Add zram field trial

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

 // Copyright (c) 2012 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/chromeos/chrome_browser_main_chromeos.h"
 
 #include <string>
 #include <vector>
 
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/chromeos/chromeos_version.h"
 #include "base/command_line.h"
+#include "base/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/linux_util.h"
 #include "base/message_loop.h"
 #include "base/string_number_conversions.h"
 #include "base/string_split.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/accessibility/accessibility_util.h"
 #include "chrome/browser/chromeos/accessibility/magnification_manager.h"
 #include "chrome/browser/chromeos/audio/audio_handler.h"
 #include "chrome/browser/chromeos/boot_times_loader.h"
@@ skipping 685 matching lines @@
 
   // Let the UserManager unregister itself as an observer of the CrosSettings
   // singleton before it is destroyed.
   UserManager::Get()->Shutdown();
 
   ChromeBrowserMainPartsLinux::PostMainMessageLoopRun();
 }
 
 void ChromeBrowserMainPartsChromeos::SetupPlatformFieldTrials() {
   SetupLowMemoryHeadroomFieldTrial();
+  SetupZramFieldTrial();
 }
 
 void ChromeBrowserMainPartsChromeos::SetupLowMemoryHeadroomFieldTrial() {
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   // Only enable this experiment on Canary and Dev, since it's possible
   // that this will make the machine unstable.
   // Note that to have this code execute in a developer build,
   // then chrome::VersionInfo::CHANNEL_UNKNOWN needs to be added here.
   if (channel == chrome::VersionInfo::CHANNEL_CANARY ||
       channel == chrome::VersionInfo::CHANNEL_DEV) {
@@ skipping 28 matching lines @@
       LowMemoryObserver::SetLowMemoryMargin(100);
     } else if (trial->group() == margin_200mb) {
       LOG(WARNING) << "low_mem: Part of '200MB' experiment";
       LowMemoryObserver::SetLowMemoryMargin(200);
     } else {
       LOG(WARNING) << "low_mem: Part of 'default' experiment";
     }
   }
 }
 
+
+void ChromeBrowserMainPartsChromeos::SetupZramFieldTrial() {
+  // The dice for this experiment have been thrown at boot.  The selected group
+  // number is stored in a file.
+  const FilePath kZramGroupPath("/home/chronos/.swap_exp_enrolled");
+  std::string zram_file_content;
+  // If the file does not exist, the experiment has not started.
+  if (!file_util::ReadFileToString(kZramGroupPath, &zram_file_content))
+    return;
+  // The file contains a single significant character, possibly followed by
+  // newline.  "x" means the user has opted out.  "0" through "8" are the valid
+  // group names.  (See src/platform/init/swap-exp.conf in chromiumos repo for
+  // group meanings.)
+  std::string zram_group = zram_file_content.substr(0, 1);
+  if (zram_group.compare("x") == 0)
+    return;
+  const base::FieldTrial::Probability kDivisor = 1;  // on/off only
+  scoped_refptr<base::FieldTrial> trial =
+      base::FieldTrialList::FactoryGetFieldTrial(
+          "ZRAM", kDivisor, "default", 2013, 12, 31, NULL);
+  // Assign probability of 1 to the group Chrome OS has picked.  Assign 0 to
+  // all other choices.
+  const char* const kGroups[] = { "0", "1", "2", "3", "4", "5", "6", "7", "8" };
+  bool matched = false;
+  for (size_t i = 0; i < arraysize(kGroups); ++i) {
+    bool match = zram_group.compare(kGroups[i]) == 0;
+    trial->AppendGroup(kGroups[i], match ? 1 : 0);
+    if (match) {
+      matched = true;
+      LOG(WARNING) << "zram field trial: group " << kGroups[i];
+    }
+  }
+  if (!matched)
+    LOG(WARNING) << "zram field trial: invalid group \"" << zram_group << "\"";
+}
+
 }  //  namespace chromeos