1 /*
   2  * Copyright (c) 2001, 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 "code/nmethod.hpp"
  27 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
  28 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  30 #include "gc_implementation/g1/heapRegion.inline.hpp"
  31 #include "gc_implementation/g1/heapRegionBounds.inline.hpp"
  32 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  33 #include "gc_implementation/g1/heapRegionManager.inline.hpp"
  34 #include "gc_implementation/shared/liveRange.hpp"
  35 #include "memory/genOopClosures.inline.hpp"
  36 #include "memory/iterator.hpp"
  37 #include "memory/space.inline.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "runtime/orderAccess.inline.hpp"
  40 
  41 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  42 
  43 int    HeapRegion::LogOfHRGrainBytes = 0;
  44 int    HeapRegion::LogOfHRGrainWords = 0;
  45 size_t HeapRegion::GrainBytes        = 0;
  46 size_t HeapRegion::GrainWords        = 0;
  47 size_t HeapRegion::CardsPerRegion    = 0;
  48 
  49 HeapRegionDCTOC::HeapRegionDCTOC(G1CollectedHeap* g1,
  50                                  HeapRegion* hr,
  51                                  G1ParPushHeapRSClosure* cl,
  52                                  CardTableModRefBS::PrecisionStyle precision) :
  53   DirtyCardToOopClosure(hr, cl, precision, NULL),
  54   _hr(hr), _rs_scan(cl), _g1(g1) { }
  55 
  56 FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
  57                                                    OopClosure* oc) :
  58   _r_bottom(r->bottom()), _r_end(r->end()), _oc(oc) { }
  59 
  60 void HeapRegionDCTOC::walk_mem_region(MemRegion mr,
  61                                       HeapWord* bottom,
  62                                       HeapWord* top) {
  63   G1CollectedHeap* g1h = _g1;
  64   size_t oop_size;
  65   HeapWord* cur = bottom;
  66 
  67   // Start filtering what we add to the remembered set. If the object is
  68   // not considered dead, either because it is marked (in the mark bitmap)
  69   // or it was allocated after marking finished, then we add it. Otherwise
  70   // we can safely ignore the object.
  71   if (!g1h->is_obj_dead(oop(cur), _hr)) {
  72     oop_size = oop(cur)->oop_iterate(_rs_scan, mr);
  73   } else {
  74     oop_size = _hr->block_size(cur);
  75   }
  76 
  77   cur += oop_size;
  78 
  79   if (cur < top) {
  80     oop cur_oop = oop(cur);
  81     oop_size = _hr->block_size(cur);
  82     HeapWord* next_obj = cur + oop_size;
  83     while (next_obj < top) {
  84       // Keep filtering the remembered set.
  85       if (!g1h->is_obj_dead(cur_oop, _hr)) {
  86         // Bottom lies entirely below top, so we can call the
  87         // non-memRegion version of oop_iterate below.
  88         cur_oop->oop_iterate(_rs_scan);
  89       }
  90       cur = next_obj;
  91       cur_oop = oop(cur);
  92       oop_size = _hr->block_size(cur);
  93       next_obj = cur + oop_size;
  94     }
  95 
  96     // Last object. Need to do dead-obj filtering here too.
  97     if (!g1h->is_obj_dead(oop(cur), _hr)) {
  98       oop(cur)->oop_iterate(_rs_scan, mr);
  99     }
 100   }
 101 }
 102 
 103 size_t HeapRegion::max_region_size() {
 104   return HeapRegionBounds::max_size();
 105 }
 106 
 107 void HeapRegion::setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size) {
 108   uintx region_size = G1HeapRegionSize;
 109   if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
 110     size_t average_heap_size = (initial_heap_size + max_heap_size) / 2;
 111     region_size = MAX2(average_heap_size / HeapRegionBounds::target_number(),
 112                        (uintx) HeapRegionBounds::min_size());
 113   }
 114 
 115   int region_size_log = log2_long((jlong) region_size);
 116   // Recalculate the region size to make sure it's a power of
 117   // 2. This means that region_size is the largest power of 2 that's
 118   // <= what we've calculated so far.
 119   region_size = ((uintx)1 << region_size_log);
 120 
 121   // Now make sure that we don't go over or under our limits.
 122   if (region_size < HeapRegionBounds::min_size()) {
 123     region_size = HeapRegionBounds::min_size();
 124   } else if (region_size > HeapRegionBounds::max_size()) {
 125     region_size = HeapRegionBounds::max_size();
 126   }
 127 
 128   // And recalculate the log.
 129   region_size_log = log2_long((jlong) region_size);
 130 
 131   // Now, set up the globals.
 132   guarantee(LogOfHRGrainBytes == 0, "we should only set it once");
 133   LogOfHRGrainBytes = region_size_log;
 134 
 135   guarantee(LogOfHRGrainWords == 0, "we should only set it once");
 136   LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize;
 137 
 138   guarantee(GrainBytes == 0, "we should only set it once");
 139   // The cast to int is safe, given that we've bounded region_size by
 140   // MIN_REGION_SIZE and MAX_REGION_SIZE.
 141   GrainBytes = (size_t)region_size;
 142 
 143   guarantee(GrainWords == 0, "we should only set it once");
 144   GrainWords = GrainBytes >> LogHeapWordSize;
 145   guarantee((size_t) 1 << LogOfHRGrainWords == GrainWords, "sanity");
 146 
 147   guarantee(CardsPerRegion == 0, "we should only set it once");
 148   CardsPerRegion = GrainBytes >> CardTableModRefBS::card_shift;
 149 }
 150 
 151 void HeapRegion::reset_after_compaction() {
 152   G1OffsetTableContigSpace::reset_after_compaction();
 153   // After a compaction the mark bitmap is invalid, so we must
 154   // treat all objects as being inside the unmarked area.
