I have had a Hubitat hub for several years. I started with a C7 and have done all my configuration there. Coming from SmartThings I migrated my WebCore pistons to my Hubitat hub. Last year I migrated to a C8 hub and started seeing Severe Hub Load warning with increasing frequency.
The things is I have barely changes my setup since my initial setup, i.e. no new Devices or Apps and I haven't seen any such problems on the C7 hub which has weaker hardware.
Why recent Software updates cause such issues on the Hub and am I the only one having this?
I had to disable some apps that were causing this but it still happens from time to time.
Check your past logs for errors, you can filter it by error and also warn in the menus.
Post screenshots of any errors in the logs.
Also check Logs > Device stats and App stats
Click show display settings and turn on all the settings.
Leave it sorted by % of busy and post a screenshot of both pages including the uptime header.
Also ge to this endpoint for your hub and post the top page of results http:/YOUR.HUB.IP/hub/advanced/freeOSMemoryHistory
I checked those page and removed stuff that had high busy time. For example I had Hubi long term storage and some graphs for humidity and temperature levels during the day.
I don't have any error logs in recent history. I guess my issue here is that I barely make any changes to my hub config and at the same time it seems performance gets worse and worse. Same configuration and even more on it with the Graphs and storage was running just fine on C7 and even the first months on C8. I would say couple of months back is when this severe load started and none of my automations worked.
Check to see how much CPU usage is consumed by each of your apps. I find that my biggest usage comes with apps that send data via the LAN or Internet. That includes such things asmy Hue bridge and my ActionTiles dashboard.
Look under Logs/App stats. Make sure the box "Percentage of busy time" is checked.
The apps with the highest CPU usage will be listed first.
Do you leave the hub running for a long time between updates / reboots?
There is an issue with longer uptime where it will start getting "excessive load" errors in the logs for no reason as far as I have found. A reboot fixes it.
I normally don't recommend this but in your case maybe try scheduling a weekly reboot?
I don't reboot it unless I have to, so most probably yes.
If by "for no reason" you mean that it just logs the errors but it actually works, that is not the case for me. I usually find out when my lights stop working.
Scheduled reboot crossed my mind but my main point here is not figuring out my load issue but rather if someone else has experienced the same issue:
This is actually fairly common and somewhat expected depending on the update size, so nothing to worry about if it goes away in the first 10 minutes or so. For the decrease in performance over time issue there are a number of factors that could cause that, but historically it has usually been tied to either a drop in memory below a sustainable level or a rogue/chatty device/app.
Well yes in the case I encountered it also caused things to stop working as well because the code would not run due to this presumed "excessive load". But there was not actually an excess load on the hub, so the errors did not make any sense.
Here is another post on that specific topic. Does this sound like the problem you are getting? I documented it in a reply there with screenshots.