How to implement memory pool in C++?

Memory pool is a technology that optimizes memory allocation by pre-allocating memory blocks to reduce allocation and release overhead. In C++, memory pools can be implemented using std::pmr::memory_resource and std::pmr::polymorphic_allocator classes, such as the MemoryPool class, which does this by specifying the memory pool size through a constructor and reducing the available memory when allocating memory. Memory pool function. In addition, the practical case shows an example of using the memory pool to optimize integer allocation. By using the memory pool to allocate 1000 integers, the performance of memory allocation and deallocation can be improved.

Memory pool in C++

Introduction
The memory pool is a kind of management tool Memory allocation optimization techniques. It can pre-allocate a batch of memory and divide it into smaller chunks so that these chunks can be allocated and freed quickly. This can greatly reduce the overhead of memory allocation and deallocation, thereby improving application performance.

Implementation
In C++, you can use the std::pmr::memory_resource and std::pmr::polymorphic_allocator classes To implement the memory pool.

#include <memory_resource>

class MemoryPool : public std::pmr::memory_resource {
public:
  // 构造函数，指定内存池的大小
  MemoryPool(size_t size) : _data(new char[size]), _available(size) {}

  // 分配内存
  void* do_allocate(size_t size, size_t alignment) override {
    if (_available >= size) {
      void* ptr = _data + (_size - _available);
      _available -= size;
      return ptr;
    }
    return nullptr;
  }

  // 释放内存
  void do_deallocate(void* ptr, size_t size, size_t alignment) override {
    _available += size;
  }

private:
  char* _data;  // 内存池数据
  size_t _size;  // 内存池大小
  size_t _available;  // 可用内存大小
};

Practical case
The following is an example of using the memory pool to optimize memory allocation:

#include "MemoryPool.h"

int main() {
  // 创建一个 1 MB 大小的内存池
  std::pmr::polymorphic_allocator<int> allocator(new MemoryPool(1024 * 1024));

  // 使用内存池分配 1000 个整数
  int* arr = allocator.allocate(1000);

  // 使用完整数后释放内存
  allocator.deallocate(arr, 1000);

  return 0;
}

In this example, using the memory pool to allocate 1000 integers can Significantly improves the performance of memory allocation and deallocation.

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