<divclass="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>
<ul>
<li>Keep certain kind of allocations separate from others.</li>
<li>Enforce particular size of Vulkan memory blocks.</li>
<li>Limit maximum amount of Vulkan memory allocated for that pool.</li>
</ul>
<p>To use custom memory pools:</p>
<oltype="1">
<li>Fill <aclass="el"href="struct_vma_pool_create_info.html"title="Describes parameter of created VmaPool. ">VmaPoolCreateInfo</a> structure.</li>
<li>Call <aclass="el"href="vk__mem__alloc_8h.html#a5c8770ded7c59c8caac6de0c2cb00b50"title="Allocates Vulkan device memory and creates VmaPool object. ">vmaCreatePool()</a> to obtain <code>VmaPool</code> handle.</li>
<li>When making an allocation, set <aclass="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>
<divclass="fragment"><divclass="line"><spanclass="comment">// Create a pool that could have at most 2 blocks, 128 MiB each.</span></div><divclass="line"><aclass="code"href="struct_vma_pool_create_info.html">VmaPoolCreateInfo</a> poolCreateInfo = {};</div><divclass="line">poolCreateInfo.<aclass="code"href="struct_vma_pool_create_info.html#a596fa76b685d3f1f688f84a709a5b319">memoryTypeIndex</a> = ...</div><divclass="line">poolCreateInfo.blockSize = 128ull * 1024 * 1024;</div><divclass="line">poolCreateInfo.<aclass="code"href="struct_vma_pool_create_info.html#ae41142f2834fcdc82baa4883c187b75c">maxBlockCount</a> = 2;</div><divclass="line"></div><divclass="line">VmaPool pool;</div><divclass="line"><aclass="code"href="vk__mem__alloc_8h.html#a5c8770ded7c59c8caac6de0c2cb00b50">vmaCreatePool</a>(allocator, &poolCreateInfo, &pool);</div><divclass="line"></div><divclass="line"><spanclass="comment">// Allocate a buffer out of it.</span></div><divclass="line">VkBufferCreateInfo bufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div><divclass="line">bufCreateInfo.size = 1024;</div><divclass="line">bufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;</div><divclass="line"></div><divclass="line"><aclass="code"href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocCreateInfo = {};</div><divclass="line">allocCreateInfo.<aclass="code"href="struct_vma_allocation_create_info.html#a6272c0555cfd1fe28bff1afeb6190150">pool</a> = pool;</div><divclass="line"></div><divclass="line">VkBuffer buf;</div><divclass="line">VmaAllocation alloc;</div><divclass="line"><aclass="code"href="struct_vma_allocation_info.html">VmaAllocationInfo</a> allocInfo;</div><divclass="line"><aclass="code"href="vk__mem__alloc_8h.html#ac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &bufCreateInfo, &allocCreateInfo, &buf, &alloc, &allocInfo);</div></div><!-- fragment --><p>You have to free all allocations made from this pool before destroying it.</p>
<divclass="fragment"><divclass="line"><aclass="code"href="vk__mem__alloc_8h.html#a0d9f4e4ba5bf9aab1f1c746387753d77">vmaDestroyBuffer</a>(allocator, buf, alloc);</div><divclass="line"><aclass="code"href="vk__mem__alloc_8h.html#a5485779c8f1948238fc4e92232fa65e1">vmaDestroyPool</a>(allocator, pool);</div></div><!-- fragment --><h1><aclass="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>
<divclass="fragment"><divclass="line">VkBufferCreateInfo dummyBufCreateInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div><divclass="line">dummyBufCreateInfo.size = 1024; <spanclass="comment">// Whatever.</span></div><divclass="line">dummyBufCreateInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT; <spanclass="comment">// Change if needed.</span></div><divclass="line"></div><divclass="line">VkBuffer dummyBuf;</div><divclass="line">vkCreateBuffer(device, &dummyBufCreateInfo, <spanclass="keyword">nullptr</span>, &dummyBuf);</div><divclass="line"></div><divclass="line">VkMemoryRequirements memReq;</div><divclass="line">vkGetBufferMemoryRequirements(device, dummyBuf, &memReq);</div><divclass="line"></div><divclass="line"><aclass="code"href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocCreateInfo = {};</div><divclass="line">allocCreateInfo.<aclass="code"href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a> = <aclass="code"href="vk__mem__alloc_8h.html#aa5846affa1e9da3800e3e78fae2305ccac6b5dc1432d88647aa4cd456246eadf7">VMA_MEMORY_USAGE_GPU_ONLY</a>; <spanclass="comment">// Change if needed.</span></div><divclass="line"></div><divclass="line">uint32_t memTypeIndex;</div><divclass="line"><aclass="code"href="vk__mem__alloc_8h.html#aef15a94b58fbcb0fe706d5720e84a74a">vmaFindMemoryTypeIndex</a>(allocator, memReq.memoryTypeBits, &allocCreateInfo, &memTypeIndex);</div><divclass="line"></div><divclass="line">vkDestroyBuffer(device, dummyBuf, <spanclass="keyword">nullptr</span>);</div><divclass="line"></div><divclass="line"><aclass="code"href="struct_vma_pool_create_info.html">VmaPoolCreateInfo</a> poolCreateInfo = {};</div><divclass="line">poolCreateInfo.<aclass="code"href="struct_vma_pool_create_info.html#a596fa76b685d3f1f688f84a709a5b319">memoryTypeIndex</a> = memTypeIndex;</div><divclass="line"><spanclass="comment">// ...</span></div></div><!-- fragment --><p>Dummy buffer is needed to query driver for <code>memReq.memoryTypeBits</code>. Memory is never allocated for this buffer. You should fill structures <code>dummyBufCreateInfo</code> and <code>allocCreateInfo</code> with the same parameters as you are going to use for buffers created in your pool. </p>
