another try
This commit is contained in:
mgthepro
@@ -1,158 +1,158 @@
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// SPDX-FileCopyrightText: Copyright (c) 2020 Erik Rigtorp <erik@rigtorp.se>
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <atomic>
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#include <bit>
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#include <condition_variable>
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#include <memory>
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#include <mutex>
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#include <new>
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#include <stop_token>
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#include <type_traits>
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#include <utility>
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namespace Common {
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#if defined(__cpp_lib_hardware_interference_size)
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constexpr size_t hardware_interference_size = std::hardware_destructive_interference_size;
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#else
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constexpr size_t hardware_interference_size = 64;
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#endif
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template <typename T, size_t capacity = 0x400>
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class MPSCQueue {
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public:
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explicit MPSCQueue() : allocator{std::allocator<Slot<T>>()} {
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// Allocate one extra slot to prevent false sharing on the last slot
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slots = allocator.allocate(capacity + 1);
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// Allocators are not required to honor alignment for over-aligned types
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// (see http://eel.is/c++draft/allocator.requirements#10) so we verify
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// alignment here
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if (reinterpret_cast<uintptr_t>(slots) % alignof(Slot<T>) != 0) {
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allocator.deallocate(slots, capacity + 1);
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throw std::bad_alloc();
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}
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for (size_t i = 0; i < capacity; ++i) {
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std::construct_at(&slots[i]);
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}
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static_assert(std::has_single_bit(capacity), "capacity must be an integer power of 2");
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static_assert(alignof(Slot<T>) == hardware_interference_size,
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"Slot must be aligned to cache line boundary to prevent false sharing");
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static_assert(sizeof(Slot<T>) % hardware_interference_size == 0,
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"Slot size must be a multiple of cache line size to prevent "
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"false sharing between adjacent slots");
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static_assert(sizeof(MPSCQueue) % hardware_interference_size == 0,
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"Queue size must be a multiple of cache line size to "
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"prevent false sharing between adjacent queues");
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}
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~MPSCQueue() noexcept {
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for (size_t i = 0; i < capacity; ++i) {
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std::destroy_at(&slots[i]);
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}
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allocator.deallocate(slots, capacity + 1);
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}
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// The queue must be both non-copyable and non-movable
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MPSCQueue(const MPSCQueue&) = delete;
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MPSCQueue& operator=(const MPSCQueue&) = delete;
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MPSCQueue(MPSCQueue&&) = delete;
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MPSCQueue& operator=(MPSCQueue&&) = delete;
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void Push(const T& v) noexcept {
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static_assert(std::is_nothrow_copy_constructible_v<T>,
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"T must be nothrow copy constructible");
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emplace(v);
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}
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template <typename P, typename = std::enable_if_t<std::is_nothrow_constructible_v<T, P&&>>>
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void Push(P&& v) noexcept {
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emplace(std::forward<P>(v));
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}
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void Pop(T& v, std::stop_token stop) noexcept {
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auto const tail = tail_.fetch_add(1);
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auto& slot = slots[idx(tail)];
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if (!slot.turn.test()) {
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std::unique_lock lock{cv_mutex};
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cv.wait(lock, stop, [&slot] { return slot.turn.test(); });
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}
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v = slot.move();
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slot.destroy();
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slot.turn.clear();
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slot.turn.notify_one();
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}
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private:
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template <typename U = T>
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struct Slot {
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~Slot() noexcept {
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if (turn.test()) {
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destroy();
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}
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}
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template <typename... Args>
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void construct(Args&&... args) noexcept {
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static_assert(std::is_nothrow_constructible_v<U, Args&&...>,
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"T must be nothrow constructible with Args&&...");
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std::construct_at(reinterpret_cast<U*>(&storage), std::forward<Args>(args)...);
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}
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void destroy() noexcept {
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static_assert(std::is_nothrow_destructible_v<U>, "T must be nothrow destructible");
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std::destroy_at(reinterpret_cast<U*>(&storage));
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}
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U&& move() noexcept {
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return reinterpret_cast<U&&>(storage);
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}
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// Align to avoid false sharing between adjacent slots
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alignas(hardware_interference_size) std::atomic_flag turn{};
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struct aligned_store {
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struct type {
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alignas(U) unsigned char data[sizeof(U)];
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};
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};
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typename aligned_store::type storage;
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};
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template <typename... Args>
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void emplace(Args&&... args) noexcept {
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static_assert(std::is_nothrow_constructible_v<T, Args&&...>,
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"T must be nothrow constructible with Args&&...");
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auto const head = head_.fetch_add(1);
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auto& slot = slots[idx(head)];
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slot.turn.wait(true);
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slot.construct(std::forward<Args>(args)...);
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slot.turn.test_and_set();
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cv.notify_one();
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}
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constexpr size_t idx(size_t i) const noexcept {
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return i & mask;
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}
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static constexpr size_t mask = capacity - 1;
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// Align to avoid false sharing between head_ and tail_
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alignas(hardware_interference_size) std::atomic<size_t> head_{0};
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alignas(hardware_interference_size) std::atomic<size_t> tail_{0};
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std::mutex cv_mutex;
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std::condition_variable_any cv;
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Slot<T>* slots;
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[[no_unique_address]] std::allocator<Slot<T>> allocator;
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static_assert(std::is_nothrow_copy_assignable_v<T> || std::is_nothrow_move_assignable_v<T>,
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"T must be nothrow copy or move assignable");
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static_assert(std::is_nothrow_destructible_v<T>, "T must be nothrow destructible");
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};
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} // namespace Common
