Food on Perhentian Besar is pretty generic, but Mama's is a good bit better than that.
We ate twice at Mama's for dinner - they do a fish BBQ every night, with other dishes such as veg and meat curries on the side. The BBQ food is reasonable value and extremely tasty. You can eat on the veranda of the restaurant or out right next to the beach. There's a lovely hustle and bustle during dinner - we loved it.
Service is fairly relaxed.