does cudahostregister consume some GPU memory??

Hello. I’m developing some matrix solver program with MAGMA.

MAGMA code is converted and optimized for my develop environment.

When I use the cudahostregister to use async functions, there is some error.

It is fixed by allocating the GPU memory with enough free memory(about ~500~600 Mbyte.)

So I suspect that cudahostregister uses some resources of GPU.

Are there anyone, who knows about how the cudahostregister works?