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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 // The eviction policy is a very simple pure LRU, so the elements at the end of | |
6 // the list are evicted until kCleanUpMargin free space is available. There is | |
7 // only one list in use (Rankings::NO_USE), and elements are sent to the front | |
8 // of the list whenever they are accessed. | |
9 | |
10 // The new (in-development) eviction policy adds re-use as a factor to evict | |
11 // an entry. The story so far: | |
12 | |
13 // Entries are linked on separate lists depending on how often they are used. | |
14 // When we see an element for the first time, it goes to the NO_USE list; if | |
15 // the object is reused later on, we move it to the LOW_USE list, until it is | |
16 // used kHighUse times, at which point it is moved to the HIGH_USE list. | |
17 // Whenever an element is evicted, we move it to the DELETED list so that if the | |
18 // element is accessed again, we remember the fact that it was already stored | |
19 // and maybe in the future we don't evict that element. | |
20 | |
21 // When we have to evict an element, first we try to use the last element from | |
22 // the NO_USE list, then we move to the LOW_USE and only then we evict an entry | |
23 // from the HIGH_USE. We attempt to keep entries on the cache for at least | |
24 // kTargetTime hours (with frequently accessed items stored for longer periods), | |
25 // but if we cannot do that, we fall-back to keep each list roughly the same | |
26 // size so that we have a chance to see an element again and move it to another | |
27 // list. | |
28 | |
29 #include "net/disk_cache/v3/eviction_v3.h" | |
30 | |
31 #include "base/bind.h" | |
32 #include "base/compiler_specific.h" | |
33 #include "base/logging.h" | |
34 #include "base/message_loop/message_loop.h" | |
35 #include "base/strings/string_util.h" | |
36 #include "base/time/time.h" | |
37 #include "net/disk_cache/experiments.h" | |
38 #include "net/disk_cache/trace.h" | |
39 #include "net/disk_cache/v3/backend_impl_v3.h" | |
40 #include "net/disk_cache/v3/entry_impl_v3.h" | |
41 #include "net/disk_cache/v3/histogram_macros.h" | |
42 | |
43 // Define CACHE_UMA_BACKEND_IMPL_OBJ to be a disk_cache::BackendImpl* in order | |
44 // to use the CACHE_UMA histogram macro. | |
45 #define CACHE_UMA_BACKEND_IMPL_OBJ backend_ | |
46 | |
47 using base::Time; | |
48 using base::TimeTicks; | |
49 | |
50 namespace { | |
51 | |
52 const int kCleanUpMargin = 1024 * 1024; | |
53 | |
54 #if defined(V3_NOT_JUST_YET_READY) | |
55 const int kHighUse = 10; // Reuse count to be on the HIGH_USE list. | |
56 const int kTargetTime = 24 * 7; // Time to be evicted (hours since last use). | |
57 const int kMaxDelayedTrims = 60; | |
58 #endif // defined(V3_NOT_JUST_YET_READY). | |
59 | |
60 int LowWaterAdjust(int high_water) { | |
61 if (high_water < kCleanUpMargin) | |
62 return 0; | |
63 | |
64 return high_water - kCleanUpMargin; | |
65 } | |
66 | |
67 #if defined(V3_NOT_JUST_YET_READY) | |
68 bool FallingBehind(int current_size, int max_size) { | |
69 return current_size > max_size - kCleanUpMargin * 20; | |
70 } | |
71 #endif // defined(V3_NOT_JUST_YET_READY). | |
72 | |
73 } // namespace | |
74 | |
75 namespace disk_cache { | |
76 | |
77 // The real initialization happens during Init(), init_ is the only member that | |
78 // has to be initialized here. | |
79 EvictionV3::EvictionV3() | |
80 : backend_(NULL), | |
81 index_(NULL), | |
82 header_(NULL), | |
83 init_(false), | |
84 ptr_factory_(this) { | |
85 } | |
86 | |
87 EvictionV3::~EvictionV3() { | |
88 } | |
89 | |
90 void EvictionV3::Init(BackendImplV3* backend) { | |
91 // We grab a bunch of info from the backend to make the code a little cleaner | |
