cogl: Add libsysprof capture based tracing

Add the ability to add tracing instrumentation to the code. When
enabled, trace entries will generate a file with timing information
that will be processable by sysprof for generating visualization of
traces over time.

While enabled by default at compile time, it is possible to disable the
expansion of the macros completely by passing --disable-tracing to
./configure.

Tracing is so far only actually done if actually enabled on explicitly
specified threads.

This will be used by Mutter passing the write end of a pipe, where the
read end is sent to Sysprof itself via the D-Bus method 'Capture()'.

By passing that, we have to detect EPIPE that is sent when Sysprof stops
recording. Fortunately, we already ignore the signal at meta_init(), so
no need to add a custom signal handler.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/197

cogl/cogl-config.h.meson

@@ -4,6 +4,9 @@
 /* Have GLES 2.0 for rendering */
 #mesondefine HAVE_COGL_GLES2
 
+/* Building with Sysprof profiling suport */
+#mesondefine HAVE_TRACING
+
 /* Enable unit tests */
 #mesondefine ENABLE_UNIT_TESTS
 

cogl/cogl/cogl-trace.c

@@ -0,0 +1,188 @@
+/*
+ * Copyright 2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "cogl-config.h"
+
+#ifdef HAVE_TRACING
+
+#include "cogl/cogl-trace.h"
+
+#include <sysprof-capture.h>
+#include <syscall.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define COGL_TRACE_OUTPUT_FILE "cogl-trace-sp-capture.syscap"
+#define BUFFER_LENGTH (4096 * 4)
+
+static void cogl_trace_thread_context_free (gpointer data);
+
+GPrivate cogl_trace_thread_data = G_PRIVATE_INIT (cogl_trace_thread_context_free);
+CoglTraceContext *cogl_trace_context;
+GMutex cogl_trace_mutex;
+
+static CoglTraceContext *
+cogl_trace_context_new (int fd)
+{
+  CoglTraceContext *context;
+  SysprofCaptureWriter *writer;
+
+  g_debug ("Initializing trace context with fd=%d", fd);
+
+  if (fd == -1)
+    {
+      writer = sysprof_capture_writer_new (COGL_TRACE_OUTPUT_FILE,
+                                           BUFFER_LENGTH);
+    }
+  else
+    {
+      writer = sysprof_capture_writer_new_from_fd (fd, BUFFER_LENGTH);
+    }
+
+  context = g_new0 (CoglTraceContext, 1);
+  context->writer = writer;
+  return context;
+}
+
+static void
+ensure_trace_context (int fd)
+{
+  g_mutex_lock (&cogl_trace_mutex);
+  if (!cogl_trace_context)
+    cogl_trace_context = cogl_trace_context_new (fd);
+  g_mutex_unlock (&cogl_trace_mutex);
+}
+
+static CoglTraceThreadContext *
+cogl_trace_thread_context_new (void)
+{
+  CoglTraceThreadContext *thread_context;
+  pid_t tid;
+
+  tid = (pid_t) syscall (SYS_gettid);
+
+  thread_context = g_new0 (CoglTraceThreadContext, 1);
+  thread_context->cpu_id = -1;
+  thread_context->pid = getpid ();
+  thread_context->group = g_strdup_printf ("t:%d", tid);
+
+  return thread_context;
+}
+
+static gboolean
+enable_tracing_idle_callback (gpointer user_data)
+{
+  CoglTraceThreadContext *thread_context =
+    g_private_get (&cogl_trace_thread_data);
+  int fd = GPOINTER_TO_INT (user_data);
+
+  ensure_trace_context (fd);
+
+  if (thread_context)
+    {
+      g_warning ("Tracing already enabled");
+      return G_SOURCE_REMOVE;
+    }
+
+  thread_context = cogl_trace_thread_context_new ();
+  g_private_set (&cogl_trace_thread_data, thread_context);
+
+  return G_SOURCE_REMOVE;
+}
+
+static void
+cogl_trace_thread_context_free (gpointer data)
+{
+  CoglTraceThreadContext *thread_context = data;
+
+  if (!thread_context)
+    return;
+
+  g_free (thread_context->group);
+  g_free (thread_context);
+}
+
+static gboolean
+disable_tracing_idle_callback (gpointer user_data)
+{
+  CoglTraceThreadContext *thread_context =
+    g_private_get (&cogl_trace_thread_data);
+  CoglTraceContext *trace_context;
+
+  if (!thread_context)
+    {
+      g_warning ("Tracing not enabled");
+      return G_SOURCE_REMOVE;
+    }
+
+  g_private_replace (&cogl_trace_thread_data, NULL);
+
+  g_mutex_lock (&cogl_trace_mutex);
+  trace_context = cogl_trace_context;
+  sysprof_capture_writer_flush (trace_context->writer);
+  g_mutex_unlock (&cogl_trace_mutex);
+
+  return G_SOURCE_REMOVE;
+}
+
+void
+cogl_set_tracing_enabled_on_thread (GMainContext *main_context,
+                                    int           fd)
+{
+  GSource *source;
+
+  source = g_idle_source_new ();
+
+  g_source_set_callback (source, enable_tracing_idle_callback, GINT_TO_POINTER (fd), NULL);
+
+  g_source_attach (source, main_context);
+  g_source_unref (source);
+}
+
+void
+cogl_set_tracing_disabled_on_thread (GMainContext *main_context)
+{
+  GSource *source;
+
+  source = g_idle_source_new ();
+
+  g_source_set_callback (source, disable_tracing_idle_callback, NULL, NULL);
+
+  g_source_attach (source, main_context);
+  g_source_unref (source);
+}
+
+#else
+
+#include <string.h>
+#include <stdio.h>
+
+void
+cogl_set_tracing_enabled_on_thread (void *data,
+                                    int   fd)
+{
+  fprintf (stderr, "Tracing not enabled");
+}
+
+void
+cogl_set_tracing_disabled_on_thread (void *data)
+{
+  fprintf (stderr, "Tracing not enabled");
+}
+
+#endif /* HAVE_TRACING */

