GPU Vulkan Display: minor optimization: reuse resources from old swapChain when creating new one

Author: davidrohr

GPU/GPUTracking/display/backend/GPUDisplayBackendVulkan.cxx

@@ -769,7 +769,7 @@ void GPUDisplayBackendVulkan::clearTextureSampler()
 
 // ---------------------------- VULKAN SWAPCHAIN MANAGEMENT ----------------------------
 
-void GPUDisplayBackendVulkan::createSwapChain(bool forScreenshot, bool forMixing)
+void GPUDisplayBackendVulkan::createSwapChain(bool forScreenshot, bool forMixing, vk::SwapchainKHR oldSwapChain)
 {
   mDownsampleFactor = getDownsampleFactor(forScreenshot);
   mDownsampleFSAA = mDownsampleFactor != 1;
@@ -805,14 +805,17 @@ void GPUDisplayBackendVulkan::createSwapChain(bool forScreenshot, bool forMixing
   swapCreateInfo.compositeAlpha = vk::CompositeAlphaFlagBitsKHR::eOpaque;
   swapCreateInfo.presentMode = mPresentMode;
   swapCreateInfo.clipped = true;
-  swapCreateInfo.oldSwapchain = VkSwapchainKHR(VK_NULL_HANDLE);
+  swapCreateInfo.oldSwapchain = oldSwapChain;
   if (mSwapchainImageReadable) {
     swapCreateInfo.imageUsage |= vk::ImageUsageFlagBits::eTransferSrc;
   }
   if (mDownsampleFSAA) {
     swapCreateInfo.imageUsage |= vk::ImageUsageFlagBits::eTransferDst;
   }
   mSwapChain = mDevice.createSwapchainKHR(swapCreateInfo, nullptr);
+  if (oldSwapChain) {
+    mDevice.destroySwapchainKHR(oldSwapChain, nullptr);
+  }
 
   mSwapChainImages = mDevice.getSwapchainImagesKHR(mSwapChain);
   uint32_t oldFramesInFlight = mFramesInFlight, oldImageCount = mImageCount;
@@ -841,10 +844,12 @@ void GPUDisplayBackendVulkan::createSwapChain(bool forScreenshot, bool forMixing
   }
 }
 
-void GPUDisplayBackendVulkan::clearSwapChain()
+void GPUDisplayBackendVulkan::clearSwapChain(bool keepSwapChain)
 {
   clearVector(mSwapChainImageViews, [&](auto& x) { mDevice.destroyImageView(x, nullptr); });
-  mDevice.destroySwapchainKHR(mSwapChain, nullptr);
+  if (!keepSwapChain) {
+    mDevice.destroySwapchainKHR(mSwapChain, nullptr);
+  }
 }
 
 void GPUDisplayBackendVulkan::recreateRendering(bool forScreenshot, bool forMixing)
@@ -856,8 +861,8 @@ void GPUDisplayBackendVulkan::recreateRendering(bool forScreenshot, bool forMixi
   if (needUpdateOffscreenBuffers) {
     clearOffscreenBuffers();
     if (needUpdateSwapChain) {
-      clearSwapChain();
-      createSwapChain(forScreenshot, forMixing);
+      clearSwapChain(true);
+      createSwapChain(forScreenshot, forMixing, mSwapChain);
     }
     createOffscreenBuffers(forScreenshot, forMixing);
   }

GPU/GPUTracking/display/backend/GPUDisplayBackendVulkan.h

@@ -99,7 +99,7 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   void startFillCommandBuffer(vk::CommandBuffer& commandBuffer, uint32_t imageIndex, bool toMixBuffer = false);
   void endFillCommandBuffer(vk::CommandBuffer& commandBuffer);
   vk::CommandBuffer getSingleTimeCommandBuffer();
-  void waitTimeline(uint64_t value); // Wait until the timeline semaphore reached value, 0 = nothing to wait for
+  void waitTimeline(uint64_t value);
   template <class... Args>
   uint64_t queueSubmit(uint64_t* timelineSignalValue, Args&&... args); // Submit under mQueueMutex; if timelineSignalValue (the entry in pSignalSemaphoreValues) is set, write the next timeline value there first. Returns the current timeline value
   void submitSingleTimeCommandBuffer(vk::CommandBuffer commandBuffer);
@@ -114,7 +114,7 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   void createCommandBuffers();
   void createSemaphores();
   void createUniformLayoutsAndBuffers();
-  void createSwapChain(bool forScreenshot = false, bool forMixing = false);
+  void createSwapChain(bool forScreenshot = false, bool forMixing = false, vk::SwapchainKHR oldSwapChain = {});
   void createOffscreenBuffers(bool forScreenshot = false, bool forMixing = false);
   void createPipeline();
   void clearDevice();
@@ -124,7 +124,7 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   void clearSemaphores();
   void clearUniformLayoutsAndBuffers();
   void clearOffscreenBuffers();
-  void clearSwapChain();
+  void clearSwapChain(bool keepSwapChain = false);
   void clearPipeline();
   void recreateRendering(bool forScreenshot = false, bool forMixing = false);
   void needRecordCommandBuffers();
@@ -175,7 +175,7 @@ class GPUDisplayBackendVulkan : public GPUDisplayBackend
   std::vector<vk::CommandBuffer> mCommandBuffersText;
   std::vector<vk::CommandBuffer> mCommandBuffersTexture;
   std::vector<vk::CommandBuffer> mCommandBuffersMix;
-  std::vector<vk::CommandBuffer> mCommandBuffersPresent;         // Pre-recorded per swapchain image: transition to ePresentSrcKHR, last in every frame
+  std::vector<vk::CommandBuffer> mCommandBuffersPresent;
   std::vector<vk::CommandBufferSubmitInfo> mFrameCommandBuffers; // All command buffers of the current frame, submitted as one batch, ordered by barriers
   std::vector<bool> mCommandBufferUpToDate;
   std::vector<vk::Semaphore> mImageAvailableSemaphore;