1 /*
2 * Copyright (c) 2003, 2017, 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 "memory/allocation.inline.hpp"
35 #include "memory/filemap.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/safepoint.hpp"
39 #include "utilities/dtrace.hpp"
40 #include "utilities/hashtable.hpp"
41 #include "utilities/hashtable.inline.hpp"
42 #include "utilities/numberSeq.hpp"
43
44
45 // This hashtable is implemented as an open hash table with a fixed number of buckets.
46
47 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry_free_list() {
48 BasicHashtableEntry<F>* entry = NULL;
49 if (_free_list != NULL) {
50 entry = _free_list;
51 _free_list = _free_list->next();
52 }
53 return entry;
54 }
55
56 // HashtableEntrys are allocated in blocks to reduce the space overhead.
57 template <MEMFLAGS F> BasicHashtableEntry<F>* BasicHashtable<F>::new_entry(unsigned int hashValue) {
58 BasicHashtableEntry<F>* entry = new_entry_free_list();
59
60 if (entry == NULL) {
61 if (_first_free_entry + _entry_size >= _end_block) {
62 int block_size = MIN2(512, MAX2((int)_table_size / 2, (int)_number_of_entries));
63 int len = _entry_size * block_size;
64 len = 1 << log2_intptr(len); // round down to power of 2
65 assert(len >= _entry_size, "");
66 _first_free_entry = NEW_C_HEAP_ARRAY2(char, len, F, CURRENT_PC);
67 _end_block = _first_free_entry + len;
68 }
69 entry = (BasicHashtableEntry<F>*)_first_free_entry;
70 _first_free_entry += _entry_size;
71 }
72
73 assert(_entry_size % HeapWordSize == 0, "");
74 entry->set_hash(hashValue);
75 return entry;
76 }
77
78
79 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::new_entry(unsigned int hashValue, T obj) {
80 HashtableEntry<T, F>* entry;
81
82 entry = (HashtableEntry<T, F>*)BasicHashtable<F>::new_entry(hashValue);
83 entry->set_literal(obj);
84 return entry;
85 }
86
87 // Version of hashtable entry allocation that allocates in the C heap directly.
88 // The allocator in blocks is preferable but doesn't have free semantics.
89 template <class T, MEMFLAGS F> HashtableEntry<T, F>* Hashtable<T, F>::allocate_new_entry(unsigned int hashValue, T obj) {
90 HashtableEntry<T, F>* entry = (HashtableEntry<T, F>*) NEW_C_HEAP_ARRAY(char, this->entry_size(), F);
91
92 entry->set_hash(hashValue);
93 entry->set_literal(obj);
94 entry->set_next(NULL);
95 return entry;
96 }
97
98 // Check to see if the hashtable is unbalanced. The caller set a flag to
99 // rehash at the next safepoint. If this bucket is 60 times greater than the
100 // expected average bucket length, it's an unbalanced hashtable.
101 // This is somewhat an arbitrary heuristic but if one bucket gets to
102 // rehash_count which is currently 100, there's probably something wrong.
103
104 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {
105 assert(this->table_size() != 0, "underflow");
106 if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {
107 // Set a flag for the next safepoint, which should be at some guaranteed
108 // safepoint interval.
109 return true;
110 }
111 return false;
112 }
113
114 // Create a new table and using alternate hash code, populate the new table
115 // with the existing elements. This can be used to change the hash code
116 // and could in the future change the size of the table.
117
118 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
119
120 // Initialize the global seed for hashing.
121 _seed = AltHashing::compute_seed();
122 assert(seed() != 0, "shouldn't be zero");
123
124 int saved_entry_count = this->number_of_entries();
125
126 // Iterate through the table and create a new entry for the new table
127 for (int i = 0; i < new_table->table_size(); ++i) {
128 for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
129 HashtableEntry<T, F>* next = p->next();
130 T string = p->literal();
131 // Use alternate hashing algorithm on the symbol in the first table
132 unsigned int hashValue = string->new_hash(seed());
133 // Get a new index relative to the new table (can also change size)
134 int index = new_table->hash_to_index(hashValue);
135 p->set_hash(hashValue);
136 // Keep the shared bit in the Hashtable entry to indicate that this entry
137 // can't be deleted. The shared bit is the LSB in the _next field so
138 // walking the hashtable past these entries requires
139 // BasicHashtableEntry::make_ptr() call.
140 bool keep_shared = p->is_shared();
141 this->unlink_entry(p);
142 new_table->add_entry(index, p);
143 if (keep_shared) {
144 p->set_shared();
145 }
146 p = next;
147 }
148 }
149 // give the new table the free list as well
150 new_table->copy_freelist(this);
151 assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");
152
153 // Destroy memory used by the buckets in the hashtable. The memory
154 // for the elements has been used in a new table and is not
155 // destroyed. The memory reuse will benefit resizing the SystemDictionary
156 // to avoid a memory allocation spike at safepoint.
