1 /*
   2  * Copyright (c) 2001, 2012, 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_implementation/g1/g1BlockOffsetTable.inline.hpp"
  27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  29 #include "gc_implementation/g1/heapRegion.inline.hpp"
  30 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  31 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  32 #include "memory/genOopClosures.inline.hpp"
  33 #include "memory/iterator.hpp"
  34 #include "oops/oop.inline.hpp"
  35 
  36 int    HeapRegion::LogOfHRGrainBytes = 0;
  37 int    HeapRegion::LogOfHRGrainWords = 0;
  38 size_t HeapRegion::GrainBytes        = 0;
  39 size_t HeapRegion::GrainWords        = 0;
  40 size_t HeapRegion::CardsPerRegion    = 0;
  41 
  42 HeapRegionDCTOC::HeapRegionDCTOC(G1CollectedHeap* g1,
  43                                  HeapRegion* hr, ExtendedOopClosure* cl,
  44                                  CardTableModRefBS::PrecisionStyle precision,
  45                                  FilterKind fk) :
  46   ContiguousSpaceDCTOC(hr, cl, precision, NULL),
  47   _hr(hr), _fk(fk), _g1(g1) { }
  48 
  49 FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
  50                                                    OopClosure* oc) :
  51   _r_bottom(r->bottom()), _r_end(r->end()), _oc(oc) { }
  52 
  53 class VerifyLiveClosure: public OopClosure {
  54 private:
  55   G1CollectedHeap* _g1h;
  56   CardTableModRefBS* _bs;
  57   oop _containing_obj;
  58   bool _failures;
  59   int _n_failures;
  60   VerifyOption _vo;
  61 public:
  62   // _vo == UsePrevMarking -> use "prev" marking information,
  63   // _vo == UseNextMarking -> use "next" marking information,
  64   // _vo == UseMarkWord    -> use mark word from object header.
  65   VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
  66     _g1h(g1h), _bs(NULL), _containing_obj(NULL),
  67     _failures(false), _n_failures(0), _vo(vo)
  68   {
  69     BarrierSet* bs = _g1h->barrier_set();
  70     if (bs->is_a(BarrierSet::CardTableModRef))
  71       _bs = (CardTableModRefBS*)bs;
  72   }
  73 
  74   void set_containing_obj(oop obj) {
  75     _containing_obj = obj;
  76   }
  77 
  78   bool failures() { return _failures; }
  79   int n_failures() { return _n_failures; }
  80 
  81   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  82   virtual void do_oop(      oop* p) { do_oop_work(p); }
  83 
  84   void print_object(outputStream* out, oop obj) {
  85 #ifdef PRODUCT
  86     Klass* k = obj->klass();
  87     const char* class_name = InstanceKlass::cast(k)->external_name();
  88     out->print_cr("class name %s", class_name);
  89 #else // PRODUCT
  90     obj->print_on(out);
  91 #endif // PRODUCT
  92   }
  93 
  94   template <class T>
  95   void do_oop_work(T* p) {
  96     assert(_containing_obj != NULL, "Precondition");
  97     assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
  98            "Precondition");
  99     T heap_oop = oopDesc::load_heap_oop(p);
 100     if (!oopDesc::is_null(heap_oop)) {
 101       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 102       bool failed = false;
 103       if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
 104         MutexLockerEx x(ParGCRareEvent_lock,
 105                         Mutex::_no_safepoint_check_flag);
 106 
 107         if (!_failures) {
 108           gclog_or_tty->print_cr("");
 109           gclog_or_tty->print_cr("----------");
 110         }
 111         if (!_g1h->is_in_closed_subset(obj)) {
 112           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 113           gclog_or_tty->print_cr("Field "PTR_FORMAT
 114                                  " of live obj "PTR_FORMAT" in region "
 115                                  "["PTR_FORMAT", "PTR_FORMAT")",
 116                                  p, (void*) _containing_obj,
 117                                  from->bottom(), from->end());
 118           print_object(gclog_or_tty, _containing_obj);
 119           gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
 120                                  (void*) obj);
 121         } else {
 122           HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 123           HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
 124           gclog_or_tty->print_cr("Field "PTR_FORMAT
 125                                  " of live obj "PTR_FORMAT" in region "
 126                                  "["PTR_FORMAT", "PTR_FORMAT")",
 127                                  p, (void*) _containing_obj,
 128                                  from->bottom(), from->end());
 129           print_object(gclog_or_tty, _containing_obj);
 130           gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
 131                                  "["PTR_FORMAT", "PTR_FORMAT")",
 132                                  (void*) obj, to->bottom(), to->end());
 133           print_object(gclog_or_tty, obj);
 134         }
 135         gclog_or_tty->print_cr("----------");
 136         gclog_or_tty->flush();
 137         _failures = true;
 138         failed = true;
 139         _n_failures++;
 140       }
 141 
 142       if (!_g1h->full_collection()) {
 143         HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
 144         HeapRegion* to   = _g1h->heap_region_containing(obj);
 145         if (from != NULL && to != NULL &&
 146             from != to &&
 147             !to->isHumongous()) {
 148           jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
 149           jbyte cv_field = *_bs->byte_for_const(p);
 150           const jbyte dirty = CardTableModRefBS::dirty_card_val();
 151 
 152           bool is_bad = !(from->is_young()
 153                           || to->rem_set()->contains_reference(p)
 154                           || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
 155                               (_containing_obj->is_objArray() ?
