Switch the TCP reads on Windows to use non-blocking/non-async I/O.

net/socket/tcp_client_socket_win.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.
 
 #include "net/socket/tcp_client_socket_win.h"
 
 #include <mstcpip.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ skipping 170 matching lines @@
 
   // The TCPClientSocketWin is going away.
   void Detach() { socket_ = NULL; }
 
   // The separate OVERLAPPED variables for asynchronous operation.
   // |read_overlapped_| is used for both Connect() and Read().
   // |write_overlapped_| is only used for Write();
   OVERLAPPED read_overlapped_;
   OVERLAPPED write_overlapped_;
 
+  // Flag indicating if we are in the experiment that enables non-blocking read
+  static bool disable_overlapped_reads_;

[Ryan Sleevi, 2012/10/11 18:53:16]

No need to make this a class static. Just have it be a bool in an unnamed
namespace in the current translation unit (eg: Line 31)

It should follow the Chromium global naming style (g_disable_overlapped_reads)

+
   // The buffers used in Read() and Write().
   scoped_refptr<IOBuffer> read_iobuffer_;
   scoped_refptr<IOBuffer> write_iobuffer_;
+  int read_buffer_length_;
   int write_buffer_length_;
 
   // Throttle the read size based on our current slow start state.
   // Returns the throttled read size.
   int ThrottleReadSize(int size) {
     if (slow_start_throttle_ < kMaxSlowStartThrottle) {
       size = std::min(size, slow_start_throttle_);
       slow_start_throttle_ *= 2;
     }
     return size;
@@ skipping 44 matching lines @@
   // When doing reads from the socket, we try to mirror TCP's slow start.
   // We do this because otherwise the async IO subsystem artifically delays
   // returning data to the application.
   static const int kInitialSlowStartThrottle = 1 * 1024;
   static const int kMaxSlowStartThrottle = 32 * kInitialSlowStartThrottle;
   int slow_start_throttle_;
 
   DISALLOW_COPY_AND_ASSIGN(Core);
 };
 
+bool TCPClientSocketWin::Core::disable_overlapped_reads_ = false;
+
 TCPClientSocketWin::Core::Core(
     TCPClientSocketWin* socket)
     : write_buffer_length_(0),
+      read_buffer_length_(0),
       socket_(socket),
       ALLOW_THIS_IN_INITIALIZER_LIST(reader_(this)),
       ALLOW_THIS_IN_INITIALIZER_LIST(writer_(this)),
       slow_start_throttle_(kInitialSlowStartThrottle) {
   memset(&read_overlapped_, 0, sizeof(read_overlapped_));
   memset(&write_overlapped_, 0, sizeof(write_overlapped_));
 
   read_overlapped_.hEvent = WSACreateEvent();
   write_overlapped_.hEvent = WSACreateEvent();
 }
@@ skipping 23 matching lines @@
   write_watcher_.StartWatching(write_overlapped_.hEvent, &writer_);
 }
 
 void TCPClientSocketWin::Core::ReadDelegate::OnObjectSignaled(
     HANDLE object) {
   DCHECK_EQ(object, core_->read_overlapped_.hEvent);
   if (core_->socket_) {
     if (core_->socket_->waiting_connect()) {
       core_->socket_->DidCompleteConnect();
     } else {
-      core_->socket_->DidCompleteRead();
+      if (disable_overlapped_reads_) {
+        core_->socket_->DidSignalRead();
+      } else {
+        core_->socket_->DidCompleteRead();
+      }
     }
   }
 
   core_->Release();
 }
 
 void TCPClientSocketWin::Core::WriteDelegate::OnObjectSignaled(
     HANDLE object) {
   DCHECK_EQ(object, core_->write_overlapped_.hEvent);
   if (core_->socket_)
@@ skipping 32 matching lines @@
   DCHECK_EQ(socket_, INVALID_SOCKET);
 
   int error = SetupSocket(socket);
   if (error)
     return MapSystemError(error);
 
   socket_ = socket;
   SetNonBlocking(socket_);
 
   core_ = new Core(this);
+  if (core_->disable_overlapped_reads_) {
+    WSAEventSelect(socket_, core_->read_overlapped_.hEvent,
+                   FD_READ | FD_CLOSE);
+  }
 
   current_address_index_ = 0;
   use_history_.set_was_ever_connected();
 
   return OK;
 }
 
 int TCPClientSocketWin::Bind(const IPEndPoint& address) {
   if (current_address_index_ >= 0 || bind_address_.get()) {
     // Cannot bind the socket if we are already connected or connecting.
@@ skipping 111 matching lines @@
         return ERR_INVALID_ARGUMENT;
       if (bind(socket_, storage.addr, storage.addr_len))
         return MapSystemError(errno);
     }
   }
 
