DNS prefetch experiment extension: Consider different connection count limits

This CL both enables selection of a run-time selected limit
on the number of connections to a single host, and varies
that limit to see how it relates to DNS prefetch latency
in connections.

r=wtc
Review URL: http://codereview.chromium.org/62083

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@13339 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 31 insertions, 6 deletions

diff --git a/net/http/http_network_session.cc b/net/http/http_network_session.cc
new file mode 100644
index 0000000..a498ed0
--- /dev/null
+++ b/net/http/http_network_session.cc
@@ -0,0 +1,22 @@
+// Copyright (c) 2009 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_session.h"
+
+#include "base/logging.h"
+
+namespace net {
+
+// static
+int HttpNetworkSession::max_sockets_per_group_ = 6;
+
+// static
+void HttpNetworkSession::set_max_sockets_per_group(int socket_count) {
+  DCHECK(0 < socket_count);
+  // The following is a sanity check... but we should NEVER be near this value.
+  DCHECK(100 > socket_count);
+  max_sockets_per_group_ = socket_count;
+}
+
+} //  namespace net
diff --git a/net/http/http_network_session.h b/net/http/http_network_session.h
index 2dd1b89..7c4ac68 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -17,13 +17,8 @@ class ProxyService;
 // This class holds session objects used by HttpNetworkTransaction objects.
 class HttpNetworkSession : public base::RefCounted<HttpNetworkSession> {
  public:
-  // Allow up to 6 connections per host.
-  enum {
-    MAX_SOCKETS_PER_GROUP = 6
-  };
-
   explicit HttpNetworkSession(ProxyService* proxy_service)
-      : connection_pool_(new ClientSocketPool(MAX_SOCKETS_PER_GROUP)),
+      : connection_pool_(new ClientSocketPool(max_sockets_per_group_)),
         proxy_service_(proxy_service) {
     DCHECK(proxy_service);
   }
@@ -35,7 +30,14 @@ class HttpNetworkSession : public base::RefCounted<HttpNetworkSession> {
   SSLConfigService* ssl_config_service() { return &ssl_config_service_; }
 #endif
 
+  static void set_max_sockets_per_group(int socket_count);
+
  private:
+  // Default to allow up to 6 connections per host. Experiment and tuning may
+  // try other values (greater than 0).  Too large may cause many problems, such
+  // as home routers blocking the connections!?!?
+  static int max_sockets_per_group_;
+
   HttpAuthCache auth_cache_;
   scoped_refptr<ClientSocketPool> connection_pool_;
   ProxyService* proxy_service_;
diff --git a/net/net.gyp b/net/net.gyp
index ca972fc..cfd17f6 100644
--- a/net/net.gyp
+++ b/net/net.gyp
@@ -217,6 +217,7 @@
         'http/http_chunked_decoder.h',
         'http/http_network_layer.cc',
         'http/http_network_layer.h',
+        'http/http_network_session.cc',
         'http/http_network_session.h',
         'http/http_network_transaction.cc',
         'http/http_network_transaction.h',