[Intel-gfx] [PATCH 1/2] drm/i915/execlists: Pull tasklet interrupt-bh local to direct submission

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-03-24 16:11:10)
> 
> On 24/03/2020 12:07, Chris Wilson wrote:
> > 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.
> 
> Oh and important question - who benefits and how much?

Anything that doesn't want to be deferred to a tasklet like wsim, where
it helps fix a small regression in tip. That and avoiding the worker
where we didn't use to have one. Did not see a difference in syslatency,
so that's still a bone of contention for direction submission.
-Chris