[perf] Add glx.swapComplete event

Add an event when we receive an event on buffer swap completion; we'll
only get this if Clutter is using the INTEL_swap_event GLX extension,
but it's useful to see the actual timing of video frames.

The recorded event includes the actual timestamp of the swap, since
we are given that in the GLX event - on my system it tends to be
consistently 80-100us before we log the event, but if something was
going wrong in event handling (too much synchronous work), then that
could could show up as a longer delay.

https://bugzilla.gnome.org/show_bug.cgi?id=619516

diff --git a/src/gnome-shell-plugin.c b/src/gnome-shell-plugin.c
index 36e2bdf7210d36c55683044db59485988412558d..8e689fdb228a7bfd1b348fc46c39991b64fa2e2d 100644 (file)
--- a/src/gnome-shell-plugin.c
+++ b/src/gnome-shell-plugin.c
@@ -42,6 +42,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <GL/glx.h>
+#include <GL/glxext.h>
+
 #include "display.h"
 
 #include "shell-global-private.h"
@@ -103,6 +106,10 @@ struct _GnomeShellPlugin
   Atom panel_action;
   Atom panel_action_run_dialog;
   Atom panel_action_main_menu;
+
+  int glx_error_base;
+  int glx_event_base;
+  guint have_swap_event : 1;
 };
 
 struct _GnomeShellPluginClass
@@ -284,12 +291,14 @@ gnome_shell_plugin_start (MutterPlugin *plugin)
   GnomeShellPlugin *shell_plugin = GNOME_SHELL_PLUGIN (plugin);
   MetaScreen *screen;
   MetaDisplay *display;
+  Display *xdisplay;
   GtkSettings *settings;
   GError *error = NULL;
   int status;
   const char *shell_js;
   char **search_path;
   ShellGlobal *global;
+  const char *glx_extensions;
 
   bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
   bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
@@ -310,6 +319,21 @@ gnome_shell_plugin_start (MutterPlugin *plugin)
   screen = mutter_plugin_get_screen (plugin);
   display = meta_screen_get_display (screen);
 
+  xdisplay = meta_display_get_xdisplay (display);
+
+  glXQueryExtension (xdisplay,
+                     &shell_plugin->glx_error_base,
+                     &shell_plugin->glx_event_base);
+
+  glx_extensions = glXQueryExtensionsString (xdisplay,
+                                             meta_screen_get_screen_number (screen));
+  shell_plugin->have_swap_event = strstr (glx_extensions, "GLX_INTEL_swap_event") != NULL;
+
+  shell_perf_log_define_event (shell_perf_log_get_default (),
+                               "glx.swapComplete",
+                               "GL buffer swap complete event received (with timestamp of completion)",
+                               "x");
+
   g_irepository_prepend_search_path (GNOME_SHELL_PKGLIBDIR);
 
   shell_js = g_getenv("GNOME_SHELL_JS");
@@ -451,6 +475,25 @@ static gboolean
 gnome_shell_plugin_xevent_filter (MutterPlugin *plugin,
                                   XEvent       *xev)
 {
+#ifdef GLX_INTEL_swap_event
+  GnomeShellPlugin *shell_plugin = GNOME_SHELL_PLUGIN (plugin);
+
+  if (shell_plugin->have_swap_event &&
+      xev->type == (shell_plugin->glx_event_base + GLX_BufferSwapComplete))
+    {
+      GLXBufferSwapComplete *swap_complete_event;
+      swap_complete_event = (GLXBufferSwapComplete *)xev;
+
+      /* Buggy early versions of the INTEL_swap_event implementation in Mesa
+       * can send this with a ust of 0. Simplify life for consumers
+       * by ignoring such events */
+      if (swap_complete_event->ust != 0)
+        shell_perf_log_event_x (shell_perf_log_get_default (),
+                                "glx.swapComplete",
+                                swap_complete_event->ust);
+    }
+#endif
+
   return clutter_x11_handle_event (xev) != CLUTTER_X11_FILTER_CONTINUE;
 }