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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 | 4 |
| 5 // The eviction policy is a very simple pure LRU, so the elements at the end of | 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 | 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 | 7 // only one list in use (Rankings::NO_USE), and elements are sent to the front |
| 8 // of the list whenever they are accessed. | 8 // of the list whenever they are accessed. |
| 9 | 9 |
| 10 // The new (in-development) eviction policy adds re-use as a factor to evict | 10 // The new (in-development) eviction policy adds re-use as a factor to evict |
| 11 // an entry. The story so far: | 11 // an entry. The story so far: |
| 12 | 12 |
| 13 // Entries are linked on separate lists depending on how often they are used. | 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 | 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 | 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. | 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 | 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 | 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. | 19 // and maybe in the future we don't evict that element. |
| 20 | 20 |
| 21 // When we have to evict an element, first we try to use the last element from | 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 | 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 | 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), | 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 | 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 | 26 // size so that we have a chance to see an element again and move it to another |
| 27 // list. | 27 // list. |
| 28 | 28 |
| 29 #include "net/disk_cache/eviction.h" | 29 #include "net/disk_cache/blockfile/eviction.h" |
| 30 | 30 |
| 31 #include "base/bind.h" | 31 #include "base/bind.h" |
| 32 #include "base/compiler_specific.h" | 32 #include "base/compiler_specific.h" |
| 33 #include "base/logging.h" | 33 #include "base/logging.h" |
| 34 #include "base/message_loop/message_loop.h" | 34 #include "base/message_loop/message_loop.h" |
| 35 #include "base/strings/string_util.h" | 35 #include "base/strings/string_util.h" |
| 36 #include "base/time/time.h" | 36 #include "base/time/time.h" |
| 37 #include "net/disk_cache/backend_impl.h" | 37 #include "net/disk_cache/blockfile/backend_impl.h" |
| 38 #include "net/disk_cache/disk_format.h" | 38 #include "net/disk_cache/blockfile/disk_format.h" |
| 39 #include "net/disk_cache/entry_impl.h" | 39 #include "net/disk_cache/blockfile/entry_impl.h" |
| 40 #include "net/disk_cache/experiments.h" | 40 #include "net/disk_cache/blockfile/experiments.h" |
| 41 #include "net/disk_cache/trace.h" | 41 #include "net/disk_cache/blockfile/trace.h" |
| 42 | 42 |
| 43 #define CACHE_HISTOGRAM_MACROS_BACKEND_IMPL_OBJ backend_ | 43 #define CACHE_HISTOGRAM_MACROS_BACKEND_IMPL_OBJ backend_ |
| 44 #include "net/disk_cache/histogram_macros.h" | 44 #include "net/disk_cache/blockfile/histogram_macros.h" |
| 45 | 45 |
| 46 using base::Time; | 46 using base::Time; |
| 47 using base::TimeTicks; | 47 using base::TimeTicks; |
| 48 | 48 |
| 49 namespace { | 49 namespace { |
| 50 | 50 |
| 51 const int kCleanUpMargin = 1024 * 1024; | 51 const int kCleanUpMargin = 1024 * 1024; |
| 52 const int kHighUse = 10; // Reuse count to be on the HIGH_USE list. | 52 const int kHighUse = 10; // Reuse count to be on the HIGH_USE list. |
| 53 const int kTargetTime = 24 * 7; // Time to be evicted (hours since last use). | 53 const int kTargetTime = 24 * 7; // Time to be evicted (hours since last use). |
| 54 const int kMaxDelayedTrims = 60; | 54 const int kMaxDelayedTrims = 60; |
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| 590 Time::FromInternalValue(last2.get()->Data()->last_used)); | 590 Time::FromInternalValue(last2.get()->Data()->last_used)); |
| 591 if (last3.get()) | 591 if (last3.get()) |
| 592 CACHE_UMA(AGE, "HighUseAge", 0, | 592 CACHE_UMA(AGE, "HighUseAge", 0, |
| 593 Time::FromInternalValue(last3.get()->Data()->last_used)); | 593 Time::FromInternalValue(last3.get()->Data()->last_used)); |
| 594 if (last4.get()) | 594 if (last4.get()) |
| 595 CACHE_UMA(AGE, "DeletedAge", 0, | 595 CACHE_UMA(AGE, "DeletedAge", 0, |
| 596 Time::FromInternalValue(last4.get()->Data()->last_used)); | 596 Time::FromInternalValue(last4.get()->Data()->last_used)); |
| 597 } | 597 } |
| 598 | 598 |
| 599 } // namespace disk_cache | 599 } // namespace disk_cache |
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