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1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef ART_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_
18 #define ART_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_
19 
20 #include <algorithm>
21 #include <cstdint>
22 #include <iosfwd>
23 
24 #include <android-base/logging.h>
25 
26 namespace art {
27 
28 class DexFile;
29 
30 enum class LayoutType : uint8_t {
31   // Layout of things that are hot (commonly accessed), these should be pinned or madvised will
32   // need.
33   kLayoutTypeHot,
34   // Layout of things that are randomly used. These should be advised to random access.
35   // Without layout, this is the default mode when loading a dex file.
36   kLayoutTypeSometimesUsed,
37   // Layout of things that are only used during startup, these can be madvised after launch.
38   kLayoutTypeStartupOnly,
39   // Layout of things that are needed probably only once (class initializers). These can be
40   // madvised during trim events.
41   kLayoutTypeUsedOnce,
42   // Layout of things that are thought to be unused. These things should be advised to random
43   // access.
44   kLayoutTypeUnused,
45   // Unused value, just the number of elements in the enum.
46   kLayoutTypeCount,
47 };
48 std::ostream& operator<<(std::ostream& os, const LayoutType& collector_type);
49 
50 // Return the "best" layout option if the same item has multiple different layouts.
MergeLayoutType(LayoutType a,LayoutType b)51 static inline LayoutType MergeLayoutType(LayoutType a, LayoutType b) {
52   return std::min(a, b);
53 }
54 
55 enum class MadviseState : uint8_t {
56   // Madvise based on a file that was just loaded.
57   kMadviseStateAtLoad,
58   // Madvise based after launch is finished.
59   kMadviseStateFinishedLaunch,
60   // Trim by madvising code that is unlikely to be too important in the future.
61   kMadviseStateFinishedTrim,
62 };
63 std::ostream& operator<<(std::ostream& os, const MadviseState& collector_type);
64 
65 // A dex layout section such as code items or strings. Each section is composed of subsections
66 // that are laid out adjacently to each other such as (hot, unused, startup, etc...).
67 class DexLayoutSection {
68  public:
69   // A subsection is a a continuous range of dex file that is all part of the same layout hint.
70   class Subsection {
71    public:
72     // Use uint32_t to handle 32/64 bit cross compilation.
73     uint32_t start_offset_ = 0u;
74     uint32_t end_offset_ = 0u;
75 
Contains(uint32_t offset)76     bool Contains(uint32_t offset) const {
77       return start_offset_ <= offset && offset < end_offset_;
78     }
79 
Size()80     bool Size() const {
81       DCHECK_LE(start_offset_, end_offset_);
82       return end_offset_ - start_offset_;
83     }
84 
CombineSection(uint32_t start_offset,uint32_t end_offset)85     void CombineSection(uint32_t start_offset, uint32_t end_offset) {
86       DCHECK_LE(start_offset, end_offset);
87       if (start_offset_ == end_offset_) {
88         start_offset_ = start_offset;
89         end_offset_ = end_offset;
90       } else  {
91         start_offset_ = std::min(start_offset_, start_offset);
92         end_offset_ = std::max(end_offset_, end_offset);
93       }
94     }
95 
96     void Madvise(const DexFile* dex_file, int advice) const;
97   };
98 
99   // Madvise the largest page-aligned region contained in [begin, end).
100   static int MadviseLargestPageAlignedRegion(const uint8_t* begin, const uint8_t* end, int advice);
101 
102   Subsection parts_[static_cast<size_t>(LayoutType::kLayoutTypeCount)];
103 };
104 
105 // A set of dex layout sections, currently there is only one section for code and one for strings.
106 class DexLayoutSections {
107  public:
108   enum class SectionType : uint8_t {
109     kSectionTypeCode,
110     kSectionTypeStrings,
111     kSectionCount,
112   };
113 
114   // Advise access about the dex file based on layout. The caller is expected to have already
115   // madvised to MADV_RANDOM.
116   void Madvise(const DexFile* dex_file, MadviseState state) const;
117 
118   DexLayoutSection sections_[static_cast<size_t>(SectionType::kSectionCount)];
119 };
120 
121 std::ostream& operator<<(std::ostream& os, const DexLayoutSections::SectionType& collector_type);
122 std::ostream& operator<<(std::ostream& os, const DexLayoutSection& section);
123 std::ostream& operator<<(std::ostream& os, const DexLayoutSections& sections);
124 
125 }  // namespace art
126 
127 #endif  // ART_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_
128