   DCHECK(!core_);
   core_ = new Core(this);
   // WSAEventSelect sets the socket to non-blocking mode as a side effect.
   // Our connect() and recv() calls require that the socket be non-blocking.
-  WSAEventSelect(socket_, core_->read_overlapped_.hEvent, FD_CONNECT);
+  if (core_->disable_overlapped_reads_) {
+    WSAEventSelect(socket_, core_->read_overlapped_.hEvent,
+                   FD_CONNECT | FD_READ | FD_CLOSE);
+  } else {
+    WSAEventSelect(socket_, core_->read_overlapped_.hEvent, FD_CONNECT);
+  }
 
   SockaddrStorage storage;
   if (!endpoint.ToSockAddr(storage.addr, &storage.addr_len))
     return ERR_INVALID_ARGUMENT;
   connect_start_time_ = base::TimeTicks::Now();
   if (!connect(socket_, storage.addr, storage.addr_len)) {
     // Connected without waiting!
     //
     // The MSDN page for connect says:
     //   With a nonblocking socket, the connection attempt cannot be completed
@@ skipping 205 matching lines @@
 
 int TCPClientSocketWin::Read(IOBuffer* buf,
                              int buf_len,
                              const CompletionCallback& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(socket_, INVALID_SOCKET);
   DCHECK(!waiting_read_);
   DCHECK(read_callback_.is_null());
   DCHECK(!core_->read_iobuffer_);
 
-  buf_len = core_->ThrottleReadSize(buf_len);
-
-  WSABUF read_buffer;
-  read_buffer.len = buf_len;
-  read_buffer.buf = buf->data();
-
-  // TODO(wtc): Remove the assertion after enough testing.
-  AssertEventNotSignaled(core_->read_overlapped_.hEvent);
-  DWORD num, flags = 0;
-  int rv = WSARecv(socket_, &read_buffer, 1, &num, &flags,
-                   &core_->read_overlapped_, NULL);
-  if (rv == 0) {
-    if (ResetEventIfSignaled(core_->read_overlapped_.hEvent)) {
+  if (core_->disable_overlapped_reads_) {
+    int flags = 0;
+    int rv = recv(socket_, buf->data(), buf_len, flags);
+    if (rv == SOCKET_ERROR) {
+      int os_error = WSAGetLastError();
+      if (os_error != WSAEWOULDBLOCK) {
+        int net_error = MapSystemError(os_error);
+        net_log_.AddEvent(NetLog::TYPE_SOCKET_READ_ERROR,
+                         CreateNetLogSocketErrorCallback(net_error, os_error));
+        return net_error;
+      }
+    } else {
       base::StatsCounter read_bytes("tcp.read_bytes");
-      read_bytes.Add(num);
-      num_bytes_read_ += num;
-      if (num > 0)
+      if (rv > 0) {
         use_history_.set_was_used_to_convey_data();
-      net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, num,
+        read_bytes.Add(rv);
+        num_bytes_read_ += rv;
+      }
+      net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, rv,
                                     buf->data());
-      return static_cast<int>(num);
+      return rv;
     }
   } else {
-    int os_error = WSAGetLastError();
-    if (os_error != WSA_IO_PENDING) {
-      int net_error = MapSystemError(os_error);
-      net_log_.AddEvent(NetLog::TYPE_SOCKET_READ_ERROR,
-                        CreateNetLogSocketErrorCallback(net_error, os_error));
-      return net_error;
+    buf_len = core_->ThrottleReadSize(buf_len);
+
+    WSABUF read_buffer;
+    read_buffer.len = buf_len;
+    read_buffer.buf = buf->data();
+
+    // TODO(wtc): Remove the assertion after enough testing.
+    AssertEventNotSignaled(core_->read_overlapped_.hEvent);
+    DWORD num, flags = 0;
+    int rv = WSARecv(socket_, &read_buffer, 1, &num, &flags,
+                     &core_->read_overlapped_, NULL);
+    if (rv == 0) {
+      if (ResetEventIfSignaled(core_->read_overlapped_.hEvent)) {
+        base::StatsCounter read_bytes("tcp.read_bytes");
+        read_bytes.Add(num);
+        num_bytes_read_ += num;
+        if (num > 0)
+          use_history_.set_was_used_to_convey_data();
+        net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, num,
+                                      buf->data());
+        return static_cast<int>(num);
+      }
+    } else {
+      int os_error = WSAGetLastError();
+      if (os_error != WSA_IO_PENDING) {
+        int net_error = MapSystemError(os_error);
+        net_log_.AddEvent(NetLog::TYPE_SOCKET_READ_ERROR,
+                         CreateNetLogSocketErrorCallback(net_error, os_error));
+        return net_error;
+      }
     }
   }
-  core_->WatchForRead();
+
   waiting_read_ = true;
   read_callback_ = callback;
   core_->read_iobuffer_ = buf;
+  core_->read_buffer_length_ = buf_len;
+  core_->WatchForRead();
   return ERR_IO_PENDING;
 }
 
 int TCPClientSocketWin::Write(IOBuffer* buf,
                               int buf_len,
                               const CompletionCallback& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(socket_, INVALID_SOCKET);
   DCHECK(!waiting_write_);
   DCHECK(write_callback_.is_null());
   DCHECK_GT(buf_len, 0);
   DCHECK(!core_->write_iobuffer_);
 
   base::StatsCounter writes("tcp.writes");
   writes.Increment();
 
