typedef struct _LFH_HEAP
{
     RTL_CRITICAL_SECTION Lock;
     LIST_ENTRY SubSegmentZones;
     ULONG ZoneBlockSize;
     PVOID Heap;
     ULONG SegmentChange;
     ULONG SegmentCreate;
     ULONG SegmentInsertInFree;
     ULONG SegmentDelete;
     ULONG CacheAllocs;
     ULONG CacheFrees;
     USER_MEMORY_CACHE_ENTRY UserBlockCache[12];
     HEAP_BUCKET Buckets[128];
     HEAP_LOCAL_DATA LocalData[1];
} LFH_HEAP, *PLFH_HEAP;

Windows Vista Kernel Structures