Make 5 minutes the default prerender TTL, create new 15 minute field trial.

The 5min TTL field trial is going well; especially with the new abandon logic in the 5min trial, the results suggest slightly faster PLT. Since this is also a correctness issue for making the prerender API widely useable, let's go ahead an extend the TTL, and start a new field trial for a 15 minute TTL, to see if that far a horizon helps further.

While I was here, I discovered a misedit of PrerenderManager::PrerenderManagerMode from a while back; I've made that enum much less susceptable to careless edits now by coping the form of PrerenderFinalStatus.

R=mmenke@chromium.org,dominich@chromium.org
BUG=None


Review URL: https://chromiumcodereview.appspot.com/10908235

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@156647 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 40 insertions, 39 deletions

diff --git a/chrome/browser/prerender/prerender_config.cc b/chrome/browser/prerender/prerender_config.cc
index fbe4351..b9482d4 100644
--- a/chrome/browser/prerender/prerender_config.cc
+++ b/chrome/browser/prerender/prerender_config.cc
@@ -9,7 +9,7 @@ namespace prerender {
 Config::Config() : max_bytes(100 * 1024 * 1024),
                    max_concurrency(1),
                    rate_limit_enabled(true),
-                   time_to_live(base::TimeDelta::FromSeconds(30)),
+                   time_to_live(base::TimeDelta::FromMinutes(5)),
                    abandon_time_to_live(base::TimeDelta::FromSeconds(30)),
                    https_allowed(true),
                    default_tab_bounds(640, 480),
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index 160a033..69edf7b 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -53,7 +53,7 @@ void SetupPrerenderFieldTrial() {
 
   FieldTrial::Probability control_probability;
   FieldTrial::Probability experiment_multi_prerender_probability;
-  FieldTrial::Probability experiment_5min_ttl_probability;
+  FieldTrial::Probability experiment_15min_ttl_probability;
   FieldTrial::Probability experiment_no_use_probability;
 
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
@@ -64,19 +64,19 @@ void SetupPrerenderFieldTrial() {
     const FieldTrial::Probability release_control_probability = 10;
     const FieldTrial::Probability
         release_experiment_multi_prerender_probability = 0;
-    const FieldTrial::Probability release_experiment_5min_ttl_probability = 10;
+    const FieldTrial::Probability release_experiment_15min_ttl_probability = 10;
     const FieldTrial::Probability release_experiment_no_use_probability = 0;
     COMPILE_ASSERT(
         release_prerender_enabled_probability + release_control_probability +
         release_experiment_multi_prerender_probability +
-        release_experiment_5min_ttl_probability +
+        release_experiment_15min_ttl_probability +
         release_experiment_no_use_probability == divisor,
         release_experiment_probabilities_must_equal_divisor);
 
-    control_probability = release_experiment_5min_ttl_probability;
+    control_probability = release_experiment_15min_ttl_probability;
     experiment_multi_prerender_probability =
         release_experiment_multi_prerender_probability;
-    experiment_5min_ttl_probability = release_control_probability;
+    experiment_15min_ttl_probability = release_control_probability;
     experiment_no_use_probability = release_experiment_no_use_probability;
   } else {
     // In testing channels, use more experiments and a larger control group to
@@ -85,18 +85,18 @@ void SetupPrerenderFieldTrial() {
     const FieldTrial::Probability dev_control_probability = 250;
     const FieldTrial::Probability
         dev_experiment_multi_prerender_probability = 250;
-    const FieldTrial::Probability dev_experiment_5min_ttl_probability = 125;
+    const FieldTrial::Probability dev_experiment_15min_ttl_probability = 125;
     const FieldTrial::Probability dev_experiment_no_use_probability = 125;
     COMPILE_ASSERT(dev_prerender_enabled_probability + dev_control_probability +
                    dev_experiment_multi_prerender_probability +
-                   dev_experiment_5min_ttl_probability +
+                   dev_experiment_15min_ttl_probability +
                    dev_experiment_no_use_probability == divisor,
                    dev_experiment_probabilities_must_equal_divisor);
 
-    control_probability = dev_experiment_5min_ttl_probability;
+    control_probability = dev_experiment_15min_ttl_probability;
     experiment_multi_prerender_probability =
         dev_experiment_multi_prerender_probability;
-    experiment_5min_ttl_probability = dev_control_probability;
+    experiment_15min_ttl_probability = dev_control_probability;
     experiment_no_use_probability = dev_experiment_no_use_probability;
   }
 