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// SPDX-FileCopyrightText: Copyright (c) 2020 Erik Rigtorp <erik@rigtorp.se>
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <atomic>
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#include <bit>
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#include <condition_variable>
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#include <memory>
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#include <mutex>
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#include <new>
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#include <stop_token>
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#include <type_traits>
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#include <utility>
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namespace Common {
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#if defined(__cpp_lib_hardware_interference_size)
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constexpr size_t hardware_interference_size = std::hardware_destructive_interference_size;
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#else
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constexpr size_t hardware_interference_size = 64;
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#endif
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template <typename T, size_t capacity = 0x400>
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class MPSCQueue {
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public:
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explicit MPSCQueue() : allocator{std::allocator<Slot<T>>()} {
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// Allocate one extra slot to prevent false sharing on the last slot
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slots = allocator.allocate(capacity + 1);
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// Allocators are not required to honor alignment for over-aligned types
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// (see http://eel.is/c++draft/allocator.requirements#10) so we verify
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// alignment here
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if (reinterpret_cast<uintptr_t>(slots) % alignof(Slot<T>) != 0) {
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allocator.deallocate(slots, capacity + 1);
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throw std::bad_alloc();
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}
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for (size_t i = 0; i < capacity; ++i) {
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std::construct_at(&slots[i]);
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}
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static_assert(std::has_single_bit(capacity), "capacity must be an integer power of 2");
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static_assert(alignof(Slot<T>) == hardware_interference_size,
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"Slot must be aligned to cache line boundary to prevent false sharing");
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static_assert(sizeof(Slot<T>) % hardware_interference_size == 0,
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"Slot size must be a multiple of cache line size to prevent "
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"false sharing between adjacent slots");
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static_assert(sizeof(MPSCQueue) % hardware_interference_size == 0,
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"Queue size must be a multiple of cache line size to "
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"prevent false sharing between adjacent queues");
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}
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~MPSCQueue() noexcept {
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for (size_t i = 0; i < capacity; ++i) {
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std::destroy_at(&slots[i]);
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}
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allocator.deallocate(slots, capacity + 1);
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}
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// The queue must be both non-copyable and non-movable
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MPSCQueue(const MPSCQueue&) = delete;
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MPSCQueue& operator=(const MPSCQueue&) = delete;
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MPSCQueue(MPSCQueue&&) = delete;
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MPSCQueue& operator=(MPSCQueue&&) = delete;
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void Push(const T& v) noexcept {
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static_assert(std::is_nothrow_copy_constructible_v<T>,
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"T must be nothrow copy constructible");
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emplace(v);
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}
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template <typename P, typename = std::enable_if_t<std::is_nothrow_constructible_v<T, P&&>>>
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void Push(P&& v) noexcept {
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emplace(std::forward<P>(v));
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}
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void Pop(T& v, std::stop_token stop) noexcept {
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auto const tail = tail_.fetch_add(1);
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auto& slot = slots[idx(tail)];
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if (!slot.turn.test()) {
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std::unique_lock lock{cv_mutex};
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cv.wait(lock, stop, [&slot] { return slot.turn.test(); });
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}
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v = slot.move();
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slot.destroy();
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slot.turn.clear();
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slot.turn.notify_one();
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}
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private:
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template <typename U = T>
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struct Slot {
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~Slot() noexcept {
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if (turn.test()) {
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destroy();
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}
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}
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template <typename... Args>
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void construct(Args&&... args) noexcept {
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static_assert(std::is_nothrow_constructible_v<U, Args&&...>,
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"T must be nothrow constructible with Args&&...");
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std::construct_at(reinterpret_cast<U*>(&storage), std::forward<Args>(args)...);
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}
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void destroy() noexcept {
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static_assert(std::is_nothrow_destructible_v<U>, "T must be nothrow destructible");
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std::destroy_at(reinterpret_cast<U*>(&storage));
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}
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U&& move() noexcept {
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return reinterpret_cast<U&&>(storage);
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}
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// Align to avoid false sharing between adjacent slots
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alignas(hardware_interference_size) std::atomic_flag turn{};
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struct aligned_store {
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struct type {
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alignas(U) unsigned char data[sizeof(U)];
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};
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};
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typename aligned_store::type storage;
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};
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template <typename... Args>
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void emplace(Args&&... args) noexcept {
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static_assert(std::is_nothrow_constructible_v<T, Args&&...>,
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"T must be nothrow constructible with Args&&...");
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auto const head = head_.fetch_add(1);
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auto& slot = slots[idx(head)];
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slot.turn.wait(true);
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slot.construct(std::forward<Args>(args)...);
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slot.turn.test_and_set();
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cv.notify_one();
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}
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constexpr size_t idx(size_t i) const noexcept {
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return i & mask;
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}
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static constexpr size_t mask = capacity - 1;
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// Align to avoid false sharing between head_ and tail_
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alignas(hardware_interference_size) std::atomic<size_t> head_{0};
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alignas(hardware_interference_size) std::atomic<size_t> tail_{0};
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std::mutex cv_mutex;
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std::condition_variable_any cv;
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Slot<T>* slots;
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[[no_unique_address]] std::allocator<Slot<T>> allocator;
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static_assert(std::is_nothrow_copy_assignable_v<T> || std::is_nothrow_move_assignable_v<T>,
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"T must be nothrow copy or move assignable");
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static_assert(std::is_nothrow_destructible_v<T>, "T must be nothrow destructible");
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};
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} // namespace Common
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