[gtk+/wip/ebassi/gsk-renderer] gsk: Add GL profiler

[Emmanuele Bassi <ebassi src gnome org>]

commit 204de4c422e05864750b9a4a20f75eccde03af58
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Jul 12 14:50:48 2016 +0100

    gsk: Add GL profiler
    
    We can use the GL_ARB_timer_query extension (available since OpenGL
    3.2, and part of the OpenGL specification since version 3.3) to query
    the time elapsed when drawing each frame. This allows us to gather
    timing information on our use of the GPU.

 gsk/Makefile.am            |    2 +
 gsk/gskglprofiler.c        |  100 ++++++++++++++++++++++++++++++++++++++++++++
 gsk/gskglprofilerprivate.h |   18 ++++++++
 gsk/gskglrenderer.c        |   13 +++++-
 4 files changed, 131 insertions(+), 2 deletions(-)
---
diff --git a/gsk/Makefile.am b/gsk/Makefile.am
index 3f5f4d1..32f4192 100644
--- a/gsk/Makefile.am
+++ b/gsk/Makefile.am
@@ -37,6 +37,7 @@ gsk_private_source_h = \
        gskcairorendererprivate.h \
        gskdebugprivate.h \
        gskgldriverprivate.h \
+       gskglprofilerprivate.h \
        gskglrendererprivate.h \
        gskprivate.h \
        gskrendererprivate.h \
@@ -54,6 +55,7 @@ gsk_source_c = \
        gskcairorenderer.c \
        gskdebug.c \
        gskgldriver.c \
+       gskglprofiler.c \
        gskglrenderer.c \
        gskrenderer.c \
        gskrendernode.c \
diff --git a/gsk/gskglprofiler.c b/gsk/gskglprofiler.c
new file mode 100644
index 0000000..f404ce1
--- /dev/null
+++ b/gsk/gskglprofiler.c
@@ -0,0 +1,100 @@
+#include "config.h"
+
+#include "gskglprofilerprivate.h"
+
+#include <epoxy/gl.h>
+
+#define N_QUERIES       4
+
+struct _GskGLProfiler
+{
+  GObject parent_instance;
+
+  /* Creating GL queries is kind of expensive, so we pay the
+   * price upfront and create a circular buffer of queries
+   */
+  GLuint gl_queries[N_QUERIES];
+  GLuint active_query;
+
+  gboolean first_frame : 1;
+};
+
+G_DEFINE_TYPE (GskGLProfiler, gsk_gl_profiler, G_TYPE_OBJECT)
+
+static void
+gsk_gl_profiler_finalize (GObject *gobject)
+{
+  GskGLProfiler *self = GSK_GL_PROFILER (gobject);
+
+  glDeleteQueries (N_QUERIES, &self->gl_queries[0]);
+
+  G_OBJECT_CLASS (gsk_gl_profiler_parent_class)->finalize (gobject);
+}
+
+static void
+gsk_gl_profiler_class_init (GskGLProfilerClass *klass)
+{
+  G_OBJECT_CLASS (klass)->finalize = gsk_gl_profiler_finalize;
+}
+
+static void
+gsk_gl_profiler_init (GskGLProfiler *self)
+{
+  glGenQueries (N_QUERIES, &self->gl_queries[0]);
+
+  self->first_frame = TRUE;
+}
+
+GskGLProfiler *
+gsk_gl_profiler_new (void)
+{
+  return g_object_new (GSK_TYPE_GL_PROFILER, NULL);
+}
+
+void
+gsk_gl_profiler_begin_gpu_region (GskGLProfiler *profiler)
+{
+  GLuint query_id;
+
+  g_return_if_fail (GSK_IS_GL_PROFILER (profiler));
+
+  query_id = profiler->gl_queries[profiler->active_query];
+  glBeginQuery (GL_TIME_ELAPSED, query_id);
+}
+
+guint64
+gsk_gl_profiler_end_gpu_region (GskGLProfiler *profiler)
+{
+  GLuint last_query_id;
+  GLint res;
+  GLuint64 elapsed;
+
+  g_return_val_if_fail (GSK_IS_GL_PROFILER (profiler), 0);
+
+  glEndQuery (GL_TIME_ELAPSED);
+
+  if (profiler->active_query == 0)
+    last_query_id = N_QUERIES - 1;
+  else
+    last_query_id = profiler->active_query - 1;
+
+  /* Advance iterator */
+  profiler->active_query += 1;
+  if (profiler->active_query == N_QUERIES)
+    profiler->active_query = 0;
+
+  /* If this is the first frame we already have a result */
+  if (profiler->first_frame)
+    {
+      profiler->first_frame = FALSE;
+      return 0;
+    }
+
+  glGetQueryObjectiv (last_query_id, GL_QUERY_RESULT_AVAILABLE, &res);
+  if (res == 1)
+    glGetQueryObjectui64v (last_query_id, GL_QUERY_RESULT, &elapsed);
+  else
+    elapsed = 0;
+
+  return elapsed;
+}
diff --git a/gsk/gskglprofilerprivate.h b/gsk/gskglprofilerprivate.h
new file mode 100644
index 0000000..51777c0
--- /dev/null
+++ b/gsk/gskglprofilerprivate.h
@@ -0,0 +1,18 @@
+#ifndef __GSK_GL_PROFILER_PRIVATE_H__
+#define __GSK_GL_PROFILER_PRIVATE_H__
+
+#include <gsk/gsktypes.h>
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_GL_PROFILER (gsk_gl_profiler_get_type ())
+G_DECLARE_FINAL_TYPE (GskGLProfiler, gsk_gl_profiler, GSK, GL_PROFILER, GObject)
+
+GskGLProfiler * gsk_gl_profiler_new                     (void);
+
+void            gsk_gl_profiler_begin_gpu_region        (GskGLProfiler *profiler);
+guint64         gsk_gl_profiler_end_gpu_region          (GskGLProfiler *profiler);
+
+G_END_DECLS
+
+#endif /* __GSK_GL_PROFILER_PRIVATE_H__ */
diff --git a/gsk/gskglrenderer.c b/gsk/gskglrenderer.c
index 9e070e6..2ada400 100644
--- a/gsk/gskglrenderer.c
+++ b/gsk/gskglrenderer.c
@@ -5,6 +5,7 @@
 #include "gskdebugprivate.h"
 #include "gskenums.h"
 #include "gskgldriverprivate.h"
+#include "gskglprofilerprivate.h"
 #include "gskrendererprivate.h"
 #include "gskrendernodeprivate.h"
 #include "gskrendernodeiter.h"
@@ -89,7 +90,7 @@ struct _GskGLRenderer
   GQuark attributes[N_ATTRIBUTES];
 
