[Intel-gfx] [PATCH 31/66] drm/i915/gt: Acquire backing storage for the context

[Thomas Hellström (Intel)]

On 7/15/20 1:51 PM, Chris Wilson wrote:
> Pull the individual acquisition of the context objects (state, ring,
> timeline) under a common i915_acquire_ctx in preparation to allow the
> context to evict memory (or rather the i915_acquire_ctx on its behalf).
>
> The context objects maintain their semi-permanent status; that is they
> are assumed to be accessible by the HW at all times until we receive a
> signal from the HW that they are no longer in use. Currently, we
> generate such a signal ourselves from the context switch following the
> final use of the objects. This means that they will remain on the HW for
> an indefinite amount of time, and we retain the use of pinning to keep
> them in the same place. As they are pinned, they can be processed
> outside of the working set for the requests within the context. This is
> useful, as the context share some global state causing it to incur a
> global lock via its objects. By only requiring that lock as the context
> is activated, it is both reduced in frequency and reduced in duration
> (as compared to execbuf).
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Thomas Hellström <thomas.hellstrom at intel.com>