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 // Check to see if the hashtable is unbalanced. The caller set a flag to
88 // rehash at the next safepoint. If this bucket is 60 times greater than the
89 // expected average bucket length, it's an unbalanced hashtable.
90 // This is somewhat an arbitrary heuristic but if one bucket gets to
91 // rehash_count which is currently 100, there's probably something wrong.
92
93 template <class T, MEMFLAGS F> bool RehashableHashtable<T, F>::check_rehash_table(int count) {
94 assert(this->table_size() != 0, "underflow");
95 if (count > (((double)this->number_of_entries()/(double)this->table_size())*rehash_multiple)) {
96 // Set a flag for the next safepoint, which should be at some guaranteed
97 // safepoint interval.
98 return true;
99 }
100 return false;
101 }
102
103 // Create a new table and using alternate hash code, populate the new table
104 // with the existing elements. This can be used to change the hash code
105 // and could in the future change the size of the table.
106
107 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::move_to(RehashableHashtable<T, F>* new_table) {
108
109 // Initialize the global seed for hashing.
110 _seed = AltHashing::compute_seed();
111 assert(seed() != 0, "shouldn't be zero");
112
113 int saved_entry_count = this->number_of_entries();
114
115 // Iterate through the table and create a new entry for the new table
116 for (int i = 0; i < new_table->table_size(); ++i) {
117 for (HashtableEntry<T, F>* p = this->bucket(i); p != NULL; ) {
118 HashtableEntry<T, F>* next = p->next();
119 T string = p->literal();
120 // Use alternate hashing algorithm on the symbol in the first table
121 unsigned int hashValue = string->new_hash(seed());
122 // Get a new index relative to the new table (can also change size)
123 int index = new_table->hash_to_index(hashValue);
124 p->set_hash(hashValue);
125 // Keep the shared bit in the Hashtable entry to indicate that this entry
126 // can't be deleted. The shared bit is the LSB in the _next field so
127 // walking the hashtable past these entries requires
128 // BasicHashtableEntry::make_ptr() call.
129 bool keep_shared = p->is_shared();
130 this->unlink_entry(p);
131 new_table->add_entry(index, p);
132 if (keep_shared) {
133 p->set_shared();
134 }
135 p = next;
136 }
137 }
138 // give the new table the free list as well
139 new_table->copy_freelist(this);
140 assert(new_table->number_of_entries() == saved_entry_count, "lost entry on dictionary copy?");
141
142 // Destroy memory used by the buckets in the hashtable. The memory
143 // for the elements has been used in a new table and is not
144 // destroyed. The memory reuse will benefit resizing the SystemDictionary
145 // to avoid a memory allocation spike at safepoint.
146 BasicHashtable<F>::free_buckets();
147 }
148
149 template <MEMFLAGS F> void BasicHashtable<F>::free_buckets() {
150 if (NULL != _buckets) {
151 // Don't delete the buckets in the shared space. They aren't
152 // allocated by os::malloc
153 if (!UseSharedSpaces ||
154 !FileMapInfo::current_info()->is_in_shared_space(_buckets)) {
155 FREE_C_HEAP_ARRAY(HashtableBucket, _buckets);
156 }
157 _buckets = NULL;
158 }
159 }
160
161 template <MEMFLAGS F> void BasicHashtable<F>::BucketUnlinkContext::free_entry(BasicHashtableEntry<F>* entry) {
162 entry->set_next(_removed_head);
163 _removed_head = entry;
164 if (_removed_tail == NULL) {
165 _removed_tail = entry;
166 }
167 _num_removed++;
168 }
169
170 template <MEMFLAGS F> void BasicHashtable<F>::bulk_free_entries(BucketUnlinkContext* context) {
171 if (context->_num_removed == 0) {
172 assert(context->_removed_head == NULL && context->_removed_tail == NULL,
173 "Zero entries in the unlink context, but elements linked from " PTR_FORMAT " to " PTR_FORMAT,
174 p2i(context->_removed_head), p2i(context->_removed_tail));
175 return;
176 }
177
178 // MT-safe add of the list of BasicHashTableEntrys from the context to the free list.
179 BasicHashtableEntry<F>* current = _free_list;
180 while (true) {
181 context->_removed_tail->set_next(current);
182 BasicHashtableEntry<F>* old = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(context->_removed_head, &_free_list, current);
183 if (old == current) {
184 break;
185 }
186 current = old;
187 }
188 Atomic::add(-context->_num_removed, &_number_of_entries);
189 }
190
191 // Copy the table to the shared space.
