[PATCH 6/9] drm/i915: Add kick_backend function to i915_sched_engine

[Jason Ekstrand]

On Thu, Jun 3, 2021 at 4:09 PM Matthew Brost <matthew.brost at intel.com> wrote:
>
> Rather than touching execlist specific structures in the generic
> scheduling code, add a callback function in the backend.

Seems reasonable but why does the function that's there today do
nothing for the ringbuffer and current GuC back-ends?  I'm sure
there's some reason but it's not immediately obvious to me.

--Jason


> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>  .../drm/i915/gt/intel_execlists_submission.c  | 52 ++++++++++++++++
>  drivers/gpu/drm/i915/i915_scheduler.c         | 62 +------------------
>  drivers/gpu/drm/i915/i915_scheduler_types.h   |  4 ++
>  3 files changed, 58 insertions(+), 60 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index 23fd03815ad0..3fac17103837 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -3116,10 +3116,61 @@ static bool can_preempt(struct intel_engine_cs *engine)
>         return engine->class != RENDER_CLASS;
>  }
>
> +static void kick_execlists(const struct i915_request *rq, int prio)
> +{
> +       struct intel_engine_cs *engine = rq->engine;
> +       struct i915_sched_engine *sched_engine = engine->sched_engine;
> +       const struct i915_request *inflight;
> +
> +       /*
> +        * We only need to kick the tasklet once for the high priority
> +        * new context we add into the queue.
> +        */
> +       if (prio <= sched_engine->queue_priority_hint)
> +               return;
> +
> +       rcu_read_lock();
> +
> +       /* Nothing currently active? We're overdue for a submission! */
> +       inflight = execlists_active(&engine->execlists);
> +       if (!inflight)
> +               goto unlock;
> +
> +       /*
> +        * If we are already the currently executing context, don't
> +        * bother evaluating if we should preempt ourselves.
> +        */
> +       if (inflight->context == rq->context)
> +               goto unlock;
> +
> +       ENGINE_TRACE(engine,
> +                    "bumping queue-priority-hint:%d for rq:%llx:%lld, inflight:%llx:%lld prio %d\n",
> +                    prio,
> +                    rq->fence.context, rq->fence.seqno,
> +                    inflight->fence.context, inflight->fence.seqno,
> +                    inflight->sched.attr.priority);
> +
> +       sched_engine->queue_priority_hint = prio;
> +
> +       /*
> +        * Allow preemption of low -> normal -> high, but we do
> +        * not allow low priority tasks to preempt other low priority
> +        * tasks under the impression that latency for low priority
> +        * tasks does not matter (as much as background throughput),
> +        * so kiss.
> +        */
> +       if (prio >= max(I915_PRIORITY_NORMAL, rq_prio(inflight)))
> +               tasklet_hi_schedule(&engine->execlists.tasklet);
> +
> +unlock:
> +       rcu_read_unlock();
> +}
> +
>  static void execlists_set_default_submission(struct intel_engine_cs *engine)
>  {
>         engine->submit_request = execlists_submit_request;
>         engine->sched_engine->schedule = i915_schedule;
> +       engine->sched_engine->kick_backend = kick_execlists;
>         engine->execlists.tasklet.callback = execlists_submission_tasklet;
>  }
>
> @@ -3702,6 +3753,7 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings,
>         ve->base.request_alloc = execlists_request_alloc;
>
>         ve->base.sched_engine->schedule = i915_schedule;
> +       ve->base.sched_engine->kick_backend = kick_execlists;
>         ve->base.submit_request = virtual_submit_request;
>         ve->base.bond_execute = virtual_bond_execute;
>
> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
> index 4bc6969f6a97..035b88f2e4aa 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler.c
> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
> @@ -157,65 +157,6 @@ sched_lock_engine(const struct i915_sched_node *node,
>         return locked;
>  }
>
> -static inline int rq_prio(const struct i915_request *rq)
> -{
> -       return rq->sched.attr.priority;
> -}
> -
> -static inline bool need_preempt(int prio, int active)
> -{
> -       /*
> -        * Allow preemption of low -> normal -> high, but we do
> -        * not allow low priority tasks to preempt other low priority
> -        * tasks under the impression that latency for low priority
> -        * tasks does not matter (as much as background throughput),
> -        * so kiss.
> -        */
> -       return prio >= max(I915_PRIORITY_NORMAL, active);
> -}
> -
> -static void kick_submission(struct intel_engine_cs *engine,
> -                           const struct i915_request *rq,
> -                           int prio)
> -{
> -       const struct i915_request *inflight;
> -
> -       /*
> -        * We only need to kick the tasklet once for the high priority
> -        * new context we add into the queue.
> -        */
> -       if (prio <= engine->sched_engine->queue_priority_hint)
> -               return;
> -
> -       rcu_read_lock();
> -
> -       /* Nothing currently active? We're overdue for a submission! */
> -       inflight = execlists_active(&engine->execlists);
> -       if (!inflight)
> -               goto unlock;
> -
> -       /*
> -        * If we are already the currently executing context, don't
> -        * bother evaluating if we should preempt ourselves.
> -        */
> -       if (inflight->context == rq->context)
> -               goto unlock;
> -
> -       ENGINE_TRACE(engine,
> -                    "bumping queue-priority-hint:%d for rq:%llx:%lld, inflight:%llx:%lld prio %d\n",
> -                    prio,
> -                    rq->fence.context, rq->fence.seqno,
> -                    inflight->fence.context, inflight->fence.seqno,
> -                    inflight->sched.attr.priority);
> -
> -       engine->sched_engine->queue_priority_hint = prio;
> -       if (need_preempt(prio, rq_prio(inflight)))
> -               tasklet_hi_schedule(&engine->execlists.tasklet);
> -
> -unlock:
> -       rcu_read_unlock();
> -}
> -
>  static void __i915_schedule(struct i915_sched_node *node,
>                             const struct i915_sched_attr *attr)
>  {
> @@ -335,7 +276,8 @@ static void __i915_schedule(struct i915_sched_node *node,
>                 }
>
>                 /* Defer (tasklet) submission until after all of our updates. */
> -               kick_submission(engine, node_to_request(node), prio);
> +               if (engine->sched_engine->kick_backend)
> +                       engine->sched_engine->kick_backend(node_to_request(node), prio);
>         }
>
>         spin_unlock(&engine->sched_engine->lock);
> diff --git a/drivers/gpu/drm/i915/i915_scheduler_types.h b/drivers/gpu/drm/i915/i915_scheduler_types.h
> index 3f462f8b06f2..8b3af536e6cf 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler_types.h
> +++ b/drivers/gpu/drm/i915/i915_scheduler_types.h
> @@ -132,6 +132,10 @@ struct i915_sched_engine {
>          */
>         bool no_priolist;
>
> +       /* Kick backend */
> +       void    (*kick_backend)(const struct i915_request *rq,
> +                               int prio);
> +
>         /*
>          * Call when the priority on a request has changed and it and its
>          * dependencies may need rescheduling. Note the request itself may
> --
> 2.28.0
>