On VE, you can use usual read(2) and write(2) to accesse file system or to transfer data through socket. But its speed is about 1GB/s at maximum in our experience. When we want to accelerate data transfer between VE and CPU, we use VE DMA. Since VE DMA has its own API for DMA, we have to rewrite a program. But we can reach 10GB/s.
Here is the result of our experiment. Source code of this experiment is available on github.
We have also uploaded the sample program and tutorial to show how to use VE DMA. Please take VE DMA into account when you need faster data transfer.