192
193 template <MEMFLAGS F> void BasicHashtable<F>::copy_table(char** top, char* end) {
194
195 // Dump the hash table entries.
196
197 intptr_t *plen = (intptr_t*)(*top);
198 *top += sizeof(*plen);
199
200 int i;
201 for (i = 0; i < _table_size; ++i) {
202 for (BasicHashtableEntry<F>** p = _buckets[i].entry_addr();
203 *p != NULL;
204 p = (*p)->next_addr()) {
205 if (*top + entry_size() > end) {
206 report_out_of_shared_space(SharedMiscData);
207 }
208 *p = (BasicHashtableEntry<F>*)memcpy(*top, *p, entry_size());
209 *top += entry_size();
210 }
211 }
212 *plen = (char*)(*top) - (char*)plen - sizeof(*plen);
213
214 // Set the shared bit.
215
216 for (i = 0; i < _table_size; ++i) {
217 for (BasicHashtableEntry<F>* p = bucket(i); p != NULL; p = p->next()) {
218 p->set_shared();
219 }
220 }
221 }
222
223 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(Symbol *symbol) {
224 return symbol->size() * HeapWordSize;
225 }
226
227 template <class T, MEMFLAGS F> int RehashableHashtable<T, F>::literal_size(oop oop) {
228 // NOTE: this would over-count if (pre-JDK8) java_lang_Class::has_offset_field() is true,
229 // and the String.value array is shared by several Strings. However, starting from JDK8,
230 // the String.value array is not shared anymore.
231 assert(oop != NULL && oop->klass() == SystemDictionary::String_klass(), "only strings are supported");
232 return (oop->size() + java_lang_String::value(oop)->size()) * HeapWordSize;
233 }
234
235 // Dump footprint and bucket length statistics
236 //
237 // Note: if you create a new subclass of Hashtable<MyNewType, F>, you will need to
238 // add a new function Hashtable<T, F>::literal_size(MyNewType lit)
239
240 template <class T, MEMFLAGS F> void RehashableHashtable<T, F>::dump_table(outputStream* st, const char *table_name) {
241 NumberSeq summary;
242 int literal_bytes = 0;
243 for (int i = 0; i < this->table_size(); ++i) {
244 int count = 0;
245 for (HashtableEntry<T, F>* e = this->bucket(i);
246 e != NULL; e = e->next()) {
247 count++;
248 literal_bytes += literal_size(e->literal());
249 }
250 summary.add((double)count);
251 }
252 double num_buckets = summary.num();
253 double num_entries = summary.sum();
254
255 int bucket_bytes = (int)num_buckets * sizeof(HashtableBucket<F>);
256 int entry_bytes = (int)num_entries * sizeof(HashtableEntry<T, F>);
257 int total_bytes = literal_bytes + bucket_bytes + entry_bytes;
258
259 double bucket_avg = (num_buckets <= 0) ? 0 : (bucket_bytes / num_buckets);
260 double entry_avg = (num_entries <= 0) ? 0 : (entry_bytes / num_entries);
261 double literal_avg = (num_entries <= 0) ? 0 : (literal_bytes / num_entries);
262
263 st->print_cr("%s statistics:", table_name);
264 st->print_cr("Number of buckets : %9d = %9d bytes, avg %7.3f", (int)num_buckets, bucket_bytes, bucket_avg);
265 st->print_cr("Number of entries : %9d = %9d bytes, avg %7.3f", (int)num_entries, entry_bytes, entry_avg);
266 st->print_cr("Number of literals : %9d = %9d bytes, avg %7.3f", (int)num_entries, literal_bytes, literal_avg);
267 st->print_cr("Total footprint : %9s = %9d bytes", "", total_bytes);
268 st->print_cr("Average bucket size : %9.3f", summary.avg());
269 st->print_cr("Variance of bucket size : %9.3f", summary.variance());
270 st->print_cr("Std. dev. of bucket size: %9.3f", summary.sd());
271 st->print_cr("Maximum bucket size : %9d", (int)summary.maximum());
272 }
273
274
275 // Dump the hash table buckets.
