There are lots of articles on how to decrease lag by tweaking graphics settings, setting up graphics cards appropriately etc. That solves the problem for most, and while that helps, that doesn't get at all my problems.

I have a very large farming area, with mobs (hostile and passive), tons of redstone circuits, water channels, literally 1000's of hoppers, chests, 100's of minecarts, etc.

So, what (if any) of these cause more lag than others?

Clearly MOBS are a resource hog. If I have 100's spiders in my spider trap, or 1000's of chickens in my chicken farm the game is essentially unplayable. So, I've tweaked all the farms to reduce mob populations dramatically, and the iron golem farms have absolute minimal (16) numbers of villagers. This has helped enormously, but as I continue to grow the farming operations into new products, I'm starting to see more lag appear.

Any anecdotes or data on how much CPU various other in game mechanics consume? Things like:

Hoppers Dispensers

Redstone Circuits

Lava (still, or flowing)

Water (still or flowing)

Running Minecart?

Stationary minecart?

Item Frames and Paintings? (Both are entities, so do they consume more CPU resources?)

other things I've missed?

Thanks