From 46dfbfe31ca1dd414e4c33cbcbcd7199bb4efde3 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Wed, 14 Apr 2021 11:19:20 -0700 Subject: Export of internal Abseil changes -- 5ff0c4b38386ae80b25e9f8d0e1bac07fd7ce92c by Martijn Vels : Add CordzUpdateTracker class PiperOrigin-RevId: 368469046 -- 4de916b1ba4b5480b4dbe93d28c5eaa110449c66 by Derek Mauro : Adds `ABSL_ATTRIBUTE_LIFETIME_BOUND` to `absl::Span`s initializer_list constructor. Compilers that support this attribute will emit a warning if the parameter does not have sufficient lifetime. For more information, see https://github.com/abseil/abseil-cpp/blob/b97a1ecda869ca8754d467a56c50275cebfeb328/absl/types/span.h#L209-L248 PiperOrigin-RevId: 368429085 -- bb6669016412bf5afffc02d0818a66dfe1c524cf by Martijn Vels : Reorganize internal cord code in CMakeLists.txt into cord_internal library PiperOrigin-RevId: 368423765 -- d1d7fce066172d5fcfa0310c4e27631d895d7e50 by Derek Mauro : Internal change PiperOrigin-RevId: 368346725 GitOrigin-RevId: 5ff0c4b38386ae80b25e9f8d0e1bac07fd7ce92c Change-Id: Ic4627eab4f0274e400a6d12cde3341fb538de075 --- absl/strings/internal/cordz_update_tracker.h | 96 +++++++++++++++ absl/strings/internal/cordz_update_tracker_test.cc | 130 +++++++++++++++++++++ 2 files changed, 226 insertions(+) create mode 100644 absl/strings/internal/cordz_update_tracker.h create mode 100644 absl/strings/internal/cordz_update_tracker_test.cc (limited to 'absl/strings/internal') diff --git a/absl/strings/internal/cordz_update_tracker.h b/absl/strings/internal/cordz_update_tracker.h new file mode 100644 index 00000000..3c617e93 --- /dev/null +++ b/absl/strings/internal/cordz_update_tracker.h @@ -0,0 +1,96 @@ +// Copyright 2021 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_STRINGS_INTERNAL_CORDZ_UPDATE_TRACKER_H_ +#define ABSL_STRINGS_INTERNAL_CORDZ_UPDATE_TRACKER_H_ + +#include +#include + +#include "absl/base/config.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +// CordzUpdateTracker tracks counters for Cord update methods. +// +// The purpose of CordzUpdateTracker is to track the number of calls to methods +// updating Cord data for sampled cords. The class internally uses 'lossy' +// atomic operations: Cord is thread-compatible, so there is no need to +// synchronize updates. However, Cordz collection threads may call 'Value()' at +// any point, so the class needs to provide thread safe access. +// +// This class is thread-safe. But as per above comments, all non-const methods +// should be used single-threaded only: updates are thread-safe but lossy. +class CordzUpdateTracker { + public: + // Tracked update methods. + enum MethodIdentifier { + kAssignString, + kAssignCord, + kMoveAssignCord, + kAppendString, + kAppendCord, + kMoveAppendCord, + kPrependString, + kPrependCord, + kMovePrependCord, + kAppendExternalMemory, + kFlatten, + kGetAppendRegion, + kRemovePrefix, + kRemoveSuffic, + kSubCord, + + // kNumMethods defines the number of entries: must be the last entry. + kNumMethods, + }; + + // Constructs a new instance. All counters are zero-initialized. + constexpr CordzUpdateTracker() noexcept : values_{} {} + + // Copy constructs a new instance. + CordzUpdateTracker(const CordzUpdateTracker& rhs) noexcept { *this = rhs; } + + // Assigns the provided value to this instance. + CordzUpdateTracker& operator=(const CordzUpdateTracker& rhs) noexcept { + for (int i = 0; i < kNumMethods; ++i) { + values_[i].store(rhs.values_[i].load(std::memory_order_relaxed), + std::memory_order_relaxed); + } + return *this; + } + + // Returns the value for the specified method. + int64_t Value(MethodIdentifier method) const { + return values_[method].load(std::memory_order_relaxed); + } + + // Increases the value for the specified method by `n` + void LossyAdd(MethodIdentifier method, int64_t n = 1) { + auto& value = values_[method]; + value.store(value.load(std::memory_order_relaxed) + n, + std::memory_order_relaxed); + } + + private: + std::atomic values_[kNumMethods]; +}; + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_CORDZ_UPDATE_TRACKER_H_ diff --git a/absl/strings/internal/cordz_update_tracker_test.cc b/absl/strings/internal/cordz_update_tracker_test.cc new file mode 100644 index 00000000..45782046 --- /dev/null +++ b/absl/strings/internal/cordz_update_tracker_test.cc @@ -0,0 +1,130 @@ +// Copyright 2021 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/strings/internal/cordz_update_tracker.h" + +#include +#include // NOLINT + +#include "gmock/gmock.h" +#include "gtest/gtest.h" +#include "absl/base/attributes.h" +#include "absl/base/config.h" +#include "absl/synchronization/notification.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { +namespace { + +using ::testing::AnyOf; +using ::testing::Eq; + +using Method = CordzUpdateTracker::MethodIdentifier; +using Methods = std::array; + +// Returns an array of all methods defined in `MethodIdentifier` +Methods AllMethods() { + return Methods{Method::kAssignString, Method::kAssignCord, + Method::kMoveAssignCord, Method::kAppendString, + Method::kAppendCord, Method::kMoveAppendCord, + Method::kPrependString, Method::kPrependCord, + Method::kMovePrependCord, Method::kAppendExternalMemory, + Method::kFlatten, Method::kGetAppendRegion, + Method::kRemovePrefix, Method::kRemoveSuffic, + Method::kSubCord}; +} + +TEST(CordzUpdateTracker, IsConstExprAndInitializesToZero) { + constexpr CordzUpdateTracker tracker; + for (Method method : AllMethods()) { + ASSERT_THAT(tracker.Value(method), Eq(0)); + } +} + +TEST(CordzUpdateTracker, LossyAdd) { + int64_t n = 1; + CordzUpdateTracker tracker; + for (Method method : AllMethods()) { + tracker.LossyAdd(method, n); + EXPECT_THAT(tracker.Value(method), Eq(n)); + n += 2; + } +} + +TEST(CordzUpdateTracker, CopyConstructor) { + int64_t n = 1; + CordzUpdateTracker src; + for (Method method : AllMethods()) { + src.LossyAdd(method, n); + n += 2; + } + + n = 1; + CordzUpdateTracker tracker(src); + for (Method method : AllMethods()) { + EXPECT_THAT(tracker.Value(method), Eq(n)); + n += 2; + } +} + +TEST(CordzUpdateTracker, OperatorAssign) { + int64_t n = 1; + CordzUpdateTracker src; + CordzUpdateTracker tracker; + for (Method method : AllMethods()) { + src.LossyAdd(method, n); + n += 2; + } + + n = 1; + tracker = src; + for (Method method : AllMethods()) { + EXPECT_THAT(tracker.Value(method), Eq(n)); + n += 2; + } +} + +TEST(CordzUpdateTracker, ThreadSanitizedValueCheck) { + absl::Notification done; + CordzUpdateTracker tracker; + + std::thread reader([&done, &tracker] { + while (!done.HasBeenNotified()) { + int n = 1; + for (Method method : AllMethods()) { + EXPECT_THAT(tracker.Value(method), AnyOf(Eq(n), Eq(0))); + n += 2; + } + } + int n = 1; + for (Method method : AllMethods()) { + EXPECT_THAT(tracker.Value(method), Eq(n)); + n += 2; + } + }); + + int64_t n = 1; + for (Method method : AllMethods()) { + tracker.LossyAdd(method, n); + n += 2; + } + done.Notify(); + reader.join(); +} + +} // namespace +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl -- cgit v1.2.3