From 112351d557a41ed214eeef3a94ad0b7644466fbc Mon Sep 17 00:00:00 2001 From: MerryMage Date: Sat, 8 Sep 2018 14:28:39 +0100 Subject: [PATCH] common: Implement a ring buffer --- src/common/CMakeLists.txt | 1 + src/common/ring_buffer.h | 111 ++++++++++++++++++++++++++ src/tests/CMakeLists.txt | 1 + src/tests/common/ring_buffer.cpp | 130 +++++++++++++++++++++++++++++++ 4 files changed, 243 insertions(+) create mode 100644 src/common/ring_buffer.h create mode 100644 src/tests/common/ring_buffer.cpp diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt index f41946cc6..6a3f1fe08 100644 --- a/src/common/CMakeLists.txt +++ b/src/common/CMakeLists.txt @@ -71,6 +71,7 @@ add_library(common STATIC param_package.cpp param_package.h quaternion.h + ring_buffer.h scm_rev.cpp scm_rev.h scope_exit.h diff --git a/src/common/ring_buffer.h b/src/common/ring_buffer.h new file mode 100644 index 000000000..30d934a38 --- /dev/null +++ b/src/common/ring_buffer.h @@ -0,0 +1,111 @@ +// Copyright 2018 yuzu emulator team +// Licensed under GPLv2 or any later version +// Refer to the license.txt file included. + +#pragma once + +#include +#include +#include +#include +#include +#include +#include +#include "common/common_types.h" + +namespace Common { + +/// SPSC ring buffer +/// @tparam T Element type +/// @tparam capacity Number of slots in ring buffer +/// @tparam granularity Slot size in terms of number of elements +template +class RingBuffer { + /// A "slot" is made of `granularity` elements of `T`. + static constexpr size_t slot_size = granularity * sizeof(T); + // T must be safely memcpy-able and have a trivial default constructor. + static_assert(std::is_trivial_v); + // Ensure capacity is sensible. + static_assert(capacity < std::numeric_limits::max() / 2 / granularity); + static_assert((capacity & (capacity - 1)) == 0, "capacity must be a power of two"); + // Ensure lock-free. + static_assert(std::atomic::is_always_lock_free); + +public: + /// Pushes slots into the ring buffer + /// @param new_slots Pointer to the slots to push + /// @param slot_count Number of slots to push + /// @returns The number of slots actually pushed + size_t Push(const void* new_slots, size_t slot_count) { + const size_t write_index = m_write_index.load(); + const size_t slots_free = capacity + m_read_index.load() - write_index; + const size_t push_count = std::min(slot_count, slots_free); + + const size_t pos = write_index % capacity; + const size_t first_copy = std::min(capacity - pos, push_count); + const size_t second_copy = push_count - first_copy; + + const char* in = static_cast(new_slots); + std::memcpy(m_data.data() + pos * granularity, in, first_copy * slot_size); + in += first_copy * slot_size; + std::memcpy(m_data.data(), in, second_copy * slot_size); + + m_write_index.store(write_index + push_count); + + return push_count; + } + + size_t Push(const std::vector& input) { + return Push(input.data(), input.size()); + } + + /// Pops slots from the ring buffer + /// @param output Where to store the popped slots + /// @param max_slots Maximum number of slots to pop + /// @returns The number of slots actually popped + size_t Pop(void* output, size_t max_slots = ~size_t(0)) { + const size_t read_index = m_read_index.load(); + const size_t slots_filled = m_write_index.load() - read_index; + const size_t pop_count = std::min(slots_filled, max_slots); + + const size_t pos = read_index % capacity; + const size_t first_copy = std::min(capacity - pos, pop_count); + const size_t second_copy = pop_count - first_copy; + + char* out = static_cast(output); + std::memcpy(out, m_data.data() + pos * granularity, first_copy * slot_size); + out += first_copy * slot_size; + std::memcpy(out, m_data.data(), second_copy * slot_size); + + m_read_index.store(read_index + pop_count); + + return pop_count; + } + + std::vector Pop(size_t max_slots = ~size_t(0)) { + std::vector out(std::min(max_slots, capacity) * granularity); + const size_t