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naiveproxy/src/base/metrics/histogram.h
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// 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.
// For Histogram (exponential histogram), LinearHistogram and CustomHistogram,
// the minimum for a declared range is 1 (instead of 0), while the maximum is
// (HistogramBase::kSampleType_MAX - 1). However, there will always be underflow
// and overflow buckets added automatically, so a 0 bucket will always exist
// even when a minimum value of 1 is specified.
// Each use of a histogram with the same name will reference the same underlying
// data, so it is safe to record to the same histogram from multiple locations
// in the code. It is a runtime error if all uses of the same histogram do not
// agree exactly in type, bucket size and range.
// For Histogram and LinearHistogram, the maximum for a declared range should
// always be larger (not equal) than minimal range. Zero and
// HistogramBase::kSampleType_MAX are implicitly added as first and last ranges,
// so the smallest legal bucket_count is 3. However CustomHistogram can have
// bucket count as 2 (when you give a custom ranges vector containing only 1
// range).
// For these 3 kinds of histograms, the max bucket count is always
// (Histogram::kBucketCount_MAX - 1).
// The buckets layout of class Histogram is exponential. For example, buckets
// might contain (sequentially) the count of values in the following intervals:
// [0,1), [1,2), [2,4), [4,8), [8,16), [16,32), [32,64), [64,infinity)
// That bucket allocation would actually result from construction of a histogram
// for values between 1 and 64, with 8 buckets, such as:
// Histogram count("some name", 1, 64, 8);
// Note that the underflow bucket [0,1) and the overflow bucket [64,infinity)
// are also counted by the constructor in the user supplied "bucket_count"
// argument.
// The above example has an exponential ratio of 2 (doubling the bucket width
// in each consecutive bucket). The Histogram class automatically calculates
// the smallest ratio that it can use to construct the number of buckets
// selected in the constructor. An another example, if you had 50 buckets,
// and millisecond time values from 1 to 10000, then the ratio between
// consecutive bucket widths will be approximately somewhere around the 50th
// root of 10000. This approach provides very fine grain (narrow) buckets
// at the low end of the histogram scale, but allows the histogram to cover a
// gigantic range with the addition of very few buckets.
// Usually we use macros to define and use a histogram, which are defined in
// base/metrics/histogram_macros.h. Note: Callers should include that header
// directly if they only access the histogram APIs through macros.
//
// Macros use a pattern involving a function static variable, that is a pointer
// to a histogram. This static is explicitly initialized on any thread
// that detects a uninitialized (NULL) pointer. The potentially racy
// initialization is not a problem as it is always set to point to the same
// value (i.e., the FactoryGet always returns the same value). FactoryGet
// is also completely thread safe, which results in a completely thread safe,
// and relatively fast, set of counters. To avoid races at shutdown, the static
// pointer is NOT deleted, and we leak the histograms at process termination.
#ifndef BASE_METRICS_HISTOGRAM_H_
#define BASE_METRICS_HISTOGRAM_H_
#include <stddef.h>
#include <stdint.h>
#include <map>
#include <memory>
#include <string>
#include <vector>
#include "base/base_export.h"
#include "base/check_op.h"
#include "base/compiler_specific.h"
#include "base/containers/span.h"
#include "base/gtest_prod_util.h"
#include "base/memory/raw_ptr.h"
#include "base/metrics/bucket_ranges.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/histogram_samples.h"
#include "base/strings/string_piece.h"
#include "base/time/time.h"
#include "base/values.h"
namespace base {
class BooleanHistogram;
class CustomHistogram;
class DelayedPersistentAllocation;
class Histogram;
class HistogramTest;
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(const Histogram&) = delete;
Histogram& operator=(const Histogram&) = delete;
~Histogram() override;
//----------------------------------------------------------------------------
// For a valid histogram, input should follow these restrictions:
// minimum > 0 (if a minimum below 1 is specified, it will implicitly be
// normalized up to 1)
// maximum > minimum
// buckets > 2 [minimum buckets needed: underflow, overflow and the range]
// Additionally,
// buckets <= (maximum - minimum + 2) - this is to ensure that we don't have
// more buckets than the range of numbers; having more buckets than 1 per
// value in the range would be nonsensical.
static HistogramBase* FactoryGet(const std::string& name,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryTimeGet(const std::string& name,
base::TimeDelta minimum,
base::TimeDelta maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryMicrosecondsTimeGet(const std::string& name,
base::TimeDelta minimum,
base::TimeDelta maximum,
uint32_t bucket_count,
int32_t flags);
// Overloads of the above functions that take 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,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryTimeGet(const char* name,
base::TimeDelta minimum,
base::TimeDelta maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryMicrosecondsTimeGet(const char* name,
base::TimeDelta minimum,
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 char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
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
// an inconsistency, we'll snapshot it again (for UMA in about a half hour),
// so we'll eventually get the data, if it was not the result of a corruption.
static const int kCommonRaceBasedCountMismatch;
// Check to see if bucket ranges, counts and tallies in the snapshot are
// consistent with the bucket ranges and checksums in our histogram. This can
// produce a false-alarm if a race occurred in the reading of the data during
// a SnapShot process, but should otherwise be false at all times (unless we
// have memory over-writes, or DRAM failures). Flag definitions are located
// under "enum Inconsistency" in base/metrics/histogram_base.h.
uint32_t FindCorruption(const HistogramSamples& samples) const override;
//----------------------------------------------------------------------------
// Accessors for factory construction, serialization and testing.
