glib/gtrace.c

/*
 * Copyright © 2020 Endless Mobile, Inc.
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 * Author: Philip Withnall <withnall@endlessm.com>
 */

/*
 * The performance tracing functions allow for the performance of code using
 * GLib to be measured by passing metrics from the current process to an
 * external measurement process such as `sysprof-cli` or `sysprofd`.
 *
 * They are designed to execute quickly, especially in the common case where no
 * measurement process is connected. They are guaranteed to not block the caller
 * and are guaranteed to have zero runtime cost if tracing support is disabled
 * at configure time.
 *
 * Tracing information can be provided as ‘marks’ with a start time and
 * duration; or as marks with a start time and no duration. Marks with a
 * duration are intended to show the execution time of a piece of code. Marks
 * with no duration are intended to show an instantaneous performance problem,
 * such as an unexpectedly large allocation, or that a slow path has been taken
 * in some code.
 *
 * |[<!-- language="C" -->
 * gint64 begin_time_nsec G_GNUC_UNUSED;
 *
 * begin_time_nsec = G_TRACE_CURRENT_TIME;
 *
 * // some code which might take a while
 *
 * g_trace_mark (begin_time_nsec, G_TRACE_CURRENT_TIME - begin_time_nsec,
 *               "GLib", "GSource.dispatch",
 *               "%s ⇒ %s", g_source_get_name (source), need_destroy ? "destroy" : "keep");
 * ]|
 *
 * The tracing API is currently internal to GLib.
 *
 * Since: 2.66
 */

#include "config.h"

#include "gtrace-private.h"

#include <stdarg.h>

/*
 * g_trace_mark:
 * @begin_time_nsec: start time of the mark, as returned by %G_TRACE_CURRENT_TIME
 * @duration_nsec: duration of the mark, in nanoseconds
 * @group: name of the group for categorising this mark
 * @name: name of the mark
 * @message_format: format for the detailed message for the mark, in `printf()` format
 * @...: arguments to substitute into @message_format; none of these should have
 *    side effects
 *
 * Add a mark to the trace, starting at @begin_time_nsec and having length
 * @duration_nsec (which may be zero). The @group should typically be `GLib`,
 * and the @name should concisely describe the call site.
 *
 * All of the arguments to this function must not have side effects, as the
 * entire function call may be dropped if sysprof support is not available.
 *
 * Since: 2.66
 */
void
(g_trace_mark) (gint64       begin_time_nsec,
                gint64       duration_nsec,
                const gchar *group,
                const gchar *name,
                const gchar *message_format,
                ...)
{
#ifdef HAVE_SYSPROF
  va_list args;

  va_start (args, message_format);
  sysprof_collector_mark_vprintf (begin_time_nsec, duration_nsec, group, name, message_format, args);
  va_end (args);
#endif  /* HAVE_SYSPROF */
}

/*
 * g_trace_define_int64_counter:
 * @group: name of the group for categorising this counter
 * @name: name of the counter
 * @description: description for the counter
 *
 * Defines a new counter with integer values.
 *
 * The name should be unique within all counters defined with
 * the same @group. The description will be shown in the sysprof UI.
 *
 * To add entries for this counter to a trace, use
 * g_trace_set_int64_counter().
 *
 * Returns: ID of the counter, for use with g_trace_set_int64_counter(),
 *     guaranteed to never be zero
 *
 * Since: 2.68
 */
guint
(g_trace_define_int64_counter) (const char *group,
                                const char *name,
                                const char *description)
{
#ifdef HAVE_SYSPROF
  SysprofCaptureCounter counter;

  counter.id = sysprof_collector_request_counters (1);

  /* sysprof not enabled? */
  if (counter.id == 0)
    return (guint) -1;

  counter.type = SYSPROF_CAPTURE_COUNTER_INT64;
  counter.value.v64 = 0;
  g_strlcpy (counter.category, group, sizeof counter.category);
  g_strlcpy (counter.name, name, sizeof counter.name);
  g_strlcpy (counter.description, description, sizeof counter.description);

  sysprof_collector_define_counters (&counter, 1);

  g_assert (counter.id != 0);

  return counter.id;
#else
  return (guint) -1;
#endif
}

/*
 * g_trace_set_int64_counter:
 * @id: ID of the counter
 * @val: the value to set the counter to
 *
 * Adds a counter value to a trace.
 *
 * The ID must be obtained via g_trace_define_int64_counter()
 * before using this function.
 *
 * Since: 2.68
 */
void
(g_trace_set_int64_counter) (guint  id,
                             gint64 val)
{
#ifdef HAVE_SYSPROF
  SysprofCaptureCounterValue value;

  g_return_if_fail (id != 0);

  /* Ignore setting the counter if we failed to define it in the first place. */
  if (id == (guint) -1)
    return;

  value.v64 = val;
  sysprof_collector_set_counters (&id, &value, 1);
#endif
}