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
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
|
//===-- sanitizer_allocator_size_class_map.h --------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Part of the Sanitizer Allocator.
//
//===----------------------------------------------------------------------===//
#ifndef SANITIZER_ALLOCATOR_H
#error This file must be included inside sanitizer_allocator.h
#endif
// SizeClassMap maps allocation sizes into size classes and back.
// Class 0 always corresponds to size 0.
// The other sizes are controlled by the template parameters:
// kMinSizeLog: defines the class 1 as 2^kMinSizeLog.
// kMaxSizeLog: defines the last class as 2^kMaxSizeLog.
// kMidSizeLog: the classes starting from 1 increase with step
// 2^kMinSizeLog until 2^kMidSizeLog.
// kNumBits: the number of non-zero bits in sizes after 2^kMidSizeLog.
// E.g. with kNumBits==3 all size classes after 2^kMidSizeLog
// look like 0b1xx0..0, where x is either 0 or 1.
//
// Example: kNumBits=3, kMidSizeLog=4, kMidSizeLog=8, kMaxSizeLog=17:
//
// Classes 1 - 16 correspond to sizes 16 to 256 (size = class_id * 16).
// Next 4 classes: 256 + i * 64 (i = 1 to 4).
// Next 4 classes: 512 + i * 128 (i = 1 to 4).
// ...
// Next 4 classes: 2^k + i * 2^(k-2) (i = 1 to 4).
// Last class corresponds to kMaxSize = 1 << kMaxSizeLog.
//
// This structure of the size class map gives us:
// - Efficient table-free class-to-size and size-to-class functions.
// - Difference between two consequent size classes is between 14% and 25%
//
// This class also gives a hint to a thread-caching allocator about the amount
// of chunks that need to be cached per-thread:
// - kMaxNumCachedHint is a hint for maximal number of chunks per size class.
// The actual number is computed in TransferBatch.
// - (1 << kMaxBytesCachedLog) is the maximal number of bytes per size class.
//
// Part of output of SizeClassMap::Print():
// c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0
// c01 => s: 16 diff: +16 00% l 4 cached: 256 4096; id 1
// c02 => s: 32 diff: +16 100% l 5 cached: 256 8192; id 2
// c03 => s: 48 diff: +16 50% l 5 cached: 256 12288; id 3
// c04 => s: 64 diff: +16 33% l 6 cached: 256 16384; id 4
// c05 => s: 80 diff: +16 25% l 6 cached: 256 20480; id 5
// c06 => s: 96 diff: +16 20% l 6 cached: 256 24576; id 6
// c07 => s: 112 diff: +16 16% l 6 cached: 256 28672; id 7
//
// c08 => s: 128 diff: +16 14% l 7 cached: 256 32768; id 8
// c09 => s: 144 diff: +16 12% l 7 cached: 256 36864; id 9
// c10 => s: 160 diff: +16 11% l 7 cached: 256 40960; id 10
// c11 => s: 176 diff: +16 10% l 7 cached: 256 45056; id 11
// c12 => s: 192 diff: +16 09% l 7 cached: 256 49152; id 12
// c13 => s: 208 diff: +16 08% l 7 cached: 256 53248; id 13
// c14 => s: 224 diff: +16 07% l 7 cached: 256 57344; id 14
// c15 => s: 240 diff: +16 07% l 7 cached: 256 61440; id 15
//
// c16 => s: 256 diff: +16 06% l 8 cached: 256 65536; id 16
// c17 => s: 320 diff: +64 25% l 8 cached: 204 65280; id 17
// c18 => s: 384 diff: +64 20% l 8 cached: 170 65280; id 18
// c19 => s: 448 diff: +64 16% l 8 cached: 146 65408; id 19
//
// c20 => s: 512 diff: +64 14% l 9 cached: 128 65536; id 20
// c21 => s: 640 diff: +128 25% l 9 cached: 102 65280; id 21
// c22 => s: 768 diff: +128 20% l 9 cached: 85 65280; id 22
// c23 => s: 896 diff: +128 16% l 9 cached: 73 65408; id 23
//
// c24 => s: 1024 diff: +128 14% l 10 cached: 64 65536; id 24
// c25 => s: 1280 diff: +256 25% l 10 cached: 51 65280; id 25
// c26 => s: 1536 diff: +256 20% l 10 cached: 42 64512; id 26
// c27 => s: 1792 diff: +256 16% l 10 cached: 36 64512; id 27
//
// ...
