[Intel-gfx] [PATCH] drm/i915: Avoid using mappable space for relocation processing through the CPU

[Daniel Vetter]

On Sun, Dec 04, 2011 at 12:26:41PM +0000, Chris Wilson wrote:
> We try to avoid writing the relocations through the uncached GTT, if the
> buffer is currently in the CPU write domain and so will be flushed out to
> main memory afterwards anyway. Also on SandyBridge we can safely write
> to the pages in cacheable memory, so long as the buffer is LLC mapped.
> In either of these caches, we therefore do not need to force the
> reallocation of the buffer into the mappable region of the GTT, reducing
> the aperture pressure.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> ---
>
> v2: We need to wait on LLC-mapped buffers before performing the relocs.
> This is neatly done by making the GTT/CPU paths symmetric.
>
> Should fix i-g-t/tests/gem_reloc_vs_gpu when the test case itself is
> debugged ;-)

Testcase is now fixed up and does indeed pass with this patch.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48