1 //===-- sanitizer_allocator_size_class_map.h --------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Part of the Sanitizer Allocator.
12 //===----------------------------------------------------------------------===//
13 #ifndef SANITIZER_ALLOCATOR_H
14 #error This file must be included inside sanitizer_allocator.h
17 // SizeClassMap maps allocation sizes into size classes and back.
18 // Class 0 always corresponds to size 0.
19 // The other sizes are controlled by the template parameters:
20 // kMinSizeLog: defines the class 1 as 2^kMinSizeLog.
21 // kMaxSizeLog: defines the last class as 2^kMaxSizeLog.
22 // kMidSizeLog: the classes starting from 1 increase with step
23 // 2^kMinSizeLog until 2^kMidSizeLog.
24 // kNumBits: the number of non-zero bits in sizes after 2^kMidSizeLog.
25 // E.g. with kNumBits==3 all size classes after 2^kMidSizeLog
26 // look like 0b1xx0..0, where x is either 0 or 1.
28 // Example: kNumBits=3, kMidSizeLog=4, kMidSizeLog=8, kMaxSizeLog=17:
30 // Classes 1 - 16 correspond to sizes 16 to 256 (size = class_id * 16).
31 // Next 4 classes: 256 + i * 64 (i = 1 to 4).
32 // Next 4 classes: 512 + i * 128 (i = 1 to 4).
34 // Next 4 classes: 2^k + i * 2^(k-2) (i = 1 to 4).
35 // Last class corresponds to kMaxSize = 1 << kMaxSizeLog.
37 // This structure of the size class map gives us:
38 // - Efficient table-free class-to-size and size-to-class functions.
39 // - Difference between two consequent size classes is between 14% and 25%
41 // This class also gives a hint to a thread-caching allocator about the amount
42 // of chunks that need to be cached per-thread:
43 // - kMaxNumCachedHint is a hint for maximal number of chunks per size class.
44 // The actual number is computed in TransferBatch.
45 // - (1 << kMaxBytesCachedLog) is the maximal number of bytes per size class.
47 // Part of output of SizeClassMap::Print():
48 // c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0
49 // c01 => s: 16 diff: +16 00% l 4 cached: 256 4096; id 1
50 // c02 => s: 32 diff: +16 100% l 5 cached: 256 8192; id 2
51 // c03 => s: 48 diff: +16 50% l 5 cached: 256 12288; id 3
52 // c04 => s: 64 diff: +16 33% l 6 cached: 256 16384; id 4
53 // c05 => s: 80 diff: +16 25% l 6 cached: 256 20480; id 5
54 // c06 => s: 96 diff: +16 20% l 6 cached: 256 24576; id 6
55 // c07 => s: 112 diff: +16 16% l 6 cached: 256 28672; id 7
57 // c08 => s: 128 diff: +16 14% l 7 cached: 256 32768; id 8
58 // c09 => s: 144 diff: +16 12% l 7 cached: 256 36864; id 9
59 // c10 => s: 160 diff: +16 11% l 7 cached: 256 40960; id 10
60 // c11 => s: 176 diff: +16 10% l 7 cached: 256 45056; id 11
61 // c12 => s: 192 diff: +16 09% l 7 cached: 256 49152; id 12
62 // c13 => s: 208 diff: +16 08% l 7 cached: 256 53248; id 13
63 // c14 => s: 224 diff: +16 07% l 7 cached: 256 57344; id 14
64 // c15 => s: 240 diff: +16 07% l 7 cached: 256 61440; id 15
66 // c16 => s: 256 diff: +16 06% l 8 cached: 256 65536; id 16
67 // c17 => s: 320 diff: +64 25% l 8 cached: 204 65280; id 17
68 // c18 => s: 384 diff: +64 20% l 8 cached: 170 65280; id 18
69 // c19 => s: 448 diff: +64 16% l 8 cached: 146 65408; id 19