count = Pop(out.data(), out.size() / granularity); + out.resize(count * granularity); + return out; + } + + /// @returns Number of slots used + size_t Size() const { + return m_write_index.load() - m_read_index.load(); + } + + /// @returns Maximum size of ring buffer + constexpr size_t Capacity() const { + return capacity; + } + +private: + // It is important to align the below variables for performance reasons: + // Having them on the same cache-line would result in false-sharing between them. + alignas(128) std::atomic m_read_index{0}; + alignas(128) std::atomic m_write_index{0}; + + std::array m_data; +}; + +} // namespace Common diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt index 4d74bb395..4e75a72ec 100644 --- a/src/tests/CMakeLists.txt +++ b/src/tests/CMakeLists.txt @@ -1,5 +1,6 @@ add_executable(tests common/param_package.cpp + common/ring_buffer.cpp core/arm/arm_test_common.cpp core/arm/arm_test_common.h core/core_timing.cpp diff --git a/src/tests/common/ring_buffer.cpp b/src/tests/common/ring_buffer.cpp new file mode 100644 index 000000000..f3fe57839 --- /dev/null +++ b/src/tests/common/ring_buffer.cpp @@ -0,0 +1,130 @@ +// Copyright 2018 yuzu emulator team +// Licensed under GPLv2 or any later version +// Refer to the license.txt file included. + +#include +#include +#include +#include +#include +#include +#include +#include "common/ring_buffer.h" + +namespace Common { + +TEST_CASE("RingBuffer: Basic Tests", "[common]") { + RingBuffer buf; + + // Pushing values into a ring buffer with space should succeed. + for (size_t i = 0; i < 4; i++) { + const char elem = static_cast(i); + const size_t count = buf.Push(&elem, 1); + REQUIRE(count == 1); + } + + REQUIRE(buf.Size() == 4); + + // Pushing values into a full ring buffer should fail. + { + const char elem = static_cast(42); + const size_t count = buf.Push(&elem, 1); + REQUIRE(count == 0); + } + + REQUIRE(buf.Size() == 4); + + // Popping multiple values from a ring buffer with values should succeed. + { + const std::vector popped = buf.Pop(2); + REQUIRE(popped.size() == 2); + REQUIRE(popped[0] == 0); + REQUIRE(popped[1] == 1); + } + + REQUIRE(buf.Size() == 2); + + // Popping a single value from a ring buffer with values should succeed. + { + const std::vector popped = buf.Pop(1); + REQUIRE(popped.size() == 1); + REQUIRE(popped[0] == 2); + } + + REQUIRE(buf.Size() == 1); + + // Pushing more values than space available should partially suceed. + { + std::vector to_push(6); + std::iota(to_push.begin(), to_push.end(), 88); + const size_t count = buf.Push(to_push); + REQUIRE(count == 3); + } + + REQUIRE(buf.Size() == 4); + + // Doing an unlimited pop should pop all values. + { + const std::vector popped = buf.Pop(); + REQUIRE(popped.size() == 4); + REQUIRE(popped[0] == 3); + REQUIRE(popped[1] == 88); + REQUIRE(popped[2] == 89); + REQUIRE(popped[3] == 90); + } + + REQUIRE(buf.Size() == 0); +} + +TEST_CASE("RingBuffer: Threaded Test", "[common]") { + RingBuffer buf; + const char seed = 42; + const size_t count = 1000000; + size_t full = 0; + size_t empty = 0; + + const auto next_value = [](std::array& value) { + value[0] += 1; + value[1] += 2; + }; + + std::thread producer{[&] { + std::array value = {seed, seed}; + size_t i = 0; + while (i < count) { + if (const size_t c = buf.Push(&value[0], 1); c > 0) { + REQUIRE(c == 1); + i++; + next_value(value); + } else { + full++; + std::this_thread::yield(); + } + } + }}; + + std::thread consumer{[&] { + std::array value = {seed, seed}; + size_t i = 0; + while (i < count) { + if (const std::vector v = buf.Pop(1); v.size() > 0) { + REQUIRE(v.size() == 2); + REQUIRE(v[0] == value[0]); + REQUIRE(v[1] == value[1]); + i++; + next_value(value); + } else { + empty++; + std::this_thread::yield(); + } + } + }}; + + producer.join(); + consumer.join(); + + REQUIRE(buf.Size() == 0); + printf("RingBuffer: Threaded Test: full: %zu, empty: %zu\n", full, empty); +} + +} // namespace Common