components/web_cache/browser/web_cache_manager.h

   1 // Copyright (c) 2011 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 // This is the browser side of the cache manager, it tracks the activity of the
   6 // render processes and allocates available memory cache resources.
   7
   8 #ifndef COMPONENTS_WEB_CACHE_BROWSER_WEB_CACHE_MANAGER_H_
   9 #define COMPONENTS_WEB_CACHE_BROWSER_WEB_CACHE_MANAGER_H_
  10
  11 #include <list>
  12 #include <map>
  13 #include <set>
  14
  15 #include "base/basictypes.h"
  16 #include "base/compiler_specific.h"
  17 #include "base/gtest_prod_util.h"
  18 #include "base/memory/weak_ptr.h"
  19 #include "base/time/time.h"
  20 #include "content/public/browser/notification_observer.h"
  21 #include "content/public/browser/notification_registrar.h"
  22 #include "third_party/WebKit/public/web/WebCache.h"
  23
  24 template<typename Type>
  25 struct DefaultSingletonTraits;
  26 class PrefRegistrySimple;
  27
  28 namespace web_cache {
  29
  30 class WebCacheManager : public content::NotificationObserver {
  31   friend class WebCacheManagerTest;
  32   FRIEND_TEST_ALL_PREFIXES(
  33       WebCacheManagerTest,
  34       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_1);
  35   FRIEND_TEST_ALL_PREFIXES(
  36       WebCacheManagerTest,
  37       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_2);
  38   FRIEND_TEST_ALL_PREFIXES(
  39       WebCacheManagerTest,
  40       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_3);
  41   FRIEND_TEST_ALL_PREFIXES(
  42       WebCacheManagerTest,
  43       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_4);
  44   FRIEND_TEST_ALL_PREFIXES(
  45       WebCacheManagerTest,
  46       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_5);
  47   FRIEND_TEST_ALL_PREFIXES(
  48       WebCacheManagerTest,
  49       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_6);
  50
  51  public:
  52   // Gets the singleton WebCacheManager object.  The first time this method
  53   // is called, a WebCacheManager object is constructed and returned.
  54   // Subsequent calls will return the same object.
  55   static WebCacheManager* GetInstance();
  56
  57   // When a render process is created, it registers itself with the cache
  58   // manager host, causing the renderer to be allocated cache resources.
  59   void Add(int renderer_id);
  60
  61   // When a render process ends, it removes itself from the cache manager host,
  62   // freeing the manager to assign its cache resources to other renderers.
  63   void Remove(int renderer_id);
  64
  65   // The cache manager assigns more cache resources to active renderer.  When a
  66   // renderer is active, it should inform the cache manager to receive more
  67   // cache resources.
  68   //
  69   // When a renderer moves from being inactive to being active, the cache
  70   // manager may decide to adjust its resource allocation, but it will delay
  71   // the recalculation, allowing ObserveActivity to return quickly.
  72   void ObserveActivity(int renderer_id);
  73
  74   // Periodically, renderers should inform the cache manager of their current
  75   // statistics.  The more up-to-date the cache manager's statistics, the
  76   // better it can allocate cache resources.
  77   void ObserveStats(
  78       int renderer_id, const blink::WebCache::UsageStats& stats);
  79
  80   // The global limit on the number of bytes in all the in-memory caches.
  81   size_t global_size_limit() const { return global_size_limit_; }
  82
  83   // Sets the global size limit, forcing a recalculation of cache allocations.
  84   void SetGlobalSizeLimit(size_t bytes);
  85
  86   // Clears all in-memory caches.
  87   void ClearCache();
  88
  89   // Clears all in-memory caches when a tab is reloaded or the user navigates
  90   // to a different website.
  91   void ClearCacheOnNavigation();
  92
  93   // content::NotificationObserver implementation:
  94   void Observe(int type,
  95                const content::NotificationSource& source,
  96                const content::NotificationDetails& details) override;
  97
  98   // Gets the default global size limit.  This interrogates system metrics to
  99   // tune the default size to the current system.
 100   static size_t GetDefaultGlobalSizeLimit();
 101
 102  protected:
 103   // The amount of idle time before we consider a tab to be "inactive"
 104   static const int kRendererInactiveThresholdMinutes = 5;
 105
 106   // Keep track of some renderer information.
 107   struct RendererInfo : blink::WebCache::UsageStats {
 108     // The access time for this renderer.
 109     base::Time access;
 110   };
 111
 112   typedef std::map<int, RendererInfo> StatsMap;
 113
 114   // An allocation is the number of bytes a specific renderer should use for
 115   // its cache.
 116   typedef std::pair<int,size_t> Allocation;
 117
 118   // An allocation strategy is a list of allocations specifying the resources
 119   // each renderer is permitted to consume for its cache.
 120   typedef std::list<Allocation> AllocationStrategy;
 121
 122   // This class is a singleton.  Do not instantiate directly.
