vkReallocate

vkReallocate is a utility routine provided by certain Vulkan memory management frameworks to resize an existing device memory allocation. It is not part of the core Vulkan API, but is offered by higher-level libraries or extensions to simplify dynamic memory growth for Vulkan applications.

Overview and behavior: Given a device, an allocation handle and a requested new size, vkReallocate attempts to adjust the allocation's size. If the allocator can accommodate the new size in place, the existing VkDeviceMemory block is retained. Otherwise a new VkDeviceMemory block is allocated with the requested size, data from the old block is copied to the new one, and the old memory is freed. The function returns a new allocation/handle and may provide information about data preservation and required command buffer synchronization. If the original memory was host-visible, a memory copy can be performed by host or by the device via a transfer command, depending on the allocator's design.

Usage and constraints: Reallocation preserves previously stored data when requested. Some allocators support in-place resizing only for certain memory types or alignment constraints. The operation may incur fragmentation and synchronization overhead and is typically not recommended for frequent resizing; instead, reallocate might be used during resource growth phases. Compatibility depends on the allocator's capabilities and the device's memory type constraints.

Relation and alternatives: In core Vulkan, applications typically allocate appropriately sized resources upfront and manage fragmentation through careful resource planning. Third-party allocators like the Vulkan Memory Allocator provide higher-level APIs such as vkReallocate-like routines to manage growth of allocations while maintaining correctness and synchronization.

See also: VkDeviceMemory, Vulkan, memory allocator.