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

chrome/browser/browser_main.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 "chrome/browser/browser_main.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 185 matching lines @@
 #endif
 
 #if defined(TOOLKIT_USES_GTK)
 #include "ui/gfx/gtk_util.h"
 #endif
 
 #if defined(TOUCH_UI) && defined(HAVE_XINPUT2)
 #include "views/touchui/touch_factory.h"
 #endif
 
+using net::internal::ClientSocketPoolBaseHelper;
+
 // BrowserMainParts ------------------------------------------------------------
 
 BrowserMainParts::BrowserMainParts(const MainFunctionParams& parameters)
     : parameters_(parameters),
       parsed_command_line_(parameters.command_line_) {
 }
 
 BrowserMainParts::~BrowserMainParts() {
 }
 
@@ skipping 267 matching lines @@
           "SSLFalseStart", kDivisor, "FalseStart_enabled", 2011, 7, 30));
 
   int disabled_group = trial->AppendGroup("FalseStart_disabled",
                                           falsestart_probability);
 
   int trial_grp = trial->group();
   if (trial_grp == disabled_group)
     net::SSLConfigService::DisableFalseStart();
 }
 
+// If --bytes-read-vs-last-accessed-alpha is not specified, run an A/B test for
+// choosing the warmest socket.
+void BrowserMainParts::WarmConnectionFieldTrial() {
+  const CommandLine& command_line = parsed_command_line();
+  if (command_line.HasSwitch(switches::kBytesReadVsLastAccessedAlpha)) {
+    std::string alpha_str = command_line.GetSwitchValueASCII(
+        switches::kBytesReadVsLastAccessedAlpha);
+    double alpha = 0;
+    base::StringToDouble(alpha_str, &alpha);
+    ClientSocketPoolBaseHelper::set_bytes_read_vs_last_accessed_alpha(alpha);
+    return;
+  }
+
+  const base::FieldTrial::Probability kWarmSocketDivisor = 100;
+  const base::FieldTrial::Probability kWarmSocketProbability = 33;  // 1% prob.
+
+  // After January 30, 2013 builds, it will always be in default group.
+  scoped_refptr<base::FieldTrial> warmest_socket_trial(
+      new base::FieldTrial(
+          "WarmSocketImpact", kWarmSocketDivisor, "last_accessed_socket",
+          2013, 1, 30));
+
+  // This (1000000) is the current default value. Having this group declared
+  // here makes it straightforward to modify |kWarmSocketProbability| such that
+  // the same probability value will be assigned to all the other groups, while
+  // preserving the remainder of the of probability space to the default value.
+  const int last_accessed_socket = warmest_socket_trial->kDefaultGroupNumber;
+  const int warmest_socket = warmest_socket_trial->AppendGroup(
+      "warmest_socket", kWarmSocketProbability);
+  const int warm_socket = warmest_socket_trial->AppendGroup(
+      "warm_socket", kWarmSocketProbability);
+
+  const int warmest_socket_trial_group = warmest_socket_trial->group();
+
+  if (warmest_socket_trial_group == last_accessed_socket) {
+    ClientSocketPoolBaseHelper::set_bytes_read_vs_last_accessed_alpha(1000000);
+  } else if (warmest_socket_trial_group == warmest_socket) {
+    ClientSocketPoolBaseHelper::set_bytes_read_vs_last_accessed_alpha(1);
+  } else if (warmest_socket_trial_group == warm_socket) {
+    // 1.83841629 = decay of 20 KB per 5 mins.
+    ClientSocketPoolBaseHelper::set_bytes_read_vs_last_accessed_alpha(
+        1.83841629);
+  } else {
+    NOTREACHED() << "Invalid bytes_read_vs_last_accessed_alpha";
+  }
+}
+
 
 // If neither --enable-connect-backup-jobs or --disable-connect-backup-jobs is
 // specified, run an A/B test for automatically establishing backup TCP
 // connections when a certain timeout value is exceeded.
 void BrowserMainParts::ConnectBackupJobsFieldTrial() {
   if (parsed_command_line().HasSwitch(switches::kEnableConnectBackupJobs)) {
     net::internal::ClientSocketPoolBaseHelper::set_connect_backup_jobs_enabled(
         true);
   } else if (parsed_command_line().HasSwitch(
         switches::kDisableConnectBackupJobs)) {
@@ skipping 101 matching lines @@
 
   // Note: make sure to call ConnectionFieldTrial() before
   // ProxyConnectionsFieldTrial().
   ConnectionFieldTrial();
   SocketTimeoutFieldTrial();
   ProxyConnectionsFieldTrial();
   prerender::ConfigurePrefetchAndPrerender(parsed_command_line());
   SpdyFieldTrial();
   ConnectBackupJobsFieldTrial();
   SSLFalseStartFieldTrial();
+  WarmConnectionFieldTrial();
 }
 
 // -----------------------------------------------------------------------------
 // TODO(viettrungluu): move more/rest of BrowserMain() into above structure
 
 namespace {
 
 // This function provides some ways to test crash and assertion handling
 // behavior of the program.
 void HandleTestParameters(const CommandLine& command_line) {
@@ skipping 1327 matching lines @@
 #if defined(OS_CHROMEOS)
   // To be precise, logout (browser shutdown) is not yet done, but the
   // remaining work is negligible, hence we say LogoutDone here.
   chromeos::BootTimesLoader::Get()->AddLogoutTimeMarker("LogoutDone",
                                                         false);
   chromeos::BootTimesLoader::Get()->WriteLogoutTimes();
 #endif
   TRACE_EVENT_END_ETW("BrowserMain", 0, 0);
   return result_code;
 }