1 /*
   2  * Copyright (c) 2001, 2013, 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/heapRegionRemSet.hpp"
  32 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  33 #include "memory/genOopClosures.inline.hpp"
  34 #include "memory/iterator.hpp"
  35 #include "oops/oop.inline.hpp"
  36 
  37 int    HeapRegion::LogOfHRGrainBytes = 0;
  38 int    HeapRegion::LogOfHRGrainWords = 0;
  39 size_t HeapRegion::GrainBytes        = 0;
  40 size_t HeapRegion::GrainWords        = 0;
  41 size_t HeapRegion::CardsPerRegion    = 0;
  42 
  43 HeapRegionDCTOC::HeapRegionDCTOC(G1CollectedHeap* g1,
  44                                  HeapRegion* hr, ExtendedOopClosure* cl,
  45                                  CardTableModRefBS::PrecisionStyle precision,
  46                                  FilterKind fk) :
  47   ContiguousSpaceDCTOC(hr, cl, precision, NULL),
  48   _hr(hr), _fk(fk), _g1(g1) { }
  49 
  50 FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
  51                                                    OopClosure* oc) :
  52   _r_bottom(r->bottom()), _r_end(r->end()), _oc(oc) { }
  53 
  54 template<class ClosureType>
  55 HeapWord* walk_mem_region_loop(ClosureType* cl, G1CollectedHeap* g1h,
  56                                HeapRegion* hr,
  57                                HeapWord* cur, HeapWord* top) {
  58   oop cur_oop = oop(cur);
  59   int oop_size = cur_oop->size();
  60   HeapWord* next_obj = cur + oop_size;
  61   while (next_obj < top) {
  62     // Keep filtering the remembered set.
  63     if (!g1h->is_obj_dead(cur_oop, hr)) {
  64       // Bottom lies entirely below top, so we can call the
  65       // non-memRegion version of oop_iterate below.
  66       cur_oop->oop_iterate(cl);
  67     }
  68     cur = next_obj;
  69     cur_oop = oop(cur);
  70     oop_size = cur_oop->size();
  71     next_obj = cur + oop_size;
  72   }
  73   return cur;
  74 }
  75 
  76 void HeapRegionDCTOC::walk_mem_region_with_cl(MemRegion mr,
  77                                               HeapWord* bottom,
  78                                               HeapWord* top,
  79                                               ExtendedOopClosure* cl) {
  80   G1CollectedHeap* g1h = _g1;
  81   int oop_size;
  82   ExtendedOopClosure* cl2 = NULL;
  83 
  84   FilterIntoCSClosure intoCSFilt(this, g1h, cl);
  85   FilterOutOfRegionClosure outOfRegionFilt(_hr, cl);
  86 
  87   switch (_fk) {
  88   case NoFilterKind:          cl2 = cl; break;
  89   case IntoCSFilterKind:      cl2 = &intoCSFilt; break;
  90   case OutOfRegionFilterKind: cl2 = &outOfRegionFilt; break;
  91   default:                    ShouldNotReachHere();
  92   }
  93 
  94   // Start filtering what we add to the remembered set. If the object is
  95   // not considered dead, either because it is marked (in the mark bitmap)
  96   // or it was allocated after marking finished, then we add it. Otherwise
  97   // we can safely ignore the object.
  98   if (!g1h->is_obj_dead(oop(bottom), _hr)) {
  99     oop_size = oop(bottom)->oop_iterate(cl2, mr);
 100   } else {
 101     oop_size = oop(bottom)->size();
 102   }
 103 
 104   bottom += oop_size;
 105 
 106   if (bottom < top) {
 107     // We replicate the loop below for several kinds of possible filters.
 108     switch (_fk) {
 109     case NoFilterKind:
 110       bottom = walk_mem_region_loop(cl, g1h, _hr, bottom, top);
 111       break;
 112 
 113     case IntoCSFilterKind: {
 114       FilterIntoCSClosure filt(this, g1h, cl);
 115       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
 116       break;
 117     }
 118 
 119     case OutOfRegionFilterKind: {
 120       FilterOutOfRegionClosure filt(_hr, cl);
 121       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
 122       break;
 123     }
 124 
 125     default:
 126       ShouldNotReachHere();
 127     }
 128 
 129     // Last object. Need to do dead-obj filtering here too.
 130     if (!g1h->is_obj_dead(oop(bottom), _hr)) {
 131       oop(bottom)->oop_iterate(cl2, mr);
 132     }
 133   }
 134 }
 135 
 136 // Minimum region size; we won't go lower than that.
 137 // We might want to decrease this in the future, to deal with small
 138 // heaps a bit more efficiently.
 139 #define MIN_REGION_SIZE  (      1024 * 1024 )
 140 
 141 // Maximum region size; we don't go higher than that. There's a good
 142 // reason for having an upper bound. We don't want regions to get too
 143 // large, otherwise cleanup's effectiveness would decrease as there
 144 // will be fewer opportunities to find totally empty regions after
 145 // marking.
 146 #define MAX_REGION_SIZE  ( 32 * 1024 * 1024 )
 147 
 148 // The automatic region size calculation will try to have around this
 149 // many regions in the heap (based on the min heap size).
