Add ability to disable command memory pooling using MVK_CONFIG_USE_COMMAND_POOLING

environment variable.

Add ability to track MVKObjectPool allocation and pool residency counts.

Docs/Whats_New.md

@@ -24,6 +24,9 @@ Released TBD
   within a single `MTLRenderEncoder`.
 - Increase value of `VkPhysicalDeviceLimits::minStorageBufferOffsetAlignment` 
   to `16` to avoid Metal validation assertions.
+- Add ability to disable command memory pooling using `MVK_CONFIG_USE_COMMAND_POOLING`
+  environment variable.
+
 
 
 

MoltenVK/MoltenVK/API/vk_mvk_moltenvk.h

@@ -154,6 +154,15 @@ typedef unsigned long MTLLanguageVersion;
  *    be dynamically allocated in application memory when the descriptor set itself is allocated.
  *    This setting is disabled by default, and MoltenVK will dynamically allocate descriptors
  *    when the containing descriptor set is allocated.
+ *
+ * 8. The MVK_CONFIG_USE_COMMAND_POOLING runtime environment variable or MoltenVK compile-time
+ *    build setting controls whether MoltenVK should use pools to manage memory used when
+ *    adding commands to command buffers. If this environment variable is enabled, MoltenVK
+ *    will use a pool to hold command resources for reuse during command execution. If this
+ *    environment variable is disabled, command memory is allocated and destroyed each time
+ *    a command is executed. This is a classic time-space trade off. When command pooling is
+ *    active, the memory in the pool can be cleared via a call to the vkTrimCommandPoolKHR()
+ *    command. This setting is enabled by default, and MoltenVK will pool command memory.
  */
 typedef struct {
 

MoltenVK/MoltenVK/Commands/MVKCommandPool.h

@@ -182,7 +182,9 @@ public:
 	/** Resets the command pool. */
 	VkResult reset( VkCommandPoolResetFlags flags);
 
-	MVKCommandPool(MVKDevice* device, const VkCommandPoolCreateInfo* pCreateInfo);
+	MVKCommandPool(MVKDevice* device,
+				   const VkCommandPoolCreateInfo* pCreateInfo,
+				   bool usePooling);
 
 	~MVKCommandPool() override;
 

