// Copyright 2016 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_ #define BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_ #include #include #include #include #include #include "base/dcheck_is_on.h" #include "base/metrics/histogram.h" #include "base/metrics/sparse_histogram.h" #include "base/time/time.h" // This is for macros and helpers internal to base/metrics. They should not be // used outside of this directory. For writing to UMA histograms, see // histogram_macros.h. namespace base { namespace internal { // Helper traits for deducing the boundary value for enums. template struct EnumSizeTraits { static constexpr Enum Count() { static_assert( sizeof(Enum) == 0, "enumerator must define kMaxValue enumerator to use this macro!"); return Enum(); } }; // Since the UMA histogram macros expect a value one larger than the max defined // enumerator value, add one. template struct EnumSizeTraits< Enum, std::enable_if_t>> { static constexpr Enum Count() { // If you're getting // note: integer value X is outside the valid range of values [0, X] for // this enumeration type // Then you need to give your enum a fixed underlying type. return static_cast( static_cast>(Enum::kMaxValue) + 1); } }; } // namespace internal } // namespace base // TODO(rkaplow): Improve commenting of these methods. //------------------------------------------------------------------------------ // Histograms are often put in areas where they are called many many times, and // performance is critical. As a result, they are designed to have a very low // recurring cost of executing (adding additional samples). Toward that end, // the macros declare a static pointer to the histogram in question, and only // take a "slow path" to construct (or find) the histogram on the first run // through the macro. We leak the histograms at shutdown time so that we don't // have to validate using the pointers at any time during the running of the // process. // In some cases (integration into 3rd party code), it's useful to separate the // definition of |atomic_histogram_pointer| from its use. To achieve this we // define HISTOGRAM_POINTER_USE, which uses an |atomic_histogram_pointer|, and // STATIC_HISTOGRAM_POINTER_BLOCK, which defines an |atomic_histogram_pointer| // and forwards to HISTOGRAM_POINTER_USE. #define HISTOGRAM_POINTER_USE( \ atomic_histogram_pointer, constant_histogram_name, \ histogram_add_method_invocation, histogram_factory_get_invocation) \ do { \ base::HistogramBase* histogram_pointer( \ reinterpret_cast( \ atomic_histogram_pointer->load(std::memory_order_acquire))); \ if (!histogram_pointer) { \ /* \ * This is the slow path, which will construct OR find the \ * matching histogram. |histogram_factory_get_invocation| includes \ * locks on a global histogram name map and is completely thread \ * safe. \ */ \ histogram_pointer = histogram_factory_get_invocation; \ \ /* \ * We could do this without any barrier, since FactoryGet() \ * entered and exited a lock after construction, but this barrier \ * makes things clear. \ */ \ atomic_histogram_pointer->store( \ reinterpret_cast(histogram_pointer), \ std::memory_order_release); \ } \ if (DCHECK_IS_ON()) \ histogram_pointer->CheckName(constant_histogram_name); \ histogram_pointer->histogram_add_method_invocation; \ } while (0) // This is a helper macro used by other macros and shouldn't be used directly. // Defines the static |atomic_histogram_pointer| and forwards to // HISTOGRAM_POINTER_USE. #define STATIC_HISTOGRAM_POINTER_BLOCK(constant_histogram_name, \ histogram_add_method_invocation, \ histogram_factory_get_invocation) \ do { \ /* \ * The pointer's presence indicates that the initialization is complete. \ * Initialization is idempotent, so it can safely be atomically repeated. \ */ \ static std::atomic_uintptr_t atomic_histogram_pointer; \ HISTOGRAM_POINTER_USE( \ std::addressof(atomic_histogram_pointer), constant_histogram_name, \ histogram_add_method_invocation, histogram_factory_get_invocation); \ } while (0) // This is a helper macro used by other macros and shouldn't be used directly. #define INTERNAL_HISTOGRAM_CUSTOM_COUNTS_WITH_FLAG(name, sample, min, max, \ bucket_count, flag) \ STATIC_HISTOGRAM_POINTER_BLOCK( \ name, Add(sample), \ base::Histogram::FactoryGet(name, min, max, bucket_count, flag)) // This is a helper macro used by other macros and shouldn't be used directly. // The bucketing scheme is linear with a bucket size of 1. For N items, // recording values in the range [0, N - 1] creates a linear histogram with N + // 1 buckets: // [0, 1), [1, 2), ..., [N - 1, N) // and an overflow bucket [N, infinity). // // Code should never emit to the overflow bucket; only to the other N buckets. // This allows future versions of Chrome to safely increase the boundary size. // Otherwise, the histogram would have [N - 1, infinity) as its overflow bucket, // and so the maximal value (N - 1) would be emitted to this overflow bucket. // But, if an additional value were