chromium/cc/base/histograms.h

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_BASE_HISTOGRAMS_H_
#define CC_BASE_HISTOGRAMS_H_

#include "base/compiler_specific.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/histogram_macros.h"
#include "base/numerics/safe_math.h"
#include "base/strings/stringprintf.h"
#include "base/time/time.h"
#include "base/timer/elapsed_timer.h"
#include "cc/base/base_export.h"

namespace cc {

// Supplies a client name to be inserted into histogram names.
// These are known so far: Renderer, Browser
//
// We currently assume that there is only one distinct client per process.
// Not thread-safe. If called multiple times, warns and skips metrics.
CC_BASE_EXPORT void SetClientNameForMetrics(const char* client_name);

// Returns the client name, for use by applicable cc metrics code.
// May return null, in which case no clients, or at least two clients, set the
// client name, and these metrics should be omitted.
//
// This method guarantees that it will never return two distinct non-null
// values over the lifetime of the process.
CC_BASE_EXPORT const char* GetClientNameForMetrics();

// Emits UMA histogram trackers for time spent as well as area (in pixels)
// processed per unit time. Time is measured in microseconds, and work in
// pixels per millisecond. Histogram name should include a %s to grab the client
// name.
//
// Usage:
//   // Outside of a method, perhaps in a namespace.
//   DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
//       ScopedReticulateSplinesTimer,
//       "Compositing.%s.ReticulateSplinesUs",
//       "Compositing.%s.ReticulateSplinesPixelsPerMs");
//
//   // Inside a method.
//   ScopedReticulateSplinesTimer timer;
//   timer.AddArea(some_rect.size().GetArea());
//
#define DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(class_name, time_histogram,     \
                                               area_histogram) …

// Version of the above macro for cases which only care about time, not area.
#define DEFINE_SCOPED_UMA_HISTOGRAM_TIMER(class_name, time_histogram) …

class CC_BASE_EXPORT ScopedUMAHistogramAreaTimerBase { … };

}  // namespace cc

#endif  // CC_BASE_HISTOGRAMS_H_