1 /*
   2  * Copyright (c) 2011, 2015, 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 "gc/g1/g1CollectedHeap.inline.hpp"
  27 #include "gc/g1/heapRegionRemSet.hpp"
  28 #include "gc/g1/heapRegionSet.inline.hpp"
  29 
  30 uint FreeRegionList::_unrealistically_long_length = 0;
  31 
  32 void HeapRegionSetBase::fill_in_ext_msg(hrs_ext_msg* msg, const char* message) {
  33   msg->append("[%s] %s ln: %u cy: " SIZE_FORMAT,
  34               name(), message, length(), total_capacity_bytes());
  35   fill_in_ext_msg_extra(msg);
  36 }
  37 
  38 #ifndef PRODUCT
  39 void HeapRegionSetBase::verify_region(HeapRegion* hr) {
  40   assert(hr->containing_set() == this, "Inconsistent containing set for %u", hr->hrm_index());
  41   assert(!hr->is_young(), "Adding young region %u", hr->hrm_index()); // currently we don't use these sets for young regions
  42   assert(hr->is_humongous() == regions_humongous(), "Wrong humongous state for region %u and set %s", hr->hrm_index(), name());
  43   assert(hr->is_free() == regions_free(), "Wrong free state for region %u and set %s", hr->hrm_index(), name());
  44   assert(!hr->is_free() || hr->is_empty(), "Free region %u is not empty for set %s", hr->hrm_index(), name());
  45   assert(!hr->is_empty() || hr->is_free() || hr->is_archive(),
  46          "Empty region %u is not free or archive for set %s", hr->hrm_index(), name());
  47   assert(hr->rem_set()->verify_ready_for_par_iteration(), "Wrong iteration state %u", hr->hrm_index());
  48 }
  49 #endif
  50 
  51 void HeapRegionSetBase::verify() {
  52   // It's important that we also observe the MT safety protocol even
  53   // for the verification calls. If we do verification without the
  54   // appropriate locks and the set changes underneath our feet
  55   // verification might fail and send us on a wild goose chase.
  56   check_mt_safety();
  57 
  58   guarantee(( is_empty() && length() == 0 && total_capacity_bytes() == 0) ||
  59             (!is_empty() && length() > 0  && total_capacity_bytes() > 0) ,
  60             "%s", hrs_ext_msg(this, "invariant").buffer());
  61 }
  62 
  63 void HeapRegionSetBase::verify_start() {
  64   // See comment in verify() about MT safety and verification.
  65   check_mt_safety();
  66   assert(!_verify_in_progress,
  67          "%s", hrs_ext_msg(this, "verification should not be in progress").buffer());
  68 
  69   // Do the basic verification first before we do the checks over the regions.
  70   HeapRegionSetBase::verify();
  71 
  72   _verify_in_progress = true;
  73 }
  74 
  75 void HeapRegionSetBase::verify_end() {
  76   // See comment in verify() about MT safety and verification.
  77   check_mt_safety();
  78   assert(_verify_in_progress,
  79          "%s", hrs_ext_msg(this, "verification should be in progress").buffer());
  80 
  81   _verify_in_progress = false;
  82 }
  83 
  84 void HeapRegionSetBase::print_on(outputStream* out, bool print_contents) {
  85   out->cr();
  86   out->print_cr("Set: %s (" PTR_FORMAT ")", name(), p2i(this));
  87   out->print_cr("  Region Assumptions");
  88   out->print_cr("    humongous         : %s", BOOL_TO_STR(regions_humongous()));
  89   out->print_cr("    free              : %s", BOOL_TO_STR(regions_free()));
  90   out->print_cr("  Attributes");
  91   out->print_cr("    length            : %14u", length());
  92   out->print_cr("    total capacity    : " SIZE_FORMAT_W(14) " bytes",
  93                 total_capacity_bytes());
  94 }
  95 
  96 HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool free, HRSMtSafeChecker* mt_safety_checker)
  97   : _name(name), _verify_in_progress(false),
  98     _is_humongous(humongous), _is_free(free), _mt_safety_checker(mt_safety_checker),
  99     _count()
 100 { }
 101 
 102 void FreeRegionList::set_unrealistically_long_length(uint len) {
 103   guarantee(_unrealistically_long_length == 0, "should only be set once");
 104   _unrealistically_long_length = len;
 105 }
 106 
 107 void FreeRegionList::fill_in_ext_msg_extra(hrs_ext_msg* msg) {
 108   msg->append(" hd: " PTR_FORMAT " tl: " PTR_FORMAT, p2i(_head), p2i(_tail));
 109 }
 110 
 111 void FreeRegionList::remove_all() {
 112   check_mt_safety();
 113   verify_optional();
 114 
 115   HeapRegion* curr = _head;
 116   while (curr != NULL) {
 117     verify_region(curr);
 118 
 119     HeapRegion* next = curr->next();
 120     curr->set_next(NULL);
 121     curr->set_prev(NULL);
 122     curr->set_containing_set(NULL);
 123     curr = next;
 124   }
 125   clear();
 126 
 127   verify_optional();
 128 }
 129 
 130 void FreeRegionList::add_ordered(FreeRegionList* from_list) {
 131   check_mt_safety();
 132   from_list->check_mt_safety();
 133 
 134   verify_optional();
 135   from_list->verify_optional();
 136 
 137   if (from_list->is_empty()) {
 138     return;
 139   }
 140 
 141   #ifdef ASSERT
 142   FreeRegionListIterator iter(from_list);
 143   while (iter.more_available()) {
 144     HeapRegion* hr = iter.get_next();
 145     // In set_containing_set() we check that we either set the value
 146     // from NULL to non-NULL or vice versa to catch bugs. So, we have
 147     // to NULL it first before setting it to the value.
