chrome/browser/chromeos/memory/oom_priority_manager.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
   6 #define CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
   7
   8 #include <vector>
   9
  10 #include "base/compiler_specific.h"
  11 #include "base/containers/hash_tables.h"
  12 #include "base/gtest_prod_util.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/process/process.h"
  15 #include "base/strings/string16.h"
  16 #include "base/synchronization/lock.h"
  17 #include "base/time/time.h"
  18 #include "base/timer/timer.h"
  19 #include "chromeos/memory/low_memory_listener_delegate.h"
  20 #include "content/public/browser/notification_observer.h"
  21 #include "content/public/browser/notification_registrar.h"
  22
  23 class GURL;
  24
  25 namespace chromeos {
  26
  27 class LowMemoryListener;
  28
  29 // The OomPriorityManager periodically checks (see
  30 // ADJUSTMENT_INTERVAL_SECONDS in the source) the status of renderers
  31 // and adjusts the out of memory (OOM) adjustment value (in
  32 // /proc/<pid>/oom_score_adj) of the renderers so that they match the
  33 // algorithm embedded here for priority in being killed upon OOM
  34 // conditions.
  35 //
  36 // The algorithm used favors killing tabs that are not selected, not pinned,
  37 // and have been idle for longest, in that order of priority.
  38 class OomPriorityManager : public content::NotificationObserver,
  39                            public LowMemoryListenerDelegate {
  40  public:
  41   OomPriorityManager();
  42   virtual ~OomPriorityManager();
  43
  44   // Number of discard events since Chrome started.
  45   int discard_count() const { return discard_count_; }
  46
  47   // See member comment.
  48   bool recent_tab_discard() const { return recent_tab_discard_; }
  49
  50   void Start();
  51   void Stop();
  52
  53   // Returns list of tab titles sorted from most interesting (don't kill)
  54   // to least interesting (OK to kill).
  55   std::vector<base::string16> GetTabTitles();
  56
  57   // Discards a tab to free the memory occupied by its renderer.
  58   // Tab still exists in the tab-strip; clicking on it will reload it.
  59   // Returns true if it successfully found a tab and discarded it.
  60   bool DiscardTab();
  61
  62   // Log memory statistics for the running processes, then discards a tab.
  63   // Tab discard happens sometime later, as collecting the statistics touches
  64   // multiple threads and takes time.
  65   void LogMemoryAndDiscardTab();
  66
  67  private:
  68   friend class OomMemoryDetails;
  69   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, Comparator);
  70   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, IsReloadableUI);
  71
  72   struct TabStats {
  73     TabStats();
  74     ~TabStats();
  75     bool is_app;  // browser window is an app
  76     bool is_reloadable_ui;  // Reloadable web UI page, like NTP or Settings.
  77     bool is_playing_audio;
  78     bool is_pinned;
  79     bool is_selected;  // selected in the currently active browser window
  80     bool is_discarded;
  81     base::TimeTicks last_selected;
  82     base::ProcessHandle renderer_handle;
  83     base::string16 title;
  84     int64 tab_contents_id;  // unique ID per WebContents
  85   };
  86   typedef std::vector<TabStats> TabStatsList;
  87
  88   // Returns true if the |url| represents an internal Chrome web UI page that
  89   // can be easily reloaded and hence makes a good choice to discard.
  90   static bool IsReloadableUI(const GURL& url);
  91
  92   // Discards a tab with the given unique ID.  Returns true if discard occurred.
  93   bool DiscardTabById(int64 target_web_contents_id);
  94
  95   // Records UMA histogram statistics for a tab discard. We record statistics
  96   // for user triggered discards via chrome://discards/ because that allows us
  97   // to manually test the system.
  98   void RecordDiscardStatistics();
  99
 100   // Record whether we ran out of memory during a recent time interval.
 101   // This allows us to normalize low memory statistics versus usage.
 102   void RecordRecentTabDiscard();
 103
 104   // Purges data structures in the browser that can be easily recomputed.
 105   void PurgeBrowserMemory();
 106
 107   // Returns the number of tabs open in all browser instances.
 108   int GetTabCount() const;
 109
 110   TabStatsList GetTabStatsOnUIThread();
 111
 112   // Called when the timer fires, sets oom_adjust_score for all renderers.
 113   void AdjustOomPriorities();
 114
 115   // Called by AdjustOomPriorities.
 116   void AdjustOomPrioritiesOnFileThread(TabStatsList stats_list);
 117
 118   // Posts AdjustFocusedTabScore task to the file thread.
 119   void OnFocusTabScoreAdjustmentTimeout();
 120
 121   // Sets the score of the focused tab to the least value.
 122   void AdjustFocusedTabScoreOnFileThread();
 123
 124   static bool CompareTabStats(TabStats first, TabStats second);
 125
 126   // NotificationObserver overrides:
 127   virtual void Observe(int type,
 128                        const content::NotificationSource& source,
 129                        const content::NotificationDetails& details) OVERRIDE;
 130
 131   // LowMemoryListenerDelegate overrides:
 132   virtual void OnMemoryLow() OVERRIDE;
 133
 134   base::RepeatingTimer<OomPriorityManager> timer_;
 135   base::OneShotTimer<OomPriorityManager> focus_tab_score_adjust_timer_;
 136   base::RepeatingTimer<OomPriorityManager> recent_tab_discard_timer_;
 137   content::NotificationRegistrar registrar_;
 138
 139   // This lock is for pid_to_oom_score_ and focus_tab_pid_.
 140   base::Lock pid_to_oom_score_lock_;
 141   // map maintaining the process - oom_score mapping.
 142   typedef base::hash_map<base::ProcessHandle, int> ProcessScoreMap;
 143   ProcessScoreMap pid_to_oom_score_;
 144   base::ProcessHandle focused_tab_pid_;
 145
 146   // Observer for the kernel low memory signal.
 147   scoped_ptr<LowMemoryListener> low_memory_listener_;
 148
 149   // Wall-clock time when the priority manager started running.
 150   base::TimeTicks start_time_;
 151
 152   // Wall-clock time of last tab discard during this browsing session, or 0 if
 153   // no discard has happened yet.
 154   base::TimeTicks last_discard_time_;
 155
 156   // Wall-clock time of last priority adjustment, used to correct the above
 157   // times for discontinuities caused by suspend/resume.
 158   base::TimeTicks last_adjust_time_;
 159
 160   // Number of times we have discarded a tab, for statistics.
 161   int discard_count_;
 162
 163   // Whether a tab discard event has occurred during the last time interval,
 164   // used for statistics normalized by usage.
 165   bool recent_tab_discard_;
 166
 167   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
 168 };
 169
 170 }  // namespace chromeos
 171
 172 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_