 156                                   cv_field == dirty
 157                                : cv_obj == dirty || cv_field == dirty));
 158           if (is_bad) {
 159             MutexLockerEx x(ParGCRareEvent_lock,
 160                             Mutex::_no_safepoint_check_flag);
 161 
 162             if (!_failures) {
 163               gclog_or_tty->print_cr("");
 164               gclog_or_tty->print_cr("----------");
 165             }
 166             gclog_or_tty->print_cr("Missing rem set entry:");
 167             gclog_or_tty->print_cr("Field "PTR_FORMAT" "
 168                                    "of obj "PTR_FORMAT", "
 169                                    "in region "HR_FORMAT,
 170                                    p, (void*) _containing_obj,
 171                                    HR_FORMAT_PARAMS(from));
 172             _containing_obj->print_on(gclog_or_tty);
 173             gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
 174                                    "in region "HR_FORMAT,
 175                                    (void*) obj,
 176                                    HR_FORMAT_PARAMS(to));
 177             obj->print_on(gclog_or_tty);
 178             gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
 179                           cv_obj, cv_field);
 180             gclog_or_tty->print_cr("----------");
 181             gclog_or_tty->flush();
 182             _failures = true;
 183             if (!failed) _n_failures++;
 184           }
 185         }
 186       }
 187     }
 188   }
 189 };
 190 
 191 template<class ClosureType>
 192 HeapWord* walk_mem_region_loop(ClosureType* cl, G1CollectedHeap* g1h,
 193                                HeapRegion* hr,
 194                                HeapWord* cur, HeapWord* top) {
 195   oop cur_oop = oop(cur);
 196   int oop_size = cur_oop->size();
 197   HeapWord* next_obj = cur + oop_size;
 198   while (next_obj < top) {
 199     // Keep filtering the remembered set.
 200     if (!g1h->is_obj_dead(cur_oop, hr)) {
 201       // Bottom lies entirely below top, so we can call the
 202       // non-memRegion version of oop_iterate below.
 203       cur_oop->oop_iterate(cl);
 204     }
 205     cur = next_obj;
 206     cur_oop = oop(cur);
 207     oop_size = cur_oop->size();
 208     next_obj = cur + oop_size;
 209   }
 210   return cur;
 211 }
 212 
 213 void HeapRegionDCTOC::walk_mem_region_with_cl(MemRegion mr,
 214                                               HeapWord* bottom,
 215                                               HeapWord* top,
 216                                               ExtendedOopClosure* cl) {
 217   G1CollectedHeap* g1h = _g1;
 218   int oop_size;
 219   ExtendedOopClosure* cl2 = NULL;
 220 
 221   FilterIntoCSClosure intoCSFilt(this, g1h, cl);
 222   FilterOutOfRegionClosure outOfRegionFilt(_hr, cl);
 223 
 224   switch (_fk) {
 225   case NoFilterKind:          cl2 = cl; break;
 226   case IntoCSFilterKind:      cl2 = &intoCSFilt; break;
 227   case OutOfRegionFilterKind: cl2 = &outOfRegionFilt; break;
 228   default:                    ShouldNotReachHere();
 229   }
 230 
 231   // Start filtering what we add to the remembered set. If the object is
 232   // not considered dead, either because it is marked (in the mark bitmap)
 233   // or it was allocated after marking finished, then we add it. Otherwise
 234   // we can safely ignore the object.
 235   if (!g1h->is_obj_dead(oop(bottom), _hr)) {
 236     oop_size = oop(bottom)->oop_iterate(cl2, mr);
 237   } else {
 238     oop_size = oop(bottom)->size();
 239   }
 240 
 241   bottom += oop_size;
 242 
 243   if (bottom < top) {
 244     // We replicate the loop below for several kinds of possible filters.
 245     switch (_fk) {
 246     case NoFilterKind:
 247       bottom = walk_mem_region_loop(cl, g1h, _hr, bottom, top);
 248       break;
 249 
 250     case IntoCSFilterKind: {
 251       FilterIntoCSClosure filt(this, g1h, cl);
 252       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
 253       break;
 254     }
 255 
 256     case OutOfRegionFilterKind: {
 257       FilterOutOfRegionClosure filt(_hr, cl);
 258       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
 259       break;
 260     }
 261 
 262     default:
 263       ShouldNotReachHere();
 264     }
 265 
 266     // Last object. Need to do dead-obj filtering here too.