@@ -112,8 +112,8 @@ void SetupPrerenderFieldTrial() {
       trial->AppendGroup("PrerenderMulti",
                          experiment_multi_prerender_probability);
   const int experiment_5_min_TTL_group =
-      trial->AppendGroup("Prerender5minTTL",
-                         experiment_5min_ttl_probability);
+      trial->AppendGroup("Prerender15minTTL",
+                         experiment_15min_ttl_probability);
   const int experiment_no_use_group =
       trial->AppendGroup("PrerenderNoUse",
                          experiment_no_use_probability);
@@ -130,7 +130,7 @@ void SetupPrerenderFieldTrial() {
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP);
   } else if (trial_group == experiment_5_min_TTL_group) {
     PrerenderManager::SetMode(
-        PrerenderManager::PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP);
+        PrerenderManager::PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP);
   } else if (trial_group == experiment_no_use_group) {
     PrerenderManager::SetMode(
         PrerenderManager::PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP);
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index b33554a..82cf8b1 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -107,17 +107,6 @@ bool NeedMatchCompleteDummyForFinalStatus(FinalStatus final_status) {
       final_status != FINAL_STATUS_CROSS_SITE_NAVIGATION_PENDING;
 }
 
-size_t GetMaxConcurrency() {
-  return PrerenderManager::GetMode() ==
-      PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP ? 3 : 1;
-}
-
-base::TimeDelta GetTimeToLive() {
-  return PrerenderManager::GetMode() ==
-      PrerenderManager::PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP ?
-      base::TimeDelta::FromMinutes(5) : base::TimeDelta::FromSeconds(30);
-}
-
 }  // namespace
 
 class PrerenderManager::OnCloseTabContentsDeleter
@@ -199,8 +188,18 @@ PrerenderManager::PrerenderManager(Profile* profile,
   // Any other checks simply make sure that the PrerenderManager is accessed on
   // the same thread that it was created on.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  config_.max_concurrency = GetMaxConcurrency();
-  config_.time_to_live = GetTimeToLive();
+
+  // Certain experiments override our default config_ values.
+  switch (PrerenderManager::GetMode()) {
+    case PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP:
+      config_.max_concurrency = 3;
+      break;
+    case PrerenderManager::PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP:
+      config_.time_to_live = base::TimeDelta::FromMinutes(15);
+      break;
+    default:
+      break;
+  }
 }
 
 PrerenderManager::~PrerenderManager() {
@@ -568,11 +567,12 @@ const char* PrerenderManager::GetModeString() {
       return "_Control";
     case PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP:
       return "_Multi";
-    case PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP:
-      return "_5MinTTL";
+    case PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP:
+      return "_15MinTTL";
     case PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP:
       return "_NoUse";
     case PRERENDER_MODE_MAX:
+    default:
       NOTREACHED() << "Invalid PrerenderManager mode.";
       break;
   };
@@ -713,8 +713,9 @@ DictionaryValue* PrerenderManager::GetAsValue() const {
     enabled_note += "(Control group: Not actually prerendering) ";
   if (IsNoUseGroup())
     enabled_note += "(No-use group: Not swapping in prerendered pages) ";
-  if (GetMode() == PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP)
-    enabled_note += "(5 min TTL group: Extended prerender eviction to 5 mins) ";
+  if (GetMode() == PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP)
+    enabled_note +=
+        "(15 min TTL group: Extended prerender eviction to 15 mins) ";
   dict_value->SetString("enabled_note", enabled_note);
   return dict_value;
 }
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index 3510962..058aa35 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -69,16 +69,16 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
                          public base::NonThreadSafe,
                          public ProfileKeyedService {
  public:
-  // PrerenderManagerMode is used in a UMA_HISTOGRAM, so please do not
-  // add in the middle.
+  // NOTE: New values need to be appended, since they are used in histograms.
   enum PrerenderManagerMode {
-    PRERENDER_MODE_DISABLED,
-    PRERENDER_MODE_ENABLED,
-    PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP,
-    PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP,
-    PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP,
-    PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP,
-    PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP,
+    PRERENDER_MODE_DISABLED = 0,
+    PRERENDER_MODE_ENABLED = 1,
+    PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP = 2,
+    PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP = 3,
+    // Obsolete: PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP = 4,
+    PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP = 5,
+    PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP = 6,
+    PRERENDER_MODE_EXPERIMENT_15MIN_TTL_GROUP = 7,
     PRERENDER_MODE_MAX
   };