With a lot of trial and error, I think I narrowed the issue down to a folder with 10 battery backup units in it. Have reset all of the check intervals and so far we’re back to normal. Will let this sit for a day or two as-is and see what happens, but for the most part cmc is hovering around 1-2% CPU usage currently.
There’s nothing exotic about the UPS units. 7 APC units with AP9631/AP9641 cards and 3 Eaton units with their Network-M2 card. CheckMK is just doing regular SNMP v3 checks on them.
If this holds steady, I’ll start to enable them one-by-one and see if it’s limited to a single host.