1 /*
2 * Copyright (c) 2003, 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 #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 "logging/log.hpp"
35 #include "memory/allocation.inline.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/weakHandle.inline.hpp"
39 #include "runtime/safepoint.hpp"
40 #include "utilities/dtrace.hpp"
41 #include "utilities/hashtable.hpp"
42 #include "utilities/hashtable.inline.hpp"
43 #include "utilities/numberSeq.hpp"
44
45
46 // This hashtable is implemented as an open hash table with a fixed number of buckets.
47
48 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
49 BasicHashtableEntry<F>* entry = NULL;
50 if (_free_list != NULL) {
51 entry = _free_list;
52 _free_list = _free_list->next();
53 }
54 return entry;
55 }
56
57 // HashtableEntrys are allocated in blocks to reduce the space overhead.
58 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
59 BasicHashtableEntry<F>* entry = new_entry_free_list();
60
61 if (entry == NULL) {
62 if (_first_free_entry + _entry_size >= _end_block) {
63 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
64 int len = _entry_size * block_size;
65 len = 1 << log2_intptr(len); // round down to power of 2
66 assert(len >= _entry_size, "");
67 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);
68 _entry_blocks->append(_first_free_entry);
69 _end_block = _first_free_entry + len;
70 }
71 entry = (BasicHashtableEntry<F>*)_first_free_entry;
72 _first_free_entry += _entry_size;
73 }
74
75 assert(_entry_size % HeapWordSize == 0, "");
76 entry->set_hash(hashValue);
77 return entry;
78 }
79
80
81 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {
82 HashtableEntry<T, F>* entry;
83
84 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);
85 entry->set_literal(obj);
86 return entry;
87 }
88
89 // Version of hashtable entry allocation that allocates in the C heap directly.
90 // The allocator in blocks is preferable but doesn't have free semantics.
91 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) {
92 HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F);
93
94 entry->set_hash(hashValue);
95 entry->set_literal(obj);
96 entry->set_next(NULL);
97 return entry;
98 }
99
100 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
101 if (NULL != _buckets) {
102 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
103 _buckets = NULL;
104 }
105 }
106
107 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) {
108 entry->set_next(_removed_head);
109 _removed_head = entry;
110 if (_removed_tail == NULL) {
111 _removed_tail = entry;
112 }
113 _num_removed++;
114 }
115
116 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) {
117 if (context->_num_removed == 0) {
118 assert(context->_removed_head == NULL && context->_removed_tail == NULL,
119 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT,
120 p2i(context->_removed_head), p2i(context->_removed_tail));
121 return;
122 }
123
124 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list.
125 BasicHashtableEntry<F>* current = _free_list;
126 while (true) {
127 context->_removed_tail->set_next(current);
128 BasicHashtableEntry<F>* old = Atomic::cmpxchg(context->_removed_head, &_free_list, current);
129 if (old == current) {
130 break;
131 }
132 current = old;
133 }
134 Atomic::add(-context->_num_removed, &_number_of_entries);
135 }
136
137 // For oops and Strings the size of the literal is interesting. For other types, nobody cares.
138 static int literal_size(ConstantPool*) { return 0; }
139 static int literal_size(Klass*) { return 0; }
140 static int literal_size(nmethod*) { return 0; }
141
142 static int literal_size(Symbol *symbol) {
143 return symbol->size() * HeapWordSize;
144 }
145
146 static int literal_size(oop obj) {
147 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
148 // and the String.value array is shared by several Strings. However, starting from JDK8,
149 // the String.value array is not shared anymore.
150 if (obj == NULL) {
151 return 0;
152 } else if (obj->klass() == SystemDictionary::String_klass()) {
153 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;
154 } else {
155 return obj->size();
156 }
157 }
158
159 static int literal_size(ClassLoaderWeakHandle v) {
160 return literal_size(v.peek());
161 }
162
163 template <MEMFLAGS F> bool BasicHashtable<F>::resize(int new_size) {
164 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
165
166 // Allocate new buckets
167 HashtableBucket<F>* buckets_new = NEW_C_HEAP_ARRAY2_RETURN_NULL(HashtableBucket<F>, new_size, F, CURRENT_PC);
168 if (buckets_new == NULL) {
169 return false;
170 }
171
172 // Clear the new buckets
173 for (int i = 0; i < new_size; i++) {
174 buckets_new[i].clear();
175 }
176
177 int table_size_old = _table_size;
178 // hash_to_index() uses _table_size, so switch the sizes now
179 _table_size = new_size;
180
181 // Move entries from the old table to a new table
182 for (int index_old = 0; index_old < table_size_old; index_old++) {
183 for (BasicHashtableEntry<F>* p = _buckets[index_old].get_entry(); p != NULL; ) {
184 BasicHashtableEntry<F>* next = p->next();
185 bool keep_shared = p->is_shared();
186 int index_new = hash_to_index(p->hash());
187
188 p->set_next(buckets_new[index_new].get_entry());
189 buckets_new[index_new].set_entry(p);
190
191 if (keep_shared) {
192 p->set_shared();
193 }
194 p = next;
195 }
196 }
197
198 // The old backets now can be released
199 BasicHashtable<F>::free_buckets();
200
201 // Switch to the new storage
202 _buckets = buckets_new;
203
204 return true;
205 }
206
207 // Dump footprint and bucket length statistics
208 //
209 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
210 // add a new function static int literal_size(MyNewType lit)
211 // because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop.
