1 /*
2 * Copyright (c) 1997, 2014, 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 "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "oops/symbol.hpp"
32 #include "services/diagnosticCommand.hpp"
33 #include "utilities/hashtable.hpp"
34
35 class NumberSeq;
36
37 // Stats for symbol tables in the CDS archive
38 class CompactHashtableStats VALUE_OBJ_CLASS_SPEC {
39 public:
40 int hashentry_count;
41 int hashentry_bytes;
42 int bucket_count;
43 int bucket_bytes;
44 };
45
46 /////////////////////////////////////////////////////////////////////////
47 //
48 // The compact hash table writer. Used at dump time for writing out
49 // the compact table to the shared archive.
50 //
51 // At dump time, the CompactHashtableWriter obtains all entries from the
52 // symbol table and adds them to a new temporary hash table. The hash
53 // table size (number of buckets) is calculated using
54 // '(num_entries + bucket_size - 1) / bucket_size'. The default bucket
55 // size is 4 and can be changed by -XX:SharedSymbolTableBucketSize option.
56 // 4 is chosen because it produces smaller sized bucket on average for
57 // faster lookup. It also has relatively small number of empty buckets and
58 // good distribution of the entries.
59 //
60 // We use a simple hash function (symbol_hash % num_bucket) for the table.
61 // The new table is compacted when written out. Please see comments
62 // above the CompactHashtable class for the table layout detail. The bucket
63 // offsets are written to the archive as part of the compact table. The
64 // bucket offset is encoded in the low 30-bit (0-29) and the bucket type
65 // (regular or compact) are encoded in bit[31, 30]. For buckets with more
66 // than one entry, both symbol hash and symbol offset are written to the
67 // table. For buckets with only one entry, only the symbol offset is written
68 // to the table and the buckets are tagged as compact in their type bits.
69 // Buckets without entry are skipped from the table. Their offsets are
70 // still written out for faster lookup.
71 //
72 class CompactHashtableWriter: public StackObj {
73 public:
74 class Entry: public CHeapObj<mtSymbol> {
75 Entry* _next;
76 unsigned int _hash;
77 void* _literal;
78
79 public:
80 Entry(unsigned int hash, Symbol *symbol) : _next(NULL), _hash(hash), _literal(symbol) {}
81
82 void *value() {
83 return _literal;
84 }
85 Symbol *symbol() {
86 return (Symbol*)_literal;
87 }
88 unsigned int hash() {
89 return _hash;
90 }
91 Entry *next() {return _next;}
92 void set_next(Entry *p) {_next = p;}
93 }; // class CompactHashtableWriter::Entry
94
95 private:
96 static int number_of_buckets(int num_entries);
97
98 const char* _table_name;
99 int _num_entries;
100 int _num_buckets;
101 juint* _bucket_sizes;
102 Entry** _buckets;
103 int _required_bytes;
104 CompactHashtableStats* _stats;
105
106 public:
107 // This is called at dump-time only
108 CompactHashtableWriter(const char* table_name, int num_entries, CompactHashtableStats* stats);
109 ~CompactHashtableWriter();
110
111 int get_required_bytes() {
112 return _required_bytes;
113 }
114
115 void add(unsigned int hash, Symbol* symbol) {
116 add(hash, new Entry(hash, symbol));
117 }
118
119 private:
120 void add(unsigned int hash, Entry* entry);
121 juint* dump_table(juint* p, juint** first_bucket, NumberSeq* summary);
122 juint* dump_buckets(juint* table, juint* p, NumberSeq* summary);
123
124 public:
125 void dump(char** top, char* end);
126 };
127
128 #define REGULAR_BUCKET_TYPE 0
129 #define COMPACT_BUCKET_TYPE 1
130 #define TABLEEND_BUCKET_TYPE 3
131 #define BUCKET_OFFSET_MASK 0x3FFFFFFF
132 #define BUCKET_OFFSET(info) ((info) & BUCKET_OFFSET_MASK)
133 #define BUCKET_TYPE_SHIFT 30
134 #define BUCKET_TYPE(info) (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT)
135 #define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK))
136
137 /////////////////////////////////////////////////////////////////////////////
138 //
139 // CompactHashtable is used to stored the CDS archive's symbol table. Used
140 // at runtime only to access the compact table from the archive.
