Fri, 23 Mar 2012 11:16:05 -0400
7150058: Allocate symbols from null boot loader to an arena for NMT
Summary: Move symbol allocation to an arena so NMT doesn't have to track them at startup.
Reviewed-by: never, kamg, zgu
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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).
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23 */
25 #ifndef SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
26 #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
28 #include "memory/allocation.inline.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
32 // The symbol table holds all Symbol*s and corresponding interned strings.
33 // Symbol*s and literal strings should be canonicalized.
34 //
35 // The interned strings are created lazily.
36 //
37 // It is implemented as an open hash table with a fixed number of buckets.
38 //
39 // %note:
40 // - symbolTableEntrys are allocated in blocks to reduce the space overhead.
42 class BoolObjectClosure;
45 // Class to hold a newly created or referenced Symbol* temporarily in scope.
46 // new_symbol() and lookup() will create a Symbol* if not already in the
47 // symbol table and add to the symbol's reference count.
48 // probe() and lookup_only() will increment the refcount if symbol is found.
49 class TempNewSymbol : public StackObj {
50 Symbol* _temp;
52 public:
53 TempNewSymbol() : _temp(NULL) {}
54 // Creating or looking up a symbol increments the symbol's reference count
55 TempNewSymbol(Symbol *s) : _temp(s) {}
57 // Operator= increments reference count.
58 void operator=(const TempNewSymbol &s) {
59 _temp = s._temp;
60 if (_temp !=NULL) _temp->increment_refcount();
61 }
63 // Decrement reference counter so it can go away if it's unique
64 ~TempNewSymbol() { if (_temp != NULL) _temp->decrement_refcount(); }
66 // Operators so they can be used like Symbols
67 Symbol* operator -> () const { return _temp; }
68 bool operator == (Symbol* o) const { return _temp == o; }
69 // Sneaky conversion function
70 operator Symbol*() { return _temp; }
71 };
73 class SymbolTable : public Hashtable<Symbol*> {
74 friend class VMStructs;
75 friend class ClassFileParser;
77 private:
78 // The symbol table
79 static SymbolTable* _the_table;
81 // For statistics
82 static int symbols_removed;
83 static int symbols_counted;
85 Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
87 // Adding elements
88 Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
89 bool c_heap, TRAPS);
91 bool basic_add(Handle class_loader, constantPoolHandle cp, int names_count,
92 const char** names, int* lengths, int* cp_indices,
93 unsigned int* hashValues, TRAPS);
95 static void new_symbols(Handle class_loader, constantPoolHandle cp,
96 int names_count,
97 const char** name, int* lengths,
98 int* cp_indices, unsigned int* hashValues,
99 TRAPS) {
100 add(class_loader, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
101 }
103 // Table size
104 enum {
105 symbol_table_size = 20011
106 };
108 Symbol* lookup(int index, const char* name, int len, unsigned int hash);
110 SymbolTable()
111 : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>)) {}
113 SymbolTable(HashtableBucket* t, int number_of_entries)
114 : Hashtable<Symbol*>(symbol_table_size, sizeof (HashtableEntry<Symbol*>), t,
115 number_of_entries) {}
117 // Arena for permanent symbols (null class loader) that are never unloaded
118 static Arena* _arena;
119 static Arena* arena() { return _arena; } // called for statistics
121 static void initialize_symbols(int arena_alloc_size = 0);
122 public:
123 enum {
124 symbol_alloc_batch_size = 8,
125 // Pick initial size based on java -version size measurements
126 symbol_alloc_arena_size = 360*K
127 };
129 // The symbol table
130 static SymbolTable* the_table() { return _the_table; }
132 static void create_table() {
133 assert(_the_table == NULL, "One symbol table allowed.");
134 _the_table = new SymbolTable();
135 initialize_symbols(symbol_alloc_arena_size);
136 }
138 static void create_table(HashtableBucket* t, int length,
139 int number_of_entries) {
140 assert(_the_table == NULL, "One symbol table allowed.");
141 assert(length == symbol_table_size * sizeof(HashtableBucket),
142 "bad shared symbol size.");
143 _the_table = new SymbolTable(t, number_of_entries);
144 // if CDS give symbol table a default arena size since most symbols
145 // are already allocated in the shared misc section.
146 initialize_symbols();
147 }
149 static Symbol* lookup(const char* name, int len, TRAPS);
150 // lookup only, won't add. Also calculate hash.
151 static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
152 // Only copy to C string to be added if lookup failed.