 155   zero_marked_bytes();
 156   init_top_at_mark_start();
 157 }
 158 
 159 void HeapRegion::hr_clear(bool par, bool clear_space, bool locked) {
 160   assert(_humongous_start_region == NULL,
 161          "we should have already filtered out humongous regions");
 162   assert(_end == _orig_end,
 163          "we should have already filtered out humongous regions");
 164 
 165   _in_collection_set = false;
 166 
 167   set_allocation_context(AllocationContext::system());
 168   set_young_index_in_cset(-1);
 169   uninstall_surv_rate_group();
 170   set_free();
 171   reset_pre_dummy_top();
 172 
 173   if (!par) {
 174     // If this is parallel, this will be done later.
 175     HeapRegionRemSet* hrrs = rem_set();
 176     if (locked) {
 177       hrrs->clear_locked();
 178     } else {
 179       hrrs->clear();
 180     }
 181     _claimed = InitialClaimValue;
 182   }
 183   zero_marked_bytes();
 184 
 185   _offsets.resize(HeapRegion::GrainWords);
 186   init_top_at_mark_start();
 187   if (clear_space) clear(SpaceDecorator::Mangle);
 188 }
 189 
 190 void HeapRegion::par_clear() {
 191   assert(used() == 0, "the region should have been already cleared");
 192   assert(capacity() == HeapRegion::GrainBytes, "should be back to normal");
 193   HeapRegionRemSet* hrrs = rem_set();
 194   hrrs->clear();
 195   CardTableModRefBS* ct_bs =
 196                    (CardTableModRefBS*)G1CollectedHeap::heap()->barrier_set();
 197   ct_bs->clear(MemRegion(bottom(), end()));
 198 }
 199 
 200 void HeapRegion::calc_gc_efficiency() {
 201   // GC efficiency is the ratio of how much space would be
 202   // reclaimed over how long we predict it would take to reclaim it.
 203   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 204   G1CollectorPolicy* g1p = g1h->g1_policy();
 205 
 206   // Retrieve a prediction of the elapsed time for this region for
 207   // a mixed gc because the region will only be evacuated during a
 208   // mixed gc.
 209   double region_elapsed_time_ms =
 210     g1p->predict_region_elapsed_time_ms(this, false /* for_young_gc */);
 211   _gc_efficiency = (double) reclaimable_bytes() / region_elapsed_time_ms;
 212 }
 213 
 214 void HeapRegion::set_startsHumongous(HeapWord* new_top, HeapWord* new_end) {
 215   assert(!isHumongous(), "sanity / pre-condition");
 216   assert(end() == _orig_end,
 217          "Should be normal before the humongous object allocation");
 218   assert(top() == bottom(), "should be empty");
 219   assert(bottom() <= new_top && new_top <= new_end, "pre-condition");
 220 
 221   _type.set_starts_humongous();
 222   _humongous_start_region = this;
 223 
 224   set_end(new_end);
 225   _offsets.set_for_starts_humongous(new_top);
 226 }
 227 
 228 void HeapRegion::set_continuesHumongous(HeapRegion* first_hr) {
 229   assert(!isHumongous(), "sanity / pre-condition");
 230   assert(end() == _orig_end,
 231          "Should be normal before the humongous object allocation");
 232   assert(top() == bottom(), "should be empty");
 233   assert(first_hr->startsHumongous(), "pre-condition");
 234 
 235   _type.set_continues_humongous();
 236   _humongous_start_region = first_hr;
 237 }
 238 
 239 void HeapRegion::clear_humongous() {
 240   assert(isHumongous(), "pre-condition");
 241 
 242   if (startsHumongous()) {
 243     assert(top() <= end(), "pre-condition");
 244     set_end(_orig_end);
 245     if (top() > end()) {
 246       // at least one "continues humongous" region after it
 247       set_top(end());
 248     }
 249   } else {
 250     // continues humongous
 251     assert(end() == _orig_end, "sanity");
 252   }
 253 
 254   assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
 255   _humongous_start_region = NULL;
 256 }
 257 
 258 bool HeapRegion::claimHeapRegion(jint claimValue) {
 259   jint current = _claimed;
 260   if (current != claimValue) {
 261     jint res = Atomic::cmpxchg(claimValue, &_claimed, current);
 262     if (res == current) {
 263       return true;
 264     }
 265   }
 266   return false;
 267 }
 268 
 269 HeapRegion::HeapRegion(uint hrm_index,
 270                        G1BlockOffsetSharedArray* sharedOffsetArray,
 271                        MemRegion mr) :
 272     G1OffsetTableContigSpace(sharedOffsetArray, mr),
 273     _hrm_index(hrm_index),
 274     _allocation_context(AllocationContext::system()),
 275     _humongous_start_region(NULL),
 276     _in_collection_set(false),
 277     _next_in_special_set(NULL), _orig_end(NULL),
 278     _claimed(InitialClaimValue), _evacuation_failed(false),
 279     _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
 280     _next_young_region(NULL),
 281     _next_dirty_cards_region(NULL), _next(NULL), _prev(NULL),
 282 #ifdef ASSERT
 283     _containing_set(NULL),
 284 #endif // ASSERT
 285      _young_index_in_cset(-1), _surv_rate_group(NULL), _age_index(-1),
 286     _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0),
 287     _predicted_bytes_to_copy(0)
 288 {
 289   _rem_set = new HeapRegionRemSet(sharedOffsetArray, this);
 290   assert(HeapRegionRemSet::num_par_rem_sets() > 0, "Invariant.");
 291 
 292   initialize(mr);
 293 }
 294 
 295 void HeapRegion::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
 296   assert(_rem_set->is_empty(), "Remembered set must be empty");
 297 
 298   G1OffsetTableContigSpace::initialize(mr, clear_space, mangle_space);
 299 
 300   _orig_end = mr.end();
 301   hr_clear(false /*par*/, false /*clear_space*/);
 302   set_top(bottom());
 303   record_timestamp();
 304 }
 305 
 306 CompactibleSpace* HeapRegion::next_compaction_space() const {
 307   return G1CollectedHeap::heap()->next_compaction_region(this);
 308 }
 309 
 310 void HeapRegion::note_self_forwarding_removal_start(bool during_initial_mark,
 311                                                     bool during_conc_mark) {
 312   // We always recreate the prev marking info and we'll explicitly
 313   // mark all objects we find to be self-forwarded on the prev
 314   // bitmap. So all objects need to be below PTAMS.
