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More documentation. Especially added new section "Finding out if memory is mappable".

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Adam Sawicki 2018-03-02 13:05:39 +01:00
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@ -66,11 +66,13 @@ $(function() {
<div class="title">Custom memory pools </div> </div>
</div><!--header-->
<div class="contents">
<div class="textblock"><p>The library automatically creates and manages default memory pool for each memory type available on the device. A pool contains a number of <code>VkDeviceMemory</code> blocks. You can create custom pool and allocate memory out of it. It can be useful if you want to:</p>
<div class="textblock"><p>A memory pool contains a number of <code>VkDeviceMemory</code> blocks. The library automatically creates and manages default pool for each memory type available on the device. Default memory pool automatically grows in size. Size of allocated blocks is also variable and managed automatically.</p>
<p>You can create custom pool and allocate memory out of it. It can be useful if you want to:</p>
<ul>
<li>Keep certain kind of allocations separate from others.</li>
<li>Enforce particular size of Vulkan memory blocks.</li>
<li>Enforce particular, fixed size of Vulkan memory blocks.</li>
<li>Limit maximum amount of Vulkan memory allocated for that pool.</li>
<li>Reserve minimum or fixed amount of Vulkan memory always preallocated for that pool.</li>
</ul>
<p>To use custom memory pools:</p>
<ol type="1">
@ -79,7 +81,7 @@ $(function() {
<li>When making an allocation, set <a class="el" href="struct_vma_allocation_create_info.html#a6272c0555cfd1fe28bff1afeb6190150" title="Pool that this allocation should be created in. ">VmaAllocationCreateInfo::pool</a> to this handle. You don't need to specify any other parameters of this structure, like usage.</li>
</ol>
<p>Example:</p>
<div class="fragment"><div class="line"><span class="comment">// Create a pool that could have at most 2 blocks, 128 MiB each.</span></div><div class="line"><a class="code" href="struct_vma_pool_create_info.html">VmaPoolCreateInfo</a> poolCreateInfo = {};</div><div class="line">poolCreateInfo.<a class="code" href="struct_vma_pool_create_info.html#a596fa76b685d3f1f688f84a709a5b319">memoryTypeIndex</a> = ...</div><div class="line">poolCreateInfo.blockSize = 128ull * 1024 * 1024;</div><div class="line">poolCreateInfo.<a class="code" href="struct_vma_pool_create_info.html#ae41142f2834fcdc82baa4883c187b75c">maxBlockCount</a> = 2;</div><div class="line"></div><div class="line">VmaPool pool;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a5c8770ded7c59c8caac6de0c2cb00b50">vmaCreatePool</a>(allocator, &amp;poolCreateInfo, &amp;pool);</div><div class="line"></div><div class="line"><span class="comment">// Allocate a buffer out of it.</span></div><div class="line">VkBufferCreateInfo bufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div><div class="line">bufCreateInfo.size = 1024;</div><div class="line">bufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;</div><div class="line"></div><div class="line"><a class="code" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocCreateInfo = {};</div><div class="line">allocCreateInfo.<a class="code" href="struct_vma_allocation_create_info.html#a6272c0555cfd1fe28bff1afeb6190150">pool</a> = pool;</div><div class="line"></div><div class="line">VkBuffer buf;</div><div class="line">VmaAllocation alloc;</div><div class="line"><a class="code" href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufCreateInfo, &amp;allocCreateInfo, &amp;buf, &amp;alloc, &amp;allocInfo);</div></div><!-- fragment --><p>You have to free all allocations made from this pool before destroying it.</p>
