1 //===-- sanitizer_allocator_size_class_map.h --------------------*- C++ -*-===// 2 // 3 // This file is distributed under the University of Illinois Open Source 4 // License. See LICENSE.TXT for details. 5 // 6 //===----------------------------------------------------------------------===// 7 // 8 // Part of the Sanitizer Allocator. 9 // 10 //===----------------------------------------------------------------------===// 11 #ifndef SANITIZER_ALLOCATOR_H 12 #error This file must be included inside sanitizer_allocator.h 13 #endif 14 15 // SizeClassMap maps allocation sizes into size classes and back. 16 // Class 0 always corresponds to size 0. 17 // The other sizes are controlled by the template parameters: 18 // kMinSizeLog: defines the class 1 as 2^kMinSizeLog. 19 // kMaxSizeLog: defines the last class as 2^kMaxSizeLog. 20 // kMidSizeLog: the classes starting from 1 increase with step 21 // 2^kMinSizeLog until 2^kMidSizeLog. 22 // kNumBits: the number of non-zero bits in sizes after 2^kMidSizeLog. 23 // E.g. with kNumBits==3 all size classes after 2^kMidSizeLog 24 // look like 0b1xx0..0, where x is either 0 or 1. 25 // 26 // Example: kNumBits=3, kMidSizeLog=4, kMidSizeLog=8, kMaxSizeLog=17: 27 // 28 // Classes 1 - 16 correspond to sizes 16 to 256 (size = class_id * 16). 29 // Next 4 classes: 256 + i * 64 (i = 1 to 4). 30 // Next 4 classes: 512 + i * 128 (i = 1 to 4). 31 // ... 32 // Next 4 classes: 2^k + i * 2^(k-2) (i = 1 to 4). 33 // Last class corresponds to kMaxSize = 1 << kMaxSizeLog. 34 // 35 // This structure of the size class map gives us: 36 // - Efficient table-free class-to-size and size-to-class functions. 37 // - Difference between two consequent size classes is between 14% and 25% 38 // 39 // This class also gives a hint to a thread-caching allocator about the amount 40 // of chunks that need to be cached per-thread: 41 // - kMaxNumCachedHint is a hint for maximal number of chunks per size class. 42 // The actual number is computed in TransferBatch. 43 // - (1 << kMaxBytesCachedLog) is the maximal number of bytes per size class. 44 // 45 // Part of output of SizeClassMap::Print(): 46 // c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0 47 // c01 => s: 16 diff: +16 00% l 4 cached: 256 4096; id 1 48 // c02 => s: 32 diff: +16 100% l 5 cached: 256 8192; id 2 49 // c03 => s: 48 diff: +16 50% l 5 cached: 256 12288; id 3 50 // c04 => s: 64 diff: +16 33% l 6 cached: 256 16384; id 4 51 // c05 => s: 80 diff: +16 25% l 6 cached: 256 20480; id 5 52 // c06 => s: 96 diff: +16 20% l 6 cached: 256 24576; id 6 53 // c07 => s: 112 diff: +16 16% l 6 cached: 256 28672; id 7 54 // 55 // c08 => s: 128 diff: +16 14% l 7 cached: 256 32768; id 8 56 // c09 => s: 144 diff: +16 12% l 7 cached: 256 36864; id 9 57 // c10 => s: 160 diff: +16 11% l 7 cached: 256 40960; id 10 58 // c11 => s: 176 diff: +16 10% l 7 cached: 256 45056; id 11 59 // c12 => s: 192 diff: +16 09% l 7 cached: 256 49152; id 12 60 // c13 => s: 208 diff: +16 08% l 7 cached: 256 53248; id 13 61 // c14 => s: 224 diff: +16 07% l 7 cached: 256 57344; id 14 62 // c15 => s: 240 diff: +16 07% l 7 cached: 256 61440; id 15 63 // 64 // c16 => s: 256 diff: +16 06% l 8 cached: 256 65536; id 16 65 // c17 => s: 320 diff: +64 25% l 8 cached: 204 65280; id 17 66 // c18 => s: 384 diff: +64 20% l 8 cached: 170 65280; id 18 67 // c19 => s: 448 diff: +64 16% l 8 cached: 146 65408; id 19 68 // 69 // c20 => s: 512 diff: +64 14% l 9 cached: 128 65536; id 20 70 // c21 => s: 640 diff: +128 25% l 9 cached: 102 65280; id 21 71 // c22 => s: 768 diff: +128 20% l 9 cached: 85 65280; id 22 72 // c23 => s: 896 diff: +128 16% l 9 cached: 73 65408; id 23 73 // 74 // c24 => s: 1024 diff: +128 14% l 10 cached: 64 65536; id 24 75 // c25 => s: 1280 diff: +256 25% l 10 cached: 51 65280; id 25 76 // c26 => s: 1536 diff: +256 20% l 10 cached: 42 64512; id 26 77 // c27 => s: 1792 diff: +256 16% l 10 cached: 36 64512; id 27 78 // 79 // ... 80 // 81 // c48 => s: 65536 diff: +8192 14% l 16 cached: 1 65536; id 48 82 // c49 => s: 81920 diff: +16384 25% l 16 cached: 1 81920; id 49 83 // c50 => s: 98304 diff: +16384 20% l 16 cached: 1 98304; id 50 84 // c51 => s: 114688 diff: +16384 16% l 16 cached: 1 114688; id 51 85 // 86 // c52 => s: 131072 diff: +16384 14% l 17 cached: 1 131072; id 52 87 // 88 // 89 // Another example (kNumBits=2): 90 // c00 => s: 0 diff: +0 00% l 0 cached: 0 0; id 0 91 // c01 => s: 32 diff: +32 00% l 5 cached: 64 2048; id 1 92 // c02 => s: 64 diff: +32 100% l 6 cached: 64 4096; id 2 93 // c03 => s: 96 diff: +32 50% l 6 cached: 64 6144; id 3 94 // c04 => s: 128 diff: +32 33% l 7 cached: 64 8192; id 4 95 // c05 => s: 160 diff: +32 25% l 7 cached: 64 10240; id 5 96 // c06 => s: 192 diff: +32 20% l 7 cached: 64 12288; id 6 97 // c07 => s: 224 diff: +32 16% l 7 cached: 64 14336; id 7 98 // c08 => s: 256 diff: +32 14% l 8 cached: 64 16384; id 8 99 // c09 => s: 384 diff: +128 50% l 8 cached: 42 16128; id 9 100 // c10 => s: 512 diff: +128 33% l 9 cached: 32 16384; id 10 101 // c11 => s: 768 diff: +256 50% l 9 cached: 21 16128; id 11 102 // c12 => s: 1024 diff: +256 33% l 10 cached: 16 16384; id 12 103 // c13 => s: 1536 diff: +512 50% l 10 cached: 10 15360; id 13 104 // c14 => s: 2048 diff: +512 33% l 11 cached: 8 16384; id 14 105 // c15 => s: 3072 diff: +1024 50% l 11 cached: 5 15360; id 15 106 // c16 => s: 4096 diff: +1024 33% l 12 cached: 4 16384; id 16 107 // c17 => s: 6144 diff: +2048 50% l 12 cached: 2 12288; id 17 108 // c18 => s: 8192 diff: +2048 33% l 13 cached: 2 16384; id 18 109 // c19 => s: 12288 diff: +4096 50% l 13 cached: 1 12288; id 19 110 // c20 => s: 16384 diff: +4096 33% l 14 cached: 1 16384; id 20 111 // c21 => s: 24576 diff: +8192 50% l 14 cached: 1 24576; id 21 112 // c22 => s: 32768 diff: +8192 33% l 15 cached: 1 32768; id 22 113 // c23 => s: 49152 diff: +16384 50% l 15 cached: 1 49152; id 23 114 // c24 => s: 65536 diff: +16384 33% l 16 cached: 1 65536; id 24 115 // c25 => s: 98304 diff: +32768 50% l 16 cached: 1 98304; id 25 116 // c26 => s: 131072 diff: +32768 33% l 17 cached: 1 131072; id 26 117 118 template <uptr kNumBits, uptr kMinSizeLog, uptr kMidSizeLog, uptr kMaxSizeLog, 119 uptr kMaxNumCachedHintT, uptr kMaxBytesCachedLog> 120 class SizeClassMap { 121 static const uptr kMinSize = 1 << kMinSizeLog; 122 static const uptr kMidSize = 1 << kMidSizeLog; 123 static const uptr kMidClass = kMidSize / kMinSize; 124 static const uptr S = kNumBits - 1; 125 static const uptr M = (1 << S) - 1; 126 127 public: 128 // kMaxNumCachedHintT is a power of two. It serves as a hint 129 // for the size of TransferBatch, the actual size could be a bit smaller. 