| /* |
| * Copyright 2020 Google LLC |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/base/SkBlockAllocator.h" |
| |
| #include "include/private/base/SkDebug.h" |
| #include "include/private/base/SkTo.h" |
| |
| #ifdef SK_DEBUG |
| #include <vector> |
| #endif |
| |
| SkBlockAllocator::SkBlockAllocator(GrowthPolicy policy, size_t blockIncrementBytes, |
| size_t additionalPreallocBytes) |
| : fTail(&fHead) |
| // Round up to the nearest max-aligned value, and then divide so that fBlockSizeIncrement |
| // can effectively fit higher byte counts in its 16 bits of storage |
| , fBlockIncrement(SkTo<uint16_t>( |
| std::min(SkAlignTo(blockIncrementBytes, kAddressAlign) / kAddressAlign, |
| (size_t) std::numeric_limits<uint16_t>::max()))) |
| , fGrowthPolicy(static_cast<uint64_t>(policy)) |
| , fN0((policy == GrowthPolicy::kLinear || policy == GrowthPolicy::kExponential) ? 1 : 0) |
| , fN1(1) |
| // The head block always fills remaining space from SkBlockAllocator's size, because it's |
| // inline, but can take over the specified number of bytes immediately after it. |
| , fHead(/*prev=*/nullptr, additionalPreallocBytes + BaseHeadBlockSize()) { |
| SkASSERT(fBlockIncrement >= 1); |
| SkASSERT(additionalPreallocBytes <= kMaxAllocationSize); |
| } |
| |
| SkBlockAllocator::Block::Block(Block* prev, int allocationSize) |
| : fNext(nullptr) |
| , fPrev(prev) |
| , fSize(allocationSize) |
| , fCursor(kDataStart) |
| , fMetadata(0) |
| , fAllocatorMetadata(0) { |
| SkASSERT(allocationSize >= (int) sizeof(Block)); |
| SkDEBUGCODE(fSentinel = kAssignedMarker;) |
| |
| this->poisonRange(kDataStart, fSize); |
| } |
| |
| SkBlockAllocator::Block::~Block() { |
| this->unpoisonRange(kDataStart, fSize); |
| |
| SkASSERT(fSentinel == kAssignedMarker); |
| SkDEBUGCODE(fSentinel = kFreedMarker;) // FWIW |
| } |
| |
| size_t SkBlockAllocator::totalSize() const { |
| // Use size_t since the sum across all blocks could exceed 'int', even though each block won't |
| size_t size = offsetof(SkBlockAllocator, fHead) + this->scratchBlockSize(); |
| for (const Block* b : this->blocks()) { |
| size += b->fSize; |
| } |
| SkASSERT(size >= this->preallocSize()); |
| return size; |
| } |
| |
| size_t SkBlockAllocator::totalUsableSpace() const { |
| size_t size = this->scratchBlockSize(); |
| if (size > 0) { |
| size -= kDataStart; // scratchBlockSize reports total block size, not usable size |
| } |
| for (const Block* b : this->blocks()) { |
| size += (b->fSize - kDataStart); |
| } |
| SkASSERT(size >= this->preallocUsableSpace()); |
| return size; |
| } |
| |
| size_t SkBlockAllocator::totalSpaceInUse() const { |
| size_t size = 0; |
| for (const Block* b : this->blocks()) { |
| size += (b->fCursor - kDataStart); |
| } |
| SkASSERT(size <= this->totalUsableSpace()); |
| return size; |
| } |
| |
| SkBlockAllocator::Block* SkBlockAllocator::findOwningBlock(const void* p) { |
| // When in doubt, search in reverse to find an overlapping block. |
| uintptr_t ptr = reinterpret_cast<uintptr_t>(p); |
| for (Block* b : this->rblocks()) { |
| uintptr_t lowerBound = reinterpret_cast<uintptr_t>(b) + kDataStart; |
| uintptr_t upperBound = reinterpret_cast<uintptr_t>(b) + b->fSize; |
| if (lowerBound <= ptr && ptr < upperBound) { |
| SkASSERT(b->fSentinel == kAssignedMarker); |
| return b; |
| } |
| } |
| return nullptr; |
| } |
| |
| void SkBlockAllocator::releaseBlock(Block* block) { |
| if (block == &fHead) { |
