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
47template <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.
57template <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
79template <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.
89template <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
104template <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
118template <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
160template <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
172template <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
181template <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 = (BasicHashtableEntry<F>*)Atomic::cmpxchg_ptr(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.
202template <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)
218template <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.
244static int literal_size(ConstantPool*) { return 0; }
245static int literal_size(Klass*)        { return 0; }
246#if INCLUDE_ALL_GCS
247static int literal_size(nmethod*)      { return 0; }
248#endif
249
250static int literal_size(Symbol *symbol) {
251  return symbol->size() * HeapWordSize;
252}
253
254static 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
277template <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
317template <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)
327template <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
344template <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
358template <MEMFLAGS F>
359template <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
398template class Hashtable<nmethod*, mtGC>;
399template class HashtableEntry<nmethod*, mtGC>;
400template class BasicHashtable<mtGC>;
401#endif
402template class Hashtable<ConstantPool*, mtClass>;
403template class RehashableHashtable<Symbol*, mtSymbol>;
404template class RehashableHashtable<oopDesc*, mtSymbol>;
405template class Hashtable<Symbol*, mtSymbol>;
406template class Hashtable<Klass*, mtClass>;
407template class Hashtable<InstanceKlass*, mtClass>;
408template class Hashtable<oop, mtClass>;
409template class Hashtable<Symbol*, mtModule>;
410#if defined(SOLARIS) || defined(CHECK_UNHANDLED_OOPS)
411template class Hashtable<oop, mtSymbol>;
412template class RehashableHashtable<oop, mtSymbol>;
413#endif // SOLARIS || CHECK_UNHANDLED_OOPS
414template class Hashtable<oopDesc*, mtSymbol>;
415template class Hashtable<Symbol*, mtClass>;
416template class HashtableEntry<Symbol*, mtSymbol>;
417template class HashtableEntry<Symbol*, mtClass>;
418template class HashtableEntry<oop, mtSymbol>;
419template class HashtableBucket<mtClass>;
420template class BasicHashtableEntry<mtSymbol>;
421template class BasicHashtableEntry<mtCode>;
422template class BasicHashtable<mtClass>;
423template class BasicHashtable<mtClassShared>;
424template class BasicHashtable<mtSymbol>;
425template class BasicHashtable<mtCode>;
426template class BasicHashtable<mtInternal>;
427template class BasicHashtable<mtModule>;
428#if INCLUDE_TRACE
429template class Hashtable<Symbol*, mtTracing>;
430template class HashtableEntry<Symbol*, mtTracing>;
431template class BasicHashtable<mtTracing>;
432#endif
433template class BasicHashtable<mtCompiler>;
434
435template void BasicHashtable<mtClass>::verify_table<DictionaryEntry>(char const*);
436template void BasicHashtable<mtModule>::verify_table<ModuleEntry>(char const*);
437template void BasicHashtable<mtModule>::verify_table<PackageEntry>(char const*);
438template void BasicHashtable<mtClass>::verify_table<ProtectionDomainCacheEntry>(char const*);
439template void BasicHashtable<mtClass>::verify_table<PlaceholderEntry>(char const*);
440