[Intel-gfx] [PATCH 1/5] drm/i915: Track per-context engine busyness

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Some customers want to know how much of the GPU time are their clients
using in order to make dynamic load balancing decisions.

With the hooks already in place which track the overall engine busyness,
we can extend that slightly to split that time between contexts.

v2: Fix accounting for tail updates.
v3: Rebase.
v4: Mark currently running contexts as active on stats enable.
v5: Include some headers to fix the build.
v6: Added fine grained lock.
v7: Convert to seqlock. (Chris Wilson)
v8: Rebase and tidy with helpers.
v9: Refactor.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_context.c       | 20 ++++++++
 drivers/gpu/drm/i915/gt/intel_context.h       | 11 +++++
 drivers/gpu/drm/i915/gt/intel_context_types.h |  9 ++++
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 16 ++++++-
 drivers/gpu/drm/i915/gt/intel_lrc.c           | 47 ++++++++++++++++---
 5 files changed, 95 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index b1e346d2d35f..b211b48d6cae 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -243,6 +243,7 @@ intel_context_init(struct intel_context *ce,
 	INIT_LIST_HEAD(&ce->signals);
 
 	mutex_init(&ce->pin_mutex);
+	seqlock_init(&ce->stats.lock);
 
 	i915_active_init(&ce->active,
 			 __intel_context_active, __intel_context_retire);
@@ -337,6 +338,25 @@ struct i915_request *intel_context_create_request(struct intel_context *ce)
 	return rq;
 }
 
+ktime_t intel_context_get_busy_time(struct intel_context *ce)
+{
+	unsigned int seq;
+	ktime_t total;
+
+	do {
+		seq = read_seqbegin(&ce->stats.lock);
+
+		total = ce->stats.total;
+
+		if (ce->stats.active)
+			total = ktime_add(total,
+					  ktime_sub(ktime_get(),
+						    ce->stats.start));
+	} while (read_seqretry(&ce->stats.lock, seq));
+
+	return total;
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftest_context.c"
 #endif
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index b39eb1fcfbca..3a15cf32f0a3 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -160,4 +160,15 @@ static inline struct intel_ring *__intel_context_ring_size(u64 sz)
 	return u64_to_ptr(struct intel_ring, sz);
 }
 
+static inline void
+__intel_context_stats_start(struct intel_context_stats *stats, ktime_t now)
+{
+	if (!stats->active) {
+		stats->start = now;
+		stats->active = true;
+	}
+}
+
+ktime_t intel_context_get_busy_time(struct intel_context *ce);
+
 #endif /* __INTEL_CONTEXT_H__ */
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index d1204cc899a3..12cbad0798cb 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -11,6 +11,7 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/types.h>
+#include <linux/seqlock.h>
 
 #include "i915_active_types.h"
 #include "i915_utils.h"
@@ -76,6 +77,14 @@ struct intel_context {
 
 	/** sseu: Control eu/slice partitioning */
 	struct intel_sseu sseu;
+
+	/** stats: Context GPU engine busyness tracking. */
+	struct intel_context_stats {
+		seqlock_t lock;
+		bool active;
+		ktime_t start;
+		ktime_t total;
+	} stats;
 };
 
 #endif /* __INTEL_CONTEXT_TYPES__ */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 3d1d48bf90cf..ac08781c8b24 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1577,8 +1577,20 @@ int intel_enable_engine_stats(struct intel_engine_cs *engine)
 
 		engine->stats.enabled_at = ktime_get();
 
