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      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<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     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.  NULL if tab discarding is
    147   // disabled.
    148   scoped_ptr<LowMemoryListener> low_memory_listener_;
    149 
    150   // Wall-clock time when the priority manager started running.
    151   base::TimeTicks start_time_;
    152 
    153   // Wall-clock time of last tab discard during this browsing session, or 0 if
    154   // no discard has happened yet.
    155   base::TimeTicks last_discard_time_;
    156 
    157   // Wall-clock time of last priority adjustment, used to correct the above
    158   // times for discontinuities caused by suspend/resume.
    159   base::TimeTicks last_adjust_time_;
    160 
    161   // Number of times we have discarded a tab, for statistics.
    162   int discard_count_;
    163 
    164   // Whether a tab discard event has occurred during the last time interval,
    165   // used for statistics normalized by usage.
    166   bool recent_tab_discard_;
    167 
    168   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
    169 };
    170 
    171 }  // namespace chrome
    172 
    173 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_
    174