 150 #define TARGET_REGION_NUMBER          2048
 151 
 152 size_t HeapRegion::max_region_size() {
 153   return (size_t)MAX_REGION_SIZE;
 154 }
 155 
 156 void HeapRegion::setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size) {
 157   uintx region_size = G1HeapRegionSize;
 158   if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
 159     size_t average_heap_size = (initial_heap_size + max_heap_size) / 2;
 160     region_size = MAX2(average_heap_size / TARGET_REGION_NUMBER,
 161                        (uintx) MIN_REGION_SIZE);
 162   }
 163 
 164   int region_size_log = log2_long((jlong) region_size);
 165   // Recalculate the region size to make sure it's a power of
 166   // 2. This means that region_size is the largest power of 2 that's
 167   // <= what we've calculated so far.
 168   region_size = ((uintx)1 << region_size_log);
 169 
 170   // Now make sure that we don't go over or under our limits.
 171   if (region_size < MIN_REGION_SIZE) {
 172     region_size = MIN_REGION_SIZE;
 173   } else if (region_size > MAX_REGION_SIZE) {
 174     region_size = MAX_REGION_SIZE;
 175   }
 176 
 177   // And recalculate the log.
 178   region_size_log = log2_long((jlong) region_size);
 179 
 180   // Now, set up the globals.
 181   guarantee(LogOfHRGrainBytes == 0, "we should only set it once");
 182   LogOfHRGrainBytes = region_size_log;
 183 
 184   guarantee(LogOfHRGrainWords == 0, "we should only set it once");
 185   LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize;
 186 
 187   guarantee(GrainBytes == 0, "we should only set it once");
 188   // The cast to int is safe, given that we've bounded region_size by
 189   // MIN_REGION_SIZE and MAX_REGION_SIZE.
 190   GrainBytes = (size_t)region_size;
 191 
 192   guarantee(GrainWords == 0, "we should only set it once");
 193   GrainWords = GrainBytes >> LogHeapWordSize;
 194   guarantee((size_t) 1 << LogOfHRGrainWords == GrainWords, "sanity");
 195 
 196   guarantee(CardsPerRegion == 0, "we should only set it once");
 197   CardsPerRegion = GrainBytes >> CardTableModRefBS::card_shift;
 198 }
 199 
 200 void HeapRegion::reset_after_compaction() {
 201   G1OffsetTableContigSpace::reset_after_compaction();
 202   // After a compaction the mark bitmap is invalid, so we must
 203   // treat all objects as being inside the unmarked area.
 204   zero_marked_bytes();
 205   init_top_at_mark_start();
 206 }
 207 
 208 void HeapRegion::hr_clear(bool par, bool clear_space) {
 209   assert(_humongous_type == NotHumongous,
 210          "we should have already filtered out humongous regions");
 211   assert(_humongous_start_region == NULL,
 212          "we should have already filtered out humongous regions");
 213   assert(_end == _orig_end,
 214          "we should have already filtered out humongous regions");
 215 
 216   _in_collection_set = false;
 217 
 218   set_young_index_in_cset(-1);
 219   uninstall_surv_rate_group();
 220   set_young_type(NotYoung);
 221   reset_pre_dummy_top();
 222 
 223   if (!par) {
 224     // If this is parallel, this will be done later.
 225     HeapRegionRemSet* hrrs = rem_set();
 226     hrrs->clear();
 227     _claimed = InitialClaimValue;
 228   }
 229   zero_marked_bytes();
 230 
 231   _offsets.resize(HeapRegion::GrainWords);
 232   init_top_at_mark_start();
 233   if (clear_space) clear(SpaceDecorator::Mangle);
 234 }
 235 
 236 void HeapRegion::par_clear() {
 237   assert(used() == 0, "the region should have been already cleared");
 238   assert(capacity() == HeapRegion::GrainBytes, "should be back to normal");
 239   HeapRegionRemSet* hrrs = rem_set();
 240   hrrs->clear();
 241   CardTableModRefBS* ct_bs =
 242                    (CardTableModRefBS*)G1CollectedHeap::heap()->barrier_set();
 243   ct_bs->clear(MemRegion(bottom(), end()));
 244 }
 245 
 246 void HeapRegion::calc_gc_efficiency() {
 247   // GC efficiency is the ratio of how much space would be
 248   // reclaimed over how long we predict it would take to reclaim it.
 249   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 250   G1CollectorPolicy* g1p = g1h->g1_policy();
 251 
 252   // Retrieve a prediction of the elapsed time for this region for
 253   // a mixed gc because the region will only be evacuated during a
 254   // mixed gc.
