src/gpu/command_buffer/client/transfer_buffer.cc

   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 // A class to Manage a growing transfer buffer.
   6
   7 #include "gpu/command_buffer/client/transfer_buffer.h"
   8
   9 #include "base/bits.h"
  10 #include "base/debug/trace_event.h"
  11 #include "base/logging.h"
  12 #include "gpu/command_buffer/client/cmd_buffer_helper.h"
  13
  14 namespace gpu {
  15
  16 TransferBuffer::TransferBuffer(
  17     CommandBufferHelper* helper)
  18     : helper_(helper),
  19       result_size_(0),
  20       default_buffer_size_(0),
  21       min_buffer_size_(0),
  22       max_buffer_size_(0),
  23       alignment_(0),
  24       size_to_flush_(0),
  25       bytes_since_last_flush_(0),
  26       buffer_id_(-1),
  27       result_buffer_(NULL),
  28       result_shm_offset_(0),
  29       usable_(true) {
  30 }
  31
  32 TransferBuffer::~TransferBuffer() {
  33   Free();
  34 }
  35
  36 bool TransferBuffer::Initialize(
  37     unsigned int default_buffer_size,
  38     unsigned int result_size,
  39     unsigned int min_buffer_size,
  40     unsigned int max_buffer_size,
  41     unsigned int alignment,
  42     unsigned int size_to_flush) {
  43   result_size_ = result_size;
  44   default_buffer_size_ = default_buffer_size;
  45   min_buffer_size_ = min_buffer_size;
  46   max_buffer_size_ = max_buffer_size;
  47   alignment_ = alignment;
  48   size_to_flush_ = size_to_flush;
  49   ReallocateRingBuffer(default_buffer_size_ - result_size);
  50   return HaveBuffer();
  51 }
  52
  53 void TransferBuffer::Free() {
  54   if (HaveBuffer()) {
  55     TRACE_EVENT0("gpu", "TransferBuffer::Free");
  56     helper_->Finish();
  57     helper_->command_buffer()->DestroyTransferBuffer(buffer_id_);
  58     buffer_id_ = -1;
  59     buffer_ = NULL;
  60     result_buffer_ = NULL;
  61     result_shm_offset_ = 0;
  62     ring_buffer_.reset();
  63     bytes_since_last_flush_ = 0;
  64   }
  65 }
  66
  67 bool TransferBuffer::HaveBuffer() const {
  68   DCHECK(buffer_id_ == -1 || buffer_);
  69   return buffer_id_ != -1;
  70 }
  71
  72 RingBuffer::Offset TransferBuffer::GetOffset(void* pointer) const {
  73   return ring_buffer_->GetOffset(pointer);
  74 }
  75
  76 void TransferBuffer::FreePendingToken(void* p, unsigned int token) {
  77   ring_buffer_->FreePendingToken(p, token);
  78   if (bytes_since_last_flush_ >= size_to_flush_ && size_to_flush_ > 0) {
  79     helper_->Flush();
  80     bytes_since_last_flush_ = 0;
  81   }
  82 }
  83
  84 void TransferBuffer::AllocateRingBuffer(unsigned int size) {
  85   for (;size >= min_buffer_size_; size /= 2) {
  86     int32 id = -1;
  87     scoped_refptr<gpu::Buffer> buffer =
  88         helper_->command_buffer()->CreateTransferBuffer(size, &id);
  89     if (id != -1) {
  90       DCHECK(buffer);
  91       buffer_ = buffer;
  92       ring_buffer_.reset(new RingBuffer(
  93           alignment_,
  94           result_size_,
  95           buffer_->size() - result_size_,
  96           helper_,
  97           static_cast<char*>(buffer_->memory()) + result_size_));
  98       buffer_id_ = id;
  99       result_buffer_ = buffer_->memory();
 100       result_shm_offset_ = 0;
 101       return;
 102     }
 103     // we failed so don't try larger than this.
