-- 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: I6e2978cae22a6adc41c0577e5c21355e9db7c8f5pull/404/head
Abseil Team
5 years ago
committed by
Andy Getz
parent
fa8c75182f
commit
3df7b52a6a
12 changed files with 581 additions and 19 deletions
@ -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
|
||||
@ -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_
|
||||
@ -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
|
||||
@ -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
|
||||
Loading…
Reference in new issue