<div class="fragment"><div class="line"><span class="comment">// Create a pool that can have at most 2 blocks, 128 MiB each.</span></div><div class="line"><a class="code" href="struct_vma_pool_create_info.html">VmaPoolCreateInfo</a> poolCreateInfo = {};</div><div class="line">poolCreateInfo.<a class="code" href="struct_vma_pool_create_info.html#a596fa76b685d3f1f688f84a709a5b319">memoryTypeIndex</a> = ...</div><div class="line">poolCreateInfo.blockSize = 128ull * 1024 * 1024;</div><div class="line">poolCreateInfo.<a class="code" href="struct_vma_pool_create_info.html#ae41142f2834fcdc82baa4883c187b75c">maxBlockCount</a> = 2;</div><div class="line"></div><div class="line">VmaPool pool;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a5c8770ded7c59c8caac6de0c2cb00b50">vmaCreatePool</a>(allocator, &amp;poolCreateInfo, &amp;pool);</div><div class="line"></div><div class="line"><span class="comment">// Allocate a buffer out of it.</span></div><div class="line">VkBufferCreateInfo bufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div><div class="line">bufCreateInfo.size = 1024;</div><div class="line">bufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;</div><div class="line"></div><div class="line"><a class="code" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocCreateInfo = {};</div><div class="line">allocCreateInfo.<a class="code" href="struct_vma_allocation_create_info.html#a6272c0555cfd1fe28bff1afeb6190150">pool</a> = pool;</div><div class="line"></div><div class="line">VkBuffer buf;</div><div class="line">VmaAllocation alloc;</div><div class="line"><a class="code" href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufCreateInfo, &amp;allocCreateInfo, &amp;buf, &amp;alloc, &amp;allocInfo);</div></div><!-- fragment --><p>You have to free all allocations made from this pool before destroying it.</p>
<div class="fragment"><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a0d9f4e4ba5bf9aab1f1c746387753d77">vmaDestroyBuffer</a>(allocator, buf, alloc);</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a5485779c8f1948238fc4e92232fa65e1">vmaDestroyPool</a>(allocator, pool);</div></div><!-- fragment --><h1><a class="anchor" id="custom_memory_pools_MemTypeIndex"></a>
Choosing memory type index</h1>
<p>When creating a pool, you must explicitly specify memory type index. To find the one suitable for your buffers or images, you can use code similar to the following:</p>

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@ -82,8 +82,12 @@ Persistently mapped memory</h1>
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 using function <code>vkvkInvalidateMappedMemoryRanges()</code> and flush cache after writing to mapped pointer using function <code>vkFlushMappedMemoryRanges()</code>. Example:</p>
<div class="fragment"><div class="line">memcpy(allocInfo.<a class="code" href="struct_vma_allocation_info.html#a5eeffbe2d2f30f53370ff14aefbadbe2">pMappedData</a>, &amp;constantBufferData, <span class="keyword">sizeof</span>(constantBufferData));</div><div class="line"></div><div class="line">VkMemoryPropertyFlags memFlags;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a8701444752eb5de4464adb5a2b514bca">vmaGetMemoryTypeProperties</a>(allocator, allocInfo.<a class="code" href="struct_vma_allocation_info.html#a7f6b0aa58c135e488e6b40a388dad9d5">memoryType</a>, &amp;memFlags);</div><div class="line"><span class="keywordflow">if</span>((memFlags &amp; VK_MEMORY_PROPERTY_HOST_COHERENT_BIT) == 0)</div><div class="line">{</div><div class="line"> VkMappedMemoryRange memRange = { VK_STRUCTURE_TYPE_MAPPED_MEMORY_RANGE };</div><div class="line"> memRange.memory = allocInfo.<a class="code" href="struct_vma_allocation_info.html#ae0bfb7dfdf79a76ffefc9a94677a2f67">deviceMemory</a>;</div><div class="line"> memRange.offset = allocInfo.<a class="code" href="struct_vma_allocation_info.html#a4a3c732388dbdc7a23f9365b00825268">offset</a>;</div><div class="line"> memRange.size = allocInfo.<a class="code" href="struct_vma_allocation_info.html#aac76d113a6a5ccbb09fea00fb25fd18f">size</a>;</div><div class="line"> vkFlushMappedMemoryRanges(device, 1, &amp;memRange);</div><div class="line">}</div></div><!-- fragment --><p>Please note that memory allocated with <code>VMA_MEMORY_USAGE_CPU_ONLY</code> is guaranteed to be host coherent.</p>
<p>Also, Windows drivers from all 3 PC GPU vendors (AMD, Intel, NVIDIA) currently provide <code>VK_MEMORY_PROPERTY_HOST_COHERENT_BIT</code> flag on all memory types that are <code>VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT</code>, so on this platform you may not need to bother. </p>
</div></div><!-- contents -->
<p>Also, Windows drivers from all 3 PC GPU vendors (AMD, Intel, NVIDIA) currently provide <code>VK_MEMORY_PROPERTY_HOST_COHERENT_BIT</code> flag on all memory types that are <code>VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT</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>
