Deciding best connection to schedule requests on based on cwnd and idle time

net/socket/tcp_client_socket_libevent.cc

Index: net/socket/tcp_client_socket_libevent.cc
===================================================================
--- net/socket/tcp_client_socket_libevent.cc	(revision 88319)
+++ net/socket/tcp_client_socket_libevent.cc	(working copy)
@@ -142,7 +142,10 @@
       net_log_(BoundNetLog::Make(net_log, NetLog::SOURCE_SOCKET)),
       previously_disconnected_(false),
       use_tcp_fastopen_(false),
-      tcp_fastopen_connected_(false) {
+      tcp_fastopen_connected_(false),
+      connect_start_time_(),

[willchan no longer on Chromium, 2011/06/09 15:08:54]

No need to explicitly invoke the empty constructor, it'll do so automatically
anyway.

[Gagan, 2011/06/09 19:49:26]

Done.

+      num_bytes_read_(0),
+      rtt_ms_(0) {
   scoped_refptr<NetLog::EventParameters> params;
   if (source.is_valid())
     params = new NetLogSourceParameter("source_dependency", source);
@@ -303,6 +306,7 @@
 
   // Connect the socket.
   if (!use_tcp_fastopen_) {
+    connect_start_time_ = base::Time::Now();
     if (!HANDLE_EINTR(connect(socket_, current_ai_->ai_addr,
                               static_cast<int>(current_ai_->ai_addrlen)))) {
       // Connected without waiting!
@@ -344,6 +348,9 @@
   write_socket_watcher_.StopWatchingFileDescriptor();
 
   if (result == OK) {
+    rtt_ms_ = static_cast<double>((base::Time::Now() -

[willchan no longer on Chromium, 2011/06/09 15:08:54]

Why is this kept as a double? Seems better to use an int. It can be converted
where used if needed.

Also, for Linux, why are we calculating this instead of using TCP_INFO
(http://linuxgazette.net/136/pfeiffer.html)?

[Gagan, 2011/06/09 19:49:26]

Initially i chose double because i didn't want to add special handling for rtt's
< 1 ms
Besides, i think rtt is usually measured at higher granularity than integer
number of milliseconds. Ping shows it to 3 decimal places.
If you want i could change the function to GetRttInMicros().

Macosx also seems to be using this file., and i couldn't find an easy of getting
rtt. I think tcp_info is linux specific,  on mac /usr/include/netinet/tcp.h
doesnt have TCP_INFO.

+                                   connect_start_time_).InMicroseconds())
+        / 1000.0;
     use_history_.set_was_ever_connected();
     return OK;  // Done!
   }
@@ -430,9 +437,12 @@
   DCHECK_GT(buf_len, 0);
 
   int nread = HANDLE_EINTR(read(socket_, buf->data(), buf_len));
+  LOG(ERROR) << "this = " << (int*) this << "\tnread = " << nread;

[Mike Belshe, 2011/06/09 16:08:52]

nit: please remove the debugging lines.

[Gagan, 2011/06/09 19:49:26]

Will remove in the last round.
For now, please accomodate the few extra lines. They are extremely helpful in
tracking sockets when something goes wrong.

[Gagan, 2011/06/14 18:25:02]

Removed.

   if (nread >= 0) {
     base::StatsCounter read_bytes("tcp.read_bytes");
     read_bytes.Add(nread);
+    num_bytes_read_ += static_cast<int64>(nread);
+    LOG(ERROR) << "this = " << (int*) this << "\tRead " << nread;
     if (nread > 0)
       use_history_.set_was_used_to_convey_data();
     net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, nread,
@@ -451,6 +461,7 @@
     return MapSystemError(errno);
   }
 
+  LOG(ERROR) << "this = " << (int*) this << "\tread_buf_len_ = " << read_buf_len_;
   read_buf_ = buf;
   read_buf_len_ = buf_len;
   read_callback_ = callback;
@@ -627,6 +638,8 @@
     result = bytes_transferred;
     base::StatsCounter read_bytes("tcp.read_bytes");
     read_bytes.Add(bytes_transferred);
+    num_bytes_read_ += static_cast<int64>(bytes_transferred);
+    LOG(ERROR) << "this = " << (int*) this << "\tRead " << bytes_transferred;
     if (bytes_transferred > 0)
       use_history_.set_was_used_to_convey_data();
     net_log_.AddByteTransferEvent(NetLog::TYPE_SOCKET_BYTES_RECEIVED, result,