-		/* XXX submission method oblivious? */
-		for (port = execlists->active; (rq = *port); port++)
+		/*
+		 * Mark currently running context as active.
+		 * XXX submission method oblivious?
+		 */
+
+		rq = NULL;
+		port = execlists->active;
+		if (port)
+			rq = *port;
+		if (rq)
+			__intel_context_stats_start(&rq->hw_context->stats,
+						    engine->stats.enabled_at);
+
+		for (; (rq = *port); port++)
 			engine->stats.active++;
 
 		for (port = execlists->pending; (rq = *port); port++) {
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 4ebfecd95032..1f158cb439bc 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -940,6 +940,7 @@ static void intel_engine_context_in(struct intel_engine_cs *engine)
 	if (engine->stats.enabled > 0) {
 		if (engine->stats.active++ == 0)
 			engine->stats.start = ktime_get();
+
 		GEM_BUG_ON(engine->stats.active == 0);
 	}
 
@@ -1088,6 +1089,30 @@ static void reset_active(struct i915_request *rq,
 	ce->lrc_desc |= CTX_DESC_FORCE_RESTORE;
 }
 
+static void
+intel_context_stats_start(struct intel_context_stats *stats)
+{
+	write_seqlock(&stats->lock);
+	__intel_context_stats_start(stats, ktime_get());
+	write_sequnlock(&stats->lock);
+}
+
+static void
+intel_context_stats_stop(struct intel_context_stats *stats)
+{
+	unsigned long flags;
+
+	if (!READ_ONCE(stats->active))
+		return;
+
+	write_seqlock_irqsave(&stats->lock, flags);
+	GEM_BUG_ON(!READ_ONCE(stats->active));
+	stats->total = ktime_add(stats->total,
+				 ktime_sub(ktime_get(), stats->start));
+	stats->active = false;
+	write_sequnlock_irqrestore(&stats->lock, flags);
+}
+
 static inline struct intel_engine_cs *
 __execlists_schedule_in(struct i915_request *rq)
 {
@@ -1155,7 +1180,7 @@ static inline void
 __execlists_schedule_out(struct i915_request *rq,
 			 struct intel_engine_cs * const engine)
 {
-	struct intel_context * const ce = rq->hw_context;
+	struct intel_context *ce = rq->hw_context;
 
 	/*
 	 * NB process_csb() is not under the engine->active.lock and hence
@@ -1172,6 +1197,7 @@ __execlists_schedule_out(struct i915_request *rq,
 		intel_engine_add_retire(engine, ce->timeline);
 
 	intel_engine_context_out(engine);
+	intel_context_stats_stop(&ce->stats);
 	execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
 	intel_gt_pm_put_async(engine->gt);
 
@@ -1389,6 +1415,9 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 		write_desc(execlists,
 			   rq ? execlists_update_context(rq) : 0,
 			   n);
+
+		if (n == 0)
+			intel_context_stats_start(&rq->hw_context->stats);
 	}
 
 	/* we need to manually load the submit queue */
@@ -2197,7 +2226,11 @@ static void process_csb(struct intel_engine_cs *engine)
 
 			WRITE_ONCE(execlists->pending[0], NULL);
 		} else {
-			GEM_BUG_ON(!*execlists->active);
+			struct i915_request *rq = *execlists->active++;
+
+			GEM_BUG_ON(!rq);
+			GEM_BUG_ON(execlists->active - execlists->inflight >
+				   execlists_num_ports(execlists));
 
 			/* port0 completed, advanced to port1 */
 			trace_ports(execlists, "completed", execlists->active);
@@ -2208,12 +2241,14 @@ static void process_csb(struct intel_engine_cs *engine)
 			 * coherent (visible from the CPU) before the
 			 * user interrupt and CSB is processed.
 			 */
-			GEM_BUG_ON(!i915_request_completed(*execlists->active) &&
+			GEM_BUG_ON(!i915_request_completed(rq) &&
 				   !reset_in_progress(execlists));
-			execlists_schedule_out(*execlists->active++);
 
-			GEM_BUG_ON(execlists->active - execlists->inflight >
-				   execlists_num_ports(execlists));
+			execlists_schedule_out(rq);
+			rq = *execlists->active;
+			if (rq)
+				intel_context_stats_start(&rq->hw_context->stats);
+
 		}
 	} while (head != tail);
 
-- 
2.20.1

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