gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/client/fenced_allocator.cc

 // Copyright (c) 2011 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.
 
 // This file contains the implementation of the FencedAllocator class.
 
 #include "gpu/command_buffer/client/fenced_allocator.h"
 
 #include <algorithm>
 
@@ skipping 16 matching lines @@
   return (size + (kAllocAlignment - 1)) & ~(kAllocAlignment - 1);
 }
 
 }  // namespace
 
 #ifndef _MSC_VER
 const FencedAllocator::Offset FencedAllocator::kInvalidOffset;
 #endif
 
 FencedAllocator::FencedAllocator(unsigned int size,
-                                 CommandBufferHelper *helper)
+                                 CommandBufferHelper* helper,
+                                 const base::Closure& poll_callback)
     : helper_(helper),
+      poll_callback_(poll_callback),
       bytes_in_use_(0) {
   Block block = { FREE, 0, RoundDown(size), kUnusedToken };
   blocks_.push_back(block);
 }
 
 FencedAllocator::~FencedAllocator() {
   // Free blocks pending tokens.
   for (unsigned int i = 0; i < blocks_.size(); ++i) {
     if (blocks_[i].state == FREE_PENDING_TOKEN) {
       i = WaitForTokenAndFreeBlock(i);
@@ skipping 147 matching lines @@
     BlockIndex index) {
   Block &block = blocks_[index];
   DCHECK_EQ(block.state, FREE_PENDING_TOKEN);
   helper_->WaitForToken(block.token);
   block.state = FREE;
   return CollapseFreeBlock(index);
 }
 
 // Frees any blocks pending a token for which the token has been read.
 void FencedAllocator::FreeUnused() {
-  int32 last_token_read = helper_->last_token_read();
+  // Free any potential blocks that has its lifetime handled outside.
+  poll_callback_.Run();
+
   for (unsigned int i = 0; i < blocks_.size();) {
     Block& block = blocks_[i];
-    if (block.state == FREE_PENDING_TOKEN && block.token <= last_token_read) {
+    if (block.state == FREE_PENDING_TOKEN &&
+        helper_->HasTokenPassed(block.token)) {
       block.state = FREE;
       i = CollapseFreeBlock(i);
     } else {
       ++i;
     }
   }
 }
 
 // If the block is exactly the requested size, simply mark it IN_USE, otherwise
 // split it and mark the first one (of the requested size) IN_USE.
@@ skipping 19 matching lines @@
 // The blocks are in offset order, so we can do a binary search.
 FencedAllocator::BlockIndex FencedAllocator::GetBlockByOffset(Offset offset) {
   Block templ = { IN_USE, offset, 0, kUnusedToken };
   Container::iterator it = std::lower_bound(blocks_.begin(), blocks_.end(),
                                             templ, OffsetCmp());
   DCHECK(it != blocks_.end() && it->offset == offset);
   return it-blocks_.begin();
 }
 
 }  // namespace gpu