Weird DMA result

Hello. I just done a memory to memory transfer using DMA. I transfer 2MB of data and DMA can improve the transferring performance to 100%. I think this is weird. May I know how much can really DMA improves or does it really can improve until 100%? I am not using HAL functions but by controlling the DMA registers. The data is transferred from SDRAM to SRAM on Altera DE2 board. please assist. thanks!