1 /* 2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP 26 #define SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP 27 28 #include "oops/array.hpp" 29 #include "oops/symbol.hpp" 30 #include "utilities/hashtable.hpp" 31 32 33 template < 34 typename K, 35 typename V, 36 V (*DECODE)(address base_address, u4 offset), 37 bool (*EQUALS)(V value, K key, int len) 38 > 39 class CompactHashtable; 40 class NumberSeq; 41 class SimpleCompactHashtable; 42 class SerializeClosure; 43 44 // Stats for symbol tables in the CDS archive 45 class CompactHashtableStats { 46 public: 47 int hashentry_count; 48 int hashentry_bytes; 49 int bucket_count; 50 int bucket_bytes; 51 }; 52 53 #if INCLUDE_CDS 54 ///////////////////////////////////////////////////////////////////////// 55 // 56 // The compact hash table writer. Used at dump time for writing out 57 // the compact table to the shared archive. 58 // 59 // At dump time, the CompactHashtableWriter obtains all entries from the 60 // symbol/string table and adds them to a new temporary hash table. The hash 61 // table size (number of buckets) is calculated using 62 // '(num_entries + bucket_size - 1) / bucket_size'. The default bucket 63 // size is 4 and can be changed by -XX:SharedSymbolTableBucketSize option. 64 // 4 is chosen because it produces smaller sized bucket on average for 65 // faster lookup. It also has relatively small number of empty buckets and 66 // good distribution of the entries. 67 // 68 // We use a simple hash function (hash % num_bucket) for the table. 69 // The new table is compacted when written out. Please see comments 70 // above the CompactHashtable class for the table layout detail. The bucket 71 // offsets are written to the archive as part of the compact table. The 72 // bucket offset is encoded in the low 30-bit (0-29) and the bucket type 73 // (regular or compact) are encoded in bit[31, 30]. For buckets with more 74 // than one entry, both hash and entry offset are written to the 75 // table. For buckets with only one entry, only the entry offset is written 76 // to the table and the buckets are tagged as compact in their type bits. 77 // Buckets without entry are skipped from the table. Their offsets are 78 // still written out for faster lookup. 79 // 80 class CompactHashtableWriter: public StackObj { 81 public: 82 class Entry { 83 unsigned int _hash; 84 u4 _value; 85 86 public: 87 Entry() {} 88 Entry(unsigned int hash, u4 val) : _hash(hash), _value(val) {} 89 90 u4 value() { 91 return _value; 92 } 93 unsigned int hash() { 94 return _hash; 95 } 96 97 bool operator==(const CompactHashtableWriter::Entry& other) { 98 return (_value == other._value && _hash == other._hash); 99 } 100 }; // class CompactHashtableWriter::Entry 101 102 private: 103 int _num_entries; 104 int _num_buckets; 105 int _num_empty_buckets; 106 int _num_value_only_buckets; 107 int _num_other_buckets; 108 GrowableArray<Entry>** _buckets; 109 CompactHashtableStats* _stats; 110 Array<u4>* _compact_buckets; 111 Array<u4>* _compact_entries; 112 113 public: 114 // This is called at dump-time only 115 CompactHashtableWriter(int num_buckets, CompactHashtableStats* stats); 116 ~CompactHashtableWriter(); 117 118 void add(unsigned int hash, u4 value); 119 120 private: 121 void allocate_table(); 122 void dump_table(NumberSeq* summary); 123 124 public: 125 void dump(SimpleCompactHashtable *cht, const char* table_name); 126 }; 127 #endif // INCLUDE_CDS 128 129 #define REGULAR_BUCKET_TYPE 0 130 #define VALUE_ONLY_BUCKET_TYPE 1 131 #define TABLEEND_BUCKET_TYPE 3 132 #define BUCKET_OFFSET_MASK 0x3FFFFFFF 133 #define BUCKET_OFFSET(info) ((info) & BUCKET_OFFSET_MASK) 134 #define BUCKET_TYPE_SHIFT 30 135 #define BUCKET_TYPE(info) (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT) 136 #define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK)) 137 138 ///////////////////////////////////////////////////////////////////////////// 139 // 140 // CompactHashtable is used to store the CDS archive's symbol/string tables. 