1 /*
   2  * Copyright (c) 2014, 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 "code/codeCache.hpp"
  27 #include "code/nmethod.hpp"
  28 #include "gc_implementation/g1/g1CodeCacheRemSet.hpp"
  29 #include "gc_implementation/g1/heapRegion.hpp"
  30 #include "memory/heap.hpp"
  31 #include "memory/iterator.hpp"
  32 #include "oops/oop.inline.hpp"
  33 #include "utilities/hashtable.inline.hpp"
  34 #include "utilities/stack.inline.hpp"
  35 
  36 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  37 
  38 class CodeRootSetTable : public Hashtable<nmethod*, mtGC> {
  39   friend class G1CodeRootSetTest;
  40   typedef HashtableEntry<nmethod*, mtGC> Entry;
  41 
  42   static CodeRootSetTable* volatile _purge_list;
  43 
  44   CodeRootSetTable* _purge_next;
  45 
  46   unsigned int compute_hash(nmethod* nm) {
  47     uintptr_t hash = (uintptr_t)nm;
  48     return hash ^ (hash >> 7); // code heap blocks are 128byte aligned
  49   }
  50 
  51   void remove_entry(Entry* e, Entry* previous);
  52   Entry* new_entry(nmethod* nm);
  53 
  54  public:
  55   CodeRootSetTable(int size) : Hashtable<nmethod*, mtGC>(size, sizeof(Entry)), _purge_next(NULL) {}
  56   ~CodeRootSetTable();
  57 
  58   // Needs to be protected locks
  59   bool add(nmethod* nm);
  60   bool remove(nmethod* nm);
  61 
  62   // Can be called without locking
  63   bool contains(nmethod* nm);
  64 
  65   int entry_size() const { return BasicHashtable<mtGC>::entry_size(); }
  66 
  67   void copy_to(CodeRootSetTable* new_table);
  68   void nmethods_do(CodeBlobClosure* blk);
  69 
  70   template<typename CB>
  71   int remove_if(CB& should_remove);
  72 
  73   static void purge_list_append(CodeRootSetTable* tbl);
  74   static void purge();
  75 
  76   static size_t static_mem_size() {
  77     return sizeof(_purge_list);
  78   }
  79 
  80   size_t mem_size();
  81 };
  82 
  83 CodeRootSetTable* volatile CodeRootSetTable::_purge_list = NULL;
  84 
  85 size_t CodeRootSetTable::mem_size() {
  86   return sizeof(CodeRootSetTable) + (entry_size() * number_of_entries()) + (sizeof(HashtableBucket<mtGC>) * table_size());
  87 }
  88 
  89 CodeRootSetTable::Entry* CodeRootSetTable::new_entry(nmethod* nm) {
  90   unsigned int hash = compute_hash(nm);
  91   Entry* entry = (Entry*) new_entry_free_list();
  92   if (entry == NULL) {
  93     entry = (Entry*) NEW_C_HEAP_ARRAY2(char, entry_size(), mtGC, CURRENT_PC);
  94   }
  95   entry->set_next(NULL);
  96   entry->set_hash(hash);
  97   entry->set_literal(nm);
  98   return entry;
  99 }
 100 
 101 void CodeRootSetTable::remove_entry(Entry* e, Entry* previous) {
 102   int index = hash_to_index(e->hash());
 103   assert((e == bucket(index)) == (previous == NULL), "if e is the first entry then previous should be null");
 104 
 105   if (previous == NULL) {
 106     set_entry(index, e->next());
 107   } else {
 108     previous->set_next(e->next());
 109   }
 110   free_entry(e);
 111 }
 112 
 113 CodeRootSetTable::~CodeRootSetTable() {
 114   for (int index = 0; index < table_size(); ++index) {
 115     for (Entry* e = bucket(index); e != NULL; ) {
 116       Entry* to_remove = e;
 117       // read next before freeing.
