3 cups sounds like a lot of food twice a day.. but it really depends on what food you're feeding. If its a food with lots of fillers, it will take more to give the dog their daily requirements. More food also = more poop.. so it might be worth checking out what's in the food you're feeding now, and if there's any room for improvement.

We've never feed that big of a serving in one meal though, so it does sound like a lot from my end.