#ifndef _NTRTL_H

typedef struct _RTL_HEAP_PARAMETERS
{
    ULONG Length;
    SIZE_T SegmentReserve;
    SIZE_T SegmentCommit;
    SIZE_T DeCommitFreeBlockThreshold;
    SIZE_T DeCommitTotalFreeThreshold;
    SIZE_T MaximumAllocationSize;
    SIZE_T VirtualMemoryThreshold;
    SIZE_T InitialCommit;
    SIZE_T InitialReserve;
    PRTL_HEAP_COMMIT_ROUTINE CommitRoutine;
    SIZE_T Reserved[2];
} RTL_HEAP_PARAMETERS, *PRTL_HEAP_PARAMETERS;

#endif
View code on GitHub

// ntifs.h

typedef struct _RTL_HEAP_PARAMETERS {
  ULONG                    Length;
  SIZE_T                   SegmentReserve;
  SIZE_T                   SegmentCommit;
  SIZE_T                   DeCommitFreeBlockThreshold;
  SIZE_T                   DeCommitTotalFreeThreshold;
  SIZE_T                   MaximumAllocationSize;
  SIZE_T                   VirtualMemoryThreshold;
  SIZE_T                   InitialCommit;
  SIZE_T                   InitialReserve;
  PRTL_HEAP_COMMIT_ROUTINE CommitRoutine;
  SIZE_T                   Reserved[2];
} RTL_HEAP_PARAMETERS, *PRTL_HEAP_PARAMETERS;
View the official Windows Driver Kit DDI reference

NtDoc

This structure is documented in Windows Driver Kit.

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Windows Driver Kit DDI reference (ns-ntifs-rtl_heap_parameters)

Description

The RTL_HEAP_PARAMETERS structure contains parameters to be applied when creating a heap.

Members

`Length`

Size, in bytes, of the RTL_HEAP_PARAMETERS structure.

`SegmentReserve`

Segment reserve size, in bytes. If this value is not specified, 1 MB is used.

`SegmentCommit`

Segment commit size, in bytes. If this value is not specified, PAGE_SIZE * 2 is used.

`DeCommitFreeBlockThreshold`

Decommit free block threshold, in bytes. If this value is not specified, PAGE_SIZE is used.

`DeCommitTotalFreeThreshold`

Decommit total free threshold, in bytes. If this value is not specified, 65536 is used.

`MaximumAllocationSize`

Size, in bytes, of the largest block of memory that can be allocated from the heap. If this value is not specified, the difference between the highest and lowest addresses, less one page, is used.

`VirtualMemoryThreshold`

Virtual memory threshold, in bytes. If this value is not specified, or if it is greater than the maximum heap block size, the maximum heap block size of 0x7F000 is used.

`InitialCommit`

Initial amount of memory, in bytes, to commit for the heap. Must be less than or equal to InitialReserve. If HeapBase and CommitRoutine are non-NULL, this parameter, which overrides the value of CommitSize, must be a nonzero value; otherwise it is ignored.

`InitialReserve`

Initial amount of memory, in bytes, to reserve for the heap. If HeapBase and CommitRoutine are non-NULL, this parameter, which overrides the value of ReserveSize, must be a nonzero value; otherwise it is ignored.

`CommitRoutine`

Pointer to a RTL_HEAP_COMMIT_ROUTINE routine to commit pages from the heap. If this parameter is non-NULL, the heap must be nongrowable. If HeapBase is NULL, CommitRoutine must also be NULL.

`Reserved`

Reserved for system use. Drivers must set this parameter to zero.

RTL_HEAP_PARAMETERS - NtDoc