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196 lines
12 KiB
C
196 lines
12 KiB
C
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// Copyright 2016 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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#ifndef BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_
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#define BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_
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#include <stdint.h>
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#include <limits>
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#include <type_traits>
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#include "base/atomicops.h"
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#include "base/logging.h"
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#include "base/metrics/histogram.h"
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#include "base/metrics/sparse_histogram.h"
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#include "base/time/time.h"
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// This is for macros internal to base/metrics. They should not be used outside
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// of this directory. For writing to UMA histograms, see histogram_macros.h.
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// TODO(rkaplow): Improve commenting of these methods.
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//------------------------------------------------------------------------------
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// Histograms are often put in areas where they are called many many times, and
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// performance is critical. As a result, they are designed to have a very low
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// recurring cost of executing (adding additional samples). Toward that end,
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// the macros declare a static pointer to the histogram in question, and only
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// take a "slow path" to construct (or find) the histogram on the first run
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// through the macro. We leak the histograms at shutdown time so that we don't
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// have to validate using the pointers at any time during the running of the
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// process.
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// In some cases (integration into 3rd party code), it's useful to separate the
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// definition of |atomic_histogram_pointer| from its use. To achieve this we
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// define HISTOGRAM_POINTER_USE, which uses an |atomic_histogram_pointer|, and
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// STATIC_HISTOGRAM_POINTER_BLOCK, which defines an |atomic_histogram_pointer|
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// and forwards to HISTOGRAM_POINTER_USE.
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#define HISTOGRAM_POINTER_USE(atomic_histogram_pointer, \
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constant_histogram_name, \
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histogram_add_method_invocation, \
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histogram_factory_get_invocation) \
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do { \
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/* \
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* Acquire_Load() ensures that we acquire visibility to the \
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* pointed-to data in the histogram. \
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*/ \
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base::HistogramBase* histogram_pointer( \
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reinterpret_cast<base::HistogramBase*>( \
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base::subtle::Acquire_Load(atomic_histogram_pointer))); \
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if (!histogram_pointer) { \
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/* \
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* This is the slow path, which will construct OR find the \
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* matching histogram. histogram_factory_get_invocation includes \
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* locks on a global histogram name map and is completely thread \
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* safe. \
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*/ \
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histogram_pointer = histogram_factory_get_invocation; \
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\
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/* \
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* Use Release_Store to ensure that the histogram data is made \
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* available globally before we make the pointer visible. Several \
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* threads may perform this store, but the same value will be \
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* stored in all cases (for a given named/spec'ed histogram). \
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* We could do this without any barrier, since FactoryGet entered \
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* and exited a lock after construction, but this barrier makes \
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* things clear. \
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*/ \
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base::subtle::Release_Store( \
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atomic_histogram_pointer, \
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reinterpret_cast<base::subtle::AtomicWord>(histogram_pointer)); \
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} \
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if (DCHECK_IS_ON()) \
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histogram_pointer->CheckName(constant_histogram_name); \
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histogram_pointer->histogram_add_method_invocation; \
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} while (0)
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// This is a helper macro used by other macros and shouldn't be used directly.
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// Defines the static |atomic_histogram_pointer| and forwards to
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// HISTOGRAM_POINTER_USE.
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#define STATIC_HISTOGRAM_POINTER_BLOCK(constant_histogram_name, \
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histogram_add_method_invocation, \
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histogram_factory_get_invocation) \
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do { \
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/* \
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* The pointer's presence indicates that the initialization is complete. \
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* Initialization is idempotent, so it can safely be atomically repeated. \
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*/ \
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static base::subtle::AtomicWord atomic_histogram_pointer = 0; \
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HISTOGRAM_POINTER_USE(&atomic_histogram_pointer, constant_histogram_name, \
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histogram_add_method_invocation, \
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histogram_factory_get_invocation); \
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} while (0)
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// This is a helper macro used by other macros and shouldn't be used directly.
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#define INTERNAL_HISTOGRAM_CUSTOM_COUNTS_WITH_FLAG(name, sample, min, max, \
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bucket_count, flag) \
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STATIC_HISTOGRAM_POINTER_BLOCK( \
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name, Add(sample), \
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base::Histogram::FactoryGet(name, min, max, bucket_count, flag))
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// This is a helper macro used by other macros and shouldn't be used directly.
