src/dawn/common/SlabAllocator.cpp - dawn - Git at Google

 // Copyright 2020 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.
 //
 // 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.
 //
 // 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
 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "dawn/common/SlabAllocator.h"

 #include <algorithm>
 #include <cstdlib>
 #include <limits>
 #include <new>
 #include "dawn/common/AlignedAlloc.h"
 #include "dawn/common/Assert.h"
 #include "dawn/common/Math.h"

 namespace dawn {

 // IndexLinkNode

 SlabAllocatorImpl::IndexLinkNode::IndexLinkNode(Index index, Index nextIndex)
     : index(index), nextIndex(nextIndex) {}

 // Slab

 SlabAllocatorImpl::Slab::Slab() = default;
 SlabAllocatorImpl::Slab::Slab(char allocation[], IndexLinkNode* head)
     : allocation(allocation), freeList(head) {}

 SlabAllocatorImpl::Slab::Slab(Slab&& rhs) = default;

 // SentinelSlab

 SlabAllocatorImpl::SentinelSlab::SentinelSlab() = default;
 SlabAllocatorImpl::SentinelSlab::SentinelSlab(SentinelSlab&& rhs) = default;

 SlabAllocatorImpl::SentinelSlab::~SentinelSlab() {
     // Delete the full linked list.
     while (next) {
         Slab* slab = next;
         slab->Splice();
         DAWN_ASSERT(slab->blocksInUse == 0);
         char* allocation = slab->allocation;
         slab->~Slab();  // Placement delete.
         AlignedFree(allocation);
     }
 }

 // SlabAllocatorImpl

 SlabAllocatorImpl::Index SlabAllocatorImpl::kInvalidIndex =
     std::numeric_limits<SlabAllocatorImpl::Index>::max();

 SlabAllocatorImpl::SlabAllocatorImpl(Index blocksPerSlab,
                                      uint32_t objectSize,
                                      uint32_t objectAlignment)
     : mAllocationAlignment(std::max(u32_alignof<Slab>, objectAlignment)),
       mSlabBlocksOffset(Align(u32_sizeof<Slab>, objectAlignment)),
       mIndexLinkNodeOffset(Align(objectSize, alignof(IndexLinkNode))),
       mBlockStride(Align(mIndexLinkNodeOffset + u32_sizeof<IndexLinkNode>, objectAlignment)),
       mBlocksPerSlab(blocksPerSlab),
       mTotalAllocationSize(static_cast<size_t>(mSlabBlocksOffset) + mBlocksPerSlab * mBlockStride) {
     DAWN_ASSERT(IsPowerOfTwo(mAllocationAlignment));
 }

 SlabAllocatorImpl::SlabAllocatorImpl(SlabAllocatorImpl&& rhs)
     : mAllocationAlignment(rhs.mAllocationAlignment),
       mSlabBlocksOffset(rhs.mSlabBlocksOffset),
       mIndexLinkNodeOffset(rhs.mIndexLinkNodeOffset),
       mBlockStride(rhs.mBlockStride),
       mBlocksPerSlab(rhs.mBlocksPerSlab),
       mTotalAllocationSize(rhs.mTotalAllocationSize),
       mAvailableSlabs(std::move(rhs.mAvailableSlabs)),
       mFullSlabs(std::move(rhs.mFullSlabs)),
       mRecycledSlabs(std::move(rhs.mRecycledSlabs)) {}

 SlabAllocatorImpl::~SlabAllocatorImpl() = default;

 SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::OffsetFrom(
     IndexLinkNode* node,
     std::make_signed_t<Index> offset) const {
     return reinterpret_cast<IndexLinkNode*>(reinterpret_cast<char*>(node) +
                                             static_cast<intptr_t>(mBlockStride) * offset);
 }

 SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::NodeFromObject(void* object) const {
     return reinterpret_cast<SlabAllocatorImpl::IndexLinkNode*>(static_cast<char*>(object) +
                                                                mIndexLinkNodeOffset);
 }

 void* SlabAllocatorImpl::ObjectFromNode(IndexLinkNode* node) const {
     return static_cast<void*>(reinterpret_cast<char*>(node) - mIndexLinkNodeOffset);
 }

 bool SlabAllocatorImpl::IsNodeInSlab(Slab* slab, IndexLinkNode* node) const {
     char* firstObjectPtr = reinterpret_cast<char*>(slab) + mSlabBlocksOffset;
     IndexLinkNode* firstNode = NodeFromObject(firstObjectPtr);
     IndexLinkNode* lastNode = OffsetFrom(firstNode, mBlocksPerSlab - 1);
     return node >= firstNode && node <= lastNode && node->index < mBlocksPerSlab;
 }

 void SlabAllocatorImpl::PushFront(Slab* slab, IndexLinkNode* node) const {
     DAWN_ASSERT(IsNodeInSlab(slab, node));

