[lhl]

In Linux, you can set it as high as you want, although you should probably have a swap drive and still be prepared for you system to die if you set it to 128GiB. Here's how you'd set it to 120GiB:

    # This is deprecated, but can still be referenced
    options amdgpu gttsize=122800

    # This specifies GTT by # of 4KB pages:
    #   31457280 * 4KB / 1024 / 1024 = 120 GiB
    options ttm pages_limit=31457280