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 // Layout of compact symbol table in the shared archive:
147 //
148 // uintx base_address;
149 // juint num_symbols;
150 // juint num_buckets;
151 // juint bucket_infos[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset
152 // juint table[]
153 //
154 // -----------------------------------
155 // | base_address | num_symbols |
156 // |---------------------------------|
157 // | num_buckets | bucket_info0 |
158 // |---------------------------------|
159 // | bucket_info1 | bucket_info2 |
160 // | bucket_info3 ... |
161 // | .... | table_end_info |
162 // |---------------------------------|
163 // | entry0 |
164 // | entry1 |
165 // | entry2 |
166 // | |
167 // | ... |
168 // -----------------------------------
169 //
170 // The size of the bucket_info table is 'num_buckets + 1'. Each entry of the
171 // bucket_info table is a 32-bit encoding of the bucket type and bucket offset,
172 // with the type in the left-most 2-bit and offset in the remaining 30-bit.
173 // The last entry is a special type. It contains the offset of the last
174 // bucket end. We use that information when traversing the compact table.
175 //
176 // There are two types of buckets, regular buckets and compact buckets. The
177 // compact buckets have '01' in their highest 2-bit, and regular buckets have
178 // '00' in their highest 2-bit.
179 //
180 // For normal buckets, each symbol's entry is 8 bytes in the table[]:
181 // juint hash; /* symbol hash */
182 // juint offset; /* Symbol* sym = (Symbol*)(base_address + offset) */
183 //
184 // For compact buckets, each entry has only the 4-byte 'offset' in the table[].
185 //
186 // See CompactHashtable::lookup() for how the table is searched at runtime.
187 // See CompactHashtableWriter::dump() for how the table is written at CDS
188 // dump time.
189 //
190 template <class T, class N> class CompactHashtable VALUE_OBJ_CLASS_SPEC {
191 uintx _base_address;
192 juint _entry_count;
193 juint _bucket_count;
194 juint _table_end_offset;
195 juint* _buckets;
196
197 inline bool equals(T entry, const char* name, int len) {
198 if (entry->equals(name, len)) {
199 assert(entry->refcount() == -1, "must be shared");
200 return true;
201 } else {
202 return false;
203 }
204 }
205
206 public:
207 CompactHashtable() {
208 _entry_count = 0;
209 _bucket_count = 0;
210 _table_end_offset = 0;
211 _buckets = 0;
212 }
213 const char* init(const char *buffer);
214
215 // Lookup an entry from the compact table
216 inline T lookup(const N* name, unsigned int hash, int len) {
217 if (_entry_count > 0) {
218 assert(!DumpSharedSpaces, "run-time only");
219 int index = hash % _bucket_count;
220 juint bucket_info = _buckets[index];
221 juint bucket_offset = BUCKET_OFFSET(bucket_info);
222 int bucket_type = BUCKET_TYPE(bucket_info);
223 juint* bucket = _buckets + bucket_offset;
224 juint* bucket_end = _buckets;
225
226 if (bucket_type == COMPACT_BUCKET_TYPE) {
227 // the compact bucket has one entry with symbol offset only
228 T entry = (T)((void*)(_base_address + bucket[0]));
229 if (equals(entry, name, len)) {
230 return entry;
231 }
232 } else {
233 // This is a regular bucket, which has more than one
234 // entries. Each entry is a pair of symbol (hash, offset).
235 // Seek until the end of the bucket.
236 bucket_end += BUCKET_OFFSET(_buckets[index + 1]);
237 while (bucket < bucket_end) {
238 unsigned int h = (unsigned int)(bucket[0]);
239 if (h == hash) {
240 juint offset = bucket[1];
241 T entry = (T)((void*)(_base_address + offset));
242 if (equals(entry, name, len)) {
243 return entry;
244 }
245 }
246 bucket += 2;
247 }
248 }
249 }
250 return NULL;
251 }
252
253 // iterate over symbols
254 void symbols_do(SymbolClosure *cl);
255 };
256
257 ////////////////////////////////////////////////////////////////////////
258 //
259 // Read/Write the contents of a hashtable textual dump (created by
260 // SymbolTable::dump).
