[RFC PATCH 84/97] drm/i915/guc: Don't allow requests not ready to consume all guc_ids

[Matthew Brost <matthew.brost@intel.com>]

Add a heuristic which checks if over half of the available guc_ids are
currently consumed by requests not ready to be submitted. If this
heuristic is true at request creation time (normal guc_id allocation
location) force all submissions + guc_ids allocations to tasklet.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_context_types.h |  3 ++
 drivers/gpu/drm/i915/gt/intel_reset.c         |  9 ++++
 drivers/gpu/drm/i915/gt/uc/intel_guc.h        |  1 +
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 53 +++++++++++++++++--
 .../gpu/drm/i915/gt/uc/intel_guc_submission.h |  2 +
 5 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index a25ea8fe2029..998f3839411a 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -186,6 +186,9 @@ struct intel_context {
 	/* GuC lrc descriptor reference count */
 	atomic_t guc_id_ref;
 
+	/* GuC number of requests not ready */
+	atomic_t guc_num_rq_not_ready;
+
 	/*
 	 * GuC ID link - in list when unpinned but guc_id still valid in GuC
 	 */
diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index 4347cc2dcea0..be25e39f0dd8 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -22,6 +22,7 @@
 #include "intel_reset.h"
 
 #include "uc/intel_guc.h"
+#include "uc/intel_guc_submission.h"
 
 #define RESET_MAX_RETRIES 3
 
@@ -776,6 +777,14 @@ static void nop_submit_request(struct i915_request *request)
 {
 	RQ_TRACE(request, "-EIO\n");
 
+	/*
+	 * XXX: Kinda ugly to check for GuC submission here but this function is
+	 * going away once we switch to the DRM scheduler so we can live with
+	 * this for now.
+	 */
+	if (intel_engine_uses_guc(request->engine))
+		intel_guc_decr_num_rq_not_ready(request->context);
+
 	request = i915_request_mark_eio(request);
 	if (request) {
 		i915_request_submit(request);
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
index bd477209839b..26a0225f45e9 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -76,6 +76,7 @@ struct intel_guc {
 	struct ida guc_ids;
 	u32 num_guc_ids;
 	u32 max_guc_ids;
+	atomic_t num_guc_ids_not_ready;
 	struct list_head guc_id_list_no_ref;
 	struct list_head guc_id_list_unpinned;
 
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 037a7ee4971b..aa5e608deed5 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -1323,6 +1323,41 @@ static inline void queue_request(struct i915_sched_engine *sched_engine,
 		kick_tasklet(&rq->engine->gt->uc.guc);
 }
 
+/* Macro to tweak heuristic, using a simple over 50% not ready for now */
+#define TOO_MANY_GUC_IDS_NOT_READY(avail, consumed) \
+	(consumed > avail / 2)
+static bool too_many_guc_ids_not_ready(struct intel_guc *guc,
+				       struct intel_context *ce)
+{
+	u32 available_guc_ids, guc_ids_consumed;
+
+	available_guc_ids = guc->num_guc_ids;
+	guc_ids_consumed = atomic_read(&guc->num_guc_ids_not_ready);
+
+	if (TOO_MANY_GUC_IDS_NOT_READY(available_guc_ids, guc_ids_consumed)) {
+		set_and_update_guc_ids_exhausted(guc);
+		return true;
+	}
+
+	return false;
+}
+
+static void incr_num_rq_not_ready(struct intel_context *ce)
+{
+	struct intel_guc *guc = ce_to_guc(ce);
+
+	if (!atomic_fetch_add(1, &ce->guc_num_rq_not_ready))
+		atomic_inc(&guc->num_guc_ids_not_ready);
+}
+
+void intel_guc_decr_num_rq_not_ready(struct intel_context *ce)
+{
+	struct intel_guc *guc = ce_to_guc(ce);
+
+	if (atomic_fetch_add(-1, &ce->guc_num_rq_not_ready) == 1)
+		atomic_dec(&guc->num_guc_ids_not_ready);
+}
+
 static bool need_tasklet(struct intel_guc *guc, struct intel_context *ce)
 {
 	struct i915_sched_engine * const sched_engine =
@@ -1369,6 +1404,8 @@ static void guc_submit_request(struct i915_request *rq)
 		kick_tasklet(guc);
 
 	spin_unlock_irqrestore(&sched_engine->lock, flags);
+
+	intel_guc_decr_num_rq_not_ready(rq->context);
 }
 
