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Clarify documentation in regards to cache flush/invalidate in few places

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See #91, thanks @ROTARTSI82 !
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Adam Sawicki 2019-12-02 13:42:25 +01:00
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@ -115,11 +115,11 @@ Persistently mapped memory</h1>
<li>Keeping many large memory blocks mapped may impact performance or stability of some debugging tools.</li>
</ul>
<h1><a class="anchor" id="memory_mapping_cache_control"></a>
Cache control</h1>
<p>Memory in Vulkan doesn't need to be unmapped before using it on GPU, but unless a memory types has <code>VK_MEMORY_PROPERTY_HOST_COHERENT_BIT</code> flag set, you need to manually invalidate cache before reading of mapped pointer and flush cache after writing to mapped pointer. Vulkan provides following functions for this purpose <code>vkFlushMappedMemoryRanges()</code>, <code>vkInvalidateMappedMemoryRanges()</code>, but this library provides more convenient functions that refer to given allocation object: <a class="el" href="vk__mem__alloc_8h.html#abc34ee6f021f459aff885f3758c435de" title="Flushes memory of given allocation.">vmaFlushAllocation()</a>, <a class="el" href="vk__mem__alloc_8h.html#a0d0eb0c1102268fa9a476d12ecbe4006" title="Invalidates memory of given allocation.">vmaInvalidateAllocation()</a>.</p>
Cache flush and invalidate</h1>
<p>Memory in Vulkan doesn't need to be unmapped before using it on GPU, but unless a memory types has <code>VK_MEMORY_PROPERTY_HOST_COHERENT_BIT</code> flag set, you need to manually <b>invalidate</b> cache before reading of mapped pointer and <b>flush</b> cache after writing to mapped pointer. Map/unmap operations don't do that automatically. Vulkan provides following functions for this purpose <code>vkFlushMappedMemoryRanges()</code>, <code>vkInvalidateMappedMemoryRanges()</code>, but this library provides more convenient functions that refer to given allocation object: <a class="el" href="vk__mem__alloc_8h.html#abc34ee6f021f459aff885f3758c435de" title="Flushes memory of given allocation.">vmaFlushAllocation()</a>, <a class="el" href="vk__mem__alloc_8h.html#a0d0eb0c1102268fa9a476d12ecbe4006" title="Invalidates memory of given allocation.">vmaInvalidateAllocation()</a>.</p>
<p>Regions of memory specified for flush/invalidate must be aligned to <code>VkPhysicalDeviceLimits::nonCoherentAtomSize</code>. This is automatically ensured by the library. In any memory type that is <code>HOST_VISIBLE</code> but not <code>HOST_COHERENT</code>, all allocations within blocks are aligned to this value, so their offsets are always multiply of <code>nonCoherentAtomSize</code> and two different allocations never share same "line" of this size.</p>
<p>Please note that memory allocated with <a class="el" href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305cca40bdf4cddeffeb12f43d45ca1286e0a5">VMA_MEMORY_USAGE_CPU_ONLY</a> is guaranteed to be <code>HOST_COHERENT</code>.</p>
<p>Also, Windows drivers from all 3 PC GPU vendors (AMD, Intel, NVIDIA) currently provide <code>HOST_COHERENT</code> flag on all memory types that are <code>HOST_VISIBLE</code>, so on this platform you may not need to bother.</p>
<p>Also, Windows drivers from all 3 <b>PC</b> GPU vendors (AMD, Intel, NVIDIA) currently provide <code>HOST_COHERENT</code> flag on all memory types that are <code>HOST_VISIBLE</code>, so on this platform you may not need to bother.</p>
<h1><a class="anchor" id="memory_mapping_finding_if_memory_mappable"></a>
Finding out if memory is mappable</h1>
<p>It may happen that your allocation ends up in memory that is <code>HOST_VISIBLE</code> (available for mapping) despite it wasn't explicitly requested. For example, application may work on integrated graphics with unified memory (like Intel) or allocation from video memory might have failed, so the library chose system memory as fallback.</p>
@ -182,20 +182,20 @@ Finding out if memory is mappable</h1>
<div class="ttc" id="avk__mem__alloc_8h_html_a9bc268595cb33f6ec4d519cfce81ff45"><div class="ttname"><a href="vk__mem__alloc_8h.html#a9bc268595cb33f6ec4d519cfce81ff45">vmaUnmapMemory</a></div><div class="ttdeci">void vmaUnmapMemory(VmaAllocator allocator, VmaAllocation allocation)</div><div class="ttdoc">Unmaps memory represented by given allocation, mapped previously using vmaMapMemory().</div></div>