 104     max_buffer_size_ = size / 2;
 105   }
 106   usable_ = false;
 107 }
 108
 109 static unsigned int ComputePOTSize(unsigned int dimension) {
 110   return (dimension == 0) ? 0 : 1 << base::bits::Log2Ceiling(dimension);
 111 }
 112
 113 void TransferBuffer::ReallocateRingBuffer(unsigned int size) {
 114   // What size buffer would we ask for if we needed a new one?
 115   unsigned int needed_buffer_size = ComputePOTSize(size + result_size_);
 116   needed_buffer_size = std::max(needed_buffer_size, min_buffer_size_);
 117   needed_buffer_size = std::max(needed_buffer_size, default_buffer_size_);
 118   needed_buffer_size = std::min(needed_buffer_size, max_buffer_size_);
 119
 120   if (usable_ && (!HaveBuffer() || needed_buffer_size > buffer_->size())) {
 121     if (HaveBuffer()) {
 122       Free();
 123     }
 124     AllocateRingBuffer(needed_buffer_size);
 125   }
 126 }
 127
 128 void* TransferBuffer::AllocUpTo(
 129     unsigned int size, unsigned int* size_allocated) {
 130   DCHECK(size_allocated);
 131
 132   ReallocateRingBuffer(size);
 133
 134   if (!HaveBuffer()) {
 135     return NULL;
 136   }
 137
 138   unsigned int max_size = ring_buffer_->GetLargestFreeOrPendingSize();
 139   *size_allocated = std::min(max_size, size);
 140   bytes_since_last_flush_ += *size_allocated;
 141   return ring_buffer_->Alloc(*size_allocated);
 142 }
 143
 144 void* TransferBuffer::Alloc(unsigned int size) {
 145   ReallocateRingBuffer(size);
 146
 147   if (!HaveBuffer()) {
 148     return NULL;
 149   }
 150
 151   unsigned int max_size = ring_buffer_->GetLargestFreeOrPendingSize();
 152   if (size > max_size) {
 153     return NULL;
 154   }
 155
 156   bytes_since_last_flush_ += size;
 157   return ring_buffer_->Alloc(size);
 158 }
 159
 160 void* TransferBuffer::GetResultBuffer() {
 161   ReallocateRingBuffer(result_size_);
 162   return result_buffer_;
 163 }
 164
 165 int TransferBuffer::GetResultOffset() {
 166   ReallocateRingBuffer(result_size_);
 167   return result_shm_offset_;
 168 }
 169
 170 int TransferBuffer::GetShmId() {
 171   ReallocateRingBuffer(result_size_);
 172   return buffer_id_;
 173 }
 174
 175 unsigned int TransferBuffer::GetCurrentMaxAllocationWithoutRealloc() const {
 176   return HaveBuffer() ? ring_buffer_->GetLargestFreeOrPendingSize() : 0;
 177 }
 178
 179 unsigned int TransferBuffer::GetMaxAllocation() const {
 180   return HaveBuffer() ? max_buffer_size_ - result_size_ : 0;
 181 }
 182
 183 void ScopedTransferBufferPtr::Release() {
 184   if (buffer_) {
 185     transfer_buffer_->FreePendingToken(buffer_, helper_->InsertToken());
 186     buffer_ = NULL;
 187     size_ = 0;
 188   }
 189 }
 190
 191 void ScopedTransferBufferPtr::Reset(unsigned int new_size) {
 192   Release();
 193   // NOTE: we allocate buffers of size 0 so that HaveBuffer will be true, so
 194   // that address will return a pointer just like malloc, and so that GetShmId
 195   // will be valid. That has the side effect that we'll insert a token on free.
 196   // We could add code skip the token for a zero size buffer but it doesn't seem
 197   // worth the complication.
 198   buffer_ = transfer_buffer_->AllocUpTo(new_size, &size_);
 199 }
 200
 201 }  // namespace gpu