This is a screenshot from my logs page.
Does it mean that this Hub is not very busy? Are all apps included?
All apps should be included, and unless the Device Stats show something that differs largely, your hub has plenty of capacity available to do more.
OK.
So what you are saying is that the CPU of the Hub has a lot of unused capacity.
Furthermore, I took the following screenshot:
I assume (please correct me if I'm wrong), that there is plenty of I/O capacity on the Hub as well.
I recognize, that it is always possible for a "flare up" to happen, which means a constriction of IO capacity (e.g. many Zwave device "talk" all at the same time, etc.).
Both of those numbers are saying that you should have a lot of unused capacity.
http://yourHubIP/hub/advanced/freeOSMemory
Will give you a couple of other numbers to watch: Free Memory and CPU Load over the last 5 minutes
(Can use Hub Information Driver to create a virtual device that can poll these, and other, attributes automatically.)
Free memory tends to drop over time, but as long as it's above 250K normally you're okay. CPU Load is a measure of running apps/devices plus those that are waiting.