 148     hr->set_containing_set(NULL);
 149     hr->set_containing_set(this);
 150   }
 151   #endif // ASSERT
 152 
 153   if (is_empty()) {
 154     assert(length() == 0 && _tail == NULL, "%s", hrs_ext_msg(this, "invariant").buffer());
 155     _head = from_list->_head;
 156     _tail = from_list->_tail;
 157   } else {
 158     HeapRegion* curr_to = _head;
 159     HeapRegion* curr_from = from_list->_head;
 160 
 161     while (curr_from != NULL) {
 162       while (curr_to != NULL && curr_to->hrm_index() < curr_from->hrm_index()) {
 163         curr_to = curr_to->next();
 164       }
 165 
 166       if (curr_to == NULL) {
 167         // The rest of the from list should be added as tail
 168         _tail->set_next(curr_from);
 169         curr_from->set_prev(_tail);
 170         curr_from = NULL;
 171       } else {
 172         HeapRegion* next_from = curr_from->next();
 173 
 174         curr_from->set_next(curr_to);
 175         curr_from->set_prev(curr_to->prev());
 176         if (curr_to->prev() == NULL) {
 177           _head = curr_from;
 178         } else {
 179           curr_to->prev()->set_next(curr_from);
 180         }
 181         curr_to->set_prev(curr_from);
 182 
 183         curr_from = next_from;
 184       }
 185     }
 186 
 187     if (_tail->hrm_index() < from_list->_tail->hrm_index()) {
 188       _tail = from_list->_tail;
 189     }
 190   }
 191 
 192   _count.increment(from_list->length(), from_list->total_capacity_bytes());
 193   from_list->clear();
 194 
 195   verify_optional();
 196   from_list->verify_optional();
 197 }
 198 
 199 void FreeRegionList::remove_starting_at(HeapRegion* first, uint num_regions) {
 200   check_mt_safety();
 201   assert(num_regions >= 1, "%s", hrs_ext_msg(this, "pre-condition").buffer());
 202   assert(!is_empty(), "%s", hrs_ext_msg(this, "pre-condition").buffer());
 203 
 204   verify_optional();
 205   DEBUG_ONLY(uint old_length = length();)
 206 
 207   HeapRegion* curr = first;
 208   uint count = 0;
 209   while (count < num_regions) {
 210     verify_region(curr);
 211     HeapRegion* next = curr->next();
 212     HeapRegion* prev = curr->prev();
 213 
 214     assert(count < num_regions,
 215            "%s", hrs_err_msg("[%s] should not come across more regions "
 216                              "pending for removal than num_regions: %u",
 217                              name(), num_regions).buffer());
 218 
 219     if (prev == NULL) {
 220       assert(_head == curr, "%s", hrs_ext_msg(this, "invariant").buffer());
 221       _head = next;
 222     } else {
 223       assert(_head != curr, "%s", hrs_ext_msg(this, "invariant").buffer());
 224       prev->set_next(next);
 225     }
 226     if (next == NULL) {
 227       assert(_tail == curr, "%s", hrs_ext_msg(this, "invariant").buffer());
 228       _tail = prev;
 229     } else {
 230       assert(_tail != curr, "%s", hrs_ext_msg(this, "invariant").buffer());
 231       next->set_prev(prev);
 232     }
 233     if (_last = curr) {
 234       _last = NULL;
 235     }
 236 
 237     curr->set_next(NULL);
 238     curr->set_prev(NULL);
 239     remove(curr);
 240 
 241     count++;
 242     curr = next;
 243   }
 244 
 245   assert(count == num_regions,
 246          "%s", hrs_err_msg("[%s] count: %u should be == num_regions: %u",
 247                            name(), count, num_regions).buffer());
 248   assert(length() + num_regions == old_length,
 249          "%s", hrs_err_msg("[%s] new length should be consistent "
 250                            "new length: %u old length: %u num_regions: %u",
 251                            name(), length(), old_length, num_regions).buffer());
 252 
 253   verify_optional();
 254 }
 255 
 256 void FreeRegionList::verify() {
 257   // See comment in HeapRegionSetBase::verify() about MT safety and
 258   // verification.
