[Intel-gfx] [PATCH] drm/i915: Allow objects to go back above 4GB in the address range

[Daniel Vetter]

On Fri, Dec 11, 2015 at 02:49:52PM +0000, Chris Wilson wrote:
> On Fri, Dec 11, 2015 at 02:34:13PM +0000, Michel Thierry wrote:
> > We detected if objects should be moved to the lower parts when 48-bit
> > support flag was not set, but not the other way around.
> > 
> > This handles the case in which an object was allocated in the 32-bit
> > address range, but it has been marked as safe to move above it, which
> > theoretically would help to keep the lower addresses available for
> > objects which really need to be there.
> > 
> > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> > Signed-off-by: Michel Thierry <michel.thierry at intel.com>
> 
> No. This is not lazy. When we run out of low space, we evict. Until then
> don't cause extra work for no reason.

Yeah, this stuff should just work. First the eviction code should kick
stuff out, and if we totally deadlock then we'll retry with everything
placed nicely. Long-term objects should segregate (assuming you're not
mixing them up badly in the userspace cache).

How did this come up? I think there's a more in-depth story to be shared
here, with some perf data to illustrate it ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch