Does cudaMemcpyAsync require pinned memory?

[CudaaduC]

Hello! Have some questions about pinned memory.

1. Is pinned memory necessary when we want to perform async-memory copy?

2.If the answer is yes, is there any size limitation of pinned memory?
For example, if we have a 64GB host memory machine, is 4GB pinned memory will influence CPU performance significantly?

Thanks!

Yes, I believe so according to this page;

http://devblogs.nvidia.com/parallelforall/how-overlap-data-transfers-cuda-cc/

“The host memory involved in the data transfer must be pinned memory.”

I have always used pinned memory with cudaMemcpyAsync and do see overlapping behavior.

Using 4 GB out of 64GB host memory will not degrade CPU performance. There is some additional overhead related to the initiall pinned memory allocation (more than a regular host malloc)