[{"_1":2,"_50":-5,"_51":-5},"loaderData",{"_3":4,"_7":8,"_49":-5},"root",{"_5":6},"path","/blogs/tags/performance-optimization","pages/Tag",{"_9":10,"_45":46,"_19":22,"_47":48},"posts",[11],{"_12":13,"_14":15,"_16":17,"_19":20,"_23":24,"_25":26,"_27":28,"_31":32,"_35":36,"_37":38},"id","clzs54c4g2e0g07o554yr6qne","publishDate","2024-08-08","category",[18],"programming","tag",[21,22],"c++","performance-optimization","slug","developing-a-custom-memory-allocator-in-c","title","Developing a Custom Memory Allocator in C++","excerpt",{"_29":30},"text","Explore the intricacies of memory management by developing a custom memory allocator in C++. Learn how to design and implement a memory pool, allocate and deallocate memory, and optimize performance with a hands-on example.","coverImg",{"_33":34},"url","https://ap-south-1.graphassets.com/AHDh3MjtFRAmkhgRu025Qz/UBsBPDoQQ6VQUof3F9YG","content","In this blog, we will dive into the intricacies of memory management by developing a custom memory allocator in C++. This is an advanced topic that can help you optimize your applications by having more control over how memory is allocated and deallocated.\n\n# Introduction\n\nMemory management is a crucial aspect of system-level programming. While C++ provides standard memory management facilities, there are scenarios where a custom memory allocator can provide significant performance improvements and more predictable memory usage.\n\n# Why Use a Custom Memory Allocator?\n\nCustom memory allocators can:\n- Reduce fragmentation\n- Increase allocation and deallocation speed\n- Provide more predictable memory usage patterns\n- Be tailored to the specific needs of your application\n\n# Basic Concepts\n\nBefore we start, let's review some basic concepts:\n- **Memory Pool**: A large block of memory from which smaller chunks are allocated.\n- **Free List**: A linked list of free memory blocks that can be reused.\n- **Alignment**: Ensuring that memory addresses meet certain alignment requirements.\n\n# Designing the Allocator\n\nWe'll design a simple allocator with the following features:\n- A fixed-size memory pool\n- A free list for managing available blocks\n- Support for basic allocation and deallocation operations\n\n# Implementation\n\n## Memory Pool\n\nWe'll start by defining a memory pool that will act as the source of memory for our allocator.\n\n```cpp\n#include \n#include \n#include \n\nclass MemoryPool {\npublic:\n MemoryPool(size_t size);\n ~MemoryPool();\n\n void* allocate(size_t size);\n void deallocate(void* ptr);\n\nprivate:\n struct FreeBlock {\n FreeBlock* next;\n };\n\n char* pool;\n size_t poolSize;\n FreeBlock* freeList;\n\n void* alignPointer(void* ptr, size_t alignment);\n};\n\nMemoryPool::MemoryPool(size_t size)\n : poolSize(size), freeList(nullptr) {\n pool = new char[size];\n freeList = reinterpret_cast(pool);\n freeList->next = nullptr;\n}\n\nMemoryPool::~MemoryPool() {\n delete[] pool;\n}\n\nvoid* MemoryPool::alignPointer(void* ptr, size_t alignment) {\n uintptr_t addr = reinterpret_cast(ptr);\n size_t offset = addr % alignment;\n if (offset != 0) {\n addr += (alignment - offset);\n }\n return reinterpret_cast(addr);\n}\n\nvoid* MemoryPool::allocate(size_t size) {\n // Align the requested size to the alignment of FreeBlock\n size = (size + sizeof(FreeBlock) - 1) & ~(sizeof(FreeBlock) - 1);\n\n FreeBlock* prev = nullptr;\n FreeBlock* curr = freeList;\n\n while (curr != nullptr) {\n if (reinterpret_cast(curr) + size <= pool + poolSize) {\n if (prev != nullptr) {\n prev->next = curr->next;\n } else {\n freeList = curr->next;\n }\n return reinterpret_cast(curr);\n }\n prev = curr;\n curr = curr->next;\n }\n return nullptr; // No suitable block found\n}\n\nvoid MemoryPool::deallocate(void* ptr) {\n FreeBlock* block = reinterpret_cast(ptr);\n block->next = freeList;\n freeList = block;\n}\n\nint main() {\n const size_t poolSize = 1024;\n MemoryPool allocator(poolSize);\n\n void* p1 = allocator.allocate(128);\n std::cout << \"Allocated 128 bytes at \" << p1 << std::endl;\n\n void* p2 = allocator.allocate(256);\n std::cout << \"Allocated 256 bytes at \" << p2 << std::endl;\n\n allocator.deallocate(p1);\n std::cout << \"Deallocated memory at \" << p1 << std::endl;\n\n void* p3 = allocator.allocate(64);\n std::cout << \"Allocated 64 bytes at \" << p3 << std::endl;\n\n return 0;\n}\n```\n\n### Explanation\nMemoryPool Constructor\nThe constructor initializes the memory pool and sets up the initial free list.