92 // when we're actually doing work. | |
93 backend_ = backend; | |
94 index_ = &backend_->index_; | |
95 header_ = index_->header(); | |
96 max_size_ = LowWaterAdjust(backend_->max_size_); | |
97 lru_ = backend->lru_eviction_; | |
98 first_trim_ = true; | |
99 trimming_ = false; | |
100 delay_trim_ = false; | |
101 trim_delays_ = 0; | |
102 init_ = true; | |
103 test_mode_ = false; | |
104 } | |
105 | |
106 void EvictionV3::Stop() { | |
107 // It is possible for the backend initialization to fail, in which case this | |
108 // object was never initialized... and there is nothing to do. | |
109 if (!init_) | |
110 return; | |
111 | |
112 // We want to stop further evictions, so let's pretend that we are busy from | |
113 // this point on. | |
114 DCHECK(!trimming_); | |
115 trimming_ = true; | |
116 ptr_factory_.InvalidateWeakPtrs(); | |
117 } | |
118 | |
119 #if defined(V3_NOT_JUST_YET_READY) | |
120 void EvictionV3::TrimCache() { | |
121 if (backend_->disabled_ || trimming_) | |
122 return; | |
123 | |
124 if (!empty && !ShouldTrim()) | |
125 return PostDelayedTrim(); | |
126 | |
127 if (new_eviction_) | |
128 return TrimCacheV2(empty); | |
129 | |
130 Trace("*** Trim Cache ***"); | |
131 trimming_ = true; | |
132 TimeTicks start = TimeTicks::Now(); | |
133 Rankings::ScopedRankingsBlock node(rankings_); | |
134 Rankings::ScopedRankingsBlock next( | |
135 rankings_, rankings_->GetPrev(node.get(), Rankings::NO_USE)); | |
136 int deleted_entries = 0; | |
137 int target_size = empty ? 0 : max_size_; | |
138 while ((header_->num_bytes > target_size || test_mode_) && next.get()) { | |
139 // The iterator could be invalidated within EvictEntry(). | |
140 if (!next->HasData()) | |
141 break; | |
142 node.reset(next.release()); | |
143 next.reset(rankings_->GetPrev(node.get(), Rankings::NO_USE)); | |
144 if (node->Data()->dirty != backend_->GetCurrentEntryId() || empty) { | |
145 // This entry is not being used by anybody. | |
146 // Do NOT use node as an iterator after this point. | |
147 rankings_->TrackRankingsBlock(node.get(), false); | |
148 if (EvictEntry(node.get(), empty, Rankings::NO_USE) && !test_mode_) | |
149 deleted_entries++; | |
150 | |
151 if (!empty && test_mode_) | |
152 break; | |
153 } | |
154 if (!empty && (deleted_entries > 20 || | |
155 (TimeTicks::Now() - start).InMilliseconds() > 20)) { | |
156 base::MessageLoop::current()->PostTask( | |
157 FROM_HERE, | |
158 base::Bind(&EvictionV3::TrimCache, ptr_factory_.GetWeakPtr(), false)); | |
159 break; | |
160 } | |
161 } | |
162 | |
163 if (empty) { | |
164 CACHE_UMA(AGE_MS, "TotalClearTimeV1", 0, start); | |
165 } else { | |
166 CACHE_UMA(AGE_MS, "TotalTrimTimeV1", 0, start); | |
167 } | |
168 CACHE_UMA(COUNTS, "TrimItemsV1", 0, deleted_entries); | |
169 | |
170 trimming_ = false; | |
171 Trace("*** Trim Cache end ***"); | |
172 return; | |
173 } | |
174 | |
175 void EvictionV3::OnOpenEntry(EntryImplV3* entry) { | |
176 EntryStore* info = entry->entry()->Data(); | |
177 DCHECK_EQ(ENTRY_NORMAL, info->state); | |
178 | |
179 if (info->reuse_count < kint32max) { | |
180 info->reuse_count++; | |
181 entry->entry()->set_modified(); | |
182 | |
183 // We may need to move this to a new list. | |
184 if (1 == info->reuse_count) { | |
185 rankings_->Remove(entry->rankings(), Rankings::NO_USE, true); | |
186 rankings_->Insert(entry->rankings(), false, Rankings::LOW_USE); | |
187 entry->entry()->Store(); | |
188 } else if (kHighUse == info->reuse_count) { | |
189 rankings_->Remove(entry->rankings(), Rankings::LOW_USE, true); | |
190 rankings_->Insert(entry->rankings(), false, Rankings::HIGH_USE); | |
191 entry->entry()->Store(); | |
192 } | |
193 } | |
194 } | |
195 | |
196 void EvictionV3::OnCreateEntry(EntryImplV3* entry) { | |
