Embed a single sample in histogram metadata.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index e1d0df6736fa326b5f74c717974f40bf711be0c9..bf22ffcc2e3fedc3f57715d5444f5ccf361ffc62 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -275,14 +275,12 @@ std::unique_ptr<HistogramBase> Histogram::PersistentCreate(
     Sample minimum,
     Sample maximum,
     const BucketRanges* ranges,
-    HistogramBase::AtomicCount* counts,
-    HistogramBase::AtomicCount* logged_counts,
-    uint32_t counts_size,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
     HistogramSamples::Metadata* meta,
     HistogramSamples::Metadata* logged_meta) {
   return WrapUnique(new Histogram(name, minimum, maximum, ranges, counts,
-                                  logged_counts, counts_size, meta,
-                                  logged_meta));
+                                  logged_counts, meta, logged_meta));
 }
 
 // Calculate what range of values are held in each bucket.
@@ -512,20 +510,19 @@ Histogram::Histogram(const std::string& name,
                      Sample minimum,
                      Sample maximum,
                      const BucketRanges* ranges,
-                     HistogramBase::AtomicCount* counts,
-                     HistogramBase::AtomicCount* logged_counts,
-                     uint32_t counts_size,
+                     const DelayedPersistentAllocation& counts,
+                     const DelayedPersistentAllocation& logged_counts,
                      HistogramSamples::Metadata* meta,
                      HistogramSamples::Metadata* logged_meta)
-  : HistogramBase(name),
-    bucket_ranges_(ranges),
-    declared_min_(minimum),
-    declared_max_(maximum) {
+    : HistogramBase(name),
+      bucket_ranges_(ranges),
+      declared_min_(minimum),
+      declared_max_(maximum) {
   if (ranges) {
-    samples_.reset(new SampleVector(HashMetricName(name),
-                                    counts, counts_size, meta, ranges));
-    logged_samples_.reset(new SampleVector(samples_->id(), logged_counts,
-                                           counts_size, logged_meta, ranges));
+    samples_.reset(
+        new PersistentSampleVector(HashMetricName(name), ranges, meta, counts));

[Alexei Svitkine (slow), 2017/04/20 19:56:10]

Wait, why is this switching to PersistentSampleVector?

[bcwhite, 2017/04/20 21:18:07]

Previously, the SampleVector had two ctors, one that told it to use internal
storage and one that provided outside storage.

I've broken it into two separate classes with a common base class.

This means that the (local) SampleVector doesn't need to store an
DelayedPersistentAllocation object and the PersistentSampleVector doesn't need
the local_counts_ vector, even if these are empty.

More importantly, virtual functions provide the correct ways of managing these
storage mechanisms.

The Histogram class, however, still has separate ctors for either local or
persistent storage; this particular one is the persistent version.

[Alexei Svitkine (slow), 2017/04/20 22:11:34]

Makes sense - thanks for the explanation!

+    logged_samples_.reset(new PersistentSampleVector(
+        samples_->id(), ranges, logged_meta, logged_counts));
   }
 }
 
@@ -656,7 +653,7 @@ void Histogram::WriteAsciiImpl(bool graph_it,
   DCHECK_EQ(sample_count, past);
 }
 
-double Histogram::GetPeakBucketSize(const SampleVector& samples) const {
+double Histogram::GetPeakBucketSize(const SampleVectorBase& samples) const {
   double max = 0;
   for (uint32_t i = 0; i < bucket_count() ; ++i) {
     double current_size = GetBucketSize(samples.GetCountAtIndex(i), i);
@@ -666,7 +663,7 @@ double Histogram::GetPeakBucketSize(const SampleVector& samples) const {
   return max;
 }
 
-void Histogram::WriteAsciiHeader(const SampleVector& samples,
+void Histogram::WriteAsciiHeader(const SampleVectorBase& samples,
                                  Count sample_count,
                                  std::string* output) const {
   StringAppendF(output,
@@ -815,14 +812,12 @@ std::unique_ptr<HistogramBase> LinearHistogram::PersistentCreate(
     Sample minimum,
     Sample maximum,
     const BucketRanges* ranges,
-    HistogramBase::AtomicCount* counts,
-    HistogramBase::AtomicCount* logged_counts,
-    uint32_t counts_size,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
     HistogramSamples::Metadata* meta,
     HistogramSamples::Metadata* logged_meta) {
-  return WrapUnique(new LinearHistogram(name, minimum, maximum, ranges,
-                                              counts, logged_counts,
-                                              counts_size, meta, logged_meta));
+  return WrapUnique(new LinearHistogram(name, minimum, maximum, ranges, counts,
+                                        logged_counts, meta, logged_meta));
 }
 
 HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
@@ -851,17 +846,23 @@ LinearHistogram::LinearHistogram(const std::string& name,
     : Histogram(name, minimum, maximum, ranges) {
 }
 
-LinearHistogram::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)
-    : Histogram(name, minimum, maximum, ranges, counts, logged_counts,
-                counts_size, meta, logged_meta) {}
+LinearHistogram::LinearHistogram(
+    const std::string& name,
+    Sample minimum,
+    Sample maximum,
+    const BucketRanges* ranges,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
+    HistogramSamples::Metadata* meta,
+    HistogramSamples::Metadata* logged_meta)
+    : Histogram(name,
+                minimum,
+                maximum,
+                ranges,
+                counts,
+                logged_counts,
+                meta,
+                logged_meta) {}
 
 double LinearHistogram::GetBucketSize(Count current, uint32_t i) const {
   DCHECK_GT(ranges(i + 1), ranges(i));
@@ -961,12 +962,12 @@ HistogramBase* BooleanHistogram::FactoryGet(const char* name, int32_t flags) {
 std::unique_ptr<HistogramBase> BooleanHistogram::PersistentCreate(
     const std::string& name,
     const BucketRanges* ranges,
-    HistogramBase::AtomicCount* counts,
-    HistogramBase::AtomicCount* logged_counts,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
     HistogramSamples::Metadata* meta,
     HistogramSamples::Metadata* logged_meta) {
-  return WrapUnique(new BooleanHistogram(
-      name, ranges, counts, logged_counts, meta, logged_meta));
+  return WrapUnique(new BooleanHistogram(name, ranges, counts, logged_counts,
+                                         meta, logged_meta));
 }
 
 HistogramType BooleanHistogram::GetHistogramType() const {
@@ -977,13 +978,20 @@ BooleanHistogram::BooleanHistogram(const std::string& name,
                                    const BucketRanges* ranges)
     : LinearHistogram(name, 1, 2, ranges) {}
 
-BooleanHistogram::BooleanHistogram(const std::string& name,
-                                   const BucketRanges* ranges,
-                                   HistogramBase::AtomicCount* counts,
-                                   HistogramBase::AtomicCount* logged_counts,
-                                   HistogramSamples::Metadata* meta,
-                                   HistogramSamples::Metadata* logged_meta)
-    : LinearHistogram(name, 1, 2, ranges, counts, logged_counts, 2, meta,
+BooleanHistogram::BooleanHistogram(
+    const std::string& name,
+    const BucketRanges* ranges,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
+    HistogramSamples::Metadata* meta,
+    HistogramSamples::Metadata* logged_meta)
+    : LinearHistogram(name,
+                      1,
+                      2,
+                      ranges,
+                      counts,
+                      logged_counts,
+                      meta,
                       logged_meta) {}
 
 HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
@@ -1068,13 +1076,12 @@ HistogramBase* CustomHistogram::FactoryGet(
 std::unique_ptr<HistogramBase> CustomHistogram::PersistentCreate(
     const std::string& name,
     const BucketRanges* ranges,
-    HistogramBase::AtomicCount* counts,
-    HistogramBase::AtomicCount* logged_counts,
-    uint32_t counts_size,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
     HistogramSamples::Metadata* meta,
     HistogramSamples::Metadata* logged_meta) {
-  return WrapUnique(new CustomHistogram(
-      name, ranges, counts, logged_counts, counts_size, meta, logged_meta));
+  return WrapUnique(new CustomHistogram(name, ranges, counts, logged_counts,
+                                        meta, logged_meta));
 }
 
 HistogramType CustomHistogram::GetHistogramType() const {
@@ -1103,20 +1110,19 @@ CustomHistogram::CustomHistogram(const std::string& name,
                 ranges->range(ranges->bucket_count() - 1),
                 ranges) {}
 
-CustomHistogram::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)
+CustomHistogram::CustomHistogram(
+    const std::string& name,
+    const BucketRanges* ranges,
+    const DelayedPersistentAllocation& counts,
+    const DelayedPersistentAllocation& logged_counts,
+    HistogramSamples::Metadata* meta,
+    HistogramSamples::Metadata* logged_meta)
     : Histogram(name,
                 ranges->range(1),
                 ranges->range(ranges->bucket_count() - 1),
                 ranges,
                 counts,
                 logged_counts,
-                counts_size,
                 meta,
                 logged_meta) {}