//----------------------------------------------------------------------------
const BucketRanges* bucket_ranges() const;
Sample declared_min() const;
Sample declared_max() const;
virtual Sample ranges(uint32_t i) const;
virtual uint32_t bucket_count() const;
// This function validates histogram construction arguments. It returns false
// if some of the arguments are bad but also corrects them so they should
// function on non-dcheck builds without crashing.
// Note. Currently it allow some bad input, e.g. 0 as minimum, but silently
// converts it to good input: 1.
// TODO(bcwhite): Use false returns to create "sink" histograms so that bad
// data doesn't create confusion on the servers.
static bool InspectConstructionArguments(StringPiece name,
Sample* minimum,
Sample* maximum,
uint32_t* bucket_count);
// HistogramBase implementation:
uint64_t name_hash() const override;
HistogramType GetHistogramType() const override;
bool HasConstructionArguments(Sample expected_minimum,
Sample expected_maximum,
uint32_t expected_bucket_count) const override;
void Add(Sample value) override;
void AddCount(Sample value, int count) override;
std::unique_ptr<HistogramSamples> SnapshotSamples() const override;
std::unique_ptr<HistogramSamples> SnapshotDelta() override;
std::unique_ptr<HistogramSamples> SnapshotFinalDelta() const override;
void AddSamples(const HistogramSamples& samples) override;
bool AddSamplesFromPickle(base::PickleIterator* iter) override;
base::Value ToGraphDict() const override;
protected:
// This class, defined entirely within the .cc file, contains all the
// common logic for building a Histogram and can be overridden by more
// specific types to alter details of how the creation is done. It is
// defined as an embedded class (rather than an anonymous one) so it
// can access the protected constructors.
class Factory;
// |ranges| should contain the underflow and overflow buckets. See top
// comments for example.
Histogram(const char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges);
// 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 char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
// HistogramBase implementation:
void SerializeInfoImpl(base::Pickle* pickle) const override;
// Return a string description of what goes in a given bucket.
// Most commonly this is the numeric value, but in derived classes it may
// be a name (or string description) given to the bucket.
virtual const std::string GetAsciiBucketRange(uint32_t it) const;
private:
// Allow tests to corrupt our innards for testing purposes.
friend class HistogramTest;
FRIEND_TEST_ALL_PREFIXES(HistogramTest, BoundsTest);
FRIEND_TEST_ALL_PREFIXES(HistogramTest, BucketPlacementTest);
FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptSampleCounts);
friend class StatisticsRecorder; // To allow it to delete duplicates.
friend class StatisticsRecorderTest;
friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
base::PickleIterator* iter);
static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
// Create a snapshot containing all samples (both logged and unlogged).
// Implementation of SnapshotSamples method with a more specific type for
// internal use.
std::unique_ptr<SampleVector> SnapshotAllSamples() const;
// Create a copy of unlogged samples.
std::unique_ptr<SampleVector> SnapshotUnloggedSamples() const;
// Writes the type, min, max, and bucket count information of the histogram in
// |params|.
Value GetParameters() const override;
// Samples that have not yet been logged with SnapshotDelta().
std::unique_ptr<SampleVectorBase> unlogged_samples_;
// Accumulation of all samples that have been logged with SnapshotDelta().
std::unique_ptr<SampleVectorBase> logged_samples_;
#if DCHECK_IS_ON() // Don't waste memory if it won't be used.
// 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;
#endif
};
//------------------------------------------------------------------------------
// LinearHistogram is a more traditional histogram, with evenly spaced
// buckets.
class BASE_EXPORT LinearHistogram : public Histogram {
public:
LinearHistogram(const LinearHistogram&) = delete;
LinearHistogram& operator=(const LinearHistogram&) = delete;
~LinearHistogram() override;
/* minimum should start from 1. 0 is as minimum is invalid. 0 is an implicit
default underflow bucket. */
static HistogramBase* FactoryGet(const std::string& name,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryTimeGet(const std::string& name,
TimeDelta minimum,
TimeDelta maximum,
uint32_t bucket_count,
int32_t flags);
// Overloads of the above two functions that take 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,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t flags);
static HistogramBase* FactoryTimeGet(const char* name,
TimeDelta minimum,
TimeDelta maximum,
uint32_t bucket_count,
int32_t flags);
// Create a histogram using data in persistent storage.
static std::unique_ptr<HistogramBase> PersistentCreate(
const char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
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
// "description" field.
static HistogramBase* FactoryGetWithRangeDescription(
const std::string& name,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t flags,
const DescriptionPair descriptions[]);
static void InitializeBucketRanges(Sample minimum,
Sample maximum,
BucketRanges* ranges);
// Overridden from Histogram:
HistogramType GetHistogramType() const override;
protected:
class Factory;
LinearHistogram(const char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges);
LinearHistogram(const char* name,
Sample minimum,
Sample maximum,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
// 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;
private:
friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
base::PickleIterator* iter);
static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
// For some ranges, we store a printable description of a bucket range.