   GskGLDriver *gl_driver;
-
+  GskGLProfiler *gl_profiler;
   GskShaderBuilder *shader_builder;
 
   int gl_min_filter;
@@ -421,6 +422,7 @@ gsk_gl_renderer_realize (GskRenderer *renderer)
 
   g_assert (self->gl_driver == NULL);
   self->gl_driver = gsk_gl_driver_new (self->context);
+  self->gl_profiler = gsk_gl_profiler_new ();
 
   GSK_NOTE (OPENGL, g_print ("Creating buffers and programs\n"));
   if (!gsk_gl_renderer_create_programs (self))
@@ -447,6 +449,7 @@ gsk_gl_renderer_unrealize (GskRenderer *renderer)
   gsk_gl_renderer_destroy_buffers (self);
   gsk_gl_renderer_destroy_programs (self);
 
+  g_clear_object (&self->gl_profiler);
   g_clear_object (&self->gl_driver);
 
   if (self->context == gdk_gl_context_get_current ())
@@ -815,6 +818,7 @@ gsk_gl_renderer_render (GskRenderer *renderer,
   gboolean use_alpha;
   int status;
   guint i;
+  guint64 gpu_time;
 
   if (self->context == NULL)
     return;
@@ -837,6 +841,8 @@ gsk_gl_renderer_render (GskRenderer *renderer,
   if (!gsk_gl_renderer_validate_tree (self, root))
     goto out;
 
+  gsk_gl_profiler_begin_gpu_region (self->gl_profiler);
+
   gsk_gl_driver_begin_frame (self->gl_driver);
 
   /* Ensure that the viewport is up to date */
@@ -887,6 +893,10 @@ gsk_gl_renderer_render (GskRenderer *renderer,
   GSK_NOTE (OPENGL, g_print ("Drawing GL content on Cairo surface using a %s\n",
                              self->texture_id != 0 ? "texture" : "renderbuffer"));
 
+  gsk_gl_driver_end_frame (self->gl_driver);
+  gpu_time = gsk_gl_profiler_end_gpu_region (self->gl_profiler);
+  GSK_NOTE (OPENGL, g_print ("GPU time: %" G_GUINT64_FORMAT " nsec\n", gpu_time));
+
 out:
   use_alpha = gsk_renderer_get_use_alpha (renderer);
 
@@ -898,7 +908,6 @@ out:
                           0, 0, viewport.size.width, viewport.size.height);
 
   gdk_gl_context_make_current (self->context);
-  gsk_gl_driver_end_frame (self->gl_driver);
   gsk_gl_renderer_clear_tree (self);
 }