1 /*
2 Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
3 Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
4 Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
5
6 This library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public
8 License as published by the Free Software Foundation; either
9 version 2 of the License, or (at your option) any later version.
10
11 This library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Library General Public License for more details.
15
16 You should have received a copy of the GNU Library General Public License
17 along with this library; see the file COPYING.LIB. If not, write to
18 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
19 Boston, MA 02110-1301, USA.
20
21 This class provides all functionality needed for loading images, style sheets and html
22 pages from the web. It has a memory cache for these objects.
23 */
24
25 #ifndef Cache_h
26 #define Cache_h
27
28 #include "CachePolicy.h"
29 #include "CachedResource.h"
30 #include "PlatformString.h"
31 #include <wtf/HashMap.h>
32 #include <wtf/HashSet.h>
33 #include <wtf/Noncopyable.h>
34 #include <wtf/Vector.h>
35 #include <wtf/text/StringHash.h>
36
37 namespace WebCore {
38
39 class CachedCSSStyleSheet;
40 class CachedResource;
41 class CachedResourceLoader;
42 class KURL;
43 class SecurityOrigin;
44 struct SecurityOriginHash;
45
46 // This cache holds subresources used by Web pages: images, scripts, stylesheets, etc.
47
48 // The cache keeps a flexible but bounded window of dead resources that grows/shrinks
49 // depending on the live resource load. Here's an example of cache growth over time,
50 // with a min dead resource capacity of 25% and a max dead resource capacity of 50%:
51
52 // |-----| Dead: -
53 // |----------| Live: +
54 // --|----------| Cache boundary: | (objects outside this mark have been evicted)
55 // --|----------++++++++++|
56 // -------|-----+++++++++++++++|
57 // -------|-----+++++++++++++++|+++++
58
59 // The behavior of the cache changes in the following way if shouldMakeResourcePurgeableOnEviction
60 // returns true.
61 //
62 // 1. Dead resources in the cache are kept in non-purgeable memory.
63 // 2. When we prune dead resources, instead of freeing them, we mark their memory as purgeable and
64 // keep the resources until the kernel reclaims the purgeable memory.
65 //
66 // By leaving the in-cache dead resources in dirty resident memory, we decrease the likelihood of
67 // the kernel claiming that memory and forcing us to refetch the resource (for example when a user
68 // presses back).
69 //
70 // And by having an unbounded number of resource objects using purgeable memory, we can use as much
71 // memory as is available on the machine. The trade-off here is that the CachedResource object (and
72 // its member variables) are allocated in non-purgeable TC-malloc'd memory so we would see slightly
73 // more memory use due to this.
74
75 class MemoryCache {
76 WTF_MAKE_NONCOPYABLE(MemoryCache); WTF_MAKE_FAST_ALLOCATED;
77 public:
78 friend MemoryCache* memoryCache();
79
80 typedef HashMap<String, CachedResource*> CachedResourceMap;
81
82 struct LRUList {
83 CachedResource* m_head;
84 CachedResource* m_tail;
LRUListLRUList85 LRUList() : m_head(0), m_tail(0) { }
86 };
87
88 struct TypeStatistic {
89 int count;
90 int size;
91 int liveSize;
92 int decodedSize;
93 int purgeableSize;
94 int purgedSize;
TypeStatisticTypeStatistic95 TypeStatistic() : count(0), size(0), liveSize(0), decodedSize(0), purgeableSize(0), purgedSize(0) { }
96 void addResource(CachedResource*);
97 };
98
99 struct Statistics {
100 TypeStatistic images;
101 TypeStatistic cssStyleSheets;
102 TypeStatistic scripts;
103 #if ENABLE(XSLT)
104 TypeStatistic xslStyleSheets;
105 #endif
106 TypeStatistic fonts;
107 };
108
109 CachedResource* resourceForURL(const KURL&);
110
111 bool add(CachedResource* resource);
remove(CachedResource * resource)112 void remove(CachedResource* resource) { evict(resource); }
113
114 static KURL removeFragmentIdentifierIfNeeded(const KURL& originalURL);
115
116 void revalidationSucceeded(CachedResource* revalidatingResource, const ResourceResponse&);
117 void revalidationFailed(CachedResource* revalidatingResource);
118
119 // Sets the cache's memory capacities, in bytes. These will hold only approximately,
120 // since the decoded cost of resources like scripts and stylesheets is not known.
121 // - minDeadBytes: The maximum number of bytes that dead resources should consume when the cache is under pressure.
122 // - maxDeadBytes: The maximum number of bytes that dead resources should consume when the cache is not under pressure.
123 // - totalBytes: The maximum number of bytes that the cache should consume overall.
124 void setCapacities(unsigned minDeadBytes, unsigned maxDeadBytes, unsigned totalBytes);
125
126 // Turn the cache on and off. Disabling the cache will remove all resources from the cache. They may
127 // still live on if they are referenced by some Web page though.
128 void setDisabled(bool);
disabled()129 bool disabled() const { return m_disabled; }
130
131 void evictResources();
132
setPruneEnabled(bool enabled)133 void setPruneEnabled(bool enabled) { m_pruneEnabled = enabled; }
prune()134 void prune()
135 {
136 if (m_liveSize + m_deadSize <= m_capacity && m_maxDeadCapacity && m_deadSize <= m_maxDeadCapacity) // Fast path.
137 return;
138
139 pruneDeadResources(); // Prune dead first, in case it was "borrowing" capacity from live.
140 pruneLiveResources();
141 }
142
setDeadDecodedDataDeletionInterval(double interval)143 void setDeadDecodedDataDeletionInterval(double interval) { m_deadDecodedDataDeletionInterval = interval; }
deadDecodedDataDeletionInterval()144 double deadDecodedDataDeletionInterval() const { return m_deadDecodedDataDeletionInterval; }
145
146 void addCachedResourceLoader(CachedResourceLoader*);
147 void removeCachedResourceLoader(CachedResourceLoader*);
148
149 // Calls to put the cached resource into and out of LRU lists.
150 void insertInLRUList(CachedResource*);
151 void removeFromLRUList(CachedResource*);
152
153 // Called to adjust the cache totals when a resource changes size.
154 void adjustSize(bool live, int delta);
155
156 // Track decoded resources that are in the cache and referenced by a Web page.
157 void insertInLiveDecodedResourcesList(CachedResource*);
158 void removeFromLiveDecodedResourcesList(CachedResource*);
159
160 void addToLiveResourcesSize(CachedResource*);
161 void removeFromLiveResourcesSize(CachedResource*);
162
163 static bool shouldMakeResourcePurgeableOnEviction();
164
165 // Function to collect cache statistics for the caches window in the Safari Debug menu.
166 Statistics getStatistics();
167
168 void resourceAccessed(CachedResource*);
169
170 typedef HashSet<RefPtr<SecurityOrigin>, SecurityOriginHash> SecurityOriginSet;
171 void removeResourcesWithOrigin(SecurityOrigin*);
172 void getOriginsWithCache(SecurityOriginSet& origins);
173
174 private:
175 MemoryCache();
176 ~MemoryCache(); // Not implemented to make sure nobody accidentally calls delete -- WebCore does not delete singletons.
177
178 LRUList* lruListFor(CachedResource*);
179 #ifndef NDEBUG
180 void dumpStats();
181 void dumpLRULists(bool includeLive) const;
182 #endif
183
184 unsigned liveCapacity() const;
185 unsigned deadCapacity() const;
186
187 void pruneDeadResources(); // Flush decoded and encoded data from resources not referenced by Web pages.
188 void pruneLiveResources(); // Flush decoded data from resources still referenced by Web pages.
189
190 bool makeResourcePurgeable(CachedResource*);
191 void evict(CachedResource*);
192
193 bool m_disabled; // Whether or not the cache is enabled.
194 bool m_pruneEnabled;
195 bool m_inPruneDeadResources;
196
197 unsigned m_capacity;
198 unsigned m_minDeadCapacity;
199 unsigned m_maxDeadCapacity;
200 double m_deadDecodedDataDeletionInterval;
201
202 unsigned m_liveSize; // The number of bytes currently consumed by "live" resources in the cache.
203 unsigned m_deadSize; // The number of bytes currently consumed by "dead" resources in the cache.
204
205 // Size-adjusted and popularity-aware LRU list collection for cache objects. This collection can hold
206 // more resources than the cached resource map, since it can also hold "stale" multiple versions of objects that are
207 // waiting to die when the clients referencing them go away.
208 Vector<LRUList, 32> m_allResources;
209
210 // List just for live resources with decoded data. Access to this list is based off of painting the resource.
211 LRUList m_liveDecodedResources;
212
213 // A URL-based map of all resources that are in the cache (including the freshest version of objects that are currently being
214 // referenced by a Web page).
215 HashMap<String, CachedResource*> m_resources;
216 };
217
shouldMakeResourcePurgeableOnEviction()218 inline bool MemoryCache::shouldMakeResourcePurgeableOnEviction()
219 {
220 #if PLATFORM(IOS)
221 return true;
222 #else
223 return false;
224 #endif
225 }
226
227 // Function to obtain the global cache.
228 MemoryCache* memoryCache();
229
230 }
231
232 #endif
233