How RAM metrics works?

maciox · December 17, 2024, 1:37pm

Hey, I have some questions about RAM metrics, especially about percentage RAM usage and total/free/used RAM.

Why on the second chart Total RAM is decreasing? I have total 192 GB RAM and now it shows only ~140.
What will happen with the second chart if my percentage RAM usage will be like ~90%? Looking at the second chart it looks like there are almost no RAM.
What about available RAM? Why there is only free RAM on second chart?

Sorry for so much questions but I’m pretty new in monitoring services, thanks for your responses!

dahag-mm · February 13, 2025, 4:26pm

I have the same issue with a virtual machine. I double checked that it doesn’t have dynamic memory enabled on the hypervisor.

Here’s the total RAM that changes all the time:

However at the same time RAM + Swap is constant:

The VM actually has 8GB RAM and 4GB Swap. There might be an inaccuracy because of GB vs GiB, but that inaccuracy should be constant.

dahag-mm · February 13, 2025, 4:31pm

grep MemTotal /proc/meminfo omits a constant and correct value, so this seems to me like a bug in Checkmk.

dahag-mm · February 13, 2025, 4:45pm

When I use the free -h and add together used and free, I get about the same that Checkmk reports as “total”, but it’s missing the columns shared, buff/cache and available.

Example from other server than the charts above.

$ free -h
               total        used        free      shared  buff/cache   available
Mem:            11Gi       5.1Gi       3.3Gi       200Mi       3.3Gi       6.1Gi

dahag-mm · February 18, 2025, 8:20am

That value is also constant over several days.

dahag-mm · May 6, 2025, 10:23am

This has been fixed in version 2.3.0p31.

martin.hirschvogel · May 7, 2025, 6:57am

And in 2.4, the order of entries also will make more sense: