Remove all MemoryModel-related code, since we're unlikely to use it again. Also changes some sample code to use a random generic name ("PruningAlgorithm") instead of MemoryModel in hopes that no one will be confused.

This does not remove IdleTimer, even though it now has no users.  I do plan to remove it, but I want to do that in a separate commit so it's easy to reference and revert if at some later point we want this functionality.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/242079

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27652 0039d316-1c4b-4281-b951-d872f2087c98

16 files changed, 8 insertions, 234 deletions

diff --git a/base/field_trial.h b/base/field_trial.h
index 82bf3b36..0779981 100644
--- a/base/field_trial.h
+++ b/base/field_trial.h
@@ -22,7 +22,7 @@
 
 //------------------------------------------------------------------------------
 // Example:  Suppose we have an experiment involving memory, such as determining
-// the impact of memory model command line flags actual memory use.
+// the impact of some pruning algorithm.
 // We assume that we already have a histogram of memory usage, such as:
 
 //   HISTOGRAM_COUNTS("Memory.RendererTotal", count);
@@ -38,9 +38,9 @@
 // int group2 = trial->AppendGroup("_low_mem", 20);   // 2% in _low_mem group.
 // // Take action depending of which group we randomly land in.
 // if (trial->group() == group1)
-//   SetMemoryModel(HIGH);  // Sample setting of browser state.
+//   SetPruningAlgorithm(kType1);  // Sample setting of browser state.
 // else if (trial->group() == group2)
-//   SetMemoryModel(LOW);  // Sample alternate setting.
+//   SetPruningAlgorithm(kType2);  // Sample alternate setting.
 
 // We then modify any histograms we wish to correlate with our experiment to
 // have slighly different names, depending on what group the trial instance
diff --git a/base/process.h b/base/process.h
index 459ad58..fa076b9 100644
--- a/base/process.h
+++ b/base/process.h
@@ -66,24 +66,6 @@ class Process {
   // Returns true if the priority was changed, false otherwise.
   bool SetProcessBackgrounded(bool value);
 
-  // Reduces the working set of memory used by the process.
-  // The algorithm used by this function is intentionally vague.  Repeated calls
-  // to this function consider the process' previous required Working Set sizes
-  // to determine a reasonable reduction.  This helps give memory back to the OS
-  // in increments without over releasing memory.
-  // When the WorkingSet is reduced, it is permanent, until the caller calls
-  // UnReduceWorkingSet.
-  // Returns true if successful, false otherwise.
-  bool ReduceWorkingSet();
-
-  // Undoes the effects of prior calls to ReduceWorkingSet().
-  // Returns true if successful, false otherwise.
-  bool UnReduceWorkingSet();
-
-  // Releases as much of the working set back to the OS as possible.
-  // Returns true if successful, false otherwise.
-  bool EmptyWorkingSet();
-
  private:
   ProcessHandle process_;
   size_t last_working_set_size_;
diff --git a/base/process_posix.cc b/base/process_posix.cc
index c9a7dfc..f0e019a 100644
--- a/base/process_posix.cc
+++ b/base/process_posix.cc
@@ -36,21 +36,6 @@ bool Process::SetProcessBackgrounded(bool value) {
   return true;
 }
 
-bool Process::ReduceWorkingSet() {
-  // http://code.google.com/p/chromium/issues/detail?id=8083
-  return false;
-}
-
-bool Process::UnReduceWorkingSet() {
-  // http://code.google.com/p/chromium/issues/detail?id=8083
-  return false;
-}
-
-bool Process::EmptyWorkingSet() {
-  // http://code.google.com/p/chromium/issues/detail?id=8083
-  return false;
-}
-
 ProcessId Process::pid() const {
   if (process_ == 0)
     return 0;
diff --git a/base/process_win.cc b/base/process_win.cc
index 263e577..469e7cd 100644
--- a/base/process_win.cc
+++ b/base/process_win.cc
@@ -38,77 +38,6 @@ bool Process::SetProcessBackgrounded(bool value) {
   return (SetPriorityClass(process_, priority) != 0);
 }
 
-// According to MSDN, these are the default values which XP
-// uses to govern working set soft limits.
-// http://msdn.microsoft.com/en-us/library/ms686234.aspx
-static const int kWinDefaultMinSet = 50 * 4096;
-static const int kWinDefaultMaxSet = 345 * 4096;
-static const int kDampingFactor = 2;
-
-bool Process::ReduceWorkingSet() {
-  if (!process_)
-    return false;
-  // The idea here is that when we the process' working set has gone
-  // down, we want to release those pages to the OS quickly.  However,
-  // when it is not going down, we want to be careful not to release
-  // too much back to the OS, as it could cause additional paging.
-
-  // We use a damping function to lessen the working set over time.
-  // As the process grows/shrinks, this algorithm will lag with
-  // working set reduction.
-  //
-  // The intended algorithm is:
-  //   TargetWorkingSetSize = (LastWorkingSet/2 + CurrentWorkingSet) /2
-
-  scoped_ptr<ProcessMetrics> metrics(
-      ProcessMetrics::CreateProcessMetrics(process_));
-  WorkingSetKBytes working_set;
-  if (!metrics->GetWorkingSetKBytes(&working_set))
-    return false;
-
-
-  // We want to compute the amount of working set that the process
-  // needs to keep in memory.  Since other processes contain the
-  // pages which are shared, we don't need to reserve them in our
-  // process, the system already has them tagged.  Keep in mind, we
-  // don't get to control *which* pages get released, but if we
-  // assume reasonable distribution of pages, this should generally
-  // be the right value.
-  size_t current_working_set_size  = working_set.priv +
-                                     working_set.shareable;
-
-  size_t max_size = current_working_set_size;
-  if (last_working_set_size_)
-    max_size = (max_size + last_working_set_size_) / 2;  // Average.
-  max_size *= 1024;  // Convert to KBytes.
-  last_working_set_size_ = current_working_set_size / kDampingFactor;
-
-  BOOL rv = SetProcessWorkingSetSize(process_, kWinDefaultMinSet, max_size);
-  return rv == TRUE;
-}
-
-bool Process::UnReduceWorkingSet() {
-  if (!process_)
-    return false;
-
-  if (!last_working_set_size_)
-    return true;  // There was nothing to undo.
-
-  // We've had a reduced working set.  Make sure we have lots of
-  // headroom now that we're active again.
-  size_t limit = last_working_set_size_ * kDampingFactor * 2 * 1024;
-  BOOL rv = SetProcessWorkingSetSize(process_, kWinDefaultMinSet, limit);
-  return rv == TRUE;
-}
-
-bool Process::EmptyWorkingSet() {
-  if (!process_)
-    return false;
-
-  BOOL rv = SetProcessWorkingSetSize(process_, -1, -1);
-  return rv == TRUE;
-}
-
 ProcessId Process::pid() const {
   if (process_ == 0)
     return 0;
diff --git a/chrome/browser/browser.cc b/chrome/browser/browser.cc
index d340b0e..a4052bd 100644
--- a/chrome/browser/browser.cc
+++ b/chrome/browser/browser.cc
@@ -102,58 +102,6 @@ using base::TimeDelta;
 // How long we wait before updating the browser chrome while loading a page.
 static const int kUIUpdateCoalescingTimeMS = 200;
 
