typedef struct _GENERAL_LOOKASIDE_POOL
{
     union
     {
          SLIST_HEADER ListHead;
          SINGLE_LIST_ENTRY SingleListHead;
     };
     WORD Depth;
     WORD MaximumDepth;
     ULONG TotalAllocates;
     union
     {
          ULONG AllocateMisses;
          ULONG AllocateHits;
     };
     ULONG TotalFrees;
     union
     {
          ULONG FreeMisses;
          ULONG FreeHits;
     };
     POOL_TYPE Type;
     ULONG Tag;
     ULONG Size;
     union
     {
          PVOID * AllocateEx;
          PVOID * Allocate;
     };
     union
     {
          PVOID FreeEx;
          PVOID Free;
     };
     LIST_ENTRY ListEntry;
     ULONG LastTotalAllocates;
     union
     {
          ULONG LastAllocateMisses;
          ULONG LastAllocateHits;
     };
     ULONG Future[2];
} GENERAL_LOOKASIDE_POOL, *PGENERAL_LOOKASIDE_POOL;

Windows Vista Kernel Structures