gpu/command_buffer/client/fenced_allocator.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file contains the definition of the FencedAllocator class.
   6
   7 #ifndef GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
   8 #define GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_
   9
  10 #include <vector>
  11
  12 #include "gpu/command_buffer/common/logging.h"
  13 #include "gpu/command_buffer/common/types.h"
  14 #include "gpu/gpu_export.h"
  15
  16 namespace gpu {
  17 class CommandBufferHelper;
  18
  19 // FencedAllocator provides a mechanism to manage allocations within a fixed
  20 // block of memory (storing the book-keeping externally). Furthermore this
  21 // class allows to free data "pending" the passage of a command buffer token,
  22 // that is, the memory won't be reused until the command buffer has processed
  23 // that token.
  24 //
  25 // NOTE: Although this class is intended to be used in the command buffer
  26 // environment which is multi-process, this class isn't "thread safe", because
  27 // it isn't meant to be shared across modules. It is thread-compatible though
  28 // (see http://www.corp.google.com/eng/doc/cpp_primer.html#thread_safety).
  29 class GPU_EXPORT FencedAllocator {
  30  public:
  31   typedef unsigned int Offset;
  32   // Invalid offset, returned by Alloc in case of failure.
  33   static const Offset kInvalidOffset = 0xffffffffU;
  34
  35   // Creates a FencedAllocator. Note that the size of the buffer is passed, but
  36   // not its base address: everything is handled as offsets into the buffer.
  37   FencedAllocator(unsigned int size,
  38                   CommandBufferHelper *helper);
  39
  40   ~FencedAllocator();
  41
  42   // Allocates a block of memory. If the buffer is out of directly available
  43   // memory, this function may wait until memory that was freed "pending a
  44   // token" can be re-used.
  45   //
  46   // Parameters:
  47   //   size: the size of the memory block to allocate.
  48   //
  49   // Returns:
  50   //   the offset of the allocated memory block, or kInvalidOffset if out of
  51   //   memory.
  52   Offset Alloc(unsigned int size);
  53
  54   // Frees a block of memory.
  55   //
  56   // Parameters:
  57   //   offset: the offset of the memory block to free.
  58   void Free(Offset offset);
  59
  60   // Frees a block of memory, pending the passage of a token. That memory won't
  61   // be re-allocated until the token has passed through the command stream.
  62   //
  63   // Parameters:
  64   //   offset: the offset of the memory block to free.
  65   //   token: the token value to wait for before re-using the memory.
  66   void FreePendingToken(Offset offset, int32 token);
  67
  68   // Frees any blocks pending a token for which the token has been read.
  69   void FreeUnused();
  70
  71   // Gets the size of the largest free block that is available without waiting.
  72   unsigned int GetLargestFreeSize();
  73
  74   // Gets the size of the largest free block that can be allocated if the
  75   // caller can wait. Allocating a block of this size will succeed, but may
  76   // block.
  77   unsigned int GetLargestFreeOrPendingSize();
  78
  79   // Checks for consistency inside the book-keeping structures. Used for
  80   // testing.
  81   bool CheckConsistency();
  82
  83   // True if any memory is allocated.
  84   bool InUse();
  85
  86   // Return bytes of memory that is IN_USE
  87   size_t bytes_in_use() const { return bytes_in_use_; }
  88
  89  private:
  90   // Status of a block of memory, for book-keeping.
  91   enum State {
  92     IN_USE,
  93     FREE,
  94     FREE_PENDING_TOKEN
  95   };
  96
  97   // Book-keeping sturcture that describes a block of memory.
  98   struct Block {
  99     State state;
 100     Offset offset;
 101     unsigned int size;
 102     int32 token;  // token to wait for in the FREE_PENDING_TOKEN case.
 103   };
 104
 105   // Comparison functor for memory block sorting.
 106   class OffsetCmp {
 107    public:
 108     bool operator() (const Block &left, const Block &right) {
 109       return left.offset < right.offset;
 110     }
 111   };
 112
 113   typedef std::vector<Block> Container;
 114   typedef unsigned int BlockIndex;
 115
 116   static const int32 kUnusedToken = 0;
 117
 118   // Gets the index of a memory block, given its offset.
 119   BlockIndex GetBlockByOffset(Offset offset);
 120
 121   // Collapse a free block with its neighbours if they are free. Returns the
 122   // index of the collapsed block.
 123   // NOTE: this will invalidate block indices.
 124   BlockIndex CollapseFreeBlock(BlockIndex index);
 125
 126   // Waits for a FREE_PENDING_TOKEN block to be usable, and free it. Returns
 127   // the new index of that block (since it may have been collapsed).
 128   // NOTE: this will invalidate block indices.
 129   BlockIndex WaitForTokenAndFreeBlock(BlockIndex index);
 130
 131   // Allocates a block of memory inside a given block, splitting it in two
 132   // (unless that block is of the exact requested size).