 255   double region_elapsed_time_ms =
 256     g1p->predict_region_elapsed_time_ms(this, false /* for_young_gc */);
 257   _gc_efficiency = (double) reclaimable_bytes() / region_elapsed_time_ms;
 258 }
 259 
 260 void HeapRegion::set_startsHumongous(HeapWord* new_top, HeapWord* new_end) {
 261   assert(!isHumongous(), "sanity / pre-condition");
 262   assert(end() == _orig_end,
 263          "Should be normal before the humongous object allocation");
 264   assert(top() == bottom(), "should be empty");
 265   assert(bottom() <= new_top && new_top <= new_end, "pre-condition");
 266 
 267   _humongous_type = StartsHumongous;
 268   _humongous_start_region = this;
 269 
 270   set_end(new_end);
 271   _offsets.set_for_starts_humongous(new_top);
 272 }
 273 
 274 void HeapRegion::set_continuesHumongous(HeapRegion* first_hr) {
 275   assert(!isHumongous(), "sanity / pre-condition");
 276   assert(end() == _orig_end,
 277          "Should be normal before the humongous object allocation");
 278   assert(top() == bottom(), "should be empty");
 279   assert(first_hr->startsHumongous(), "pre-condition");
 280 
 281   _humongous_type = ContinuesHumongous;
 282   _humongous_start_region = first_hr;
 283 }
 284 
 285 void HeapRegion::set_notHumongous() {
 286   assert(isHumongous(), "pre-condition");
 287 
 288   if (startsHumongous()) {
 289     assert(top() <= end(), "pre-condition");
 290     set_end(_orig_end);
 291     if (top() > end()) {
 292       // at least one "continues humongous" region after it
 293       set_top(end());
 294     }
 295   } else {
 296     // continues humongous
 297     assert(end() == _orig_end, "sanity");
 298   }
 299 
 300   assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
 301   _humongous_type = NotHumongous;
 302   _humongous_start_region = NULL;
 303 }
 304 
 305 bool HeapRegion::claimHeapRegion(jint claimValue) {
 306   jint current = _claimed;
 307   if (current != claimValue) {
 308     jint res = Atomic::cmpxchg(claimValue, &_claimed, current);
 309     if (res == current) {
 310       return true;
 311     }
 312   }
 313   return false;
 314 }
 315 
 316 HeapWord* HeapRegion::next_block_start_careful(HeapWord* addr) {
 317   HeapWord* low = addr;
 318   HeapWord* high = end();
 319   while (low < high) {
 320     size_t diff = pointer_delta(high, low);
 321     // Must add one below to bias toward the high amount.  Otherwise, if
 322   // "high" were at the desired value, and "low" were one less, we
 323     // would not converge on "high".  This is not symmetric, because
 324     // we set "high" to a block start, which might be the right one,
 325     // which we don't do for "low".
 326     HeapWord* middle = low + (diff+1)/2;
 327     if (middle == high) return high;
 328     HeapWord* mid_bs = block_start_careful(middle);
 329     if (mid_bs < addr) {
 330       low = middle;
 331     } else {
 332       high = mid_bs;
 333     }
 334   }
 335   assert(low == high && low >= addr, "Didn't work.");
 336   return low;
 337 }
 338 
 339 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 340 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 341 #endif // _MSC_VER
 342 
 343 
 344 HeapRegion::HeapRegion(uint hrs_index,
 345                        G1BlockOffsetSharedArray* sharedOffsetArray,
 346                        MemRegion mr) :
 347     G1OffsetTableContigSpace(sharedOffsetArray, mr),
 348     _hrs_index(hrs_index),
 349     _humongous_type(NotHumongous), _humongous_start_region(NULL),
 350     _in_collection_set(false),
 351     _next_in_special_set(NULL), _orig_end(NULL),
 352     _claimed(InitialClaimValue), _evacuation_failed(false),
 353     _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
 354     _young_type(NotYoung), _next_young_region(NULL),
 355     _next_dirty_cards_region(NULL), _next(NULL), _pending_removal(false),
 356 #ifdef ASSERT
 357     _containing_set(NULL),
 358 #endif // ASSERT
 359      _young_index_in_cset(-1), _surv_rate_group(NULL), _age_index(-1),
 360     _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0),
 361     _predicted_bytes_to_copy(0)
 362 {
 363   _rem_set = new HeapRegionRemSet(sharedOffsetArray, this);
 364   _orig_end = mr.end();
 365   // Note that initialize() will set the start of the unmarked area of the
 366   // region.
 367   hr_clear(false /*par*/, false /*clear_space*/);
 368   set_top(bottom());
 369   set_saved_mark();
 370 
 371   assert(HeapRegionRemSet::num_par_rem_sets() > 0, "Invariant.");
 372 }
 373 
 374 CompactibleSpace* HeapRegion::next_compaction_space() const {
 375   // We're not using an iterator given that it will wrap around when
 376   // it reaches the last region and this is not what we want here.
 377   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 378   uint index = hrs_index() + 1;
 379   while (index < g1h->n_regions()) {
 380     HeapRegion* hr = g1h->region_at(index);
 381     if (!hr->isHumongous()) {
 382       return hr;
 383     }
 384     index += 1;
 385   }
 386   return NULL;
 387 }
 388 
 389 void HeapRegion::save_marks() {
 390   set_saved_mark();
 391 }
 392 
 393 void HeapRegion::oops_in_mr_iterate(MemRegion mr, ExtendedOopClosure* cl) {
 394   HeapWord* p = mr.start();
 395   HeapWord* e = mr.end();
 396   oop obj;
 397   while (p < e) {
 398     obj = oop(p);
 399     p += obj->oop_iterate(cl);
 400   }
 401   assert(p == e, "bad memregion: doesn't end on obj boundary");
 402 }
 403 
 404 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 405 void HeapRegion::oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
 406   ContiguousSpace::oop_since_save_marks_iterate##nv_suffix(cl);              \
 407 }
 408 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN)
 409 
 410 
 411 void HeapRegion::oop_before_save_marks_iterate(ExtendedOopClosure* cl) {
 412   oops_in_mr_iterate(MemRegion(bottom(), saved_mark_word()), cl);
 413 }
 414 
 415 void HeapRegion::note_self_forwarding_removal_start(bool during_initial_mark,
 416                                                     bool during_conc_mark) {
 417   // We always recreate the prev marking info and we'll explicitly
 418   // mark all objects we find to be self-forwarded on the prev
 419   // bitmap. So all objects need to be below PTAMS.
