[PATCH] Mapping snooped user pages into the GTT

[Dave Airlie]

On Sat, Jan 8, 2011 at 2:07 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> I've been looking at how we can improve upload/download performance on our
> UMA gfx. One under-used aspect of the IGP is its ability to blit between
> snooped-and-unsnooped memory i.e. from normal ram into the GTT. Only the
> BLT has this ability, almost all other functions of the GPU most be from
> unsnooped memory. SNB introduces its own cache handling that we need to
> exploit further, however the BLT remains and is orders of magnitude faster
> for read back than an UC read by the CPU...

You might want to test this on a 945G era machine, I think I tried to
get this working back in the TTM days,
I got a lot of crashes and pain and suffering.

But I might have had bad ops happening occasionally or something.

Dave.