[dxvk] Prefer VRAM allocation over dedicated sysmem allocation

May in some cases improve performance when under memory pressure:
If a dedicated allocation is preferred, but the alloaction fails,
try to allocate memory from an already allocated chunk instead
of falling back to system memory right away.

src/dxvk/dxvk_buffer.cpp

@@ -91,10 +91,8 @@ namespace dxvk {
     float priority = isGpuWritable ? 1.0f : 0.5f;
     
     // Ask driver whether we should be using a dedicated allocation
-    bool useDedicated = dedicatedRequirements.prefersDedicatedAllocation;
-
     handle.memory = m_memAlloc->alloc(&memReq.memoryRequirements,
-      useDedicated ? &dedMemoryAllocInfo : nullptr, m_memFlags, priority);
+      dedicatedRequirements, dedMemoryAllocInfo, m_memFlags, priority);
     
     if (vkd->vkBindBufferMemory(vkd->device(), handle.buffer,
         handle.memory.memory(), handle.memory.offset()) != VK_SUCCESS)

src/dxvk/dxvk_image.cpp

@@ -98,10 +98,8 @@ namespace dxvk {
     float priority = isGpuWritable ? 1.0f : 0.5f;
 
     // Ask driver whether we should be using a dedicated allocation
-    bool useDedicated = dedicatedRequirements.prefersDedicatedAllocation;
-
     m_memory = memAlloc.alloc(&memReq.memoryRequirements,
-      useDedicated ? &dedMemoryAllocInfo : nullptr, memFlags, priority);
+      dedicatedRequirements, dedMemoryAllocInfo, memFlags, priority);
     
     // Try to bind the allocated memory slice to the image
     if (m_vkd->vkBindImageMemory(m_vkd->device(),

src/dxvk/dxvk_memory.cpp

@@ -181,18 +181,28 @@ namespace dxvk {
   
   DxvkMemory DxvkMemoryAllocator::alloc(
     const VkMemoryRequirements*             req,
-    const VkMemoryDedicatedAllocateInfoKHR* dedAllocInfo,
+    const VkMemoryDedicatedRequirements&    dedAllocReq,
+    const VkMemoryDedicatedAllocateInfoKHR& dedAllocInfo,
           VkMemoryPropertyFlags             flags,
           float                             priority) {
     std::lock_guard<std::mutex> lock(m_mutex);
 
+    // Try to allocate from a memory type which supports the given flags exactly
+    auto dedAllocPtr = dedAllocReq.prefersDedicatedAllocation ? &dedAllocInfo : nullptr;
+    DxvkMemory result = this->tryAlloc(req, dedAllocPtr, flags, priority);
+
+    // If the first attempt failed, try ignoring the dedicated allocation
+    if (!result && dedAllocPtr && !dedAllocReq.requiresDedicatedAllocation) {
+      result = this->tryAlloc(req, nullptr, flags, priority);
+      dedAllocPtr = nullptr;
+    }
+
+    // If that still didn't work, probe slower memory types as well
     VkMemoryPropertyFlags optFlags = VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT
                                    | VK_MEMORY_PROPERTY_HOST_CACHED_BIT;
     
-    DxvkMemory result = this->tryAlloc(req, dedAllocInfo, flags, priority);
-
     if (!result && (flags & optFlags))
-      result = this->tryAlloc(req, dedAllocInfo, flags & ~optFlags, priority);
+      result = this->tryAlloc(req, dedAllocPtr, flags & ~optFlags, priority);
     
     if (!result) {
       Logger::err(str::format(

src/dxvk/dxvk_memory.h

@@ -239,6 +239,7 @@ namespace dxvk {
      * \brief Allocates device memory
      * 
      * \param [in] req Memory requirements
+     * \param [in] dedAllocReq Dedicated allocation requirements
      * \param [in] dedAllocInfo Dedicated allocation info
      * \param [in] flags Memory type flags
      * \param [in] priority Device-local memory priority
@@ -246,7 +247,8 @@ namespace dxvk {
      */
     DxvkMemory alloc(
       const VkMemoryRequirements*             req,
-      const VkMemoryDedicatedAllocateInfoKHR* dedAllocInfo,
+      const VkMemoryDedicatedRequirements&    dedAllocReq,
+      const VkMemoryDedicatedAllocateInfoKHR& dedAllocInfo,
             VkMemoryPropertyFlags             flags,
             float                             priority);