Export of internal Abseil changes

--
3a871e2cd854a46770a9416189953b2b38980bcf by Andy Getzendanner <durandal@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 280660534

--
f5a155fb056dcf68b089c21aebb5bf5159dc0eb3 by Tom Manshreck <shreck@google.com>:

Nit: fix format of algorithm.h comments

PiperOrigin-RevId: 280474139

--
08b117a18353c0daf51b33b45100e5a007e5ab0c by Abseil Team <absl-team@google.com>:

Allow absl::Notification::HasBeenNotified to be inlined.

PiperOrigin-RevId: 280453271

--
26d33dd2bad72945f1987f7b2669dbec3a6247e6 by Derek Mauro <dmauro@google.com>:

Fix unused variable warnings on Windows

PiperOrigin-RevId: 280324417

--
907e9b23029be683af3b443bafd6a577a595922f by Abseil Team <absl-team@google.com>:

PeriodicSampler implementation (for internal-use only)

PiperOrigin-RevId: 280257168
GitOrigin-RevId: 3a871e2cd854a46770a9416189953b2b38980bcf
Change-Id: I6e2978cae22a6adc41c0577e5c21355e9db7c8f5
This commit is contained in:
Abseil Team 2019-11-15 08:07:12 -08:00 committed by Andy Getz
parent fa8c75182f
commit 3df7b52a6a
12 changed files with 581 additions and 19 deletions

View file

@ -84,6 +84,8 @@ It RotateImpl(It first, It middle, It last, std::false_type) {
} // namespace algorithm_internal
// equal()
//
// Compares the equality of two ranges specified by pairs of iterators, using
// the given predicate, returning true iff for each corresponding iterator i1
// and i2 in the first and second range respectively, pred(*i1, *i2) == true
@ -104,8 +106,8 @@ bool equal(InputIter1 first1, InputIter1 last1, InputIter2 first2,
typename std::iterator_traits<InputIter2>::iterator_category{});
}
// Performs comparison of two ranges specified by pairs of iterators using
// operator==.
// Overload of equal() that performs comparison of two ranges specified by pairs
// of iterators using operator==.
template <typename InputIter1, typename InputIter2>
bool equal(InputIter1 first1, InputIter1 last1, InputIter2 first2,
InputIter2 last2) {
@ -113,6 +115,8 @@ bool equal(InputIter1 first1, InputIter1 last1, InputIter2 first2,
algorithm_internal::EqualTo{});
}
// linear_search()
//
// Performs a linear search for `value` using the iterator `first` up to
// but not including `last`, returning true if [`first`, `last`) contains an
// element equal to `value`.
@ -126,6 +130,8 @@ bool linear_search(InputIterator first, InputIterator last,
return std::find(first, last, value) != last;
}
// rotate()
//
// Performs a left rotation on a range of elements (`first`, `last`) such that
// `middle` is now the first element. `rotate()` returns an iterator pointing to
// the first element before rotation. This function is exactly the same as
@ -135,7 +141,6 @@ bool linear_search(InputIterator first, InputIterator last,
// The complexity of this algorithm is the same as that of `std::rotate`, but if
// `ForwardIterator` is not a random-access iterator, then `absl::rotate`
// performs an additional pass over the range to construct the return value.
template <typename ForwardIterator>
ForwardIterator rotate(ForwardIterator first, ForwardIterator middle,
ForwardIterator last) {

View file

@ -585,6 +585,47 @@ cc_test(
],
)
cc_library(
name = "periodic_sampler",
srcs = ["internal/periodic_sampler.cc"],
hdrs = ["internal/periodic_sampler.h"],
copts = ABSL_DEFAULT_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
":core_headers",
":exponential_biased",
],
)
cc_test(
name = "periodic_sampler_test",
size = "small",
srcs = ["internal/periodic_sampler_test.cc"],
copts = ABSL_TEST_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
visibility = ["//visibility:private"],
deps = [
":core_headers",
":periodic_sampler",
"@com_google_googletest//:gtest_main",
],
)
cc_binary(
name = "periodic_sampler_benchmark",
testonly = 1,
srcs = ["internal/periodic_sampler_benchmark.cc"],
copts = ABSL_TEST_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
tags = ["benchmark"],
visibility = ["//visibility:private"],
deps = [
":core_headers",
":periodic_sampler",
"@com_github_google_benchmark//:benchmark_main",
],
)
cc_library(
name = "scoped_set_env",
testonly = 1,

