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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/blockfile/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/blockfile/backend_impl_v3.h" | |
38 #include "net/disk_cache/blockfile/entry_impl_v3.h" | |
39 #include "net/disk_cache/blockfile/experiments.h" | |
40 #include "net/disk_cache/blockfile/histogram_macros_v3.h" | |
41 #include "net/disk_cache/blockfile/trace.h" | |
42 | |
43 #define CACHE_UMA_BACKEND_IMPL_OBJ backend_ | |
44 | |
45 using base::Time; | |
46 using base::TimeTicks; | |
47 | |
48 namespace { | |
49 | |
50 const int kCleanUpMargin = 1024 * 1024; | |
51 | |
52 #if defined(V3_NOT_JUST_YET_READY) | |
53 const int kHighUse = 10; // Reuse count to be on the HIGH_USE list. | |
54 const int kTargetTime = 24 * 7; // Time to be evicted (hours since last use). | |
55 const int kMaxDelayedTrims = 60; | |
56 #endif // defined(V3_NOT_JUST_YET_READY). | |
57 | |
58 int LowWaterAdjust(int high_water) { | |
59 if (high_water < kCleanUpMargin) | |
60 return 0; | |
61 | |
62 return high_water - kCleanUpMargin; | |
63 } | |
64 | |
65 #if defined(V3_NOT_JUST_YET_READY) | |
66 bool FallingBehind(int current_size, int max_size) { | |
67 return current_size > max_size - kCleanUpMargin * 20; | |
68 } | |
69 #endif // defined(V3_NOT_JUST_YET_READY). | |
70 | |
71 } // namespace | |
72 | |
73 namespace disk_cache { | |
74 | |
75 // The real initialization happens during Init(), init_ is the only member that | |
76 // has to be initialized here. | |
77 EvictionV3::EvictionV3() | |
78 : backend_(NULL), | |
79 index_(NULL), | |
80 header_(NULL), | |
81 init_(false), | |
82 ptr_factory_(this) { | |
83 } | |
84 | |
85 EvictionV3::~EvictionV3() { | |
86 } | |
87 | |
88 void EvictionV3::Init(BackendImplV3* backend) { | |
89 // We grab a bunch of info from the backend to make the code a little cleaner | |
90 // when we're actually doing work. | |
91 backend_ = backend; | |
92 index_ = &backend_->index_; | |
93 header_ = index_->header(); | |
94 max_size_ = LowWaterAdjust(backend_->max_size_); | |
95 lru_ = backend->lru_eviction_; | |
96 first_trim_ = true; | |
97 trimming_ = false; | |
98 delay_trim_ = false; | |
99 trim_delays_ = 0; | |
100 init_ = true; | |
101 test_mode_ = false; | |
102 } | |
103 | |
104 void EvictionV3::Stop() { | |
105 // It is possible for the backend initialization to fail, in which case this | |
106 // object was never initialized... and there is nothing to do. | |
107 if (!init_) | |
108 return; | |
109 | |
110 // We want to stop further evictions, so let's pretend that we are busy from | |
111 // this point on. | |
112 DCHECK(!trimming_); | |
113 trimming_ = true; | |
114 ptr_factory_.InvalidateWeakPtrs(); | |
115 } | |
116 | |
117 #if defined(V3_NOT_JUST_YET_READY) | |
118 void EvictionV3::TrimCache() { | |
119 if (backend_->disabled_ || trimming_) | |
120 return; | |
121 | |
122 if (!empty && !ShouldTrim()) | |
123 return PostDelayedTrim(); | |
124 | |
125 if (new_eviction_) | |
126 return TrimCacheV2(empty); | |
127 | |
128 Trace("*** Trim Cache ***"); | |
129 trimming_ = true; | |
130 TimeTicks start = TimeTicks::Now(); | |
131 Rankings::ScopedRankingsBlock node(rankings_); | |
132 Rankings::ScopedRankingsBlock next( | |
133 rankings_, rankings_->GetPrev(node.get(), Rankings::NO_USE)); | |
134 int deleted_entries = 0; | |
135 int target_size = empty ? 0 : max_size_; | |
136 while ((header_->num_bytes > target_size || test_mode_) && next.get()) { | |
137 // The iterator could be invalidated within EvictEntry(). | |
138 if (!next->HasData()) | |
139 break; | |
140 node.reset(next.release()); | |
141 next.reset(rankings_->GetPrev(node.get(), Rankings::NO_USE)); | |
142 if (node->Data()->dirty != backend_->GetCurrentEntryId() || empty) { | |
143 // This entry is not being used by anybody. | |
144 // Do NOT use node as an iterator after this point. | |
145 rankings_->TrackRankingsBlock(node.get(), false); | |
146 if (EvictEntry(node.get(), empty, Rankings::NO_USE) && !test_mode_) | |
147 deleted_entries++; | |
148 | |
149 if (!empty && test_mode_) | |
150 break; | |
151 } | |
152 if (!empty && (deleted_entries > 20 || | |
153 (TimeTicks::Now() - start).InMilliseconds() > 20)) { | |
154 base::MessageLoop::current()->PostTask( | |
155 FROM_HERE, | |
156 base::Bind(&EvictionV3::TrimCache, ptr_factory_.GetWeakPtr(), false)); | |
157 break; | |
158 } | |
159 } | |
160 | |
161 if (empty) { | |
162 CACHE_UMA(AGE_MS, "TotalClearTimeV1", 0, start); | |
163 } else { | |
164 CACHE_UMA(AGE_MS, "TotalTrimTimeV1", 0, start); | |
165 } | |
166 CACHE_UMA(COUNTS, "TrimItemsV1", 0, deleted_entries); | |
167 | |
168 trimming_ = false; | |
169 Trace("*** Trim Cache end ***"); | |
170 return; | |
171 } | |
172 | |
173 void EvictionV3::OnOpenEntry(EntryImplV3* entry) { | |
174 EntryStore* info = entry->entry()->Data(); | |
175 DCHECK_EQ(ENTRY_NORMAL, info->state); | |
176 | |
177 if (info->reuse_count < kint32max) { | |
178 info->reuse_count++; | |
179 entry->entry()->set_modified(); | |
180 | |
181 // We may need to move this to a new list. | |
182 if (1 == info->reuse_count) { | |
183 rankings_->Remove(entry->rankings(), Rankings::NO_USE, true); | |
184 rankings_->Insert(entry->rankings(), false, Rankings::LOW_USE); | |
185 entry->entry()->Store(); | |
186 } else if (kHighUse == info->reuse_count) { | |
187 rankings_->Remove(entry->rankings(), Rankings::LOW_USE, true); | |
188 rankings_->Insert(entry->rankings(), false, Rankings::HIGH_USE); | |
189 entry->entry()->Store(); | |
190 } | |
191 } | |
192 } | |
193 | |
194 void EvictionV3::OnCreateEntry(EntryImplV3* entry) { | |
195 EntryStore* info = entry->entry()->Data(); | |
196 switch (info->state) { | |
197 case ENTRY_NORMAL: { | |
198 DCHECK(!info->reuse_count); | |
199 DCHECK(!info->refetch_count); | |
200 break; | |
201 }; | |
202 case ENTRY_EVICTED: { | |
203 if (info->refetch_count < kint32max) | |
204 info->refetch_count++; | |
205 | |
206 if (info->refetch_count > kHighUse && info->reuse_count < kHighUse) { | |
207 info->reuse_count = kHighUse; | |
208 } else { | |
209 info->reuse_count++; | |
210 } | |
211 info->state = ENTRY_NORMAL; | |
212 entry->entry()->Store(); | |
213 rankings_->Remove(entry->rankings(), Rankings::DELETED, true); | |
214 break; | |
215 }; | |
216 default: | |
217 NOTREACHED(); | |
218 } | |
219 | |
220 rankings_->Insert(entry->rankings(), true, GetListForEntryV2(entry)); | |
221 } | |
222 | |
223 void EvictionV3::SetTestMode() { | |
224 test_mode_ = true; | |
225 } | |
226 | |
227 void EvictionV3::TrimDeletedList(bool empty) { | |
228 DCHECK(test_mode_ && new_eviction_); | |
229 TrimDeleted(empty); | |
230 } | |
231 | |
232 // ----------------------------------------------------------------------- | |