197 EntryStore* info = entry->entry()->Data(); | |
198 switch (info->state) { | |
199 case ENTRY_NORMAL: { | |
200 DCHECK(!info->reuse_count); | |
201 DCHECK(!info->refetch_count); | |
202 break; | |
203 }; | |
204 case ENTRY_EVICTED: { | |
205 if (info->refetch_count < kint32max) | |
206 info->refetch_count++; | |
207 | |
208 if (info->refetch_count > kHighUse && info->reuse_count < kHighUse) { | |
209 info->reuse_count = kHighUse; | |
210 } else { | |
211 info->reuse_count++; | |
212 } | |
213 info->state = ENTRY_NORMAL; | |
214 entry->entry()->Store(); | |
215 rankings_->Remove(entry->rankings(), Rankings::DELETED, true); | |
216 break; | |
217 }; | |
218 default: | |
219 NOTREACHED(); | |
220 } | |
221 | |
222 rankings_->Insert(entry->rankings(), true, GetListForEntryV2(entry)); | |
223 } | |
224 | |
225 void EvictionV3::SetTestMode() { | |
226 test_mode_ = true; | |
227 } | |
228 | |
229 void EvictionV3::TrimDeletedList(bool empty) { | |
230 DCHECK(test_mode_ && new_eviction_); | |
231 TrimDeleted(empty); | |
232 } | |
233 | |
234 // ----------------------------------------------------------------------- | |
235 | |
236 void EvictionV3::PostDelayedTrim() { | |
237 // Prevent posting multiple tasks. | |
238 if (delay_trim_) | |
239 return; | |
240 delay_trim_ = true; | |
241 trim_delays_++; | |
242 base::MessageLoop::current()->PostDelayedTask( | |
243 FROM_HERE, | |
244 base::Bind(&EvictionV3::DelayedTrim, ptr_factory_.GetWeakPtr()), | |
245 base::TimeDelta::FromMilliseconds(1000)); | |
246 } | |
247 | |
248 void EvictionV3::DelayedTrim() { | |
249 delay_trim_ = false; | |
250 if (trim_delays_ < kMaxDelayedTrims && backend_->IsLoaded()) | |
251 return PostDelayedTrim(); | |
252 | |
253 TrimCache(false); | |
254 } | |
255 | |
256 bool EvictionV3::ShouldTrim() { | |
257 if (!FallingBehind(header_->num_bytes, max_size_) && | |
258 trim_delays_ < kMaxDelayedTrims && backend_->IsLoaded()) { | |
259 return false; | |
260 } | |
261 | |
262 UMA_HISTOGRAM_COUNTS("DiskCache.TrimDelays", trim_delays_); | |
263 trim_delays_ = 0; | |
264 return true; | |
265 } | |
266 | |
267 bool EvictionV3::ShouldTrimDeleted() { | |
268 int index_load = header_->num_entries * 100 / index_size_; | |
269 | |
270 // If the index is not loaded, the deleted list will tend to double the size | |
271 // of the other lists 3 lists (40% of the total). Otherwise, all lists will be | |
272 // about the same size. | |
273 int max_length = (index_load < 25) ? header_->num_entries * 2 / 5 : | |
274 header_->num_entries / 4; | |
275 return (!test_mode_ && header_->lru.sizes[Rankings::DELETED] > max_length); | |
276 } | |
277 | |
278 bool Eviction::EvictEntry(CacheRankingsBlock* node, bool empty, | |
279 Rankings::List list) { | |
280 EntryImplV3* entry = backend_->GetEnumeratedEntry(node, list); | |
281 if (!entry) { | |
282 Trace("NewEntry failed on Trim 0x%x", node->address().value()); | |
283 return false; | |
284 } | |
285 | |
286 ReportTrimTimes(entry); | |
287 if (empty || !new_eviction_) { | |
288 entry->DoomImpl(); | |
289 } else { | |
290 entry->DeleteEntryData(false); | |
291 EntryStore* info = entry->entry()->Data(); | |
292 DCHECK_EQ(ENTRY_NORMAL, info->state); | |
293 | |
294 rankings_->Remove(entry->rankings(), GetListForEntryV2(entry), true); | |
295 info->state = ENTRY_EVICTED; | |
296 entry->entry()->Store(); | |
297 rankings_->Insert(entry->rankings(), true, Rankings::DELETED); | |
298 } | |
299 if (!empty) | |
300 backend_->OnEvent(Stats::TRIM_ENTRY); | |
301 | |
302 entry->Release(); | |
303 | |
304 return true; | |
305 } | |
306 | |
307 void EvictionV3::TrimCacheV2(bool empty) { | |
308 Trace("*** Trim Cache ***"); | |
309 trimming_ = true; | |
310 TimeTicks start = TimeTicks::Now(); | |
311 | |
