From 25429998e373c12287ae8da2a1c9c1bbe7bd7047 Mon Sep 17 00:00:00 2001
From: Morph <39850852+Morph1984@users.noreply.github.com>
Date: Tue, 14 Jun 2022 08:57:19 -0400
Subject: [PATCH] bounded_threadsafe_queue: Use constexpr capacity and mask
While this is the primary change, we also:
- Remove the mpsc namespace and rename Queue to MPSCQueue
- Make Slot a private struct within MPSCQueue
- Remove the AlignedAllocator template argument, as we use std::allocator
- Replace instances of mask + 1 with capacity, and mask + 2 with capacity + 1
---
src/common/bounded_threadsafe_queue.h | 159 ++++++++++++--------------
src/video_core/gpu_thread.h | 2 +-
2 files changed, 74 insertions(+), 87 deletions(-)
diff --git a/src/common/bounded_threadsafe_queue.h b/src/common/bounded_threadsafe_queue.h
index e83064c7f0..7e465549bd 100644
--- a/src/common/bounded_threadsafe_queue.h
+++ b/src/common/bounded_threadsafe_queue.h
@@ -1,10 +1,7 @@
// SPDX-FileCopyrightText: Copyright (c) 2020 Erik Rigtorp <erik@rigtorp.se>
// SPDX-License-Identifier: MIT
+
#pragma once
-#ifdef _MSC_VER
-#pragma warning(push)
-#pragma warning(disable : 4324)
-#endif
#include <atomic>
#include <bit>
@@ -12,105 +9,63 @@
#include <memory>
#include <mutex>
#include <new>
-#include <stdexcept>
#include <stop_token>
#include <type_traits>
#include <utility>
namespace Common {
-namespace mpsc {
+
#if defined(__cpp_lib_hardware_interference_size)
constexpr size_t hardware_interference_size = std::hardware_destructive_interference_size;
#else
constexpr size_t hardware_interference_size = 64;
#endif
-template <typename T>
-using AlignedAllocator = std::allocator<T>;
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4324)
+#endif
-template <typename T>
-struct Slot {
- ~Slot() noexcept {
- if (turn.test()) {
- destroy();
- }
- }
-
- template <typename... Args>
- void construct(Args&&... args) noexcept {
- static_assert(std::is_nothrow_constructible_v<T, Args&&...>,
- "T must be nothrow constructible with Args&&...");
- std::construct_at(reinterpret_cast<T*>(&storage), std::forward<Args>(args)...);
- }
-
- void destroy() noexcept {
- static_assert(std::is_nothrow_destructible_v<T>, "T must be nothrow destructible");
- std::destroy_at(reinterpret_cast<T*>(&storage));
- }
-
- T&& move() noexcept {
- return reinterpret_cast<T&&>(storage);
- }
-
- // Align to avoid false sharing between adjacent slots
- alignas(hardware_interference_size) std::atomic_flag turn{};
- struct aligned_store {
- struct type {
- alignas(T) unsigned char data[sizeof(T)];
- };
- };
- typename aligned_store::type storage;
-};
-
-template <typename T, typename Allocator = AlignedAllocator<Slot<T>>>
-class Queue {
+template <typename T, size_t capacity = 0x400>
+class MPSCQueue {
public:
- explicit Queue(const size_t capacity, const Allocator& allocator = Allocator())
- : allocator_(allocator) {
- if (capacity < 1) {
- throw std::invalid_argument("capacity < 1");
- }
- // Ensure that the queue length is an integer power of 2
- // This is so that idx(i) can be a simple i & mask_ insted of i % capacity
- // https://github.com/rigtorp/MPMCQueue/pull/36
- if (!std::has_single_bit(capacity)) {
- throw std::invalid_argument("capacity must be an integer power of 2");
- }
-
- mask_ = capacity - 1;
-
+ explicit MPSCQueue() : allocator{std::allocator<Slot<T>>()} {
// Allocate one extra slot to prevent false sharing on the last slot
- slots_ = allocator_.allocate(mask_ + 2);
+ slots = allocator.allocate(capacity + 1);
// Allocators are not required to honor alignment for over-aligned types
// (see http://eel.is/c++draft/allocator.requirements#10) so we verify
// alignment here
- if (reinterpret_cast<uintptr_t>(slots_) % alignof(Slot<T>) != 0) {
- allocator_.deallocate(slots_, mask_ + 2);
+ if (reinterpret_cast<uintptr_t>(slots) % alignof(Slot<T>) != 0) {
+ allocator.deallocate(slots, capacity + 1);
throw std::bad_alloc();
}
- for (size_t i = 0; i < mask_ + 1; ++i) {
- std::construct_at(&slots_[i]);
+ for (size_t i = 0; i < capacity; ++i) {
+ std::construct_at(&slots[i]);
}
+ static_assert(std::has_single_bit(capacity), "capacity must be an integer power of 2");
static_assert(alignof(Slot<T>) == hardware_interference_size,
"Slot must be aligned to cache line boundary to prevent false sharing");
static_assert(sizeof(Slot<T>) % hardware_interference_size == 0,