141 // 142 // Because these tables are read-only (no entries can be added/deleted) at run-time 143 // and tend to have large number of entries, we try to minimize the footprint 144 // cost per entry. 145 // 146 // The CompactHashtable is split into two arrays 147 // 148 // u4 buckets[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset 149 // u4 entries[<variable size>] 150 // 151 // The size of buckets[] is 'num_buckets + 1'. Each entry of 152 // buckets[] is a 32-bit encoding of the bucket type and bucket offset, 153 // with the type in the left-most 2-bit and offset in the remaining 30-bit. 154 // The last entry is a special type. It contains the end of the last 155 // bucket. 156 // 157 // There are two types of buckets, regular buckets and value_only buckets. The 158 // value_only buckets have '01' in their highest 2-bit, and regular buckets have 159 // '00' in their highest 2-bit. 160 // 161 // For normal buckets, each entry is 8 bytes in the entries[]: 162 // u4 hash; /* symbol/string hash */ 163 // union { 164 // u4 offset; /* Symbol* sym = (Symbol*)(base_address + offset) */ 165 // narrowOop str; /* String narrowOop encoding */ 166 // } 167 // 168 // 169 // For value_only buckets, each entry has only the 4-byte 'offset' in the entries[]. 170 // 171 // Example -- note that the second bucket is a VALUE_ONLY_BUCKET_TYPE so the hash code 172 // is skipped. 173 // buckets[0, 4, 5, ....] 174 // | | | 175 // | | +---+ 176 // | | | 177 // | +----+ | 178 // v v v 179 // entries[H,O,H,O,O,H,O,H,O.....] 180 // 181 // See CompactHashtable::lookup() for how the table is searched at runtime. 182 // See CompactHashtableWriter::dump() for how the table is written at CDS 183 // dump time. 184 // 185 class SimpleCompactHashtable { 186 protected: 187 address _base_address; 188 u4 _bucket_count; 189 u4 _entry_count; 190 u4* _buckets; 191 u4* _entries; 192 193 public: 194 SimpleCompactHashtable() { 195 _entry_count = 0; 196 _bucket_count = 0; 197 _buckets = 0; 198 _entries = 0; 199 } 200 201 void reset() { 202 _bucket_count = 0; 203 _entry_count = 0; 204 _buckets = 0; 205 _entries = 0; 206 } 207 208 void init(address base_address, u4 entry_count, u4 bucket_count, u4* buckets, u4* entries) { 209 _base_address = base_address; 210 _bucket_count = bucket_count; 211 _entry_count = entry_count; 212 _buckets = buckets; 213 _entries = entries; 214 } 215 216 // For reading from/writing to the CDS archive 217 void serialize(SerializeClosure* soc) NOT_CDS_RETURN; 218 219 inline bool empty() { 220 return (_entry_count == 0); 221 } 222 }; 223 224 template < 225 typename K, 226 typename V, 227 V (*DECODE)(address base_address, u4 offset), 228 bool (*EQUALS)(V value, K key, int len) 229 > 230 class CompactHashtable : public SimpleCompactHashtable { 231 friend class VMStructs; 232 233 V decode(u4 offset) const { 234 return DECODE(_base_address, offset); 235 } 236 237 public: 238 CompactHashtable() : SimpleCompactHashtable() {} 239 240 // Lookup a value V from the compact table using key K 241 inline V lookup(K key, unsigned int hash, int len) const { 242 if (_entry_count > 0) { 243 int index = hash % _bucket_count; 244 u4 bucket_info = _buckets[index]; 245 u4 bucket_offset = BUCKET_OFFSET(bucket_info); 246 int bucket_type = BUCKET_TYPE(bucket_info); 247 u4* entry = _entries + bucket_offset; 248 249 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) { 250 V value = decode(entry[0]); 251 if (EQUALS(value, key, len)) { 252 return value; 253 } 254 } else { 255 // This is a regular bucket, which has more than one 256 // entries. Each entry is a pair of entry (hash, offset). 