 259   check_mt_safety();
 260 
 261   // This will also do the basic verification too.
 262   verify_start();
 263 
 264   verify_list();
 265 
 266   verify_end();
 267 }
 268 
 269 void FreeRegionList::clear() {
 270   _count = HeapRegionSetCount();
 271   _head = NULL;
 272   _tail = NULL;
 273   _last = NULL;
 274 }
 275 
 276 void FreeRegionList::print_on(outputStream* out, bool print_contents) {
 277   HeapRegionSetBase::print_on(out, print_contents);
 278   out->print_cr("  Linking");
 279   out->print_cr("    head              : " PTR_FORMAT, p2i(_head));
 280   out->print_cr("    tail              : " PTR_FORMAT, p2i(_tail));
 281 
 282   if (print_contents) {
 283     out->print_cr("  Contents");
 284     FreeRegionListIterator iter(this);
 285     while (iter.more_available()) {
 286       HeapRegion* hr = iter.get_next();
 287       hr->print_on(out);
 288     }
 289   }
 290 
 291   out->cr();
 292 }
 293 
 294 void FreeRegionList::verify_list() {
 295   HeapRegion* curr = _head;
 296   HeapRegion* prev1 = NULL;
 297   HeapRegion* prev0 = NULL;
 298   uint count = 0;
 299   size_t capacity = 0;
 300   uint last_index = 0;
 301 
 302   guarantee(_head == NULL || _head->prev() == NULL, "_head should not have a prev");
 303   while (curr != NULL) {
 304     verify_region(curr);
 305 
 306     count++;
 307     guarantee(count < _unrealistically_long_length,
 308         "%s", hrs_err_msg("[%s] the calculated length: %u seems very long, is there maybe a cycle? curr: " PTR_FORMAT " prev0: " PTR_FORMAT " " "prev1: " PTR_FORMAT " length: %u",
 309               name(), count, p2i(curr), p2i(prev0), p2i(prev1), length()).buffer());
 310 
 311     if (curr->next() != NULL) {
 312       guarantee(curr->next()->prev() == curr, "Next or prev pointers messed up");
 313     }
 314     guarantee(curr->hrm_index() == 0 || curr->hrm_index() > last_index, "List should be sorted");
 315     last_index = curr->hrm_index();
 316 
 317     capacity += curr->capacity();
 318 
 319     prev1 = prev0;
 320     prev0 = curr;
 321     curr = curr->next();
 322   }
 323 
 324   guarantee(_tail == prev0, "Expected %s to end with %u but it ended with %u.", name(), _tail->hrm_index(), prev0->hrm_index());
 325   guarantee(_tail == NULL || _tail->next() == NULL, "_tail should not have a next");
 326   guarantee(length() == count, "%s count mismatch. Expected %u, actual %u.", name(), length(), count);
 327   guarantee(total_capacity_bytes() == capacity, "%s capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
 328             name(), total_capacity_bytes(), capacity);
 329 }
 330 
 331 // Note on the check_mt_safety() methods below:
 332 //
 333 // Verification of the "master" heap region sets / lists that are
 334 // maintained by G1CollectedHeap is always done during a STW pause and
 335 // by the VM thread at the start / end of the pause. The standard
 336 // verification methods all assert check_mt_safety(). This is
 337 // important as it ensures that verification is done without
 338 // concurrent updates taking place at the same time. It follows, that,
 339 // for the "master" heap region sets / lists, the check_mt_safety()
 340 // method should include the VM thread / STW case.
 341 
 342 void MasterFreeRegionListMtSafeChecker::check() {
 343   // Master Free List MT safety protocol:
 344   // (a) If we're at a safepoint, operations on the master free list
 345   // should be invoked by either the VM thread (which will serialize
 346   // them) or by the GC workers while holding the
 347   // FreeList_lock.
 348   // (b) If we're not at a safepoint, operations on the master free
 349   // list should be invoked while holding the Heap_lock.
 350 
 351   if (SafepointSynchronize::is_at_safepoint()) {
 352     guarantee(Thread::current()->is_VM_thread() ||
 353               FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
 354   } else {
 355     guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
 356   }
 357 }
 358 
 359 void SecondaryFreeRegionListMtSafeChecker::check() {
 360   // Secondary Free List MT safety protocol:
 361   // Operations on the secondary free list should always be invoked
 362   // while holding the SecondaryFreeList_lock.
