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