| // Reset the cursor of the head block so that it can be reused if it becomes the new tail |
| block->fCursor = kDataStart; |
| block->fMetadata = 0; |
| block->poisonRange(kDataStart, block->fSize); |
| // Unlike in reset(), we don't set the head's next block to null because there are |
| // potentially heap-allocated blocks that are still connected to it. |
| } else { |
| SkASSERT(block->fPrev); |
| block->fPrev->fNext = block->fNext; |
| if (block->fNext) { |
| SkASSERT(fTail != block); |
| block->fNext->fPrev = block->fPrev; |
| } else { |
| SkASSERT(fTail == block); |
| fTail = block->fPrev; |
| } |
| |
| // The released block becomes the new scratch block (if it's bigger), or delete it |
| if (this->scratchBlockSize() < block->fSize) { |
| SkASSERT(block != fHead.fPrev); // shouldn't already be the scratch block |
| if (fHead.fPrev) { |
| delete fHead.fPrev; |
| } |
| block->markAsScratch(); |
| fHead.fPrev = block; |
| } else { |
| delete block; |
| } |
| } |
| |
| // Decrement growth policy (opposite of addBlock()'s increment operations) |
| GrowthPolicy gp = static_cast<GrowthPolicy>(fGrowthPolicy); |
| if (fN0 > 0 && (fN1 > 1 || gp == GrowthPolicy::kFibonacci)) { |
| SkASSERT(gp != GrowthPolicy::kFixed); // fixed never needs undoing, fN0 always is 0 |
| if (gp == GrowthPolicy::kLinear) { |
| fN1 = fN1 - fN0; |
| } else if (gp == GrowthPolicy::kFibonacci) { |
| // Subtract n0 from n1 to get the prior 2 terms in the fibonacci sequence |
| int temp = fN1 - fN0; // yields prior fN0 |
| fN1 = fN1 - temp; // yields prior fN1 |
| fN0 = temp; |
| } else { |
| SkASSERT(gp == GrowthPolicy::kExponential); |
| // Divide by 2 to undo the 2N update from addBlock |
| fN1 = fN1 >> 1; |
| fN0 = fN1; |
| } |
| } |
| |
| SkASSERT(fN1 >= 1 && fN0 >= 0); |
| } |
| |
| void SkBlockAllocator::stealHeapBlocks(SkBlockAllocator* other) { |
| Block* toSteal = other->fHead.fNext; |
| if (toSteal) { |
| // The other's next block connects back to this allocator's current tail, and its new tail |
| // becomes the end of other's block linked list. |
| SkASSERT(other->fTail != &other->fHead); |
| toSteal->fPrev = fTail; |
| fTail->fNext = toSteal; |
| fTail = other->fTail; |
| // The other allocator becomes just its inline head block |
| other->fTail = &other->fHead; |
| other->fHead.fNext = nullptr; |
| } // else no block to steal |
| } |
| |
| void SkBlockAllocator::reset() { |
| for (Block* b : this->rblocks()) { |
| if (b == &fHead) { |
| // Reset metadata and cursor, tail points to the head block again |
| fTail = b; |
| b->fNext = nullptr; |
| b->fCursor = kDataStart; |
| b->fMetadata = 0; |
| // For reset(), but NOT releaseBlock(), the head allocatorMetadata and scratch block |
| // are reset/destroyed. |
| b->fAllocatorMetadata = 0; |
| b->poisonRange(kDataStart, b->fSize); |
| this->resetScratchSpace(); |
| } else { |
| delete b; |
| } |
| } |
| SkASSERT(fTail == &fHead && fHead.fNext == nullptr && fHead.fPrev == nullptr && |
| fHead.metadata() == 0 && fHead.fCursor == kDataStart); |
| |
| GrowthPolicy gp = static_cast<GrowthPolicy>(fGrowthPolicy); |
| fN0 = (gp == GrowthPolicy::kLinear || gp == GrowthPolicy::kExponential) ? 1 : 0; |
| fN1 = 1; |
| } |
| |
| void SkBlockAllocator::resetScratchSpace() { |
| if (fHead.fPrev) { |
| delete fHead.fPrev; |
| fHead.fPrev = nullptr; |
| } |
| } |
| |
| void SkBlockAllocator::addBlock(int minSize, int maxSize) { |
| SkASSERT(minSize > (int) sizeof(Block) && minSize <= maxSize); |
| |
