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
24template<typename Type>
25struct DefaultSingletonTraits;
26class PrefRegistrySimple;
27
28namespace web_cache {
29
30class 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  virtual 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  virtual ~WebCacheManager();
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_
242