<p>You can detect this case and map such allocation to access its memory on CPU directly, instead of launching a transfer operation. You can even use <code>VMA_ALLOCATION_CREATE_MAPPED_BIT</code> flag while creating allocations that are not necessarily <code>HOST_VISIBLE</code> (e.g. using <code>VMA_MEMORY_USAGE_GPU_ONLY</code>). If the allocation ends up in memory type that is <code>HOST_VISIBLE</code>, it will be persistently mapped and you can use it directly. If not, the flag is just ignored. Example:</p>
<div class="fragment"><div class="line">VkBufferCreateInfo bufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div><div class="line">bufCreateInfo.size = <span class="keyword">sizeof</span>(ConstantBuffer);</div><div class="line">bufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;</div><div class="line"></div><div class="line"><a class="code" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocCreateInfo = {};</div><div class="line">allocCreateInfo.<a class="code" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a> = <a class="code" href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7">VMA_MEMORY_USAGE_GPU_ONLY</a>;</div><div class="line">allocCreateInfo.<a class="code" href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">flags</a> = <a class="code" href="vk__mem__alloc_8h.html#ad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f">VMA_ALLOCATION_CREATE_MAPPED_BIT</a>;</div><div class="line"></div><div class="line">VkBuffer buf;</div><div class="line">VmaAllocation alloc;</div><div class="line"><a class="code" href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufCreateInfo, &amp;allocCreateInfo, &amp;buf, &amp;alloc, &amp;allocInfo);</div><div class="line"></div><div class="line"><span class="keywordflow">if</span>(allocInfo.<a class="code" href="struct_vma_allocation_info.html#adc507656149c04de7ed95d0042ba2a13">pUserData</a> != <span class="keyword">nullptr</span>)</div><div class="line">{</div><div class="line"> <span class="comment">// Allocation ended up in mappable memory.</span></div><div class="line"> <span class="comment">// It&#39;s persistently mapped. You can access it directly.</span></div><div class="line"> memcpy(allocInfo.<a class="code" href="struct_vma_allocation_info.html#a5eeffbe2d2f30f53370ff14aefbadbe2">pMappedData</a>, &amp;constantBufferData, <span class="keyword">sizeof</span>(constantBufferData));</div><div class="line">}</div><div class="line"><span class="keywordflow">else</span></div><div class="line">{</div><div class="line"> <span class="comment">// Allocation ended up in non-mappable memory.</span></div><div class="line"> <span class="comment">// You need to create CPU-side copy in VMA_MEMORY_USAGE_CPU_ONLY and make a transfer.</span></div><div class="line">}</div></div><!-- fragment --> </div></div><!-- contents -->
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@ -71,7 +71,7 @@ $(function() {
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-attribs"></a>
Public Attributes</h2></td></tr>
<tr class="memitem:add09658ac14fe290ace25470ddd6d41b"><td class="memItemLeft" align="right" valign="top"><a class="el" href="vk__mem__alloc_8h.html#a5225e5e11f8376f6a31a1791f3d6e817">VmaAllocationCreateFlags</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">flags</a></td></tr>
<tr class="memdesc:add09658ac14fe290ace25470ddd6d41b"><td class="mdescLeft">&#160;</td><td class="mdescRight">Use VmaAllocationCreateFlagBits enum. <a href="#add09658ac14fe290ace25470ddd6d41b">More...</a><br /></td></tr>
<tr class="memdesc:add09658ac14fe290ace25470ddd6d41b"><td class="mdescLeft">&#160;</td><td class="mdescRight">Use <a class="el" href="vk__mem__alloc_8h.html#abf6bf6748c7a9fe7ce5b7835c0f56af4" title="Flags to be passed as VmaAllocationCreateInfo::flags. ">VmaAllocationCreateFlagBits</a> enum. <a href="#add09658ac14fe290ace25470ddd6d41b">More...</a><br /></td></tr>
<tr class="separator:add09658ac14fe290ace25470ddd6d41b"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:accb8b06b1f677d858cb9af20705fa910"><td class="memItemLeft" align="right" valign="top"><a class="el" href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305cc">VmaMemoryUsage</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a></td></tr>
<tr class="memdesc:accb8b06b1f677d858cb9af20705fa910"><td class="mdescLeft">&#160;</td><td class="mdescRight">Intended usage of memory. <a href="#accb8b06b1f677d858cb9af20705fa910">More...</a><br /></td></tr>
@ -105,7 +105,7 @@ Public Attributes</h2></td></tr>
