611 lines
26 KiB
C++
611 lines
26 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Histogram is an object that aggregates statistics, and can summarize them in
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// various forms, including ASCII graphical, HTML, and numerically (as a
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// vector of numbers corresponding to each of the aggregating buckets).
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// It supports calls to accumulate either time intervals (which are processed
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// as integral number of milliseconds), or arbitrary integral units.
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// For Histogram (exponential histogram), LinearHistogram and CustomHistogram,
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// the minimum for a declared range is 1 (instead of 0), while the maximum is
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// (HistogramBase::kSampleType_MAX - 1). However, there will always be underflow
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// and overflow buckets added automatically, so a 0 bucket will always exist
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// even when a minimum value of 1 is specified.
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// Each use of a histogram with the same name will reference the same underlying
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// data, so it is safe to record to the same histogram from multiple locations
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// in the code. It is a runtime error if all uses of the same histogram do not
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// agree exactly in type, bucket size and range.
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// For Histogram and LinearHistogram, the maximum for a declared range should
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// always be larger (not equal) than minimal range. Zero and
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// HistogramBase::kSampleType_MAX are implicitly added as first and last ranges,
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// so the smallest legal bucket_count is 3. However CustomHistogram can have
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// bucket count as 2 (when you give a custom ranges vector containing only 1
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// range).
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// For these 3 kinds of histograms, the max bucket count is always
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// (Histogram::kBucketCount_MAX - 1).
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// The buckets layout of class Histogram is exponential. For example, buckets
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// might contain (sequentially) the count of values in the following intervals:
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// [0,1), [1,2), [2,4), [4,8), [8,16), [16,32), [32,64), [64,infinity)
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// That bucket allocation would actually result from construction of a histogram
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// for values between 1 and 64, with 8 buckets, such as:
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// Histogram count("some name", 1, 64, 8);
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// Note that the underflow bucket [0,1) and the overflow bucket [64,infinity)
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// are also counted by the constructor in the user supplied "bucket_count"
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// argument.
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// The above example has an exponential ratio of 2 (doubling the bucket width
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// in each consecutive bucket). The Histogram class automatically calculates
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// the smallest ratio that it can use to construct the number of buckets
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// selected in the constructor. An another example, if you had 50 buckets,
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// and millisecond time values from 1 to 10000, then the ratio between
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// consecutive bucket widths will be approximately somewhere around the 50th
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// root of 10000. This approach provides very fine grain (narrow) buckets
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// at the low end of the histogram scale, but allows the histogram to cover a
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// gigantic range with the addition of very few buckets.
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// Usually we use macros to define and use a histogram, which are defined in
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// base/metrics/histogram_macros.h. Note: Callers should include that header
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// directly if they only access the histogram APIs through macros.
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//
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// Macros use a pattern involving a function static variable, that is a pointer
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// to a histogram. This static is explicitly initialized on any thread
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// that detects a uninitialized (NULL) pointer. The potentially racy
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// initialization is not a problem as it is always set to point to the same
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// value (i.e., the FactoryGet always returns the same value). FactoryGet
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// is also completely thread safe, which results in a completely thread safe,
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// and relatively fast, set of counters. To avoid races at shutdown, the static
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// pointer is NOT deleted, and we leak the histograms at process termination.
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#ifndef BASE_METRICS_HISTOGRAM_H_
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#define BASE_METRICS_HISTOGRAM_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <map>
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#include <memory>
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#include <string>
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#include <vector>
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#include "base/base_export.h"
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#include "base/compiler_specific.h"
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#include "base/containers/span.h"
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#include "base/gtest_prod_util.h"
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#include "base/logging.h"
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#include "base/macros.h"
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#include "base/metrics/bucket_ranges.h"
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#include "base/metrics/histogram_base.h"
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#include "base/metrics/histogram_samples.h"
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#include "base/strings/string_piece.h"
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#include "base/time/time.h"
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namespace base {
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class BooleanHistogram;
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class CustomHistogram;
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class DelayedPersistentAllocation;
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class Histogram;
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class HistogramTest;
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class LinearHistogram;
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class Pickle;
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class PickleIterator;
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class SampleVector;
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class SampleVectorBase;
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class BASE_EXPORT Histogram : public HistogramBase {
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public:
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// Initialize maximum number of buckets in histograms as 16,384.
