1 /*
2 * Copyright (c) 2003, 2019, 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 #include "precompiled.hpp"
26 #include "classfile/altHashing.hpp"
27 #include "classfile/dictionary.hpp"
28 #include "classfile/javaClasses.inline.hpp"
29 #include "classfile/moduleEntry.hpp"
30 #include "classfile/packageEntry.hpp"
31 #include "classfile/placeholders.hpp"
32 #include "classfile/protectionDomainCache.hpp"
33 #include "classfile/stringTable.hpp"
34 #include "code/nmethod.hpp"
35 #include "logging/log.hpp"
36 #include "memory/allocation.inline.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/weakHandle.inline.hpp"
40 #include "runtime/safepoint.hpp"
41 #include "utilities/dtrace.hpp"
42 #include "utilities/hashtable.hpp"
43 #include "utilities/hashtable.inline.hpp"
44 #include "utilities/numberSeq.hpp"
45
46
47 // This hashtable is implemented as an open hash table with a fixed number of buckets.
48
49 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
50 BasicHashtableEntry<F>* entry = NULL;
51 if (_free_list != NULL) {
52 entry = _free_list;
53 _free_list = _free_list->next();
54 }
55 return entry;
56 }
57
58 // HashtableEntrys are allocated in blocks to reduce the space overhead.
59 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
60 BasicHashtableEntry<F>* entry = new_entry_free_list();
61
62 if (entry == NULL) {
63 if (_first_free_entry + _entry_size >= _end_block) {
64 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
65 int len = _entry_size * block_size;
66 len = 1 << log2_int(len); // round down to power of 2
67 assert(len >= _entry_size, "");
68 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);
69 _entry_blocks->append(_first_free_entry);
70 _end_block = _first_free_entry + len;
71 }
72 entry = (BasicHashtableEntry<F>*)_first_free_entry;
73 _first_free_entry += _entry_size;
74 }
75
76 assert(_entry_size % HeapWordSize == 0, "");
77 entry->set_hash(hashValue);
78 return entry;
79 }
80
81
82 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {
83 HashtableEntry<T, F>* entry;
84
85 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);
86 entry->set_literal(obj);
87 return entry;
88 }
89
90 // Version of hashtable entry allocation that allocates in the C heap directly.
91 // The block allocator in BasicHashtable has less fragmentation, but the memory is not freed until
92 // the whole table is freed. Use allocate_new_entry() if you want to individually free the memory
93 // used by each entry
94 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) {
95 HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F);
96
97 entry->set_hash(hashValue);
98 entry->set_literal(obj);
99 entry->set_next(NULL);
100 return entry;
101 }
102
103 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
104 if (NULL != _buckets) {
105 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
106 _buckets = NULL;
107 }
108 }
109
110 // For oops and Strings the size of the literal is interesting. For other types, nobody cares.
111 static int literal_size(ConstantPool*) { return 0; }
112 static int literal_size(Klass*) { return 0; }
113 static int literal_size(nmethod*) { return 0; }
114
115 static int literal_size(Symbol *symbol) {
116 return symbol->size() * HeapWordSize;
117 }
118
119 static int literal_size(oop obj) {
120 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
121 // and the String.value array is shared by several Strings. However, starting from JDK8,
122 // the String.value array is not shared anymore.
123 if (obj == NULL) {
124 return 0;
125 } else if (obj->klass() == SystemDictionary::String_klass()) {
126 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;
127 } else {
128 return obj->size();
129 }
130 }
131
132 static int literal_size(WeakHandle<vm_class_loader_data> v) {
133 return literal_size(v.peek());
134 }
135
136 template <MEMFLAGS F> bool BasicHashtable<F>::resize(int new_size) {
137 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
138
139 // Allocate new buckets
140 HashtableBucket<F>* buckets_new = NEW_C_HEAP_ARRAY2_RETURN_NULL(HashtableBucket<F>, new_size, F, CURRENT_PC);
141 if (buckets_new == NULL) {
142 return false;
143 }
144
145 // Clear the new buckets
146 for (int i = 0; i < new_size; i++) {
147 buckets_new[i].clear();
148 }
149
150 int table_size_old = _table_size;
151 // hash_to_index() uses _table_size, so switch the sizes now
152 _table_size = new_size;
153
154 // Move entries from the old table to a new table
155 for (int index_old = 0; index_old < table_size_old; index_old++) {
156 for (BasicHashtableEntry<F>* p = _buckets[index_old].get_entry(); p != NULL; ) {
157 BasicHashtableEntry<F>* next = p->next();
158 bool keep_shared = p->is_shared();
159 int index_new = hash_to_index(p->hash());
160
161 p->set_next(buckets_new[index_new].get_entry());
162 buckets_new[index_new].set_entry(p);
163
164 if (keep_shared) {
165 p->set_shared();
166 }
167 p = next;
168 }
169 }
170
171 // The old backets now can be released
172 BasicHashtable<F>::free_buckets();
173
174 // Switch to the new storage
175 _buckets = buckets_new;
176
177 return true;
178 }
179
180 template <MEMFLAGS F> bool BasicHashtable<F>::maybe_grow(int max_size, int load_factor) {
181 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
182
183 if (table_size() >= max_size) {
184 return false;
185 }
186 if (number_of_entries() / table_size() > load_factor) {
187 resize(MIN2<int>(table_size() * 2, max_size));
188 return true;
189 } else {
190 return false;
191 }
192 }
193
194 // Dump footprint and bucket length statistics
195 //
196 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
197 // add a new function static int literal_size(MyNewType lit)
198 // because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop.
