Setup system in Vulkan to reuse VkDescriptorSet allocations.

src/gpu/vk/GrVkDescriptorSetManager.h

+/*
+* Copyright 2016 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+
+#ifndef GrVkDescriptorSetManager_DEFINED
+#define GrVkDescriptorSetManager_DEFINED
+
+#include "GrResourceHandle.h"
+#include "GrVkDescriptorPool.h"
+#include "SkRefCnt.h"
+#include "SkTArray.h"
+#include "vk/GrVkDefines.h"
+
+class GrVkDescriptorSet;
+class GrVkGpu;
+
+/**
+ * This class handles the allocation of descriptor sets for a given VkDescriptorSetLayout. It will
+ * try to reuse previously allocated descriptor sets if they are no longer in use by other objects.
+ */
+class GrVkDescriptorSetManager {
+public:
+    GR_DEFINE_RESOURCE_HANDLE_CLASS(Handle);
+
+    GrVkDescriptorSetManager(GrVkGpu* gpu,
+                             VkDescriptorSetLayout layout,
+                             VkDescriptorType,
+                             uint32_t samplerCount);
+    ~GrVkDescriptorSetManager() {}
+
+    void abandon();
+    void release(const GrVkGpu* gpu);
+
+    const GrVkDescriptorSet* getDescriptorSet(GrVkGpu* gpu, const Handle& handle);
+
+    void recycleDescriptorSet(const GrVkDescriptorSet*);
+
+    int isCompatible(uint32_t numSamplers) const { return numSamplers == fNumSamplerBindings; }
+
+private:
+    struct DescriptorPoolManager {
+        DescriptorPoolManager(VkDescriptorSetLayout layout, VkDescriptorType type,
+                              uint32_t samplerCount, GrVkGpu* gpu)
+            : fDescLayout(layout)
+            , fDescType(type)
+            , fCurrentDescriptorCount(0)
+            , fPool(nullptr) {
+            if (VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER == type) {
+                fDescCountPerSet = kNumUniformDescPerSet;
+            } else {
+                SkASSERT(VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER);
+                fDescCountPerSet = samplerCount;
+            }
+
+            SkASSERT(fDescCountPerSet < kStartNumDescriptors);
+            fMaxDescriptors = kStartNumDescriptors;
+            SkASSERT(fMaxDescriptors > 0);
+            this->getNewPool(gpu);
+        }
+
+        ~DescriptorPoolManager() {
+            SkASSERT(!fDescLayout);
+            SkASSERT(!fPool);
+        }
+
+        void getNewDescriptorSet(GrVkGpu* gpu, VkDescriptorSet* ds);
+
+        void freeGPUResources(const GrVkGpu* gpu);
+        void abandonGPUResources();
+
+        VkDescriptorSetLayout  fDescLayout; // Not owned by this class
+        VkDescriptorType       fDescType;
+        uint32_t               fDescCountPerSet;
+        uint32_t               fMaxDescriptors;
+        uint32_t               fCurrentDescriptorCount;
+        GrVkDescriptorPool*    fPool;
+
+    private:
+        enum {
+            kNumUniformDescPerSet = 2,
+            kMaxDescriptors = 1024,
+            kStartNumDescriptors = 16, // must be less than kMaxUniformDescriptors
+        };
+
+        void getNewPool(GrVkGpu* gpu);
+    };
+
+    DescriptorPoolManager              fPoolManager;
+    SkTArray<const GrVkDescriptorSet*> fFreeSets;
+    // If the number of bindings is 0 we assume this is for uniform buffers
+    uint32_t                           fNumSamplerBindings;
+};
+
+#endif