typedef struct _MM_AVL_TABLE
{
     MMADDRESS_NODE BalancedRoot;
     ULONG DepthOfTree: 5;
     ULONG Unused: 3;
     ULONG NumberGenericTableElements: 24;
     PVOID NodeHint;
     PVOID NodeFreeHint;
} MM_AVL_TABLE, *PMM_AVL_TABLE;

Windows Vista Kernel Structures