[Intel-gfx] [PATCH] drm/i915/execlists: Pull tasklet interrupt-bh local to direct submission

[Chris Wilson]

Quoting Chris Wilson (2020-03-20 17:47:45)
> We dropped calling process_csb prior to handling direct submission in
> order to avoid the nesting of spinlocks and lift process_csb() and the
> majority of the tasklet out of irq-off. However, we do want to avoid
> ksoftirqd latency in the fast path, so try and pull the interrupt-bh
> local to direct submission if we can acquire the tasklet's lock.
> 
> v2: Tweak the balance to avoid over submitting lite-restores

Sigh. It's a driver problem with lock contention, mostly from aggressive
idling.
-Chris