Embed a single sample in histogram metadata.

base/metrics/histogram.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 
 // It supports calls to accumulate either time intervals (which are processed
 // as integral number of milliseconds), or arbitrary integral units.
@@ skipping 68 matching lines @@
 #include "base/macros.h"
 #include "base/metrics/bucket_ranges.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/time/time.h"
 
 namespace base {
 
 class BooleanHistogram;
 class CustomHistogram;
+class DelayedPersistentAllocation;
 class Histogram;
 class LinearHistogram;
 class Pickle;
 class PickleIterator;
 class SampleVector;
+class SampleVectorBase;
 
 class BASE_EXPORT Histogram : public HistogramBase {
  public:
   // Initialize maximum number of buckets in histograms as 16,384.
   static const uint32_t kBucketCount_MAX;
 
   typedef std::vector<Count> Counts;
 
   ~Histogram() override;
 
@@ skipping 31 matching lines @@
                                        base::TimeDelta maximum,
                                        uint32_t bucket_count,
                                        int32_t flags);
 
   // Create a histogram using data in persistent storage.
   static std::unique_ptr<HistogramBase> PersistentCreate(
       const std::string& name,
       Sample minimum,
       Sample maximum,
       const BucketRanges* ranges,
-      HistogramBase::AtomicCount* counts,
-      HistogramBase::AtomicCount* logged_counts,
-      uint32_t counts_size,
       HistogramSamples::Metadata* meta,
-      HistogramSamples::Metadata* logged_meta);
+      const DelayedPersistentAllocation& counts,
+      HistogramSamples::Metadata* logged_meta,

[Alexei Svitkine (slow), 2017/04/12 17:38:06]

Non-const params should be last - so add the new params above the two meta's.
Same below.

[bcwhite, 2017/04/13 00:06:00]

<sigh>  There were arranged like that but I figured they grouped better this
way.

Done.

+      const DelayedPersistentAllocation& logged_counts);
 
   static void InitializeBucketRanges(Sample minimum,
                                      Sample maximum,
                                      BucketRanges* ranges);
 
   // This constant if for FindCorruption. Since snapshots of histograms are
   // taken asynchronously relative to sampling, and our counting code currently
   // does not prevent race conditions, it is pretty likely that we'll catch a
   // redundant count that doesn't match the sample count.  We allow for a
   // certain amount of slop before flagging this as an inconsistency. Even with
@@ skipping 63 matching lines @@
   // Traditionally, histograms allocate their own memory for the bucket
   // vector but "shared" histograms use memory regions allocated from a
   // special memory segment that is passed in here.  It is assumed that
   // the life of this memory is managed externally and exceeds the lifetime
   // of this object. Practically, this memory is never released until the
   // process exits and the OS cleans it up.
   Histogram(const std::string& name,
             Sample minimum,
             Sample maximum,
             const BucketRanges* ranges,
-            HistogramBase::AtomicCount* counts,
-            HistogramBase::AtomicCount* logged_counts,
-            uint32_t counts_size,
             HistogramSamples::Metadata* meta,
-            HistogramSamples::Metadata* logged_meta);
+            const DelayedPersistentAllocation& counts,
+            HistogramSamples::Metadata* logged_meta,
+            const DelayedPersistentAllocation& logged_counts);
 
   // HistogramBase implementation:
   bool SerializeInfoImpl(base::Pickle* pickle) const override;
 
   // Method to override to skip the display of the i'th bucket if it's empty.
   virtual bool PrintEmptyBucket(uint32_t index) const;
 
   // Get normalized size, relative to the ranges(i).
   virtual double GetBucketSize(Count current, uint32_t i) const;
 
@@ skipping 19 matching lines @@
   std::unique_ptr<SampleVector> SnapshotSampleVector() const;
 
   //----------------------------------------------------------------------------
   // Helpers for emitting Ascii graphic.  Each method appends data to output.
 
   void WriteAsciiImpl(bool graph_it,
                       const std::string& newline,
                       std::string* output) const;
 