</table>
</div><div class="memdoc">
<p>Use VmaAllocationCreateFlagBits enum. </p>
<p>Use <a class="el" href="vk__mem__alloc_8h.html#abf6bf6748c7a9fe7ce5b7835c0f56af4" title="Flags to be passed as VmaAllocationCreateInfo::flags. ">VmaAllocationCreateFlagBits</a> enum. </p>
</div>
</div>

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@ -1295,8 +1295,9 @@ Functions</h2></td></tr>
<p>The function also frees empty <code>VkDeviceMemory</code> blocks.</p>
<p>After allocation has been moved, its <a class="el" href="struct_vma_allocation_info.html#ae0bfb7dfdf79a76ffefc9a94677a2f67" title="Handle to Vulkan memory object. ">VmaAllocationInfo::deviceMemory</a> and/or <a class="el" href="struct_vma_allocation_info.html#a4a3c732388dbdc7a23f9365b00825268" title="Offset into deviceMemory object to the beginning of this allocation, in bytes. (deviceMemory, offset) pair is unique to this allocation. ">VmaAllocationInfo::offset</a> changes. You must query them again using <a class="el" href="vk__mem__alloc_8h.html#a86dd08aba8633bfa4ad0df2e76481d8b" title="Returns current information about specified allocation. ">vmaGetAllocationInfo()</a> if you need them.</p>
<p>If an allocation has been moved, data in memory is copied to new place automatically, but if it was bound to a buffer or an image, you must destroy that object yourself, create new one and bind it to the new memory pointed by the allocation. You must use <code>vkDestroyBuffer()</code>, <code>vkDestroyImage()</code>, <code>vkCreateBuffer()</code>, <code>vkCreateImage()</code> for that purpose and NOT <a class="el" href="vk__mem__alloc_8h.html#a0d9f4e4ba5bf9aab1f1c746387753d77" title="Destroys Vulkan buffer and frees allocated memory. ">vmaDestroyBuffer()</a>, <a class="el" href="vk__mem__alloc_8h.html#ae50d2cb3b4a3bfd4dd40987234e50e7e" title="Destroys Vulkan image and frees allocated memory. ">vmaDestroyImage()</a>, <a class="el" href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer()</a>, <a class="el" href="vk__mem__alloc_8h.html#a02a94f25679275851a53e82eacbcfc73" title="Function similar to vmaCreateBuffer(). ">vmaCreateImage()</a>! Example:</p>
<div class="fragment"><div class="line">VkDevice device = ...;</div><div class="line">VmaAllocator allocator = ...;</div><div class="line">std::vector&lt;VkBuffer&gt; buffers = ...;</div><div class="line">std::vector&lt;VmaAllocation&gt; allocations = ...;</div><div class="line"></div><div class="line">std::vector&lt;VkBool32&gt; allocationsChanged(allocations.size());</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a6aced90fcc7b39882b6654a740a0b9bb">vmaDefragment</a>(allocator, allocations.data(), allocations.size(), allocationsChanged.data(), <span class="keyword">nullptr</span>, <span class="keyword">nullptr</span>);</div><div class="line"></div><div class="line"><span class="keywordflow">for</span>(<span class="keywordtype">size_t</span> i = 0; i &lt; allocations.size(); ++i)</div><div class="line">{</div><div class="line"> <span class="keywordflow">if</span>(allocationsChanged[i])</div><div class="line"> {</div><div class="line"> <a class="code" href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><div class="line"> <a class="code" href="vk__mem__alloc_8h.html#a86dd08aba8633bfa4ad0df2e76481d8b">vmaGetAllocationInfo</a>(allocator, allocations[i], &amp;allocInfo);</div><div class="line"></div><div class="line"> vkDestroyBuffer(device, buffers[i], <span class="keyword">nullptr</span>);</div><div class="line"></div><div class="line"> VkBufferCreateInfo bufferInfo = ...;</div><div class="line"> vkCreateBuffer(device, &amp;bufferInfo, <span class="keyword">nullptr</span>, &amp;buffers[i]);</div><div class="line"> </div><div class="line"> <span class="comment">// You can make dummy call to vkGetBufferMemoryRequirements here to silence validation layer warning.</span></div><div class="line"> </div><div class="line"> vkBindBufferMemory(device, buffers[i], allocInfo.<a class="code" href="struct_vma_allocation_info.html#ae0bfb7dfdf79a76ffefc9a94677a2f67">deviceMemory</a>, allocInfo.<a class="code" href="struct_vma_allocation_info.html#a4a3c732388dbdc7a23f9365b00825268">offset</a>);</div><div class="line"> }</div><div class="line">}</div></div><!-- fragment --><p>Warning! This function is not correct according to Vulkan specification. Use it at your own risk. That's becuase Vulkan doesn't guarantee that memory requirements (size and alignment) for a new buffer or image are consistent. They may be different even for subsequent calls with the same parameters. It really does happen on some platforms, especially with images.</p>
