Preallocate a pool of descriptors by default.

Enable MVKConfiguration::preallocateDescriptors and
MVK_CONFIG_PREALLOCATE_DESCRIPTORS by default.
Rename MVKDescriptorTypePreallocation to MVKDescriptorTypePool.

Docs/Whats_New.md

@@ -24,6 +24,8 @@ Released TBD
 - Avoid use of _Metal_ renderpass load and store actions on memoryless attachments.
 - Remove project qualifiers from references to `SPIRV-Cross` header files.
 - `MVKDescriptorPool` pools its descriptor sets.
+- Enable `MVKConfiguration::preallocateDescriptors` and `MVK_CONFIG_PREALLOCATE_DESCRIPTORS` 
+  environment variable by default to preallocate descriptors when a `VkDescriptorPool` is created.
 - Add `MVKConfiguration::apiVersionToAdvertise` and `MVK_CONFIG_API_VERSION_TO_ADVERTISE` 
   env var to configure **MoltenVK** to advertise a particular _Vulkan_ version.
 - Add `MVKConfiguration::advertiseExtensions` and `MVK_CONFIG_ADVERTISE_EXTENSIONS` 

MoltenVK/MoltenVK/API/vk_mvk_moltenvk.h

@@ -660,22 +660,20 @@ typedef struct {
 	VkBool32 texture1DAs2D;
 
 	/**
-	 * Controls whether MoltenVK should preallocate memory in each VkDescriptorPool
-	 * ccording to the values of the VkDescriptorPoolSize parameters. Doing so may improve
-	 * descriptor set allocation performance at a cost of preallocated application memory,
-	 * and possible descreased performance when creating and reseting the VkDescriptorPool.
-	 * If this setting is disabled, the descriptors required for a descriptor set will
-	 * be dynamically allocated in application memory when the descriptor set itself is allocated.
+	 * Controls whether MoltenVK should preallocate memory in each VkDescriptorPool according
+	 * to the values of the VkDescriptorPoolSize parameters. Doing so may improve descriptor set
+	 * allocation performance and memory stability at a cost of preallocated application memory.
+	 * If this setting is disabled, the descriptors required for a descriptor set will be individually
+	 * dynamically allocated in application memory when the descriptor set itself is allocated.
 	 *
-	 * The value of this parameter may be changed at any time during application runtime,
-	 * and the changed value will immediately effect behavior of VkDescriptorPools created
-	 * after the setting is changed.
+	 * The value of this parameter may be changed at any time during application runtime, and the
+	 * changed value will affect the behavior of VkDescriptorPools created after the value is changed.
 	 *
 	 * The initial value or this parameter is set by the
 	 * MVK_CONFIG_PREALLOCATE_DESCRIPTORS
 	 * runtime environment variable or MoltenVK compile-time build setting.
-	 * If neither is set, this setting is disabled by default, and MoltenVK will
-	 * dynamically allocate descriptors when the containing descriptor set is allocated.
+	 * If neither is set, this setting is enabled by default, and MoltenVK will
+	 * allocate a pool of descriptors when a VkDescriptorPool is created.
 	 */
 	VkBool32 preallocateDescriptors;
 

MoltenVK/MoltenVK/GPUObjects/MVKDescriptorSet.h

@@ -146,17 +146,17 @@ protected:
 
 
 #pragma mark -
-#pragma mark MVKDescriptorTypePreallocation
+#pragma mark MVKDescriptorTypePool
 
-/** Support class for MVKDescriptorPool that holds preallocated instances of a single concrete descriptor class. */
+/** Support class for MVKDescriptorPool that holds a pool of instances of a single concrete descriptor class. */
 template<class DescriptorClass>
-class MVKDescriptorTypePreallocation : public MVKBaseObject {
+class MVKDescriptorTypePool : public MVKBaseObject {
 
 public:
 
 	MVKVulkanAPIObject* getVulkanAPIObject() override { return nullptr; };
 
-	MVKDescriptorTypePreallocation(size_t poolSize);
+	MVKDescriptorTypePool(size_t poolSize);
 
 protected:
 	friend class MVKDescriptorPool;
@@ -200,7 +200,7 @@ public:
 
 protected:
 	friend class MVKDescriptorSet;
-	template<class> friend class MVKDescriptorTypePreallocation;
+	template<class> friend class MVKDescriptorTypePool;
 
 	void propagateDebugName() override {}
 	const uint32_t* getVariableDecriptorCounts(const VkDescriptorSetAllocateInfo* pAllocateInfo);
@@ -212,18 +212,18 @@ protected:
 	MVKSmallVector<MVKDescriptorSet> _descriptorSets;
 	MVKBitArray _descriptorSetAvailablility;
 