233 | |
234 void EvictionV3::PostDelayedTrim() { | |
235 // Prevent posting multiple tasks. | |
236 if (delay_trim_) | |
237 return; | |
238 delay_trim_ = true; | |
239 trim_delays_++; | |
240 base::MessageLoop::current()->PostDelayedTask( | |
241 FROM_HERE, | |
242 base::Bind(&EvictionV3::DelayedTrim, ptr_factory_.GetWeakPtr()), | |
243 base::TimeDelta::FromMilliseconds(1000)); | |
244 } | |
245 | |
246 void EvictionV3::DelayedTrim() { | |
247 delay_trim_ = false; | |
248 if (trim_delays_ < kMaxDelayedTrims && backend_->IsLoaded()) | |
249 return PostDelayedTrim(); | |
250 | |
251 TrimCache(false); | |
252 } | |
253 | |
254 bool EvictionV3::ShouldTrim() { | |
255 if (!FallingBehind(header_->num_bytes, max_size_) && | |
256 trim_delays_ < kMaxDelayedTrims && backend_->IsLoaded()) { | |
257 return false; | |
258 } | |
259 | |
260 UMA_HISTOGRAM_COUNTS("DiskCache.TrimDelays", trim_delays_); | |
261 trim_delays_ = 0; | |
262 return true; | |
263 } | |
264 | |
265 bool EvictionV3::ShouldTrimDeleted() { | |
266 int index_load = header_->num_entries * 100 / index_size_; | |
267 | |
268 // If the index is not loaded, the deleted list will tend to double the size | |
269 // of the other lists 3 lists (40% of the total). Otherwise, all lists will be | |
270 // about the same size. | |
271 int max_length = (index_load < 25) ? header_->num_entries * 2 / 5 : | |
272 header_->num_entries / 4; | |
273 return (!test_mode_ && header_->lru.sizes[Rankings::DELETED] > max_length); | |
274 } | |
275 | |
276 bool Eviction::EvictEntry(CacheRankingsBlock* node, bool empty, | |
277 Rankings::List list) { | |
278 EntryImplV3* entry = backend_->GetEnumeratedEntry(node, list); | |
279 if (!entry) { | |
280 Trace("NewEntry failed on Trim 0x%x", node->address().value()); | |
281 return false; | |
282 } | |
283 | |
284 ReportTrimTimes(entry); | |
285 if (empty || !new_eviction_) { | |
286 entry->DoomImpl(); | |
287 } else { | |
288 entry->DeleteEntryData(false); | |
289 EntryStore* info = entry->entry()->Data(); | |
290 DCHECK_EQ(ENTRY_NORMAL, info->state); | |
291 | |
292 rankings_->Remove(entry->rankings(), GetListForEntryV2(entry), true); | |
293 info->state = ENTRY_EVICTED; | |
294 entry->entry()->Store(); | |
295 rankings_->Insert(entry->rankings(), true, Rankings::DELETED); | |
296 } | |
297 if (!empty) | |
298 backend_->OnEvent(Stats::TRIM_ENTRY); | |
299 | |
300 entry->Release(); | |
301 | |
302 return true; | |
303 } | |
304 | |
305 void EvictionV3::TrimCacheV2(bool empty) { | |
306 Trace("*** Trim Cache ***"); | |
307 trimming_ = true; | |
308 TimeTicks start = TimeTicks::Now(); | |
309 | |
310 const int kListsToSearch = 3; | |
311 Rankings::ScopedRankingsBlock next[kListsToSearch]; | |
312 int list = Rankings::LAST_ELEMENT; | |
313 | |
314 // Get a node from each list. | |
315 for (int i = 0; i < kListsToSearch; i++) { | |
316 bool done = false; | |
317 next[i].set_rankings(rankings_); | |
318 if (done) | |
319 continue; | |
320 next[i].reset(rankings_->GetPrev(NULL, static_cast<Rankings::List>(i))); | |
321 if (!empty && NodeIsOldEnough(next[i].get(), i)) { | |
322 list = static_cast<Rankings::List>(i); | |
323 done = true; | |
324 } | |
325 } | |
326 | |
327 // If we are not meeting the time targets lets move on to list length. | |
328 if (!empty && Rankings::LAST_ELEMENT == list) | |
329 list = SelectListByLength(next); | |
330 | |