 420   _prev_top_at_mark_start = top();
 421   _prev_marked_bytes = 0;
 422 
 423   if (during_initial_mark) {
 424     // During initial-mark, we'll also explicitly mark all objects
 425     // we find to be self-forwarded on the next bitmap. So all
 426     // objects need to be below NTAMS.
 427     _next_top_at_mark_start = top();
 428     _next_marked_bytes = 0;
 429   } else if (during_conc_mark) {
 430     // During concurrent mark, all objects in the CSet (including
 431     // the ones we find to be self-forwarded) are implicitly live.
 432     // So all objects need to be above NTAMS.
 433     _next_top_at_mark_start = bottom();
 434     _next_marked_bytes = 0;
 435   }
 436 }
 437 
 438 void HeapRegion::note_self_forwarding_removal_end(bool during_initial_mark,
 439                                                   bool during_conc_mark,
 440                                                   size_t marked_bytes) {
 441   assert(0 <= marked_bytes && marked_bytes <= used(),
 442          err_msg("marked: "SIZE_FORMAT" used: "SIZE_FORMAT,
 443                  marked_bytes, used()));
 444   _prev_marked_bytes = marked_bytes;
 445 }
 446 
 447 HeapWord*
 448 HeapRegion::object_iterate_mem_careful(MemRegion mr,
 449                                                  ObjectClosure* cl) {
 450   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 451   // We used to use "block_start_careful" here.  But we're actually happy
 452   // to update the BOT while we do this...
 453   HeapWord* cur = block_start(mr.start());
 454   mr = mr.intersection(used_region());
 455   if (mr.is_empty()) return NULL;
 456   // Otherwise, find the obj that extends onto mr.start().
 457 
 458   assert(cur <= mr.start()
 459          && (oop(cur)->klass_or_null() == NULL ||
 460              cur + oop(cur)->size() > mr.start()),
 461          "postcondition of block_start");
 462   oop obj;
 463   while (cur < mr.end()) {
 464     obj = oop(cur);
 465     if (obj->klass_or_null() == NULL) {
 466       // Ran into an unparseable point.
 467       return cur;
 468     } else if (!g1h->is_obj_dead(obj)) {
 469       cl->do_object(obj);
 470     }
 471     if (cl->abort()) return cur;
 472     // The check above must occur before the operation below, since an
 473     // abort might invalidate the "size" operation.
 474     cur += obj->size();
 475   }
 476   return NULL;
 477 }
 478 
 479 HeapWord*
 480 HeapRegion::
 481 oops_on_card_seq_iterate_careful(MemRegion mr,
 482                                  FilterOutOfRegionClosure* cl,
 483                                  bool filter_young,
 484                                  jbyte* card_ptr) {
 485   // Currently, we should only have to clean the card if filter_young
 486   // is true and vice versa.
 487   if (filter_young) {
 488     assert(card_ptr != NULL, "pre-condition");
 489   } else {
 490     assert(card_ptr == NULL, "pre-condition");
 491   }
 492   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 493 
 494   // If we're within a stop-world GC, then we might look at a card in a
 495   // GC alloc region that extends onto a GC LAB, which may not be
 496   // parseable.  Stop such at the "saved_mark" of the region.
 497   if (g1h->is_gc_active()) {
 498     mr = mr.intersection(used_region_at_save_marks());
 499   } else {
 500     mr = mr.intersection(used_region());
 501   }
 502   if (mr.is_empty()) return NULL;
 503   // Otherwise, find the obj that extends onto mr.start().
 504 
 505   // The intersection of the incoming mr (for the card) and the
 506   // allocated part of the region is non-empty. This implies that
 507   // we have actually allocated into this region. The code in
 508   // G1CollectedHeap.cpp that allocates a new region sets the
 509   // is_young tag on the region before allocating. Thus we
 510   // safely know if this region is young.
 511   if (is_young() && filter_young) {
 512     return NULL;
 513   }
 514 
 515   assert(!is_young(), "check value of filter_young");
 516 
 517   // We can only clean the card here, after we make the decision that
 518   // the card is not young. And we only clean the card if we have been
 519   // asked to (i.e., card_ptr != NULL).
 520   if (card_ptr != NULL) {
 521     *card_ptr = CardTableModRefBS::clean_card_val();
 522     // We must complete this write before we do any of the reads below.
 523     OrderAccess::storeload();
 524   }
 525 
 526   // Cache the boundaries of the memory region in some const locals
 527   HeapWord* const start = mr.start();
 528   HeapWord* const end = mr.end();
 529 
 530   // We used to use "block_start_careful" here.  But we're actually happy
 531   // to update the BOT while we do this...
 532   HeapWord* cur = block_start(start);
 533   assert(cur <= start, "Postcondition");
 534 
 535   oop obj;
 536 
 537   HeapWord* next = cur;
 538   while (next <= start) {
 539     cur = next;
 540     obj = oop(cur);
 541     if (obj->klass_or_null() == NULL) {
 542       // Ran into an unparseable point.
 543       return cur;
 544     }
 545     // Otherwise...
 546     next = (cur + obj->size());
 547   }
 548 
 549   // If we finish the above loop...We have a parseable object that
 550   // begins on or before the start of the memory region, and ends
 551   // inside or spans the entire region.
 552 
 553   assert(obj == oop(cur), "sanity");
 554   assert(cur <= start &&
 555          obj->klass_or_null() != NULL &&
 556          (cur + obj->size()) > start,
 557          "Loop postcondition");
 558 
 559   if (!g1h->is_obj_dead(obj)) {
 560     obj->oop_iterate(cl, mr);
 561   }
 562 
 563   while (cur < end) {
 564     obj = oop(cur);
 565     if (obj->klass_or_null() == NULL) {
 566       // Ran into an unparseable point.
