers and cache. So the kernel swaps out stuff that has not been used for a while in favor of having more buffer/cache. You will only see zero swap usage if you have more RAM than the size of your file data set.

Check with vmstat. You will see that si and so are zero, swap usage is quasi-static.

 

[Azurel]

Thank you for your explanation.