<p>This function may be time-consuming, so you shouldn't call it too often (like every frame or after every resource creation/destruction), but rater you can call it on special occasions (like when reloading a game level, when you just destroyed a lot of objects). </p>
<div class="fragment"><div class="line">VkDevice device = ...;</div><div class="line">VmaAllocator allocator = ...;</div><div class="line">std::vector&lt;VkBuffer&gt; buffers = ...;</div><div class="line">std::vector&lt;VmaAllocation&gt; allocations = ...;</div><div class="line"></div><div class="line">std::vector&lt;VkBool32&gt; allocationsChanged(allocations.size());</div><div class="line"><a class="code" href="vk__mem__alloc_8h.html#a6aced90fcc7b39882b6654a740a0b9bb">vmaDefragment</a>(allocator, allocations.data(), allocations.size(), allocationsChanged.data(), <span class="keyword">nullptr</span>, <span class="keyword">nullptr</span>);</div><div class="line"></div><div class="line"><span class="keywordflow">for</span>(<span class="keywordtype">size_t</span> i = 0; i &lt; allocations.size(); ++i)</div><div class="line">{</div><div class="line"> <span class="keywordflow">if</span>(allocationsChanged[i])</div><div class="line"> {</div><div class="line"> <a class="code" href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><div class="line"> <a class="code" href="vk__mem__alloc_8h.html#a86dd08aba8633bfa4ad0df2e76481d8b">vmaGetAllocationInfo</a>(allocator, allocations[i], &amp;allocInfo);</div><div class="line"></div><div class="line"> vkDestroyBuffer(device, buffers[i], <span class="keyword">nullptr</span>);</div><div class="line"></div><div class="line"> VkBufferCreateInfo bufferInfo = ...;</div><div class="line"> vkCreateBuffer(device, &amp;bufferInfo, <span class="keyword">nullptr</span>, &amp;buffers[i]);</div><div class="line"> </div><div class="line"> <span class="comment">// You can make dummy call to vkGetBufferMemoryRequirements here to silence validation layer warning.</span></div><div class="line"> </div><div class="line"> vkBindBufferMemory(device, buffers[i], allocInfo.<a class="code" href="struct_vma_allocation_info.html#ae0bfb7dfdf79a76ffefc9a94677a2f67">deviceMemory</a>, allocInfo.<a class="code" href="struct_vma_allocation_info.html#a4a3c732388dbdc7a23f9365b00825268">offset</a>);</div><div class="line"> }</div><div class="line">}</div></div><!-- fragment --><p>Note: Please don't expect memory to be fully compacted after this call. Algorithms inside are based on some heuristics that try to maximize number of Vulkan memory blocks to make totally empty to release them, as well as to maximimze continuous empty space inside remaining blocks, while minimizing the number and size of data that needs to be moved. Some fragmentation still remains after this call. This is normal.</p>
<p>Warning: This function is not 100% correct according to Vulkan specification. Use it at your own risk. That's because Vulkan doesn't guarantee that memory requirements (size and alignment) for a new buffer or image are consistent. They may be different even for subsequent calls with the same parameters. It really does happen on some platforms, especially with images.</p>
<p>Warning: This function may be time-consuming, so you shouldn't call it too often (like every frame or after every resource creation/destruction). You can call it on special occasions (like when reloading a game level or when you just destroyed a lot of objects). </p>
</div>
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@ -353,17 +353,63 @@ Also, Windows drivers from all 3 PC GPU vendors (AMD, Intel, NVIDIA)
currently provide `VK_MEMORY_PROPERTY_HOST_COHERENT_BIT` flag on all memory types that are
`VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT`, so on this platform you may not need to bother.
\section memory_mapping_finding_if_memory_mappable Finding out if memory is mappable
It may happen that your allocation ends up in memory that is `HOST_VISIBLE` (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.
You can detect this case and map such allocation to access its memory on CPU directly,
instead of launching a transfer operation.