 567       return cur;
 568     };
 569 
 570     // Otherwise:
 571     next = (cur + obj->size());
 572 
 573     if (!g1h->is_obj_dead(obj)) {
 574       if (next < end || !obj->is_objArray()) {
 575         // This object either does not span the MemRegion
 576         // boundary, or if it does it's not an array.
 577         // Apply closure to whole object.
 578         obj->oop_iterate(cl);
 579       } else {
 580         // This obj is an array that spans the boundary.
 581         // Stop at the boundary.
 582         obj->oop_iterate(cl, mr);
 583       }
 584     }
 585     cur = next;
 586   }
 587   return NULL;
 588 }
 589 
 590 // Code roots support
 591 
 592 void HeapRegion::add_strong_code_root(nmethod* nm) {
 593   HeapRegionRemSet* hrrs = rem_set();
 594   hrrs->add_strong_code_root(nm);
 595 }
 596 
 597 void HeapRegion::remove_strong_code_root(nmethod* nm) {
 598   HeapRegionRemSet* hrrs = rem_set();
 599   hrrs->remove_strong_code_root(nm);
 600 }
 601 
 602 void HeapRegion::migrate_strong_code_roots() {
 603   assert(in_collection_set(), "only collection set regions");
 604   assert(!isHumongous(), "humongous region moved?");
 605 
 606   HeapRegionRemSet* hrrs = rem_set();
 607   hrrs->migrate_strong_code_roots();
 608 }
 609 
 610 void HeapRegion::strong_code_roots_do(CodeBlobClosure* blk) const {
 611   HeapRegionRemSet* hrrs = rem_set();
 612   hrrs->strong_code_roots_do(blk);
 613 }
 614 
 615 class VerifyStrongCodeRootOopClosure: public OopClosure {
 616   const HeapRegion* _hr;
 617   nmethod* _nm;
 618   bool _failures;
 619   bool _has_oops_in_region;
 620 
 621   template <class T> void do_oop_work(T* p) {
 622     T heap_oop = oopDesc::load_heap_oop(p);
 623     if (!oopDesc::is_null(heap_oop)) {
 624       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 625 
 626       // Note: not all the oops embedded in the nmethod are in the
 627       // current region. We only look at those which are.
 628       if (_hr->is_in(obj)) {
 629         // Object is in the region. Check that its less than top
 630         if (_hr->top() <= (HeapWord*)obj) {
 631           // Object is above top
 632           gclog_or_tty->print_cr("Object "PTR_FORMAT" in region "
 633                                  "["PTR_FORMAT", "PTR_FORMAT") is above "
 634                                  "top "PTR_FORMAT,
 635                                  (void *)obj, _hr->bottom(), _hr->end(), _hr->top());
 636           _failures = true;
 637           return;
 638         }
 639         // Nmethod has at least one oop in the current region
 640         _has_oops_in_region = true;
 641       }
 642     }
 643   }
 644 
 645 public:
 646   VerifyStrongCodeRootOopClosure(const HeapRegion* hr, nmethod* nm):
 647     _hr(hr), _failures(false), _has_oops_in_region(false) {}
 648 
 649   void do_oop(narrowOop* p) { do_oop_work(p); }
 650   void do_oop(oop* p)       { do_oop_work(p); }
 651 
 652   bool failures()           { return _failures; }
 653   bool has_oops_in_region() { return _has_oops_in_region; }
 654 };
 655 
 656 class VerifyStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
 657   const HeapRegion* _hr;
 658   bool _failures;
 659 public:
 660   VerifyStrongCodeRootCodeBlobClosure(const HeapRegion* hr) :
 661     _hr(hr), _failures(false) {}
 662 
 663   void do_code_blob(CodeBlob* cb) {
 664     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
 665     if (nm != NULL) {
 666       // Verify that the nemthod is live
 667       if (!nm->is_alive()) {
 668         gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has dead nmethod "
 669                                PTR_FORMAT" in its strong code roots",
 670                                _hr->bottom(), _hr->end(), nm);
 671         _failures = true;
 672       } else {
 673         VerifyStrongCodeRootOopClosure oop_cl(_hr, nm);
 674         nm->oops_do(&oop_cl);
 675         if (!oop_cl.has_oops_in_region()) {
 676           gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has nmethod "
 677                                  PTR_FORMAT" in its strong code roots "
 678                                  "with no pointers into region",
 679                                  _hr->bottom(), _hr->end(), nm);
 680           _failures = true;
 681         } else if (oop_cl.failures()) {
 682           gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has other "
 683                                  "failures for nmethod "PTR_FORMAT,
 684                                  _hr->bottom(), _hr->end(), nm);
 685           _failures = true;
 686         }
 687       }
 688     }
 689   }
 690 
 691   bool failures()       { return _failures; }
 692 };
 693 
 694 void HeapRegion::verify_strong_code_roots(VerifyOption vo, bool* failures) const {
 695   if (!G1VerifyHeapRegionCodeRoots) {
 696     // We're not verifying code roots.
 697     return;
 698   }
 699   if (vo == VerifyOption_G1UseMarkWord) {
 700     // Marking verification during a full GC is performed after class
 701     // unloading, code cache unloading, etc so the strong code roots
 702     // attached to each heap region are in an inconsistent state. They won't
 703     // be consistent until the strong code roots are rebuilt after the
 704     // actual GC. Skip verifying the strong code roots in this particular
 705     // time.