71 // c20 => s: 512 diff: +64 14% l 9 cached: 128 65536; id 20
72 // c21 => s: 640 diff: +128 25% l 9 cached: 102 65280; id 21
73 // c22 => s: 768 diff: +128 20% l 9 cached: 85 65280; id 22
74 // c23 => s: 896 diff: +128 16% l 9 cached: 73 65408; id 23
76 // c24 => s: 1024 diff: +128 14% l 10 cached: 64 65536; id 24
77 // c25 => s: 1280 diff: +256 25% l 10 cached: 51 65280; id 25
78 // c26 => s: 1536 diff: +256 20% l 10 cached: 42 64512; id 26
79 // c27 => s: 1792 diff: +256 16% l 10 cached: 36 64512; id 27
83 // c48 => s: 65536 diff: +8192 14% l 16 cached: 1 65536; id 48
84 // c49 => s: 81920 diff: +16384 25% l 16 cached: 1 81920; id 49
85 // c50 => s: 98304 diff: +16384 20% l 16 cached: 1 98304; id 50
86 // c51 => s: 114688 diff: +16384 16% l 16 cached: 1 114688; id 51
88 // c52 => s: 131072 diff: +16384 14% l 17 cached: 1 131072; id 52
91 // Another example (kNumBits=2):
92 // c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0
93 // c01 => s: 32 diff: +32 00% l 5 cached: 64 2048; id 1
94 // c02 => s: 64 diff: +32 100% l 6 cached: 64 4096; id 2
95 // c03 => s: 96 diff: +32 50% l 6 cached: 64 6144; id 3
96 // c04 => s: 128 diff: +32 33% l 7 cached: 64 8192; id 4
97 // c05 => s: 160 diff: +32 25% l 7 cached: 64 10240; id 5
98 // c06 => s: 192 diff: +32 20% l 7 cached: 64 12288; id 6
99 // c07 => s: 224 diff: +32 16% l 7 cached: 64 14336; id 7
100 // c08 => s: 256 diff: +32 14% l 8 cached: 64 16384; id 8
101 // c09 => s: 384 diff: +128 50% l 8 cached: 42 16128; id 9
102 // c10 => s: 512 diff: +128 33% l 9 cached: 32 16384; id 10
103 // c11 => s: 768 diff: +256 50% l 9 cached: 21 16128; id 11
104 // c12 => s: 1024 diff: +256 33% l 10 cached: 16 16384; id 12
105 // c13 => s: 1536 diff: +512 50% l 10 cached: 10 15360; id 13
106 // c14 => s: 2048 diff: +512 33% l 11 cached: 8 16384; id 14
107 // c15 => s: 3072 diff: +1024 50% l 11 cached: 5 15360; id 15
108 // c16 => s: 4096 diff: +1024 33% l 12 cached: 4 16384; id 16
109 // c17 => s: 6144 diff: +2048 50% l 12 cached: 2 12288; id 17
110 // c18 => s: 8192 diff: +2048 33% l 13 cached: 2 16384; id 18
111 // c19 => s: 12288 diff: +4096 50% l 13 cached: 1 12288; id 19
112 // c20 => s: 16384 diff: +4096 33% l 14 cached: 1 16384; id 20
113 // c21 => s: 24576 diff: +8192 50% l 14 cached: 1 24576; id 21
114 // c22 => s: 32768 diff: +8192 33% l 15 cached: 1 32768; id 22
115 // c23 => s: 49152 diff: +16384 50% l 15 cached: 1 49152; id 23
116 // c24 => s: 65536 diff: +16384 33% l 16 cached: 1 65536; id 24
117 // c25 => s: 98304 diff: +32768 50% l 16 cached: 1 98304; id 25
118 // c26 => s: 131072 diff: +32768 33% l 17 cached: 1 131072; id 26
120 template <uptr kNumBits, uptr kMinSizeLog, uptr kMidSizeLog, uptr kMaxSizeLog,
121 uptr kMaxNumCachedHintT, uptr kMaxBytesCachedLog>
123 static const uptr kMinSize = 1 << kMinSizeLog;
124 static const uptr kMidSize = 1 << kMidSizeLog;
125 static const uptr kMidClass = kMidSize / kMinSize;
126 static const uptr S = kNumBits - 1;
127 static const uptr M = (1 << S) - 1;
130 // kMaxNumCachedHintT is a power of two. It serves as a hint
131 // for the size of TransferBatch, the actual size could be a bit smaller.
