1//===-- sanitizer_allocator_size_class_map.h --------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// Part of the Sanitizer Allocator. 11// 12//===----------------------------------------------------------------------===// 13#ifndef SANITIZER_ALLOCATOR_H 14#error This file must be included inside sanitizer_allocator.h 15#endif 16 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. 27// 28// Example: kNumBits=3, kMidSizeLog=4, kMidSizeLog=8, kMaxSizeLog=17: 29// 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). 33// ... 34// Next 4 classes: 2^k + i * 2^(k-2) (i = 1 to 4). 35// Last class corresponds to kMaxSize = 1 << kMaxSizeLog. 36// 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% 40// 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. 46// 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 56// 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 65// 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 70// 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 75// 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 80// 81// ... 82// 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 87// 88// c52 => s: 131072 diff: +16384 14% l 17 cached: 1 131072; id 52 89// 90// 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 26 119 120template <uptr kNumBits, uptr kMinSizeLog, uptr kMidSizeLog, uptr kMaxSizeLog, 121 uptr kMaxNumCachedHintT, uptr kMaxBytesCachedLog> 122class SizeClassMap { 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; 128 129 public: 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); 134 135 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; 145 146 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); 157 } 158 159 static uptr ClassID(uptr size) { 160 if (UNLIKELY(size > kMaxSize)) 161 return 0; 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); 169 } 170 171 static uptr MaxCachedHint(uptr size) { 172 DCHECK_LE(size, kMaxSize); 173 if (UNLIKELY(size == 0)) 174 return 0; 175 uptr n; 176 // Force a 32-bit division if the template parameters allow for it. 177 if (kMaxBytesCachedLog > 31 || kMaxSizeLog > 31) 178 n = (1UL << kMaxBytesCachedLog) / size; 179 else 180 n = (1U << kMaxBytesCachedLog) / static_cast<u32>(size); 181 return Max<uptr>(1U, Min(kMaxNumCachedHint, n)); 182 } 183 184 static void Print() { 185 uptr prev_s = 0; 186 uptr total_cached = 0; 187 for (uptr i = 0; i < kNumClasses; i++) { 188 uptr s = Size(i); 189 if (s >= kMidSize / 2 && (s & (s - 1)) == 0) 190 Printf("\n"); 191 uptr d = s - prev_s; 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) 196 d = p = l = 0; 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; 201 prev_s = s; 202 } 203 Printf("Total cached: %zd\n", total_cached); 204 } 205 206 static void Validate() { 207 for (uptr c = 1; c < kNumClasses; c++) { 208 // Printf("Validate: c%zd\n", c); 209 uptr s = Size(c); 210 CHECK_NE(s, 0U); 211 if (c == kBatchClassID) 212 continue; 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)); 218 } 219 CHECK_EQ(ClassID(kMaxSize + 1), 0); 220 221 for (uptr s = 1; s <= kMaxSize; s++) { 222 uptr c = ClassID(s); 223 // Printf("s%zd => c%zd\n", s, c); 224 CHECK_LT(c, kNumClasses); 225 CHECK_GE(Size(c), s); 226 if (c > 0) 227 CHECK_LT(Size(c - 1), s); 228 } 229 } 230}; 231 232typedef SizeClassMap<3, 4, 8, 17, 128, 16> DefaultSizeClassMap; 233typedef SizeClassMap<3, 4, 8, 17, 64, 14> CompactSizeClassMap; 234typedef SizeClassMap<2, 5, 9, 16, 64, 14> VeryCompactSizeClassMap; 235 236// 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. 239typedef 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. 242typedef SizeClassMap<2, 5, 9, 16, 8, 10> VeryDenseSizeClassMap; 243