later added, the bucket label for // the value (N - 1) would change to [N - 1, N), which would result in different // versions of Chrome using different bucket labels for identical data. #define INTERNAL_HISTOGRAM_EXACT_LINEAR_WITH_FLAG(name, sample, boundary, \ flag) \ do { \ static_assert(!std::is_enum_v>, \ "|sample| should not be an enum type!"); \ static_assert(!std::is_enum_v>, \ "|boundary| should not be an enum type!"); \ STATIC_HISTOGRAM_POINTER_BLOCK( \ name, Add(sample), \ base::LinearHistogram::FactoryGet(name, 1, boundary, boundary + 1, \ flag)); \ } while (0) // While this behaves the same as the above macro, the wrapping of a linear // histogram with another object to do the scaling means the POINTER_BLOCK // macro can't be used as it is tied to HistogramBase #define INTERNAL_HISTOGRAM_SCALED_EXACT_LINEAR_WITH_FLAG( \ name, sample, count, boundary, scale, flag) \ do { \ static_assert(!std::is_enum_v>, \ "|sample| should not be an enum type!"); \ static_assert(!std::is_enum_v>, \ "|boundary| should not be an enum type!"); \ class ScaledLinearHistogramInstance : public base::ScaledLinearHistogram { \ public: \ ScaledLinearHistogramInstance() \ : ScaledLinearHistogram(name, \ 1, \ boundary, \ boundary + 1, \ scale, \ flag) {} \ }; \ static base::LazyInstance::Leaky \ scaled_leaky; \ scaled_leaky.Get().AddScaledCount(sample, count); \ } while (0) // Helper for 'overloading' UMA_HISTOGRAM_ENUMERATION with a variable number of // arguments. #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_GET_MACRO(_1, _2, NAME, ...) NAME #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_DEDUCE_BOUNDARY(name, sample, \ flags) \ INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG( \ name, sample, \ base::internal::EnumSizeTraits>::Count(), \ flags) // Note: The value in |sample| must be strictly less than |enum_size|. #define INTERNAL_UMA_HISTOGRAM_ENUMERATION_SPECIFY_BOUNDARY(name, sample, \ enum_size, flags) \ INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, enum_size, flags) // Similar to the previous macro but intended for enumerations. This delegates // the work to the previous macro, but supports scoped enumerations as well by // forcing an explicit cast to the HistogramBase::Sample integral type. // // Note the range checks verify two separate issues: // - that the declared enum size isn't out of range of HistogramBase::Sample // - that the declared enum size is > 0 // // TODO(dcheng): This should assert that the passed in types are actually enum // types. #define INTERNAL_HISTOGRAM_ENUMERATION_WITH_FLAG(name, sample, boundary, flag) \ do { \ using decayed_sample = std::decay::type; \ using decayed_boundary = std::decay::type; \ static_assert( \ !std::is_enum_v || std::is_enum_v, \ "Unexpected: |boundary| is enum, but |sample| is not."); \ static_assert(!std::is_enum_v || \ !std::is_enum_v || \ std::is_same_v, \ "|sample| and |boundary| shouldn't be of different enums"); \ static_assert( \ static_cast(boundary) < \ static_cast( \ std::numeric_limits::max()), \ "|boundary| is out of range of HistogramBase::Sample"); \ INTERNAL_HISTOGRAM_EXACT_LINEAR_WITH_FLAG( \ name, static_cast(sample), \ static_cast(boundary), flag); \ } while (0) #define INTERNAL_HISTOGRAM_SCALED_ENUMERATION_WITH_FLAG(name, sample, count, \ scale, flag) \ do { \ using decayed_sample = std::decay::type; \ static_assert(std::is_enum_v, \ "Unexpected: |sample| is not at enum."); \ constexpr auto boundary = base::internal::EnumSizeTraits< \ std::decay_t>::Count(); \ static_assert( \ static_cast(boundary) < \ static_cast( \ std::numeric_limits::max()), \ "|boundary| is out of range of HistogramBase::Sample"); \ INTERNAL_HISTOGRAM_SCALED_EXACT_LINEAR_WITH_FLAG( \ name, static_cast(sample), count, \ static_cast(boundary), scale, flag); \ } while (0) // This is a helper macro used by other macros and shouldn't be used directly. // This is necessary to expand __COUNTER__ to an actual value. #define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_EXPANDER(name, timing, key) \ INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, timing, key) // This is a helper macro used by other macros and shouldn't be used directly. #define INTERNAL_SCOPED_UMA_HISTOGRAM_TIMER_UNIQUE(name, timing, key) \ class ScopedHistogramTimer##key { \ public: \ ScopedHistogramTimer##key() : constructed_(base::TimeTicks::Now()) {} \ ~ScopedHistogramTimer##key() { \ base::TimeDelta elapsed = base::TimeTicks::Now() - constructed_; \ switch (timing) { \ case ScopedHistogramTiming::kMicrosecondTimes: \ UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES( \ name, elapsed, base::Microseconds(1), base::Seconds(1), 50); \ break; \ case ScopedHistogramTiming::kMediumTimes: \ UMA_HISTOGRAM_TIMES(name, elapsed); \ break; \ case ScopedHistogramTiming::kLongTimes: \ UMA_HISTOGRAM_LONG_TIMES_100(name, elapsed); \ break; \ } \ } \ \ private: \ base::TimeTicks constructed_; \ } scoped_histogram_timer_##key #endif // BASE_METRICS_HISTOGRAM_MACROS_INTERNAL_H_