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/logging.h"
  11 #include "base/trace_event/trace_event.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_.get());
  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::DiscardBlock(void* p) {
  77   ring_buffer_->DiscardBlock(p);
  78 }
  79
  80 void TransferBuffer::FreePendingToken(void* p, unsigned int token) {
  81   ring_buffer_->FreePendingToken(p, token);
  82   if (bytes_since_last_flush_ >= size_to_flush_ && size_to_flush_ > 0) {
  83     helper_->Flush();
  84     bytes_since_last_flush_ = 0;
  85   }
  86 }
  87
  88 void TransferBuffer::AllocateRingBuffer(unsigned int size) {
  89   for (;size >= min_buffer_size_; size /= 2) {
  90     int32 id = -1;
  91     scoped_refptr<gpu::Buffer> buffer =
  92         helper_->command_buffer()->CreateTransferBuffer(size, &id);
  93     if (id != -1) {
  94       DCHECK(buffer.get());
  95       buffer_ = buffer;
  96       ring_buffer_.reset(new RingBuffer(
  97           alignment_,
  98           result_size_,
  99           buffer_->size() - result_size_,
 100           helper_,
 101           static_cast<char*>(buffer_->memory()) + result_size_));
 102       buffer_id_ = id;
 103       result_buffer_ = buffer_->memory();
 104       result_shm_offset_ = 0;
 105       return;
 106     }
 107     // we failed so don't try larger than this.
 108     max_buffer_size_ = size / 2;
 109   }
 110   usable_ = false;
 111 }
 112
 113 static unsigned int ComputePOTSize(unsigned int dimension) {
 114   return (dimension == 0) ? 0 : 1 << base::bits::Log2Ceiling(dimension);
 115 }
 116
 117 void TransferBuffer::ReallocateRingBuffer(unsigned int size) {
 118   // What size buffer would we ask for if we needed a new one?
 119   unsigned int needed_buffer_size = ComputePOTSize(size + result_size_);
 120   needed_buffer_size = std::max(needed_buffer_size, min_buffer_size_);
 121   needed_buffer_size = std::max(needed_buffer_size, default_buffer_size_);
 122   needed_buffer_size = std::min(needed_buffer_size, max_buffer_size_);
 123
 124   if (usable_ && (!HaveBuffer() || needed_buffer_size > buffer_->size())) {
 125     if (HaveBuffer()) {
 126       Free();
 127     }
 128     AllocateRingBuffer(needed_buffer_size);
 129   }
 130 }
 131
 132 void* TransferBuffer::AllocUpTo(
 133     unsigned int size, unsigned int* size_allocated) {
 134   DCHECK(size_allocated);
 135
 136   ReallocateRingBuffer(size);
 137
 138   if (!HaveBuffer()) {
 139     return NULL;
 140   }
 141
 142   unsigned int max_size = ring_buffer_->GetLargestFreeOrPendingSize();
 143   *size_allocated = std::min(max_size, size);
 144   bytes_since_last_flush_ += *size_allocated;
 145   return ring_buffer_->Alloc(*size_allocated);
 146 }
 147
 148 void* TransferBuffer::Alloc(unsigned int size) {
 149   ReallocateRingBuffer(size);
 150
 151   if (!HaveBuffer()) {
 152     return NULL;
 153   }
 154
 155   unsigned int max_size = ring_buffer_->GetLargestFreeOrPendingSize();
 156   if (size > max_size) {
 157     return NULL;
 158   }
 159
 160   bytes_since_last_flush_ += size;
 161   return ring_buffer_->Alloc(size);
 162 }
 163
 164 void* TransferBuffer::GetResultBuffer() {
 165   ReallocateRingBuffer(result_size_);
 166   return result_buffer_;
 167 }
 168
 169 int TransferBuffer::GetResultOffset() {
 170   ReallocateRingBuffer(result_size_);
 171   return result_shm_offset_;
 172 }
 173
 174 int TransferBuffer::GetShmId() {
 175   ReallocateRingBuffer(result_size_);
 176   return buffer_id_;
 177 }
 178
 179 unsigned int TransferBuffer::GetCurrentMaxAllocationWithoutRealloc() const {
 180   return HaveBuffer() ? ring_buffer_->GetLargestFreeOrPendingSize() : 0;
 181 }
 182
 183 unsigned int TransferBuffer::GetMaxAllocation() const {
 184   return HaveBuffer() ? max_buffer_size_ - result_size_ : 0;
 185 }
 186
 187 void ScopedTransferBufferPtr::Release() {
 188   if (buffer_) {
 189     transfer_buffer_->FreePendingToken(buffer_, helper_->InsertToken());
 190     buffer_ = NULL;
 191     size_ = 0;
 192   }
 193 }
 194
 195 void ScopedTransferBufferPtr::Discard() {
 196   if (buffer_) {
 197     transfer_buffer_->DiscardBlock(buffer_);
 198     buffer_ = NULL;
 199     size_ = 0;
 200   }
 201 }
 202
 203 void ScopedTransferBufferPtr::Reset(unsigned int new_size) {
 204   Release();
 205   // NOTE: we allocate buffers of size 0 so that HaveBuffer will be true, so
 206   // that address will return a pointer just like malloc, and so that GetShmId
 207   // will be valid. That has the side effect that we'll insert a token on free.
 208   // We could add code skip the token for a zero size buffer but it doesn't seem
 209   // worth the complication.
 210   buffer_ = transfer_buffer_->AllocUpTo(new_size, &size_);
 211 }
 212
 213 }  // namespace gpu