     IndexLinkNode* head = slab->freeList;
     if (head == nullptr) {
         node->nextIndex = kInvalidIndex;
     } else {
         DAWN_ASSERT(IsNodeInSlab(slab, head));
         node->nextIndex = head->index;
     }
     slab->freeList = node;

     DAWN_ASSERT(slab->blocksInUse != 0);
     slab->blocksInUse--;
 }

 SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::PopFront(Slab* slab) const {
     DAWN_ASSERT(slab->freeList != nullptr);

     IndexLinkNode* head = slab->freeList;
     if (head->nextIndex == kInvalidIndex) {
         slab->freeList = nullptr;
     } else {
         DAWN_ASSERT(IsNodeInSlab(slab, head));
         slab->freeList = OffsetFrom(head, head->nextIndex - head->index);
         DAWN_ASSERT(IsNodeInSlab(slab, slab->freeList));
     }

     DAWN_ASSERT(slab->blocksInUse < mBlocksPerSlab);
     slab->blocksInUse++;
     return head;
 }

 void SlabAllocatorImpl::SentinelSlab::Prepend(SlabAllocatorImpl::Slab* slab) {
     if (next != nullptr) {
         next->prev = slab;
     }
     slab->prev = this;
     slab->next = next;
     next = slab;
 }

 void SlabAllocatorImpl::Slab::Splice() {
     DAWN_ASSERT(prev != nullptr);
     prev->next = next;
     if (next != nullptr) {
         next->prev = prev;
     }
     prev = nullptr;
     next = nullptr;
 }

 void* SlabAllocatorImpl::Allocate() {
     if (mAvailableSlabs.next == nullptr) {
         GetNewSlab();
     }

     Slab* slab = mAvailableSlabs.next;
     IndexLinkNode* node = PopFront(slab);
     DAWN_ASSERT(node != nullptr);

     // Move full slabs to a separate list, so allocate can always return quickly.
     if (slab->blocksInUse == mBlocksPerSlab) {
         slab->Splice();
         mFullSlabs.Prepend(slab);
     }

     return ObjectFromNode(node);
 }

 void SlabAllocatorImpl::Deallocate(void* ptr) {
     IndexLinkNode* node = NodeFromObject(ptr);

     DAWN_ASSERT(node->index < mBlocksPerSlab);
     void* firstAllocation = ObjectFromNode(OffsetFrom(node, -node->index));
     Slab* slab = reinterpret_cast<Slab*>(static_cast<char*>(firstAllocation) - mSlabBlocksOffset);
     DAWN_ASSERT(slab != nullptr);

     bool slabWasFull = slab->blocksInUse == mBlocksPerSlab;
     DAWN_ASSERT(slab->blocksInUse != 0);
     PushFront(slab, node);

     if (slabWasFull) {
         // Slab is in the full list. Move it to the recycled list.
         DAWN_ASSERT(slab->freeList != nullptr);
         slab->Splice();
         mRecycledSlabs.Prepend(slab);
     }

     // TODO(crbug.com/dawn/825): Occasionally prune slabs if |blocksInUse == 0|.
     // Doing so eagerly hurts performance.
 }

 void SlabAllocatorImpl::GetNewSlab() {
     // Should only be called when there are no available slabs.
     DAWN_ASSERT(mAvailableSlabs.next == nullptr);

     if (mRecycledSlabs.next != nullptr) {
         // If the recycled list is non-empty, swap their contents.
         std::swap(mAvailableSlabs.next, mRecycledSlabs.next);

         // We swapped the next pointers, so the prev pointer is wrong.
         // Update it here.
         mAvailableSlabs.next->prev = &mAvailableSlabs;
         DAWN_ASSERT(mRecycledSlabs.next == nullptr);
         return;
     }

     char* alignedPtr = static_cast<char*>(AlignedAlloc(mTotalAllocationSize, mAllocationAlignment));

     char* dataStart = alignedPtr + mSlabBlocksOffset;

     IndexLinkNode* node = NodeFromObject(dataStart);
     for (uint32_t i = 0; i < mBlocksPerSlab; ++i) {
         new (OffsetFrom(node, i)) IndexLinkNode(i, i + 1);
     }

     IndexLinkNode* lastNode = OffsetFrom(node, mBlocksPerSlab - 1);
     lastNode->nextIndex = kInvalidIndex;

     mAvailableSlabs.Prepend(new (alignedPtr) Slab(alignedPtr, node));
 }

 }  // namespace dawn
	// Copyright 2020 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.
	//
	// 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.
	//
	// 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
	// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
	// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include "dawn/common/SlabAllocator.h"

