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243 lines
6.7 KiB
C++
243 lines
6.7 KiB
C++
template <typename T>
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struct MPSCNode {
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std::atomic<MPSCNode<T> *> next;
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T value;
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};
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//
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// Multiple Producer Single Consumer Lockless Queue
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// URL: https://www.1024cores.net
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//
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template <typename T>
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struct MPSCQueue {
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MPSCNode<T> sentinel;
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std::atomic<MPSCNode<T> *> head;
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std::atomic<MPSCNode<T> *> tail;
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std::atomic<isize> count;
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};
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template <typename T> gb_internal void mpsc_init (MPSCQueue<T> *q, gbAllocator const &allocator);
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template <typename T> gb_internal void mpsc_destroy(MPSCQueue<T> *q);
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template <typename T> gb_internal isize mpsc_enqueue(MPSCQueue<T> *q, T const &value);
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template <typename T> gb_internal bool mpsc_dequeue(MPSCQueue<T> *q, T *value_);
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template <typename T>
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gb_internal void mpsc_init(MPSCQueue<T> *q, gbAllocator const &allocator) {
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q->sentinel.next.store(nullptr, std::memory_order_relaxed);
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q->head.store(&q->sentinel, std::memory_order_relaxed);
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q->tail.store(&q->sentinel, std::memory_order_relaxed);
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q->count.store(0, std::memory_order_relaxed);
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}
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template <typename T>
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gb_internal void mpsc_destroy(MPSCQueue<T> *q) {
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GB_ASSERT(q->count.load() == 0);
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}
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template <typename T>
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gb_internal MPSCNode<T> *mpsc_alloc_node(MPSCQueue<T> *q, T const &value) {
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// auto new_node = gb_alloc_item(heap_allocator(), MPSCNode<T>);
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auto new_node = gb_alloc_item(permanent_allocator(), MPSCNode<T>);
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new_node->value = value;
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return new_node;
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}
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template <typename T>
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gb_internal void mpsc_free_node(MPSCQueue<T> *q, MPSCNode<T> *node) {
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// TODO(bill): determine a good way to handle the freed nodes rather than letting them leak
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}
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template <typename T>
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gb_internal isize mpsc_enqueue(MPSCQueue<T> *q, MPSCNode<T> *node) {
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node->next.store(nullptr, std::memory_order_relaxed);
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auto prev = q->head.exchange(node, std::memory_order_acq_rel);
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prev->next.store(node, std::memory_order_release);
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isize count = 1 + q->count.fetch_add(1, std::memory_order_relaxed);
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return count;
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}
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template <typename T>
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gb_internal isize mpsc_enqueue(MPSCQueue<T> *q, T const &value) {
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auto node = mpsc_alloc_node(q, value);
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return mpsc_enqueue(q, node);
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}
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template <typename T>
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gb_internal bool mpsc_dequeue(MPSCQueue<T> *q, T *value_) {
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auto tail = q->tail.load(std::memory_order_relaxed);
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auto next = tail->next.load(std::memory_order_relaxed);
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if (next) {
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q->tail.store(next, std::memory_order_relaxed);
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if (value_) *value_ = next->value;
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q->count.fetch_sub(1, std::memory_order_relaxed);
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mpsc_free_node(q, tail);
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return true;
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}
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GB_ASSERT(q->count.load(std::memory_order_acquire) == 0);
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return false;
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}
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////////////////////////////
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#define MPMC_CACHE_LINE_SIZE 64
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typedef std::atomic<i32> MPMCQueueAtomicIdx;
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// Multiple Producer Multiple Consumer Queue
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template <typename T>
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struct MPMCQueue {
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static size_t const PAD0_OFFSET = (sizeof(T *) + sizeof(MPMCQueueAtomicIdx *) + sizeof(gbAllocator) + sizeof(BlockingMutex) + sizeof(i32) + sizeof(i32));
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T * nodes;
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MPMCQueueAtomicIdx *indices;
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BlockingMutex mutex;
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MPMCQueueAtomicIdx count;
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i32 mask; // capacity-1, because capacity must be a power of 2
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char pad0[(MPMC_CACHE_LINE_SIZE*2 - PAD0_OFFSET) % MPMC_CACHE_LINE_SIZE];
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MPMCQueueAtomicIdx head_idx;
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char pad1[MPMC_CACHE_LINE_SIZE - sizeof(i32)];
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MPMCQueueAtomicIdx tail_idx;
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};
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gb_internal gbAllocator mpmc_allocator(void) {
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return heap_allocator();
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}
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gb_internal void mpmc_internal_init_indices(MPMCQueueAtomicIdx *indices, i32 offset, i32 size) {
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GB_ASSERT(offset % 8 == 0);
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GB_ASSERT(size % 8 == 0);
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// NOTE(bill): pretend it's not atomic for performance
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auto *raw_data = cast(i32 *)indices;
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for (i32 i = offset; i < size; i += 8) {
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raw_data[i+0] = i+0;
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raw_data[i+1] = i+1;
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raw_data[i+2] = i+2;
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raw_data[i+3] = i+3;
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raw_data[i+4] = i+4;
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raw_data[i+5] = i+5;
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raw_data[i+6] = i+6;
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raw_data[i+7] = i+7;
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}
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}
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template <typename T>
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gb_internal void mpmc_init(MPMCQueue<T> *q, isize size_i) {
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if (size_i < 8) {
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size_i = 8;
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}
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GB_ASSERT(size_i < I32_MAX);
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i32 size = cast(i32)size_i;
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size = next_pow2(size);
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GB_ASSERT(gb_is_power_of_two(size));
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q->mask = size-1;
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gbAllocator a = mpmc_allocator();
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q->nodes = gb_alloc_array(a, T, size);
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q->indices = gb_alloc_array(a, MPMCQueueAtomicIdx, size);
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mpmc_internal_init_indices(q->indices, 0, q->mask+1);
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}
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template <typename T>
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gb_internal void mpmc_destroy(MPMCQueue<T> *q) {
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gbAllocator a = mpmc_allocator();
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gb_free(a, q->nodes);
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gb_free(a, q->indices);
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}
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template <typename T>
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gb_internal bool mpmc_internal_grow(MPMCQueue<T> *q) {
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gbAllocator a = mpmc_allocator();
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mutex_lock(&q->mutex);
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i32 old_size = q->mask+1;
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i32 new_size = old_size*2;
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resize_array_raw(&q->nodes, a, old_size, new_size);
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if (q->nodes == nullptr) {
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GB_PANIC("Unable to resize enqueue: %td -> %td", old_size, new_size);
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mutex_unlock(&q->mutex);
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return false;
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}
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resize_array_raw(&q->indices, a, old_size, new_size);
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if (q->indices == nullptr) {
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GB_PANIC("Unable to resize enqueue: %td -> %td", old_size, new_size);
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mutex_unlock(&q->mutex);
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return false;
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}
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mpmc_internal_init_indices(q->indices, old_size, new_size);
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q->mask = new_size-1;
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mutex_unlock(&q->mutex);
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return true;
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}
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template <typename T>
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gb_internal i32 mpmc_enqueue(MPMCQueue<T> *q, T const &data) {
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GB_ASSERT(q->mask != 0);
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i32 head_idx = q->head_idx.load(std::memory_order_relaxed);
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for (;;) {
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i32 index = head_idx & q->mask;
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auto node = &q->nodes[index];
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auto node_idx_ptr = &q->indices[index];
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i32 node_idx = node_idx_ptr->load(std::memory_order_acquire);
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i32 diff = node_idx - head_idx;
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if (diff == 0) {
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i32 next_head_idx = head_idx+1;
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if (q->head_idx.compare_exchange_weak(head_idx, next_head_idx)) {
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*node = data;
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node_idx_ptr->store(next_head_idx, std::memory_order_release);
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return q->count.fetch_add(1, std::memory_order_release);
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}
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} else if (diff < 0) {
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if (!mpmc_internal_grow(q)) {
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return -1;
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}
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} else {
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head_idx = q->head_idx.load(std::memory_order_relaxed);
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}
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}
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}
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template <typename T>
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gb_internal bool mpmc_dequeue(MPMCQueue<T> *q, T *data_) {
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if (q->mask == 0) {
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return false;
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}
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i32 tail_idx = q->tail_idx.load(std::memory_order_relaxed);
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for (;;) {
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auto node_ptr = &q->nodes[tail_idx & q->mask];
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auto node_idx_ptr = &q->indices[tail_idx & q->mask];
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i32 node_idx = node_idx_ptr->load(std::memory_order_acquire);
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i32 diff = node_idx - (tail_idx+1);
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if (diff == 0) {
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i32 next_tail_idx = tail_idx+1;
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if (q->tail_idx.compare_exchange_weak(tail_idx, next_tail_idx)) {
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if (data_) *data_ = *node_ptr;
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node_idx_ptr->store(tail_idx + q->mask + 1, std::memory_order_release);
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q->count.fetch_sub(1, std::memory_order_release);
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return true;
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}
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} else if (diff < 0) {
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return false;
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} else {
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tail_idx = q->tail_idx.load(std::memory_order_relaxed);
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}
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}
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}
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