memcpy is so slowly

When my 138 board is start, the log is:

ARM Clock : 456000000 Hz
DDR Clock : 198000000 Hz

But in my code, when I process frame data, and it's need some memcpy function. But I find that it is so slowly  on DSP side. In my program, ARM communicate to DSP with ListMP. In DSP, I copy D1 420 frame to DSP buffer from ARM side.

I don't known what wrong about it. Who can help me ?

Thanks.