 315   _prev_marked_bytes = 0;
 316 
 317   if (during_initial_mark) {
 318     // During initial-mark, we'll also explicitly mark all objects
 319     // we find to be self-forwarded on the next bitmap. So all
 320     // objects need to be below NTAMS.
 321     _next_top_at_mark_start = top();
 322     _next_marked_bytes = 0;
 323   } else if (during_conc_mark) {
 324     // During concurrent mark, all objects in the CSet (including
 325     // the ones we find to be self-forwarded) are implicitly live.
 326     // So all objects need to be above NTAMS.
 327     _next_top_at_mark_start = bottom();
 328     _next_marked_bytes = 0;
 329   }
 330 }
 331 
 332 void HeapRegion::note_self_forwarding_removal_end(bool during_initial_mark,
 333                                                   bool during_conc_mark,
 334                                                   size_t marked_bytes) {
 335   assert(0 <= marked_bytes && marked_bytes <= used(),
 336          err_msg("marked: "SIZE_FORMAT" used: "SIZE_FORMAT,
 337                  marked_bytes, used()));
 338   _prev_top_at_mark_start = top();
 339   _prev_marked_bytes = marked_bytes;
 340 }
 341 
 342 HeapWord*
 343 HeapRegion::object_iterate_mem_careful(MemRegion mr,
 344                                                  ObjectClosure* cl) {
 345   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 346   // We used to use "block_start_careful" here.  But we're actually happy
 347   // to update the BOT while we do this...
 348   HeapWord* cur = block_start(mr.start());
 349   mr = mr.intersection(used_region());
 350   if (mr.is_empty()) return NULL;
 351   // Otherwise, find the obj that extends onto mr.start().
 352 
 353   assert(cur <= mr.start()
 354          && (oop(cur)->klass_or_null() == NULL ||
 355              cur + oop(cur)->size() > mr.start()),
 356          "postcondition of block_start");
 357   oop obj;
 358   while (cur < mr.end()) {
 359     obj = oop(cur);
 360     if (obj->klass_or_null() == NULL) {
 361       // Ran into an unparseable point.
 362       return cur;
 363     } else if (!g1h->is_obj_dead(obj)) {
 364       cl->do_object(obj);
 365     }
 366     if (cl->abort()) return cur;
 367     // The check above must occur before the operation below, since an
 368     // abort might invalidate the "size" operation.
 369     cur += block_size(cur);
 370   }
 371   return NULL;
 372 }
 373 
 374 HeapWord*
 375 HeapRegion::
 376 oops_on_card_seq_iterate_careful(MemRegion mr,
 377                                  FilterOutOfRegionClosure* cl,
 378                                  bool filter_young,
 379                                  jbyte* card_ptr) {
 380   // Currently, we should only have to clean the card if filter_young
 381   // is true and vice versa.
 382   if (filter_young) {
 383     assert(card_ptr != NULL, "pre-condition");
 384   } else {
 385     assert(card_ptr == NULL, "pre-condition");
 386   }
 387   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 388 
 389   // If we're within a stop-world GC, then we might look at a card in a
 390   // GC alloc region that extends onto a GC LAB, which may not be
 391   // parseable.  Stop such at the "scan_top" of the region.
 392   if (g1h->is_gc_active()) {
 393     mr = mr.intersection(MemRegion(bottom(), scan_top()));
 394   } else {
 395     mr = mr.intersection(used_region());
 396   }
 397   if (mr.is_empty()) return NULL;
 398   // Otherwise, find the obj that extends onto mr.start().
 399 
 400   // The intersection of the incoming mr (for the card) and the
 401   // allocated part of the region is non-empty. This implies that
 402   // we have actually allocated into this region. The code in
 403   // G1CollectedHeap.cpp that allocates a new region sets the
 404   // is_young tag on the region before allocating. Thus we
 405   // safely know if this region is young.
 406   if (is_young() && filter_young) {
 407     return NULL;
 408   }
 409 
 410   assert(!is_young(), "check value of filter_young");
 411 
 412   // We can only clean the card here, after we make the decision that
 413   // the card is not young. And we only clean the card if we have been
 414   // asked to (i.e., card_ptr != NULL).