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// The bucketing scheme is linear with a bucket size of 1. For N items,
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// recording values in the range [0, N - 1] creates a linear histogram with N +
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// 1 buckets:
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// [0, 1), [1, 2), ..., [N - 1, N)
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// and an overflow bucket [N, infinity).
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//
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// Code should never emit to the overflow bucket; only to the other N buckets.
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// This allows future versions of Chrome to safely increase the boundary size.
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// Otherwise, the histogram would have [N - 1, infinity) as its overflow bucket,
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// and so the maximal value (N - 1) would be emitted to this overflow bucket.
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// But, if an additional value were later added, the bucket label for
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// the value (N - 1) would change to [N - 1, N), which would result in different
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// versions of Chrome using different bucket labels for identical data.
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#define INTERNAL_HISTOGRAM_EXACT_LINEAR_WITH_FLAG(name, sample, boundary, \
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flag) \
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do { \
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static_assert(!std::is_enum<decltype(sample)>::value, \
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"|sample| should not be an enum type!"); \
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static_assert(!std::is_enum<decltype(boundary)>::value, \
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"|boundary| should not be an enum type!"); \
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STATIC_HISTOGRAM_POINTER_BLOCK( \
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name, Add(sample), \
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base::LinearHistogram::FactoryGet(name, 1, boundary, boundary + 1, \
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flag)); \
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} while (0)
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// Similar to the previous macro but intended for enumerations. This delegates
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// the work to the previous macro, but supports scoped enumerations as well by
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// forcing an explicit cast to the HistogramBase::Sample integral type.
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//
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// Note the range checks verify two separate issues:
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// - that the declared enum size isn't out of range of HistogramBase::Sample
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// - that the declared enum size is > 0
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//
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// TODO(dcheng): This should assert that the passed in types are actually enum
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// types.
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#define INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary, flag) \
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do { \
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using decayed_sample = std::decay<decltype(sample)>::type; \
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using decayed_boundary = std::decay<decltype(boundary)>::type; \
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static_assert(!std::is_enum<decayed_boundary>::value || \
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std::is_enum<decayed_sample>::value, \
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"Unexpected: |boundary| is enum, but |sample| is not."); \
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static_assert(!std::is_enum<decayed_sample>::value || \
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!std::is_enum<decayed_boundary>::value || \
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std::is_same<decayed_sample, decayed_boundary>::value, \
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"|sample| and |boundary| shouldn't be of different enums"); \
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static_assert( \
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static_cast<uintmax_t>(boundary) < \
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static_cast<uintmax_t>( \
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std::numeric_limits<base::HistogramBase::Sample>::max()), \
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"|boundary| is out of range of HistogramBase::Sample"); \
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INTERNAL_HISTOGRAM_EXACT_LINEAR_WITH_FLAG( \
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name, static_cast<base::HistogramBase::Sample>(sample), \
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static_cast<base::HistogramBase::Sample>(boundary), flag); \
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} while (0)
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// This is a helper macro used by other macros and shouldn't be used directly.
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// This is necessary to expand __COUNTER__ to an actual value.
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#define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_EXPANDER(name, is_long, key) \
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INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, is_long, key)
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// This is a helper macro used by other macros and shouldn't be used directly.
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#define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, is_long, key) \
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class ScopedHistogramTimer##key { \
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public: \
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ScopedHistogramTimer##key() : constructed_(base::TimeTicks::Now()) {} \
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~ScopedHistogramTimer##key() { \
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base::TimeDelta elapsed = base::TimeTicks::Now() - constructed_; \
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if (is_long) { \
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UMA_HISTOGRAM_LONG_TIMES_100(name, elapsed); \
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} else { \
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UMA_HISTOGRAM_TIMES(name, elapsed); \
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} \
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} \
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private: \
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base::TimeTicks constructed_; \
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} scoped_histogram_timer_##key
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// Macro for sparse histogram.
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// The implementation is more costly to add values to, and each value
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// stored has more overhead, compared to the other histogram types. However it
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// may be more efficient in memory if the total number of sample values is small
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// compared to the range of their values.
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#define INTERNAL_HISTOGRAM_SPARSE_SLOWLY(name, sample) \
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do { \
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base::HistogramBase* histogram = base::SparseHistogram::FactoryGet( \
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name, base::HistogramBase::kUmaTargetedHistogramFlag); \
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histogram->Add(sample); \
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} while (0)
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#endif // BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_
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