MoltenVK/MoltenVK/Commands/MVKCommandPool.mm

@@ -134,57 +134,58 @@ void MVKCommandPool::trim() {
 #pragma mark Construction
 
 MVKCommandPool::MVKCommandPool(MVKDevice* device,
-							   const VkCommandPoolCreateInfo* pCreateInfo) :
+							   const VkCommandPoolCreateInfo* pCreateInfo,
+							   bool usePooling) :
 	MVKVulkanAPIDeviceObject(device),
 	_queueFamilyIndex(pCreateInfo->queueFamilyIndex),
-	_commandBufferPool(device),
+	_commandBufferPool(device, usePooling),
 	_commandEncodingPool(this),
-	_cmdPipelineBarrierPool(this),
+	_cmdPipelineBarrierPool(this, usePooling),
-	_cmdBindPipelinePool(this),
+	_cmdBindPipelinePool(this, usePooling),
-	_cmdBeginRenderPassPool(this),
+	_cmdBeginRenderPassPool(this, usePooling),
-	_cmdNextSubpassPool(this),
+	_cmdNextSubpassPool(this, usePooling),
-	_cmdExecuteCommandsPool(this),
+	_cmdExecuteCommandsPool(this, usePooling),
-	_cmdEndRenderPassPool(this),
+	_cmdEndRenderPassPool(this, usePooling),
-	_cmdBindDescriptorSetsPool(this),
+	_cmdBindDescriptorSetsPool(this, usePooling),
-	_cmdSetViewportPool(this),
+	_cmdSetViewportPool(this, usePooling),
-	_cmdSetScissorPool(this),
+	_cmdSetScissorPool(this, usePooling),
-	_cmdSetLineWidthPool(this),
+	_cmdSetLineWidthPool(this, usePooling),
-	_cmdSetDepthBiasPool(this),
+	_cmdSetDepthBiasPool(this, usePooling),
-	_cmdSetBlendConstantsPool(this),
+	_cmdSetBlendConstantsPool(this, usePooling),
-	_cmdSetDepthBoundsPool(this),
+	_cmdSetDepthBoundsPool(this, usePooling),
-	_cmdSetStencilCompareMaskPool(this),
+	_cmdSetStencilCompareMaskPool(this, usePooling),
-	_cmdSetStencilWriteMaskPool(this),
+	_cmdSetStencilWriteMaskPool(this, usePooling),
-	_cmdSetStencilReferencePool(this),
+	_cmdSetStencilReferencePool(this, usePooling),
-	_cmdBindVertexBuffersPool(this),
+	_cmdBindVertexBuffersPool(this, usePooling),
-	_cmdBindIndexBufferPool(this),
+	_cmdBindIndexBufferPool(this, usePooling),
-	_cmdDrawPool(this),
+	_cmdDrawPool(this, usePooling),
-	_cmdDrawIndexedPool(this),
+	_cmdDrawIndexedPool(this, usePooling),
-	_cmdDrawIndirectPool(this),
+	_cmdDrawIndirectPool(this, usePooling),
-	_cmdDrawIndexedIndirectPool(this),
+	_cmdDrawIndexedIndirectPool(this, usePooling),
-	_cmdCopyImagePool(this),
+	_cmdCopyImagePool(this, usePooling),
-	_cmdBlitImagePool(this),
+	_cmdBlitImagePool(this, usePooling),
-	_cmdResolveImagePool(this),
+	_cmdResolveImagePool(this, usePooling),
-	_cmdFillBufferPool(this),
+	_cmdFillBufferPool(this, usePooling),
-	_cmdUpdateBufferPool(this),
+	_cmdUpdateBufferPool(this, usePooling),
-	_cmdCopyBufferPool(this),
+	_cmdCopyBufferPool(this, usePooling),
-	_cmdBufferImageCopyPool(this),
+	_cmdBufferImageCopyPool(this, usePooling),
-	_cmdClearAttachmentsPool(this),
+	_cmdClearAttachmentsPool(this, usePooling),
-	_cmdClearImagePool(this),
+	_cmdClearImagePool(this, usePooling),
-	_cmdBeginQueryPool(this),
+	_cmdBeginQueryPool(this, usePooling),
-	_cmdEndQueryPool(this),
+	_cmdEndQueryPool(this, usePooling),
-	_cmdWriteTimestampPool(this),
+	_cmdWriteTimestampPool(this, usePooling),
-	_cmdResetQueryPoolPool(this),
+	_cmdResetQueryPoolPool(this, usePooling),
-	_cmdCopyQueryPoolResultsPool(this),
+	_cmdCopyQueryPoolResultsPool(this, usePooling),
-	_cmdPushConstantsPool(this),
+	_cmdPushConstantsPool(this, usePooling),
-	_cmdDispatchPool(this),
+	_cmdDispatchPool(this, usePooling),
-	_cmdDispatchIndirectPool(this),
+	_cmdDispatchIndirectPool(this, usePooling),
-	_cmdPushDescriptorSetPool(this),
+	_cmdPushDescriptorSetPool(this, usePooling),
-	_cmdPushSetWithTemplatePool(this),
+	_cmdPushSetWithTemplatePool(this, usePooling),
-	_cmdDebugMarkerBeginPool(this),
+	_cmdDebugMarkerBeginPool(this, usePooling),
-	_cmdDebugMarkerEndPool(this),
+	_cmdDebugMarkerEndPool(this, usePooling),
-	_cmdDebugMarkerInsertPool(this),
+	_cmdDebugMarkerInsertPool(this, usePooling),
-	_cmdSetResetEventPool(this),
+	_cmdSetResetEventPool(this, usePooling),
-	_cmdWaitEventsPool(this)
+	_cmdWaitEventsPool(this, usePooling)
 // when extending be sure to add to trim() as well
 {}
 

MoltenVK/MoltenVK/GPUObjects/MVKDevice.h

@@ -666,16 +666,6 @@ public:
     /** Performance statistics. */
     MVKPerformanceStatistics _performanceStatistics;
 
-	// Indicates whether semaphores should use a MTLFence if available.
-	// Set by the MVK_ALLOW_METAL_FENCES environment variable if MTLFences are available.
-	// This should be a temporary fix after some repair to semaphore handling.
-	bool _useMTLFenceForSemaphores;
-
-	// Indicates whether semaphores should use a MTLEvent if available.
-	// Set by the MVK_ALLOW_METAL_EVENTS environment variable if MTLEvents are available.
-	// This should be a temporary fix after some repair to semaphore handling.
-	bool _useMTLEventForSemaphores;
-
 
 #pragma mark Construction
 
@@ -724,6 +714,9 @@ protected:
     id<MTLBuffer> _globalVisibilityResultMTLBuffer;
     uint32_t _globalVisibilityQueryCount;
     std::mutex _vizLock;
+	bool _useMTLFenceForSemaphores;
+	bool _useMTLEventForSemaphores;
+	bool _useCommandPooling;
 };
 
 

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -2395,7 +2395,7 @@ void MVKDevice::destroyRenderPass(MVKRenderPass* mvkRP,
 
 MVKCommandPool* MVKDevice::createCommandPool(const VkCommandPoolCreateInfo* pCreateInfo,
 											const VkAllocationCallbacks* pAllocator) {
-	return new MVKCommandPool(this, pCreateInfo);
+	return new MVKCommandPool(this, pCreateInfo, _useCommandPooling);
 }
 
 void MVKDevice::destroyCommandPool(MVKCommandPool* mvkCmdPool,
@@ -2650,16 +2650,30 @@ void MVKDevice::initPhysicalDevice(MVKPhysicalDevice* physicalDevice, const VkDe
 	_pProperties = &_physicalDevice->_properties;
 	_pMemoryProperties = &_physicalDevice->_memoryProperties;
 