<div class="ttc" id="astruct_vma_allocator_html"><div class="ttname"><a href="struct_vma_allocator.html">VmaAllocator</a></div><div class="ttdoc">Represents main object of this library initialized.</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_a8701444752eb5de4464adb5a2b514bca"><div class="ttname"><a href="vk__mem__alloc_8h.html#a8701444752eb5de4464adb5a2b514bca">vmaGetMemoryTypeProperties</a></div><div class="ttdeci">void vmaGetMemoryTypeProperties(VmaAllocator allocator, uint32_t memoryTypeIndex, VkMemoryPropertyFlags *pFlags)</div><div class="ttdoc">Given Memory Type Index, returns Property Flags of this memory type.</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_aa5846affa1e9da3800e3e78fae2305cca40bdf4cddeffeb12f43d45ca1286e0a5"><div class="ttname"><a href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305cca40bdf4cddeffeb12f43d45ca1286e0a5">VMA_MEMORY_USAGE_CPU_ONLY</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2291</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_aa5846affa1e9da3800e3e78fae2305cca40bdf4cddeffeb12f43d45ca1286e0a5"><div class="ttname"><a href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305cca40bdf4cddeffeb12f43d45ca1286e0a5">VMA_MEMORY_USAGE_CPU_ONLY</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2292</div></div>
<div class="ttc" id="astruct_vma_allocation_html"><div class="ttname"><a href="struct_vma_allocation.html">VmaAllocation</a></div><div class="ttdoc">Represents single memory allocation.</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7"><div class="ttname"><a href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7">VMA_MEMORY_USAGE_GPU_ONLY</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2281</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7"><div class="ttname"><a href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7">VMA_MEMORY_USAGE_GPU_ONLY</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2282</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_ad5bd1243512d099706de88168992f069"><div class="ttname"><a href="vk__mem__alloc_8h.html#ad5bd1243512d099706de88168992f069">vmaMapMemory</a></div><div class="ttdeci">VkResult vmaMapMemory(VmaAllocator allocator, VmaAllocation allocation, void **ppData)</div><div class="ttdoc">Maps memory represented by given allocation and returns pointer to it.</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_a5eeffbe2d2f30f53370ff14aefbadbe2"><div class="ttname"><a href="struct_vma_allocation_info.html#a5eeffbe2d2f30f53370ff14aefbadbe2">VmaAllocationInfo::pMappedData</a></div><div class="ttdeci">void * pMappedData</div><div class="ttdoc">Pointer to the beginning of this allocation as mapped data.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2809</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_accb8b06b1f677d858cb9af20705fa910"><div class="ttname"><a href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">VmaAllocationCreateInfo::usage</a></div><div class="ttdeci">VmaMemoryUsage usage</div><div class="ttdoc">Intended usage of memory.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2447</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_adc507656149c04de7ed95d0042ba2a13"><div class="ttname"><a href="struct_vma_allocation_info.html#adc507656149c04de7ed95d0042ba2a13">VmaAllocationInfo::pUserData</a></div><div class="ttdeci">void * pUserData</div><div class="ttdoc">Custom general-purpose pointer that was passed as VmaAllocationCreateInfo::pUserData or set using vma...</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2814</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_a5eeffbe2d2f30f53370ff14aefbadbe2"><div class="ttname"><a href="struct_vma_allocation_info.html#a5eeffbe2d2f30f53370ff14aefbadbe2">VmaAllocationInfo::pMappedData</a></div><div class="ttdeci">void * pMappedData</div><div class="ttdoc">Pointer to the beginning of this allocation as mapped data.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2810</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_accb8b06b1f677d858cb9af20705fa910"><div class="ttname"><a href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">VmaAllocationCreateInfo::usage</a></div><div class="ttdeci">VmaMemoryUsage usage</div><div class="ttdoc">Intended usage of memory.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2448</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_adc507656149c04de7ed95d0042ba2a13"><div class="ttname"><a href="struct_vma_allocation_info.html#adc507656149c04de7ed95d0042ba2a13">VmaAllocationInfo::pUserData</a></div><div class="ttdeci">void * pUserData</div><div class="ttdoc">Custom general-purpose pointer that was passed as VmaAllocationCreateInfo::pUserData or set using vma...