[RFC 4/6] drm/i915/pmu: Add queued counter

[Tvrtko Ursulin <tursulin@ursulin.net>]

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

We add a PMU counter to expose the number of requests which are ready to
run and waiting on a free slot on the GPU.

This is useful to analyze the overall load of the system.

v2: Don't limit to gen8+.
v3:
 * Rebase for dynamic sysfs.
 * Drop currently executing requests.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_pmu.c         | 34 +++++++++++++++++++++++++++++----
 drivers/gpu/drm/i915/intel_ringbuffer.h |  2 +-
 include/uapi/drm/i915_drm.h             |  8 +++++++-
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index cbfca4a255ab..aaf48e85c35e 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -36,7 +36,8 @@
 #define ENGINE_SAMPLE_MASK \
 	(BIT(I915_SAMPLE_BUSY) | \
 	 BIT(I915_SAMPLE_WAIT) | \
-	 BIT(I915_SAMPLE_SEMA))
+	 BIT(I915_SAMPLE_SEMA) | \
+	 BIT(I915_SAMPLE_QUEUED))
 
 #define ENGINE_SAMPLE_BITS (1 << I915_PMU_SAMPLE_BITS)
 
@@ -220,6 +221,11 @@ static void engines_sample(struct drm_i915_private *dev_priv)
 
 		update_sample(&engine->pmu.sample[I915_SAMPLE_SEMA],
 			      PERIOD, !!(val & RING_WAIT_SEMAPHORE));
+
+		if (engine->pmu.enable & BIT(I915_SAMPLE_QUEUED))
+			update_sample(&engine->pmu.sample[I915_SAMPLE_QUEUED],
+				      1 / I915_SAMPLE_QUEUED_SCALE,
+				      engine->queued);
 	}
 
 	if (fw)
@@ -297,6 +303,7 @@ engine_event_status(struct intel_engine_cs *engine,
 	switch (sample) {
 	case I915_SAMPLE_BUSY:
 	case I915_SAMPLE_WAIT:
+	case I915_SAMPLE_QUEUED:
 		break;
 	case I915_SAMPLE_SEMA:
 		if (INTEL_GEN(engine->i915) < 6)
@@ -407,6 +414,9 @@ static u64 __i915_pmu_event_read(struct perf_event *event)
 		} else {
 			val = engine->pmu.sample[sample].cur;
 		}
+
+		if (sample == I915_SAMPLE_QUEUED)
+			val = div_u64(val, FREQUENCY);
 	} else {
 		switch (event->attr.config) {
 		case I915_PMU_ACTUAL_FREQUENCY:
@@ -719,6 +729,16 @@ static const struct attribute_group *i915_pmu_attr_groups[] = {
 { \
 	.sample = (__sample), \
 	.name = (__name), \
+	.suffix = "unit", \
+	.value = "ns", \
+}
+
+#define __engine_event_scale(__sample, __name, __scale) \
+{ \
+	.sample = (__sample), \
+	.name = (__name), \
+	.suffix = "scale", \
+	.value = (__scale), \
 }
 
 static struct i915_ext_attribute *
@@ -762,10 +782,14 @@ create_event_attributes(struct drm_i915_private *i915)
 	static const struct {
 		enum drm_i915_pmu_engine_sample sample;
 		char *name;
+		char *suffix;
+		char *value;
 	} engine_events[] = {
 		__engine_event(I915_SAMPLE_BUSY, "busy"),
 		__engine_event(I915_SAMPLE_SEMA, "sema"),
 		__engine_event(I915_SAMPLE_WAIT, "wait"),
+		__engine_event_scale(I915_SAMPLE_QUEUED, "queued",
+				     __stringify(I915_SAMPLE_QUEUED_SCALE)),
 	};
 	unsigned int count = 0;
 	struct perf_pmu_events_attr *pmu_attr = NULL, *pmu_iter;
@@ -852,13 +876,15 @@ create_event_attributes(struct drm_i915_private *i915)
 								engine->instance,
 								engine_events[i].sample));
 
-			str = kasprintf(GFP_KERNEL, "%s-%s.unit",
-					engine->name, engine_events[i].name);
+			str = kasprintf(GFP_KERNEL, "%s-%s.%s",
+					engine->name, engine_events[i].name,
+					engine_events[i].suffix);
 			if (!str)
 				goto err;
 
 			*attr_iter++ = &pmu_iter->attr.attr;
-			pmu_iter = add_pmu_attr(pmu_iter, str, "ns");
+			pmu_iter = add_pmu_attr(pmu_iter, str,
+						engine_events[i].value);
 		}
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 77fff2488cde..84541b91bcd8 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -379,7 +379,7 @@ struct intel_engine_cs {
 		 *
 		 * Our internal timer stores the current counters in this field.
 		 */
-#define I915_ENGINE_SAMPLE_MAX (I915_SAMPLE_SEMA + 1)
+#define I915_ENGINE_SAMPLE_MAX (I915_SAMPLE_QUEUED + 1)
 		struct i915_pmu_sample sample[I915_ENGINE_SAMPLE_MAX];
 		/**
 		 * @busy_stats: Has enablement of engine stats tracking been
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 536ee4febd74..83458e5b1ac7 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -110,9 +110,12 @@ enum drm_i915_gem_engine_class {
 enum drm_i915_pmu_engine_sample {
 	I915_SAMPLE_BUSY = 0,
 	I915_SAMPLE_WAIT = 1,
-	I915_SAMPLE_SEMA = 2
+	I915_SAMPLE_SEMA = 2,
+	I915_SAMPLE_QUEUED = 3
 };
 
+#define I915_SAMPLE_QUEUED_SCALE 1e-2 /* No braces please. */
+
 #define I915_PMU_SAMPLE_BITS (4)
 #define I915_PMU_SAMPLE_MASK (0xf)
 #define I915_PMU_SAMPLE_INSTANCE_BITS (8)
@@ -133,6 +136,9 @@ enum drm_i915_pmu_engine_sample {
 #define I915_PMU_ENGINE_SEMA(class, instance) \
 	__I915_PMU_ENGINE(class, instance, I915_SAMPLE_SEMA)
 
+#define I915_PMU_ENGINE_QUEUED(class, instance) \
+	__I915_PMU_ENGINE(class, instance, I915_SAMPLE_QUEUED)
+
 #define __I915_PMU_OTHER(x) (__I915_PMU_ENGINE(0xff, 0xff, 0xf) + 1 + (x))
 
 #define I915_PMU_ACTUAL_FREQUENCY	__I915_PMU_OTHER(0)
-- 
2.14.1

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