 363 
 364   guarantee(SecondaryFreeList_lock->owned_by_self(), "secondary free list MT safety protocol");
 365 }
 366 
 367 void OldRegionSetMtSafeChecker::check() {
 368   // Master Old Set MT safety protocol:
 369   // (a) If we're at a safepoint, operations on the master old set
 370   // should be invoked:
 371   // - by the VM thread (which will serialize them), or
 372   // - by the GC workers while holding the FreeList_lock, if we're
 373   //   at a safepoint for an evacuation pause (this lock is taken
 374   //   anyway when an GC alloc region is retired so that a new one
 375   //   is allocated from the free list), or
 376   // - by the GC workers while holding the OldSets_lock, if we're at a
 377   //   safepoint for a cleanup pause.
 378   // (b) If we're not at a safepoint, operations on the master old set
 379   // should be invoked while holding the Heap_lock.
 380 
 381   if (SafepointSynchronize::is_at_safepoint()) {
 382     guarantee(Thread::current()->is_VM_thread()
 383         || FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
 384         "master old set MT safety protocol at a safepoint");
 385   } else {
 386     guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
 387   }
 388 }
 389 
 390 void HumongousRegionSetMtSafeChecker::check() {
 391   // Humongous Set MT safety protocol:
 392   // (a) If we're at a safepoint, operations on the master humongous
 393   // set should be invoked by either the VM thread (which will
 394   // serialize them) or by the GC workers while holding the
 395   // OldSets_lock.
 396   // (b) If we're not at a safepoint, operations on the master
 397   // humongous set should be invoked while holding the Heap_lock.
 398 
 399   if (SafepointSynchronize::is_at_safepoint()) {
 400     guarantee(Thread::current()->is_VM_thread() ||
 401               OldSets_lock->owned_by_self(),
 402               "master humongous set MT safety protocol at a safepoint");
 403   } else {
 404     guarantee(Heap_lock->owned_by_self(),
 405               "master humongous set MT safety protocol outside a safepoint");
 406   }
 407 }
 408 
 409 void FreeRegionList_test() {
 410   FreeRegionList l("test");
 411 
 412   const uint num_regions_in_test = 5;
 413   // Create a fake heap. It does not need to be valid, as the HeapRegion constructor
 414   // does not access it.
 415   MemRegion heap(NULL, num_regions_in_test * HeapRegion::GrainWords);
 416   // Allocate a fake BOT because the HeapRegion constructor initializes
 417   // the BOT.
 418   size_t bot_size = G1BlockOffsetSharedArray::compute_size(heap.word_size());
 419   HeapWord* bot_data = NEW_C_HEAP_ARRAY(HeapWord, bot_size, mtGC);
 420   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(heap.word_size()));
 421   G1RegionToSpaceMapper* bot_storage =
 422     G1RegionToSpaceMapper::create_mapper(bot_rs,
 423                                          bot_rs.size(),
 424                                          os::vm_page_size(),
 425                                          HeapRegion::GrainBytes,
 426                                          G1BlockOffsetSharedArray::N_bytes,
 427                                          mtGC);
 428   G1BlockOffsetSharedArray oa(heap, bot_storage);
 429   bot_storage->commit_regions(0, num_regions_in_test);
 430 
 431   // Set up memory regions for the heap regions.
 432   MemRegion mr0(heap.start(), HeapRegion::GrainWords);
 433   MemRegion mr1(mr0.end(), HeapRegion::GrainWords);
 434   MemRegion mr2(mr1.end(), HeapRegion::GrainWords);
 435   MemRegion mr3(mr2.end(), HeapRegion::GrainWords);
 436   MemRegion mr4(mr3.end(), HeapRegion::GrainWords);
 437 
 438   HeapRegion hr0(0, &oa, mr0);
 439   HeapRegion hr1(1, &oa, mr1);
 440   HeapRegion hr2(2, &oa, mr2);
 441   HeapRegion hr3(3, &oa, mr3);
 442   HeapRegion hr4(4, &oa, mr4);
 443   l.add_ordered(&hr1);
 444   l.add_ordered(&hr0);
 445   l.add_ordered(&hr3);
 446   l.add_ordered(&hr4);
 447   l.add_ordered(&hr2);
 448   assert(l.length() == num_regions_in_test, "wrong length");
 449   l.verify_list();
 450 
 451   bot_storage->uncommit_regions(0, num_regions_in_test);
 452   delete bot_storage;
 453   FREE_C_HEAP_ARRAY(HeapWord, bot_data);
 454 }