dwAllocationGranularity

dwAllocationGranularity is a term used in the context of Windows programming, specifically within the Windows API. It refers to the smallest unit of memory that can be allocated or freed by the system. This value is crucial for memory management and optimization, as it determines the alignment and size of memory blocks that can be allocated.

The dwAllocationGranularity value is typically retrieved using the GetSystemInfo function, which populates a SYSTEM_INFO structure. This structure contains various system-specific information, including the allocation granularity. The allocation granularity is expressed in bytes and is a power of two, commonly 64 KB (65536 bytes) on modern systems.

Understanding dwAllocationGranularity is important for developers who need to manage memory efficiently. For example, when mapping files into memory using the MapViewOfFile function, the starting address of the view must be a multiple of the allocation granularity. Failure to adhere to this requirement can result in errors or undefined behavior.

In summary, dwAllocationGranularity is a fundamental concept in Windows memory management, defining the smallest allocatable memory unit and influencing how memory is mapped and accessed. Developers should be aware of this value to ensure efficient and reliable memory operations in their applications.