You can even use `VMA_ALLOCATION_CREATE_MAPPED_BIT` flag while creating allocations
that are not necessarily `HOST_VISIBLE` (e.g. using `VMA_MEMORY_USAGE_GPU_ONLY`).
If the allocation ends up in memory type that is `HOST_VISIBLE`, it will be persistently mapped and you can use it directly.
If not, the flag is just ignored.
Example:
\code
VkBufferCreateInfo bufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };
bufCreateInfo.size = sizeof(ConstantBuffer);
bufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;
VmaAllocationCreateInfo allocCreateInfo = {};
allocCreateInfo.usage = VMA_MEMORY_USAGE_GPU_ONLY;
allocCreateInfo.flags = VMA_ALLOCATION_CREATE_MAPPED_BIT;
VkBuffer buf;
VmaAllocation alloc;
VmaAllocationInfo allocInfo;
vmaCreateBuffer(allocator, &bufCreateInfo, &allocCreateInfo, &buf, &alloc, &allocInfo);
if(allocInfo.pUserData != nullptr)
{
// Allocation ended up in mappable memory.
// It's persistently mapped. You can access it directly.
memcpy(allocInfo.pMappedData, &constantBufferData, sizeof(constantBufferData));
}
else
{
// Allocation ended up in non-mappable memory.
// You need to create CPU-side copy in VMA_MEMORY_USAGE_CPU_ONLY and make a transfer.
}
\endcode
\page custom_memory_pools Custom memory pools
The library automatically creates and manages default memory pool for each
memory type available on the device. A pool contains a number of
`VkDeviceMemory` blocks. You can create custom pool and allocate memory out of
it. It can be useful if you want to:
A memory pool contains a number of `VkDeviceMemory` blocks.
The library automatically creates and manages default pool for each memory type available on the device.
Default memory pool automatically grows in size.
Size of allocated blocks is also variable and managed automatically.
You can create custom pool and allocate memory out of it.
It can be useful if you want to:
- Keep certain kind of allocations separate from others.
- Enforce particular size of Vulkan memory blocks.
- Enforce particular, fixed size of Vulkan memory blocks.
- Limit maximum amount of Vulkan memory allocated for that pool.
- Reserve minimum or fixed amount of Vulkan memory always preallocated for that pool.
To use custom memory pools:
@ -375,7 +421,7 @@ To use custom memory pools:
Example:
\code
// Create a pool that could have at most 2 blocks, 128 MiB each.
// Create a pool that can have at most 2 blocks, 128 MiB each.
VmaPoolCreateInfo poolCreateInfo = {};
poolCreateInfo.memoryTypeIndex = ...
poolCreateInfo.blockSize = 128ull * 1024 * 1024;
@ -1156,7 +1202,7 @@ typedef VkFlags VmaAllocationCreateFlags;
typedef struct VmaAllocationCreateInfo
{
/// Use VmaAllocationCreateFlagBits enum.
/// Use #VmaAllocationCreateFlagBits enum.
VmaAllocationCreateFlags flags;
/** \brief Intended usage of memory.
@ -1612,16 +1658,22 @@ for(size_t i = 0; i < allocations.size(); ++i)
}
\endcode
Warning! This function is not correct according to Vulkan specification. Use it
at your own risk. That's becuase Vulkan doesn't guarantee that memory
Note: Please don't expect memory to be fully compacted after this call.
Algorithms inside are based on some heuristics that try to maximize number of Vulkan
memory blocks to make totally empty to release them, as well as to maximimze continuous
empty space inside remaining blocks, while minimizing the number and size of data that
needs to be moved. Some fragmentation still remains after this call. This is normal.
Warning: This function is not 100% correct according to Vulkan specification. Use it
at your own risk. That's because Vulkan doesn't guarantee that memory
requirements (size and alignment) for a new buffer or image are consistent. They
may be different even for subsequent calls with the same parameters. It really
does happen on some platforms, especially with images.
This function may be time-consuming, so you shouldn't call it too often (like
every frame or after every resource creation/destruction), but rater you can
call it on special occasions (like when reloading a game level, when you just
destroyed a lot of objects).
Warning: This function may be time-consuming, so you shouldn't call it too often
(like every frame or after every resource creation/destruction).
You can call it on special occasions (like when reloading a game level or
when you just destroyed a lot of objects).
*/
VkResult vmaDefragment(
VmaAllocator allocator,