257 // Seek until the end of the bucket. 258 u4* entry_max = _entries + BUCKET_OFFSET(_buckets[index + 1]); 259 while (entry < entry_max) { 260 unsigned int h = (unsigned int)(entry[0]); 261 if (h == hash) { 262 V value = decode(entry[1]); 263 if (EQUALS(value, key, len)) { 264 return value; 265 } 266 } 267 entry += 2; 268 } 269 } 270 } 271 return NULL; 272 } 273 274 template <class ITER> 275 inline void iterate(ITER* iter) const { 276 for (u4 i = 0; i < _bucket_count; i++) { 277 u4 bucket_info = _buckets[i]; 278 u4 bucket_offset = BUCKET_OFFSET(bucket_info); 279 int bucket_type = BUCKET_TYPE(bucket_info); 280 u4* entry = _entries + bucket_offset; 281 282 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) { 283 iter->do_value(decode(entry[0])); 284 } else { 285 u4*entry_max = _entries + BUCKET_OFFSET(_buckets[i + 1]); 286 while (entry < entry_max) { 287 iter->do_value(decode(entry[1])); 288 entry += 2; 289 } 290 } 291 } 292 } 293 }; 294 295 //////////////////////////////////////////////////////////////////////// 296 // 297 // Read/Write the contents of a hashtable textual dump (created by 298 // SymbolTable::dump and StringTable::dump). 299 // Because the dump file may be big (hundred of MB in extreme cases), 300 // we use mmap for fast access when reading it. 301 // 302 class HashtableTextDump { 303 int _fd; 304 const char* _base; 305 const char* _p; 306 const char* _end; 307 const char* _filename; 308 size_t _size; 309 int _prefix_type; 310 int _line_no; 311 public: 312 HashtableTextDump(const char* filename); 313 ~HashtableTextDump(); 314 315 enum { 316 SymbolPrefix = 1 << 0, 317 StringPrefix = 1 << 1, 318 Unknown = 1 << 2 319 }; 320 321 void quit(const char* err, const char* msg); 322 323 inline int remain() { 324 return (int)(_end - _p); 325 } 326 327 void corrupted(const char *p, const char *msg); 328 329 inline void corrupted_if(bool cond, const char *msg) { 330 if (cond) { 331 corrupted(_p, msg); 332 } 333 } 334 335 bool skip_newline(); 336 int skip(char must_be_char); 337 void skip_past(char c); 338 void check_version(const char* ver); 339 340 inline void get_num(char delim, int *num) { 341 const char* p = _p; 342 const char* end = _end; 343 u8 n = 0; 344 345 while (p < end) { 346 char c = *p++; 347 if ('0' <= c && c <= '9') { 348 n = n * 10 + (c - '0'); 349 if (n > (u8)INT_MAX) { 350 corrupted(_p, "Num overflow"); 351 } 352 } else if (c == delim) { 353 _p = p; 354 *num = (int)n; 355 return; 356 } else { 357 // Not [0-9], not 'delim' 358 corrupted(_p, "Unrecognized format");; 359 } 360 } 361 362 corrupted(_end, "Incorrect format"); 363 ShouldNotReachHere(); 364 } 365 366 void scan_prefix_type(); 367 int scan_prefix(int* utf8_length); 368 int scan_string_prefix(); 369 int scan_symbol_prefix(); 370 371 jchar unescape(const char* from, const char* end, int count); 372 void get_utf8(char* utf8_buffer, int utf8_length); 373 static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length); 374 }; 375 376 #endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP