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/growableArray.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 static int default_num_buckets(size_t num_entries) {
128 return default_num_buckets((int)num_entries);
129 }
130 static int default_num_buckets(int num_entries) {
131 int num_buckets = num_entries / SharedSymbolTableBucketSize;
132 // calculation of num_buckets can result in zero buckets, we need at least one
133 return (num_buckets < 1) ? 1 : num_buckets;
134 }
135 };
136 #endif // INCLUDE_CDS
137
138 #define REGULAR_BUCKET_TYPE 0
139 #define VALUE_ONLY_BUCKET_TYPE 1
140 #define TABLEEND_BUCKET_TYPE 3
141 #define BUCKET_OFFSET_MASK 0x3FFFFFFF
142 #define BUCKET_OFFSET(info) ((info) & BUCKET_OFFSET_MASK)
143 #define BUCKET_TYPE_SHIFT 30
144 #define BUCKET_TYPE(info) (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT)
145 #define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK))
146
147 /////////////////////////////////////////////////////////////////////////////
148 //
149 // CompactHashtable is used to store the CDS archive's symbol/string tables.
150 //
151 // Because these tables are read-only (no entries can be added/deleted) at run-time
152 // and tend to have large number of entries, we try to minimize the footprint
153 // cost per entry.
154 //
155 // The CompactHashtable is split into two arrays
156 //
157 // u4 buckets[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset
158 // u4 entries[<variable size>]
159 //
160 // The size of buckets[] is 'num_buckets + 1'. Each entry of
161 // buckets[] is a 32-bit encoding of the bucket type and bucket offset,
162 // with the type in the left-most 2-bit and offset in the remaining 30-bit.
163 // The last entry is a special type. It contains the end of the last
164 // bucket.
165 //
166 // There are two types of buckets, regular buckets and value_only buckets. The
167 // value_only buckets have '01' in their highest 2-bit, and regular buckets have
168 // '00' in their highest 2-bit.
169 //
170 // For normal buckets, each entry is 8 bytes in the entries[]:
171 // u4 hash; /* symbol/string hash */
172 // union {
173 // u4 offset; /* Symbol* sym = (Symbol*)(base_address + offset) */
174 // narrowOop str; /* String narrowOop encoding */
175 // }
176 //
177 //
178 // For value_only buckets, each entry has only the 4-byte 'offset' in the entries[].
179 //
180 // Example -- note that the second bucket is a VALUE_ONLY_BUCKET_TYPE so the hash code
181 // is skipped.
182 // buckets[0, 4, 5, ....]
183 // | | |
184 // | | +---+
185 // | | |
186 // | +----+ |
187 // v v v
188 // entries[H,O,H,O,O,H,O,H,O.....]
189 //
190 // See CompactHashtable::lookup() for how the table is searched at runtime.
191 // See CompactHashtableWriter::dump() for how the table is written at CDS
192 // dump time.
193 //
194 class SimpleCompactHashtable {
195 protected:
196 address _base_address;
197 u4 _bucket_count;
198 u4 _entry_count;
199 u4* _buckets;
200 u4* _entries;
201
202 public:
203 SimpleCompactHashtable() {
204 _entry_count = 0;
205 _bucket_count = 0;
206 _buckets = 0;
207 _entries = 0;
208 }
209
210 void reset() {
211 _bucket_count = 0;
212 _entry_count = 0;
213 _buckets = 0;
214 _entries = 0;
215 }
216
217 void init(address base_address, u4 entry_count, u4 bucket_count, u4* buckets, u4* entries) {
218 _base_address = base_address;
219 _bucket_count = bucket_count;
220 _entry_count = entry_count;
221 _buckets = buckets;
222 _entries = entries;
223 }
224
225 // Read/Write the table's header from/to the CDS archive
226 void serialize_header(SerializeClosure* soc) NOT_CDS_RETURN;
227
228 inline bool empty() {
229 return (_entry_count == 0);
230 }
231 };
232
233 template <
234 typename K,
235 typename V,
236 V (*DECODE)(address base_address, u4 offset),
237 bool (*EQUALS)(V value, K key, int len)
238 >
239 class CompactHashtable : public SimpleCompactHashtable {
240 friend class VMStructs;
241
242 V decode(u4 offset) const {
243 return DECODE(_base_address, offset);
244 }
245
246 public:
247 // Lookup a value V from the compact table using key K
248 inline V lookup(K key, unsigned int hash, int len) const {
249 if (_entry_count > 0) {
250 int index = hash % _bucket_count;
251 u4 bucket_info = _buckets[index];
252 u4 bucket_offset = BUCKET_OFFSET(bucket_info);
253 int bucket_type = BUCKET_TYPE(bucket_info);
254 u4* entry = _entries + bucket_offset;
255
256 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {
257 V value = decode(entry[0]);
258 if (EQUALS(value, key, len)) {
259 return value;
260 }
261 } else {
262 // This is a regular bucket, which has more than one
263 // entries. Each entry is a pair of entry (hash, offset).
264 // Seek until the end of the bucket.