cogl/cogl/cogl-trace.h

@@ -0,0 +1,138 @@
+/*
+ * Copyright 2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef COGL_TRACE_H
+#define COGL_TRACE_H
+
+#include "cogl-config.h"
+
+#ifdef HAVE_TRACING
+
+#include <glib.h>
+#include <sysprof-capture-writer.h>
+#include <sysprof-clock.h>
+#include <stdint.h>
+#include <errno.h>
+
+typedef struct _CoglTraceContext
+{
+  SysprofCaptureWriter *writer;
+} CoglTraceContext;
+
+typedef struct _CoglTraceThreadContext
+{
+  int cpu_id;
+  GPid pid;
+  char *group;
+} CoglTraceThreadContext;
+
+typedef struct _CoglTraceHead
+{
+  SysprofTimeStamp begin_time;
+  const char *name;
+} CoglTraceHead;
+
+extern GPrivate cogl_trace_thread_data;
+extern CoglTraceContext *cogl_trace_context;
+extern GMutex cogl_trace_mutex;
+
+void cogl_set_tracing_enabled_on_thread (GMainContext *main_context,
+                                         int           fd);
+
+void cogl_set_tracing_disabled_on_thread (GMainContext *main_context);
+
+static inline void
+cogl_trace_begin (CoglTraceHead *head,
+                  const char    *name)
+{
+  head->begin_time = g_get_monotonic_time () * 1000;
+  head->name = name;
+}
+
+static inline void
+cogl_trace_end (CoglTraceHead *head)
+{
+  SysprofTimeStamp end_time;
+  CoglTraceContext *trace_context;
+  CoglTraceThreadContext *trace_thread_context;
+
+  end_time = g_get_monotonic_time () * 1000;
+  trace_context = cogl_trace_context;
+  trace_thread_context = g_private_get (&cogl_trace_thread_data);
+
+  g_mutex_lock (&cogl_trace_mutex);
+  if (!sysprof_capture_writer_add_mark (trace_context->writer,
+                                        head->begin_time,
+                                        trace_thread_context->cpu_id,
+                                        trace_thread_context->pid,
+                                        (uint64_t) end_time - head->begin_time,
+                                        trace_thread_context->group,
+                                        head->name,
+                                        NULL))
+    {
+      /* XXX: g_main_context_get_thread_default() might be wrong, it probably
+       * needs to store the GMainContext in CoglTraceThreadContext when creating
+       * and use it here.
+       */
+      if (errno == EPIPE)
+        cogl_set_tracing_disabled_on_thread (g_main_context_get_thread_default ());
+    }
+  g_mutex_unlock (&cogl_trace_mutex);
+}
+
+static inline void
+cogl_auto_trace_end_helper (CoglTraceHead **head)
+{
+  if (*head)
+    cogl_trace_end (*head);
+}
+
+#define COGL_TRACE_BEGIN(Name) \
+  CoglTraceHead CoglTrace##Name = { 0 }; \
+  if (g_private_get (&cogl_trace_thread_data)) \
+    cogl_trace_begin (&CoglTrace##Name, #Name); \
+
+#define COGL_TRACE_END(Name)\
+  if (g_private_get (&cogl_trace_thread_data)) \
+    cogl_trace_end (&CoglTrace##Name);
+
+#define COGL_TRACE_BEGIN_SCOPED(Name) \
+  CoglTraceHead CoglTrace##Name = { 0 }; \
+  __attribute__((cleanup (cogl_auto_trace_end_helper))) \
+    CoglTraceHead *ScopedCoglTrace##Name = NULL; \
+  if (g_private_get (&cogl_trace_thread_data)) \
+    { \
+      cogl_trace_begin (&CoglTrace##Name, #Name); \
+      ScopedCoglTrace##Name = &CoglTrace##Name; \
+    }
+
+#else /* HAVE_TRACING */
+
+#include <stdio.h>
+
+#define COGL_TRACE_BEGIN(Name) (void) 0
+#define COGL_TRACE_END(Name) (void) 0
+#define COGL_TRACE_BEGIN_SCOPED(Name) (void) 0
+
+void cogl_set_tracing_enabled_on_thread (void *data, int fd);
+
+void cogl_set_tracing_disabled_on_thread (void *data);
+
+#endif /* HAVE_TRACING */
+
+#endif /* COGL_TRACE_H */

cogl/cogl/meson.build

@@ -303,6 +303,8 @@ cogl_sources = [
   'cogl-blend-string.c',
   'cogl-blend-string.h',
   'cogl-debug.c',
+  'cogl-trace.c',
+  'cogl-trace.h',
   'cogl-sub-texture-private.h',
   'cogl-texture-private.h',
   'cogl-texture-2d-private.h',

cogl/meson.build

@@ -7,6 +7,7 @@ cogl_includepath = include_directories('.', 'cogl')
 cdata = configuration_data()
 cdata.set('HAVE_COGL_GL', have_gl)
 cdata.set('HAVE_COGL_GLES2', have_gles2)
+cdata.set('HAVE_TRACING', have_profiler)
 cdata.set('ENABLE_UNIT_TESTS', have_cogl_tests)
 
 cogl_config_h = configure_file(
@@ -26,6 +27,12 @@ cogl_pkg_private_deps = [
   #uprof_dep,
 ]
 
+if have_profiler
+  cogl_pkg_private_deps += [
+    sysprof_dep,
+  ]
+endif
+
 if have_wayland
   cogl_pkg_deps += [
     wayland_server_dep,

config.h.meson

@@ -49,6 +49,9 @@
 /* Building with startup notification support */
 #mesondefine HAVE_STARTUP_NOTIFICATION
 
+/* Building with Sysprof profiling suport */
+#mesondefine HAVE_TRACING
+
 /* Path to Xwayland executable */
 #mesondefine XWAYLAND_PATH
 

meson.build

@@ -264,6 +264,11 @@ if have_tests
   have_installed_tests = get_option('installed_tests')
 endif
 
+have_profiler = get_option('profiler')
+if have_profiler
+  sysprof_dep = dependency('sysprof-capture-3')
+endif
+
 required_functions = [
   'ffs',
   'clz',
@@ -346,6 +351,7 @@ cdata.set('HAVE_LIBWACOM', have_libwacom)
 cdata.set('HAVE_SM', have_sm)
 cdata.set('HAVE_STARTUP_NOTIFICATION', have_startup_notification)
 cdata.set('HAVE_INTROSPECTION', have_introspection)
+cdata.set('HAVE_TRACING', have_profiler)
 
 xkb_base = xkeyboard_config_dep.get_pkgconfig_variable('xkb_base')
 cdata.set_quoted('XKB_BASE', xkb_base)
@@ -411,6 +417,7 @@ output = [
   '        SM....................... ' + have_sm.to_string(),
   '        Startup notification..... ' + have_startup_notification.to_string(),
   '        Introspection............ ' + have_introspection.to_string(),
+  '        Profiler................. ' + have_profiler.to_string(),
   '',
   '    Tests:',
   '',

meson_options.txt

@@ -123,6 +123,12 @@ option('tests',
   description: 'Enable tests globally. Specific test suites can be controlled with core_tests, clutter_tests, and cogl_tests'
 )
 
+option('profiler',
+  type: 'boolean',
+  value: true,
+  description: 'Enable Sysprof tracing'
+)
+
 option('installed_tests',
   type: 'boolean',
   value: true,