[Intel-gfx] [PATCH] drm/i915: Delegate our irq handler to a thread

[Chris Wilson]

Quoting Chris Wilson (2019-09-26 15:25:38)
> Moving our primary irq handler to a RT thread incurs an extra 1us delay
> in process interrupts. This is most notice in waking up client threads,
> where it adds about 20% of extra latency. It also imposes a delay in
> feeding the GPU, an extra 1us before signaling secondary engines and
> extra latency in resubmitting work to keep the GPU busy. The latter case
> is insignificant as the latency hidden by the active GPU, and
> preempt-to-busy ensures that no extra latency is incurred for
> preemption.

Fwiw, gem_wsim says the impact is around 1.25% for transcode (just
looking at the first hour or so of runs), which is enough to put the idea
on the back burner for now.
-Chris