</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2815</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_ac72ee55598617e8eecca384e746bab51"><div class="ttname"><a href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a></div><div class="ttdeci">VkResult vmaCreateBuffer(VmaAllocator allocator, const VkBufferCreateInfo *pBufferCreateInfo, const VmaAllocationCreateInfo *pAllocationCreateInfo, VkBuffer *pBuffer, VmaAllocation *pAllocation, VmaAllocationInfo *pAllocationInfo)</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_a7f6b0aa58c135e488e6b40a388dad9d5"><div class="ttname"><a href="struct_vma_allocation_info.html#a7f6b0aa58c135e488e6b40a388dad9d5">VmaAllocationInfo::memoryType</a></div><div class="ttdeci">uint32_t memoryType</div><div class="ttdoc">Memory type index that this allocation was allocated from.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2781</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_ad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f"><div class="ttname"><a href="vk__mem__alloc_8h.html#ad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f">VMA_ALLOCATION_CREATE_MAPPED_BIT</a></div><div class="ttdoc">Set this flag to use a memory that will be persistently mapped and retrieve pointer to it.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2358</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_add09658ac14fe290ace25470ddd6d41b"><div class="ttname"><a href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">VmaAllocationCreateInfo::flags</a></div><div class="ttdeci">VmaAllocationCreateFlags flags</div><div class="ttdoc">Use VmaAllocationCreateFlagBits enum.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2441</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html"><div class="ttname"><a href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2438</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_a7fe8d81a1ad10b2a2faacacee5b15d6d"><div class="ttname"><a href="struct_vma_allocation_create_info.html#a7fe8d81a1ad10b2a2faacacee5b15d6d">VmaAllocationCreateInfo::preferredFlags</a></div><div class="ttdeci">VkMemoryPropertyFlags preferredFlags</div><div class="ttdoc">Flags that preferably should be set in a memory type chosen for an allocation.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2457</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html"><div class="ttname"><a href="struct_vma_allocation_info.html">VmaAllocationInfo</a></div><div class="ttdoc">Parameters of VmaAllocation objects, that can be retrieved using function vmaGetAllocationInfo().</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2776</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html_a7f6b0aa58c135e488e6b40a388dad9d5"><div class="ttname"><a href="struct_vma_allocation_info.html#a7f6b0aa58c135e488e6b40a388dad9d5">VmaAllocationInfo::memoryType</a></div><div class="ttdeci">uint32_t memoryType</div><div class="ttdoc">Memory type index that this allocation was allocated from.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2782</div></div>
<div class="ttc" id="avk__mem__alloc_8h_html_ad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f"><div class="ttname"><a href="vk__mem__alloc_8h.html#ad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f">VMA_ALLOCATION_CREATE_MAPPED_BIT</a></div><div class="ttdoc">Set this flag to use a memory that will be persistently mapped and retrieve pointer to it.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2359</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_add09658ac14fe290ace25470ddd6d41b"><div class="ttname"><a href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">VmaAllocationCreateInfo::flags</a></div><div class="ttdeci">VmaAllocationCreateFlags flags</div><div class="ttdoc">Use VmaAllocationCreateFlagBits enum.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2442</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html"><div class="ttname"><a href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a></div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2439</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_a7fe8d81a1ad10b2a2faacacee5b15d6d"><div class="ttname"><a href="struct_vma_allocation_create_info.html#a7fe8d81a1ad10b2a2faacacee5b15d6d">VmaAllocationCreateInfo::preferredFlags</a></div><div class="ttdeci">VkMemoryPropertyFlags preferredFlags</div><div class="ttdoc">Flags that preferably should be set in a memory type chosen for an allocation.</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2458</div></div>
<div class="ttc" id="astruct_vma_allocation_info_html"><div class="ttname"><a href="struct_vma_allocation_info.html">VmaAllocationInfo</a></div><div class="ttdoc">Parameters of VmaAllocation objects, that can be retrieved using function vmaGetAllocationInfo().</div><div class="ttdef"><b>Definition:</b> vk_mem_alloc.h:2777</div></div>
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