 415   if (card_ptr != NULL) {
 416     *card_ptr = CardTableModRefBS::clean_card_val();
 417     // We must complete this write before we do any of the reads below.
 418     OrderAccess::storeload();
 419   }
 420 
 421   // Cache the boundaries of the memory region in some const locals
 422   HeapWord* const start = mr.start();
 423   HeapWord* const end = mr.end();
 424 
 425   // We used to use "block_start_careful" here.  But we're actually happy
 426   // to update the BOT while we do this...
 427   HeapWord* cur = block_start(start);
 428   assert(cur <= start, "Postcondition");
 429 
 430   oop obj;
 431 
 432   HeapWord* next = cur;
 433   do {
 434     cur = next;
 435     obj = oop(cur);
 436     if (obj->klass_or_null() == NULL) {
 437       // Ran into an unparseable point.
 438       return cur;
 439     }
 440     // Otherwise...
 441     next = cur + block_size(cur);
 442   } while (next <= start);
 443 
 444   // If we finish the above loop...We have a parseable object that
 445   // begins on or before the start of the memory region, and ends
 446   // inside or spans the entire region.
 447   assert(cur <= start, "Loop postcondition");
 448   assert(obj->klass_or_null() != NULL, "Loop postcondition");
 449 
 450   do {
 451     obj = oop(cur);
 452     assert((cur + block_size(cur)) > (HeapWord*)obj, "Loop invariant");
 453     if (obj->klass_or_null() == NULL) {
 454       // Ran into an unparseable point.
 455       return cur;
 456     }
 457 
 458     // Advance the current pointer. "obj" still points to the object to iterate.
 459     cur = cur + block_size(cur);
 460 
 461     if (!g1h->is_obj_dead(obj)) {
 462       // Non-objArrays are sometimes marked imprecise at the object start. We
 463       // always need to iterate over them in full.
 464       // We only iterate over object arrays in full if they are completely contained
 465       // in the memory region.
 466       if (!obj->is_objArray() || (((HeapWord*)obj) >= start && cur <= end)) {
 467         obj->oop_iterate(cl);
 468       } else {
 469         obj->oop_iterate(cl, mr);
 470       }
 471     }
 472   } while (cur < end);
 473 
 474   return NULL;
 475 }
 476 
 477 // Code roots support
 478 
 479 void HeapRegion::add_strong_code_root(nmethod* nm) {
 480   HeapRegionRemSet* hrrs = rem_set();
 481   hrrs->add_strong_code_root(nm);
 482 }
 483 
 484 void HeapRegion::add_strong_code_root_locked(nmethod* nm) {
 485   assert_locked_or_safepoint(CodeCache_lock);
 486   HeapRegionRemSet* hrrs = rem_set();
 487   hrrs->add_strong_code_root_locked(nm);
 488 }
 489 
 490 void HeapRegion::remove_strong_code_root(nmethod* nm) {
 491   HeapRegionRemSet* hrrs = rem_set();
 492   hrrs->remove_strong_code_root(nm);
 493 }
 494 
 495 void HeapRegion::strong_code_roots_do(CodeBlobClosure* blk) const {
 496   HeapRegionRemSet* hrrs = rem_set();
 497   hrrs->strong_code_roots_do(blk);
 498 }
 499 
 500 class VerifyStrongCodeRootOopClosure: public OopClosure {
 501   const HeapRegion* _hr;
 502   nmethod* _nm;
 503   bool _failures;
 504   bool _has_oops_in_region;
 505 
 506   template <class T> void do_oop_work(T* p) {
 507     T heap_oop = oopDesc::load_heap_oop(p);
 508     if (!oopDesc::is_null(heap_oop)) {
 509       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 510 
 511       // Note: not all the oops embedded in the nmethod are in the
 512       // current region. We only look at those which are.
 513       if (_hr->is_in(obj)) {
 514         // Object is in the region. Check that its less than top
 515         if (_hr->top() <= (HeapWord*)obj) {
 516           // Object is above top
 517           gclog_or_tty->print_cr("Object "PTR_FORMAT" in region "
 518                                  "["PTR_FORMAT", "PTR_FORMAT") is above "
 519                                  "top "PTR_FORMAT,
 520                                  (void *)obj, _hr->bottom(), _hr->end(), _hr->top());
 521           _failures = true;
 522           return;
 523         }
 524         // Nmethod has at least one oop in the current region
 525         _has_oops_in_region = true;
 526       }
 527     }
 528   }
 529 
 530 public:
 531   VerifyStrongCodeRootOopClosure(const HeapRegion* hr, nmethod* nm):
 532     _hr(hr), _failures(false), _has_oops_in_region(false) {}
 533 
 534   void do_oop(narrowOop* p) { do_oop_work(p); }
 535   void do_oop(oop* p)       { do_oop_work(p); }
 536 
 537   bool failures()           { return _failures; }
 538   bool has_oops_in_region() { return _has_oops_in_region; }
 539 };
 540 
 541 class VerifyStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
 542   const HeapRegion* _hr;
 543   bool _failures;
 544 public:
 545   VerifyStrongCodeRootCodeBlobClosure(const HeapRegion* hr) :
 546     _hr(hr), _failures(false) {}
 547 
 548   void do_code_blob(CodeBlob* cb) {
 549     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
 550     if (nm != NULL) {
 551       // Verify that the nemthod is live
 552       if (!nm->is_alive()) {
 553         gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has dead nmethod "
 554                                PTR_FORMAT" in its strong code roots",
 555                                _hr->bottom(), _hr->end(), nm);
 556         _failures = true;
 557       } else {
 558         VerifyStrongCodeRootOopClosure oop_cl(_hr, nm);
 559         nm->oops_do(&oop_cl);
 560         if (!oop_cl.has_oops_in_region()) {
 561           gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has nmethod "
 562                                  PTR_FORMAT" in its strong code roots "
 563                                  "with no pointers into region",
 564                                  _hr->bottom(), _hr->end(), nm);
 565           _failures = true;
 566         } else if (oop_cl.failures()) {
 567           gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has other "
 568                                  "failures for nmethod "PTR_FORMAT,
 569                                  _hr->bottom(), _hr->end(), nm);
 570           _failures = true;
 571         }
 572       }
 573     }
 574   }
 575 
 576   bool failures()       { return _failures; }
 577 };
 578 
 579 void HeapRegion::verify_strong_code_roots(VerifyOption vo, bool* failures) const {
 580   if (!G1VerifyHeapRegionCodeRoots) {
 581     // We're not verifying code roots.
