vkFlushMappedMemoryRanges

vkFlushMappedMemoryRanges is a Vulkan API function used to flush host writes to mapped device memory so that the device can observe those changes. It operates on memory that has been mapped into the host address space and uses an array of VkMappedMemoryRange structures to specify which parts of which memory objects should be flushed.

In Vulkan, memory types can be host-visible but either coherent or non-coherent. If a memory type does not have the VK_MEMORY_PROPERTY_HOST_COHERENT_BIT property, host writes performed through a mapped pointer may remain cached and not be visible to the device until a flush is performed. vkFlushMappedMemoryRanges ensures that writes in the specified ranges are made visible to the device. Conversely, if the memory is host-coherent, flushing is not required and the operation may be a no-op.

Usage involves providing the device, the number of memory ranges, and a pointer to an array of VkMappedMemoryRange structures. Each range describes a VkDeviceMemory object, an offset, and a size to flush. The function can be called with multiple ranges in a single call, enabling selective flushing of only updated regions. After host writes to mapped memory, you would typically call this function before the device reads or uses the data.

The function returns a VkResult, with VK_SUCCESS indicating success. Possible error codes include VK_ERROR_MEMORY_MAP_FAILED if the flush could not be completed. For memory that is not host-visible or already coherent, the call may be a no-op or return an appropriate error.

Related functionality includes vkInvalidateMappedMemoryRanges, which invalidates host caches to reflect device writes back to host memory.