331 if (empty) | |
332 list = 0; | |
333 | |
334 Rankings::ScopedRankingsBlock node(rankings_); | |
335 int deleted_entries = 0; | |
336 int target_size = empty ? 0 : max_size_; | |
337 | |
338 for (; list < kListsToSearch; list++) { | |
339 while ((header_->num_bytes > target_size || test_mode_) && | |
340 next[list].get()) { | |
341 // The iterator could be invalidated within EvictEntry(). | |
342 if (!next[list]->HasData()) | |
343 break; | |
344 node.reset(next[list].release()); | |
345 next[list].reset(rankings_->GetPrev(node.get(), | |
346 static_cast<Rankings::List>(list))); | |
347 if (node->Data()->dirty != backend_->GetCurrentEntryId() || empty) { | |
348 // This entry is not being used by anybody. | |
349 // Do NOT use node as an iterator after this point. | |
350 rankings_->TrackRankingsBlock(node.get(), false); | |
351 if (EvictEntry(node.get(), empty, static_cast<Rankings::List>(list))) | |
352 deleted_entries++; | |
353 | |
354 if (!empty && test_mode_) | |
355 break; | |
356 } | |
357 if (!empty && (deleted_entries > 20 || | |
358 (TimeTicks::Now() - start).InMilliseconds() > 20)) { | |
359 base::MessageLoop::current()->PostTask( | |
360 FROM_HERE, | |
361 base::Bind(&Eviction::TrimCache, ptr_factory_.GetWeakPtr(), false)); | |
362 break; | |
363 } | |
364 } | |
365 if (!empty) | |
366 list = kListsToSearch; | |
367 } | |
368 | |
369 if (empty) { | |
370 TrimDeleted(true); | |
371 } else if (ShouldTrimDeleted()) { | |
372 base::MessageLoop::current()->PostTask( | |
373 FROM_HERE, | |
374 base::Bind(&EvictionV3::TrimDeleted, ptr_factory_.GetWeakPtr(), empty)); | |
375 } | |
376 | |
377 if (empty) { | |
378 CACHE_UMA(AGE_MS, "TotalClearTimeV2", 0, start); | |
379 } else { | |
380 CACHE_UMA(AGE_MS, "TotalTrimTimeV2", 0, start); | |
381 } | |
382 CACHE_UMA(COUNTS, "TrimItemsV2", 0, deleted_entries); | |
383 | |
384 Trace("*** Trim Cache end ***"); | |
385 trimming_ = false; | |
386 return; | |
387 } | |
388 | |
389 // This is a minimal implementation that just discards the oldest nodes. | |
390 // TODO(rvargas): Do something better here. | |
391 void EvictionV3::TrimDeleted(bool empty) { | |
392 Trace("*** Trim Deleted ***"); | |
393 if (backend_->disabled_) | |
394 return; | |
395 | |
396 TimeTicks start = TimeTicks::Now(); | |
397 Rankings::ScopedRankingsBlock node(rankings_); | |
398 Rankings::ScopedRankingsBlock next( | |
399 rankings_, rankings_->GetPrev(node.get(), Rankings::DELETED)); | |
400 int deleted_entries = 0; | |
401 while (next.get() && | |
402 (empty || (deleted_entries < 20 && | |
403 (TimeTicks::Now() - start).InMilliseconds() < 20))) { | |
404 node.reset(next.release()); | |
405 next.reset(rankings_->GetPrev(node.get(), Rankings::DELETED)); | |
406 if (RemoveDeletedNode(node.get())) | |
407 deleted_entries++; | |
408 if (test_mode_) | |
409 break; | |
410 } | |
411 | |
412 if (deleted_entries && !empty && ShouldTrimDeleted()) { | |
413 base::MessageLoop::current()->PostTask( | |
414 FROM_HERE, | |
415 base::Bind(&EvictionV3::TrimDeleted, ptr_factory_.GetWeakPtr(), false)); | |
416 } | |
417 | |
418 CACHE_UMA(AGE_MS, "TotalTrimDeletedTime", 0, start); | |
419 CACHE_UMA(COUNTS, "TrimDeletedItems", 0, deleted_entries); | |
420 Trace("*** Trim Deleted end ***"); | |
421 return; | |
422 } | |
423 | |
424 void EvictionV3::ReportTrimTimes(EntryImplV3* entry) { | |
425 if (first_trim_) { | |
