Embodiments of the present disclosure relate to a memory system, a memory controller, and a method for operating the same. Garbage collection is performed with regard to the memory device on the basis of a first amount of time and a second amount of time, the first amount of time being a period of time between triggering of first garbage collection and triggering of second garbage collection, and the second amount of time being an amount of time necessary to perform the second garbage collection. A ratio of the first amount of time to the second amount of time is determined as a target ratio value, and the second amount of time is determined to be equal to or longer than a minimum garbage collection operation time. Accordingly, efficient garbage collection can be performed, and the optimal time to perform garbage collection can be determined with regard to a configured performance drop value.