cc/base/histograms.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CC_BASE_HISTOGRAMS_H_
   6 #define CC_BASE_HISTOGRAMS_H_
   7
   8 #include "base/compiler_specific.h"
   9 #include "base/metrics/histogram_base.h"
  10 #include "base/metrics/histogram_macros.h"
  11 #include "base/numerics/safe_math.h"
  12 #include "base/strings/stringprintf.h"
  13 #include "base/time/time.h"
  14 #include "base/timer/elapsed_timer.h"
  15 #include "cc/base/cc_export.h"
  16
  17 namespace cc {
  18
  19 // Supplies a client name to be inserted into histogram names.
  20 // These are known so far: Renderer, Browser
  21 //
  22 // We currently assume that there is only one distinct client per process.
  23 // Not thread-safe. If called multiple times, warns and skips metrics.
  24 CC_EXPORT void SetClientNameForMetrics(const char* client_name);
  25
  26 // Returns the client name, for use by applicable cc metrics code.
  27 // May return null, in which case no clients, or at least two clients, set the
  28 // client name, and these metrics should be omitted.
  29 //
  30 // This method guarantees that it will never return two distinct non-null
  31 // values over the lifetime of the process.
  32 const char* GetClientNameForMetrics();
  33
  34 // Emits UMA histogram trackers for time spent as well as area (in pixels)
  35 // processed per unit time. Time is measured in microseconds, and work in
  36 // pixels per millisecond. Histogram name should include a %s to grab the client
  37 // name.
  38 //
  39 // Usage:
  40 //   // Outside of a method, perhaps in a namespace.
  41 //   DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
  42 //       ScopedReticulateSplinesTimer,
  43 //       "Compositing.%s.ReticulateSplinesUs",
  44 //       "Compositing.%s.ReticulateSplinesPixelsPerMs");
  45 //
  46 //   // Inside a method.
  47 //   ScopedReticulateSplinesTimer timer;
  48 //   timer.AddArea(some_rect.size().GetArea());
  49 //
  50 #define DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(class_name, time_histogram,  \
  51                                                area_histogram)              \
  52   class class_name : public ::cc::ScopedUMAHistogramAreaTimerBase {         \
  53    public:                                                                  \
  54     ~class_name();                                                          \
  55   };                                                                        \
  56   class_name::~class_name() {                                               \
  57     Sample time_sample;                                                     \
  58     Sample area_sample;                                                     \
  59     const char* client_name = ::cc::GetClientNameForMetrics();              \
  60     if (client_name && GetHistogramValues(&time_sample, &area_sample)) {    \
  61       /* GetClientNameForMetrics only returns one non-null value over */    \
  62       /* the lifetime of the process, so these histogram names are */       \
  63       /* runtime constant. */                                               \
  64       UMA_HISTOGRAM_COUNTS(base::StringPrintf(time_histogram, client_name), \
  65                            time_sample);                                    \
  66       UMA_HISTOGRAM_COUNTS(base::StringPrintf(area_histogram, client_name), \
  67                            area_sample);                                    \
  68     }                                                                       \
  69   }
  70
  71 class CC_EXPORT ScopedUMAHistogramAreaTimerBase {
  72  public:
  73   void AddArea(int area) { area_ += area; }
  74   void SetArea(int area) { area_ = area; }
  75
  76  protected:
  77   using Sample = base::HistogramBase::Sample;
  78
  79   ScopedUMAHistogramAreaTimerBase();
  80   ~ScopedUMAHistogramAreaTimerBase();
  81
  82   // Returns true if histograms should be recorded (i.e. values are valid).
  83   bool GetHistogramValues(Sample* time_microseconds,
  84                           Sample* pixels_per_ms) const;
  85
  86  private:
  87   static bool GetHistogramValues(base::TimeDelta elapsed,
  88                                  int area,
  89                                  Sample* time_microseconds,
  90                                  Sample* pixels_per_ms);
  91
  92   base::ElapsedTimer timer_;
  93   base::CheckedNumeric<int> area_;
  94
  95   friend class ScopedUMAHistogramAreaTimerBaseTest;
  96   DISALLOW_COPY_AND_ASSIGN(ScopedUMAHistogramAreaTimerBase);
  97 };
  98
  99 }  // namespace cc
 100
 101 #endif  // CC_BASE_HISTOGRAMS_H_