[Mesa-dev] [Intel-gfx] [PATCH 00/68] Broadwell 48b addressing and prelocations (no relocs)

[Chris Wilson]

On Thu, Aug 21, 2014 at 08:11:23PM -0700, Ben Widawsky wrote:
> The primary goal of these patches is to introduce what I've started
> calling, "prelocations" on Broadwell. A prelocation is like a
> relocation, except not. When a GPU client specifies a prelocation, it is
> instructing the kernel where in the GPU address the buffer should be
> mapped. The mechanic works very similarly to a relocation except it uses
> the execbuffer object to obtain the offset, and bind if needed.

You are mixing two APIs. One to preallocate an offset at creation
and one to presume relocations during execbuffer. I'd much rather keep
the flexible execbuffer approach outlined and first submitted a couple of
years ago.

> If a GPU
> client uses only prelocations, the relocation process can be entirely
> skipped. This sounds like a big win initially,

Close to zero if the client uses existing interfaces.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre