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 namespace base {
  25 template<typename Type>
  26 struct DefaultSingletonTraits;
  27 }  // namespace base
  28
  29 class PrefRegistrySimple;
  30
  31 namespace web_cache {
  32
  33 class WebCacheManager : public content::NotificationObserver {
  34   friend class WebCacheManagerTest;
  35   FRIEND_TEST_ALL_PREFIXES(
  36       WebCacheManagerTest,
  37       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_1);
  38   FRIEND_TEST_ALL_PREFIXES(
  39       WebCacheManagerTest,
  40       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_2);
  41   FRIEND_TEST_ALL_PREFIXES(
  42       WebCacheManagerTest,
  43       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_3);
  44   FRIEND_TEST_ALL_PREFIXES(
  45       WebCacheManagerTest,
  46       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_4);
  47   FRIEND_TEST_ALL_PREFIXES(
  48       WebCacheManagerTest,
  49       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_5);
  50   FRIEND_TEST_ALL_PREFIXES(
  51       WebCacheManagerTest,
  52       CallRemoveRendererAndObserveActivityInAnyOrderShouldNotCrashTest_6);
  53
  54  public:
  55   // Gets the singleton WebCacheManager object.  The first time this method
  56   // is called, a WebCacheManager object is constructed and returned.
  57   // Subsequent calls will return the same object.
  58   static WebCacheManager* GetInstance();
  59
  60   // When a render process is created, it registers itself with the cache
  61   // manager host, causing the renderer to be allocated cache resources.
  62   void Add(int renderer_id);
  63
  64   // When a render process ends, it removes itself from the cache manager host,
  65   // freeing the manager to assign its cache resources to other renderers.
  66   void Remove(int renderer_id);
  67
  68   // The cache manager assigns more cache resources to active renderer.  When a
  69   // renderer is active, it should inform the cache manager to receive more
  70   // cache resources.
  71   //
  72   // When a renderer moves from being inactive to being active, the cache
  73   // manager may decide to adjust its resource allocation, but it will delay
  74   // the recalculation, allowing ObserveActivity to return quickly.
  75   void ObserveActivity(int renderer_id);
  76
  77   // Periodically, renderers should inform the cache manager of their current
  78   // statistics.  The more up-to-date the cache manager's statistics, the
  79   // better it can allocate cache resources.
  80   void ObserveStats(
  81       int renderer_id, const blink::WebCache::UsageStats& stats);
  82
  83   // The global limit on the number of bytes in all the in-memory caches.
  84   size_t global_size_limit() const { return global_size_limit_; }
  85
  86   // Sets the global size limit, forcing a recalculation of cache allocations.
  87   void SetGlobalSizeLimit(size_t bytes);
  88
  89   // Clears all in-memory caches.
  90   void ClearCache();
  91
  92   // Instantly clears renderer cache for a process.
  93   void ClearCacheForProcess(int process_id);
  94
  95   // Clears all in-memory caches when a tab is reloaded or the user navigates
  96   // to a different website.
  97   void ClearCacheOnNavigation();
  98
  99   // content::NotificationObserver implementation:
 100   void Observe(int type,
 101                const content::NotificationSource& source,
 102                const content::NotificationDetails& details) override;
 103
 104   // Gets the default global size limit.  This interrogates system metrics to
 105   // tune the default size to the current system.
 106   static size_t GetDefaultGlobalSizeLimit();
 107
 108  protected:
 109   // The amount of idle time before we consider a tab to be "inactive"
 110   static const int kRendererInactiveThresholdMinutes = 5;
 111
 112   // Keep track of some renderer information.
 113   struct RendererInfo : blink::WebCache::UsageStats {
 114     // The access time for this renderer.
 115     base::Time access;
 116   };
 117
 118   typedef std::map<int, RendererInfo> StatsMap;
 119
 120   // An allocation is the number of bytes a specific renderer should use for
 121   // its cache.
 122   typedef std::pair<int,size_t> Allocation;
 123
 124   // An allocation strategy is a list of allocations specifying the resources
 125   // each renderer is permitted to consume for its cache.
 126   typedef std::list<Allocation> AllocationStrategy;
 127
 128   // This class is a singleton.  Do not instantiate directly.
 129   WebCacheManager();
 130   friend struct base::DefaultSingletonTraits<WebCacheManager>;
 131
 132   ~WebCacheManager() override;
 133
 134   // Recomputes the allocation of cache resources among the renderers.  Also
 135   // informs the renderers of their new allocation.
 136   void ReviseAllocationStrategy();
 137
 138   // Schedules a call to ReviseAllocationStrategy after a short delay.
 139   void ReviseAllocationStrategyLater();
 140
 141   // The various tactics used as part of an allocation strategy.  To decide
 142   // how many resources a given renderer should be allocated, we consider its
 143   // usage statistics.  Each tactic specifies the function that maps usage
 144   // statistics to resource allocations.
 145   //
 146   // Determining a resource allocation strategy amounts to picking a tactic
 147   // for each renderer and checking that the total memory required fits within
 148   // our |global_size_limit_|.
 149   enum AllocationTactic {
 150     // Ignore cache statistics and divide resources equally among the given
 151     // set of caches.
 152     DIVIDE_EVENLY,
 153
 154     // Allow each renderer to keep its current set of cached resources, with
 155     // some extra allocation to store new objects.
 156     KEEP_CURRENT_WITH_HEADROOM,
 157
 158     // Allow each renderer to keep its current set of cached resources.
 159     KEEP_CURRENT,
 160
 161     // Allow each renderer to keep cache resources it believes are currently
 162     // being used, with some extra allocation to store new objects.
 163     KEEP_LIVE_WITH_HEADROOM,
 164
 165     // Allow each renderer to keep cache resources it believes are currently
 166     // being used, but instruct the renderer to discard all other data.
 167     KEEP_LIVE,
 168   };
 169
 170   // Helper functions for devising an allocation strategy
 171
 172   // Add up all the stats from the given set of renderers and place the result
 173   // in |stats|.
 174   void GatherStats(const std::set<int>& renderers,
 175                    blink::WebCache::UsageStats* stats);
 176
 177   // Get the amount of memory that would be required to implement |tactic|
 178   // using the specified allocation tactic.  This function defines the
 179   // semantics for each of the tactics.
 180   static size_t GetSize(AllocationTactic tactic,
 181                         const blink::WebCache::UsageStats& stats);
 182
 183   // Attempt to use the specified tactics to compute an allocation strategy
 184   // and place the result in |strategy|.  |active_stats| and |inactive_stats|
 185   // are the aggregate statistics for |active_renderers_| and
 186   // |inactive_renderers_|, respectively.
 187   //
 188   // Returns |true| on success and |false| on failure.  Does not modify
 189   // |strategy| on failure.
 190   bool AttemptTactic(AllocationTactic active_tactic,
 191                      const blink::WebCache::UsageStats& active_stats,
 192                      AllocationTactic inactive_tactic,
 193                      const blink::WebCache::UsageStats& inactive_stats,
 194                      AllocationStrategy* strategy);
 195
 196   // For each renderer in |renderers|, computes its allocation according to
 197   // |tactic| and add the result to |strategy|.  Any |extra_bytes_to_allocate|
 198   // is divided evenly among the renderers.
 199   void AddToStrategy(const std::set<int>& renderers,
 200                      AllocationTactic tactic,
 201                      size_t extra_bytes_to_allocate,
 202                      AllocationStrategy* strategy);
 203
 204   // Enact an allocation strategy by informing the renderers of their
 205   // allocations according to |strategy|.
 206   void EnactStrategy(const AllocationStrategy& strategy);
 207
 208   enum ClearCacheOccasion {
 209     // Instructs to clear the cache instantly.
 210     INSTANTLY,
 211     // Instructs to clear the cache when a navigation takes place (this
 212     // includes reloading a tab).
 213     ON_NAVIGATION
 214   };
 215
 216   // Inform all |renderers| to clear their cache.
 217   void ClearRendererCache(const std::set<int>& renderers,
 218                           ClearCacheOccasion occation);
 219
 220   // Check to see if any active renderers have fallen inactive.
 221   void FindInactiveRenderers();
 222
 223   // The global size limit for all in-memory caches.
 224   size_t global_size_limit_;
 225
 226   // Maps every renderer_id our most recent copy of its statistics.
 227   StatsMap stats_;
 228
 229   // Every renderer we think is still around is in one of these two sets.
 230   //
 231   // Active renderers are those renderers that have been active more recently
 232   // than they have been inactive.
 233   std::set<int> active_renderers_;
 234   // Inactive renderers are those renderers that have been inactive more
 235   // recently than they have been active.
 236   std::set<int> inactive_renderers_;
 237
 238   content::NotificationRegistrar registrar_;
 239
 240   base::WeakPtrFactory<WebCacheManager> weak_factory_;
 241
 242   DISALLOW_COPY_AND_ASSIGN(WebCacheManager);
 243 };
 244
 245 }  // namespace web_cache
 246
 247 #endif  // COMPONENTS_WEB_CACHE_BROWSER_WEB_CACHE_MANAGER_H_