[Intel-gfx] [PATCH 33/34] drm/i915: Prioritise non-busywait semaphore workloads

[Chris Wilson]

Quoting Chris Wilson (2019-01-21 22:21:16)
> We don't want to busywait on the GPU if we have other work to do. If we
> give non-busywaiting workloads higher (initial) priority than workloads
> that require a busywait, we will prioritise work that is ready to run
> immediately.

Fwiw, without preemption using HW semaphore does perturb user visible
scheduling behaviour (enough for me to be able to write a userspace
deadlock).
-Chris