1 /*
2 * Copyright (c) 2003, 2016, 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/javaClasses.inline.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "memory/filemap.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/safepoint.hpp"
34 #include "utilities/dtrace.hpp"
35 #include "utilities/hashtable.hpp"
36 #include "utilities/hashtable.inline.hpp"
37 #include "utilities/numberSeq.hpp"
38
39
40 // This hashtable is implemented as an open hash table with a fixed number of buckets.
41
42 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
43 BasicHashtableEntry<F>* entry = NULL;
44 if (_free_list != NULL) {
45 entry = _free_list;
46 _free_list = _free_list->next();
47 }
48 return entry;
49 }
50
51 // HashtableEntrys are allocated in blocks to reduce the space overhead.
52 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
53 BasicHashtableEntry<F>* entry = new_entry_free_list();
54
55 if (entry == NULL) {
56 if (_first_free_entry + _entry_size >= _end_block) {
57 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
58 int len = _entry_size * block_size;
59 len = 1 << log2_intptr(len); // round down to power of 2
60 assert(len >= _entry_size, "");
61 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);
62 _end_block = _first_free_entry + len;
63 }
64 entry = (BasicHashtableEntry<F>*)_first_free_entry;
65 _first_free_entry += _entry_size;
66 }
67
68 assert(_entry_size % HeapWordSize == 0, "");
69 entry->set_hash(hashValue);
70 return entry;
71 }
72
73
74 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {
75 HashtableEntry<T, F>* entry;
76
77 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);
78 entry->set_literal(obj);
79 return entry;
80 }
81
82 // Check to see if the hashtable is unbalanced. The caller set a flag to
83 // rehash at the next safepoint. If this bucket is 60 times greater than the
84 // expected average bucket length, it's an unbalanced hashtable.
85 // This is somewhat an arbitrary heuristic but if one bucket gets to
86 // rehash_count which is currently 100, there's probably something wrong.
87
88 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {
89 assert(this->table_size() != 0, "underflow");
90 if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {
91 // Set a flag for the next safepoint, which should be at some guaranteed
92 // safepoint interval.
93 return true;
94 }
95 return false;
96 }
97
98 template <class T, MEMFLAGS F> juint RehashableHashtable<T, F>::_seed = 0;
99
100 // Create a new table and using alternate hash code, populate the new table
101 // with the existing elements. This can be used to change the hash code
102 // and could in the future change the size of the table.
103
104 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
105
106 // Initialize the global seed for hashing.
107 _seed = AltHashing::compute_seed();
108 assert(seed() != 0, "shouldn't be zero");
109
110 int saved_entry_count = this->number_of_entries();
111
112 // Iterate through the table and create a new entry for the new table
113 for (int i = 0; i < new_table->table_size(); ++i) {
114 for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
115 HashtableEntry<T, F>* next = p->next();
116 T string = p->literal();
117 // Use alternate hashing algorithm on the symbol in the first table
118 unsigned int hashValue = string->new_hash(seed());
119 // Get a new index relative to the new table (can also change size)
120 int index = new_table->hash_to_index(hashValue);
121 p->set_hash(hashValue);
122 // Keep the shared bit in the Hashtable entry to indicate that this entry
123 // can't be deleted. The shared bit is the LSB in the _next field so
124 // walking the hashtable past these entries requires
125 // BasicHashtableEntry::make_ptr() call.
126 bool keep_shared = p->is_shared();
127 this->unlink_entry(p);
128 new_table->add_entry(index, p);
129 if (keep_shared) {
130 p->set_shared();
131 }
132 p = next;
133 }
134 }
135 // give the new table the free list as well
136 new_table->copy_freelist(this);
137 assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");
138
139 // Destroy memory used by the buckets in the hashtable. The memory
140 // for the elements has been used in a new table and is not
141 // destroyed. The memory reuse will benefit resizing the SystemDictionary
142 // to avoid a memory allocation spike at safepoint.
143 BasicHashtable<F>::free_buckets();
144 }
145
146 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
147 if (NULL != _buckets) {
148 // Don't delete the buckets in the shared space. They aren't
149 // allocated by os::malloc
150 if (!UseSharedSpaces ||
151 !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {
152 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
153 }
154 _buckets = NULL;
155 }
156 }
157
158
159 // Reverse the order of elements in the hash buckets.
160
161 template <MEMFLAGS F> void BasicHashtable<F>::reverse() {
162
163 for (int i = 0; i < _table_size; ++i) {
164 BasicHashtableEntry<F>* new_list = NULL;
165 BasicHashtableEntry<F>* p = bucket(i);
166 while (p != NULL) {
167 BasicHashtableEntry<F>* next = p->next();
168 p->set_next(new_list);
169 new_list = p;
170 p = next;
171 }
172 *bucket_addr(i) = new_list;
173 }
174 }
175
176
177 // Copy the table to the shared space.
178
179 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {
180
181 // Dump the hash table entries.
182
183 intptr_t *plen = (intptr_t*)(*top);
184 *top += sizeof(*plen);
185
186 int i;
187 for (i = 0; i < _table_size; ++i) {
188 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
189 *p != NULL;
190 p = (*p)->next_addr()) {
191 if (*top + entry_size() > end) {
192 report_out_of_shared_space(SharedMiscData);
193 }
194 *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());
195 *top += entry_size();
196 }
197 }
198 *plen = (char*)(*top) - (char*)plen - sizeof(*plen);
199
200 // Set the shared bit.
201
202 for (i = 0; i < _table_size; ++i) {
203 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
204 p->set_shared();
205 }
206 }
207 }
208
209
210
211 // Reverse the order of elements in the hash buckets.