//
// c48 => s: 65536 diff: +8192 14% l 16 cached: 1 65536; id 48
// c49 => s: 81920 diff: +16384 25% l 16 cached: 1 81920; id 49
// c50 => s: 98304 diff: +16384 20% l 16 cached: 1 98304; id 50
// c51 => s: 114688 diff: +16384 16% l 16 cached: 1 114688; id 51
//
// c52 => s: 131072 diff: +16384 14% l 17 cached: 1 131072; id 52
//
//
// Another example (kNumBits=2):
// c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0
// c01 => s: 32 diff: +32 00% l 5 cached: 64 2048; id 1
// c02 => s: 64 diff: +32 100% l 6 cached: 64 4096; id 2
// c03 => s: 96 diff: +32 50% l 6 cached: 64 6144; id 3
// c04 => s: 128 diff: +32 33% l 7 cached: 64 8192; id 4
// c05 => s: 160 diff: +32 25% l 7 cached: 64 10240; id 5
// c06 => s: 192 diff: +32 20% l 7 cached: 64 12288; id 6
// c07 => s: 224 diff: +32 16% l 7 cached: 64 14336; id 7
// c08 => s: 256 diff: +32 14% l 8 cached: 64 16384; id 8
// c09 => s: 384 diff: +128 50% l 8 cached: 42 16128; id 9
// c10 => s: 512 diff: +128 33% l 9 cached: 32 16384; id 10
// c11 => s: 768 diff: +256 50% l 9 cached: 21 16128; id 11
// c12 => s: 1024 diff: +256 33% l 10 cached: 16 16384; id 12
// c13 => s: 1536 diff: +512 50% l 10 cached: 10 15360; id 13
// c14 => s: 2048 diff: +512 33% l 11 cached: 8 16384; id 14
// c15 => s: 3072 diff: +1024 50% l 11 cached: 5 15360; id 15
// c16 => s: 4096 diff: +1024 33% l 12 cached: 4 16384; id 16
// c17 => s: 6144 diff: +2048 50% l 12 cached: 2 12288; id 17
// c18 => s: 8192 diff: +2048 33% l 13 cached: 2 16384; id 18
// c19 => s: 12288 diff: +4096 50% l 13 cached: 1 12288; id 19
// c20 => s: 16384 diff: +4096 33% l 14 cached: 1 16384; id 20
// c21 => s: 24576 diff: +8192 50% l 14 cached: 1 24576; id 21
// c22 => s: 32768 diff: +8192 33% l 15 cached: 1 32768; id 22
// c23 => s: 49152 diff: +16384 50% l 15 cached: 1 49152; id 23
// c24 => s: 65536 diff: +16384 33% l 16 cached: 1 65536; id 24
// c25 => s: 98304 diff: +32768 50% l 16 cached: 1 98304; id 25
// c26 => s: 131072 diff: +32768 33% l 17 cached: 1 131072; id 26
template <uptr kNumBits, uptr kMinSizeLog, uptr kMidSizeLog, uptr kMaxSizeLog,
uptr kMaxNumCachedHintT, uptr kMaxBytesCachedLog>
class SizeClassMap {
static const uptr kMinSize = 1 << kMinSizeLog;
static const uptr kMidSize = 1 << kMidSizeLog;
static const uptr kMidClass = kMidSize / kMinSize;
static const uptr S = kNumBits - 1;
static const uptr M = (1 << S) - 1;
public:
// kMaxNumCachedHintT is a power of two. It serves as a hint
// for the size of TransferBatch, the actual size could be a bit smaller.
