How do I monitor Linux CPU but not memory?

FYI, we just put in a feature request to disable auto-discovery of "shared memory" and "cached memory" from Linux systems.  Please upvote if you find this feature request useful.

Link: thwack.solarwinds.com/.../inhibit-the-auto-discovery-of-cached-memory-and-shared-memory-in-linux-systems

You need to read and digest the contents of : Help, Linux Ate my RAM! - and apologies if you already know this.

Once you do, then you need to create a custom poller for your device(s) that does an "actually in use" memory calculation. Then you apply the poller to the relevant nodes **, and then you can monitor both CPU and RAM quite happily.

** I have found one poller per manufacturer seems to work - so all our Fortinets have one poller for this, but our Checkpoints need a different one, as do F5's, etc ...

You'll need to know the relevant OIDs for the device in question - as a minimum you will need the OIDs for CPU and then the OIDs for 'System Memory Usage' [fgSysMemUsage] and ' System Memory Capacity' [fgSysMemCapacity] and then you need to do a calculation - in the case of a Fortinet that calculation would look like:

Truncate(([fgSysMemCapacity] * 1024) * ([fgSysMemUsage] / 100))

You can actually test this against a node as you build the poller and if you have SSH access you can run the equivalent memory command to confirm your results. The test would look like: 

The yellow highlight is the %age of RAM in actual use at that time of the test.

Hope this helps - any questions please shout.