Make CommandBuffer::Flush asynchronous, and add CommandBuffer::FlushSync with former semantics.

gpu/command_buffer/client/cmd_buffer_helper.cc

 // Copyright (c) 2009 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 command buffer helper class.
 
 #include "../client/cmd_buffer_helper.h"
 #include "../common/command_buffer.h"
 
 namespace gpu {
 
 CommandBufferHelper::CommandBufferHelper(CommandBuffer* command_buffer)
     : command_buffer_(command_buffer),
       entries_(NULL),
       total_entry_count_(0),
       usable_entry_count_(0),
       token_(0),
       last_token_read_(-1),
       get_(0),
-      put_(0) {
+      put_(0),
+      last_put_sent_(0) {
 }
 
 bool CommandBufferHelper::Initialize(int32 ring_buffer_size) {
   ring_buffer_ = command_buffer_->GetRingBuffer();
   if (!ring_buffer_.ptr)
     return false;
 
   CommandBuffer::State state = command_buffer_->GetState();
   entries_ = static_cast<CommandBufferEntry*>(ring_buffer_.ptr);
   int32 num_ring_buffer_entries = ring_buffer_size / sizeof(CommandBufferEntry);
   if (num_ring_buffer_entries > state.num_entries) {
     return false;
   }
 
   const int32 kJumpEntries =
       sizeof(cmd::Jump) / sizeof(*entries_);  // NOLINT
 
   total_entry_count_ = num_ring_buffer_entries;
   usable_entry_count_ = total_entry_count_ - kJumpEntries;
   put_ = state.put_offset;
   SynchronizeState(state);
   return true;
 }
 
 CommandBufferHelper::~CommandBufferHelper() {
 }
 
-bool CommandBufferHelper::Flush() {
-  CommandBuffer::State state = command_buffer_->Flush(put_);
+bool CommandBufferHelper::FlushSync() {
+  last_put_sent_ = put_;
+  CommandBuffer::State state = command_buffer_->FlushSync(put_);
   SynchronizeState(state);
   return state.error == error::kNoError;
 }
 
+void CommandBufferHelper::Flush() {
+  last_put_sent_ = put_;
+  command_buffer_->Flush(put_);
+}
+
 // Calls Flush() and then waits until the buffer is empty. Break early if the
 // error is set.
 bool CommandBufferHelper::Finish() {
   do {
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return false;
   } while (put_ != get_);
 
   return true;
 }
 
 // Inserts a new token into the command stream. It uses an increasing value
 // scheme so that we don't lose tokens (a token has passed if the current token
 // value is higher than that token). Calls Finish() if the token value wraps,
 // which will be rare.
@@ skipping 10 matching lines @@
   }
   return token_;
 }
 
 // Waits until the current token value is greater or equal to the value passed
 // in argument.
 void CommandBufferHelper::WaitForToken(int32 token) {
   // Return immediately if corresponding InsertToken failed.
   if (token < 0)
     return;
-  if (last_token_read_ >= token) return;  // fast path.
   if (token > token_) return;  // we wrapped
-  Flush();
   while (last_token_read_ < token) {
     if (get_ == put_) {
       GPU_LOG(FATAL) << "Empty command buffer while waiting on a token.";
       return;
     }
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return;
   }
 }
 
 // Waits for available entries, basically waiting until get >= put + count + 1.
 // It actually waits for contiguous entries, so it may need to wrap the buffer
 // around, adding a jump. Thus this function may change the value of put_. The
 // function will return early if an error occurs, in which case the available
 // space may not be available.
 void CommandBufferHelper::WaitForAvailableEntries(int32 count) {
   GPU_CHECK(count < usable_entry_count_);
   if (put_ + count > usable_entry_count_) {
     // There's not enough room between the current put and the end of the
     // buffer, so we need to wrap. We will add a jump back to the start, but we
     // need to make sure get wraps first, actually that get is 1 or more (since
     // put will wrap to 0 after we add the jump).
     GPU_DCHECK_LE(1, put_);
-    Flush();
     while (get_ > put_ || get_ == 0) {
       // Do not loop forever if the flush fails, meaning the command buffer
       // reader has shutdown.
-      if (!Flush())
+      if (!FlushSync())
         return;
     }
     // Insert a jump back to the beginning.
     cmd::Jump::Set(&entries_[put_], 0);
     put_ = 0;
   }
-  // If we have enough room, return immediatly.
-  if (count <= AvailableEntries()) return;
-  // Otherwise flush, and wait until we do have enough room.
-  Flush();
   while (AvailableEntries() < count) {
     // Do not loop forever if the flush fails, meaning the command buffer reader
     // has shutdown.
-    if (!Flush())
+    if (!FlushSync())
       return;
   }
+  // Force a flush if the buffer is getting half full, or even earlier if the
+  // reader is know to be idle.

[apatrick_chromium, 2011/01/14 22:43:32]

know -> known

[Antoine Labour, 2011/01/14 23:17:28]

Done.

+  int32 pending =
+      (put_ + usable_entry_count_ - last_put_sent_) % usable_entry_count_;
+  int32 limit = usable_entry_count_ / ((get_ == last_put_sent_) ? 16 : 2);
+  if (pending > limit) {
+    Flush();
+  }
 }
 
 CommandBufferEntry* CommandBufferHelper::GetSpace(uint32 entries) {
   WaitForAvailableEntries(entries);
   CommandBufferEntry* space = &entries_[put_];
   put_ += entries;
   GPU_DCHECK_LE(put_, usable_entry_count_);
   if (put_ == usable_entry_count_) {
     cmd::Jump::Set(&entries_[put_], 0);
     put_ = 0;
   }
   return space;
 }
 
 error::Error CommandBufferHelper::GetError() {
   CommandBuffer::State state = command_buffer_->GetState();
   SynchronizeState(state);
   return static_cast<error::Error>(state.error);
 }
 
 void CommandBufferHelper::SynchronizeState(CommandBuffer::State state) {
   get_ = state.get_offset;
   last_token_read_ = state.token;
 }
 
 }  // namespace gpu