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 "content/public/browser/notification_observer.h"
  20 #include "content/public/browser/notification_registrar.h"
  21
  22 class GURL;
  23
  24 namespace chromeos {
  25
  26 class LowMemoryObserver;
  27
  28 // The OomPriorityManager periodically checks (see
  29 // ADJUSTMENT_INTERVAL_SECONDS in the source) the status of renderers
  30 // and adjusts the out of memory (OOM) adjustment value (in
  31 // /proc/<pid>/oom_score_adj) of the renderers so that they match the
  32 // algorithm embedded here for priority in being killed upon OOM
  33 // conditions.
  34 //
  35 // The algorithm used favors killing tabs that are not selected, not pinned,
  36 // and have been idle for longest, in that order of priority.
  37 class OomPriorityManager : public content::NotificationObserver {
  38  public:
  39   OomPriorityManager();
  40   virtual ~OomPriorityManager();
  41
  42   // Number of discard events since Chrome started.
  43   int discard_count() const { return discard_count_; }
  44
  45   // See member comment.
  46   bool recent_tab_discard() const { return recent_tab_discard_; }
  47
  48   void Start();
  49   void Stop();
  50
  51   // Returns list of tab titles sorted from most interesting (don't kill)
  52   // to least interesting (OK to kill).
  53   std::vector<base::string16> GetTabTitles();
  54
  55   // Discards a tab to free the memory occupied by its renderer.
  56   // Tab still exists in the tab-strip; clicking on it will reload it.
  57   // Returns true if it successfully found a tab and discarded it.
  58   bool DiscardTab();
  59
  60   // Log memory statistics for the running processes, then discards a tab.
  61   // Tab discard happens sometime later, as collecting the statistics touches
  62   // multiple threads and takes time.
  63   void LogMemoryAndDiscardTab();
  64
  65  private:
  66   friend class OomMemoryDetails;
  67   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, Comparator);
  68   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, IsReloadableUI);
  69   FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, GetProcessHandles);
  70
  71   struct TabStats {
  72     TabStats();
  73     ~TabStats();
  74     bool is_app;  // browser window is an app
  75     bool is_reloadable_ui;  // Reloadable web UI page, like NTP or Settings.
  76     bool is_playing_audio;
  77     bool is_pinned;
  78     bool is_selected;  // selected in the currently active browser window
  79     bool is_discarded;
  80     base::TimeTicks last_active;
  81     base::ProcessHandle renderer_handle;
  82     base::string16 title;
  83     int64 tab_contents_id;  // unique ID per WebContents
  84   };
  85   typedef std::vector<TabStats> TabStatsList;
  86
  87   // Returns true if the |url| represents an internal Chrome web UI page that
  88   // can be easily reloaded and hence makes a good choice to discard.
  89   static bool IsReloadableUI(const GURL& url);
  90
  91   // Discards a tab with the given unique ID.  Returns true if discard occurred.
  92   bool DiscardTabById(int64 target_web_contents_id);
  93
  94   // Records UMA histogram statistics for a tab discard. We record statistics
  95   // for user triggered discards via chrome://discards/ because that allows us
  96   // to manually test the system.
  97   void RecordDiscardStatistics();
  98
  99   // Record whether we ran out of memory during a recent time interval.
 100   // This allows us to normalize low memory statistics versus usage.
 101   void RecordRecentTabDiscard();
 102
 103   // Purges data structures in the browser that can be easily recomputed.
 104   void PurgeBrowserMemory();
 105
 106   // Returns the number of tabs open in all browser instances.
 107   int GetTabCount() const;
 108
 109   TabStatsList GetTabStatsOnUIThread();
 110
 111   // Called when the timer fires, sets oom_adjust_score for all renderers.
 112   void AdjustOomPriorities();
 113
 114   // Returns a list of unique process handles from |stats_list|. If multiple
 115   // tabs use the same process, returns the first process handle. This implies
 116   // that the processes are selected based on their "most important" tab.
 117   static std::vector<base::ProcessHandle> GetProcessHandles(
 118       const TabStatsList& stats_list);
 119
 120   // Called by AdjustOomPriorities.
 121   void AdjustOomPrioritiesOnFileThread(TabStatsList stats_list);
 122
 123   // Posts AdjustFocusedTabScore task to the file thread.
 124   void OnFocusTabScoreAdjustmentTimeout();
 125
 126   // Sets the score of the focused tab to the least value.
 127   void AdjustFocusedTabScoreOnFileThread();
 128
 129   static bool CompareTabStats(TabStats first, TabStats second);
 130
 131   virtual void Observe(int type,
 132                        const content::NotificationSource& source,
 133                        const content::NotificationDetails& details) OVERRIDE;
 134
 135   base::RepeatingTimer<OomPriorityManager> timer_;
 136   base::OneShotTimer<OomPriorityManager> focus_tab_score_adjust_timer_;
 137   base::RepeatingTimer<OomPriorityManager> recent_tab_discard_timer_;
 138   content::NotificationRegistrar registrar_;
 139
 140   // This lock is for pid_to_oom_score_ and focus_tab_pid_.
 141   base::Lock pid_to_oom_score_lock_;
 142   // map maintaining the process - oom_score mapping.
 143   typedef base::hash_map<base::ProcessHandle, int> ProcessScoreMap;
 144   ProcessScoreMap pid_to_oom_score_;
 145   base::ProcessHandle focused_tab_pid_;
 146
 147   // Observer for the kernel low memory signal.  NULL if tab discarding is
 148   // disabled.
 149   scoped_ptr<LowMemoryObserver> low_memory_observer_;
 150
 151   // Wall-clock time when the priority manager started running.
 152   base::TimeTicks start_time_;
 153
 154   // Wall-clock time of last tab discard during this browsing session, or 0 if
 155   // no discard has happened yet.
 156   base::TimeTicks last_discard_time_;
 157
 158   // Wall-clock time of last priority adjustment, used to correct the above
 159   // times for discontinuities caused by suspend/resume.
 160   base::TimeTicks last_adjust_time_;
 161
 162   // Number of times we have discarded a tab, for statistics.
 163   int discard_count_;
 164
 165   // Whether a tab discard event has occurred during the last time interval,
 166   // used for statistics normalized by usage.
 167   bool recent_tab_discard_;
 168
 169   DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
 170 };
 171
 172 }  // namespace chromeos
 173
 174 #endif  // CHROME_BROWSER_CHROMEOS_MEMORY_OOM_PRIORITY_MANAGER_H_