b6c0211d6a
- 添加完整的中文Doxygen注释文档 - 实现process_deferred_release()延迟释放处理 - 添加deferred_release模板函数和current_frame_index() - 实现延迟释放队列和帧索引管理 - 详细说明FreeList栈式索引分配/释放算法 - 更新D3D12学习Wiki，添加延迟释放机制章节
137 lines
4.5 KiB
C++
137 lines
4.5 KiB
C++
#include "D3D12Resources.h"
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#include "D3D12Core.h"
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namespace XEngine::graphics::d3d12::core{
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//////////// DESCRIPTOR HEAP ////////////
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// 该类将被多个线程并发访问：资源创建（如纹理）与资源销毁/释放可能发生在不同线程，
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// 因此需要同步机制保护内部数据结构
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bool
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descriptor_heap::initialize(u32 capacity, bool is_shader_visible)
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{
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std::lock_guard lock(_mutex);
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// 检查容量有效性：必须大于0且不超过最大限制
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assert(capacity && capacity <= D3D12_MAX_SHADER_VISIBLE_DESCRIPTOR_HEAP_SIZE_TIER_2);
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// 对于采样器描述符堆，需要额外检查容量是否超过最大采样器堆大小限制
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assert(!(_type == D3D12_DESCRIPTOR_HEAP_TYPE_SAMPLER &&
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capacity > D3D12_MAX_SHADER_VISIBLE_SAMPLER_HEAP_SIZE));
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// 对于DSV和RTV他们在描述符堆的内存模型中本身就是GPU不可见的
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if(_type == D3D12_DESCRIPTOR_HEAP_TYPE_DSV ||
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_type == D3D12_DESCRIPTOR_HEAP_TYPE_RTV)
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{
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is_shader_visible = false;
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}
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// 应为这个功能将被调用多次,所以需要先释放之前的资源
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release();
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ID3D12Device *const device {core::device()};
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assert(device);
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D3D12_DESCRIPTOR_HEAP_DESC desc{};
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desc.Flags = is_shader_visible
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? D3D12_DESCRIPTOR_HEAP_FLAG_SHADER_VISIBLE
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: D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
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desc.NumDescriptors = capacity;
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desc.Type = _type;
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desc.NodeMask = 0;
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HRESULT hr {S_OK};
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DXCall(hr = device->CreateDescriptorHeap(&desc, IID_PPV_ARGS(&_heap)));
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if(FAILED(hr)) return false;
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_free_handles = std::move(std::make_unique<u32[]>(capacity));
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_capacity = capacity;
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_size = 0;
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for(u32 i = 0; i < capacity; ++i) _free_handles[i] = i;
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DEBUG_OP(for(u32 i{0}; i<frame_buffer_count;++i) assert(_deferred_free_indices[i].empty()));
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_descriptor_size = device->GetDescriptorHandleIncrementSize(_type);
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_cpu_start = _heap->GetCPUDescriptorHandleForHeapStart();
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_gpu_start = is_shader_visible
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? _heap->GetGPUDescriptorHandleForHeapStart()
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: D3D12_GPU_DESCRIPTOR_HANDLE{0};
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return true;
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}
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void
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descriptor_heap::release()
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{
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assert(!_size);
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core::deferred_release(_heap);
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}
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// 处理延迟释放
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// 注意这里的free_handles对应的是一整块连续的内存,而不是对应的描述符句柄的索引index
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// 描述符自生是记录了自己的地址(通过简单的计算可以得出偏移和索引)
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// 所以释放后,只需要指向释放出来的索引index即可,这样下次新增时即可以
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// 放在对应的空闲区域.
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// 这一切都是应为freelist和内存是一对一对应的关系
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// 延迟释放机制确保GPU完成使用后才回收描述符，避免GPU仍在访问时重用
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// 使用双缓冲/多帧缓冲机制，当前帧释放的描述符会在若干帧后安全回收
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// _free_handles作为空闲索引栈，_size指向栈顶，回收的索引压入栈中供后续分配使用
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void
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descriptor_heap::process_deferred_release(u32 frame_index)
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{
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std::lock_guard lock(_mutex);
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assert(frame_index < frame_buffer_count);
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utl::vector<u32>& indices { _deferred_free_indices[frame_index] };
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if(!indices.empty())
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{
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for(auto index : indices)
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{
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--_size;
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_free_handles[_size] = index;
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}
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indices.clear();
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}
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}
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descriptor_handle
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descriptor_heap::allocate()
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{
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std::lock_guard lock(_mutex);
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assert(_heap);
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assert(_size < _capacity);
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const u32 index { _free_handles[_size] };
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const u32 offset { index * _descriptor_size };
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++_size;
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descriptor_handle handle{};
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handle.cpu.ptr = _cpu_start.ptr + offset;
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if(is_shader_visible())
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{
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handle.gpu.ptr = _gpu_start.ptr + offset;
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}
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DEBUG_OP(handle.container = this);
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DEBUG_OP(handle.index = index);
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return handle;
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}
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void
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descriptor_heap::free(descriptor_handle handle)
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{
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if(!handle.is_valid()) return;
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std::lock_guard lock(_mutex);
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assert(_heap && _size);
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assert(handle.container == this);
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assert(handle.cpu.ptr >= _cpu_start.ptr);
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assert((handle.cpu.ptr - _cpu_start.ptr) % _descriptor_size == 0);
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assert(handle.index < _capacity);
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const u32 index{ (u32)(handle.cpu.ptr - _cpu_start.ptr) / _descriptor_size };
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assert(handle.index == index);
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const u32 frame_index{ core::current_frame_index() };
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_deferred_free_indices[frame_index].push_back(index);
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core::set_deferred_release_flag();
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handle = {};
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}
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} //XEngine::graphics::d3d12
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