Cycles: Add sample-based runtime profiler that measures time spent in various parts of the CPU kernel

This commit adds a sample-based profiler that runs during CPU rendering and collects statistics on time spent in different parts of the kernel (ray intersection, shader evaluation etc.) as well as time spent per material and object.

The results are currently not exposed in the user interface or per Python yet, to see the stats on the console pass the "--cycles-print-stats" argument to Cycles (e.g. "./blender -- --cycles-print-stats").

Unfortunately, there is no clear way to extend this functionality to CUDA or OpenCL, so it is CPU-only for now.

Reviewers: brecht, sergey, swerner

Reviewed By: brecht, swerner

Differential Revision: https://developer.blender.org/D3892

1 files changed, 178 insertions, 0 deletions

diff --git a/intern/cycles/util/util_profiling.cpp b/intern/cycles/util/util_profiling.cpp
new file mode 100644
index 00000000000..30aaef69310
--- /dev/null
+++ b/intern/cycles/util/util_profiling.cpp
@@ -0,0 +1,178 @@
+/*
+ * Copyright 2011-2018 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "util/util_algorithm.h"
+#include "util/util_profiling.h"
+#include "util/util_set.h"
+
+CCL_NAMESPACE_BEGIN
+
+Profiler::Profiler()
+ : do_stop_worker(true), worker(NULL)
+{
+}
+
+Profiler::~Profiler()
+{
+	assert(worker == NULL);
+}
+
+void Profiler::run()
+{
+	uint64_t updates = 0;
+	auto start_time = std::chrono::system_clock::now();
+	while(!do_stop_worker) {
+		thread_scoped_lock lock(mutex);
+		foreach(ProfilingState *state, states) {
+			uint32_t cur_event = state->event;
+			int32_t cur_shader = state->shader;
+			int32_t cur_object = state->object;
+
+			/* The state reads/writes should be atomic, but just to be sure
+			 * check the values for validity anyways. */
+			if(cur_event < PROFILING_NUM_EVENTS) {
+				event_samples[cur_event]++;
+			}
+
+			if(cur_shader >= 0 && cur_shader < shader_samples.size()) {
+				/* Only consider the active shader during events whose runtime significantly depends on it. */
+				if(((cur_event >= PROFILING_SHADER_EVAL ) && (cur_event <= PROFILING_SUBSURFACE)) ||
+				   ((cur_event >= PROFILING_CLOSURE_EVAL) && (cur_event <= PROFILING_CLOSURE_VOLUME_SAMPLE))) {
+					shader_samples[cur_shader]++;
+				}
+			}
+
+			if(cur_object >= 0 && cur_object < object_samples.size()) {
+				object_samples[cur_object]++;
+			}
+		}
+		lock.unlock();
+
+		/* Relative waits always overshoot a bit, so just waiting 1ms every
+		 * time would cause the sampling to drift over time.
+		 * By keeping track of the absolute time, the wait times correct themselves -
+		 * if one wait overshoots a lot, the next one will be shorter to compensate. */
+		updates++;
+		std::this_thread::sleep_until(start_time + updates*std::chrono::milliseconds(1));
+	}
+}
+
+void Profiler::reset(int num_shaders, int num_objects)
+{
+	bool running = (worker != NULL);
+	if(running) {
+		stop();
+	}
+
+	/* Resize and clear the accumulation vectors. */
+	shader_hits.assign(num_shaders, 0);
+	object_hits.assign(num_objects, 0);
+
+	event_samples.assign(PROFILING_NUM_EVENTS, 0);
+	shader_samples.assign(num_shaders, 0);
+	object_samples.assign(num_objects, 0);
+
+	if(running) {
+		start();
+	}
+}
+
+void Profiler::start()
+{
+	assert(worker == NULL);
+	do_stop_worker = false;
+	worker = new thread(function_bind(&Profiler::run, this));
+}
+
+void Profiler::stop()
+{
+	if(worker != NULL) {
+		do_stop_worker = true;
+
+		worker->join();
+		delete worker;
+		worker = NULL;
+	}
+}
+
+void Profiler::add_state(ProfilingState *state)
+{
+	thread_scoped_lock lock(mutex);
+
+	/* Add the ProfilingState from the list of sampled states. */
+	assert(std::find(states.begin(), states.end(), state) == states.end());
+	states.push_back(state);
+
+	/* Resize thread-local hit counters. */
+	state->shader_hits.assign(shader_hits.size(), 0);
+	state->object_hits.assign(object_hits.size(), 0);
+
+	/* Initialize the state. */
+	state->event = PROFILING_UNKNOWN;
+	state->shader = -1;
+	state->object = -1;
+	state->active = true;
+}
+
+void Profiler::remove_state(ProfilingState *state)
+{
+	thread_scoped_lock lock(mutex);
+
+	/* Remove the ProfilingState from the list of sampled states. */
+	states.erase(std::remove(states.begin(), states.end(), state), states.end());
+	state->active = false;
+
+	/* Merge thread-local hit counters. */
+	assert(shader_hits.size() == state->shader_hits.size());
+	for(int i = 0; i < shader_hits.size(); i++) {
+		shader_hits[i] += state->shader_hits[i];
+	}
+
+	assert(object_hits.size() == state->object_hits.size());
+	for(int i = 0; i < object_hits.size(); i++) {
+		object_hits[i] += state->object_hits[i];
+	}
+}
+
+uint64_t Profiler::get_event(ProfilingEvent event)
+{
+	assert(worker == NULL);
+	return event_samples[event];
+}
+
+bool Profiler::get_shader(int shader, uint64_t &samples, uint64_t &hits)
+{
+	assert(worker == NULL);
+	if(shader_samples[shader] == 0) {
+		return false;
+	}
+	samples = shader_samples[shader];
+	hits = shader_hits[shader];
+	return true;
+}
+
+bool Profiler::get_object(int object, uint64_t &samples, uint64_t &hits)
+{
+	assert(worker == NULL);
+	if(object_samples[object] == 0) {
+		return false;
+	}
+	samples = object_samples[object];
+	hits = object_hits[object];
+	return true;
+}
+
+CCL_NAMESPACE_END