 582     return;
 583   }
 584   if (vo == VerifyOption_G1UseMarkWord) {
 585     // Marking verification during a full GC is performed after class
 586     // unloading, code cache unloading, etc so the strong code roots
 587     // attached to each heap region are in an inconsistent state. They won't
 588     // be consistent until the strong code roots are rebuilt after the
 589     // actual GC. Skip verifying the strong code roots in this particular
 590     // time.
 591     assert(VerifyDuringGC, "only way to get here");
 592     return;
 593   }
 594 
 595   HeapRegionRemSet* hrrs = rem_set();
 596   size_t strong_code_roots_length = hrrs->strong_code_roots_list_length();
 597 
 598   // if this region is empty then there should be no entries
 599   // on its strong code root list
 600   if (is_empty()) {
 601     if (strong_code_roots_length > 0) {
 602       gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is empty "
 603                              "but has "SIZE_FORMAT" code root entries",
 604                              bottom(), end(), strong_code_roots_length);
 605       *failures = true;
 606     }
 607     return;
 608   }
 609 
 610   if (continuesHumongous()) {
 611     if (strong_code_roots_length > 0) {
 612       gclog_or_tty->print_cr("region "HR_FORMAT" is a continuation of a humongous "
 613                              "region but has "SIZE_FORMAT" code root entries",
 614                              HR_FORMAT_PARAMS(this), strong_code_roots_length);
 615       *failures = true;
 616     }
 617     return;
 618   }
 619 
 620   VerifyStrongCodeRootCodeBlobClosure cb_cl(this);
 621   strong_code_roots_do(&cb_cl);
 622 
 623   if (cb_cl.failures()) {
 624     *failures = true;
 625   }
 626 }
 627 
 628 void HeapRegion::print() const { print_on(gclog_or_tty); }
 629 void HeapRegion::print_on(outputStream* st) const {
 630   st->print("AC%4u", allocation_context());
 631   st->print(" %2s", get_short_type_str());
 632   if (in_collection_set())
 633     st->print(" CS");
 634   else
 635     st->print("   ");
 636   st->print(" TS %5d", _gc_time_stamp);
 637   st->print(" PTAMS "PTR_FORMAT" NTAMS "PTR_FORMAT,
 638             prev_top_at_mark_start(), next_top_at_mark_start());
 639   G1OffsetTableContigSpace::print_on(st);
 640 }
 641 
 642 class G1VerificationClosure : public OopClosure {
 643 protected:
 644   G1CollectedHeap* _g1h;
 645   CardTableModRefBS* _bs;
 646   oop _containing_obj;
 647   bool _failures;
 648   int _n_failures;
 649   VerifyOption _vo;
 650 public:
 651   // _vo == UsePrevMarking -> use "prev" marking information,
 652   // _vo == UseNextMarking -> use "next" marking information,
 653   // _vo == UseMarkWord    -> use mark word from object header.
