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Side by Side Diff: base/trace_event/heap_profiler_allocation_context.h

Issue 1907593002: Revert of [tracing] Turn StackFrame into struct. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Created 4 years, 8 months ago
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1 // Copyright 2015 The Chromium Authors. All rights reserved. 1 // Copyright 2015 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 #ifndef BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_ 5 #ifndef BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_
6 #define BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_ 6 #define BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_
7 7
8 #include <stddef.h> 8 #include <stddef.h>
9 #include <stdint.h> 9 #include <stdint.h>
10 10
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28 // The number of stack frames stored in the backtrace is a trade off between 28 // The number of stack frames stored in the backtrace is a trade off between
29 // memory used for tracing and accuracy. Measurements done on a prototype 29 // memory used for tracing and accuracy. Measurements done on a prototype
30 // revealed that: 30 // revealed that:
31 // 31 //
32 // - In 60 percent of the cases, stack depth <= 7. 32 // - In 60 percent of the cases, stack depth <= 7.
33 // - In 87 percent of the cases, stack depth <= 9. 33 // - In 87 percent of the cases, stack depth <= 9.
34 // - In 95 percent of the cases, stack depth <= 11. 34 // - In 95 percent of the cases, stack depth <= 11.
35 // 35 //
36 // See the design doc (https://goo.gl/4s7v7b) for more details. 36 // See the design doc (https://goo.gl/4s7v7b) for more details.
37 37
38 // Represents (pseudo) stack frame. Used in Backtrace class below. 38 using StackFrame = const char*;
39 //
40 // Conceptually stack frame is identified by its value, and type is used
41 // mostly to properly format the value. Value is expected to be a valid
42 // pointer from process' address space.
43 struct BASE_EXPORT StackFrame {
44 enum class Type {
45 TRACE_EVENT_NAME, // const char* string
46 THREAD_NAME, // const char* thread name
47 };
48 39
49 static StackFrame FromTraceEventName(const char* name) { 40 struct BASE_EXPORT Backtrace {
50 return {Type::TRACE_EVENT_NAME, name}; 41 // Unused backtrace frames are filled with nullptr frames. If the stack is
51 } 42 // higher than what can be stored here, the bottom frames are stored. Based
52 static StackFrame FromThreadName(const char* name) { 43 // on the data above, a depth of 12 captures the full stack in the vast
53 return {Type::THREAD_NAME, name}; 44 // majority of the cases.
54 } 45 StackFrame frames[12];
55
56 Type type;
57 const void* value;
58 }; 46 };
59 47
60 bool BASE_EXPORT operator < (const StackFrame& lhs, const StackFrame& rhs); 48 // Struct to store the size and count of the allocations.
61 bool BASE_EXPORT operator == (const StackFrame& lhs, const StackFrame& rhs); 49 struct AllocationMetrics {
62 bool BASE_EXPORT operator != (const StackFrame& lhs, const StackFrame& rhs); 50 size_t size;
63 51 size_t count;
64 struct BASE_EXPORT Backtrace {
65 Backtrace();
66
67 // If the stack is higher than what can be stored here, the bottom frames
68 // (the ones closer to main()) are stored. Based on the data above, a depth
69 // of 12 captures the full stack in the vast majority of the cases.
70 enum { kMaxFrameCount = 12 };
71 StackFrame frames[kMaxFrameCount];
72 size_t frame_count;
73 }; 52 };
74 53
75 bool BASE_EXPORT operator==(const Backtrace& lhs, const Backtrace& rhs); 54 bool BASE_EXPORT operator==(const Backtrace& lhs, const Backtrace& rhs);
76 55
77 // The |AllocationContext| is context metadata that is kept for every allocation 56 // The |AllocationContext| is context metadata that is kept for every allocation
78 // when heap profiling is enabled. To simplify memory management for book- 57 // when heap profiling is enabled. To simplify memory management for book-
79 // keeping, this struct has a fixed size. 58 // keeping, this struct has a fixed size. All |const char*|s here must have
59 // static lifetime.
80 struct BASE_EXPORT AllocationContext { 60 struct BASE_EXPORT AllocationContext {
81 AllocationContext(); 61 public:
62 // An allocation context with empty backtrace and unknown type.
63 static AllocationContext Empty();
82 64
83 Backtrace backtrace; 65 Backtrace backtrace;
84 66
85 // Type name of the type stored in the allocated memory. A null pointer 67 // Type name of the type stored in the allocated memory. A null pointer
86 // indicates "unknown type". Grouping is done by comparing pointers, not by 68 // indicates "unknown type". Grouping is done by comparing pointers, not by
87 // deep string comparison. In a component build, where a type name can have a 69 // deep string comparison. In a component build, where a type name can have a
88 // string literal in several dynamic libraries, this may distort grouping. 70 // string literal in several dynamic libraries, this may distort grouping.
89 const char* type_name; 71 const char* type_name;
72
73 private:
74 friend class AllocationContextTracker;
75
76 // Don't allow uninitialized instances except inside the allocation context
77 // tracker. Except in tests, an |AllocationContext| should only be obtained
78 // from the tracker. In tests, paying the overhead of initializing the struct
79 // to |Empty| and then overwriting the members is not such a big deal.
80 AllocationContext();
90 }; 81 };
91 82
92 bool BASE_EXPORT operator==(const AllocationContext& lhs, 83 bool BASE_EXPORT operator==(const AllocationContext& lhs,
93 const AllocationContext& rhs); 84 const AllocationContext& rhs);
94 85
95 // Struct to store the size and count of the allocations.
96 struct AllocationMetrics {
97 size_t size;
98 size_t count;
99 };
100
101 } // namespace trace_event 86 } // namespace trace_event
102 } // namespace base 87 } // namespace base
103 88
104 namespace BASE_HASH_NAMESPACE { 89 namespace BASE_HASH_NAMESPACE {
105 90
106 template <> 91 template <>
107 struct BASE_EXPORT hash<base::trace_event::StackFrame> {
108 size_t operator()(const base::trace_event::StackFrame& frame) const;
109 };
110
111 template <>
112 struct BASE_EXPORT hash<base::trace_event::Backtrace> { 92 struct BASE_EXPORT hash<base::trace_event::Backtrace> {
113 size_t operator()(const base::trace_event::Backtrace& backtrace) const; 93 size_t operator()(const base::trace_event::Backtrace& backtrace) const;
114 }; 94 };
115 95
116 template <> 96 template <>
117 struct BASE_EXPORT hash<base::trace_event::AllocationContext> { 97 struct BASE_EXPORT hash<base::trace_event::AllocationContext> {
118 size_t operator()(const base::trace_event::AllocationContext& context) const; 98 size_t operator()(const base::trace_event::AllocationContext& context) const;
119 }; 99 };
120 100
121 } // BASE_HASH_NAMESPACE 101 } // BASE_HASH_NAMESPACE
122 102
123 #endif // BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_ 103 #endif // BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_
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