261 // Because the dump file may be big (hundred of MB in extreme cases),
262 // we use mmap for fast access when reading it.
263 //
264 class HashtableTextDump VALUE_OBJ_CLASS_SPEC {
265 int _fd;
266 const char* _base;
267 const char* _p;
268 const char* _end;
269 const char* _filename;
270 size_t _size;
271 public:
272 HashtableTextDump(const char* filename);
273 ~HashtableTextDump();
274
275 void quit(const char* err, const char* msg);
276
277 inline int remain() {
278 return (int)(_end - _p);
279 }
280
281 void corrupted(const char *p);
282
283 inline void corrupted_if(bool cond) {
284 if (cond) {
285 corrupted(_p);
286 }
287 }
288
289 bool skip_newline();
290 int skip(char must_be_char);
291 void skip_past(char c);
292 void check_version(const char* ver);
293
294 inline int get_num(char delim) {
295 const char* p = _p;
296 const char* end = _end;
297 int num = 0;
298
299 while (p < end) {
300 char c = *p ++;
301 if ('0' <= c && c <= '9') {
302 num = num * 10 + (c - '0');
303 } else if (c == delim) {
304 _p = p;
305 return num;
306 } else {
307 corrupted(p-1);
308 }
309 }
310 corrupted(_end);
311 ShouldNotReachHere();
312 return 0;
313 }
314
315 int scan_prefix();
316 int scan_prefix2();
317
318 jchar unescape(const char* from, const char* end, int count);
319 void get_utf8(char* utf8_buffer, int utf8_length);
320 static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length);
321 };
322
323 ///////////////////////////////////////////////////////////////////////
324 //
325 // jcmd command support for symbol table and string table dumping:
326 // VM.symboltable -verbose: for dumping the symbol table
327 // VM.stringtable -verbose: for dumping the string table
328 //
329 class VM_DumpHashtable : public VM_Operation {
330 private:
331 outputStream* _out;
332 int _which;
333 bool _verbose;
334 public:
335 enum {
336 DumpSymbols = 1 << 0,
337 DumpStrings = 1 << 1,
338 DumpSysDict = 1 << 2 // not implemented yet
339 };
340 VM_DumpHashtable(outputStream* out, int which, bool verbose) {
341 _out = out;
342 _which = which;
343 _verbose = verbose;
344 }
345
346 virtual VMOp_Type type() const { return VMOp_DumpHashtable; }
347
348 virtual void doit() {
349 switch (_which) {
350 case DumpSymbols:
351 SymbolTable::dump(_out, _verbose);
352 break;
353 case DumpStrings:
354 StringTable::dump(_out, _verbose);
355 break;
356 default:
357 ShouldNotReachHere();
358 }
359 }
360 };
361
362 class SymboltableDCmd : public DCmdWithParser {
363 protected:
364 DCmdArgument<bool> _verbose;
365 public:
366 SymboltableDCmd(outputStream* output, bool heap);
367 static const char* name() {
368 return "VM.symboltable";
369 }
370 static const char* description() {
371 return "Dump symbol table.";
372 }
373 static const char* impact() {
374 return "Medium: Depends on Java content.";
375 }
376 static const JavaPermission permission() {
377 JavaPermission p = {"java.lang.management.ManagementPermission",
378 "monitor", NULL};
379 return p;
380 }
381 static int num_arguments();
382 virtual void execute(DCmdSource source, TRAPS);
383 };
384
385 class StringtableDCmd : public DCmdWithParser {
386 protected:
387 DCmdArgument<bool> _verbose;
388 public:
389 StringtableDCmd(outputStream* output, bool heap);
390 static const char* name() {
391 return "VM.stringtable";
392 }
393 static const char* description() {
394 return "Dump string table.";
395 }
396 static const char* impact() {
397 return "Medium: Depends on Java content.";
398 }
399 static const JavaPermission permission() {
400 JavaPermission p = {"java.lang.management.ManagementPermission",
401 "monitor", NULL};
402 return p;
403 }
404 static int num_arguments();
405 virtual void execute(DCmdSource source, TRAPS);
406 };
407
408 #endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP