angle/src/common/PoolAlloc.cpp at main · google/angle

410 lines (353 loc) · 12.9 KB
// Copyright 2019 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// PoolAlloc.cpp:
//    Implements the class methods for PoolAllocator and Allocation classes.
#ifdef UNSAFE_BUFFERS_BUILD
#    pragma allow_unsafe_buffers
#include "common/PoolAlloc.h"
#include <assert.h>
#include <stdint.h>
#include <stdio.h>
#include <utility>
#include <utility>
#include "common/mathutil.h"
#include "common/platform.h"
#include "common/tls.h"
#if defined(ANGLE_WITH_ASAN)
#    include <sanitizer/asan_interface.h>
namespace angle
// If we are using guard blocks, we must track each individual allocation.  If we aren't using guard
// blocks, these never get instantiated, so won't have any impact.
class Allocation
    Allocation(size_t size, unsigned char *mem, Allocation *prev = 0)
        : mSize(size), mMem(mem), mPrevAlloc(prev)
        // Allocations are bracketed:
        //    [allocationHeader][initialGuardBlock][userData][finalGuardBlock]
        // This would be cleaner with if (kGuardBlockSize)..., but that makes the compiler print
        // warnings about 0 length memsets, even with the if() protecting them.
#if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
        memset(preGuard(), kGuardBlockBeginVal, kGuardBlockSize);
        memset(data(), kUserDataFill, mSize);
        memset(postGuard(), kGuardBlockEndVal, kGuardBlockSize);
    void checkAllocList() const;
    static size_t AlignedHeaderSize(uint8_t *allocationBasePtr, size_t alignment)
        // Make sure that the data offset after the header is aligned to the given alignment.
        size_t base = reinterpret_cast<size_t>(allocationBasePtr);
        return rx::roundUpPow2(base + kGuardBlockSize + HeaderSize(), alignment) - base;
    // Return total size needed to accommodate user buffer of 'size',
    // plus our tracking data and any necessary alignments.
    static size_t AllocationSize(uint8_t *allocationBasePtr,
                                 size_t size,
                                 size_t alignment,
                                 size_t *preAllocationPaddingOut)
        // The allocation will be laid out as such:
        //                      Aligned to |alignment|
        //   preAllocationPaddingOut     |
        //        ___^___                |
        //       <padding>[header][guard][data][guard]
        //       \___________ __________/
        //              dataOffset
        // Note that alignment is at least as much as a pointer alignment, so the pointers in the
        // header are also necessarily aligned appropriately.
        size_t dataOffset        = AlignedHeaderSize(allocationBasePtr, alignment);
        *preAllocationPaddingOut = dataOffset - HeaderSize() - kGuardBlockSize;
        return dataOffset + size + kGuardBlockSize;
    // Given memory pointing to |header|, returns |data|.
    static uint8_t *GetDataPointer(uint8_t *memory, size_t alignment)
        uint8_t *alignedPtr = memory + kGuardBlockSize + HeaderSize();
        // |memory| must be aligned already such that user data is aligned to |alignment|.
        ASSERT((reinterpret_cast<uintptr_t>(alignedPtr) & (alignment - 1)) == 0);
        return alignedPtr;
    void checkGuardBlock(unsigned char *blockMem, unsigned char val, const char *locText) const;
    void checkAlloc() const
        checkGuardBlock(preGuard(), kGuardBlockBeginVal, "before");
        checkGuardBlock(postGuard(), kGuardBlockEndVal, "after");
    // Find offsets to pre and post guard blocks, and user data buffer
    unsigned char *preGuard() const { return mMem + HeaderSize(); }
    unsigned char *data() const { return preGuard() + kGuardBlockSize; }
    unsigned char *postGuard() const { return data() + mSize; }
    size_t mSize;            // size of the user data area
    unsigned char *mMem;     // beginning of our allocation (points to header)
    Allocation *mPrevAlloc;  // prior allocation in the chain
    static constexpr unsigned char kGuardBlockBeginVal = 0xfb;
    static constexpr unsigned char kGuardBlockEndVal   = 0xfe;
    static constexpr unsigned char kUserDataFill       = 0xcd;
#if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