// If there is no description, then GetAsciiBucketRange() uses parent class
// to provide a description.
typedef std::map<Sample, std::string> BucketDescriptionMap;
BucketDescriptionMap bucket_description_;
};
//------------------------------------------------------------------------------
// ScaledLinearHistogram is a wrapper around a linear histogram that scales the
// counts down by some factor. Remainder values are kept locally but lost when
// uploaded or serialized. The integral counts are rounded up/down so should
// average to the correct value when many reports are added.
//
// This is most useful when adding many counts at once via AddCount() that can
// cause overflows of the 31-bit counters, usually with an enum as the value.
class BASE_EXPORT ScaledLinearHistogram {
using AtomicCount = Histogram::AtomicCount;
using Sample = Histogram::Sample;
public:
// Currently only works with "exact" linear histograms: minimum=1, maximum=N,
// and bucket_count=N+1.
ScaledLinearHistogram(const char* name,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t scale,
int32_t flags);
ScaledLinearHistogram(const std::string& name,
Sample minimum,
Sample maximum,
uint32_t bucket_count,
int32_t scale,
int32_t flags);
ScaledLinearHistogram(const ScaledLinearHistogram&) = delete;
ScaledLinearHistogram& operator=(const ScaledLinearHistogram&) = delete;
~ScaledLinearHistogram();
// Like AddCount() but actually accumulates |count|/|scale| and increments
// the accumulated remainder by |count|%|scale|. An additional increment
// is done when the remainder has grown sufficiently large.
void AddScaledCount(Sample value, int count);
int32_t scale() const { return scale_; }
HistogramBase* histogram() { return histogram_; }
private:
// Pointer to the underlying histogram. Ownership of it remains with
// the statistics-recorder. This is typed as HistogramBase because it may be a
// DummyHistogram if expired.
const raw_ptr<HistogramBase> histogram_;
// The scale factor of the sample counts.
const int32_t scale_;
// A vector of "remainder" counts indexed by bucket number. These values
// may be negative as the scaled count is actually bumped once the
// remainder is 1/2 way to the scale value (thus "rounding").
std::vector<AtomicCount> remainders_;
};
//------------------------------------------------------------------------------
// BooleanHistogram is a histogram for booleans.
class BASE_EXPORT BooleanHistogram : public LinearHistogram {
public:
static HistogramBase* FactoryGet(const std::string& name, int32_t flags);
// 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);
BooleanHistogram(const BooleanHistogram&) = delete;
BooleanHistogram& operator=(const BooleanHistogram&) = delete;
// Create a histogram using data in persistent storage.
static std::unique_ptr<HistogramBase> PersistentCreate(
const char* name,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
HistogramType GetHistogramType() const override;
protected:
class Factory;
private:
BooleanHistogram(const char* name, const BucketRanges* ranges);
BooleanHistogram(const char* name,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
base::PickleIterator* iter);
static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
};
//------------------------------------------------------------------------------
// CustomHistogram is a histogram for a set of custom integers.
class BASE_EXPORT CustomHistogram : public Histogram {
public:
// |custom_ranges| contains a vector of limits on ranges. Each limit should be
// > 0 and < kSampleType_MAX. (Currently 0 is still accepted for backward
// compatibility). The limits can be unordered or contain duplication, but
// client should not depend on this.
static HistogramBase* FactoryGet(const std::string& name,
const std::vector<Sample>& custom_ranges,
int32_t flags);
// 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,
const std::vector<Sample>& custom_ranges,
int32_t flags);
CustomHistogram(const CustomHistogram&) = delete;
CustomHistogram& operator=(const CustomHistogram&) = delete;
// Create a histogram using data in persistent storage.
static std::unique_ptr<HistogramBase> PersistentCreate(
const char* name,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
// 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.
static std::vector<Sample> ArrayToCustomEnumRanges(
base::span<const Sample> values);
protected:
class Factory;
CustomHistogram(const char* name, const BucketRanges* ranges);
CustomHistogram(const char* name,
const BucketRanges* ranges,
const DelayedPersistentAllocation& counts,
const DelayedPersistentAllocation& logged_counts,
HistogramSamples::Metadata* meta,
HistogramSamples::Metadata* logged_meta);
// HistogramBase implementation:
void SerializeInfoImpl(base::Pickle* pickle) 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);
};
} // namespace base
#endif // BASE_METRICS_HISTOGRAM_H_
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