   // Find out how large (graphically) the largest bucket will appear to be.
-  double GetPeakBucketSize(const SampleVector& samples) const;
+  double GetPeakBucketSize(const SampleVectorBase& samples) const;
 
   // Write a common header message describing this histogram.
-  void WriteAsciiHeader(const SampleVector& samples,
+  void WriteAsciiHeader(const SampleVectorBase& samples,
                         Count sample_count,
                         std::string* output) const;
 
   // Write information about previous, current, and next buckets.
   // Information such as cumulative percentage, etc.
   void WriteAsciiBucketContext(const int64_t past,
                                const Count current,
                                const int64_t remaining,
                                const uint32_t i,
                                std::string* output) const;
 
   // WriteJSON calls these.
   void GetParameters(DictionaryValue* params) const override;
 
   void GetCountAndBucketData(Count* count,
                              int64_t* sum,
                              ListValue* buckets) const override;
 
   // Does not own this object. Should get from StatisticsRecorder.
   const BucketRanges* bucket_ranges_;
 
   Sample declared_min_;  // Less than this goes into the first bucket.
   Sample declared_max_;  // Over this goes into the last bucket.
 
   // Finally, provide the state that changes with the addition of each new
   // sample.
-  std::unique_ptr<SampleVector> samples_;
+  std::unique_ptr<SampleVectorBase> samples_;
 
   // Also keep a previous uploaded state for calculating deltas.
   std::unique_ptr<HistogramSamples> logged_samples_;
 
   // Flag to indicate if PrepareFinalDelta has been previously called. It is
   // used to DCHECK that a final delta is not created multiple times.
   mutable bool final_delta_created_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(Histogram);
 };
@@ skipping 32 matching lines @@
                                        TimeDelta maximum,
                                        uint32_t bucket_count,
                                        int32_t flags);
 
   // Create a histogram using data in persistent storage.
   static std::unique_ptr<HistogramBase> PersistentCreate(
       const std::string& name,
       Sample minimum,
       Sample maximum,
       const BucketRanges* ranges,
-      HistogramBase::AtomicCount* counts,
-      HistogramBase::AtomicCount* logged_counts,
-      uint32_t counts_size,
       HistogramSamples::Metadata* meta,
-      HistogramSamples::Metadata* logged_meta);
+      const DelayedPersistentAllocation& counts,
+      HistogramSamples::Metadata* logged_meta,
+      const DelayedPersistentAllocation& logged_counts);
 
   struct DescriptionPair {
     Sample sample;
     const char* description;  // Null means end of a list of pairs.
   };
 
   // Create a LinearHistogram and store a list of number/text values for use in
   // writing the histogram graph.
   // |descriptions| can be NULL, which means no special descriptions to set. If
   // it's not NULL, the last element in the array must has a NULL in its
@@ skipping 18 matching lines @@
 
   LinearHistogram(const std::string& name,
                   Sample minimum,
                   Sample maximum,
                   const BucketRanges* ranges);
 
   LinearHistogram(const std::string& name,
                   Sample minimum,
                   Sample maximum,
                   const BucketRanges* ranges,
-                  HistogramBase::AtomicCount* counts,
-                  HistogramBase::AtomicCount* logged_counts,
-                  uint32_t counts_size,
                   HistogramSamples::Metadata* meta,
-                  HistogramSamples::Metadata* logged_meta);
+                  const DelayedPersistentAllocation& counts,
+                  HistogramSamples::Metadata* logged_meta,
+                  const DelayedPersistentAllocation& logged_counts);
 
   double GetBucketSize(Count current, uint32_t i) const override;
 
   // If we have a description for a bucket, then return that.  Otherwise
   // let parent class provide a (numeric) description.
   const std::string GetAsciiBucketRange(uint32_t i) const override;
 
   // Skip printing of name for numeric range if we have a name (and if this is
   // an empty bucket).
   bool PrintEmptyBucket(uint32_t index) const override;
@@ skipping 21 matching lines @@
 
