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