 123   WebCacheManager();
 124   friend struct DefaultSingletonTraits<WebCacheManager>;
 125
 126   ~WebCacheManager() override;
 127
 128   // Recomputes the allocation of cache resources among the renderers.  Also
 129   // informs the renderers of their new allocation.
 130   void ReviseAllocationStrategy();
 131
 132   // Schedules a call to ReviseAllocationStrategy after a short delay.
 133   void ReviseAllocationStrategyLater();
 134
 135   // The various tactics used as part of an allocation strategy.  To decide
 136   // how many resources a given renderer should be allocated, we consider its
 137   // usage statistics.  Each tactic specifies the function that maps usage
 138   // statistics to resource allocations.
 139   //
 140   // Determining a resource allocation strategy amounts to picking a tactic
 141   // for each renderer and checking that the total memory required fits within
 142   // our |global_size_limit_|.
 143   enum AllocationTactic {
 144     // Ignore cache statistics and divide resources equally among the given
 145     // set of caches.
 146     DIVIDE_EVENLY,
 147
 148     // Allow each renderer to keep its current set of cached resources, with
 149     // some extra allocation to store new objects.
 150     KEEP_CURRENT_WITH_HEADROOM,
 151
 152     // Allow each renderer to keep its current set of cached resources.
 153     KEEP_CURRENT,
 154
 155     // Allow each renderer to keep cache resources it believes are currently
 156     // being used, with some extra allocation to store new objects.
 157     KEEP_LIVE_WITH_HEADROOM,
 158
 159     // Allow each renderer to keep cache resources it believes are currently
 160     // being used, but instruct the renderer to discard all other data.
 161     KEEP_LIVE,
 162   };
 163
 164   // Helper functions for devising an allocation strategy
 165
 166   // Add up all the stats from the given set of renderers and place the result
 167   // in |stats|.
 168   void GatherStats(const std::set<int>& renderers,
 169                    blink::WebCache::UsageStats* stats);
 170
 171   // Get the amount of memory that would be required to implement |tactic|
 172   // using the specified allocation tactic.  This function defines the
 173   // semantics for each of the tactics.
 174   static size_t GetSize(AllocationTactic tactic,
 175                         const blink::WebCache::UsageStats& stats);
 176
 177   // Attempt to use the specified tactics to compute an allocation strategy
 178   // and place the result in |strategy|.  |active_stats| and |inactive_stats|
 179   // are the aggregate statistics for |active_renderers_| and
 180   // |inactive_renderers_|, respectively.
 181   //
 182   // Returns |true| on success and |false| on failure.  Does not modify
 183   // |strategy| on failure.
 184   bool AttemptTactic(AllocationTactic active_tactic,
 185                      const blink::WebCache::UsageStats& active_stats,
 186                      AllocationTactic inactive_tactic,
 187                      const blink::WebCache::UsageStats& inactive_stats,
 188                      AllocationStrategy* strategy);
 189
 190   // For each renderer in |renderers|, computes its allocation according to
 191   // |tactic| and add the result to |strategy|.  Any |extra_bytes_to_allocate|
 192   // is divided evenly among the renderers.
 193   void AddToStrategy(const std::set<int>& renderers,
 194                      AllocationTactic tactic,
 195                      size_t extra_bytes_to_allocate,
 196                      AllocationStrategy* strategy);
 197
 198   // Enact an allocation strategy by informing the renderers of their
 199   // allocations according to |strategy|.
 200   void EnactStrategy(const AllocationStrategy& strategy);
 201
 202   enum ClearCacheOccasion {
 203     // Instructs to clear the cache instantly.
 204     INSTANTLY,
 205     // Instructs to clear the cache when a navigation takes place (this
 206     // includes reloading a tab).
 207     ON_NAVIGATION
 208   };
 209
 210   // Inform all |renderers| to clear their cache.
 211   void ClearRendererCache(const std::set<int>& renderers,
 212                           ClearCacheOccasion occation);
 213
 214   // Check to see if any active renderers have fallen inactive.
 215   void FindInactiveRenderers();
 216
 217   // The global size limit for all in-memory caches.
 218   size_t global_size_limit_;
 219
 220   // Maps every renderer_id our most recent copy of its statistics.
 221   StatsMap stats_;
 222
 223   // Every renderer we think is still around is in one of these two sets.
 224   //
 225   // Active renderers are those renderers that have been active more recently
 226   // than they have been inactive.
 227   std::set<int> active_renderers_;
 228   // Inactive renderers are those renderers that have been inactive more
 229   // recently than they have been active.
 230   std::set<int> inactive_renderers_;
 231
 232   content::NotificationRegistrar registrar_;
 233
 234   base::WeakPtrFactory<WebCacheManager> weak_factory_;
 235
 236   DISALLOW_COPY_AND_ASSIGN(WebCacheManager);
 237 };
 238
 239 }  // namespace web_cache
 240
 241 #endif  // COMPONENTS_WEB_CACHE_BROWSER_WEB_CACHE_MANAGER_H_