157 BasicHashtable<F>::free_buckets();
158 }
159
160 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
161 if (NULL != _buckets) {
162 // Don't delete the buckets in the shared space. They aren't
163 // allocated by os::malloc
164 if (!UseSharedSpaces ||
165 !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {
166 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
167 }
168 _buckets = NULL;
169 }
170 }
171
172 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) {
173 entry->set_next(_removed_head);
174 _removed_head = entry;
175 if (_removed_tail == NULL) {
176 _removed_tail = entry;
177 }
178 _num_removed++;
179 }
180
181 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) {
182 if (context->_num_removed == 0) {
183 assert(context->_removed_head == NULL && context->_removed_tail == NULL,
184 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT,
185 p2i(context->_removed_head), p2i(context->_removed_tail));
186 return;
187 }
188
189 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list.
190 BasicHashtableEntry<F>* current = _free_list;
191 while (true) {
192 context->_removed_tail->set_next(current);
193 BasicHashtableEntry<F>* old = Atomic::cmpxchg(context->_removed_head, &_free_list, current);
194 if (old == current) {
195 break;
196 }
197 current = old;
198 }
199 Atomic::add(-context->_num_removed, &_number_of_entries);
200 }
201 // Copy the table to the shared space.
202 template <MEMFLAGS F> size_t BasicHashtable<F>::count_bytes_for_table() {
203 size_t bytes = 0;
204 bytes += sizeof(intptr_t); // len
205
206 for (int i = 0; i < _table_size; ++i) {
207 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
208 *p != NULL;
209 p = (*p)->next_addr()) {
210 bytes += entry_size();
211 }
212 }
213
214 return bytes;
215 }
216
217 // Dump the hash table entries (into CDS archive)
218 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char* top, char* end) {
219 assert(is_aligned(top, sizeof(intptr_t)), "bad alignment");
220 intptr_t *plen = (intptr_t*)(top);
221 top += sizeof(*plen);
222
223 int i;
224 for (i = 0; i < _table_size; ++i) {
225 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
226 *p != NULL;
227 p = (*p)->next_addr()) {
228 *p = (BasicHashtableEntry<F>*)memcpy(top, (void*)*p, entry_size());
229 top += entry_size();
230 }
231 }
232 *plen = (char*)(top) - (char*)plen - sizeof(*plen);
233 assert(top == end, "count_bytes_for_table is wrong");
234 // Set the shared bit.
235
236 for (i = 0; i < _table_size; ++i) {
237 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
238 p->set_shared();
239 }
240 }
241 }
242
243 // For oops and Strings the size of the literal is interesting. For other types, nobody cares.
244 static int literal_size(ConstantPool*) { return 0; }
245 static int literal_size(Klass*) { return 0; }
246 #if INCLUDE_ALL_GCS
247 static int literal_size(nmethod*) { return 0; }
248 #endif
249
250 static int literal_size(Symbol *symbol) {
251 return symbol->size() * HeapWordSize;
252 }
253
254 static int literal_size(oop obj) {
255 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
256 // and the String.value array is shared by several Strings. However, starting from JDK8,
257 // the String.value array is not shared anymore.
258 if (obj == NULL) {
259 return 0;
260 } else if (obj->klass() == SystemDictionary::String_klass()) {
261 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;
262 } else {
263 return obj->size();
264 }
265 }
266
267
268 // Dump footprint and bucket length statistics
269 //
270 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
271 // add a new function static int literal_size(MyNewType lit)
272 // because I can't get template <class T> int literal_size(T) to pick the specializations for Symbol and oop.
273 //
274 // The StringTable and SymbolTable dumping print how much footprint is used by the String and Symbol
275 // literals.
276
277 template <class T, MEMFLAGS F> void Hashtable<T, F>::print_table_statistics(outputStream* st,
278 const char *table_name) {
279 NumberSeq summary;
280 int literal_bytes = 0;
281 for (int i = 0; i < this->table_size(); ++i) {
282 int count = 0;
283 for (HashtableEntry<T, F>* e = this->bucket(i);
284 e != NULL; e = e->next()) {
285 count++;
286 literal_bytes += literal_size(e->literal());
287 }
288 summary.add((double)count);
289 }
290 double num_buckets = summary.num();
291 double num_entries = summary.sum();
292
293 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
294 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
295 int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
296
297 int bucket_size = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets);
298 int entry_size = (num_entries <= 0) ? 0 : (entry_bytes / num_entries);
299
300 st->print_cr("%s statistics:", table_name);
301 st->print_cr("Number of buckets : %9d = %9d bytes, each %d", (int)num_buckets, bucket_bytes, bucket_size);
302 st->print_cr("Number of entries : %9d = %9d bytes, each %d", (int)num_entries, entry_bytes, entry_size);
303 if (literal_bytes != 0) {
304 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
305 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
306 }
307 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes);
308 st->print_cr("Average bucket size : %9.3f", summary.avg());
309 st->print_cr("Variance of bucket size : %9.3f", summary.variance());
310 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
311 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum());
312 }
313
314
315 // Dump the hash table buckets.