\n\n```cpp\nMemoryPool::MemoryPool(size_t size)\n : poolSize(size), freeList(nullptr) {\n pool = new char[size];\n freeList = reinterpret_cast(pool);\n freeList->next = nullptr;\n}\n```\n\n**Align Pointer**\nThe `alignPointer` function ensures that the memory addresses meet certain alignment requirements.\n\n```cpp\nvoid* MemoryPool::alignPointer(void* ptr, size_t alignment) {\n uintptr_t addr = reinterpret_cast(ptr);\n size_t offset = addr % alignment;\n if (offset != 0) {\n addr += (alignment - offset);\n }\n return reinterpret_cast(addr);\n}\n```\n\n**Allocate Memory**\nThe `allocate` function searches the free list for a suitable block and returns a pointer to the allocated memory.\n\n```cpp\nvoid* MemoryPool::allocate(size_t size) {\n size = (size + sizeof(FreeBlock) - 1) & ~(sizeof(FreeBlock) - 1);\n\n FreeBlock* prev = nullptr;\n FreeBlock* curr = freeList;\n\n while (curr != nullptr) {\n if (reinterpret_cast(curr) + size <= pool + poolSize) {\n if (prev != nullptr) {\n prev->next = curr->next;\n } else {\n freeList = curr->next;\n }\n return reinterpret_cast(curr);\n }\n prev = curr;\n curr = curr->next;\n }\n return nullptr;\n}\n```\n\n**Deallocate Memory**\nThe `deallocate` function adds the deallocated block back to the free list.\n\n```cpp\nvoid MemoryPool::deallocate(void* ptr) {\n FreeBlock* block = reinterpret_cast(ptr);\n block->next = freeList;\n freeList = block;\n}\n```\n\n## Testing the Allocator\nHere is a simple main function to test our allocator.\n\n```cpp\nint main() {\n const size_t poolSize = 1024;\n MemoryPool allocator(poolSize);\n\n void* p1 = allocator.allocate(128);\n std::cout << \"Allocated 128 bytes at \" << p1 << std::endl;\n\n void* p2 = allocator.allocate(256);\n std::cout << \"Allocated 256 bytes at \" << p2 << std::endl;\n\n allocator.deallocate(p1);\n std::cout << \"Deallocated memory at \" << p1 << std::endl;\n\n void* p3 = allocator.allocate(64);\n std::cout << \"Allocated 64 bytes at \" << p3 << std::endl;\n\n return 0;\n}\n```\n\n# Performance Comparison\n\nYou can add performance comparison code to benchmark our custom allocator against the standard `new` and `delete` operators to demonstrate the benefits.\n\n```cpp\n#include \n\nvoid benchmarkAllocator() {\n const size_t poolSize = 1024 * 1024;\n const size_t numAllocations = 10000;\n const size_t blockSize = 128;\n\n MemoryPool allocator(poolSize);\n\n auto start = std::chrono::high_resolution_clock::now();\n for (size_t i = 0; i < numAllocations; ++i) {\n void* ptr = allocator.allocate(blockSize);\n allocator.deallocate(ptr);\n }\n auto end = std::chrono::high_resolution_clock::now();\n std::chrono::duration duration = end - start;\n\n std::cout << \"Custom allocator duration: \" << duration.count() << \" seconds\" << std::endl;\n\n start = std::chrono::high_resolution_clock::now();\n for (size_t i = 0; i < numAllocations; ++i) {\n void* ptr = operator new(blockSize);\n operator delete(ptr);\n }\n end = std::chrono::high_resolution_clock::now();\n duration = end - start;\n\n std::cout << \"Standard allocator duration: \" << duration.count() << \" seconds\" << std::endl;\n}\n\nint main() {\n benchmarkAllocator();\n return 0;\n}\n```\n\n# Conclusion\nCustom memory allocators can provide significant performance benefits and more predictable memory usage. By understanding and implementing a basic allocator, you can tailor memory management to the specific needs of your application.","author",{"_39":40,"_41":42,"_43":44},"name","Dexter","img","https://avatars.githubusercontent.com/u/71167911?v=4","social","https://github.com/dexter-xD","hasMorePosts",false,"page",1,"layouts/HomeLayout","actionData","errors"]