212
213 template <class T, MEMFLAGS F> void Hashtable<T, F>::reverse(void* boundary) {
214
215 for (int i = 0; i < this->table_size(); ++i) {
216 HashtableEntry<T, F>* high_list = NULL;
217 HashtableEntry<T, F>* low_list = NULL;
218 HashtableEntry<T, F>* last_low_entry = NULL;
219 HashtableEntry<T, F>* p = bucket(i);
220 while (p != NULL) {
221 HashtableEntry<T, F>* next = p->next();
222 if ((void*)p->literal() >= boundary) {
223 p->set_next(high_list);
224 high_list = p;
225 } else {
226 p->set_next(low_list);
227 low_list = p;
228 if (last_low_entry == NULL) {
229 last_low_entry = p;
230 }
231 }
232 p = next;
233 }
234 if (low_list != NULL) {
235 *bucket_addr(i) = low_list;
236 last_low_entry->set_next(high_list);
237 } else {
238 *bucket_addr(i) = high_list;
239 }
240 }
241 }
242
243 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) {
244 return symbol->size() * HeapWordSize;
245 }
246
247 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) {
248 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
249 // and the String.value array is shared by several Strings. However, starting from JDK8,
250 // the String.value array is not shared anymore.
251 assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");
252 return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;
253 }
254
255 // Dump footprint and bucket length statistics
256 //
257 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
258 // add a new function Hashtable<T, F>::literal_size(MyNewType lit)
259
260 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
261 NumberSeq summary;
262 int literal_bytes = 0;
263 for (int i = 0; i < this->table_size(); ++i) {
264 int count = 0;
265 for (HashtableEntry<T, F>* e = this->bucket(i);
266 e != NULL; e = e->next()) {
267 count++;
268 literal_bytes += literal_size(e->literal());
269 }
270 summary.add((double)count);
271 }
272 double num_buckets = summary.num();
273 double num_entries = summary.sum();
274
275 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
276 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
277 int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
278
279 double bucket_avg = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets);
280 double entry_avg = (num_entries <= 0) ? 0 : (entry_bytes / num_entries);
281 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
282
283 st->print_cr("%s statistics:", table_name);
284 st->print_cr("Number of buckets : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes, bucket_avg);
285 st->print_cr("Number of entries : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes, entry_avg);
286 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
287 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes);
288 st->print_cr("Average bucket size : %9.3f", summary.avg());
289 st->print_cr("Variance of bucket size : %9.3f", summary.variance());
290 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
291 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum());
292 }
293
294
295 // Dump the hash table buckets.
296
297 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {
298 intptr_t len = _table_size * sizeof(HashtableBucket<F>);
299 *(intptr_t*)(*top) = len;
300 *top += sizeof(intptr_t);
301
302 *(intptr_t*)(*top) = _number_of_entries;
303 *top += sizeof(intptr_t);
304
305 if (*top + len > end) {
306 report_out_of_shared_space(SharedMiscData);
307 }
308 _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);
309 *top += len;
310 }
311
312
313 #ifndef PRODUCT
314
315 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
316 ResourceMark rm;
317
318 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
319 HashtableEntry<T, F>* entry = bucket(i);
320 while(entry != NULL) {
321 tty->print("%d : ", i);
322 entry->literal()->print();
323 tty->cr();
324 entry = entry->next();
325 }
326 }
327 }
328
329
330 template <MEMFLAGS F> void BasicHashtable<F>::verify() {
331 int count = 0;
332 for (int i = 0; i < table_size(); i++) {
333 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
334 ++count;
335 }
336 }
337 assert(count == number_of_entries(), "number of hashtable entries incorrect");
338 }
339
340
341 #endif // PRODUCT
342
343 #ifdef ASSERT
344
345 template <MEMFLAGS F> void BasicHashtable<F>::verify_lookup_length(double load) {
346 if ((double)_lookup_length / (double)_lookup_count > load * 2.0) {
347 warning("Performance bug: SystemDictionary lookup_count=%d "
348 "lookup_length=%d average=%lf load=%f",
349 _lookup_count, _lookup_length,
350 (double) _lookup_length / _lookup_count, load);
351 }
352 }
353
354 #endif
355
356
357 // Explicitly instantiate these types
358 #if INCLUDE_ALL_GCS
359 template class Hashtable<nmethod*, mtGC>;
360 template class HashtableEntry<nmethod*, mtGC>;
361 template class BasicHashtable<mtGC>;
362 #endif
363 template class Hashtable<ConstantPool*, mtClass>;
364 template class RehashableHashtable<Symbol*, mtSymbol>;
365 template class RehashableHashtable<oopDesc*, mtSymbol>;
366 template class Hashtable<Symbol*, mtSymbol>;
367 template class Hashtable<Klass*, mtClass>;
368 template class Hashtable<InstanceKlass*, mtClass>;
369 template class Hashtable<oop, mtClass>;
370 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
371 template class Hashtable<oop, mtSymbol>;
372 template class RehashableHashtable<oop, mtSymbol>;
373 #endif // SOLARIS || CHECK_UNHANDLED_OOPS
374 template class Hashtable<oopDesc*, mtSymbol>;
375 template class Hashtable<Symbol*, mtClass>;
376 template class HashtableEntry<Symbol*, mtSymbol>;
377 template class HashtableEntry<Symbol*, mtClass>;
378 template class HashtableEntry<oop, mtSymbol>;
379 template class BasicHashtableEntry<mtSymbol>;
380 template class BasicHashtableEntry<mtCode>;
381 template class BasicHashtable<mtClass>;
382 template class BasicHashtable<mtClassShared>;
383 template class BasicHashtable<mtSymbol>;
384 template class BasicHashtable<mtCode>;
385 template class BasicHashtable<mtInternal>;
386 template class BasicHashtable<mtCompiler>;