Techwiki:Win32k/VMEMHEAP

typedef struct _VMEMHEAP
{  
       DWORD  dwFlags;  
       DWORD  stride;  
       LPVOID  freeList;  
       LPVOID  allocList;  
       DWORD  dwTotalSize;  
       FLATPTR  fpGARTLin;  
       FLATPTR  fpGARTDev;  
       DWORD  dwCommitedSize;  
       DWORD  dwCoalesceCount;  
       HEAPALIGNMENT  Alignment;  
       DDSCAPSEX  ddsCapsEx;  
       DDSCAPSEX  ddsCapsExAlt;  
       LARGE_INTEGER  liPhysAGPBase;  
       PEDD_DIRECTDRAW_GLOBAL hdevAGP;  
       LPVOID  pvPhysRsrv;
       BYTE* pAgpCommitMask;
       DWORD dwAgpCommitMaskSize;
} VMEMHEAP, FAR *LPVMEMHEAP;

hdevAGP in msdn it is declare as handle but the true nature it is a EDD_DIRECTDRAW_GLOBAL struct

pAgpCommitMask and dwAgpCommitMaskSize found in older ddk it is still in use in windows xp, but it is not public documented in msdn

References

• http://msdn.microsoft.com/en-us/library/ms793889.aspx
• http://www.osronline.com/ddkx/graphics/ddstrcts_16ef.htm