 654   G1VerificationClosure(G1CollectedHeap* g1h, VerifyOption vo) :
 655     _g1h(g1h), _bs(NULL), _containing_obj(NULL),
 656     _failures(false), _n_failures(0), _vo(vo)
 657   {
 658     BarrierSet* bs = _g1h->barrier_set();
 659     if (bs->is_a(BarrierSet::CardTableModRef))
 660       _bs = (CardTableModRefBS*)bs;
 661   }
 662 
 663   void set_containing_obj(oop obj) {
 664     _containing_obj = obj;
 665   }
 666 
 667   bool failures() { return _failures; }
 668   int n_failures() { return _n_failures; }
 669 
 670   void print_object(outputStream* out, oop obj) {
 671 #ifdef PRODUCT
 672     Klass* k = obj->klass();
 673     const char* class_name = InstanceKlass::cast(k)->external_name();
 674     out->print_cr("class name %s", class_name);
 675 #else // PRODUCT
 676     obj->print_on(out);
 677 #endif // PRODUCT
 678   }
 679 };
 680 
 681 class VerifyLiveClosure : public G1VerificationClosure {
 682 public:
 683   VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) : G1VerificationClosure(g1h, vo) {}
 684   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
 685   virtual void do_oop(oop* p) { do_oop_work(p); }
 686 
 687   template <class T>
 688   void do_oop_work(T* p) {
 689     assert(_containing_obj != NULL, "Precondition");
 690     assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
 691       "Precondition");
 692     verify_liveness(p);
 693   }
 694 
 695   template <class T>
 696   void verify_liveness(T* p) {
 697     T heap_oop = oopDesc::load_heap_oop(p);
 698     if (!oopDesc::is_null(heap_oop)) {
 699       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 700       bool failed = false;
 701       if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
 702         MutexLockerEx x(ParGCRareEvent_lock,
 703           Mutex::_no_safepoint_check_flag);
 704 
 705         if (!_failures) {
 706           gclog_or_tty->cr();
 707           gclog_or_tty->print_cr("----------");
 708         }
 709         if (!_g1h->is_in_closed_subset(obj)) {
 710           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 711           gclog_or_tty->print_cr("Field "PTR_FORMAT
 712                                  " of live obj "PTR_FORMAT" in region "
 713                                  "["PTR_FORMAT", "PTR_FORMAT")",
 714                                  p, (void*) _containing_obj,
 715                                  from->bottom(), from->end());
 716           print_object(gclog_or_tty, _containing_obj);
 717           gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
 718                                  (void*) obj);
 719         } else {
 720           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 721           HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
 722           gclog_or_tty->print_cr("Field "PTR_FORMAT
 723                                  " of live obj "PTR_FORMAT" in region "
 724                                  "["PTR_FORMAT", "PTR_FORMAT")",
 725                                  p, (void*) _containing_obj,
 726                                  from->bottom(), from->end());
 727           print_object(gclog_or_tty, _containing_obj);
 728           gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
 729                                  "["PTR_FORMAT", "PTR_FORMAT")",
 730                                  (void*) obj, to->bottom(), to->end());
 731           print_object(gclog_or_tty, obj);
 732         }
 733         gclog_or_tty->print_cr("----------");
 734         gclog_or_tty->flush();
 735         _failures = true;
 736         failed = true;
 737         _n_failures++;
 738       }
 739     }
 740   }
 741 };
 742 
 743 class VerifyRemSetClosure : public G1VerificationClosure {
 744 public:
 745   VerifyRemSetClosure(G1CollectedHeap* g1h, VerifyOption vo) : G1VerificationClosure(g1h, vo) {}
 746   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
 747   virtual void do_oop(oop* p) { do_oop_work(p); }
 748 
 749   template <class T>
 750   void do_oop_work(T* p) {
 751     assert(_containing_obj != NULL, "Precondition");
 752     assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
 753       "Precondition");
 754     verify_remembered_set(p);
 755   }
 756 
 757   template <class T>
 758   void verify_remembered_set(T* p) {
 759     T heap_oop = oopDesc::load_heap_oop(p);
 760     if (!oopDesc::is_null(heap_oop)) {
 761       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 762       bool failed = false;
 763       HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 764       HeapRegion* to   = _g1h->heap_region_containing(obj);
 765       if (from != NULL && to != NULL &&
 766           from != to &&
 767           !to->isHumongous()) {
 768         jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
 769         jbyte cv_field = *_bs->byte_for_const(p);
 770         const jbyte dirty = CardTableModRefBS::dirty_card_val();
 771 
 772         bool is_bad = !(from->is_young()
 773                         || to->rem_set()->contains_reference(p)
 774                         || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
 775                             (_containing_obj->is_objArray() ?
 776                                 cv_field == dirty
 777                              : cv_obj == dirty || cv_field == dirty));
 778         if (is_bad) {
 779           MutexLockerEx x(ParGCRareEvent_lock,
 780                           Mutex::_no_safepoint_check_flag);
 781 
 782           if (!_failures) {
 783             gclog_or_tty->cr();
 784             gclog_or_tty->print_cr("----------");
 785           }
 786           gclog_or_tty->print_cr("Missing rem set entry:");
 787           gclog_or_tty->print_cr("Field "PTR_FORMAT" "
 788                                  "of obj "PTR_FORMAT", "
 789                                  "in region "HR_FORMAT,
 790                                  p, (void*) _containing_obj,
 791                                  HR_FORMAT_PARAMS(from));
 792           _containing_obj->print_on(gclog_or_tty);
 793           gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
 794                                  "in region "HR_FORMAT,
 795                                  (void*) obj,
 796                                  HR_FORMAT_PARAMS(to));
 797           if (obj->is_oop()) {
 798             obj->print_on(gclog_or_tty);
 799           }
 800           gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
 801                         cv_obj, cv_field);
 802           gclog_or_tty->print_cr("----------");
 803           gclog_or_tty->flush();
 804           _failures = true;
 805           if (!failed) _n_failures++;
 806         }
 807       }
 808     }
 809   }
 810 };
 811 
 812 // This really ought to be commoned up into OffsetTableContigSpace somehow.
 813 // We would need a mechanism to make that code skip dead objects.
 814 
 815 void HeapRegion::verify(VerifyOption vo,
 816                         bool* failures) const {
 817   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 818   *failures = false;
 819   HeapWord* p = bottom();
 820   HeapWord* prev_p = NULL;
 821   VerifyLiveClosure vl_cl(g1, vo);
 822   VerifyRemSetClosure vr_cl(g1, vo);
 823   bool is_humongous = isHumongous();
 824   bool do_bot_verify = !is_young();
 825   size_t object_num = 0;
 826   while (p < top()) {
 827     oop obj = oop(p);
 828     size_t obj_size = block_size(p);
 829     object_num += 1;
 830 
 831     if (is_humongous != g1->isHumongous(obj_size) &&
 832         !g1->is_obj_dead(obj, this)) { // Dead objects may have bigger block_size since they span several objects.