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static const uint32_t kBucketCount_MAX;
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typedef std::vector<Count> Counts;
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~Histogram() override;
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//----------------------------------------------------------------------------
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// For a valid histogram, input should follow these restrictions:
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// minimum > 0 (if a minimum below 1 is specified, it will implicitly be
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// normalized up to 1)
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// maximum > minimum
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// buckets > 2 [minimum buckets needed: underflow, overflow and the range]
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// Additionally,
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// buckets <= (maximum - minimum + 2) - this is to ensure that we don't have
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// more buckets than the range of numbers; having more buckets than 1 per
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// value in the range would be nonsensical.
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static HistogramBase* FactoryGet(const std::string& name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryTimeGet(const std::string& name,
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base::TimeDelta minimum,
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base::TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryMicrosecondsTimeGet(const std::string& name,
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base::TimeDelta minimum,
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base::TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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// Overloads of the above functions that take a const char* |name| param, to
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// avoid code bloat from the std::string constructor being inlined into call
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// sites.
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static HistogramBase* FactoryGet(const char* name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryTimeGet(const char* name,
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base::TimeDelta minimum,
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base::TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryMicrosecondsTimeGet(const char* name,
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base::TimeDelta minimum,
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base::TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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// Create a histogram using data in persistent storage.
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static std::unique_ptr<HistogramBase> PersistentCreate(
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const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges,
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const DelayedPersistentAllocation& counts,
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const DelayedPersistentAllocation& logged_counts,
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HistogramSamples::Metadata* meta,
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HistogramSamples::Metadata* logged_meta);
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static void InitializeBucketRanges(Sample minimum,
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Sample maximum,
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BucketRanges* ranges);
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// This constant if for FindCorruption. Since snapshots of histograms are
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// taken asynchronously relative to sampling, and our counting code currently
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// does not prevent race conditions, it is pretty likely that we'll catch a
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// redundant count that doesn't match the sample count. We allow for a
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// certain amount of slop before flagging this as an inconsistency. Even with
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// an inconsistency, we'll snapshot it again (for UMA in about a half hour),
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// so we'll eventually get the data, if it was not the result of a corruption.
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static const int kCommonRaceBasedCountMismatch;
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// Check to see if bucket ranges, counts and tallies in the snapshot are
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// consistent with the bucket ranges and checksums in our histogram. This can
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// produce a false-alarm if a race occurred in the reading of the data during
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// a SnapShot process, but should otherwise be false at all times (unless we
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// have memory over-writes, or DRAM failures). Flag definitions are located
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// under "enum Inconsistency" in base/metrics/histogram_base.h.
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uint32_t FindCorruption(const HistogramSamples& samples) const override;
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//----------------------------------------------------------------------------
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// Accessors for factory construction, serialization and testing.
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//----------------------------------------------------------------------------
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const BucketRanges* bucket_ranges() const;
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Sample declared_min() const;
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Sample declared_max() const;
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virtual Sample ranges(uint32_t i) const;
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virtual uint32_t bucket_count() const;
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// This function validates histogram construction arguments. It returns false
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// if some of the arguments are bad but also corrects them so they should
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// function on non-dcheck builds without crashing.
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// Note. Currently it allow some bad input, e.g. 0 as minimum, but silently
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// converts it to good input: 1.
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// TODO(bcwhite): Use false returns to create "sink" histograms so that bad
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// data doesn't create confusion on the servers.
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static bool InspectConstructionArguments(StringPiece name,
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Sample* minimum,
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Sample* maximum,
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uint32_t* bucket_count);
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// HistogramBase implementation:
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uint64_t name_hash() const override;
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HistogramType GetHistogramType() const override;
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bool HasConstructionArguments(Sample expected_minimum,
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Sample expected_maximum,
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uint32_t expected_bucket_count) const override;
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void Add(Sample value) override;
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void AddCount(Sample value, int count) override;
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std::unique_ptr<HistogramSamples> SnapshotSamples() const override;
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std::unique_ptr<HistogramSamples> SnapshotDelta() override;
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std::unique_ptr<HistogramSamples> SnapshotFinalDelta() const override;
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void AddSamples(const HistogramSamples& samples) override;
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bool AddSamplesFromPickle(base::PickleIterator* iter) override;
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void WriteHTMLGraph(std::string* output) const override;
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void WriteAscii(std::string* output) const override;
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// Validates the histogram contents and CHECKs on errors.
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// TODO(bcwhite): Remove this after https://crbug/836875.
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void ValidateHistogramContents() const override;
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protected:
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// This class, defined entirely within the .cc file, contains all the
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// common logic for building a Histogram and can be overridden by more
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// specific types to alter details of how the creation is done. It is
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// defined as an embedded class (rather than an anonymous one) so it
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// can access the protected constructors.