312 const int kListsToSearch = 3; | |
313 Rankings::ScopedRankingsBlock next[kListsToSearch]; | |
314 int list = Rankings::LAST_ELEMENT; | |
315 | |
316 // Get a node from each list. | |
317 for (int i = 0; i < kListsToSearch; i++) { | |
318 bool done = false; | |
319 next[i].set_rankings(rankings_); | |
320 if (done) | |
321 continue; | |
322 next[i].reset(rankings_->GetPrev(NULL, static_cast<Rankings::List>(i))); | |
323 if (!empty && NodeIsOldEnough(next[i].get(), i)) { | |
324 list = static_cast<Rankings::List>(i); | |
325 done = true; | |
326 } | |
327 } | |
328 | |
329 // If we are not meeting the time targets lets move on to list length. | |
330 if (!empty && Rankings::LAST_ELEMENT == list) | |
331 list = SelectListByLength(next); | |
332 | |
333 if (empty) | |
334 list = 0; | |
335 | |
336 Rankings::ScopedRankingsBlock node(rankings_); | |
337 int deleted_entries = 0; | |
338 int target_size = empty ? 0 : max_size_; | |
339 | |
340 for (; list < kListsToSearch; list++) { | |
341 while ((header_->num_bytes > target_size || test_mode_) && | |
342 next[list].get()) { | |
343 // The iterator could be invalidated within EvictEntry(). | |
344 if (!next[list]->HasData()) | |
345 break; | |
346 node.reset(next[list].release()); | |
347 next[list].reset(rankings_->GetPrev(node.get(), | |
348 static_cast<Rankings::List>(list))); | |
349 if (node->Data()->dirty != backend_->GetCurrentEntryId() || empty) { | |
350 // This entry is not being used by anybody. | |
351 // Do NOT use node as an iterator after this point. | |
352 rankings_->TrackRankingsBlock(node.get(), false); | |
353 if (EvictEntry(node.get(), empty, static_cast<Rankings::List>(list))) | |
354 deleted_entries++; | |
355 | |
356 if (!empty && test_mode_) | |
357 break; | |
358 } | |
359 if (!empty && (deleted_entries > 20 || | |
360 (TimeTicks::Now() - start).InMilliseconds() > 20)) { | |
361 base::MessageLoop::current()->PostTask( | |
362 FROM_HERE, | |
363 base::Bind(&Eviction::TrimCache, ptr_factory_.GetWeakPtr(), false)); | |
364 break; | |
365 } | |
366 } | |
367 if (!empty) | |
368 list = kListsToSearch; | |
369 } | |
370 | |
371 if (empty) { | |
372 TrimDeleted(true); | |
373 } else if (ShouldTrimDeleted()) { | |
374 base::MessageLoop::current()->PostTask( | |
375 FROM_HERE, | |
376 base::Bind(&EvictionV3::TrimDeleted, ptr_factory_.GetWeakPtr(), empty)); | |
377 } | |
378 | |
379 if (empty) { | |
380 CACHE_UMA(AGE_MS, "TotalClearTimeV2", 0, start); | |
381 } else { | |
382 CACHE_UMA(AGE_MS, "TotalTrimTimeV2", 0, start); | |
383 } | |
384 CACHE_UMA(COUNTS, "TrimItemsV2", 0, deleted_entries); | |
385 | |
386 Trace("*** Trim Cache end ***"); | |
387 trimming_ = false; | |
388 return; | |
389 } | |
390 | |
391 // This is a minimal implementation that just discards the oldest nodes. | |
392 // TODO(rvargas): Do something better here. | |
393 void EvictionV3::TrimDeleted(bool empty) { | |
394 Trace("*** Trim Deleted ***"); | |
395 if (backend_->disabled_) | |
396 return; | |
397 | |
398 TimeTicks start = TimeTicks::Now(); | |
399 Rankings::ScopedRankingsBlock node(rankings_); | |
400 Rankings::ScopedRankingsBlock next( | |
401 rankings_, rankings_->GetPrev(node.get(), Rankings::DELETED)); | |
402 int deleted_entries = 0; | |
403 while (next.get() && | |
404 (empty || (deleted_entries < 20 && | |
405 (TimeTicks::Now() - start).InMilliseconds() < 20))) { | |
406 node.reset(next.release()); | |
407 next.reset(rankings_->GetPrev(node.get(), Rankings::DELETED)); | |
408 if (RemoveDeletedNode(node.get())) | |
409 deleted_entries++; | |
410 if (test_mode_) | |
411 break; | |
412 } | |
413 | |
414 if (deleted_entries && !empty && ShouldTrimDeleted()) { | |
415 base::MessageLoop::current()->PostTask( | |
416 FROM_HERE, | |