	#include <algorithm>
	#include <cstdlib>
	#include <limits>
	#include <new>
	#include "dawn/common/AlignedAlloc.h"
	#include "dawn/common/Assert.h"
	#include "dawn/common/Math.h"

	namespace dawn {

	// IndexLinkNode

	SlabAllocatorImpl::IndexLinkNode::IndexLinkNode(Index index, Index nextIndex)
	: index(index), nextIndex(nextIndex) {}

	// Slab

	SlabAllocatorImpl::Slab::Slab() = default;
	SlabAllocatorImpl::Slab::Slab(char allocation[], IndexLinkNode* head)
	: allocation(allocation), freeList(head) {}

	SlabAllocatorImpl::Slab::Slab(Slab&& rhs) = default;

	// SentinelSlab

	SlabAllocatorImpl::SentinelSlab::SentinelSlab() = default;
	SlabAllocatorImpl::SentinelSlab::SentinelSlab(SentinelSlab&& rhs) = default;

	SlabAllocatorImpl::SentinelSlab::~SentinelSlab() {
	// Delete the full linked list.
	while (next) {
	Slab* slab = next;
	slab->Splice();
	DAWN_ASSERT(slab->blocksInUse == 0);
	char* allocation = slab->allocation;
	slab->~Slab(); // Placement delete.
	AlignedFree(allocation);
	}
	}

	// SlabAllocatorImpl

	SlabAllocatorImpl::Index SlabAllocatorImpl::kInvalidIndex =
	std::numeric_limits<SlabAllocatorImpl::Index>::max();

	SlabAllocatorImpl::SlabAllocatorImpl(Index blocksPerSlab,
	uint32_t objectSize,
	uint32_t objectAlignment)
	: mAllocationAlignment(std::max(u32_alignof<Slab>, objectAlignment)),
	mSlabBlocksOffset(Align(u32_sizeof<Slab>, objectAlignment)),
	mIndexLinkNodeOffset(Align(objectSize, alignof(IndexLinkNode))),
	mBlockStride(Align(mIndexLinkNodeOffset + u32_sizeof<IndexLinkNode>, objectAlignment)),
	mBlocksPerSlab(blocksPerSlab),
	mTotalAllocationSize(static_cast<size_t>(mSlabBlocksOffset) + mBlocksPerSlab * mBlockStride) {
	DAWN_ASSERT(IsPowerOfTwo(mAllocationAlignment));
	}

	SlabAllocatorImpl::SlabAllocatorImpl(SlabAllocatorImpl&& rhs)
	: mAllocationAlignment(rhs.mAllocationAlignment),
	mSlabBlocksOffset(rhs.mSlabBlocksOffset),
	mIndexLinkNodeOffset(rhs.mIndexLinkNodeOffset),
	mBlockStride(rhs.mBlockStride),
	mBlocksPerSlab(rhs.mBlocksPerSlab),
	mTotalAllocationSize(rhs.mTotalAllocationSize),
	mAvailableSlabs(std::move(rhs.mAvailableSlabs)),
	mFullSlabs(std::move(rhs.mFullSlabs)),
	mRecycledSlabs(std::move(rhs.mRecycledSlabs)) {}

	SlabAllocatorImpl::~SlabAllocatorImpl() = default;

	SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::OffsetFrom(
	IndexLinkNode* node,
	std::make_signed_t<Index> offset) const {
	return reinterpret_cast<IndexLinkNode>(reinterpret_cast<char>(node) +
	static_cast<intptr_t>(mBlockStride) * offset);
	}

	SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::NodeFromObject(void* object) const {
	return reinterpret_cast<SlabAllocatorImpl::IndexLinkNode>(static_cast<char>(object) +
	mIndexLinkNodeOffset);
	}

	void* SlabAllocatorImpl::ObjectFromNode(IndexLinkNode* node) const {
	return static_cast<void>(reinterpret_cast<char>(node) - mIndexLinkNodeOffset);
	}

	bool SlabAllocatorImpl::IsNodeInSlab(Slab* slab, IndexLinkNode* node) const {
	char* firstObjectPtr = reinterpret_cast<char*>(slab) + mSlabBlocksOffset;
	IndexLinkNode* firstNode = NodeFromObject(firstObjectPtr);
	IndexLinkNode* lastNode = OffsetFrom(firstNode, mBlocksPerSlab - 1);
	return node >= firstNode && node <= lastNode && node->index < mBlocksPerSlab;
	}

	void SlabAllocatorImpl::PushFront(Slab* slab, IndexLinkNode* node) const {
	DAWN_ASSERT(IsNodeInSlab(slab, node));

