System.THeapStatus Record

THeapStatus represents information about the global heap.

Pascal

THeapStatus = record
  TotalAddrSpace: Cardinal;
  TotalUncommitted: Cardinal;
  TotalCommitted: Cardinal;
  TotalAllocated: Cardinal;
  TotalFree: Cardinal;
  FreeSmall: Cardinal;
  FreeBig: Cardinal;
  Unused: Cardinal;
  Overhead: Cardinal;
  HeapErrorCode: Cardinal;
end;

C++

struct THeapStatus {
  unsigned TotalAddrSpace;
  unsigned TotalUncommitted;
  unsigned TotalCommitted;
  unsigned TotalAllocated;
  unsigned TotalFree;
  unsigned FreeSmall;
  unsigned FreeBig;
  unsigned Unused;
  unsigned Overhead;
  unsigned HeapErrorCode;
};

File

System

Description

THeapStatus represents information about the current memory manager. These are the meanings of the values in each field:

Field	Meaning
TotalAddrSpace	The (current) total address space available to your program, in bytes. This will grow as your program's dynamic memory usage grows.
TotalUncommitted	The total number of bytes (of TotalAddrSpace) for which space has not been allocated in the swap file.
TotalCommitted	The total number of bytes (of TotalAddrSpace) for which space has been allocated in the swap file. Note : TotalUncommitted + TotalCommitted = TotalAddrSpace
TotalAllocated	The total number of bytes dynamically allocated by your program.
TotalFree	The total number of free bytes available in the (current) address space for allocation by your program. If this number is exceeded, and enough virtual memory is available, more address space will be allocated from the OS; TotalAddrSpace will be incremented accordingly.
FreeSmall	Total bytes of small memory blocks which are not currently allocated by your program.
FreeBig	Total bytes of big memory blocks which are not currently allocated by your program. Large free blocks can be created by coalescing smaller, contiguous, free blocks or by freeing a large dynamic allocation. (The exact size of the blocks is immaterial).
Unused	Total bytes which have never been allocated by your program. Note : Unused + FreeBig + FreeSmall = TotalFree These three fields (Unused, FreeBig, and FreeSmall) refer to dynamic allocation by the user program.
Overhead	The total number of bytes required by the heap manager to manage all the blocks dynamically allocated by your program.
HeapErrorCode	Indicates the current status of the heap, as internally determined.

Note: TotalAddrSpace, TotalUncommitted and TotalCommitted refer to OS memory used by the program, whereas TotalAllocated and TotalFree refer to the heap memory used within the program by dynamic allocations. Therefore, to monitor dynamic memory used in your program use TotalAllocated and TotalFree.

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