 133   // NOTE: this will invalidate block indices.
 134   // Returns the offset of the allocated block (NOTE: this is different from
 135   // the other functions that return a block index).
 136   Offset AllocInBlock(BlockIndex index, unsigned int size);
 137
 138   CommandBufferHelper *helper_;
 139   Container blocks_;
 140   size_t bytes_in_use_;
 141
 142   DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocator);
 143 };
 144
 145 // This class functions just like FencedAllocator, but its API uses pointers
 146 // instead of offsets.
 147 class FencedAllocatorWrapper {
 148  public:
 149   FencedAllocatorWrapper(unsigned int size,
 150                          CommandBufferHelper* helper,
 151                          void* base)
 152       : allocator_(size, helper),
 153         base_(base) { }
 154
 155   // Allocates a block of memory. If the buffer is out of directly available
 156   // memory, this function may wait until memory that was freed "pending a
 157   // token" can be re-used.
 158   //
 159   // Parameters:
 160   //   size: the size of the memory block to allocate.
 161   //
 162   // Returns:
 163   //   the pointer to the allocated memory block, or NULL if out of
 164   //   memory.
 165   void *Alloc(unsigned int size) {
 166     FencedAllocator::Offset offset = allocator_.Alloc(size);
 167     return GetPointer(offset);
 168   }
 169
 170   // Allocates a block of memory. If the buffer is out of directly available
 171   // memory, this function may wait until memory that was freed "pending a
 172   // token" can be re-used.
 173   // This is a type-safe version of Alloc, returning a typed pointer.
 174   //
 175   // Parameters:
 176   //   count: the number of elements to allocate.
 177   //
 178   // Returns:
 179   //   the pointer to the allocated memory block, or NULL if out of
 180   //   memory.
 181   template <typename T> T *AllocTyped(unsigned int count) {
 182     return static_cast<T *>(Alloc(count * sizeof(T)));
 183   }
 184
 185   // Frees a block of memory.
 186   //
 187   // Parameters:
 188   //   pointer: the pointer to the memory block to free.
 189   void Free(void *pointer) {
 190     GPU_DCHECK(pointer);
 191     allocator_.Free(GetOffset(pointer));
 192   }
 193
 194   // Frees a block of memory, pending the passage of a token. That memory won't
 195   // be re-allocated until the token has passed through the command stream.
 196   //
 197   // Parameters:
 198   //   pointer: the pointer to the memory block to free.
 199   //   token: the token value to wait for before re-using the memory.
 200   void FreePendingToken(void *pointer, int32 token) {
 201     GPU_DCHECK(pointer);
 202     allocator_.FreePendingToken(GetOffset(pointer), token);
 203   }
 204
 205   // Frees any blocks pending a token for which the token has been read.
 206   void FreeUnused() {
 207     allocator_.FreeUnused();
 208   }
 209
 210   // Gets a pointer to a memory block given the base memory and the offset.
 211   // It translates FencedAllocator::kInvalidOffset to NULL.
 212   void *GetPointer(FencedAllocator::Offset offset) {
 213     return (offset == FencedAllocator::kInvalidOffset) ?
 214         NULL : static_cast<char *>(base_) + offset;
 215   }
 216
 217   // Gets the offset to a memory block given the base memory and the address.
 218   // It translates NULL to FencedAllocator::kInvalidOffset.
 219   FencedAllocator::Offset GetOffset(void *pointer) {
 220     return pointer ?
 221         static_cast<FencedAllocator::Offset>(
 222             static_cast<char*>(pointer) - static_cast<char*>(base_)) :
 223         FencedAllocator::kInvalidOffset;
 224   }
 225
 226   // Gets the size of the largest free block that is available without waiting.
 227   unsigned int GetLargestFreeSize() {
 228     return allocator_.GetLargestFreeSize();
 229   }
 230
 231   // Gets the size of the largest free block that can be allocated if the
 232   // caller can wait.
 233   unsigned int GetLargestFreeOrPendingSize() {
 234     return allocator_.GetLargestFreeOrPendingSize();
 235   }
 236
 237   // Checks for consistency inside the book-keeping structures. Used for
 238   // testing.
 239   bool CheckConsistency() {
 240     return allocator_.CheckConsistency();
 241   }
 242
 243   // True if any memory is allocated.
 244   bool InUse() {
 245     return allocator_.InUse();
 246   }
 247
 248   FencedAllocator &allocator() { return allocator_; }
 249
 250   size_t bytes_in_use() const { return allocator_.bytes_in_use(); }
 251
 252  private:
 253   FencedAllocator allocator_;
 254   void* base_;
 255   DISALLOW_IMPLICIT_CONSTRUCTORS(FencedAllocatorWrapper);
 256 };
 257
 258 }  // namespace gpu
 259
 260 #endif  // GPU_COMMAND_BUFFER_CLIENT_FENCED_ALLOCATOR_H_