 706     assert(VerifyDuringGC, "only way to get here");
 707     return;
 708   }
 709 
 710   HeapRegionRemSet* hrrs = rem_set();
 711   int strong_code_roots_length = hrrs->strong_code_roots_list_length();
 712 
 713   // if this region is empty then there should be no entries
 714   // on its strong code root list
 715   if (is_empty()) {
 716     if (strong_code_roots_length > 0) {
 717       gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is empty "
 718                              "but has "INT32_FORMAT" code root entries",
 719                              bottom(), end(), strong_code_roots_length);
 720       *failures = true;
 721     }
 722     return;
 723   }
 724 
 725   // An H-region continuation should have an empty strong code root list
 726   if (continuesHumongous()) {
 727     if (strong_code_roots_length > 0) {
 728       gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is a humongous continuation "
 729                              "but has "INT32_FORMAT" code root entries",
 730                              bottom(), end(), strong_code_roots_length);
 731       *failures = true;
 732     }
 733     return;
 734   }
 735 
 736   VerifyStrongCodeRootCodeBlobClosure cb_cl(this);
 737   strong_code_roots_do(&cb_cl);
 738 
 739   if (cb_cl.failures()) {
 740     *failures = true;
 741   }
 742 }
 743 
 744 void HeapRegion::print() const { print_on(gclog_or_tty); }
 745 void HeapRegion::print_on(outputStream* st) const {
 746   if (isHumongous()) {
 747     if (startsHumongous())
 748       st->print(" HS");
 749     else
 750       st->print(" HC");
 751   } else {
 752     st->print("   ");
 753   }
 754   if (in_collection_set())
 755     st->print(" CS");
 756   else
 757     st->print("   ");
 758   if (is_young())
 759     st->print(is_survivor() ? " SU" : " Y ");
 760   else
 761     st->print("   ");
 762   if (is_empty())
 763     st->print(" F");
 764   else
 765     st->print("  ");
 766   st->print(" TS %5d", _gc_time_stamp);
 767   st->print(" PTAMS "PTR_FORMAT" NTAMS "PTR_FORMAT,
 768             prev_top_at_mark_start(), next_top_at_mark_start());
 769   G1OffsetTableContigSpace::print_on(st);
 770 }
 771 
 772 class VerifyLiveClosure: public OopClosure {
 773 private:
 774   G1CollectedHeap* _g1h;
 775   CardTableModRefBS* _bs;
 776   oop _containing_obj;
 777   bool _failures;
 778   int _n_failures;
 779   VerifyOption _vo;
 780 public:
 781   // _vo == UsePrevMarking -> use "prev" marking information,
 782   // _vo == UseNextMarking -> use "next" marking information,
 783   // _vo == UseMarkWord    -> use mark word from object header.
 784   VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
 785     _g1h(g1h), _bs(NULL), _containing_obj(NULL),
 786     _failures(false), _n_failures(0), _vo(vo)
 787   {
 788     BarrierSet* bs = _g1h->barrier_set();
 789     if (bs->is_a(BarrierSet::CardTableModRef))
 790       _bs = (CardTableModRefBS*)bs;
 791   }
 792 
 793   void set_containing_obj(oop obj) {
 794     _containing_obj = obj;
 795   }
 796 
 797   bool failures() { return _failures; }
 798   int n_failures() { return _n_failures; }
 799 
 800   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
 801   virtual void do_oop(      oop* p) { do_oop_work(p); }
 802 
 803   void print_object(outputStream* out, oop obj) {
 804 #ifdef PRODUCT
 805     Klass* k = obj->klass();
 806     const char* class_name = InstanceKlass::cast(k)->external_name();
 807     out->print_cr("class name %s", class_name);
 808 #else // PRODUCT
 809     obj->print_on(out);
 810 #endif // PRODUCT
 811   }
 812 
 813   template <class T>
 814   void do_oop_work(T* p) {
 815     assert(_containing_obj != NULL, "Precondition");
 816     assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
 817            "Precondition");
 818     T heap_oop = oopDesc::load_heap_oop(p);
 819     if (!oopDesc::is_null(heap_oop)) {
 820       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 821       bool failed = false;
 822       if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
 823         MutexLockerEx x(ParGCRareEvent_lock,
 824                         Mutex::_no_safepoint_check_flag);
 825 
 826         if (!_failures) {
 827           gclog_or_tty->print_cr("");
 828           gclog_or_tty->print_cr("----------");
 829         }
 830         if (!_g1h->is_in_closed_subset(obj)) {
 831           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 832           gclog_or_tty->print_cr("Field "PTR_FORMAT
 833                                  " of live obj "PTR_FORMAT" in region "
 834                                  "["PTR_FORMAT", "PTR_FORMAT")",
 835                                  p, (void*) _containing_obj,
 836                                  from->bottom(), from->end());
 837           print_object(gclog_or_tty, _containing_obj);
 838           gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
 839                                  (void*) obj);
 840         } else {
 841           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 842           HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
 843           gclog_or_tty->print_cr("Field "PTR_FORMAT
 844                                  " of live obj "PTR_FORMAT" in region "
 845                                  "["PTR_FORMAT", "PTR_FORMAT")",
 846                                  p, (void*) _containing_obj,
 847                                  from->bottom(), from->end());
 848           print_object(gclog_or_tty, _containing_obj);
 849           gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
 850                                  "["PTR_FORMAT", "PTR_FORMAT")",
 851                                  (void*) obj, to->bottom(), to->end());
 852           print_object(gclog_or_tty, obj);
 853         }
 854         gclog_or_tty->print_cr("----------");
 855         gclog_or_tty->flush();
 856         _failures = true;
 857         failed = true;
 858         _n_failures++;
 859       }
 860 
 861       if (!_g1h->full_collection() || G1VerifyRSetsDuringFullGC) {
 862         HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 863         HeapRegion* to   = _g1h->heap_region_containing(obj);
 864         if (from != NULL && to != NULL &&
 865             from != to &&
 866             !to->isHumongous()) {
 867           jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
 868           jbyte cv_field = *_bs->byte_for_const(p);
 869           const jbyte dirty = CardTableModRefBS::dirty_card_val();
 870 
 871           bool is_bad = !(from->is_young()
 872                           || to->rem_set()->contains_reference(p)
 873                           || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
 874                               (_containing_obj->is_objArray() ?
 875                                   cv_field == dirty
 876                                : cv_obj == dirty || cv_field == dirty));
 877           if (is_bad) {
 878             MutexLockerEx x(ParGCRareEvent_lock,
 879                             Mutex::_no_safepoint_check_flag);
 880 
 881             if (!_failures) {
 882               gclog_or_tty->print_cr("");
 883               gclog_or_tty->print_cr("----------");
 884             }
 885             gclog_or_tty->print_cr("Missing rem set entry:");
 886             gclog_or_tty->print_cr("Field "PTR_FORMAT" "
 887                                    "of obj "PTR_FORMAT", "
 888                                    "in region "HR_FORMAT,
 889                                    p, (void*) _containing_obj,
 890                                    HR_FORMAT_PARAMS(from));
 891             _containing_obj->print_on(gclog_or_tty);
 892             gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
 893                                    "in region "HR_FORMAT,
 894                                    (void*) obj,
 895                                    HR_FORMAT_PARAMS(to));
 896             obj->print_on(gclog_or_tty);
 897             gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
 898                           cv_obj, cv_field);
 899             gclog_or_tty->print_cr("----------");
 900             gclog_or_tty->flush();
 901             _failures = true;
 902             if (!failed) _n_failures++;
 903           }
 904         }
 905       }
 906     }
 907   }
 908 };
 909 
 910 // This really ought to be commoned up into OffsetTableContigSpace somehow.
 911 // We would need a mechanism to make that code skip dead objects.
 912 
 913 void HeapRegion::verify(VerifyOption vo,
 914                         bool* failures) const {
 915   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 916   *failures = false;
 917   HeapWord* p = bottom();
 918   HeapWord* prev_p = NULL;
 919   VerifyLiveClosure vl_cl(g1, vo);
 920   bool is_humongous = isHumongous();
 921   bool do_bot_verify = !is_young();
 922   size_t object_num = 0;
 923   while (p < top()) {
 924     oop obj = oop(p);
 925     size_t obj_size = obj->size();
 926     object_num += 1;
 927 
 928     if (is_humongous != g1->isHumongous(obj_size)) {
 929       gclog_or_tty->print_cr("obj "PTR_FORMAT" is of %shumongous size ("
 930                              SIZE_FORMAT" words) in a %shumongous region",
 931                              p, g1->isHumongous(obj_size) ? "" : "non-",
 932                              obj_size, is_humongous ? "" : "non-");
 933        *failures = true;
 934        return;
 935     }
 936 
 937     // If it returns false, verify_for_object() will output the
 938     // appropriate messasge.
 939     if (do_bot_verify && !_offsets.verify_for_object(p, obj_size)) {
 940       *failures = true;
 941       return;
 942     }
 943 
 944     if (!g1->is_obj_dead_cond(obj, this, vo)) {
 945       if (obj->is_oop()) {
 946         Klass* klass = obj->klass();
 947         if (!klass->is_metaspace_object()) {
 948           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 949                                  "not metadata", klass, (void *)obj);
 950           *failures = true;
 951           return;
 952         } else if (!klass->is_klass()) {
 953           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 954                                  "not a klass", klass, (void *)obj);
 955           *failures = true;
 956           return;
 957         } else {
 958           vl_cl.set_containing_obj(obj);
 959           obj->oop_iterate_no_header(&vl_cl);
 960           if (vl_cl.failures()) {
 961             *failures = true;
 962           }
 963           if (G1MaxVerifyFailures >= 0 &&
 964               vl_cl.n_failures() >= G1MaxVerifyFailures) {
 965             return;
 966           }
 967         }
 968       } else {
 969         gclog_or_tty->print_cr(PTR_FORMAT" no an oop", (void *)obj);
 970         *failures = true;
 971         return;
 972       }
 973     }
 974     prev_p = p;
 975     p += obj_size;
 976   }
 977 
 978   if (p != top()) {
 979     gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
 980                            "does not match top "PTR_FORMAT, p, top());
 981     *failures = true;
 982     return;
 983   }
 984 
 985   HeapWord* the_end = end();
 986   assert(p == top(), "it should still hold");
 987   // Do some extra BOT consistency checking for addresses in the
 988   // range [top, end). BOT look-ups in this range should yield
 989   // top. No point in doing that if top == end (there's nothing there).