316
317 template <MEMFLAGS F> size_t BasicHashtable<F>::count_bytes_for_buckets() {
318 size_t bytes = 0;
319 bytes += sizeof(intptr_t); // len
320 bytes += sizeof(intptr_t); // _number_of_entries
321 bytes += _table_size * sizeof(HashtableBucket<F>); // the buckets
322
323 return bytes;
324 }
325
326 // Dump the buckets (into CDS archive)
327 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char* top, char* end) {
328 assert(is_aligned(top, sizeof(intptr_t)), "bad alignment");
329 intptr_t len = _table_size * sizeof(HashtableBucket<F>);
330 *(intptr_t*)(top) = len;
331 top += sizeof(intptr_t);
332
333 *(intptr_t*)(top) = _number_of_entries;
334 top += sizeof(intptr_t);
335
336 _buckets = (HashtableBucket<F>*)memcpy(top, (void*)_buckets, len);
337 top += len;
338
339 assert(top == end, "count_bytes_for_buckets is wrong");
340 }
341
342 #ifndef PRODUCT
343
344 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
345 ResourceMark rm;
346
347 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
348 HashtableEntry<T, F>* entry = bucket(i);
349 while(entry != NULL) {
350 tty->print("%d : ", i);
351 entry->literal()->print();
352 tty->cr();
353 entry = entry->next();
354 }
355 }
356 }
357
358 template <MEMFLAGS F>
359 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
360 int element_count = 0;
361 int max_bucket_count = 0;
362 int max_bucket_number = 0;
363 for (int index = 0; index < table_size(); index++) {
364 int bucket_count = 0;
365 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
366 probe->verify();
367 bucket_count++;
368 }
369 element_count += bucket_count;
370 if (bucket_count > max_bucket_count) {
371 max_bucket_count = bucket_count;
372 max_bucket_number = index;
373 }
374 }
375 guarantee(number_of_entries() == element_count,
376 "Verify of %s failed", table_name);
377
378 // Log some statistics about the hashtable
379 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
380 max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
381 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
382 for (int index = 0; index < table_size(); index++) {
383 int bucket_count = 0;
384 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
385 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
386 bucket_count++;
387 }
388 if (bucket_count > 0) {
389 log_debug(hashtables)("bucket %d count %d", index, bucket_count);
390 }
391 }
392 }
393 }
394 #endif // PRODUCT
395
396 // Explicitly instantiate these types
397 #if INCLUDE_ALL_GCS
398 template class Hashtable<nmethod*, mtGC>;
399 template class HashtableEntry<nmethod*, mtGC>;
400 template class BasicHashtable<mtGC>;
401 #endif
402 template class Hashtable<ConstantPool*, mtClass>;
403 template class RehashableHashtable<Symbol*, mtSymbol>;
404 template class RehashableHashtable<oopDesc*, mtSymbol>;
405 template class Hashtable<Symbol*, mtSymbol>;
406 template class Hashtable<Klass*, mtClass>;
407 template class Hashtable<InstanceKlass*, mtClass>;
408 template class Hashtable<oop, mtClass>;
409 template class Hashtable<Symbol*, mtModule>;
410 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
411 template class Hashtable<oop, mtSymbol>;
412 template class RehashableHashtable<oop, mtSymbol>;
413 #endif // SOLARIS || CHECK_UNHANDLED_OOPS
414 template class Hashtable<oopDesc*, mtSymbol>;
415 template class Hashtable<Symbol*, mtClass>;
416 template class HashtableEntry<Symbol*, mtSymbol>;
417 template class HashtableEntry<Symbol*, mtClass>;
418 template class HashtableEntry<oop, mtSymbol>;
419 template class HashtableBucket<mtClass>;
420 template class BasicHashtableEntry<mtSymbol>;
421 template class BasicHashtableEntry<mtCode>;
422 template class BasicHashtable<mtClass>;
423 template class BasicHashtable<mtClassShared>;
424 template class BasicHashtable<mtSymbol>;
425 template class BasicHashtable<mtCode>;
426 template class BasicHashtable<mtInternal>;
427 template class BasicHashtable<mtModule>;
428 #if INCLUDE_TRACE
429 template class Hashtable<Symbol*, mtTracing>;
430 template class HashtableEntry<Symbol*, mtTracing>;
431 template class BasicHashtable<mtTracing>;
432 #endif
433 template class BasicHashtable<mtCompiler>;
434
435 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
436 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
437 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
438 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
439 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);