153 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
155 static void release(Symbol* sym);
157 // Look up the address of the literal in the SymbolTable for this Symbol*
158 static Symbol** lookup_symbol_addr(Symbol* sym);
160 // jchar (utf16) version of lookups
161 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
162 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
164 static void add(Handle class_loader, constantPoolHandle cp, int names_count,
165 const char** names, int* lengths, int* cp_indices,
166 unsigned int* hashValues, TRAPS);
168 // Release any dead symbols
169 static void unlink();
171 // iterate over symbols
172 static void symbols_do(SymbolClosure *cl);
174 // Symbol creation
175 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
176 assert(utf8_buffer != NULL, "just checking");
177 return lookup(utf8_buffer, length, THREAD);
178 }
179 static Symbol* new_symbol(const char* name, TRAPS) {
180 return new_symbol(name, (int)strlen(name), THREAD);
181 }
182 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
183 assert(begin <= end && end <= sym->utf8_length(), "just checking");
184 return lookup(sym, begin, end, THREAD);
185 }
187 // Create a symbol in the arena for symbols that are not deleted
188 static Symbol* new_permanent_symbol(const char* name, TRAPS);
190 // Symbol lookup
191 static Symbol* lookup(int index, const char* name, int len, TRAPS);
193 // Needed for preloading classes in signatures when compiling.
194 // Returns the symbol is already present in symbol table, otherwise
195 // NULL. NO ALLOCATION IS GUARANTEED!
196 static Symbol* probe(const char* name, int len) {
197 unsigned int ignore_hash;
198 return lookup_only(name, len, ignore_hash);
199 }
200 static Symbol* probe_unicode(const jchar* name, int len) {
201 unsigned int ignore_hash;
202 return lookup_only_unicode(name, len, ignore_hash);
203 }
205 // Histogram
206 static void print_histogram() PRODUCT_RETURN;
207 static void print() PRODUCT_RETURN;
209 // Debugging
210 static void verify();
212 // Sharing
213 static void copy_buckets(char** top, char*end) {
214 the_table()->Hashtable<Symbol*>::copy_buckets(top, end);
215 }
216 static void copy_table(char** top, char*end) {
217 the_table()->Hashtable<Symbol*>::copy_table(top, end);
218 }
219 static void reverse(void* boundary = NULL) {
220 the_table()->Hashtable<Symbol*>::reverse(boundary);
221 }
222 };
224 class StringTable : public Hashtable<oop> {
225 friend class VMStructs;
227 private:
228 // The string table
229 static StringTable* _the_table;
231 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
232 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
233 unsigned int hashValue, TRAPS);
235 oop lookup(int index, jchar* chars, int length, unsigned int hashValue);
237 StringTable() : Hashtable<oop>((int)StringTableSize,
238 sizeof (HashtableEntry<oop>)) {}
240 StringTable(HashtableBucket* t, int number_of_entries)
241 : Hashtable<oop>((int)StringTableSize, sizeof (HashtableEntry<oop>), t,
242 number_of_entries) {}
244 public:
245 // The string table
246 static StringTable* the_table() { return _the_table; }
248 static void create_table() {
249 assert(_the_table == NULL, "One string table allowed.");
250 _the_table = new StringTable();
251 }
253 static void create_table(HashtableBucket* t, int length,
254 int number_of_entries) {
255 assert(_the_table == NULL, "One string table allowed.");
256 assert((size_t)length == StringTableSize * sizeof(HashtableBucket),
257 "bad shared string size.");
258 _the_table = new StringTable(t, number_of_entries);
259 }
261 // GC support
262 // Delete pointers to otherwise-unreachable objects.
263 static void unlink(BoolObjectClosure* cl);
265 // Invoke "f->do_oop" on the locations of all oops in the table.
266 static void oops_do(OopClosure* f);
268 // Probing
269 static oop lookup(Symbol* symbol);
271 // Interning
272 static oop intern(Symbol* symbol, TRAPS);
273 static oop intern(oop string, TRAPS);
274 static oop intern(const char *utf8_string, TRAPS);
276 // Debugging
277 static void verify();
279 // Sharing
280 static void copy_buckets(char** top, char*end) {
281 the_table()->Hashtable<oop>::copy_buckets(top, end);
282 }
283 static void copy_table(char** top, char*end) {
284 the_table()->Hashtable<oop>::copy_table(top, end);
285 }
286 static void reverse() {
287 the_table()->Hashtable<oop>::reverse();
288 }
289 };
291 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP