src/dawn/native/DynamicUploader.cpp

// Copyright 2018 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
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// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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#include "dawn/native/DynamicUploader.h"

#include <utility>

#include "dawn/common/Math.h"
#include "dawn/native/Buffer.h"
#include "dawn/native/Device.h"
#include "dawn/native/Queue.h"

namespace dawn::native {

DynamicUploader::DynamicUploader(DeviceBase* device) : mDevice(device) {
    mRingBuffers.emplace_back(
        std::unique_ptr<RingBuffer>(new RingBuffer{nullptr, RingBufferAllocator(kRingBufferSize)}));
}

void DynamicUploader::ReleaseStagingBuffer(Ref<BufferBase> stagingBuffer) {
    mReleasedStagingBuffers.Enqueue(std::move(stagingBuffer),
                                    mDevice->GetQueue()->GetPendingCommandSerial());
}

ResultOrError<UploadHandle> DynamicUploader::AllocateInternal(uint64_t allocationSize,
                                                              ExecutionSerial serial,
                                                              uint64_t offsetAlignment) {
    // Disable further sub-allocation should the request be too large.
    if (allocationSize > kRingBufferSize) {
        BufferDescriptor bufferDesc = {};
        bufferDesc.usage = wgpu::BufferUsage::CopySrc | wgpu::BufferUsage::MapWrite;
        bufferDesc.size = Align(allocationSize, 4);
        bufferDesc.mappedAtCreation = true;
        bufferDesc.label = "Dawn_DynamicUploaderStaging";

        IgnoreLazyClearCountScope scope(mDevice);
        Ref<BufferBase> stagingBuffer;
        DAWN_TRY_ASSIGN(stagingBuffer, mDevice->CreateBuffer(&bufferDesc));

        UploadHandle uploadHandle;
        uploadHandle.mappedBuffer = static_cast<uint8_t*>(stagingBuffer->GetMappedPointer());
        uploadHandle.stagingBuffer = stagingBuffer.Get();

        ReleaseStagingBuffer(std::move(stagingBuffer));
        return uploadHandle;
    }

    // Note: Validation ensures size is already aligned.
    // First-fit: find next buffer large enough to satisfy the allocation request.
    uint64_t startOffset = RingBufferAllocator::kInvalidOffset;
    RingBuffer* targetRingBuffer = mRingBuffers.back().get();
    for (auto& ringBuffer : mRingBuffers) {
        RingBufferAllocator& ringBufferAllocator = ringBuffer->mAllocator;
        // Prevent overflow.
        DAWN_ASSERT(ringBufferAllocator.GetSize() >= ringBufferAllocator.GetUsedSize());
        startOffset = ringBufferAllocator.Allocate(allocationSize, serial, offsetAlignment);
        if (startOffset != RingBufferAllocator::kInvalidOffset) {
            targetRingBuffer = ringBuffer.get();
            break;
        }
    }

    // Upon failure, append a newly created ring buffer to fulfill the
    // request.
    if (startOffset == RingBufferAllocator::kInvalidOffset) {
        mRingBuffers.emplace_back(std::unique_ptr<RingBuffer>(
            new RingBuffer{nullptr, RingBufferAllocator(kRingBufferSize)}));

        targetRingBuffer = mRingBuffers.back().get();
        startOffset = targetRingBuffer->mAllocator.Allocate(allocationSize, serial);
    }

    DAWN_ASSERT(startOffset != RingBufferAllocator::kInvalidOffset);

    // Allocate the staging buffer backing the ringbuffer.
    // Note: the first ringbuffer will be lazily created.
    if (targetRingBuffer->mStagingBuffer == nullptr) {
        BufferDescriptor bufferDesc = {};
        bufferDesc.usage = wgpu::BufferUsage::CopySrc | wgpu::BufferUsage::MapWrite;
        bufferDesc.size = Align(targetRingBuffer->mAllocator.GetSize(), 4);
        bufferDesc.mappedAtCreation = true;
        bufferDesc.label = "Dawn_DynamicUploaderStaging";

        IgnoreLazyClearCountScope scope(mDevice);
        Ref<BufferBase> stagingBuffer;
        DAWN_TRY_ASSIGN(stagingBuffer, mDevice->CreateBuffer(&bufferDesc));
        targetRingBuffer->mStagingBuffer = std::move(stagingBuffer);
    }

    DAWN_ASSERT(targetRingBuffer->mStagingBuffer != nullptr);

    UploadHandle uploadHandle;
    uploadHandle.stagingBuffer = targetRingBuffer->mStagingBuffer.Get();
    uploadHandle.mappedBuffer =
        static_cast<uint8_t*>(uploadHandle.stagingBuffer->GetMappedPointer()) + startOffset;
    uploadHandle.startOffset = startOffset;

    return uploadHandle;
}

void DynamicUploader::Deallocate(ExecutionSerial lastCompletedSerial) {
    // Reclaim memory within the ring buffers by ticking (or removing requests no longer
    // in-flight).
    for (size_t i = 0; i < mRingBuffers.size(); ++i) {
        mRingBuffers[i]->mAllocator.Deallocate(lastCompletedSerial);

        // Never erase the last buffer as to prevent re-creating smaller buffers
        // again. The last buffer is the largest.
        if (mRingBuffers[i]->mAllocator.Empty() && i < mRingBuffers.size() - 1) {
            mRingBuffers.erase(mRingBuffers.begin() + i);
        }
    }
    mReleasedStagingBuffers.ClearUpTo(lastCompletedSerial);
}

ResultOrError<UploadHandle> DynamicUploader::Allocate(uint64_t allocationSize,
                                                      ExecutionSerial serial,
                                                      uint64_t offsetAlignment) {
    DAWN_ASSERT(offsetAlignment > 0);
    return AllocateInternal(allocationSize, serial, offsetAlignment);
}

bool DynamicUploader::ShouldFlush() {
    uint64_t kTotalAllocatedSizeThreshold = 64 * 1024 * 1024;
    // We use total allocated size instead of pending-upload size to prevent Dawn from allocating
    // too much GPU memory so that the risk of OOM can be minimized.
    return GetTotalAllocatedSize() > kTotalAllocatedSizeThreshold;
}

uint64_t DynamicUploader::GetTotalAllocatedSize() {
    uint64_t size = 0;
    for (const auto& buffer : mReleasedStagingBuffers.IterateAll()) {
        size += buffer->GetSize();
    }
    for (const auto& buffer : mRingBuffers) {
        if (buffer->mStagingBuffer != nullptr) {
            size += buffer->mStagingBuffer->GetSize();
        }
    }
    return size;
}

}  // namespace dawn::native