Make transfer buffer reallocate at default size.

gpu/command_buffer/client/transfer_buffer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A class to Manage a growing transfer buffer.
 
 #include "../client/transfer_buffer.h"
 #include "../client/cmd_buffer_helper.h"
 
 namespace gpu {
 
 AlignedRingBuffer::~AlignedRingBuffer() {
 }
 
 TransferBuffer::TransferBuffer(
     CommandBufferHelper* helper)
     : helper_(helper),
       result_size_(0),
+      default_buffer_size_(0),
       min_buffer_size_(0),
       max_buffer_size_(0),
       alignment_(0),
       size_to_flush_(0),
       bytes_since_last_flush_(0),
       buffer_id_(-1),
       result_buffer_(NULL),
       result_shm_offset_(0),
       usable_(true) {
 }
 
 TransferBuffer::~TransferBuffer() {
   Free();
 }
 
 bool TransferBuffer::Initialize(
-    unsigned int starting_buffer_size,
+    unsigned int default_buffer_size,
     unsigned int result_size,
     unsigned int min_buffer_size,
     unsigned int max_buffer_size,
     unsigned int alignment,
     unsigned int size_to_flush) {
   result_size_ = result_size;
+  default_buffer_size_ = default_buffer_size;
   min_buffer_size_ = min_buffer_size;
   max_buffer_size_ = max_buffer_size;
   alignment_ = alignment;
   size_to_flush_ = size_to_flush;
-  ReallocateRingBuffer(starting_buffer_size - result_size);
+  ReallocateRingBuffer(default_buffer_size_ - result_size);

[vangelis, 2012/04/23 23:46:35]

Why do we subtract the result_size here?  

[greggman, 2012/04/24 20:04:46]

because the start of the buffer is reserved. I could change it to
default_buffer_size + result_size but it works this way now

   return HaveBuffer();
 }
 
 void TransferBuffer::Free() {
   if (HaveBuffer()) {
     helper_->Finish();
     helper_->command_buffer()->DestroyTransferBuffer(buffer_id_);
     buffer_id_ = -1;
     buffer_.ptr = NULL;
     buffer_.size = 0;
@@ skipping 72 matching lines @@
 }
 
 static unsigned int ComputePOTSize(unsigned int dimension) {
   return (dimension == 0) ? 0 : 1 << Log2Ceiling(dimension);
 }
 
 void TransferBuffer::ReallocateRingBuffer(unsigned int size) {
   // What size buffer would we ask for if we needed a new one?
   unsigned int needed_buffer_size = ComputePOTSize(size + result_size_);
   needed_buffer_size = std::max(needed_buffer_size, min_buffer_size_);
+  needed_buffer_size = std::max(needed_buffer_size, default_buffer_size_);
   needed_buffer_size = std::min(needed_buffer_size, max_buffer_size_);
 
   if (usable_ && (!HaveBuffer() || needed_buffer_size > buffer_.size)) {
     if (HaveBuffer()) {
       Free();
     }
     AllocateRingBuffer(needed_buffer_size);
   }
 }
 
@@ skipping 64 matching lines @@
   Release();
   // NOTE: we allocate buffers of size 0 so that HaveBuffer will be true, so
   // that address will return a pointer just like malloc, and so that GetShmId
   // will be valid. That has the side effect that we'll insert a token on free.
   // We could add code skip the token for a zero size buffer but it doesn't seem
   // worth the complication.
   buffer_ = transfer_buffer_->AllocUpTo(new_size, &size_);
 }
 
 }  // namespace gpu