C Specification

To allocate memory objects, call:

// Provided by VK_VERSION_1_0
VkResult vkAllocateMemory(
    VkDevice                                    device,
    const VkMemoryAllocateInfo*                 pAllocateInfo,
    const VkAllocationCallbacks*                pAllocator,
    VkDeviceMemory*                             pMemory);

Parameters

  • device is the logical device that owns the memory.

  • pAllocateInfo is a pointer to a VkMemoryAllocateInfo structure describing parameters of the allocation. A successfully returned allocation must use the requested parameters — no substitution is permitted by the implementation.

  • pAllocator controls host memory allocation as described in the Memory Allocation chapter.

  • pMemory is a pointer to a VkDeviceMemory handle in which information about the allocated memory is returned.

Description

Allocations returned by vkAllocateMemory are guaranteed to meet any alignment requirement of the implementation. For example, if an implementation requires 128 byte alignment for images and 64 byte alignment for buffers, the device memory returned through this mechanism would be 128-byte aligned. This ensures that applications can correctly suballocate objects of different types (with potentially different alignment requirements) in the same memory object.

When memory is allocated, its contents are undefined with the following constraint:

  • The contents of unprotected memory must not be a function of the contents of data protected memory objects, even if those memory objects were previously freed.

Note

The contents of memory allocated by one application should not be a function of data from protected memory objects of another application, even if those memory objects were previously freed.

The maximum number of valid memory allocations that can exist simultaneously within a VkDevice may be restricted by implementation- or platform-dependent limits. The maxMemoryAllocationCount feature describes the number of allocations that can exist simultaneously before encountering these internal limits.

Note

For historical reasons, if maxMemoryAllocationCount is exceeded, some implementations may return VK_ERROR_TOO_MANY_OBJECTS. Exceeding this limit will result in undefined behavior, and an application should not rely on the use of the returned error code in order to identify when the limit is reached.

Note

Many protected memory implementations involve complex hardware and system software support, and often have additional and much lower limits on the number of simultaneous protected memory allocations (from memory types with the VK_MEMORY_PROPERTY_PROTECTED_BIT property) than for non-protected memory allocations. These limits can be system-wide, and depend on a variety of factors outside of the Vulkan implementation, so can’t be queried in Vulkan. Applications should use as few allocations as possible from such memory types by suballocating aggressively, and be prepared for allocation failure even when there is apparently plenty of capacity remaining in the memory heap. As a guideline, the Vulkan conformance test suite requires that at least 80 minimum-size allocations can exist concurrently when no other uses of protected memory are active in the system.

Some platforms may have a limit on the maximum size of a single allocation. For example, certain systems may fail to create allocations with a size greater than or equal to 4GB. Such a limit is implementation-dependent, and if such a failure occurs then the error VK_ERROR_OUT_OF_DEVICE_MEMORY must be returned. This limit is advertised in VkPhysicalDeviceMaintenance3Properties::maxMemoryAllocationSize.

The cumulative memory size allocated to a heap can be limited by the size of the specified heap. In such cases, allocated memory is tracked on a per-device and per-heap basis. Some platforms allow overallocation into other heaps. The overallocation behavior can be specified through the VK_AMD_memory_overallocation_behavior extension.

If the VkPhysicalDevicePageableDeviceLocalMemoryFeaturesEXT::pageableDeviceLocalMemory feature is enabled, memory allocations made from a heap that includes VK_MEMORY_HEAP_DEVICE_LOCAL_BIT in VkMemoryHeap::flags may be transparently moved to host-local memory allowing multiple applications to share device-local memory. If there is no space left in device-local memory when this new allocation is made, other allocations may be moved out transparently to make room. The operating system will determine which allocations to move to device-local memory or host-local memory based on platform-specific criteria. To help the operating system make good choices, the application should set the appropriate memory priority with VkMemoryPriorityAllocateInfoEXT and adjust it as necessary with vkSetDeviceMemoryPriorityEXT. Higher priority allocations will moved to device-local memory first.

Memory allocations made on heaps without the VK_MEMORY_HEAP_DEVICE_LOCAL_BIT property will not be transparently promoted to device-local memory by the operating system.

Valid Usage
Valid Usage (Implicit)
  • VUID-vkAllocateMemory-device-parameter
    device must be a valid VkDevice handle

  • VUID-vkAllocateMemory-pAllocateInfo-parameter
    pAllocateInfo must be a valid pointer to a valid VkMemoryAllocateInfo structure

  • VUID-vkAllocateMemory-pAllocator-parameter
    If pAllocator is not NULL, pAllocator must be a valid pointer to a valid VkAllocationCallbacks structure

  • VUID-vkAllocateMemory-pMemory-parameter
    pMemory must be a valid pointer to a VkDeviceMemory handle

Return Codes
On success, this command returns
  • VK_SUCCESS

On failure, this command returns
  • VK_ERROR_OUT_OF_HOST_MEMORY

  • VK_ERROR_OUT_OF_DEVICE_MEMORY

  • VK_ERROR_INVALID_EXTERNAL_HANDLE

  • VK_ERROR_INVALID_OPAQUE_CAPTURE_ADDRESS_KHR

See Also

Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

Copyright 2014-2021 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0