    static constexpr size_t kGuardBlockSize = 16;
    static constexpr size_t HeaderSize() { return sizeof(Allocation); }
    static constexpr size_t kGuardBlockSize = 0;
    static constexpr size_t HeaderSize() { return 0; }
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
class PageHeader
    PageHeader(PageHeader *nextPage, size_t pageCount)
        : nextPage(nextPage),
          pageCount(pageCount)
    PageHeader *nextPage;
    size_t pageCount;
#    if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
    Allocation *lastAllocation = nullptr;
// Implement the functionality of the PoolAllocator class, which
// is documented in PoolAlloc.h.
PoolAllocator::PoolAllocator(int growthIncrement, int allocationAlignment)
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
      mPageSize(growthIncrement),
      mFreeList(nullptr),
      mInUseList(nullptr),
      mNumCalls(0),
      mTotalBytes(0),
      mAlignment(allocationAlignment)
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
    mPageHeaderSkip = sizeof(PageHeader);
    // Alignment == 1 is a special fast-path where fastAllocate() is enabled
    if (mAlignment != 1)
        // Adjust mAlignment to be at least pointer aligned and
        // power of 2.
        size_t minAlign = sizeof(void *);
        if (mAlignment < minAlign)
            mAlignment = minAlign;
        mAlignment = gl::ceilPow2(static_cast<unsigned int>(mAlignment));
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
    // Don't allow page sizes we know are smaller than all common
    // OS page sizes.
    if (mPageSize < 4 * 1024)
        mPageSize = 4 * 1024;
    // A large mCurrentPageOffset indicates a new page needs to
    // be obtained to allocate memory.
    mCurrentPageOffset = mPageSize;
PoolAllocator::~PoolAllocator()
    reset();
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
    while (mFreeList)
        PageHeader *next = mFreeList->nextPage;
        delete[] reinterpret_cast<char *>(mFreeList);
        mFreeList = next;
// Check a single guard block for damage
void Allocation::checkGuardBlock(unsigned char *blockMem,
                                 unsigned char val,
                                 const char *locText) const
#if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
    for (size_t x = 0; x < kGuardBlockSize; x++)
        if (blockMem[x] != val)
            char assertMsg[80];
            // We don't print the assert message.  It's here just to be helpful.
            snprintf(assertMsg, sizeof(assertMsg),
                     "PoolAlloc: Damage %s %zu byte allocation at 0x%p\n", locText, mSize, data());
            assert(0 && "PoolAlloc: Damage in guard block");
void PoolAllocator::reset()
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
    mNumCalls   = 0;
    mTotalBytes = 0;
    mCurrentPageOffset = mPageSize;
    PageHeader *page   = std::exchange(mInUseList, nullptr);
    while (page)
        const size_t pageCount = page->pageCount;
        PageHeader *nextInUse  = page->nextPage;
#    if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
        if (page->lastAllocation)
            Allocation *allocations = std::exchange(page->lastAllocation, nullptr);
            allocations->checkAllocList();
        if (pageCount > 1)
            delete[] reinterpret_cast<uint8_t *>(page);
        else
#    if defined(ANGLE_WITH_ASAN)
            // Clear any container annotations left over from when the memory
            // was last used. (crbug.com/1419798)
            __asan_unpoison_memory_region(page, mPageSize);
            page->nextPage = mFreeList;
            mFreeList      = page;
        page = nextInUse;
#else  // !defined(ANGLE_DISABLE_POOL_ALLOC)
    mStack.clear();
void *PoolAllocator::allocate(size_t numBytes)
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
    // Just keep some interesting statistics.
    ++mNumCalls;
    mTotalBytes += numBytes;
    uint8_t *currentPagePtr = reinterpret_cast<uint8_t *>(mInUseList) + mCurrentPageOffset;
    size_t preAllocationPadding = 0;
    size_t allocationSize =
        Allocation::AllocationSize(currentPagePtr, numBytes, mAlignment, &preAllocationPadding);
    // Integer overflow is unexpected.
    ASSERT(allocationSize >= numBytes);
    // Do the allocation, most likely case first, for efficiency.
    if (allocationSize <= mPageSize - mCurrentPageOffset)
        // There is enough room to allocate from the current page at mCurrentPageOffset.
        uint8_t *memory = currentPagePtr + preAllocationPadding;
        mCurrentPageOffset += allocationSize;
        return initializeAllocation(memory, numBytes);
    if (allocationSize > mPageSize - mPageHeaderSkip)
        // If the allocation is larger than a whole page, do a multi-page allocation.  These are not
        // mixed with the others.  The OS is efficient in allocating and freeing multiple pages.
        // We don't know what the alignment of the new allocated memory will be, so conservatively
        // allocate enough memory for up to alignment extra bytes being needed.
        allocationSize = Allocation::AllocationSize(reinterpret_cast<uint8_t *>(mPageHeaderSkip),
                                                    numBytes, mAlignment, &preAllocationPadding);
        size_t numBytesToAlloc = allocationSize + mPageHeaderSkip + mAlignment;
        // Integer overflow is unexpected.
        ASSERT(numBytesToAlloc >= allocationSize);
        uint8_t *memory = new (std::nothrow) uint8_t[numBytesToAlloc];
        if (memory == nullptr)
            return nullptr;
        mInUseList =
            new (memory) PageHeader(mInUseList, (numBytesToAlloc + mPageSize - 1) / mPageSize);
        // Make next allocation come from a new page
        mCurrentPageOffset = mPageSize;
        // Now that we actually have the pointer, make sure the data pointer will be aligned.
        currentPagePtr = reinterpret_cast<uint8_t *>(mInUseList) + mPageHeaderSkip;
        Allocation::AllocationSize(currentPagePtr, numBytes, mAlignment, &preAllocationPadding);
        return initializeAllocation(currentPagePtr + preAllocationPadding, numBytes);
    uint8_t *newPageAddr = allocateNewPage(numBytes);
    return initializeAllocation(newPageAddr, numBytes);
#else  // !defined(ANGLE_DISABLE_POOL_ALLOC)
    uint8_t *alloc = new (std::nothrow) uint8_t[numBytes + mAlignment - 1];
    mStack.emplace_back(std::unique_ptr<uint8_t[]>(alloc));
    intptr_t intAlloc = reinterpret_cast<intptr_t>(alloc);
    intAlloc          = rx::roundUpPow2<intptr_t>(intAlloc, mAlignment);
    return reinterpret_cast<void *>(intAlloc);
#if !defined(ANGLE_DISABLE_POOL_ALLOC)
uint8_t *PoolAllocator::allocateNewPage(size_t numBytes)
    // Need a simple page to allocate from.  Pick a page from the free list, if any.  Otherwise need
    // to make the allocation.
    if (mFreeList)
        PageHeader *page = mFreeList;
        mFreeList = mFreeList->nextPage;
        page->nextPage   = mInUseList;
        mInUseList       = page;
        uint8_t *memory = new (std::nothrow) uint8_t[mPageSize];
        if (memory == nullptr)
            return nullptr;
        mInUseList = new (memory) PageHeader(mInUseList, 1);
    // Leave room for the page header.
    mCurrentPageOffset      = mPageHeaderSkip;
    uint8_t *currentPagePtr = reinterpret_cast<uint8_t *>(mInUseList) + mCurrentPageOffset;
    size_t preAllocationPadding = 0;
    size_t allocationSize =
        Allocation::AllocationSize(currentPagePtr, numBytes, mAlignment, &preAllocationPadding);
    mCurrentPageOffset += allocationSize;
    // The new allocation is made after the page header and any alignment required before it.
    return reinterpret_cast<uint8_t *>(mInUseList) + mPageHeaderSkip + preAllocationPadding;
void *PoolAllocator::initializeAllocation(uint8_t *memory, size_t numBytes)
#    if defined(ANGLE_POOL_ALLOC_GUARD_BLOCKS)
    mInUseList->lastAllocation =
        new (memory) Allocation(numBytes, memory, mInUseList->lastAllocation);
    return Allocation::GetDataPointer(memory, mAlignment);
// Check all allocations in a list for damage by calling check on each.
void Allocation::checkAllocList() const
    for (const Allocation *alloc = this; alloc != nullptr; alloc = alloc->mPrevAlloc)
        alloc->checkAlloc();
}  // namespace angle
Provide feedback

Saved searches

Use saved searches to filter your results more quickly

FilesExpand file tree

PoolAlloc.cpp

Latest commit

History

PoolAlloc.cpp

File metadata and controls