   // Overload of the above function that takes a const char* |name| param,
   // to avoid code bloat from the std::string constructor being inlined into
   // call sites.
   static HistogramBase* FactoryGet(const char* name, int32_t flags);
 
   // Create a histogram using data in persistent storage.
   static std::unique_ptr<HistogramBase> PersistentCreate(
       const std::string& name,
       const BucketRanges* ranges,
-      HistogramBase::AtomicCount* counts,
-      HistogramBase::AtomicCount* logged_counts,
       HistogramSamples::Metadata* meta,
-      HistogramSamples::Metadata* logged_meta);
+      const DelayedPersistentAllocation& counts,
+      HistogramSamples::Metadata* logged_meta,
+      const DelayedPersistentAllocation& logged_counts);
 
   HistogramType GetHistogramType() const override;
 
  protected:
   class Factory;
 
  private:
   BooleanHistogram(const std::string& name, const BucketRanges* ranges);
   BooleanHistogram(const std::string& name,
                    const BucketRanges* ranges,
-                   HistogramBase::AtomicCount* counts,
-                   HistogramBase::AtomicCount* logged_counts,
                    HistogramSamples::Metadata* meta,
-                   HistogramSamples::Metadata* logged_meta);
+                   const DelayedPersistentAllocation& counts,
+                   HistogramSamples::Metadata* logged_meta,
+                   const DelayedPersistentAllocation& logged_counts);
 
   friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
       base::PickleIterator* iter);
   static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
 
   DISALLOW_COPY_AND_ASSIGN(BooleanHistogram);
 };
 
 //------------------------------------------------------------------------------
 
@@ skipping 12 matching lines @@
   // to avoid code bloat from the std::string constructor being inlined into
   // call sites.
   static HistogramBase* FactoryGet(const char* name,
                                    const std::vector<Sample>& custom_ranges,
                                    int32_t flags);
 
   // Create a histogram using data in persistent storage.
   static std::unique_ptr<HistogramBase> PersistentCreate(
       const std::string& name,
       const BucketRanges* ranges,
-      HistogramBase::AtomicCount* counts,
-      HistogramBase::AtomicCount* logged_counts,
-      uint32_t counts_size,
       HistogramSamples::Metadata* meta,
-      HistogramSamples::Metadata* logged_meta);
+      const DelayedPersistentAllocation& counts,
+      HistogramSamples::Metadata* logged_meta,
+      const DelayedPersistentAllocation& logged_counts);
 
   // Overridden from Histogram:
   HistogramType GetHistogramType() const override;
 
   // Helper method for transforming an array of valid enumeration values
   // to the std::vector<int> expected by UMA_HISTOGRAM_CUSTOM_ENUMERATION.
   // This function ensures that a guard bucket exists right after any
   // valid sample value (unless the next higher sample is also a valid value),
   // so that invalid samples never fall into the same bucket as valid samples.
   // TODO(kaiwang): Change name to ArrayToCustomEnumRanges.
   static std::vector<Sample> ArrayToCustomRanges(const Sample* values,
                                                  uint32_t num_values);
  protected:
   class Factory;
 
   CustomHistogram(const std::string& name,
                   const BucketRanges* ranges);
 
   CustomHistogram(const std::string& name,
                   const BucketRanges* ranges,
-                  HistogramBase::AtomicCount* counts,
-                  HistogramBase::AtomicCount* logged_counts,
-                  uint32_t counts_size,
                   HistogramSamples::Metadata* meta,
-                  HistogramSamples::Metadata* logged_meta);
+                  const DelayedPersistentAllocation& counts,
+                  HistogramSamples::Metadata* logged_meta,
+                  const DelayedPersistentAllocation& logged_counts);
 
   // HistogramBase implementation:
   bool SerializeInfoImpl(base::Pickle* pickle) const override;
 
   double GetBucketSize(Count current, uint32_t i) const override;
 
  private:
   friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
       base::PickleIterator* iter);
   static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
 
   static bool ValidateCustomRanges(const std::vector<Sample>& custom_ranges);
 
   DISALLOW_COPY_AND_ASSIGN(CustomHistogram);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_H_