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class Factory;
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// |ranges| should contain the underflow and overflow buckets. See top
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// comments for example.
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Histogram(const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges);
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// Traditionally, histograms allocate their own memory for the bucket
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// vector but "shared" histograms use memory regions allocated from a
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// special memory segment that is passed in here. It is assumed that
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// the life of this memory is managed externally and exceeds the lifetime
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// of this object. Practically, this memory is never released until the
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// process exits and the OS cleans it up.
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Histogram(const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges,
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const DelayedPersistentAllocation& counts,
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const DelayedPersistentAllocation& logged_counts,
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HistogramSamples::Metadata* meta,
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HistogramSamples::Metadata* logged_meta);
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// HistogramBase implementation:
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void SerializeInfoImpl(base::Pickle* pickle) const override;
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// Method to override to skip the display of the i'th bucket if it's empty.
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virtual bool PrintEmptyBucket(uint32_t index) const;
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// Get normalized size, relative to the ranges(i).
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virtual double GetBucketSize(Count current, uint32_t i) const;
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// Return a string description of what goes in a given bucket.
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// Most commonly this is the numeric value, but in derived classes it may
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// be a name (or string description) given to the bucket.
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virtual const std::string GetAsciiBucketRange(uint32_t it) const;
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private:
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// Allow tests to corrupt our innards for testing purposes.
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friend class HistogramTest;
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FRIEND_TEST_ALL_PREFIXES(HistogramTest, BoundsTest);
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FRIEND_TEST_ALL_PREFIXES(HistogramTest, BucketPlacementTest);
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FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptSampleCounts);
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friend class StatisticsRecorder; // To allow it to delete duplicates.
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friend class StatisticsRecorderTest;
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friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
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base::PickleIterator* iter);
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static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
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// Create a snapshot containing all samples (both logged and unlogged).
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// Implementation of SnapshotSamples method with a more specific type for
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// internal use.
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std::unique_ptr<SampleVector> SnapshotAllSamples() const;
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// Create a copy of unlogged samples.
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std::unique_ptr<SampleVector> SnapshotUnloggedSamples() const;
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//----------------------------------------------------------------------------
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// Helpers for emitting Ascii graphic. Each method appends data to output.
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void WriteAsciiBody(const SampleVector& snapshot,
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bool graph_it,
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const std::string& newline,
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std::string* output) const;
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// Find out how large (graphically) the largest bucket will appear to be.
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double GetPeakBucketSize(const SampleVectorBase& samples) const;
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// Write a common header message describing this histogram.
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void WriteAsciiHeader(const SampleVectorBase& samples,
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std::string* output) const;
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// Write information about previous, current, and next buckets.
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// Information such as cumulative percentage, etc.
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void WriteAsciiBucketContext(const int64_t past,
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const Count current,
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const int64_t remaining,
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const uint32_t i,
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std::string* output) const;
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// WriteJSON calls these.
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void GetParameters(DictionaryValue* params) const override;
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void GetCountAndBucketData(Count* count,
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int64_t* sum,
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ListValue* buckets) const override;
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// Samples that have not yet been logged with SnapshotDelta().
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std::unique_ptr<SampleVectorBase> unlogged_samples_;
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// Accumulation of all samples that have been logged with SnapshotDelta().
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std::unique_ptr<SampleVectorBase> logged_samples_;
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#if DCHECK_IS_ON() // Don't waste memory if it won't be used.
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// Flag to indicate if PrepareFinalDelta has been previously called. It is
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// used to DCHECK that a final delta is not created multiple times.
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mutable bool final_delta_created_ = false;
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#endif
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DISALLOW_COPY_AND_ASSIGN(Histogram);
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};
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//------------------------------------------------------------------------------
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// LinearHistogram is a more traditional histogram, with evenly spaced
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// buckets.
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class BASE_EXPORT LinearHistogram : public Histogram {
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public:
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~LinearHistogram() override;
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/* minimum should start from 1. 0 is as minimum is invalid. 0 is an implicit
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default underflow bucket. */
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static HistogramBase* FactoryGet(const std::string& name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryTimeGet(const std::string& name,
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TimeDelta minimum,
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TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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// Overloads of the above two functions that take a const char* |name| param,
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// to avoid code bloat from the std::string constructor being inlined into
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// call sites.
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static HistogramBase* FactoryGet(const char* name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t flags);
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static HistogramBase* FactoryTimeGet(const char* name,
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TimeDelta minimum,
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TimeDelta maximum,
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uint32_t bucket_count,
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int32_t flags);
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// Create a histogram using data in persistent storage.
