MEMORY_REGION_INFORMATION - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTMMAPI_H

/**
 * The MEMORY_REGION_INFORMATION structure contains summary information about a virtual memory region.
 * The RegionType encoding is selected by the information class, not by the buffer size.
 * On x64, MemoryRegionInformation accepts a 24-byte prefix without CommitSize;
 * MemoryRegionInformationEx requires at least 32 bytes.
 */
typedef struct _MEMORY_REGION_INFORMATION
{
    PVOID AllocationBase;                  // Base address of the allocation.
    ULONG AllocationProtect;               // Page protection when the allocation was created (individual pages can be different from this value).
    ULONG RegionType;                      // MemoryRegionInformation: legacy MEM_* values; MemoryRegionInformationEx: MEMORY_REGION_INFORMATION_TYPE bits.
    SIZE_T RegionSize;                     // The combined size of pages in the region.
    SIZE_T CommitSize;                     // The commit charge associated with the allocation.
} MEMORY_REGION_INFORMATION, *PMEMORY_REGION_INFORMATION;

#endif

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This structure is documented in Windows SDK.