Change default congestion limit for DNS preresolution...

chrome/browser/net/dns_global.cc

 // Copyright (c) 2006-2008 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/net/dns_global.h"
 
 #include <map>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 27 matching lines @@
 static void DnsMotivatedPrefetch(const std::string& hostname,
                                  DnsHostInfo::ResolutionMotivation motivation);
 static void DnsPrefetchMotivatedList(
     const NameList& hostnames,
     DnsHostInfo::ResolutionMotivation motivation);
 
 // static
 const size_t DnsGlobalInit::kMaxPrefetchConcurrentLookups = 8;
 
 // static
-const int DnsGlobalInit::kMaxPrefetchQueueingDelayMs = 1000;
+const int DnsGlobalInit::kMaxPrefetchQueueingDelayMs = 500;
 
 // Host resolver shared by DNS prefetcher, and the main URLRequestContext.
 static net::HostResolver* global_host_resolver = NULL;
 
 //------------------------------------------------------------------------------
 // This section contains all the globally accessable API entry points for the
 // DNS Prefetching feature.
 //------------------------------------------------------------------------------
 
 // Status of prefetch feature, controlling whether any prefetching is done.
@@ skipping 555 matching lines @@
 // Methods for the helper class that is used to startup and teardown the whole
 // DNS prefetch system.
 
 DnsGlobalInit::DnsGlobalInit(PrefService* user_prefs,
                              PrefService* local_state) {
   DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
   // Set up a field trial to see what disabling DNS pre-resolution does to
   // latency of page loads.
   FieldTrial::Probability kDivisor = 100;
   // For each option (i.e., non-default), we have a fixed probability.
-  FieldTrial::Probability kProbabilityPerGroup = 10;  // 10% probability.
+  FieldTrial::Probability kProbabilityPerGroup = 3;  // 3% probability.
 
   trial_ = new FieldTrial("DnsImpact", kDivisor);
 
   // First option is to disable prefetching completely.
   int disabled_prefetch = trial_->AppendGroup("_disabled_prefetch",
                                               kProbabilityPerGroup);
   // Set congestion detection at 250, 500, or 750ms, rather than the 1 second
   // default.
   int max_250ms_prefetch = trial_->AppendGroup("_max_250ms_queue_prefetch",
                                                kProbabilityPerGroup);
@@ skipping 38 matching lines @@
     RestoreSubresourceReferrers(local_state);
   }
 }
 
 DnsGlobalInit::~DnsGlobalInit() {
     if (dns_master)
       FreeDnsPrefetchResources();
   }
 
 }  // namespace chrome_browser_net