130 static const uptr kMaxNumCachedHint = kMaxNumCachedHintT; 131 COMPILER_CHECK((kMaxNumCachedHint & (kMaxNumCachedHint - 1)) == 0); 132 133 static const uptr kMaxSize = 1UL << kMaxSizeLog; 134 static const uptr kNumClasses = 135 kMidClass + ((kMaxSizeLog - kMidSizeLog) << S) + 1 + 1; 136 static const uptr kLargestClassID = kNumClasses - 2; 137 static const uptr kBatchClassID = kNumClasses - 1; 138 COMPILER_CHECK(kNumClasses >= 16 && kNumClasses <= 256); 139 static const uptr kNumClassesRounded = 140 kNumClasses <= 32 ? 32 : 141 kNumClasses <= 64 ? 64 : 142 kNumClasses <= 128 ? 128 : 256; 143 Size(uptr class_id)144 static uptr Size(uptr class_id) { 145 // Estimate the result for kBatchClassID because this class does not know 146 // the exact size of TransferBatch. It's OK since we are using the actual 147 // sizeof(TransferBatch) where it matters. 148 if (UNLIKELY(class_id == kBatchClassID)) 149 return kMaxNumCachedHint * sizeof(uptr); 150 if (class_id <= kMidClass) 151 return kMinSize * class_id; 152 class_id -= kMidClass; 153 uptr t = kMidSize << (class_id >> S); 154 return t + (t >> S) * (class_id & M); 155 } 156 ClassID(uptr size)157 static uptr ClassID(uptr size) { 158 if (UNLIKELY(size > kMaxSize)) 159 return 0; 160 if (size <= kMidSize) 161 return (size + kMinSize - 1) >> kMinSizeLog; 162 uptr l = MostSignificantSetBitIndex(size); 163 uptr hbits = (size >> (l - S)) & M; 164 uptr lbits = size & ((1 << (l - S)) - 1); 165 uptr l1 = l - kMidSizeLog; 166 return kMidClass + (l1 << S) + hbits + (lbits > 0); 167 } 168 MaxCachedHint(uptr class_id)169 static uptr MaxCachedHint(uptr class_id) { 170 // Estimate the result for kBatchClassID because this class does not know 171 // the exact size of TransferBatch. We need to cache fewer batches than user 172 // chunks, so this number can be small. 173 if (UNLIKELY(class_id == kBatchClassID)) 174 return 16; 175 if (UNLIKELY(class_id == 0)) 176 return 0; 177 uptr n = (1UL << kMaxBytesCachedLog) / Size(class_id); 178 return Max<uptr>(1, Min(kMaxNumCachedHint, n)); 179 } 180 Print()181 static void Print() { 182 uptr prev_s = 0; 183 uptr total_cached = 0; 184 for (uptr i = 0; i < kNumClasses; i++) { 185 uptr s = Size(i); 186 if (s >= kMidSize / 2 && (s & (s - 1)) == 0) 187 Printf("\n"); 188 uptr d = s - prev_s; 189 uptr p = prev_s ? (d * 100 / prev_s) : 0; 190 uptr l = s ? MostSignificantSetBitIndex(s) : 0; 191 uptr cached = MaxCachedHint(i) * s; 192 if (i == kBatchClassID) 193 d = p = l = 0; 194 Printf("c%02zd => s: %zd diff: +%zd %02zd%% l %zd " 195 "cached: %zd %zd; id %zd\n", 196 i, Size(i), d, p, l, MaxCachedHint(i), cached, ClassID(s)); 197 total_cached += cached; 198 prev_s = s; 199 } 200 Printf("Total cached: %zd\n", total_cached); 201 } 202 Validate()203 static void Validate() { 204 for (uptr c = 1; c < kNumClasses; c++) { 205 // Printf("Validate: c%zd\n", c); 206 uptr s = Size(c); 207 CHECK_NE(s, 0U); 208 if (c == kBatchClassID) 209 continue; 210 CHECK_EQ(ClassID(s), c); 211 if (c < kLargestClassID) 212 CHECK_EQ(ClassID(s + 1), c + 1); 213 CHECK_EQ(ClassID(s - 1), c); 214 CHECK_GT(Size(c), Size(c - 1)); 215 } 216 CHECK_EQ(ClassID(kMaxSize + 1), 0); 217 218 for (uptr s = 1; s <= kMaxSize; s++) { 219 uptr c = ClassID(s); 220 // Printf("s%zd => c%zd\n", s, c); 221 CHECK_LT(c, kNumClasses); 222 CHECK_GE(Size(c), s); 223 if (c > 0) 224 CHECK_LT(Size(c - 1), s); 225 } 226 } 227 }; 228 229 typedef SizeClassMap<3, 4, 8, 17, 128, 16> DefaultSizeClassMap; 230 typedef SizeClassMap<3, 4, 8, 17, 64, 14> CompactSizeClassMap; 231 typedef SizeClassMap<2, 5, 9, 16, 64, 14> VeryCompactSizeClassMap; 232