 118       e = e->next();
 119       unlink_entry(to_remove);
 120       FREE_C_HEAP_ARRAY(char, to_remove, mtGC);
 121     }
 122   }
 123   assert(number_of_entries() == 0, "should have removed all entries");
 124   free_buckets();
 125   for (BasicHashtableEntry<mtGC>* e = new_entry_free_list(); e != NULL; e = new_entry_free_list()) {
 126     FREE_C_HEAP_ARRAY(char, e, mtGC);
 127   }
 128 }
 129 
 130 bool CodeRootSetTable::add(nmethod* nm) {
 131   if (!contains(nm)) {
 132     Entry* e = new_entry(nm);
 133     int index = hash_to_index(e->hash());
 134     add_entry(index, e);
 135     return true;
 136   }
 137   return false;
 138 }
 139 
 140 bool CodeRootSetTable::contains(nmethod* nm) {
 141   int index = hash_to_index(compute_hash(nm));
 142   for (Entry* e = bucket(index); e != NULL; e = e->next()) {
 143     if (e->literal() == nm) {
 144       return true;
 145     }
 146   }
 147   return false;
 148 }
 149 
 150 bool CodeRootSetTable::remove(nmethod* nm) {
 151   int index = hash_to_index(compute_hash(nm));
 152   Entry* previous = NULL;
 153   for (Entry* e = bucket(index); e != NULL; previous = e, e = e->next()) {
 154     if (e->literal() == nm) {
 155       remove_entry(e, previous);
 156       return true;
 157     }
 158   }
 159   return false;
 160 }
 161 
 162 void CodeRootSetTable::copy_to(CodeRootSetTable* new_table) {
 163   for (int index = 0; index < table_size(); ++index) {
 164     for (Entry* e = bucket(index); e != NULL; e = e->next()) {
 165       new_table->add(e->literal());
 166     }
 167   }
 168   new_table->copy_freelist(this);
 169 }
 170 
 171 void CodeRootSetTable::nmethods_do(CodeBlobClosure* blk) {
 172   for (int index = 0; index < table_size(); ++index) {
 173     for (Entry* e = bucket(index); e != NULL; e = e->next()) {
 174       blk->do_code_blob(e->literal());
 175     }
 176   }
 177 }
 178 
 179 template<typename CB>
 180 int CodeRootSetTable::remove_if(CB& should_remove) {
 181   int num_removed = 0;
 182   for (int index = 0; index < table_size(); ++index) {
 183     Entry* previous = NULL;
 184     Entry* e = bucket(index);
 185     while (e != NULL) {
 186       Entry* next = e->next();
 187       if (should_remove(e->literal())) {
 188         remove_entry(e, previous);
 189         ++num_removed;
 190       } else {
 191         previous = e;
 192       }
 193       e = next;
 194     }
 195   }
 196   return num_removed;
 197 }
 198 
 199 G1CodeRootSet::~G1CodeRootSet() {
 200   delete _table;
 201 }
 202 
 203 CodeRootSetTable* G1CodeRootSet::load_acquire_table() {
 204   return (CodeRootSetTable*) OrderAccess::load_ptr_acquire(&_table);
 205 }
 206 
 207 void G1CodeRootSet::allocate_small_table() {
 208   _table = new CodeRootSetTable(SmallSize);


 209 }
 210 
 211 void CodeRootSetTable::purge_list_append(CodeRootSetTable* table) {
 212   for (;;) {
 213     table->_purge_next = _purge_list;
 214     CodeRootSetTable* old = (CodeRootSetTable*) Atomic::cmpxchg_ptr(table, &_purge_list, table->_purge_next);
 215     if (old == table->_purge_next) {
 216       break;
 217     }
 218   }
 219 }
 220 
 221 void CodeRootSetTable::purge() {
 222   CodeRootSetTable* table = _purge_list;
 223   _purge_list = NULL;
 224   while (table != NULL) {
 225     CodeRootSetTable* to_purge = table;
 226     table = table->_purge_next;
 227     delete to_purge;
 228   }
 229 }
 230 
 231 void G1CodeRootSet::move_to_large() {
 232   CodeRootSetTable* temp = new CodeRootSetTable(LargeSize);
 233 
 234   _table->copy_to(temp);
 235 
 236   CodeRootSetTable::purge_list_append(_table);
 237 
 238   OrderAccess::release_store_ptr(&_table, temp);
 239 }
 240 
 241 void G1CodeRootSet::purge() {
 242   CodeRootSetTable::purge();
 243 }
 244 
 245 size_t G1CodeRootSet::static_mem_size() {
 246   return CodeRootSetTable::static_mem_size();
 247 }
 248 
 249 void G1CodeRootSet::add(nmethod* method) {
 250   bool added = false;
 251   if (is_empty()) {
 252     allocate_small_table();
 253   }
 254   added = _table->add(method);
 255   if (added) {
 256     if (_length == Threshold) {
 257       move_to_large();
 258     }
 259     ++_length;
 260   }
 261   assert(_length == (size_t)_table->number_of_entries(), "sizes should match");
 262 }
 263 
 264 bool G1CodeRootSet::remove(nmethod* method) {
 265   bool removed = false;
 266   if (_table != NULL) {
 267     removed = _table->remove(method);
 268   }
 269   if (removed) {
 270     _length--;
 271     if (_length == 0) {
 272       clear();
 273     }
 274   }
 275   assert((_length == 0 && _table == NULL) ||
 276          (_length == (size_t)_table->number_of_entries()), "sizes should match");
 277   return removed;