-// Idle time before helping prune memory consumption.
-static const int kBrowserReleaseMemoryInterval = 30;  // In seconds.
-
-///////////////////////////////////////////////////////////////////////////////
-
-// A task to reduce the working set of the child processes that live on the IO
-// thread (i.e. plugins, workers).
-class ReduceChildProcessesWorkingSetTask : public Task {
- public:
-  virtual void Run() {
-#if defined(OS_WIN)
-    for (ChildProcessHost::Iterator iter; !iter.Done(); ++iter)
-      iter->ReduceWorkingSet();
-#endif
-  }
-};
-
-// A browser task to run when the user is not using the browser.
-// In our case, we're trying to be nice to the operating system and release
-// memory not in use.
-class BrowserIdleTimer : public base::IdleTimer {
- public:
-  BrowserIdleTimer()
-      : base::IdleTimer(TimeDelta::FromSeconds(kBrowserReleaseMemoryInterval),
-                        false) {
-  }
-
-  virtual void OnIdle() {
-#if defined(OS_WIN)
-    // We're idle.  Release browser and renderer unused pages.
-
-    // Handle the Browser.
-    base::Process process(GetCurrentProcess());
-    process.ReduceWorkingSet();
-
-    // Handle the Renderer(s).
-    RenderProcessHost::iterator renderer_iter(
-        RenderProcessHost::AllHostsIterator());
-    while (!renderer_iter.IsAtEnd()) {
-      base::Process process = renderer_iter.GetCurrentValue()->process();
-      process.ReduceWorkingSet();
-      renderer_iter.Advance();
-    }
-
-    // Handle the child processe.  We need to iterate through them on the IO
-    // thread because that thread manages the child process collection.
-    g_browser_process->io_thread()->message_loop()->PostTask(FROM_HERE,
-        new ReduceChildProcessesWorkingSetTask());
-#endif
-  }
-};
-
 ///////////////////////////////////////////////////////////////////////////////
 
 namespace {
@@ -181,8 +129,7 @@ Browser::Browser(Type type, Profile* profile)
       is_attempting_to_close_browser_(false),
       cancel_download_confirmation_state_(NOT_PROMPTED),
       maximized_state_(MAXIMIZED_STATE_DEFAULT),
-      method_factory_(this),
-      idle_task_(new BrowserIdleTimer) {
+      method_factory_(this) {
   tabstrip_model_.AddObserver(this);
 
   registrar_.Add(this, NotificationType::SSL_VISIBLE_STATE_CHANGED,
@@ -209,10 +156,6 @@ Browser::Browser(Type type, Profile* profile)
 
   encoding_auto_detect_.Init(prefs::kWebKitUsesUniversalDetector,
                              profile_->GetPrefs(), NULL);
-
-  // Trim browser memory on idle for low & medium memory models.
-  if (g_browser_process->memory_model() < BrowserProcess::HIGH_MEMORY_MODEL)
-    idle_task_->Start();
 }
 
 Browser::~Browser() {
diff --git a/chrome/browser/browser.h b/chrome/browser/browser.h
index 8e42694..d881059 100644
--- a/chrome/browser/browser.h
+++ b/chrome/browser/browser.h
@@ -25,7 +25,6 @@
 #include "chrome/common/pref_member.h"
 #include "testing/gtest/include/gtest/gtest_prod.h"
 
-class BrowserIdleTimer;
 class BrowserWindow;
 class DebuggerWindow;
 class FindBarController;
@@ -795,9 +794,6 @@ class Browser : public TabStripModelDelegate,
   // Dialog box used for opening and saving files.
   scoped_refptr<SelectFileDialog> select_file_dialog_;
 
-  // The browser idle task helps cleanup unused memory resources when idle.
-  scoped_ptr<BrowserIdleTimer> idle_task_;
-
   // Keep track of the encoding auto detect pref.
   BooleanPrefMember encoding_auto_detect_;
 
diff --git a/chrome/browser/browser_process.h b/chrome/browser/browser_process.h
index ff41250..7c1c5b3 100644
--- a/chrome/browser/browser_process.h
+++ b/chrome/browser/browser_process.h
@@ -53,21 +53,6 @@ class BrowserProcess {
   BrowserProcess() {}
   virtual ~BrowserProcess() {}
 
-  // The browser has 3 memory model configurations.  These models have to
-  // do with how aggressively we release Renderer memory to the OS.
-  // Low memory releases memory the fastest, High memory releases it the
-  // slowest.  Geek out!
-  enum MemoryModel {
-    // Will release as much memory as it can after each tab switch, and also
-    // after user idle.
-    LOW_MEMORY_MODEL,
-    // Will release a little memory after each tab switch and also after
-    // user idle.
-    MEDIUM_MEMORY_MODEL,
-    // Hangs onto every last byte.
-    HIGH_MEMORY_MODEL
-  };
-
   // Invoked when the user is logging out/shutting down. When logging off we may
   // not have enough time to do a normal shutdown. This method is invoked prior
   // to normal shutdown and saves any state that must be saved before we are
@@ -133,8 +118,6 @@ class BrowserProcess {
   // Returns the locale used by the application.
   virtual const std::string& GetApplicationLocale() = 0;
 
-  virtual MemoryModel memory_model() = 0;
-
   DownloadRequestManager* download_request_manager();
 
   // Returns an event that is signaled when the browser shutdown.
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index 1509c68..f381b65 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -146,7 +146,6 @@ BrowserProcessImpl::BrowserProcessImpl(const CommandLine& command_line)
       created_debugger_wrapper_(false),
       created_devtools_manager_(false),
       module_ref_count_(0),
-      memory_model_(HIGH_MEMORY_MODEL),
       checked_for_new_frames_(false),
       using_new_frames_(false),
       have_inspector_files_(true) {
@@ -157,18 +156,6 @@ BrowserProcessImpl::BrowserProcessImpl(const CommandLine& command_line)
   // Must be created after the NotificationService.
   print_job_manager_.reset(new printing::PrintJobManager);
 
-  // Configure the browser memory model.
-  if (command_line.HasSwitch(switches::kMemoryModel)) {
-    std::wstring model = command_line.GetSwitchValue(switches::kMemoryModel);
-    if (!model.empty()) {
-      if (model == L"high")
-        memory_model_ = HIGH_MEMORY_MODEL;
-      else if (model == L"low")
-        memory_model_ = LOW_MEMORY_MODEL;
-      else if (model == L"medium")
-        memory_model_ = MEDIUM_MEMORY_MODEL;
-    }
-  }
   shutdown_event_.reset(new base::WaitableEvent(true, false));
 }
 
diff --git a/chrome/browser/browser_process_impl.h b/chrome/browser/browser_process_impl.h
index 4f094dd..a949ae4 100644
--- a/chrome/browser/browser_process_impl.h
+++ b/chrome/browser/browser_process_impl.h
@@ -183,11 +183,6 @@ class BrowserProcessImpl : public BrowserProcess, public NonThreadSafe {
 
   virtual const std::string& GetApplicationLocale();
 
-  virtual MemoryModel memory_model() {
-    DCHECK(CalledOnValidThread());
-    return memory_model_;
-  }
-
   virtual base::WaitableEvent* shutdown_event() {
     return shutdown_event_.get();
   }
@@ -285,8 +280,6 @@ class BrowserProcessImpl : public BrowserProcess, public NonThreadSafe {
 
   std::string locale_;
 
-  MemoryModel memory_model_;
-
   bool checked_for_new_frames_;
   bool using_new_frames_;
 
diff --git a/chrome/browser/browser_trial.cc b/chrome/browser/browser_trial.cc
index 31a2ea0..10ffcda 100644
--- a/chrome/browser/browser_trial.cc
+++ b/chrome/browser/browser_trial.cc
@@ -6,5 +6,6 @@
 
 // The following is a sample of the lines that should be listed here.
 
-// // A test to determine the impact of using HIGH vs MEDIUM memory models.
-// const wchar_t* BrowserTrial::kMemoryModelFieldTrial = L"memory_model";
+// // A test to determine the impact of kCase1 vs kCase2 pruning algorithms.
+// const wchar_t* BrowserTrial::kPruningAlgorithmFieldTrial =
+//     L"pruning_algorithm";
diff --git a/chrome/browser/browser_trial.h b/chrome/browser/browser_trial.h
index cae4dfa..f878a14 100644
--- a/chrome/browser/browser_trial.h
+++ b/chrome/browser/browser_trial.h
@@ -16,7 +16,7 @@ class BrowserTrial {
  public:
 
   // The following is a sample line for what should be listed in this file.
-  // static const wchar_t* kMemoryModelFieldTrial;
+  // static const wchar_t* kPruningAlgorithmFieldTrial;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BrowserTrial);
diff --git a/chrome/browser/renderer_host/browser_render_process_host.cc b/chrome/browser/renderer_host/browser_render_process_host.cc
index b0ec310..899b3ff 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.cc
+++ b/chrome/browser/renderer_host/browser_render_process_host.cc
@@ -923,21 +923,6 @@ void BrowserRenderProcessHost::SetBackgrounded(bool backgrounded) {
         return;
       }
     }
-
-    // Now tune the memory footprint of the renderer.
-    // If the OS needs to page, we'd rather it page idle renderers.
-    BrowserProcess::MemoryModel model = g_browser_process->memory_model();
-    if (model < BrowserProcess::HIGH_MEMORY_MODEL) {
-      if (backgrounded) {
-        if (model == BrowserProcess::LOW_MEMORY_MODEL)
-          process_.EmptyWorkingSet();
-        else if (model == BrowserProcess::MEDIUM_MEMORY_MODEL)
-          process_.ReduceWorkingSet();
-      } else {
-        if (model == BrowserProcess::MEDIUM_MEMORY_MODEL)
-          process_.UnReduceWorkingSet();
-      }
-    }
   }
 
   // Note: we always set the backgrounded_ value.  If the process is NULL
diff --git a/chrome/common/child_process_info.h b/chrome/common/child_process_info.h
index c99b2c0..31b1cb84 100644
--- a/chrome/common/child_process_info.h
+++ b/chrome/common/child_process_info.h
@@ -46,7 +46,6 @@ class ChildProcessInfo {
   int id() const { return id_; }
 
   void SetProcessBackgrounded() const { process_.SetProcessBackgrounded(true); }
-  void ReduceWorkingSet() const { process_.ReduceWorkingSet(); }
 
   // Returns an English name of the process type, should only be used for non
   // user-visible strings, or debugging pages like about:memory.
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index b619517..176eb57 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -292,12 +292,6 @@ const wchar_t kTabCountToLoadOnSessionRestore[] =
 // all memory allocations during the run.
 const wchar_t kMemoryProfiling[]               = L"memory-profile";
 
-// Configure Chrome's memory model.
-// Does chrome really need multiple memory models?  No.  But we get a lot
-// of concerns from individuals about how the changes work on *their*
-// system, and we need to be able to experiment with a few choices.
-const wchar_t kMemoryModel[]                   = L"memory-model";
-
 // By default, cookies are not allowed on file://. They are needed in for
 // testing, for example page cycler and layout tests.  See bug 1157243.
 const wchar_t kEnableFileCookies[]             = L"enable-file-cookies";
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index f6cb10d..8774a0f 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -100,7 +100,6 @@ extern const wchar_t kEnableExtensionTimelineApi[];
 extern const wchar_t kTabCountToLoadOnSessionRestore[];
 
 extern const wchar_t kMemoryProfiling[];
-extern const wchar_t kMemoryModel[];
 
 extern const wchar_t kEnableFileCookies[];
 
diff --git a/chrome/test/testing_browser_process.h b/chrome/test/testing_browser_process.h
index 22e106b..d105fda 100644
--- a/chrome/test/testing_browser_process.h
+++ b/chrome/test/testing_browser_process.h
@@ -136,8 +136,6 @@ class TestingBrowserProcess : public BrowserProcess {
     return *value;
   }
 
-  virtual MemoryModel memory_model() { return HIGH_MEMORY_MODEL; }
-
   virtual base::WaitableEvent* shutdown_event() {
     return shutdown_event_.get();
   }