View file

@ -534,6 +534,33 @@ absl_cc_test(
gmock_main
)
absl_cc_library(
NAME
periodic_sampler
SRCS
"internal/periodic_sampler.cc"
HDRS
"internal/periodic_sampler.h"
COPTS
${ABSL_DEFAULT_COPTS}
DEPS
absl::core_headers
absl::exponential_biased
)
absl_cc_test(
NAME
periodic_sampler_test
SRCS
"internal/periodic_sampler_test.cc"
COPTS
${ABSL_TEST_COPTS}
DEPS
absl::core_headers
absl::periodic_sampler
gmock_main
)
absl_cc_library(
NAME
scoped_set_env

View file

@ -0,0 +1,50 @@
// Copyright 2019 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/base/internal/periodic_sampler.h"
#include <atomic>
#include "absl/base/internal/exponential_biased.h"
namespace absl {
namespace base_internal {
int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
return rng_.Get(period);
}
bool PeriodicSamplerBase::SubtleConfirmSample() noexcept {
int current_period = period();
// Deal with period case 0 (always off) and 1 (always on)
if (ABSL_PREDICT_FALSE(current_period < 2)) {
stride_ = 0;
return current_period == 1;
}
// Check if this is the first call to Sample()
if (ABSL_PREDICT_FALSE(stride_ == 1)) {
stride_ = -1 - GetExponentialBiased(current_period);
if (stride_ < -1) {
++stride_;
return false;
}
}
stride_ = -1 - GetExponentialBiased(current_period);
return true;
}
} // namespace base_internal
} // namespace absl

