If we change the priority of the active context, then it has no impact
on the decision of whether to preempt the active context -- we don't
preempt the context with itself. In this situation, we elide the tasklet
rescheduling and should *not* be marking up the queue_priority_hint as
that may mask a later submission where we decide we don't have to kick
the tasklet as a higher priority submission is pending (spoiler alert,
it was not).
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_scheduler.c | 37 ++++++++++++++++-----------
1 file changed, 22 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 0ca40f6bf08c..d2edb527dcb8 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -189,22 +189,34 @@ static inline bool need_preempt(int prio, int active)
return prio >= max(I915_PRIORITY_NORMAL, active);
}
-static void kick_submission(struct intel_engine_cs *engine, int prio)
+static void kick_submission(struct intel_engine_cs *engine,
+ const struct i915_request *rq,
+ int prio)
{
- const struct i915_request *inflight =
- execlists_active(&engine->execlists);
+ 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->execlists.queue_priority_hint)
+ return;
+
+ /* Nothing currently active? We're overdue for a submission! */
+ inflight = execlists_active(&engine->execlists);
+ if (!inflight)
+ return;
/*
* 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.
+ * bother evaluating if we should preempt ourselves.
*/
- if (!inflight || !need_preempt(prio, rq_prio(inflight)))
+ if (inflight->hw_context == rq->hw_context)
return;
- tasklet_hi_schedule(&engine->execlists.tasklet);
+ engine->execlists.queue_priority_hint = prio;
+ if (need_preempt(prio, rq_prio(inflight)))
+ tasklet_hi_schedule(&engine->execlists.tasklet);
}
static void __i915_schedule(struct i915_sched_node *node,
@@ -330,13 +342,8 @@ static void __i915_schedule(struct i915_sched_node *node,
list_move_tail(&node->link, cache.priolist);
}
- if (prio <= engine->execlists.queue_priority_hint)
- continue;
-
- engine->execlists.queue_priority_hint = prio;
-
/* Defer (tasklet) submission until after all of our updates. */
- kick_submission(engine, prio);
+ kick_submission(engine, node_to_request(node), prio);
}
spin_unlock(&engine->active.lock);
--
2.23.0
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