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

net/http/http_network_transaction.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.
 
 #include "net/http/http_network_transaction.h"
 
 #include <set>
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 1057 matching lines @@
 
   UMA_HISTOGRAM_LONG_TIMES("Net.Transaction_Latency", duration);
   UMA_HISTOGRAM_CLIPPED_TIMES("Net.Transaction_Latency_Under_10", duration,
                               base::TimeDelta::FromMilliseconds(1),
                               base::TimeDelta::FromMinutes(10),
                               100);
   UMA_HISTOGRAM_CLIPPED_TIMES("Net.Transaction_Latency_Total_Under_10",
                               total_duration,
                               base::TimeDelta::FromMilliseconds(1),
                               base::TimeDelta::FromMinutes(10), 100);
+
+  int num_kb = stream_->GetBytesReceived() / 1024;

[willchan no longer on Chromium, 2011/06/06 10:57:36]

I think the way you have this structured isn't what you want. This stats are
sort of meaningless for SPDY since we will only be using one connection. Why
don't you add a LogRTTMetrics or something to the HttpStream interface instead
of exposing accessors. Then for HttpBasicStream, do this logic. For
SpdyHttpStream, where it doesn't matter, don't do anything.

[Gagan, 2011/06/06 20:27:10]

Good point.
Done.

+  if (num_kb < 1024 && stream_->GetRTTMs() > 0) {  // Ignore responses > 1MB
+    double num_rtt = static_cast<double>(duration.InMilliseconds()) /
+        stream_->GetRTTMs();
+    int num_rtt_scaled = (4 * num_rtt);
+    int val = 1024 * num_rtt_scaled + num_kb;  // Supports ~500 RTT of 1418 B.
+    HISTOGRAM_CUSTOM_COUNTS("Net.RTT_vs_KB", val, 4096, 3048000, 1000);
+    LOG(ERROR) << "rtt = " << stream_->GetRTTMs() << "\tnum_rtt = " << num_rtt
+               << "\tnum_kb = " << num_kb << "\tval = " << val;
+  }
+
   if (!stream_->IsConnectionReused()) {
     UMA_HISTOGRAM_CLIPPED_TIMES(
         "Net.Transaction_Latency_Total_New_Connection_Under_10",
         total_duration, base::TimeDelta::FromMilliseconds(1),
         base::TimeDelta::FromMinutes(10), 100);
   }
 }
 
 int HttpNetworkTransaction::HandleCertificateRequest(int error) {
   // There are two paths through which the server can request a certificate
@@ skipping 253 matching lines @@
       description = base::StringPrintf("Unknown state 0x%08X (%u)", state,
                                        state);
       break;
   }
   return description;
 }
 
 #undef STATE_CASE
 
 }  // namespace net