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clarify documentation regarding limitations of defragmentation

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#59
This commit is contained in:
Adam Sawicki 2019-04-17 11:53:02 +02:00
parent f48896d164
commit 672f7c8e94
4 changed files with 171 additions and 159 deletions
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24
src/vk_mem_alloc.h
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@ -907,19 +907,22 @@ in function vmaDefragmentationBegin().
\section defragmentation_additional_notes Additional notes
While using defragmentation, you may experience validation layer warnings, which you just need to ignore.
See [Validation layer warnings](@ref general_considerations_validation_layer_warnings).
It is only legal to defragment allocations bound to:
If you defragment allocations bound to images, these images should be created with
`VK_IMAGE_CREATE_ALIAS_BIT` flag, to make sure that new image created with same
parameters and pointing to data copied to another memory region will interpret
its contents consistently. Otherwise you may experience corrupted data on some
implementations, e.g. due to different pixel swizzling used internally by the graphics driver.
- buffers
- images created with `VK_IMAGE_CREATE_ALIAS_BIT`, `VK_IMAGE_TILING_LINEAR`, and
being currently in `VK_IMAGE_LAYOUT_GENERAL` or `VK_IMAGE_LAYOUT_PREINITIALIZED`.
Defragmentation of images created with `VK_IMAGE_TILING_OPTIMAL` or in any other
layout may give undefined results.
If you defragment allocations bound to images, new images to be bound to new
memory region after defragmentation should be created with `VK_IMAGE_LAYOUT_PREINITIALIZED`
and then transitioned to their original layout from before defragmentation using
an image memory barrier.
and then transitioned to their original layout from before defragmentation if
needed using an image memory barrier.
While using defragmentation, you may experience validation layer warnings, which you just need to ignore.
See [Validation layer warnings](@ref general_considerations_validation_layer_warnings).
Please don't expect memory to be fully compacted after defragmentation.
Algorithms inside are based on some heuristics that try to maximize number of Vulkan
@ -2937,6 +2940,9 @@ Warning! Between the call to vmaDefragmentationBegin() and vmaDefragmentationEnd
They become valid after call to vmaDefragmentationEnd().
- If `pInfo->commandBuffer` is not null, you must submit that command buffer
and make sure it finished execution before calling vmaDefragmentationEnd().
For more information and important limitations regarding defragmentation, see documentation chapter:
[Defragmentation](@ref defragmentation).
*/
VkResult vmaDefragmentationBegin(
VmaAllocator allocator,