it doesn't matter ... like do hills effect your driving on a highway. When the jet is careening down the runway all that matters is relative speed and whether the runway is long enough (LOL). As long as the "dips" are not trenches and the wheels ride smooth, the plane encounters no loss or gain in performance.
There is actually a picture in Airliners mag, I think an Iceland issue where there is a little runway (one of the shortest in the world or something) and it looks like a U. serious. check it out.
Enter the new age: A340-500, 777-200LR, 7E7