RemoteFX GPU VRAM's size!

Hi guys:

I got a problem recently about the RemoteFX GPU.

My server OS is windows server 2012, and the VM's guest OS is Win 7 sp1. I create a vm in hyper-v ,use the RemoteFX GPU tech, and VM　got the VGPU success (I find it in device manager, run "dxdiag"  double check ), but when i run the WoW, the game experience very bad.

I find the VRAM only 115M ,so i think maybe the VRAM is the point, but i can not change the VRAM by manual operation.

So ,how can i do in this situation ?? Is there other reasons???

Thank you very much!!!