 833       gclog_or_tty->print_cr("obj "PTR_FORMAT" is of %shumongous size ("
 834                              SIZE_FORMAT" words) in a %shumongous region",
 835                              p, g1->isHumongous(obj_size) ? "" : "non-",
 836                              obj_size, is_humongous ? "" : "non-");
 837        *failures = true;
 838        return;
 839     }
 840 
 841     // If it returns false, verify_for_object() will output the
 842     // appropriate message.
 843     if (do_bot_verify &&
 844         !g1->is_obj_dead(obj, this) &&
 845         !_offsets.verify_for_object(p, obj_size)) {
 846       *failures = true;
 847       return;
 848     }
 849 
 850     if (!g1->is_obj_dead_cond(obj, this, vo)) {
 851       if (obj->is_oop()) {
 852         Klass* klass = obj->klass();
 853         bool is_metaspace_object = Metaspace::contains(klass) ||
 854                                    (vo == VerifyOption_G1UsePrevMarking &&
 855                                    ClassLoaderDataGraph::unload_list_contains(klass));
 856         if (!is_metaspace_object) {
 857           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 858                                  "not metadata", klass, (void *)obj);
 859           *failures = true;
 860           return;
 861         } else if (!klass->is_klass()) {
 862           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 863                                  "not a klass", klass, (void *)obj);
 864           *failures = true;
 865           return;
 866         } else {
 867           vl_cl.set_containing_obj(obj);
 868           if (!g1->full_collection() || G1VerifyRSetsDuringFullGC) {
 869             // verify liveness and rem_set
 870             vr_cl.set_containing_obj(obj);
 871             G1Mux2Closure mux(&vl_cl, &vr_cl);
 872             obj->oop_iterate_no_header(&mux);
 873 
 874             if (vr_cl.failures()) {
 875               *failures = true;
 876             }
 877             if (G1MaxVerifyFailures >= 0 &&
 878               vr_cl.n_failures() >= G1MaxVerifyFailures) {
 879               return;
 880             }
 881           } else {
 882             // verify only liveness
 883             obj->oop_iterate_no_header(&vl_cl);
 884           }
 885           if (vl_cl.failures()) {
 886             *failures = true;
 887           }
 888           if (G1MaxVerifyFailures >= 0 &&
 889               vl_cl.n_failures() >= G1MaxVerifyFailures) {
 890             return;
 891           }
 892         }
 893       } else {
 894         gclog_or_tty->print_cr(PTR_FORMAT" not an oop", (void *)obj);
 895         *failures = true;
 896         return;
 897       }
 898     }
 899     prev_p = p;
 900     p += obj_size;
 901   }
 902 
 903   if (p != top()) {
 904     gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
 905                            "does not match top "PTR_FORMAT, p, top());
 906     *failures = true;
 907     return;
 908   }
 909 
 910   HeapWord* the_end = end();
 911   assert(p == top(), "it should still hold");
 912   // Do some extra BOT consistency checking for addresses in the
 913   // range [top, end). BOT look-ups in this range should yield
 914   // top. No point in doing that if top == end (there's nothing there).
 915   if (p < the_end) {
 916     // Look up top
 917     HeapWord* addr_1 = p;
 918     HeapWord* b_start_1 = _offsets.block_start_const(addr_1);
 919     if (b_start_1 != p) {
 920       gclog_or_tty->print_cr("BOT look up for top: "PTR_FORMAT" "
 921                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 922                              addr_1, b_start_1, p);
 923       *failures = true;
 924       return;
 925     }
 926 
 927     // Look up top + 1
 928     HeapWord* addr_2 = p + 1;
 929     if (addr_2 < the_end) {
 930       HeapWord* b_start_2 = _offsets.block_start_const(addr_2);
 931       if (b_start_2 != p) {
 932         gclog_or_tty->print_cr("BOT look up for top + 1: "PTR_FORMAT" "
 933                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 934                                addr_2, b_start_2, p);
 935         *failures = true;
 936         return;
 937       }
 938     }
 939 
 940     // Look up an address between top and end
 941     size_t diff = pointer_delta(the_end, p) / 2;
 942     HeapWord* addr_3 = p + diff;
 943     if (addr_3 < the_end) {
 944       HeapWord* b_start_3 = _offsets.block_start_const(addr_3);
 945       if (b_start_3 != p) {
 946         gclog_or_tty->print_cr("BOT look up for top + diff: "PTR_FORMAT" "
 947                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 948                                addr_3, b_start_3, p);
 949         *failures = true;
 950         return;
 951       }
 952     }
 953 
 954     // Loook up end - 1
 955     HeapWord* addr_4 = the_end - 1;
 956     HeapWord* b_start_4 = _offsets.block_start_const(addr_4);
 957     if (b_start_4 != p) {
 958       gclog_or_tty->print_cr("BOT look up for end - 1: "PTR_FORMAT" "
 959                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 960                              addr_4, b_start_4, p);
 961       *failures = true;
 962       return;
 963     }
 964   }
 965 
 966   if (is_humongous && object_num > 1) {
 967     gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
 968                            "but has "SIZE_FORMAT", objects",
 969                            bottom(), end(), object_num);
 970     *failures = true;
 971     return;
 972   }
 973 
 974   verify_strong_code_roots(vo, failures);
 975 }
 976 
 977 void HeapRegion::verify() const {
 978   bool dummy = false;
 979   verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
 980 }
 981 
 982 void HeapRegion::verify_rem_set(VerifyOption vo, bool* failures) const {
 983   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 984   *failures = false;
 985   HeapWord* p = bottom();
 986   HeapWord* prev_p = NULL;
 987   VerifyRemSetClosure vr_cl(g1, vo);
 988   while (p < top()) {
 989     oop obj = oop(p);
 990     size_t obj_size = block_size(p);
 991 
 992     if (!g1->is_obj_dead_cond(obj, this, vo)) {
 993       if (obj->is_oop()) {
 994         vr_cl.set_containing_obj(obj);
 995         obj->oop_iterate_no_header(&vr_cl);
 996 
 997         if (vr_cl.failures()) {
 998           *failures = true;
 999         }
1000         if (G1MaxVerifyFailures >= 0 &&
1001           vr_cl.n_failures() >= G1MaxVerifyFailures) {
1002           return;
1003         }
1004       } else {
1005         gclog_or_tty->print_cr(PTR_FORMAT " not an oop", p2i(obj));
1006         *failures = true;
1007         return;
1008       }
1009     }
1010 
1011     prev_p = p;
1012     p += obj_size;
1013   }
1014 }
1015 
1016 void HeapRegion::verify_rem_set() const {
1017   bool failures = false;
1018   verify_rem_set(VerifyOption_G1UsePrevMarking, &failures);
1019   guarantee(!failures, "HeapRegion RemSet verification failed");
1020 }
1021 
1022 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
1023 // away eventually.
