1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
// Copyright 2021 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/strings/cord_analysis.h"
#include <cstddef>
#include <cstdint>
#include <unordered_set>
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/container/inlined_vector.h"
#include "absl/strings/internal/cord_data_edge.h"
#include "absl/strings/internal/cord_internal.h"
#include "absl/strings/internal/cord_rep_btree.h"
#include "absl/strings/internal/cord_rep_crc.h"
#include "absl/strings/internal/cord_rep_flat.h"
#include "absl/strings/internal/cord_rep_ring.h"
//
#include "absl/base/macros.h"
#include "absl/base/port.h"
#include "absl/functional/function_ref.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace cord_internal {
namespace {
// Accounting mode for analyzing memory usage.
enum class Mode { kFairShare, kTotal, kTotalMorePrecise };
// CordRepRef holds a `const CordRep*` reference in rep, and depending on mode,
// holds a 'fraction' representing a cumulative inverse refcount weight.
template <Mode mode>
struct CordRepRef {
// Instantiates a CordRepRef instance.
explicit CordRepRef(const CordRep* r) : rep(r) {}
// Creates a child reference holding the provided child.
// Overloaded to add cumulative reference count for kFairShare.
CordRepRef Child(const CordRep* child) const { return CordRepRef(child); }
const CordRep* rep;
};
// RawUsage holds the computed total number of bytes.
template <Mode mode>
struct RawUsage {
size_t total = 0;
// Add 'size' to total, ignoring the CordRepRef argument.
void Add(size_t size, CordRepRef<mode>) { total += size; }
};
// Overloaded representation of RawUsage that tracks the set of objects
// counted, and avoids double-counting objects referenced more than once
// by the same Cord.
template <>
struct RawUsage<Mode::kTotalMorePrecise> {
size_t total = 0;
// TODO(b/289250880): Replace this with a flat_hash_set.
std::unordered_set<const CordRep*> counted;
void Add(size_t size, CordRepRef<Mode::kTotalMorePrecise> repref) {
if (counted.find(repref.rep) == counted.end()) {
counted.insert(repref.rep);
total += size;
}
}
};
// Returns n / refcount avoiding a div for the common refcount == 1.
template <typename refcount_t>
double MaybeDiv(double d, refcount_t refcount) {
return refcount == 1 ? d : d / refcount;
}
// Overloaded 'kFairShare' specialization for CordRepRef. This class holds a
// `fraction` value which represents a cumulative inverse refcount weight.
// For example, a top node with a reference count of 2 will have a fraction
// value of 1/2 = 0.5, representing the 'fair share' of memory it references.
// A node below such a node with a reference count of 5 then has a fraction of
// 0.5 / 5 = 0.1 representing the fair share of memory below that node, etc.
template <>
struct CordRepRef<Mode::kFairShare> {
// Creates a CordRepRef with the provided rep and top (parent) fraction.
explicit CordRepRef(const CordRep* r, double frac = 1.0)
: rep(r), fraction(MaybeDiv(frac, r->refcount.Get())) {}
// Returns a CordRepRef with a fraction of `this->fraction / child.refcount`
CordRepRef Child(const CordRep* child) const {
return CordRepRef(child, fraction);
}
const CordRep* rep;
double fraction;
};
// Overloaded 'kFairShare' specialization for RawUsage
template <>
struct RawUsage<Mode::kFairShare> {
double total = 0;
// Adds `size` multiplied by `rep.fraction` to the total size.
void Add(size_t size, CordRepRef<Mode::kFairShare> rep) {
total += static_cast<double>(size) * rep.fraction;
}
};
// Computes the estimated memory size of the provided data edge.
// External reps are assumed 'heap allocated at their exact size'.
template <Mode mode>
void AnalyzeDataEdge(CordRepRef<mode> rep, RawUsage<mode>& raw_usage) {
assert(IsDataEdge(rep.rep));
// Consume all substrings
if (rep.rep->tag == SUBSTRING) {
raw_usage.Add(sizeof(CordRepSubstring), rep);
rep = rep.Child(rep.rep->substring()->child);
}
// Consume FLAT / EXTERNAL
const size_t size =
rep.rep->tag >= FLAT
? rep.rep->flat()->AllocatedSize()
: rep.rep->length + sizeof(CordRepExternalImpl<intptr_t>);
raw_usage.Add(size, rep);
}
// Computes the memory size of the provided Ring tree.
template <Mode mode>
void AnalyzeRing(CordRepRef<mode> rep, RawUsage<mode>& raw_usage) {
const CordRepRing* ring = rep.rep->ring();
raw_usage.Add(CordRepRing::AllocSize(ring->capacity()), rep);
ring->ForEach([&](CordRepRing::index_type pos) {
AnalyzeDataEdge(rep.Child(ring->entry_child(pos)), raw_usage);
});
}
// Computes the memory size of the provided Btree tree.
template <Mode mode>
void AnalyzeBtree(CordRepRef<mode> rep, RawUsage<mode>& raw_usage) {
raw_usage.Add(sizeof(CordRepBtree), rep);
const CordRepBtree* tree = rep.rep->btree();
if (tree->height() > 0) {
for (CordRep* edge : tree->Edges()) {
AnalyzeBtree(rep.Child(edge), raw_usage);
}
} else {
for (CordRep* edge : tree->Edges()) {
AnalyzeDataEdge(rep.Child(edge), raw_usage);
}
}
}
template <Mode mode>
size_t GetEstimatedUsage(const CordRep* rep) {
// Zero initialized memory usage totals.
RawUsage<mode> raw_usage;
// Capture top level node and refcount into a CordRepRef.
CordRepRef<mode> repref(rep);
// Consume the top level CRC node if present.
if (repref.rep->tag == CRC) {
raw_usage.Add(sizeof(CordRepCrc), repref);
repref = repref.Child(repref.rep->crc()->child);
}
if (IsDataEdge(repref.rep)) {
AnalyzeDataEdge(repref, raw_usage);
} else if (repref.rep->tag == BTREE) {
AnalyzeBtree(repref, raw_usage);
} else if (repref.rep->tag == RING) {
AnalyzeRing(repref, raw_usage);
} else {
assert(false);
}
return static_cast<size_t>(raw_usage.total);
}
} // namespace
size_t GetEstimatedMemoryUsage(const CordRep* rep) {
return GetEstimatedUsage<Mode::kTotal>(rep);
}
size_t GetEstimatedFairShareMemoryUsage(const CordRep* rep) {
return GetEstimatedUsage<Mode::kFairShare>(rep);
}
size_t GetMorePreciseMemoryUsage(const CordRep* rep) {
return GetEstimatedUsage<Mode::kTotalMorePrecise>(rep);
}
} // namespace cord_internal
ABSL_NAMESPACE_END
} // namespace absl
|