 990   if (p < the_end) {
 991     // Look up top
 992     HeapWord* addr_1 = p;
 993     HeapWord* b_start_1 = _offsets.block_start_const(addr_1);
 994     if (b_start_1 != p) {
 995       gclog_or_tty->print_cr("BOT look up for top: "PTR_FORMAT" "
 996                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 997                              addr_1, b_start_1, p);
 998       *failures = true;
 999       return;
1000     }
1001 
1002     // Look up top + 1
1003     HeapWord* addr_2 = p + 1;
1004     if (addr_2 < the_end) {
1005       HeapWord* b_start_2 = _offsets.block_start_const(addr_2);
1006       if (b_start_2 != p) {
1007         gclog_or_tty->print_cr("BOT look up for top + 1: "PTR_FORMAT" "
1008                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
1009                                addr_2, b_start_2, p);
1010         *failures = true;
1011         return;
1012       }
1013     }
1014 
1015     // Look up an address between top and end
1016     size_t diff = pointer_delta(the_end, p) / 2;
1017     HeapWord* addr_3 = p + diff;
1018     if (addr_3 < the_end) {
1019       HeapWord* b_start_3 = _offsets.block_start_const(addr_3);
1020       if (b_start_3 != p) {
1021         gclog_or_tty->print_cr("BOT look up for top + diff: "PTR_FORMAT" "
1022                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
1023                                addr_3, b_start_3, p);
1024         *failures = true;
1025         return;
1026       }
1027     }
1028 
1029     // Loook up end - 1
1030     HeapWord* addr_4 = the_end - 1;
1031     HeapWord* b_start_4 = _offsets.block_start_const(addr_4);
1032     if (b_start_4 != p) {
1033       gclog_or_tty->print_cr("BOT look up for end - 1: "PTR_FORMAT" "
1034                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
1035                              addr_4, b_start_4, p);
1036       *failures = true;
1037       return;
1038     }
1039   }
1040 
1041   if (is_humongous && object_num > 1) {
1042     gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
1043                            "but has "SIZE_FORMAT", objects",
1044                            bottom(), end(), object_num);
1045     *failures = true;
1046     return;
1047   }
1048 
1049   verify_strong_code_roots(vo, failures);
1050 }
1051 
1052 void HeapRegion::verify() const {
1053   bool dummy = false;
1054   verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
1055 }
1056 
1057 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
1058 // away eventually.
1059 
1060 void G1OffsetTableContigSpace::clear(bool mangle_space) {
1061   ContiguousSpace::clear(mangle_space);
1062   _offsets.zero_bottom_entry();
1063   _offsets.initialize_threshold();
1064 }
1065 
1066 void G1OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
1067   Space::set_bottom(new_bottom);
1068   _offsets.set_bottom(new_bottom);
1069 }
1070 
1071 void G1OffsetTableContigSpace::set_end(HeapWord* new_end) {
1072   Space::set_end(new_end);
1073   _offsets.resize(new_end - bottom());
1074 }
1075 
1076 void G1OffsetTableContigSpace::print() const {
1077   print_short();
1078   gclog_or_tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
1079                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
1080                 bottom(), top(), _offsets.threshold(), end());
1081 }
1082 
1083 HeapWord* G1OffsetTableContigSpace::initialize_threshold() {
1084   return _offsets.initialize_threshold();
1085 }
1086 
1087 HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
1088                                                     HeapWord* end) {
1089   _offsets.alloc_block(start, end);
1090   return _offsets.threshold();
1091 }
1092 
1093 HeapWord* G1OffsetTableContigSpace::saved_mark_word() const {
1094   G1CollectedHeap* g1h = G1CollectedHeap::heap();
1095   assert( _gc_time_stamp <= g1h->get_gc_time_stamp(), "invariant" );
1096   if (_gc_time_stamp < g1h->get_gc_time_stamp())
1097     return top();
1098   else
1099     return ContiguousSpace::saved_mark_word();
1100 }
1101 
1102 void G1OffsetTableContigSpace::set_saved_mark() {
1103   G1CollectedHeap* g1h = G1CollectedHeap::heap();
1104   unsigned curr_gc_time_stamp = g1h->get_gc_time_stamp();
1105 
1106   if (_gc_time_stamp < curr_gc_time_stamp) {
1107     // The order of these is important, as another thread might be
1108     // about to start scanning this region. If it does so after
1109     // set_saved_mark and before _gc_time_stamp = ..., then the latter
1110     // will be false, and it will pick up top() as the high water mark
1111     // of region. If it does so after _gc_time_stamp = ..., then it
1112     // will pick up the right saved_mark_word() as the high water mark
1113     // of the region. Either way, the behaviour will be correct.
1114     ContiguousSpace::set_saved_mark();
1115     OrderAccess::storestore();
1116     _gc_time_stamp = curr_gc_time_stamp;
1117     // No need to do another barrier to flush the writes above. If
1118     // this is called in parallel with other threads trying to
1119     // allocate into the region, the caller should call this while
1120     // holding a lock and when the lock is released the writes will be
1121     // flushed.
1122   }
1123 }
1124 
1125 G1OffsetTableContigSpace::
1126 G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
1127                          MemRegion mr) :
1128   _offsets(sharedOffsetArray, mr),
1129   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
1130   _gc_time_stamp(0)
1131 {
1132   _offsets.set_space(this);
1133   // false ==> we'll do the clearing if there's clearing to be done.
1134   ContiguousSpace::initialize(mr, false, SpaceDecorator::Mangle);
1135   _offsets.zero_bottom_entry();
1136   _offsets.initialize_threshold();
1137 }