static const uptr kMaxNumCachedHint = kMaxNumCachedHintT;
COMPILER_CHECK((kMaxNumCachedHint & (kMaxNumCachedHint - 1)) == 0);
static const uptr kMaxSize = 1UL << kMaxSizeLog;
static const uptr kNumClasses =
kMidClass + ((kMaxSizeLog - kMidSizeLog) << S) + 1 + 1;
static const uptr kLargestClassID = kNumClasses - 2;
static const uptr kBatchClassID = kNumClasses - 1;
COMPILER_CHECK(kNumClasses >= 16 && kNumClasses <= 256);
static const uptr kNumClassesRounded =
kNumClasses <= 32 ? 32 :
kNumClasses <= 64 ? 64 :
kNumClasses <= 128 ? 128 : 256;
static uptr Size(uptr class_id) {
// Estimate the result for kBatchClassID because this class does not know
// the exact size of TransferBatch. It's OK since we are using the actual
// sizeof(TransferBatch) where it matters.
if (UNLIKELY(class_id == kBatchClassID))
return kMaxNumCachedHint * sizeof(uptr);
if (class_id <= kMidClass)
return kMinSize * class_id;
class_id -= kMidClass;
uptr t = kMidSize << (class_id >> S);
return t + (t >> S) * (class_id & M);
}
static uptr ClassID(uptr size) {
if (UNLIKELY(size > kMaxSize))
return 0;
if (size <= kMidSize)
return (size + kMinSize - 1) >> kMinSizeLog;
uptr l = MostSignificantSetBitIndex(size);
uptr hbits = (size >> (l - S)) & M;
uptr lbits = size & ((1 << (l - S)) - 1);
uptr l1 = l - kMidSizeLog;
return kMidClass + (l1 << S) + hbits + (lbits > 0);
}
static uptr MaxCachedHint(uptr class_id) {
// Estimate the result for kBatchClassID because this class does not know
// the exact size of TransferBatch. We need to cache fewer batches than user
// chunks, so this number can be small.
if (UNLIKELY(class_id == kBatchClassID))
return 16;
if (UNLIKELY(class_id == 0))
return 0;
uptr n = (1UL << kMaxBytesCachedLog) / Size(class_id);
return Max<uptr>(1, Min(kMaxNumCachedHint, n));
}
static void Print() {
uptr prev_s = 0;
uptr total_cached = 0;
for (uptr i = 0; i < kNumClasses; i++) {
uptr s = Size(i);
if (s >= kMidSize / 2 && (s & (s - 1)) == 0)
Printf("\n");
uptr d = s - prev_s;
uptr p = prev_s ? (d * 100 / prev_s) : 0;
uptr l = s ? MostSignificantSetBitIndex(s) : 0;
uptr cached = MaxCachedHint(i) * s;
if (i == kBatchClassID)
d = p = l = 0;
Printf("c%02zd => s: %zd diff: +%zd %02zd%% l %zd "
"cached: %zd %zd; id %zd\n",
i, Size(i), d, p, l, MaxCachedHint(i), cached, ClassID(s));
total_cached += cached;
prev_s = s;
}
Printf("Total cached: %zd\n", total_cached);
}
static void Validate() {
for (uptr c = 1; c < kNumClasses; c++) {
// Printf("Validate: c%zd\n", c);
uptr s = Size(c);
CHECK_NE(s, 0U);
if (c == kBatchClassID)
continue;
CHECK_EQ(ClassID(s), c);
if (c < kLargestClassID)
CHECK_EQ(ClassID(s + 1), c + 1);
CHECK_EQ(ClassID(s - 1), c);
CHECK_GT(Size(c), Size(c - 1));
}
CHECK_EQ(ClassID(kMaxSize + 1), 0);
for (uptr s = 1; s <= kMaxSize; s++) {
uptr c = ClassID(s);
// Printf("s%zd => c%zd\n", s, c);
CHECK_LT(c, kNumClasses);
CHECK_GE(Size(c), s);
if (c > 0)
CHECK_LT(Size(c - 1), s);
}
}
};
typedef SizeClassMap<3, 4, 8, 17, 128, 16> DefaultSizeClassMap;
typedef SizeClassMap<3, 4, 8, 17, 64, 14> CompactSizeClassMap;
typedef SizeClassMap<2, 5, 9, 16, 64, 14> VeryCompactSizeClassMap;
|