426 first_trim_ = false; | |
427 if (backend_->ShouldReportAgain()) { | |
428 CACHE_UMA(AGE, "TrimAge", 0, entry->GetLastUsed()); | |
429 ReportListStats(); | |
430 } | |
431 | |
432 if (header_->lru.filled) | |
433 return; | |
434 | |
435 header_->lru.filled = 1; | |
436 | |
437 if (header_->create_time) { | |
438 // This is the first entry that we have to evict, generate some noise. | |
439 backend_->FirstEviction(); | |
440 } else { | |
441 // This is an old file, but we may want more reports from this user so | |
442 // lets save some create_time. | |
443 Time::Exploded old = {0}; | |
444 old.year = 2009; | |
445 old.month = 3; | |
446 old.day_of_month = 1; | |
447 header_->create_time = Time::FromLocalExploded(old).ToInternalValue(); | |
448 } | |
449 } | |
450 } | |
451 | |
452 bool EvictionV3::NodeIsOldEnough(CacheRankingsBlock* node, int list) { | |
453 if (!node) | |
454 return false; | |
455 | |
456 // If possible, we want to keep entries on each list at least kTargetTime | |
457 // hours. Each successive list on the enumeration has 2x the target time of | |
458 // the previous list. | |
459 Time used = Time::FromInternalValue(node->Data()->last_used); | |
460 int multiplier = 1 << list; | |
461 return (Time::Now() - used).InHours() > kTargetTime * multiplier; | |
462 } | |
463 | |
464 int EvictionV3::SelectListByLength(Rankings::ScopedRankingsBlock* next) { | |
465 int data_entries = header_->num_entries - | |
466 header_->lru.sizes[Rankings::DELETED]; | |
467 // Start by having each list to be roughly the same size. | |
468 if (header_->lru.sizes[0] > data_entries / 3) | |
469 return 0; | |
470 | |
471 int list = (header_->lru.sizes[1] > data_entries / 3) ? 1 : 2; | |
472 | |
473 // Make sure that frequently used items are kept for a minimum time; we know | |
474 // that this entry is not older than its current target, but it must be at | |
475 // least older than the target for list 0 (kTargetTime), as long as we don't | |
476 // exhaust list 0. | |
477 if (!NodeIsOldEnough(next[list].get(), 0) && | |
478 header_->lru.sizes[0] > data_entries / 10) | |
479 list = 0; | |
480 | |
481 return list; | |
482 } | |
483 | |
484 void EvictionV3::ReportListStats() { | |
485 if (!new_eviction_) | |
486 return; | |
487 | |
488 Rankings::ScopedRankingsBlock last1(rankings_, | |
489 rankings_->GetPrev(NULL, Rankings::NO_USE)); | |
490 Rankings::ScopedRankingsBlock last2(rankings_, | |
491 rankings_->GetPrev(NULL, Rankings::LOW_USE)); | |
492 Rankings::ScopedRankingsBlock last3(rankings_, | |
493 rankings_->GetPrev(NULL, Rankings::HIGH_USE)); | |
494 Rankings::ScopedRankingsBlock last4(rankings_, | |
495 rankings_->GetPrev(NULL, Rankings::DELETED)); | |
496 | |
497 if (last1.get()) | |
498 CACHE_UMA(AGE, "NoUseAge", 0, | |
499 Time::FromInternalValue(last1.get()->Data()->last_used)); | |
500 if (last2.get()) | |
501 CACHE_UMA(AGE, "LowUseAge", 0, | |
502 Time::FromInternalValue(last2.get()->Data()->last_used)); | |
503 if (last3.get()) | |
504 CACHE_UMA(AGE, "HighUseAge", 0, | |
505 Time::FromInternalValue(last3.get()->Data()->last_used)); | |
506 if (last4.get()) | |
507 CACHE_UMA(AGE, "DeletedAge", 0, | |
508 Time::FromInternalValue(last4.get()->Data()->last_used)); | |
509 } | |
510 #endif // defined(V3_NOT_JUST_YET_READY). | |
511 | |
512 } // namespace disk_cache | |
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