View file

@ -0,0 +1,193 @@
// Copyright 2019 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_
#define ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_
#include <stdint.h>
#include <atomic>
#include "absl/base/internal/exponential_biased.h"
#include "absl/base/optimization.h"
namespace absl {
namespace base_internal {
// PeriodicSamplerBase provides the basic period sampler implementation.
//
// This is the base class for the templated PeriodicSampler class, which holds
// a global std::atomic value identified by a user defined tag, such that
// each specific PeriodSampler implementation holds its own global period.
//
// PeriodicSamplerBase is thread-compatible except where stated otherwise.
class PeriodicSamplerBase {
public:
// PeriodicSamplerBase is trivial / copyable / movable / destructible.
PeriodicSamplerBase() = default;
PeriodicSamplerBase(PeriodicSamplerBase&&) = default;
PeriodicSamplerBase(const PeriodicSamplerBase&) = default;
// Returns true roughly once every `period` calls. This is established by a
// randomly picked `stride` that is counted down on each call to `Sample`.
// This stride is picked such that the probability of `Sample()` returning
// true is 1 in `period`.
inline bool Sample() noexcept;
// The below methods are intended for optimized use cases where the
// size of the inlined fast path code is highly important. Applications
// should use the `Sample()` method unless they have proof that their
// specific use case requires the optimizations offered by these methods.
//
// An example of such a use case is SwissTable sampling. All sampling checks
// are in inlined SwissTable methods, and the number of call sites is huge.
// In this case, the inlined code size added to each translation unit calling
// SwissTable methods is non-trivial.
//
// The `SubtleMaybeSample()` function spuriously returns true even if the
// function should not be sampled, applications MUST match each call to
// 'SubtleMaybeSample()' returning true with a `SubtleConfirmSample()` call,
// and use the result of the latter as the sampling decision.
// In other words: the code should logically be equivalent to:
//
// if (SubtleMaybeSample() && SubtleConfirmSample()) {
// // Sample this call
// }
//
// In the 'inline-size' optimized case, the `SubtleConfirmSample()` call can
// be placed out of line, for example, the typical use case looks as follows:
//
// // --- frobber.h -----------
// void FrobberSampled();
//
// inline void FrobberImpl() {
// // ...
// }
//
// inline void Frobber() {
// if (ABSL_PREDICT_FALSE(sampler.SubtleMaybeSample())) {
// FrobberSampled();
// } else {
// FrobberImpl();
// }
// }
//
// // --- frobber.cc -----------
// void FrobberSampled() {
// if (!sampler.SubtleConfirmSample())) {
// // Spurious false positive
// FrobberImpl();
// return;
// }
//
// // Sampled execution
// // ...
// }
inline bool SubtleMaybeSample() noexcept;
bool SubtleConfirmSample() noexcept;
protected:
// We explicitly don't use a virtual destructor as this class is never
// virtually destroyed, and it keeps the class trivial, which avoids TLS
// prologue and epilogue code for our TLS instances.
~PeriodicSamplerBase() = default;
// Returns the next stride for our sampler.
// This function is virtual for testing purposes only.
virtual int64_t GetExponentialBiased(int period) noexcept;
private:
// Returns the current period of this sampler. Thread-safe.
virtual int period() const noexcept = 0;
int64_t stride_ = 0;
ExponentialBiased rng_;
};
inline bool PeriodicSamplerBase::SubtleMaybeSample() noexcept {
// We explicitly count up and not down, as the compiler does not generate
// ideal code for counting down. See also https://gcc.godbolt.org/z/FTPDSM
//
// With `if (ABSL_PREDICT_FALSE(++stride_ < 0))`
// add QWORD PTR fs:sampler@tpoff+8, 1
// jns .L15
// ret
//
// With `if (ABSL_PREDICT_FALSE(--stride_ > 0))`
// mov rax, QWORD PTR fs:sampler@tpoff+8
// sub rax, 1
// mov QWORD PTR fs:sampler@tpoff+8, rax
// test rax, rax
// jle .L15
// ret
// add QWORD PTR fs:sampler@tpoff+8, 1
// jns .L15
// ret
//
// --stride >= 0 does work, but makes our logic slightly harder as in that
// case we have less convenient zero-init and over-run values.
if (ABSL_PREDICT_FALSE(++stride_ < 0)) {
return false;
}
return true;
}
inline bool PeriodicSamplerBase::Sample() noexcept {
return ABSL_PREDICT_FALSE(SubtleMaybeSample()) ? SubtleConfirmSample()
: false;
}
// PeriodicSampler is a concreted periodic sampler implementation.
// The user provided Tag identifies the implementation, and is required to
// isolate the global state of this instance from other instances.
//
// Typical use case:
//
// struct HashTablezTag {};
// thread_local PeriodicSampler sampler;
//
// void HashTableSamplingLogic(...) {
// if (sampler.Sample()) {
// HashTableSlowSamplePath(...);
// }
// }
//
template <typename Tag, int default_period = 0>
class PeriodicSampler final : public PeriodicSamplerBase {
public:
~PeriodicSampler() = default;
int period() const noexcept final {
return period_.load(std::memory_order_relaxed);
}
// Sets the global period for this sampler. Thread-safe.
// Setting a period of 0 disables the sampler, i.e., every call to Sample()
// will return false. Setting a period of 1 puts the sampler in 'always on'
// mode, i.e., every call to Sample() returns true.
static void SetGlobalPeriod(int period) {
period_.store(period, std::memory_order_relaxed);
}
private:
static std::atomic<int> period_;
};
template <typename Tag, int default_period>
std::atomic<int> PeriodicSampler<Tag, default_period>::period_(default_period);
} // namespace base_internal
} // namespace absl
#endif // ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_