| // Max positive value for uint:23 storage (decltype(fN0) picks up uint64_t, not uint:23). |
| static constexpr int kMaxN = (1 << 23) - 1; |
| static_assert(2 * kMaxN <= std::numeric_limits<int32_t>::max()); // Growth policy won't overflow |
| |
| auto alignAllocSize = [](int size) { |
| // Round to a nice boundary since the block isn't maxing out: |
| // if allocSize > 32K, aligns on 4K boundary otherwise aligns on max_align_t, to play |
| // nicely with jeMalloc (from SkArenaAlloc). |
| int mask = size > (1 << 15) ? ((1 << 12) - 1) : (kAddressAlign - 1); |
| return (size + mask) & ~mask; |
| }; |
| |
| int allocSize; |
| void* mem = nullptr; |
| if (this->scratchBlockSize() >= minSize) { |
| // Activate the scratch block instead of making a new block |
| SkASSERT(fHead.fPrev->isScratch()); |
| allocSize = fHead.fPrev->fSize; |
| mem = fHead.fPrev; |
| fHead.fPrev = nullptr; |
| } else if (minSize < maxSize) { |
| // Calculate the 'next' size per growth policy sequence |
| GrowthPolicy gp = static_cast<GrowthPolicy>(fGrowthPolicy); |
| int nextN1 = fN0 + fN1; |
| int nextN0; |
| if (gp == GrowthPolicy::kFixed || gp == GrowthPolicy::kLinear) { |
| nextN0 = fN0; |
| } else if (gp == GrowthPolicy::kFibonacci) { |
| nextN0 = fN1; |
| } else { |
| SkASSERT(gp == GrowthPolicy::kExponential); |
| nextN0 = nextN1; |
| } |
| fN0 = std::min(kMaxN, nextN0); |
| fN1 = std::min(kMaxN, nextN1); |
| |
| // However, must guard against overflow here, since all the size-based asserts prevented |
| // alignment/addition overflows, while multiplication requires 2x bits instead of x+1. |
| int sizeIncrement = fBlockIncrement * kAddressAlign; |
| if (maxSize / sizeIncrement < nextN1) { |
| // The growth policy would overflow, so use the max. We've already confirmed that |
| // maxSize will be sufficient for the requested minimumSize |
| allocSize = maxSize; |
| } else { |
| allocSize = std::min(alignAllocSize(std::max(minSize, sizeIncrement * nextN1)), |
| maxSize); |
| } |
| } else { |
| SkASSERT(minSize == maxSize); |
| // Still align on a nice boundary, no max clamping since that would just undo the alignment |
| allocSize = alignAllocSize(minSize); |
| } |
| |
| // Create new block and append to the linked list of blocks in this allocator |
| if (!mem) { |
| mem = operator new(allocSize); |
| } |
| fTail->fNext = new (mem) Block(fTail, allocSize); |
| fTail = fTail->fNext; |
| } |
| |
| #ifdef SK_DEBUG |
| void SkBlockAllocator::validate() const { |
| std::vector<const Block*> blocks; |
| const Block* prev = nullptr; |
| for (const Block* block : this->blocks()) { |
| blocks.push_back(block); |
| |
| SkASSERT(kAssignedMarker == block->fSentinel); |
| if (block == &fHead) { |
| // The head blocks' fPrev may be non-null if it holds a scratch block, but that's not |
| // considered part of the linked list |
| SkASSERT(!prev && (!fHead.fPrev || fHead.fPrev->isScratch())); |
| } else { |
| SkASSERT(prev == block->fPrev); |
| } |
| if (prev) { |
| SkASSERT(prev->fNext == block); |
| } |
| |
| SkASSERT(block->fSize >= (int) sizeof(Block)); |
| SkASSERT(block->fCursor >= kDataStart); |
| SkASSERT(block->fCursor <= block->fSize); |
| |
| prev = block; |
| } |
| SkASSERT(prev == fTail); |
| SkASSERT(!blocks.empty()); |
| SkASSERT(blocks[0] == &fHead); |
| |
| // Confirm reverse iteration matches forward iteration |
| size_t j = blocks.size(); |
| for (const Block* b : this->rblocks()) { |
| SkASSERT(b == blocks[j - 1]); |
| j--; |
| } |
| SkASSERT(j == 0); |
| } |
| #endif |