132 static const uptr kMaxNumCachedHint = kMaxNumCachedHintT;
133 COMPILER_CHECK((kMaxNumCachedHint & (kMaxNumCachedHint - 1)) == 0);
135 static const uptr kMaxSize = 1UL << kMaxSizeLog;
136 static const uptr kNumClasses =
137 kMidClass + ((kMaxSizeLog - kMidSizeLog) << S) + 1 + 1;
138 static const uptr kLargestClassID = kNumClasses - 2;
139 static const uptr kBatchClassID = kNumClasses - 1;
140 COMPILER_CHECK(kNumClasses >= 16 && kNumClasses <= 256);
141 static const uptr kNumClassesRounded =
142 kNumClasses <= 32 ? 32 :
143 kNumClasses <= 64 ? 64 :
144 kNumClasses <= 128 ? 128 : 256;
146 static uptr Size(uptr class_id) {
147 // Estimate the result for kBatchClassID because this class does not know
148 // the exact size of TransferBatch. It's OK since we are using the actual
149 // sizeof(TransferBatch) where it matters.
150 if (UNLIKELY(class_id == kBatchClassID))
151 return kMaxNumCachedHint * sizeof(uptr);
152 if (class_id <= kMidClass)
153 return kMinSize * class_id;
154 class_id -= kMidClass;
155 uptr t = kMidSize << (class_id >> S);
156 return t + (t >> S) * (class_id & M);
159 static uptr ClassID(uptr size) {
160 if (UNLIKELY(size > kMaxSize))
162 if (size <= kMidSize)
163 return (size + kMinSize - 1) >> kMinSizeLog;
164 const uptr l = MostSignificantSetBitIndex(size);
165 const uptr hbits = (size >> (l - S)) & M;
166 const uptr lbits = size & ((1U << (l - S)) - 1);
167 const uptr l1 = l - kMidSizeLog;
168 return kMidClass + (l1 << S) + hbits + (lbits > 0);
171 static uptr MaxCachedHint(uptr size) {
172 DCHECK_LE(size, kMaxSize);
173 if (UNLIKELY(size == 0))
176 // Force a 32-bit division if the template parameters allow for it.
177 if (kMaxBytesCachedLog > 31 || kMaxSizeLog > 31)
178 n = (1UL << kMaxBytesCachedLog) / size;
180 n = (1U << kMaxBytesCachedLog) / static_cast<u32>(size);
181 return Max<uptr>(1U, Min(kMaxNumCachedHint, n));
184 static void Print() {
186 uptr total_cached = 0;
187 for (uptr i = 0; i < kNumClasses; i++) {
189 if (s >= kMidSize / 2 && (s & (s - 1)) == 0)
192 uptr p = prev_s ? (d * 100 / prev_s) : 0;
193 uptr l = s ? MostSignificantSetBitIndex(s) : 0;
194 uptr cached = MaxCachedHint(s) * s;
195 if (i == kBatchClassID)
197 Printf("c%02zd => s: %zd diff: +%zd %02zd%% l %zd "
198 "cached: %zd %zd; id %zd\n",
199 i, Size(i), d, p, l, MaxCachedHint(s), cached, ClassID(s));
200 total_cached += cached;
203 Printf("Total cached: %zd\n", total_cached);
206 static void Validate() {
207 for (uptr c = 1; c < kNumClasses; c++) {
208 // Printf("Validate: c%zd\n", c);
211 if (c == kBatchClassID)
213 CHECK_EQ(ClassID(s), c);
214 if (c < kLargestClassID)
215 CHECK_EQ(ClassID(s + 1), c + 1);
216 CHECK_EQ(ClassID(s - 1), c);
217 CHECK_GT(Size(c), Size(c - 1));
219 CHECK_EQ(ClassID(kMaxSize + 1), 0);
221 for (uptr s = 1; s <= kMaxSize; s++) {
223 // Printf("s%zd => c%zd\n", s, c);
224 CHECK_LT(c, kNumClasses);
225 CHECK_GE(Size(c), s);
227 CHECK_LT(Size(c - 1), s);
232 typedef SizeClassMap<3, 4, 8, 17, 128, 16> DefaultSizeClassMap;
233 typedef SizeClassMap<3, 4, 8, 17, 64, 14> CompactSizeClassMap;
234 typedef SizeClassMap<2, 5, 9, 16, 64, 14> VeryCompactSizeClassMap;
236 // The following SizeClassMap only holds a way small number of cached entries,
237 // allowing for denser per-class arrays, smaller memory footprint and usually
238 // better performances in threaded environments.
239 typedef SizeClassMap<3, 4, 8, 17, 8, 10> DenseSizeClassMap;
240 // Similar to VeryCompact map above, this one has a small number of different
241 // size classes, and also reduced thread-local caches.
242 typedef SizeClassMap<2, 5, 9, 16, 8, 10> VeryDenseSizeClassMap;