276
277 template <MEMFLAGS F> void BasicHashtable<F>::copy_buckets(char** top, char* end) {
278 intptr_t len = _table_size * sizeof(HashtableBucket<F>);
279 *(intptr_t*)(*top) = len;
280 *top += sizeof(intptr_t);
281
282 *(intptr_t*)(*top) = _number_of_entries;
283 *top += sizeof(intptr_t);
284
285 if (*top + len > end) {
286 report_out_of_shared_space(SharedMiscData);
287 }
288 _buckets = (HashtableBucket<F>*)memcpy(*top, _buckets, len);
289 *top += len;
290 }
291
292
293 #ifndef PRODUCT
294
295 template <class T, MEMFLAGS F> void Hashtable<T, F>::print() {
296 ResourceMark rm;
297
298 for (int i = 0; i < BasicHashtable<F>::table_size(); i++) {
299 HashtableEntry<T, F>* entry = bucket(i);
300 while(entry != NULL) {
301 tty->print("%d : ", i);
302 entry->literal()->print();
303 tty->cr();
304 entry = entry->next();
305 }
306 }
307 }
308
309 template <MEMFLAGS F>
310 template <class T> void BasicHashtable<F>::verify_table(const char* table_name) {
311 int element_count = 0;
312 int max_bucket_count = 0;
313 int max_bucket_number = 0;
314 for (int index = 0; index < table_size(); index++) {
315 int bucket_count = 0;
316 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
317 probe->verify();
318 bucket_count++;
319 }
320 element_count += bucket_count;
321 if (bucket_count > max_bucket_count) {
322 max_bucket_count = bucket_count;
323 max_bucket_number = index;
324 }
325 }
326 guarantee(number_of_entries() == element_count,
327 "Verify of %s failed", table_name);
328
329 // Log some statistics about the hashtable
330 log_info(hashtables)("%s max bucket size %d bucket %d element count %d table size %d", table_name,
331 max_bucket_count, max_bucket_number, _number_of_entries, _table_size);
332 if (_number_of_entries > 0 && log_is_enabled(Debug, hashtables)) {
333 for (int index = 0; index < table_size(); index++) {
334 int bucket_count = 0;
335 for (T* probe = (T*)bucket(index); probe != NULL; probe = probe->next()) {
336 log_debug(hashtables)("bucket %d hash " INTPTR_FORMAT, index, (intptr_t)probe->hash());
337 bucket_count++;
338 }
339 if (bucket_count > 0) {
340 log_debug(hashtables)("bucket %d count %d", index, bucket_count);
341 }
342 }
343 }
344 }
345 #endif // PRODUCT
346
347 // Explicitly instantiate these types
348 #if INCLUDE_ALL_GCS
349 template class Hashtable<nmethod*, mtGC>;
350 template class HashtableEntry<nmethod*, mtGC>;
351 template class BasicHashtable<mtGC>;
352 #endif
353 template class Hashtable<ConstantPool*, mtClass>;
354 template class RehashableHashtable<Symbol*, mtSymbol>;
355 template class RehashableHashtable<oopDesc*, mtSymbol>;
356 template class Hashtable<Symbol*, mtSymbol>;
357 template class Hashtable<Klass*, mtClass>;
358 template class Hashtable<InstanceKlass*, mtClass>;
359 template class Hashtable<oop, mtClass>;
360 #if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
361 template class Hashtable<oop, mtSymbol>;
362 template class RehashableHashtable<oop, mtSymbol>;
363 #endif // SOLARIS || CHECK_UNHANDLED_OOPS
364 template class Hashtable<oopDesc*, mtSymbol>;
365 template class Hashtable<Symbol*, mtClass>;
366 template class HashtableEntry<Symbol*, mtSymbol>;
367 template class HashtableEntry<Symbol*, mtClass>;
368 template class HashtableEntry<oop, mtSymbol>;
369 template class BasicHashtableEntry<mtSymbol>;
370 template class BasicHashtableEntry<mtCode>;
371 template class BasicHashtable<mtClass>;
372 template class BasicHashtable<mtClassShared>;
373 template class BasicHashtable<mtSymbol>;
374 template class BasicHashtable<mtCode>;
375 template class BasicHashtable<mtInternal>;
376 template class BasicHashtable<mtModule>;
377 #if INCLUDE_TRACE
378 template class Hashtable<Symbol*, mtTracing>;
379 template class HashtableEntry<Symbol*, mtTracing>;
380 template class BasicHashtable<mtTracing>;
381 #endif
382 template class BasicHashtable<mtCompiler>;
383
384 template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
385 template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
386 template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
387 template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
388 template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);
389