	IndexLinkNode* head = slab->freeList;
	if (head == nullptr) {
	node->nextIndex = kInvalidIndex;
	} else {
	DAWN_ASSERT(IsNodeInSlab(slab, head));
	node->nextIndex = head->index;
	}
	slab->freeList = node;

	DAWN_ASSERT(slab->blocksInUse != 0);
	slab->blocksInUse--;
	}

	SlabAllocatorImpl::IndexLinkNode* SlabAllocatorImpl::PopFront(Slab* slab) const {
	DAWN_ASSERT(slab->freeList != nullptr);

	IndexLinkNode* head = slab->freeList;
	if (head->nextIndex == kInvalidIndex) {
	slab->freeList = nullptr;
	} else {
	DAWN_ASSERT(IsNodeInSlab(slab, head));
	slab->freeList = OffsetFrom(head, head->nextIndex - head->index);
	DAWN_ASSERT(IsNodeInSlab(slab, slab->freeList));
	}

	DAWN_ASSERT(slab->blocksInUse < mBlocksPerSlab);
	slab->blocksInUse++;
	return head;
	}

	void SlabAllocatorImpl::SentinelSlab::Prepend(SlabAllocatorImpl::Slab* slab) {
	if (next != nullptr) {
	next->prev = slab;
	}
	slab->prev = this;
	slab->next = next;
	next = slab;
	}

	void SlabAllocatorImpl::Slab::Splice() {
	DAWN_ASSERT(prev != nullptr);
	prev->next = next;
	if (next != nullptr) {
	next->prev = prev;
	}
	prev = nullptr;
	next = nullptr;
	}

	void* SlabAllocatorImpl::Allocate() {
	if (mAvailableSlabs.next == nullptr) {
	GetNewSlab();
	}

	Slab* slab = mAvailableSlabs.next;
	IndexLinkNode* node = PopFront(slab);
	DAWN_ASSERT(node != nullptr);

	// Move full slabs to a separate list, so allocate can always return quickly.
	if (slab->blocksInUse == mBlocksPerSlab) {
	slab->Splice();
	mFullSlabs.Prepend(slab);
	}

	return ObjectFromNode(node);
	}

	void SlabAllocatorImpl::Deallocate(void* ptr) {
	IndexLinkNode* node = NodeFromObject(ptr);

	DAWN_ASSERT(node->index < mBlocksPerSlab);
	void* firstAllocation = ObjectFromNode(OffsetFrom(node, -node->index));
	Slab* slab = reinterpret_cast<Slab>(static_cast<char>(firstAllocation) - mSlabBlocksOffset);
	DAWN_ASSERT(slab != nullptr);

	bool slabWasFull = slab->blocksInUse == mBlocksPerSlab;
	DAWN_ASSERT(slab->blocksInUse != 0);
	PushFront(slab, node);

	if (slabWasFull) {
	// Slab is in the full list. Move it to the recycled list.
	DAWN_ASSERT(slab->freeList != nullptr);
	slab->Splice();
	mRecycledSlabs.Prepend(slab);
	}

	// TODO(crbug.com/dawn/825): Occasionally prune slabs if \|blocksInUse == 0\|.
	// Doing so eagerly hurts performance.
	}

	void SlabAllocatorImpl::GetNewSlab() {
	// Should only be called when there are no available slabs.
	DAWN_ASSERT(mAvailableSlabs.next == nullptr);

	if (mRecycledSlabs.next != nullptr) {
	// If the recycled list is non-empty, swap their contents.
	std::swap(mAvailableSlabs.next, mRecycledSlabs.next);

	// We swapped the next pointers, so the prev pointer is wrong.
	// Update it here.
	mAvailableSlabs.next->prev = &mAvailableSlabs;
	DAWN_ASSERT(mRecycledSlabs.next == nullptr);
	return;
	}

	char* alignedPtr = static_cast<char*>(AlignedAlloc(mTotalAllocationSize, mAllocationAlignment));

	char* dataStart = alignedPtr + mSlabBlocksOffset;

	IndexLinkNode* node = NodeFromObject(dataStart);
	for (uint32_t i = 0; i < mBlocksPerSlab; ++i) {
	new (OffsetFrom(node, i)) IndexLinkNode(i, i + 1);
	}

	IndexLinkNode* lastNode = OffsetFrom(node, mBlocksPerSlab - 1);
	lastNode->nextIndex = kInvalidIndex;

	mAvailableSlabs.Prepend(new (alignedPtr) Slab(alignedPtr, node));
	}

	} // namespace dawn