OpenGL SandBox

Getting a sandbox-like environment for OpenGL debugging. For now I'm profiling shaders in master and blender2.8 branches of Blender. Originally I was using this for testing the setup of OpenGL core profile.

How to build it?

make

How to run it?

__GL_SHADER_DISK_CACHE=0 ./hello

Results

In Linux with an AMD Radeon RX480 running Mesa (Gallium 0.4 - 4.10.0-24-generic) we get:

Version: 4.5
Core profile: 1
time start (control):  hello.cpp:115
time end   (control): 0.003271  hello.cpp:117
time start (master):  hello.cpp:101
time end   (master): 0.088870  hello.cpp:103
time start (eevee):  hello.cpp:108
time end   (eevee): 0.189856  hello.cpp:110

That means Eevee shader compilation is taken 2x as much as master shaders. And those ~200ms means there is a big lag every time the shader is recompiled (e.g., when the user drags a slider in a node).

Running from within Blender I get a similar result, so this sandbox seems well representative of the real production environment.

In a NVIDIA Quadro K6000, proprietary driver 375.39 I get:

Version: 3.3
Core profile: 1
time start (control):  hello.cpp:115
time end   (control): 0.032880  hello.cpp:117
time start (master):  hello.cpp:101
time end   (master): 0.063129  hello.cpp:103
time start (eevee):  hello.cpp:108
time end   (eevee): 0.320869  hello.cpp:110

Now that's more interesting. While the master shader compiles faster, the eevee one compiles considerably slower.

Note

Some systems create a cache for GLSL compiled shaders. So be sure to delete the cache after different runs of this program. Or to use the __GL_SHADER_DISK_CACHE=0 environment value before running, as suggested in the run section of this document.

License

The glsl shaders come from Blender (master, eevee) and Cycles (control). Licensed as GPL2 and Apache respectively.

Shaders

The shaders come from Blender. They were obtained from the following patch in master and blender2.8. The most basic shader (initial cube with a nodetree) was used for this test.

diff --git a/source/blender/gpu/intern/gpu_shader.c b/source/blender/gpu/intern/gpu_shader.c
index f0a1c182713..c9439f5df3f 100644
--- a/source/blender/gpu/intern/gpu_shader.c
+++ b/source/blender/gpu/intern/gpu_shader.c
@@ -267,6 +267,26 @@ GPUShader *GPU_shader_create(const char *vertexcode,
 	                            GPU_SHADER_FLAGS_NONE);
 }
 
+static void gpu_dump_shader(const char **code, const int num_shaders)
+{
+	const char *foldername = "/tmp/";
+	static int i = 0;
+
+	char filename[512] = {'\0'};
+	sprintf(filename, "%s/%04d.shader", foldername, i++);
+
+	FILE *f = fopen(filename, "w");
+	if (f == NULL) {
+		printf("Error writing to file: %s\n", filename);
+	}
+
+	for (int j = 0; j < num_shaders; j++) {
+		fprintf(f, "%s", code[j]);
+	}
+
+	fclose(f);
+}
+
 GPUShader *GPU_shader_create_ex(const char *vertexcode,
                                 const char *fragcode,
                                 const char *geocode,
@@ -325,6 +345,8 @@ GPUShader *GPU_shader_create_ex(const char *vertexcode,
 		if (defines) source[num_source++] = defines;
 		source[num_source++] = vertexcode;
 
+		gpu_dump_shader(source, num_source);
+
 		glAttachShader(shader->program, shader->vertex);
 		glShaderSource(shader->vertex, num_source, source, NULL);
 
@@ -364,6 +386,8 @@ GPUShader *GPU_shader_create_ex(const char *vertexcode,
 		if (libcode) source[num_source++] = libcode;
 		source[num_source++] = fragcode;
 
+		gpu_dump_shader(source, num_source);
+
 		glAttachShader(shader->program, shader->fragment);
 		glShaderSource(shader->fragment, num_source, source, NULL);
 
@@ -390,6 +414,8 @@ GPUShader *GPU_shader_create_ex(const char *vertexcode,
 		if (defines) source[num_source++] = defines;
 		source[num_source++] = geocode;
 
+		gpu_dump_shader(source, num_source);
+
 		glAttachShader(shader->program, shader->geometry);
 		glShaderSource(shader->geometry, num_source, source, NULL);