   WSABUF write_buffer;
   write_buffer.len = buf_len;
   write_buffer.buf = buf->data();
-  core_->write_buffer_length_ = buf_len;
 
   // TODO(wtc): Remove the assertion after enough testing.
   AssertEventNotSignaled(core_->write_overlapped_.hEvent);
   DWORD num;
   int rv = WSASend(socket_, &write_buffer, 1, &num, 0,
                    &core_->write_overlapped_, NULL);
   if (rv == 0) {
     if (ResetEventIfSignaled(core_->write_overlapped_.hEvent)) {
       rv = static_cast<int>(num);
       if (rv > buf_len || rv < 0) {
@@ skipping 13 matching lines @@
     }
   } else {
     int os_error = WSAGetLastError();
     if (os_error != WSA_IO_PENDING) {
       int net_error = MapSystemError(os_error);
       net_log_.AddEvent(NetLog::TYPE_SOCKET_WRITE_ERROR,
                         CreateNetLogSocketErrorCallback(net_error, os_error));
       return net_error;
     }
   }
-  core_->WatchForWrite();
   waiting_write_ = true;
   write_callback_ = callback;
   core_->write_iobuffer_ = buf;
+  core_->write_buffer_length_ = buf_len;
+  core_->WatchForWrite();
   return ERR_IO_PENDING;
 }
 
 bool TCPClientSocketWin::SetReceiveBufferSize(int32 size) {
   DCHECK(CalledOnValidThread());
   return SetSocketReceiveBufferSize(socket_, size);
 }
 
 bool TCPClientSocketWin::SetSendBufferSize(int32 size) {
   DCHECK(CalledOnValidThread());
@@ skipping 77 matching lines @@
   }
 
   connect_os_error_ = os_error;
   rv = DoConnectLoop(result);
   if (rv != ERR_IO_PENDING) {
     LogConnectCompletion(rv);
     DoReadCallback(rv);
   }
 }
 
+void TCPClientSocketWin::DidSignalRead() {
+  DCHECK(waiting_read_);
+  int rv;
+  int os_error = 0, flags = 0;
+  WSANETWORKEVENTS network_events;
+  rv = WSAEnumNetworkEvents(socket_, core_->read_overlapped_.hEvent,
+                              &network_events);
+  if (rv != SOCKET_ERROR) {
+    if (network_events.lNetworkEvents & FD_READ) {
+      rv = recv(socket_, core_->read_iobuffer_->data(),
+                core_->read_buffer_length_, flags);
+      if (rv == SOCKET_ERROR) {
+        os_error = WSAGetLastError();
+        if (os_error == WSAEWOULDBLOCK) {
+          core_->WatchForRead();
+          return;
+        } else {
+          rv = MapSystemError(os_error);
+        }
+      }
+    } else {
+      core_->WatchForRead();
+      return;
+    }
+  } else {
+    os_error = WSAGetLastError();
+    rv = MapSystemError(os_error);
+  }
+  if (rv > 0) {
+      base::StatsCounter read_bytes("tcp.read_bytes");
+      if (rv > 0) {
+        use_history_.set_was_used_to_convey_data();
+        read_bytes.Add(rv);
+        num_bytes_read_ += rv;
+      }
+      net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, rv,
+                                    core_->read_iobuffer_->data());
+  } else {
+    rv = MapSystemError(os_error);
+    net_log_.AddEvent(NetLog::TYPE_SOCKET_READ_ERROR,
+                      CreateNetLogSocketErrorCallback(rv, os_error));
+  }
+  waiting_read_ = false;
+  core_->read_iobuffer_ = NULL;
+  core_->read_buffer_length_ = 0;
+  DoReadCallback(rv);
+}
+
 void TCPClientSocketWin::DidCompleteRead() {
   DCHECK(waiting_read_);
   DWORD num_bytes, flags;
   BOOL ok = WSAGetOverlappedResult(socket_, &core_->read_overlapped_,
                                    &num_bytes, FALSE, &flags);
   WSAResetEvent(core_->read_overlapped_.hEvent);
   waiting_read_ = false;
   int rv;
   if (ok) {
     base::StatsCounter read_bytes("tcp.read_bytes");
@@ skipping 43 matching lines @@
       if (num_bytes > 0)
         use_history_.set_was_used_to_convey_data();
       net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_SENT, num_bytes,
                                     core_->write_iobuffer_->data());
     }
   }
   core_->write_iobuffer_ = NULL;
   DoWriteCallback(rv);
 }
 
+void TCPClientSocketWin::DisableOverlappedReads() {
+  TCPClientSocketWin::Core::disable_overlapped_reads_ = true;
+}
+
 }  // namespace net