Hello,
The DMA performance is reported in the reference manual. I.e. for the K64F in its reference manual in the chapter 22.4.4 is documented how to calculate the time that the DMA needs to complete a transaction. In this case the transaction corresponds to a an internal peripheral to internal SRAM so it needs 9 clock cycles assuming zero wait-states. For a more detailed information please go to the reference manual.
Best regards,
Earl.