View file

@ -0,0 +1,70 @@
// Copyright 2019 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "benchmark/benchmark.h"
#include "absl/base/internal/periodic_sampler.h"
namespace absl {
namespace base_internal {
namespace {
template <typename Sampler>
void BM_Sample(Sampler* sampler, benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(sampler);
benchmark::DoNotOptimize(sampler->Sample());
}
}
template <typename Sampler>
void BM_SampleMinunumInlined(Sampler* sampler, benchmark::State& state) {
for (auto _ : state) {
benchmark::DoNotOptimize(sampler);
if (ABSL_PREDICT_FALSE(sampler->SubtleMaybeSample())) {
benchmark::DoNotOptimize(sampler->SubtleConfirmSample());
}
}
}
void BM_PeriodicSampler_ShortSample(benchmark::State& state) {
struct Tag {};
PeriodicSampler<Tag, 1024> sampler;
BM_Sample(&sampler, state);
}
BENCHMARK(BM_PeriodicSampler_ShortSample);
void BM_PeriodicSampler_LongSample(benchmark::State& state) {
struct Tag {};
PeriodicSampler<Tag, 1024 * 1024> sampler;
BM_Sample(&sampler, state);
}
BENCHMARK(BM_PeriodicSampler_LongSample);
void BM_PeriodicSampler_LongSampleMinunumInlined(benchmark::State& state) {
struct Tag {};
PeriodicSampler<Tag, 1024 * 1024> sampler;
BM_SampleMinunumInlined(&sampler, state);
}
BENCHMARK(BM_PeriodicSampler_LongSampleMinunumInlined);
void BM_PeriodicSampler_Disabled(benchmark::State& state) {
struct Tag {};
PeriodicSampler<Tag, 0> sampler;
BM_Sample(&sampler, state);
}
BENCHMARK(BM_PeriodicSampler_Disabled);
} // namespace
} // namespace base_internal
} // namespace absl

View file

@ -0,0 +1,175 @@
// Copyright 2019 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/base/internal/periodic_sampler.h"
#include <thread> // NOLINT(build/c++11)
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/base/attributes.h"
#include "absl/base/macros.h"
namespace absl {
namespace base_internal {
namespace {
using testing::Eq;
using testing::Return;
using testing::StrictMock;
class MockPeriodicSampler : public PeriodicSamplerBase {
public:
virtual ~MockPeriodicSampler() = default;
MOCK_METHOD(int, period, (), (const, noexcept));
MOCK_METHOD(int64_t, GetExponentialBiased, (int), (noexcept));
};
TEST(PeriodicSamplerBaseTest, Sample) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(16));
EXPECT_CALL(sampler, GetExponentialBiased(16))
.WillOnce(Return(1))
.WillOnce(Return(2))
.WillOnce(Return(3));
EXPECT_FALSE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
}
TEST(PeriodicSamplerBaseTest, ImmediatelySample) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(16));
EXPECT_CALL(sampler, GetExponentialBiased(16))
.WillOnce(Return(0))
.WillOnce(Return(1))
.WillOnce(Return(2));
EXPECT_TRUE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
}
TEST(PeriodicSamplerBaseTest, Disabled) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(0));
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
}
TEST(PeriodicSamplerBaseTest, AlwaysOn) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).Times(3).WillRepeatedly(Return(1));
EXPECT_TRUE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
}
TEST(PeriodicSamplerBaseTest, Disable) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).WillOnce(Return(16));
EXPECT_CALL(sampler, GetExponentialBiased(16)).WillOnce(Return(2));
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(0));
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
}
TEST(PeriodicSamplerBaseTest, Enable) {
StrictMock<MockPeriodicSampler> sampler;
EXPECT_CALL(sampler, period()).WillOnce(Return(0));
EXPECT_FALSE(sampler.Sample());
EXPECT_CALL(sampler, period()).Times(2).WillRepeatedly(Return(16));
EXPECT_CALL(sampler, GetExponentialBiased(16))
.Times(2)
.WillRepeatedly(Return(2));
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_TRUE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
EXPECT_FALSE(sampler.Sample());
}
TEST(PeriodicSamplerTest, ConstructConstInit) {
struct Tag {};
ABSL_CONST_INIT static PeriodicSampler<Tag> sampler;
(void)sampler;
}
TEST(PeriodicSamplerTest, DefaultPeriod0) {
struct Tag {};
PeriodicSampler<Tag> sampler;
EXPECT_THAT(sampler.period(), Eq(0));
}
TEST(PeriodicSamplerTest, DefaultPeriod) {
struct Tag {};
PeriodicSampler<Tag, 100> sampler;
EXPECT_THAT(sampler.period(), Eq(100));
}
TEST(PeriodicSamplerTest, SetGlobalPeriod) {
struct Tag1 {};
struct Tag2 {};
PeriodicSampler<Tag1, 25> sampler1;
PeriodicSampler<Tag2, 50> sampler2;
EXPECT_THAT(sampler1.period(), Eq(25));
EXPECT_THAT(sampler2.period(), Eq(50));
std::thread thread([] {
PeriodicSampler<Tag1, 25> sampler1;
PeriodicSampler<Tag2, 50> sampler2;
EXPECT_THAT(sampler1.period(), Eq(25));
EXPECT_THAT(sampler2.period(), Eq(50));
sampler1.SetGlobalPeriod(10);
sampler2.SetGlobalPeriod(20);
});
thread.join();
EXPECT_THAT(sampler1.period(), Eq(10));
EXPECT_THAT(sampler2.period(), Eq(20));
}
} // namespace
} // namespace base_internal
} // namespace absl