199 //
200 // The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol
201 // literals.
202
203 template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st,
204 const char *table_name,
205 T (*literal_load_barrier)(HashtableEntry<T, F>*)) {
206 NumberSeq summary;
207 int literal_bytes = 0;
208 for (int i = 0; i < this->table_size(); ++i) {
209 int count = 0;
210 for (HashtableEntry<T, F>* e = this->bucket(i);
211 e != NULL; e = e->next()) {
212 count++;
213 T l = (literal_load_barrier != NULL) ? literal_load_barrier(e) : e->literal();
214 literal_bytes += literal_size(l);
215 }
216 summary.add((double)count);
217 }
218 double num_buckets = summary.num();
219 double num_entries = summary.sum();
220
221 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
222 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
223 int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
224
225 int bucket_size = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets);
226 int entry_size = (num_entries <= 0) ? 0 : (entry_bytes / num_entries);
227
228 st->print_cr("%s statistics:", table_name);
229 st->print_cr("Number of buckets : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes, bucket_size);
230 st->print_cr("Number of entries : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes, entry_size);
231 if (literal_bytes != 0) {
232 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
233 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
234 }
235 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes);
236 st->print_cr("Average bucket size : %9.3f", summary.avg());
237 st->print_cr("Variance of bucket size : %9.3f", summary.variance());
238 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
239 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum());
240 }
241
242 #ifndef PRODUCT
243 template <class T> void print_literal(T l) {
244 l->print();
245 }
246
247 static void print_literal(WeakHandle<vm_class_loader_data> l) {
248 l.print();
249 }
250
251 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
252 ResourceMark rm;
253
254 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
255 HashtableEntry<T, F>* entry = bucket(i);
256 while(entry != NULL) {
257 tty->print("%d : ", i);
258 print_literal(entry->literal());
259 tty->cr();
260 entry = entry->next();
261 }
262 }
263 }
264
265 template <MEMFLAGS F>
266 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
267 int element_count = 0;
268 int max_bucket_count = 0;
269 int max_bucket_number = 0;
270 for (int index = 0; index < table_size(); index++) {
271 int bucket_count = 0;
272 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
273 probe->verify();
274 bucket_count++;
275 }
276 element_count += bucket_count;
277 if (bucket_count > max_bucket_count) {
278 max_bucket_count = bucket_count;
279 max_bucket_number = index;
280 }
281 }
282 guarantee(number_of_entries() == element_count,
283 "Verify of %s failed", table_name);
284
285 // Log some statistics about the hashtable
286 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
287 max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
288 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
289 for (int index = 0; index < table_size(); index++) {
290 int bucket_count = 0;
291 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
292 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
293 bucket_count++;
294 }
295 if (bucket_count > 0) {
296 log_debug(hashtables)("bucket %d count %d", index, bucket_count);
297 }
298 }
299 }
300 }
301 #endif // PRODUCT
302
303 // Explicitly instantiate these types
304 template class Hashtable<nmethod*, mtGC>;
305 template class HashtableEntry<nmethod*, mtGC>;
306 template class BasicHashtable<mtGC>;
307 template class Hashtable<ConstantPool*, mtClass>;
308 template class Hashtable<Symbol*, mtSymbol>;
309 template class Hashtable<Klass*, mtClass>;
310 template class Hashtable<InstanceKlass*, mtClass>;
311 template class Hashtable<WeakHandle<vm_class_loader_data>, mtClass>;
312 template class Hashtable<Symbol*, mtModule>;
313 template class Hashtable<oop, mtSymbol>;
314 template class Hashtable<Symbol*, mtClass>;
315 template class HashtableEntry<Symbol*, mtSymbol>;
316 template class HashtableEntry<Symbol*, mtClass>;
317 template class HashtableEntry<oop, mtSymbol>;
318 template class HashtableEntry<WeakHandle<vm_class_loader_data>, mtClass>;
319 template class HashtableBucket<mtClass>;
320 template class BasicHashtableEntry<mtSymbol>;
321 template class BasicHashtableEntry<mtCode>;
322 template class BasicHashtable<mtClass>;
323 template class BasicHashtable<mtClassShared>;
324 template class BasicHashtable<mtSymbol>;
325 template class BasicHashtable<mtCode>;
326 template class BasicHashtable<mtInternal>;
327 template class BasicHashtable<mtModule>;
328 template class BasicHashtable<mtCompiler>;
329
330 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
331 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
332 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
333 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
334 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);