417 base::Bind(&EvictionV3::TrimDeleted, ptr_factory_.GetWeakPtr(), false)); | |
418 } | |
419 | |
420 CACHE_UMA(AGE_MS, "TotalTrimDeletedTime", 0, start); | |
421 CACHE_UMA(COUNTS, "TrimDeletedItems", 0, deleted_entries); | |
422 Trace("*** Trim Deleted end ***"); | |
423 return; | |
424 } | |
425 | |
426 void EvictionV3::ReportTrimTimes(EntryImplV3* entry) { | |
427 if (first_trim_) { | |
428 first_trim_ = false; | |
429 if (backend_->ShouldReportAgain()) { | |
430 CACHE_UMA(AGE, "TrimAge", 0, entry->GetLastUsed()); | |
431 ReportListStats(); | |
432 } | |
433 | |
434 if (header_->lru.filled) | |
435 return; | |
436 | |
437 header_->lru.filled = 1; | |
438 | |
439 if (header_->create_time) { | |
440 // This is the first entry that we have to evict, generate some noise. | |
441 backend_->FirstEviction(); | |
442 } else { | |
443 // This is an old file, but we may want more reports from this user so | |
444 // lets save some create_time. | |
445 Time::Exploded old = {0}; | |
446 old.year = 2009; | |
447 old.month = 3; | |
448 old.day_of_month = 1; | |
449 header_->create_time = Time::FromLocalExploded(old).ToInternalValue(); | |
450 } | |
451 } | |
452 } | |
453 | |
454 bool EvictionV3::NodeIsOldEnough(CacheRankingsBlock* node, int list) { | |
455 if (!node) | |
456 return false; | |
457 | |
458 // If possible, we want to keep entries on each list at least kTargetTime | |
459 // hours. Each successive list on the enumeration has 2x the target time of | |
460 // the previous list. | |
461 Time used = Time::FromInternalValue(node->Data()->last_used); | |
462 int multiplier = 1 << list; | |
463 return (Time::Now() - used).InHours() > kTargetTime * multiplier; | |
464 } | |
465 | |
466 int EvictionV3::SelectListByLength(Rankings::ScopedRankingsBlock* next) { | |
467 int data_entries = header_->num_entries - | |
468 header_->lru.sizes[Rankings::DELETED]; | |
469 // Start by having each list to be roughly the same size. | |
470 if (header_->lru.sizes[0] > data_entries / 3) | |
471 return 0; | |
472 | |
473 int list = (header_->lru.sizes[1] > data_entries / 3) ? 1 : 2; | |
474 | |
475 // Make sure that frequently used items are kept for a minimum time; we know | |
476 // that this entry is not older than its current target, but it must be at | |
477 // least older than the target for list 0 (kTargetTime), as long as we don't | |
478 // exhaust list 0. | |
479 if (!NodeIsOldEnough(next[list].get(), 0) && | |
480 header_->lru.sizes[0] > data_entries / 10) | |
481 list = 0; | |
482 | |
483 return list; | |
484 } | |
485 | |
486 void EvictionV3::ReportListStats() { | |
487 if (!new_eviction_) | |
488 return; | |
489 | |
490 Rankings::ScopedRankingsBlock last1(rankings_, | |
491 rankings_->GetPrev(NULL, Rankings::NO_USE)); | |
492 Rankings::ScopedRankingsBlock last2(rankings_, | |
493 rankings_->GetPrev(NULL, Rankings::LOW_USE)); | |
494 Rankings::ScopedRankingsBlock last3(rankings_, | |
495 rankings_->GetPrev(NULL, Rankings::HIGH_USE)); | |
496 Rankings::ScopedRankingsBlock last4(rankings_, | |
497 rankings_->GetPrev(NULL, Rankings::DELETED)); | |
498 | |
499 if (last1.get()) | |
500 CACHE_UMA(AGE, "NoUseAge", 0, | |
501 Time::FromInternalValue(last1.get()->Data()->last_used)); | |
502 if (last2.get()) | |
503 CACHE_UMA(AGE, "LowUseAge", 0, | |
504 Time::FromInternalValue(last2.get()->Data()->last_used)); | |
505 if (last3.get()) | |
506 CACHE_UMA(AGE, "HighUseAge", 0, | |
507 Time::FromInternalValue(last3.get()->Data()->last_used)); | |
508 if (last4.get()) | |
509 CACHE_UMA(AGE, "DeletedAge", 0, | |
510 Time::FromInternalValue(last4.get()->Data()->last_used)); | |
511 } | |
512 #endif // defined(V3_NOT_JUST_YET_READY). | |
513 | |
514 } // namespace disk_cache | |
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