drm/i915: Only reschedule the submission tasklet if preemption is possible

If we couple the scheduler more tightly with the execlists policy, we
can apply the preemption policy to the question of whether we need to
kick the tasklet at all for this priority bump.

v2: Rephrase it as a core i915 policy and not an execlists foible.
v3: Pull the kick together.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190507122544.12698-1-chris@chris-wilson.co.uk

1 files changed, 19 insertions, 15 deletions

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 39bc4f54e272..ec22c3fe7360 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -261,16 +261,27 @@ sched_lock_engine(const struct i915_sched_node *node,
 	return engine;
 }
 
-static bool inflight(const struct i915_request *rq,
-		     const struct intel_engine_cs *engine)
+static inline int rq_prio(const struct i915_request *rq)
 {
-	const struct i915_request *active;
+	return rq->sched.attr.priority | __NO_PREEMPTION;
+}
+
+static void kick_submission(struct intel_engine_cs *engine, int prio)
+{
+	const struct i915_request *inflight =
+		port_request(engine->execlists.port);
 
-	if (!i915_request_is_active(rq))
-		return false;
+	/*
+	 * If we are already the currently executing context, don't
+	 * bother evaluating if we should preempt ourselves, or if
+	 * we expect nothing to change as a result of running the
+	 * tasklet, i.e. we have not change the priority queue
+	 * sufficiently to oust the running context.
+	 */
+	if (inflight && !i915_scheduler_need_preempt(prio, rq_prio(inflight)))
+		return;
 
-	active = port_request(engine->execlists.port);
-	return active->hw_context == rq->hw_context;
+	tasklet_hi_schedule(&engine->execlists.tasklet);
 }
 
 static void __i915_schedule(struct i915_request *rq,
@@ -396,15 +407,8 @@ static void __i915_schedule(struct i915_request *rq,
 
 		engine->execlists.queue_priority_hint = prio;
 
-		/*
-		 * If we are already the currently executing context, don't
-		 * bother evaluating if we should preempt ourselves.
-		 */
-		if (inflight(node_to_request(node), engine))
-			continue;
-
 		/* Defer (tasklet) submission until after all of our updates. */
-		tasklet_hi_schedule(&engine->execlists.tasklet);
+		kick_submission(engine, prio);
 	}
 
 	spin_unlock(&engine->timeline.lock);