212 //
213 // The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol
214 // literals.
215
216 template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st,
217 const char *table_name,
218 T (*literal_load_barrier)(HashtableEntry<T, F>*)) {
219 NumberSeq summary;
220 int literal_bytes = 0;
221 for (int i = 0; i < this->table_size(); ++i) {
222 int count = 0;
223 for (HashtableEntry<T, F>* e = this->bucket(i);
224 e != NULL; e = e->next()) {
225 count++;
226 T l = (literal_load_barrier != NULL) ? literal_load_barrier(e) : e->literal();
227 literal_bytes += literal_size(l);
228 }
229 summary.add((double)count);
230 }
231 double num_buckets = summary.num();
232 double num_entries = summary.sum();
233
234 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
235 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
236 int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
237
238 int bucket_size = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets);
239 int entry_size = (num_entries <= 0) ? 0 : (entry_bytes / num_entries);
240
241 st->print_cr("%s statistics:", table_name);
242 st->print_cr("Number of buckets : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes, bucket_size);
243 st->print_cr("Number of entries : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes, entry_size);
244 if (literal_bytes != 0) {
245 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
246 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
247 }
248 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes);
249 st->print_cr("Average bucket size : %9.3f", summary.avg());
250 st->print_cr("Variance of bucket size : %9.3f", summary.variance());
251 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
252 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum());
253 }
254
255 #ifndef PRODUCT
256 template <class T> void print_literal(T l) {
257 l->print();
258 }
259
260 static void print_literal(ClassLoaderWeakHandle l) {
261 l.print();
262 }
263
264 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
265 ResourceMark rm;
266
267 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
268 HashtableEntry<T, F>* entry = bucket(i);
269 while(entry != NULL) {
270 tty->print("%d : ", i);
271 print_literal(entry->literal());
272 tty->cr();
273 entry = entry->next();
274 }
275 }
276 }
277
278 template <MEMFLAGS F>
279 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
280 int element_count = 0;
281 int max_bucket_count = 0;
282 int max_bucket_number = 0;
283 for (int index = 0; index < table_size(); index++) {
284 int bucket_count = 0;
285 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
286 probe->verify();
287 bucket_count++;
288 }
289 element_count += bucket_count;
290 if (bucket_count > max_bucket_count) {
291 max_bucket_count = bucket_count;
292 max_bucket_number = index;
293 }
294 }
295 guarantee(number_of_entries() == element_count,
296 "Verify of %s failed", table_name);
297
298 // Log some statistics about the hashtable
299 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
300 max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
301 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
302 for (int index = 0; index < table_size(); index++) {
303 int bucket_count = 0;
304 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
305 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
306 bucket_count++;
307 }
308 if (bucket_count > 0) {
309 log_debug(hashtables)("bucket %d count %d", index, bucket_count);
310 }
311 }
312 }
313 }
314 #endif // PRODUCT
315
316 // Explicitly instantiate these types
317 template class Hashtable<nmethod*, mtGC>;
318 template class HashtableEntry<nmethod*, mtGC>;
319 template class BasicHashtable<mtGC>;
320 template class Hashtable<ConstantPool*, mtClass>;
321 template class Hashtable<Symbol*, mtSymbol>;
322 template class Hashtable<Klass*, mtClass>;
323 template class Hashtable<InstanceKlass*, mtClass>;
324 template class Hashtable<ClassLoaderWeakHandle, mtClass>;
325 template class Hashtable<Symbol*, mtModule>;
326 template class Hashtable<oop, mtSymbol>;
327 template class Hashtable<ClassLoaderWeakHandle, mtSymbol>;
328 template class Hashtable<Symbol*, mtClass>;
329 template class HashtableEntry<Symbol*, mtSymbol>;
330 template class HashtableEntry<Symbol*, mtClass>;
331 template class HashtableEntry<oop, mtSymbol>;
332 template class HashtableEntry<ClassLoaderWeakHandle, mtSymbol>;
333 template class HashtableBucket<mtClass>;
334 template class BasicHashtableEntry<mtSymbol>;
335 template class BasicHashtableEntry<mtCode>;
336 template class BasicHashtable<mtClass>;
337 template class BasicHashtable<mtClassShared>;
338 template class BasicHashtable<mtSymbol>;
339 template class BasicHashtable<mtCode>;
340 template class BasicHashtable<mtInternal>;
341 template class BasicHashtable<mtModule>;
342 template class BasicHashtable<mtCompiler>;
343
344 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
345 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
346 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
347 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
348 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);