[Mesa-dev] u_blitter cpu/gpu stall

[Keith Whitwell]

On Mon, 2010-11-22 at 20:06 -0800, Dave Airlie wrote:
> Hi Marek,
> 
> So I was looking at some perf traces from r600g, and I see a stall on
> the blitter quad vbuf, every clear will cause the CPU to block on the
> mapping of the vbuf to upload the new coords. On r300g I can see this
> not mattering as the immediate upload path takes care of things,
> however I think we should probably do something like the attached and
> fire and forget the vertex buffer.
> 
> Dave.


Dave,

I don't have a particular objection to this change in and of itself, but
more broadly I feel it's a bandaid on one particular instance of a usage
pattern which r600g doesn't cope with well.

Ultimately, I think it will be necessary to introduce a pipelined
transfer path for r600g buffers, to avoid stalling on these types of
updates.

Keith