1024 
1025 void G1OffsetTableContigSpace::clear(bool mangle_space) {
1026   set_top(bottom());
1027   _scan_top = bottom();
1028   CompactibleSpace::clear(mangle_space);
1029   reset_bot();
1030 }
1031 
1032 void G1OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
1033   Space::set_bottom(new_bottom);
1034   _offsets.set_bottom(new_bottom);
1035 }
1036 
1037 void G1OffsetTableContigSpace::set_end(HeapWord* new_end) {
1038   Space::set_end(new_end);
1039   _offsets.resize(new_end - bottom());
1040 }
1041 
1042 void G1OffsetTableContigSpace::print() const {
1043   print_short();
1044   gclog_or_tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
1045                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
1046                 bottom(), top(), _offsets.threshold(), end());
1047 }
1048 
1049 HeapWord* G1OffsetTableContigSpace::initialize_threshold() {
1050   return _offsets.initialize_threshold();
1051 }
1052 
1053 HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
1054                                                     HeapWord* end) {
1055   _offsets.alloc_block(start, end);
1056   return _offsets.threshold();
1057 }
1058 
1059 HeapWord* G1OffsetTableContigSpace::scan_top() const {
1060   G1CollectedHeap* g1h = G1CollectedHeap::heap();
1061   HeapWord* local_top = top();
1062   OrderAccess::loadload();
1063   const unsigned local_time_stamp = _gc_time_stamp;
1064   assert(local_time_stamp <= g1h->get_gc_time_stamp(), "invariant");
1065   if (local_time_stamp < g1h->get_gc_time_stamp()) {
1066     return local_top;
1067   } else {
1068     return _scan_top;
1069   }
1070 }
1071 
1072 void G1OffsetTableContigSpace::record_timestamp() {
1073   G1CollectedHeap* g1h = G1CollectedHeap::heap();
1074   unsigned curr_gc_time_stamp = g1h->get_gc_time_stamp();
1075 
1076   if (_gc_time_stamp < curr_gc_time_stamp) {
1077     // Setting the time stamp here tells concurrent readers to look at
1078     // scan_top to know the maximum allowed address to look at.
1079 
1080     // scan_top should be bottom for all regions except for the
1081     // retained old alloc region which should have scan_top == top
1082     HeapWord* st = _scan_top;
1083     guarantee(st == _bottom || st == _top, "invariant");
1084 
1085     _gc_time_stamp = curr_gc_time_stamp;
1086   }
1087 }
1088 
1089 void G1OffsetTableContigSpace::record_retained_region() {
1090   // scan_top is the maximum address where it's safe for the next gc to
1091   // scan this region.
1092   _scan_top = top();
1093 }
1094 
1095 void G1OffsetTableContigSpace::safe_object_iterate(ObjectClosure* blk) {
1096   object_iterate(blk);
1097 }
1098 
1099 void G1OffsetTableContigSpace::object_iterate(ObjectClosure* blk) {
1100   HeapWord* p = bottom();
1101   while (p < top()) {
1102     if (block_is_obj(p)) {
1103       blk->do_object(oop(p));
1104     }
1105     p += block_size(p);
1106   }
1107 }
1108 
1109 #define block_is_always_obj(q) true
1110 void G1OffsetTableContigSpace::prepare_for_compaction(CompactPoint* cp) {
1111   SCAN_AND_FORWARD(cp, top, block_is_always_obj, block_size);
1112 }
1113 #undef block_is_always_obj
1114 
1115 G1OffsetTableContigSpace::
1116 G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
1117                          MemRegion mr) :
1118   _offsets(sharedOffsetArray, mr),
1119   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
1120   _gc_time_stamp(0)
1121 {
1122   _offsets.set_space(this);
1123 }
1124 
1125 void G1OffsetTableContigSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
1126   CompactibleSpace::initialize(mr, clear_space, mangle_space);
1127   _top = bottom();
1128   _scan_top = bottom();
1129   set_saved_mark_word(NULL);
1130   reset_bot();
1131 }
1132