ENH: refine code comments

paddle/memory/detail/buddy_allocator.h

@@ -42,7 +42,7 @@ class BuddyAllocator {
   void Free(void*);
   size_t Used();
 
- private:
+ public:
   // Disable copy and assignment.
   BuddyAllocator(const BuddyAllocator&) = delete;
   BuddyAllocator& operator=(const BuddyAllocator&) = delete;
@@ -57,6 +57,7 @@ class BuddyAllocator {
 
   /*! \brief If existing chunks are not suitable, refill pool */
   PoolSet::iterator RefillPool();
+
   /**
    *  \brief Find the suitable chunk from existing pool
    *

paddle/memory/detail/meta_cache.h

@@ -23,13 +23,13 @@ namespace paddle {
 namespace memory {
 namespace detail {
 
-/*! A cache for accessing memory block meta-data that may be expensive to access
-   directly.
-
-    Note: this class exists to unify the metadata format between GPU and CPU
-   allocations.
-    It should be removed when the CPU can access all GPU allocations directly
-   via UVM.
+/**
+ *  \brief A cache for accessing memory block meta-data that may be expensive
+ *         to access directly.
+ *
+ *  \note  This class exists to unify the metadata format between GPU and CPU
+ *         allocations. It should be removed when the CPU can access all GPU
+ *         allocations directly via UVM.
  */
 class MetadataCache {
  public:
@@ -42,14 +42,7 @@ class MetadataCache {
   /*! \brief Store the associated metadata for the specified memory block. */
   void store(MemoryBlock*, const Metadata&);
 
- public:
-  /*! \brief Acquire any external metadata updates. */
-  void acquire(MemoryBlock*);
-
-  /*! \brief Publish any local updates externally. */
-  void release(MemoryBlock*);
-
-  /*! \brief Indicate that the specified metadata will no longer be used */
+  /*! \brief Indicate that the specified metadata will no longer be used. */
   void invalidate(MemoryBlock*);
 
  public:

paddle/memory/detail/system_allocator.cc

@@ -60,7 +60,7 @@ void CPUAllocator::Free(void* p, size_t size, size_t index) {
   free(p);
 }
 
-bool CPUAllocator::UseGpu() { return false; }
+bool CPUAllocator::UseGpu() const { return false; }
 
 #ifndef PADDLE_ONLY_CPU
 
@@ -133,7 +133,7 @@ void GPUAllocator::Free(void* p, size_t size, size_t index) {
   }
 }
 
-bool GPUAllocator::UseGpu() { return true; }
+bool GPUAllocator::UseGpu() const { return true; }
 
 #endif  // PADDLE_ONLY_CPU
 

paddle/memory/detail/system_allocator.h

@@ -32,14 +32,14 @@ class SystemAllocator {
   virtual ~SystemAllocator() {}
   virtual void* Alloc(size_t& index, size_t size) = 0;
   virtual void Free(void* p, size_t size, size_t index) = 0;
-  virtual bool UseGpu() = 0;
+  virtual bool UseGpu() const = 0;
 };
 
 class CPUAllocator : public SystemAllocator {
  public:
   virtual void* Alloc(size_t& index, size_t size);
   virtual void Free(void* p, size_t size, size_t index);
-  virtual bool UseGpu();
+  virtual bool UseGpu() const;
 };
 
 #ifndef PADDLE_ONLY_CPU
@@ -47,7 +47,7 @@ class GPUAllocator : public SystemAllocator {
  public:
   virtual void* Alloc(size_t& index, size_t size);
   virtual void Free(void* p, size_t size, size_t index);
-  virtual bool UseGpu();
+  virtual bool UseGpu() const;
 
  private:
   size_t gpu_alloc_size_ = 0;