1. An OS-based memory management apparatus associated with main memory, comprising: a memory allocation controller configured to control a first memory region within the main memory such that the first memory region, comprising reservation memory for an input/output device among input/output devices, is used as a buffer cache when the input/output device is not active; and a first buffer cache within the OS, wherein: the memory allocation controller controls the first memory region such that the first memory region is used as an eviction-based cache comprising an interface configured to control disposition of information therewithin; the first memory region is used as the eviction-based cache for caching pages evicted from the first buffer cache; and the memory allocation controller controls: an original copy of data cached in the first memory region so that the original copy is stored in an external storage space, and the first memory region such that all contents cached in the first memory region are discarded and the first memory region is immediately used by the input/output device in response to an indication that the first memory region is to be used by the input/output device.