 278 }
 279 
 280 bool G1CodeRootSet::contains(nmethod* method) {
 281   CodeRootSetTable* table = load_acquire_table(); // contains() may be called outside of lock, so ensure mem sync.
 282   if (table != NULL) {
 283     return table->contains(method);
 284   }
 285   return false;
 286 }
 287 
 288 void G1CodeRootSet::clear() {
 289   delete _table;
 290   _table = NULL;
 291   _length = 0;
 292 }
 293 
 294 size_t G1CodeRootSet::mem_size() {
 295   return sizeof(*this) + (_table != NULL ? _table->mem_size() : 0);
 296 }
 297 
 298 void G1CodeRootSet::nmethods_do(CodeBlobClosure* blk) const {
 299   if (_table != NULL) {
 300     _table->nmethods_do(blk);
 301   }
 302 }
 303 
 304 class CleanCallback : public StackObj {
 305   class PointsIntoHRDetectionClosure : public OopClosure {
 306     HeapRegion* _hr;
 307    public:
 308     bool _points_into;
 309     PointsIntoHRDetectionClosure(HeapRegion* hr) : _hr(hr), _points_into(false) {}
 310 
 311     void do_oop(narrowOop* o) {
 312       do_oop_work(o);
 313     }
 314 
 315     void do_oop(oop* o) {
 316       do_oop_work(o);
 317     }
 318 
 319     template <typename T>
 320     void do_oop_work(T* p) {
 321       if (_hr->is_in(oopDesc::load_decode_heap_oop(p))) {
 322         _points_into = true;
 323       }
 324     }
 325   };
 326 
 327   PointsIntoHRDetectionClosure _detector;
 328   CodeBlobToOopClosure _blobs;
 329 
 330  public:
 331   CleanCallback(HeapRegion* hr) : _detector(hr), _blobs(&_detector, !CodeBlobToOopClosure::FixRelocations) {}
 332 
 333   bool operator() (nmethod* nm) {
 334     _detector._points_into = false;
 335     _blobs.do_code_blob(nm);
 336     return !_detector._points_into;
 337   }
 338 };
 339 
 340 void G1CodeRootSet::clean(HeapRegion* owner) {
 341   CleanCallback should_clean(owner);
 342   if (_table != NULL) {
 343     int removed = _table->remove_if(should_clean);
 344     assert((size_t)removed <= _length, "impossible");
 345     _length -= removed;
 346   }
 347   if (_length == 0) {
 348     clear();
 349   }
 350 }
 351 
 352 #ifndef PRODUCT
 353 
 354 class G1CodeRootSetTest {
 355  public:
 356   static void test() {
 357     {
 358       G1CodeRootSet set1;
 359       assert(set1.is_empty(), "Code root set must be initially empty but is not.");
 360 
 361       assert(G1CodeRootSet::static_mem_size() == sizeof(void*),
 362           err_msg("The code root set's static memory usage is incorrect, " SIZE_FORMAT " bytes", G1CodeRootSet::static_mem_size()));
 363 
 364       set1.add((nmethod*)1);
 365       assert(set1.length() == 1, err_msg("Added exactly one element, but set contains "
 366           SIZE_FORMAT " elements", set1.length()));
 367 
 368       const size_t num_to_add = (size_t)G1CodeRootSet::Threshold + 1;
 369 
 370       for (size_t i = 1; i <= num_to_add; i++) {
 371         set1.add((nmethod*)1);
 372       }
 373       assert(set1.length() == 1,
 374           err_msg("Duplicate detection should not have increased the set size but "
 375               "is " SIZE_FORMAT, set1.length()));
 376 
 377       for (size_t i = 2; i <= num_to_add; i++) {
 378         set1.add((nmethod*)(uintptr_t)(i));
 379       }
 380       assert(set1.length() == num_to_add,
 381           err_msg("After adding in total " SIZE_FORMAT " distinct code roots, they "
 382               "need to be in the set, but there are only " SIZE_FORMAT,
 383               num_to_add, set1.length()));
 384 
 385       assert(CodeRootSetTable::_purge_list != NULL, "should have grown to large hashtable");
 386 
 387       size_t num_popped = 0;
 388       for (size_t i = 1; i <= num_to_add; i++) {
 389         bool removed = set1.remove((nmethod*)i);
 390         if (removed) {
 391           num_popped += 1;
 392         } else {
 393           break;
 394         }
 395       }
 396       assert(num_popped == num_to_add,
 397           err_msg("Managed to pop " SIZE_FORMAT " code roots, but only " SIZE_FORMAT " "
 398               "were added", num_popped, num_to_add));
 399       assert(CodeRootSetTable::_purge_list != NULL, "should have grown to large hashtable");
 400 
 401       G1CodeRootSet::purge();
 402 
 403       assert(CodeRootSetTable::_purge_list == NULL, "should have purged old small tables");
 404 
 405     }
 406 
 407   }
 408 };
 409 
 410 void TestCodeCacheRemSet_test() {
 411   G1CodeRootSetTest::test();
 412 }
 413 
 414 #endif
--- EOF ---