Could you take a look at
Enjoy 10 exciting batches of falling cubes
then let it sit for 10 seconds and look at the cpu, it’s still up at 100% instead of dropping to nothing.
Problem with the sleep function in physx?
You can tweak the sleeping settings quite a bit in the edit → Project Settings → Physics
Specificially sleep and sleep angular velocity. Increase the value and they will start sleeping faster. Increasing Min Penetration for Penalty can also affect the speed at which objects start falling asleep.
Performance wise, i don’t think it is slow because of physics. If you use multiple pixel lights and shadows rendering some 500-1000 cubes is also expensive.
Remember that rendering a 2000 poly mesh and a 8 poly mesh is pretty much the same overhead for a graphics card. It’s about the batch count. For shadows and pixel lights objects need to be rendered multiple times etc.