"Slot size must be a multiple of cache line size to prevent "
"false sharing between adjacent slots");
- static_assert(sizeof(Queue) % hardware_interference_size == 0,
+ static_assert(sizeof(MPSCQueue) % hardware_interference_size == 0,
"Queue size must be a multiple of cache line size to "
"prevent false sharing between adjacent queues");
}
- ~Queue() noexcept {
- for (size_t i = 0; i < mask_ + 1; ++i) {
- slots_[i].~Slot();
+ ~MPSCQueue() noexcept {
+ for (size_t i = 0; i < capacity; ++i) {
+ std::destroy_at(&slots[i]);
}
- allocator_.deallocate(slots_, mask_ + 2);
+ allocator.deallocate(slots, capacity + 1);
}
- // non-copyable and non-movable
- Queue(const Queue&) = delete;
- Queue& operator=(const Queue&) = delete;
+ // The queue must be both non-copyable and non-movable
+ MPSCQueue(const MPSCQueue&) = delete;
+ MPSCQueue& operator=(const MPSCQueue&) = delete;
+
+ MPSCQueue(MPSCQueue&&) = delete;
+ MPSCQueue& operator=(MPSCQueue&&) = delete;
void Push(const T& v) noexcept {
static_assert(std::is_nothrow_copy_constructible_v<T>,
@@ -125,8 +80,8 @@ public:
void Pop(T& v, std::stop_token stop) noexcept {
auto const tail = tail_.fetch_add(1);
- auto& slot = slots_[idx(tail)];
- if (false == slot.turn.test()) {
+ auto& slot = slots[idx(tail)];
+ if (!slot.turn.test()) {
std::unique_lock lock{cv_mutex};
cv.wait(lock, stop, [&slot] { return slot.turn.test(); });
}
@@ -137,12 +92,46 @@ public:
}
private:
+ template <typename U = T>
+ struct Slot {
+ ~Slot() noexcept {
+ if (turn.test()) {
+ destroy();
+ }
+ }
+
+ template <typename... Args>
+ void construct(Args&&... args) noexcept {
+ static_assert(std::is_nothrow_constructible_v<U, Args&&...>,
+ "T must be nothrow constructible with Args&&...");
+ std::construct_at(reinterpret_cast<U*>(&storage), std::forward<Args>(args)...);
+ }
+
+ void destroy() noexcept {
+ static_assert(std::is_nothrow_destructible_v<U>, "T must be nothrow destructible");
+ std::destroy_at(reinterpret_cast<U*>(&storage));
+ }
+
+ U&& move() noexcept {
+ return reinterpret_cast<U&&>(storage);
+ }
+
+ // Align to avoid false sharing between adjacent slots
+ alignas(hardware_interference_size) std::atomic_flag turn{};
+ struct aligned_store {
+ struct type {
+ alignas(U) unsigned char data[sizeof(U)];
+ };
+ };
+ typename aligned_store::type storage;
+ };
+
template <typename... Args>
void emplace(Args&&... args) noexcept {
static_assert(std::is_nothrow_constructible_v<T, Args&&...>,
"T must be nothrow constructible with Args&&...");
auto const head = head_.fetch_add(1);
- auto& slot = slots_[idx(head)];
+ auto& slot = slots[idx(head)];
slot.turn.wait(true);
slot.construct(std::forward<Args>(args)...);
slot.turn.test_and_set();
@@ -150,31 +139,29 @@ private:
}
constexpr size_t idx(size_t i) const noexcept {
- return i & mask_;
+ return i & mask;
}
- std::conditional_t<true, std::condition_variable_any, std::condition_variable> cv;
- std::mutex cv_mutex;
- size_t mask_;
- Slot<T>* slots_;
- [[no_unique_address]] Allocator allocator_;
+ static constexpr size_t mask = capacity - 1;
// Align to avoid false sharing between head_ and tail_
alignas(hardware_interference_size) std::atomic<size_t> head_{0};
alignas(hardware_interference_size) std::atomic<size_t> tail_{0};
+ std::mutex cv_mutex;
+ std::condition_variable_any cv;
+
+ Slot<T>* slots;
+ [[no_unique_address]] std::allocator<Slot<T>> allocator;
+
static_assert(std::is_nothrow_copy_assignable_v<T> || std::is_nothrow_move_assignable_v<T>,
"T must be nothrow copy or move assignable");
static_assert(std::is_nothrow_destructible_v<T>, "T must be nothrow destructible");
};
-} // namespace mpsc
-
-template <typename T, typename Allocator = mpsc::AlignedAllocator<mpsc::Slot<T>>>
-using MPSCQueue = mpsc::Queue<T, Allocator>;
-
-} // namespace Common
#ifdef _MSC_VER
#pragma warning(pop)
#endif
+
+} // namespace Common
diff --git a/src/video_core/gpu_thread.h b/src/video_core/gpu_thread.h
index ad9fd5eff6..be0ac22140 100644
--- a/src/video_core/gpu_thread.h
+++ b/src/video_core/gpu_thread.h
@@ -98,7 +98,7 @@ struct CommandDataContainer {
struct SynchState final {
using CommandQueue = Common::MPSCQueue<CommandDataContainer>;
std::mutex write_lock;
- CommandQueue queue{512}; // size must be 2^n
+ CommandQueue queue;
u64 last_fence{};
std::atomic<u64> signaled_fence{};
std::condition_variable_any cv;