XMem API Reference

Reference material for memory allocation APIs.

There are two functions which the operating system and middleware can call to perform memory operations which can be hooked by your title – XMemAlloc to allocate memory, and XMemFree to free blocks which were previously allocated by a call to XMemAlloc. Both of these functions take a dwAttributes parameter which identifies the type of allocation, the subsystem performing the allocation, and define the parameters which need to be honored for the allocation itself. The default implementations of these functions are XMemAllocDefault and XMemFreeDefault, which can be called by your title if it does not understand the kind of allocation being requested. Alternatively, you may wish to leave the entire implementation to the operating system and always call the default functions, using the hooks solely to track allocations and frees for debugging purposes.

Functions

Name	Description
AllocateTitlePhysicalPages	Allocates the requested amount of memory in separate contiguous runs.
FreeTitlePhysicalPages	Used to free pages allocated with AllocateTitlePhysicalPages.
MAKE_XALLOC_ATTRIBUTES	Inline helper function used to compose the dwAttributes parameter to XMEMALLOC_ROUTINE.
MapTitlePhysicalPages	Maps pages allocated by AllocateTitlePhysicalPages into the virtual address space.
TitleMemoryStatus	Retrieves information about the current usage of memory accessible to the title.
VirtualAlloc	Application-defined memory allocation callback function that replaces the default memory allocator.
VirtualFree	Releases or decommits a region of pages within the virtual address space of the calling process.
XMemAlloc	Application-defined memory allocation callback function that replaces the default memory allocator.
XMEMALLOC_ROUTINE	Defines the syntax of the memory allocation routines, XMemAlloc and XMemAllocDefault.
XMemAllocDefault	The default memory allocation routine.
XMemFree	Application-defined memory deallocation callback function that replaces the default memory deallocator.
XMEMFREE_ROUTINE	Defines the syntax of the memory deallocation routines, XMemFree and XMemFreeDefault.
XMemFreeDefault	Default memory free function.
XMemGetAllocationHysteresis	Gets the hysteresis amount for a given heap, rounded up to an internal allocation boundary (4 MB).
XMemGetAllocationStatistics	Queries the hysteresis amount for a given heap.
XMemPreallocateFreeSpace	Allocates free pages for a heap up to its hysteresis value.
XMemSetAllocationHooks	Used by titles to register memory allocation hooks.
XMemSetAllocationHysteresis	Sets the hysteresis amount for a given heap, rounded up to an internal allocation boundary (4 MB).

Structures

Name	Description
TITLEMEMORYSTATUS	Describes the current usage of memory accessible to the title.
XALLOC_ATTRIBUTES	Contains values that describe the attributes of a memory allocation.
XMEM_HEAP_STATISTICS	A statistics structure for a given heap.

Enumerations

Name	Description
XALLOC_ALLOCATOR_IDS	Defines the range for the set of IDs for different types of allocators used by memory allocation routines.

See also

White Paper: Xbox One XDK Memory Management

White Paper: Xbox One Memory System