-	MVKDescriptorTypePreallocation<MVKUniformBufferDescriptor> _uniformBufferDescriptors;
-	MVKDescriptorTypePreallocation<MVKStorageBufferDescriptor> _storageBufferDescriptors;
-	MVKDescriptorTypePreallocation<MVKUniformBufferDynamicDescriptor> _uniformBufferDynamicDescriptors;
-	MVKDescriptorTypePreallocation<MVKStorageBufferDynamicDescriptor> _storageBufferDynamicDescriptors;
-	MVKDescriptorTypePreallocation<MVKInlineUniformBlockDescriptor> _inlineUniformBlockDescriptors;
-	MVKDescriptorTypePreallocation<MVKSampledImageDescriptor> _sampledImageDescriptors;
-	MVKDescriptorTypePreallocation<MVKStorageImageDescriptor> _storageImageDescriptors;
-	MVKDescriptorTypePreallocation<MVKInputAttachmentDescriptor> _inputAttachmentDescriptors;
-	MVKDescriptorTypePreallocation<MVKSamplerDescriptor> _samplerDescriptors;
-	MVKDescriptorTypePreallocation<MVKCombinedImageSamplerDescriptor> _combinedImageSamplerDescriptors;
-	MVKDescriptorTypePreallocation<MVKUniformTexelBufferDescriptor> _uniformTexelBufferDescriptors;
-	MVKDescriptorTypePreallocation<MVKStorageTexelBufferDescriptor> _storageTexelBufferDescriptors;
+	MVKDescriptorTypePool<MVKUniformBufferDescriptor> _uniformBufferDescriptors;
+	MVKDescriptorTypePool<MVKStorageBufferDescriptor> _storageBufferDescriptors;
+	MVKDescriptorTypePool<MVKUniformBufferDynamicDescriptor> _uniformBufferDynamicDescriptors;
+	MVKDescriptorTypePool<MVKStorageBufferDynamicDescriptor> _storageBufferDynamicDescriptors;
+	MVKDescriptorTypePool<MVKInlineUniformBlockDescriptor> _inlineUniformBlockDescriptors;
+	MVKDescriptorTypePool<MVKSampledImageDescriptor> _sampledImageDescriptors;
+	MVKDescriptorTypePool<MVKStorageImageDescriptor> _storageImageDescriptors;
+	MVKDescriptorTypePool<MVKInputAttachmentDescriptor> _inputAttachmentDescriptors;
+	MVKDescriptorTypePool<MVKSamplerDescriptor> _samplerDescriptors;
+	MVKDescriptorTypePool<MVKCombinedImageSamplerDescriptor> _combinedImageSamplerDescriptors;
+	MVKDescriptorTypePool<MVKUniformTexelBufferDescriptor> _uniformTexelBufferDescriptors;
+	MVKDescriptorTypePool<MVKStorageTexelBufferDescriptor> _storageTexelBufferDescriptors;
 	bool _hasPooledDescriptors;
 };
 

MoltenVK/MoltenVK/GPUObjects/MVKDescriptorSet.mm

@@ -319,12 +319,12 @@ MVKDescriptorSet::MVKDescriptorSet(MVKDescriptorPool* pool) : MVKVulkanAPIDevice
 
 
 #pragma mark -
-#pragma mark MVKDescriptorTypePreallocation
+#pragma mark MVKDescriptorTypePool
 
 // If preallocated, find the next availalble descriptor.
 // If not preallocated, create one on the fly.
 template<class DescriptorClass>
-VkResult MVKDescriptorTypePreallocation<DescriptorClass>::allocateDescriptor(MVKDescriptor** pMVKDesc,
+VkResult MVKDescriptorTypePool<DescriptorClass>::allocateDescriptor(MVKDescriptor** pMVKDesc,
 																			 MVKDescriptorPool* pool) {
 	DescriptorClass* mvkDesc;
 	if (pool->_hasPooledDescriptors) {
@@ -344,7 +344,7 @@ VkResult MVKDescriptorTypePreallocation<DescriptorClass>::allocateDescriptor(MVK
 // The descriptor will be reset when it is re-allocated. This streamlines the reset() of this pool.
 // If not preallocated, simply destroy returning descriptor.
 template<typename DescriptorClass>
-void MVKDescriptorTypePreallocation<DescriptorClass>::freeDescriptor(MVKDescriptor* mvkDesc,
+void MVKDescriptorTypePool<DescriptorClass>::freeDescriptor(MVKDescriptor* mvkDesc,
 																	 MVKDescriptorPool* pool) {
 	if (pool->_hasPooledDescriptors) {
 		size_t descIdx = (DescriptorClass*)mvkDesc - _descriptors.data();
@@ -356,12 +356,12 @@ void MVKDescriptorTypePreallocation<DescriptorClass>::freeDescriptor(MVKDescript
 
 // Preallocated descriptors will be reset when they are reused
 template<typename DescriptorClass>
-void MVKDescriptorTypePreallocation<DescriptorClass>::reset() {
+void MVKDescriptorTypePool<DescriptorClass>::reset() {
 	_availability.setAllBits();
 }
 
 template<typename DescriptorClass>
-MVKDescriptorTypePreallocation<DescriptorClass>::MVKDescriptorTypePreallocation(size_t poolSize) :
+MVKDescriptorTypePool<DescriptorClass>::MVKDescriptorTypePool(size_t poolSize) :
 	_descriptors(poolSize),
 	_availability(poolSize, true) {}
 

MoltenVK/MoltenVK/Utility/MVKEnvironment.h

@@ -248,9 +248,9 @@ void mvkSetMVKConfiguration(MVKConfiguration* pMVKConfig);
 #   define MVK_CONFIG_TEXTURE_1D_AS_2D    1
 #endif
 
-/** Preallocate descriptors when creating VkDescriptorPool. Disabled by default. */
+/** Preallocate descriptors when creating VkDescriptorPool. Enabled by default. */
 #ifndef MVK_CONFIG_PREALLOCATE_DESCRIPTORS
-#   define MVK_CONFIG_PREALLOCATE_DESCRIPTORS    0
+#   define MVK_CONFIG_PREALLOCATE_DESCRIPTORS    1
 #endif
 
 /** Use pooling for command resources in a VkCommandPool. Enabled by default. */