+
+	// Indicates whether semaphores should use a MTLFence if available.
+	// Set by the MVK_ALLOW_METAL_FENCES environment variable if MTLFences are available.
+	// This should be a temporary fix after some repair to semaphore handling.
 	_useMTLFenceForSemaphores = false;
 	if (_pMetalFeatures->fences) {
 		MVK_SET_FROM_ENV_OR_BUILD_BOOL(_useMTLFenceForSemaphores, MVK_ALLOW_METAL_FENCES);
 	}
+
+	// Indicates whether semaphores should use a MTLEvent if available.
+	// Set by the MVK_ALLOW_METAL_EVENTS environment variable if MTLEvents are available.
+	// This should be a temporary fix after some repair to semaphore handling.
 	_useMTLEventForSemaphores = false;
 	if (_pMetalFeatures->events) {
 		MVK_SET_FROM_ENV_OR_BUILD_BOOL(_useMTLEventForSemaphores, MVK_ALLOW_METAL_EVENTS);
 	}
 	MVKLogInfo("Using %s for Vulkan semaphores.", _useMTLFenceForSemaphores ? "MTLFence" : (_useMTLEventForSemaphores ? "MTLEvent" : "emulation"));
 
+#ifndef MVK_CONFIG_USE_COMMAND_POOLING
+#   define MVK_CONFIG_USE_COMMAND_POOLING    1
+#endif
+	_useCommandPooling = MVK_CONFIG_USE_COMMAND_POOLING;
+	MVK_SET_FROM_ENV_OR_BUILD_BOOL(_useCommandPooling, MVK_CONFIG_USE_COMMAND_POOLING);
+
 #if MVK_MACOS
 	// If we have selected a high-power GPU and want to force the window system
 	// to use it, force the window system to use a high-power GPU by calling the

MoltenVK/MoltenVK/Utility/MVKObjectPool.h

@@ -23,6 +23,9 @@
 #include <mutex>
 
 
+#pragma mark -
+#pragma mark MVKLinkableMixin
+
 /**
  * Instances of sublcasses of this mixin can participate in a typed linked list or pool.
  * A simple implementation of the CRTP (https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern).
@@ -47,6 +50,13 @@ protected:
 #pragma mark -
 #pragma mark MVKObjectPool
 
+/** Track pool stats. */
+typedef struct {
+	uint64_t created = 0;
+	uint64_t alive = 0;
+	uint64_t resident = 0;
+} MVKObjectPoolCounts;
+
 /**
  * Manages a pool of instances of a particular object type.
  *
@@ -80,9 +90,13 @@ public:
      * aquireObject() and returnObject() must be made from the same thread.
 	 */
 	T* acquireObject() {
-		T* obj = VK_NULL_HANDLE;
+		T* obj = nullptr;
 		if (_isPooling) { obj = nextObject(); }
-		if ( !obj ) { obj = newObject(); }
+		if ( !obj ) {
+			obj = newObject();
+			_counts.created++;
+			_counts.alive++;
+		}
 
 		return obj;
 	}
@@ -102,11 +116,12 @@ public:
 
 		if (_isPooling) {
 			if (_tail) { _tail->_next = obj; }
-			obj->_next = VK_NULL_HANDLE;
+			obj->_next = nullptr;
 			_tail = obj;
 			if ( !_head ) { _head = obj; }
+			_counts.resident++;
 		} else {
-			obj->destroy();
+			destroyObject(obj);
 		}
 	}
 
@@ -122,12 +137,15 @@ public:
 		returnObject(obj);
 	}
 
-	/** Clears all the objects from this pool, deleting each one. This method is thread-safe. */
+	/** Clears all the objects from this pool, destroying each one. This method is thread-safe. */
 	void clear() {
         std::lock_guard<std::mutex> lock(_lock);
-		while ( T* obj = nextObject() ) { obj->destroy(); }
+		while ( T* obj = nextObject() ) { destroyObject(obj); }
 	}
 
+	/** Returns the current counts. */
+	MVKObjectPoolCounts getCounts() { return _counts; }
+
 	/**
 	 * Configures this instance to either use pooling, or not, depending on the
 	 * value of isPooling, which defaults to true if not indicated explicitly.
@@ -146,9 +164,10 @@ protected:
     T* nextObject() {
         T* obj = _head;
         if (obj) {
-            _head = (T*)obj->_next;						// Will be null for last object in pool
+            _head = (T*)obj->_next;				// Will be null for last object in pool
-            if ( !_head ) { _tail = VK_NULL_HANDLE; }	// If last, also clear tail
+            if ( !_head ) { _tail = nullptr; }	// If last, also clear tail
-            obj->_next = VK_NULL_HANDLE;				// Objects in the wild should never think they are still part of this pool
+            obj->_next = nullptr;				// Objects in the wild should never think they are still part of this pool
+			_counts.resident--;
         }
         return obj;
     }
@@ -156,9 +175,16 @@ protected:
     /** Returns a new instance of the type of object managed by this pool. */
     virtual T* newObject() = 0;
 
+	/** Destroys the object. */
+	void destroyObject(T* obj) {
+		obj->destroy();
+		_counts.alive--;
+	}
+
     std::mutex _lock;
 	T* _head = nullptr;
 	T* _tail = nullptr;
 	bool _isPooling;
+	MVKObjectPoolCounts _counts;
 };