View file

@ -54,7 +54,7 @@ static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn =
template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
const void *ucp, int *min_dropped_frames) {
const void*, int* min_dropped_frames) {
int n = 0;
if (!RtlCaptureStackBackTrace_fn) {
// can't find a stacktrace with no function to call

View file

@ -34,7 +34,7 @@ namespace absl {
static HANDLE process = NULL;
void InitializeSymbolizer(const char *argv0) {
void InitializeSymbolizer(const char*) {
if (process != nullptr) {
return;
}

View file

@ -44,15 +44,6 @@ Notification::~Notification() {
MutexLock l(&this->mutex_);
}
static inline bool HasBeenNotifiedInternal(
const std::atomic<bool> *notified_yet) {
return notified_yet->load(std::memory_order_acquire);
}
bool Notification::HasBeenNotified() const {
return HasBeenNotifiedInternal(&this->notified_yet_);
}
void Notification::WaitForNotification() const {
if (!HasBeenNotifiedInternal(&this->notified_yet_)) {
this->mutex_.LockWhen(Condition(&HasBeenNotifiedInternal,

View file

@ -73,7 +73,9 @@ class Notification {
// Notification::HasBeenNotified()
//
// Returns the value of the notification's internal "notified" state.
bool HasBeenNotified() const;
bool HasBeenNotified() const {
return HasBeenNotifiedInternal(&this->notified_yet_);
}
// Notification::WaitForNotification()
//
@ -105,6 +107,11 @@ class Notification {
void Notify();
private:
static inline bool HasBeenNotifiedInternal(
const std::atomic<bool>* notified_yet) {
return notified_yet->load(std::memory_order_acquire);
}
mutable Mutex mutex_;
std::atomic<bool> notified_yet_; // written under mutex_
};

View file

@ -49,10 +49,13 @@ std::unique_ptr<absl::time_internal::cctz::ZoneInfoSource> DefaultFactory(
#if !defined(__has_attribute)
#define __has_attribute(x) 0
#endif
#if __has_attribute(weak) || defined(__GNUC__)
// MinGW is GCC on Windows, so while it asserts __has_attribute(weak), the
// Windows linker cannot handle that. Nor does the MinGW compiler know how to
// pass "#pragma comment(linker, ...)" to the Windows linker.
#if (__has_attribute(weak) || defined(__GNUC__)) && !defined(__MINGW32__)
ZoneInfoSourceFactory zone_info_source_factory
__attribute__((weak)) = DefaultFactory;
#elif defined(_MSC_VER) && !defined(_LIBCPP_VERSION)
#elif defined(_MSC_VER) && !defined(__MINGW32__) && !defined(_LIBCPP_VERSION)
extern ZoneInfoSourceFactory zone_info_source_factory;
extern ZoneInfoSourceFactory default_factory;
ZoneInfoSourceFactory default_factory = DefaultFactory;