 #define GUC_ID_START	64	/* First 64 guc_ids reserved */
@@ -2240,10 +2277,13 @@ static int guc_request_alloc(struct i915_request *rq)
 	GEM_BUG_ON(!intel_context_is_pinned(rq->context));
 
 	/*
-	 * guc_ids are exhausted, don't allocate one here, defer to submission
-	 * in the tasklet.
+	 * guc_ids are exhausted or a heuristic is met indicating too many
+	 * guc_ids are waiting on requests with submission dependencies (not
+	 * ready to submit). Don't allocate one here, defer to submission in the
+	 * tasklet.
 	 */
-	if (test_and_update_guc_ids_exhausted(guc)) {
+	if (test_and_update_guc_ids_exhausted(guc) ||
+	    too_many_guc_ids_not_ready(guc, ce)) {
 		set_bit(I915_FENCE_FLAG_GUC_ID_NOT_PINNED, &rq->fence.flags);
 		goto out;
 	}
@@ -2299,6 +2339,7 @@ static int guc_request_alloc(struct i915_request *rq)
 		 */
 		set_bit(I915_FENCE_FLAG_GUC_ID_NOT_PINNED, &rq->fence.flags);
 		set_and_update_guc_ids_exhausted(guc);
+		incr_num_rq_not_ready(ce);
 
 		return 0;
 	} else if (unlikely(ret < 0)) {
@@ -2321,6 +2362,8 @@ static int guc_request_alloc(struct i915_request *rq)
 	clear_bit(CONTEXT_LRCA_DIRTY, &ce->flags);
 
 out:
+	incr_num_rq_not_ready(ce);
+
 	/*
 	 * We block all requests on this context if a G2H is pending for a
 	 * schedule disable or context deregistration as the GuC will fail a
@@ -3088,6 +3131,8 @@ void intel_guc_log_submission_info(struct intel_guc *guc,
 	drm_printf(p, "GuC submit flags: 0x%04lx\n", guc->flags);
 	drm_printf(p, "GuC total number request without guc_id: %d\n",
 		   guc->total_num_rq_with_no_guc_id);
+	drm_printf(p, "GuC Number GuC IDs not ready: %d\n",
+		   atomic_read(&guc->num_guc_ids_not_ready));
 	drm_printf(p, "GuC stall reason: %d\n", guc->submission_stall_reason);
 	drm_printf(p, "GuC stalled request: %s\n",
 		   yesno(guc->stalled_rq));
@@ -3127,6 +3172,8 @@ void intel_guc_log_context_info(struct intel_guc *guc,
 			   atomic_read(&ce->pin_count));
 		drm_printf(p, "\t\tGuC ID Ref Count: %u\n",
 			   atomic_read(&ce->guc_id_ref));
+		drm_printf(p, "\t\tNumber Requests Not Ready: %u\n",
+			   atomic_read(&ce->guc_num_rq_not_ready));
 		drm_printf(p, "\t\tSchedule State: 0x%x, 0x%x\n\n",
 			   ce->guc_state.sched_state,
 			   atomic_read(&ce->guc_sched_state_no_lock));
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.h
index a2a3fad72be1..60c8b9aaad6e 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.h
@@ -51,4 +51,6 @@ static inline bool intel_guc_submission_is_used(struct intel_guc *guc)
 	return intel_guc_is_used(guc) && intel_guc_submission_is_wanted(guc);
 }
 
+void intel_guc_decr_num_rq_not_ready(struct intel_context *ce);
+
 #endif
-- 
2.28.0