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

net/http/http_basic_stream.cc

Index: net/http/http_basic_stream.cc
===================================================================
--- net/http/http_basic_stream.cc	(revision 90217)
+++ net/http/http_basic_stream.cc	(working copy)
@@ -4,6 +4,8 @@
 
 #include "net/http/http_basic_stream.h"
 
+#include "base/format_macros.h"
+#include "base/metrics/histogram.h"
 #include "base/stringprintf.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
@@ -12,6 +14,7 @@
 #include "net/http/http_stream_parser.h"
 #include "net/http/http_util.h"
 #include "net/socket/client_socket_handle.h"
+#include "net/socket/client_socket_pool_base.h"
 
 namespace net {
 
@@ -34,6 +37,7 @@
   request_info_ = request_info;
   parser_.reset(new HttpStreamParser(connection_.get(), request_info,
                                      read_buf_, net_log));
+  bytes_read_offset_ = connection_->socket()->NumBytesRead();
   return OK;
 }
 
@@ -50,6 +54,7 @@
   request_line_ = base::StringPrintf("%s %s HTTP/1.1\r\n",
                                      request_info_->method.c_str(),
                                      path.c_str());
+  response_ = response;
   return parser_->SendRequest(request_line_, headers, request_body, response,
                               callback);
 }
@@ -119,4 +124,45 @@
   return false;
 }
 
+void HttpBasicStream::LogNumRttVsBytesMetrics() const {
+  int socket_reuse_policy = GetSocketReusePolicy();
+  if (socket_reuse_policy > 2 || socket_reuse_policy < 0) {
+    LOG(ERROR) << "Invalid socket reuse policy";
+    return;
+  }
+
+  int64 total_bytes_read = connection_->socket()->NumBytesRead();
+  int64 bytes_received = total_bytes_read - bytes_read_offset_;
+  int64 num_kb = bytes_received / 1024;
+  double rtt = connection_->socket()->GetConnectTimeMicros().ToInternalValue();
+  rtt /= 1000.0;
+
+  if (num_kb < 1024 && rtt > 0) {  // Ignore responses > 1MB
+    base::TimeDelta duration = base::Time::Now() -
+                               response_->request_time;
+    double num_rtt = static_cast<double>(duration.InMilliseconds()) / rtt;
+    int64 num_rtt_scaled = (4 * num_rtt);
+
+    static const char* const kGroups[] = {
+      "warmest_socket", "warm_socket", "last_accessed_socket"
+    };
+    int bucket = (num_kb / 5) * 5;
+    const std::string histogram(StringPrintf("Net.Num_RTT_vs_KB_%s_%dKB",
+                                             kGroups[socket_reuse_policy],
+                                             bucket));
+    base::Histogram* counter = base::Histogram::FactoryGet(
+        histogram, 0, 1000, 2, base::Histogram::kUmaTargetedHistogramFlag);
+    DCHECK_EQ(histogram, counter->histogram_name());
+    counter->Add(num_rtt_scaled);
+
+    VLOG(2) << StringPrintf("%s\nrtt = %f\tnum_rtt = %f\t"
+                            "num_kb = %" PRId64 "\t"
+                            "total bytes = %" PRId64 "\t"
+                            "histogram = %s",
+                            request_line_.data(),
+                            rtt, num_rtt, num_kb, total_bytes_read,
+                            histogram.data());
+  }
+}
+
 }  // namespace net