265 u4* entry_max = _entries + BUCKET_OFFSET(_buckets[index + 1]);
266 while (entry < entry_max) {
267 unsigned int h = (unsigned int)(entry[0]);
268 if (h == hash) {
269 V value = decode(entry[1]);
270 if (EQUALS(value, key, len)) {
271 return value;
272 }
273 }
274 entry += 2;
275 }
276 }
277 }
278 return NULL;
279 }
280
281 template <class ITER>
282 inline void iterate(ITER* iter) const {
283 for (u4 i = 0; i < _bucket_count; i++) {
284 u4 bucket_info = _buckets[i];
285 u4 bucket_offset = BUCKET_OFFSET(bucket_info);
286 int bucket_type = BUCKET_TYPE(bucket_info);
287 u4* entry = _entries + bucket_offset;
288
289 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {
290 iter->do_value(decode(entry[0]));
291 } else {
292 u4*entry_max = _entries + BUCKET_OFFSET(_buckets[i + 1]);
293 while (entry < entry_max) {
294 iter->do_value(decode(entry[1]));
295 entry += 2;
296 }
297 }
298 }
299 }
300
301 void print_table_statistics(outputStream* st, const char* name) {
302 st->print_cr("%s statistics:", name);
303 int total_entries = 0;
304 int max_bucket = 0;
305 for (u4 i = 0; i < _bucket_count; i++) {
306 u4 bucket_info = _buckets[i];
307 int bucket_type = BUCKET_TYPE(bucket_info);
308 int bucket_size;
309
310 if (bucket_type == VALUE_ONLY_BUCKET_TYPE) {
311 bucket_size = 1;
312 } else {
313 bucket_size = (BUCKET_OFFSET(_buckets[i + 1]) - BUCKET_OFFSET(bucket_info)) / 2;
314 }
315 total_entries += bucket_size;
316 if (max_bucket < bucket_size) {
317 max_bucket = bucket_size;
318 }
319 }
320 st->print_cr("Number of buckets : %9d", _bucket_count);
321 st->print_cr("Number of entries : %9d", total_entries);
322 st->print_cr("Maximum bucket size : %9d", max_bucket);
323 }
324 };
325
326 ////////////////////////////////////////////////////////////////////////
327 //
328 // OffsetCompactHashtable -- This is used to store many types of objects
329 // in the CDS archive. On 64-bit platforms, we save space by using a 32-bit
330 // offset from the CDS base address.
331
332 template <typename V>
333 inline V read_value_from_compact_hashtable(address base_address, u4 offset) {
334 return (V)(base_address + offset);
335 }
336
337 template <
338 typename K,
339 typename V,
340 bool (*EQUALS)(V value, K key, int len)
341 >
342 class OffsetCompactHashtable : public CompactHashtable<
343 K, V, read_value_from_compact_hashtable<V>, EQUALS> {
344 };
345
346
347 ////////////////////////////////////////////////////////////////////////
348 //
349 // Read/Write the contents of a hashtable textual dump (created by
350 // SymbolTable::dump and StringTable::dump).
351 // Because the dump file may be big (hundred of MB in extreme cases),
352 // we use mmap for fast access when reading it.
353 //
354 class HashtableTextDump {
355 int _fd;
356 const char* _base;
357 const char* _p;
358 const char* _end;
359 const char* _filename;
360 size_t _size;
361 int _prefix_type;
362 int _line_no;
363 public:
364 HashtableTextDump(const char* filename);
365 ~HashtableTextDump();
366
367 enum {
368 SymbolPrefix = 1 << 0,
369 StringPrefix = 1 << 1,
370 Unknown = 1 << 2
371 };
372
373 void quit(const char* err, const char* msg);
374
375 inline int remain() {
376 return (int)(_end - _p);
377 }
378
379 void corrupted(const char *p, const char *msg);
380
381 inline void corrupted_if(bool cond, const char *msg) {
382 if (cond) {
383 corrupted(_p, msg);
384 }
385 }
386
387 bool skip_newline();
388 int skip(char must_be_char);
389 void skip_past(char c);
390 void check_version(const char* ver);
391
392 inline void get_num(char delim, int *num) {
393 const char* p = _p;
394 const char* end = _end;
395 u8 n = 0;
396
397 while (p < end) {
398 char c = *p++;
399 if ('0' <= c && c <= '9') {
400 n = n * 10 + (c - '0');
401 if (n > (u8)INT_MAX) {
402 corrupted(_p, "Num overflow");
403 }
404 } else if (c == delim) {
405 _p = p;
406 *num = (int)n;
407 return;
408 } else {
409 // Not [0-9], not 'delim'
410 corrupted(_p, "Unrecognized format");;
411 }
412 }
413
414 corrupted(_end, "Incorrect format");
415 ShouldNotReachHere();
416 }
417
418 void scan_prefix_type();
419 int scan_prefix(int* utf8_length);
420 int scan_string_prefix();
421 int scan_symbol_prefix();
422
423 jchar unescape(const char* from, const char* end, int count);
424 void get_utf8(char* utf8_buffer, int utf8_length);
425 static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length);
426 };
427
428 #endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP