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Diffstat (limited to 'gfx/angle/checkout/src/common/PoolAlloc.h')
| -rw-r--r-- | gfx/angle/checkout/src/common/PoolAlloc.h | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/gfx/angle/checkout/src/common/PoolAlloc.h b/gfx/angle/checkout/src/common/PoolAlloc.h new file mode 100644 index 0000000000..536848f198 --- /dev/null +++ b/gfx/angle/checkout/src/common/PoolAlloc.h @@ -0,0 +1,181 @@ +// +// 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.h: +// Defines the class interface for PoolAllocator. +// + +#ifndef COMMON_POOLALLOC_H_ +#define COMMON_POOLALLOC_H_ + +#if !defined(NDEBUG) +# define ANGLE_POOL_ALLOC_GUARD_BLOCKS // define to enable guard block checking +#endif + +// +// This header defines an allocator that can be used to efficiently +// allocate a large number of small requests for heap memory, with the +// intention that they are not individually deallocated, but rather +// collectively deallocated at one time. +// +// This simultaneously +// +// * Makes each individual allocation much more efficient; the +// typical allocation is trivial. +// * Completely avoids the cost of doing individual deallocation. +// * Saves the trouble of tracking down and plugging a large class of leaks. +// +// Individual classes can use this allocator by supplying their own +// new and delete methods. +// + +#include "angleutils.h" +#include "common/debug.h" + +namespace angle +{ +class Allocation; +class PageHeader; + +// +// There are several stacks. One is to track the pushing and popping +// of the user, and not yet implemented. The others are simply a +// repositories of free pages or used pages. +// +// Page stacks are linked together with a simple header at the beginning +// of each allocation obtained from the underlying OS. Multi-page allocations +// are returned to the OS. Individual page allocations are kept for future +// re-use. +// +// The "page size" used is not, nor must it match, the underlying OS +// page size. But, having it be about that size or equal to a set of +// pages is likely most optimal. +// +class PoolAllocator : angle::NonCopyable +{ + public: + static const int kDefaultAlignment = sizeof(void *); + // + // Create PoolAllocator. If alignment is set to 1 byte then fastAllocate() + // function can be used to make allocations with less overhead. + // + PoolAllocator(int growthIncrement = 8 * 1024, int allocationAlignment = kDefaultAlignment); + + // + // Don't call the destructor just to free up the memory, call pop() + // + ~PoolAllocator(); + + // + // Initialize page size and alignment after construction + // + void initialize(int pageSize, int alignment); + + // + // Call push() to establish a new place to pop memory to. Does not + // have to be called to get things started. + // + void push(); + + // + // Call pop() to free all memory allocated since the last call to push(), + // or if no last call to push, frees all memory since first allocation. + // + void pop(); + + // + // Call popAll() to free all memory allocated. + // + void popAll(); + + // + // Call allocate() to actually acquire memory. Returns 0 if no memory + // available, otherwise a properly aligned pointer to 'numBytes' of memory. + // + void *allocate(size_t numBytes); + + // + // Call fastAllocate() for a faster allocate function that does minimal bookkeeping + // preCondition: Allocator must have been created w/ alignment of 1 + ANGLE_INLINE uint8_t *fastAllocate(size_t numBytes) + { +#if defined(ANGLE_DISABLE_POOL_ALLOC) + return reinterpret_cast<uint8_t *>(allocate(numBytes)); +#else + ASSERT(mAlignment == 1); + // No multi-page allocations + ASSERT(numBytes <= (mPageSize - mPageHeaderSkip)); + // + // Do the allocation, most likely case inline first, for efficiency. + // + if (numBytes <= mPageSize - mCurrentPageOffset) + { + // + // Safe to allocate from mCurrentPageOffset. + // + uint8_t *memory = reinterpret_cast<uint8_t *>(mInUseList) + mCurrentPageOffset; + mCurrentPageOffset += numBytes; + return memory; + } + return allocateNewPage(numBytes); +#endif + } + + // There is no deallocate. The point of this class is that deallocation can be skipped by the + // user of it, as the model of use is to simultaneously deallocate everything at once by calling + // pop(), and to not have to solve memory leak problems. + + // Catch unwanted allocations. + // TODO(jmadill): Remove this when we remove the global allocator. + void lock(); + void unlock(); + + private: + size_t mAlignment; // all returned allocations will be aligned at + // this granularity, which will be a power of 2 +#if !defined(ANGLE_DISABLE_POOL_ALLOC) + struct AllocState + { + size_t offset; + PageHeader *page; + }; + using AllocStack = std::vector<AllocState>; + + // Slow path of allocation when we have to get a new page. + uint8_t *allocateNewPage(size_t numBytes); + // Track allocations if and only if we're using guard blocks + void *initializeAllocation(uint8_t *memory, size_t numBytes); + + // Granularity of allocation from the OS + size_t mPageSize; + // Amount of memory to skip to make room for the page header (which is the size of the page + // header, or PageHeader in PoolAlloc.cpp) + size_t mPageHeaderSkip; + // Next offset in top of inUseList to allocate from. This offset is not necessarily aligned to + // anything. When an allocation is made, the data is aligned to mAlignment, and the header (if + // any) will align to pointer size by extension (since mAlignment is made aligned to at least + // pointer size). + size_t mCurrentPageOffset; + // List of popped memory + PageHeader *mFreeList; + // List of all memory currently being used. The head of this list is where allocations are + // currently being made from. + PageHeader *mInUseList; + // Stack of where to allocate from, to partition pool + AllocStack mStack; + + int mNumCalls; // just an interesting statistic + size_t mTotalBytes; // just an interesting statistic + +#else // !defined(ANGLE_DISABLE_POOL_ALLOC) + std::vector<std::vector<void *>> mStack; +#endif + + bool mLocked; +}; + +} // namespace angle + +#endif // COMMON_POOLALLOC_H_ |