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static std::unique_ptr<HistogramBase> PersistentCreate(
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const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges,
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const DelayedPersistentAllocation& counts,
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const DelayedPersistentAllocation& logged_counts,
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HistogramSamples::Metadata* meta,
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HistogramSamples::Metadata* logged_meta);
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struct DescriptionPair {
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Sample sample;
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const char* description; // Null means end of a list of pairs.
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};
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// Create a LinearHistogram and store a list of number/text values for use in
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// writing the histogram graph.
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// |descriptions| can be NULL, which means no special descriptions to set. If
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// it's not NULL, the last element in the array must has a NULL in its
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// "description" field.
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static HistogramBase* FactoryGetWithRangeDescription(
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const std::string& name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t flags,
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const DescriptionPair descriptions[]);
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static void InitializeBucketRanges(Sample minimum,
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Sample maximum,
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BucketRanges* ranges);
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// Overridden from Histogram:
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HistogramType GetHistogramType() const override;
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protected:
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class Factory;
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LinearHistogram(const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges);
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LinearHistogram(const char* name,
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Sample minimum,
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Sample maximum,
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const BucketRanges* ranges,
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const DelayedPersistentAllocation& counts,
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const DelayedPersistentAllocation& logged_counts,
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HistogramSamples::Metadata* meta,
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HistogramSamples::Metadata* logged_meta);
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double GetBucketSize(Count current, uint32_t i) const override;
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// If we have a description for a bucket, then return that. Otherwise
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// let parent class provide a (numeric) description.
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const std::string GetAsciiBucketRange(uint32_t i) const override;
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// Skip printing of name for numeric range if we have a name (and if this is
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// an empty bucket).
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bool PrintEmptyBucket(uint32_t index) const override;
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private:
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friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
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base::PickleIterator* iter);
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static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
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// For some ranges, we store a printable description of a bucket range.
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// If there is no description, then GetAsciiBucketRange() uses parent class
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// to provide a description.
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typedef std::map<Sample, std::string> BucketDescriptionMap;
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BucketDescriptionMap bucket_description_;
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DISALLOW_COPY_AND_ASSIGN(LinearHistogram);
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};
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//------------------------------------------------------------------------------
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// ScaledLinearHistogram is a wrapper around a linear histogram that scales the
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// counts down by some factor. Remainder values are kept locally but lost when
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// uploaded or serialized. The integral counts are rounded up/down so should
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// average to the correct value when many reports are added.
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//
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// This is most useful when adding many counts at once via AddCount() that can
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// cause overflows of the 31-bit counters, usually with an enum as the value.
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class BASE_EXPORT ScaledLinearHistogram {
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using AtomicCount = Histogram::AtomicCount;
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using Sample = Histogram::Sample;
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public:
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// Currently only works with "exact" linear histograms: minimum=1, maximum=N,
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// and bucket_count=N+1.
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ScaledLinearHistogram(const char* name,
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Sample minimum,
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Sample maximum,
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uint32_t bucket_count,
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int32_t scale,
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int32_t flags);
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~ScaledLinearHistogram();
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// Like AddCount() but actually accumulates |count|/|scale| and increments
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// the accumulated remainder by |count|%|scale|. An additional increment
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// is done when the remainder has grown sufficiently large.
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void AddScaledCount(Sample value, int count);
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int32_t scale() const { return scale_; }
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LinearHistogram* histogram() { return histogram_; }
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private:
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// Pointer to the underlying histogram. Ownership of it remains with
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// the statistics-recorder.
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LinearHistogram* const histogram_;
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// The scale factor of the sample counts.
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const int32_t scale_;
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|
|
|
// 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_;
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|
|
|
DISALLOW_COPY_AND_ASSIGN(ScaledLinearHistogram);
|
|
};
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|
|
|
//------------------------------------------------------------------------------
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|
|
|
// BooleanHistogram is a histogram for booleans.
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class BASE_EXPORT BooleanHistogram : public LinearHistogram {
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public:
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static HistogramBase* FactoryGet(const std::string& name, int32_t flags);
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|
|
|
// 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);
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|
|
|
// 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);
|
|
|
|
DISALLOW_COPY_AND_ASSIGN(BooleanHistogram);
|
|
};
|
|
|
|
//------------------------------------------------------------------------------
|
|
|
|
// 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);
|
|
|
|
// 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;
|
|
|
|
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_
|