 267     if (!g1h->is_obj_dead(oop(bottom), _hr)) {
 268       oop(bottom)->oop_iterate(cl2, mr);
 269     }
 270   }
 271 }
 272 
 273 // Minimum region size; we won't go lower than that.
 274 // We might want to decrease this in the future, to deal with small
 275 // heaps a bit more efficiently.
 276 #define MIN_REGION_SIZE  (      1024 * 1024 )
 277 
 278 // Maximum region size; we don't go higher than that. There's a good
 279 // reason for having an upper bound. We don't want regions to get too
 280 // large, otherwise cleanup's effectiveness would decrease as there
 281 // will be fewer opportunities to find totally empty regions after
 282 // marking.
 283 #define MAX_REGION_SIZE  ( 32 * 1024 * 1024 )
 284 
 285 // The automatic region size calculation will try to have around this
 286 // many regions in the heap (based on the min heap size).
 287 #define TARGET_REGION_NUMBER          2048
 288 
 289 void HeapRegion::setup_heap_region_size(uintx min_heap_size) {
 290   // region_size in bytes
 291   uintx region_size = G1HeapRegionSize;
 292   if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
 293     // We base the automatic calculation on the min heap size. This
 294     // can be problematic if the spread between min and max is quite
 295     // wide, imagine -Xms128m -Xmx32g. But, if we decided it based on
 296     // the max size, the region size might be way too large for the
 297     // min size. Either way, some users might have to set the region
 298     // size manually for some -Xms / -Xmx combos.
 299 
 300     region_size = MAX2(min_heap_size / TARGET_REGION_NUMBER,
 301                        (uintx) MIN_REGION_SIZE);
 302   }
 303 
 304   int region_size_log = log2_long((jlong) region_size);
 305   // Recalculate the region size to make sure it's a power of
 306   // 2. This means that region_size is the largest power of 2 that's
 307   // <= what we've calculated so far.
 308   region_size = ((uintx)1 << region_size_log);
 309 
 310   // Now make sure that we don't go over or under our limits.
 311   if (region_size < MIN_REGION_SIZE) {
 312     region_size = MIN_REGION_SIZE;
 313   } else if (region_size > MAX_REGION_SIZE) {
 314     region_size = MAX_REGION_SIZE;
 315   }
 316 
 317   // And recalculate the log.
 318   region_size_log = log2_long((jlong) region_size);
 319 
 320   // Now, set up the globals.
 321   guarantee(LogOfHRGrainBytes == 0, "we should only set it once");
 322   LogOfHRGrainBytes = region_size_log;
 323 
 324   guarantee(LogOfHRGrainWords == 0, "we should only set it once");
 325   LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize;
 326 
 327   guarantee(GrainBytes == 0, "we should only set it once");
 328   // The cast to int is safe, given that we've bounded region_size by
 329   // MIN_REGION_SIZE and MAX_REGION_SIZE.
 330   GrainBytes = (size_t)region_size;
 331 
 332   guarantee(GrainWords == 0, "we should only set it once");
 333   GrainWords = GrainBytes >> LogHeapWordSize;
 334   guarantee((size_t) 1 << LogOfHRGrainWords == GrainWords, "sanity");
 335 
 336   guarantee(CardsPerRegion == 0, "we should only set it once");
 337   CardsPerRegion = GrainBytes >> CardTableModRefBS::card_shift;
 338 }
 339 
 340 void HeapRegion::reset_after_compaction() {
 341   G1OffsetTableContigSpace::reset_after_compaction();
 342   // After a compaction the mark bitmap is invalid, so we must
 343   // treat all objects as being inside the unmarked area.
 344   zero_marked_bytes();
 345   init_top_at_mark_start();
 346 }
 347 
 348 void HeapRegion::hr_clear(bool par, bool clear_space) {
 349   assert(_humongous_type == NotHumongous,
 350          "we should have already filtered out humongous regions");
 351   assert(_humongous_start_region == NULL,
 352          "we should have already filtered out humongous regions");
 353   assert(_end == _orig_end,
 354          "we should have already filtered out humongous regions");
 355 
 356   _in_collection_set = false;
 357 
 358   set_young_index_in_cset(-1);
 359   uninstall_surv_rate_group();
 360   set_young_type(NotYoung);
 361   reset_pre_dummy_top();
 362 
 363   if (!par) {
 364     // If this is parallel, this will be done later.
 365     HeapRegionRemSet* hrrs = rem_set();
 366     if (hrrs != NULL) hrrs->clear();
 367     _claimed = InitialClaimValue;
 368   }
 369   zero_marked_bytes();
 370 
 371   _offsets.resize(HeapRegion::GrainWords);
 372   init_top_at_mark_start();
 373   if (clear_space) clear(SpaceDecorator::Mangle);
 374 }
 375 
 376 void HeapRegion::par_clear() {
 377   assert(used() == 0, "the region should have been already cleared");
 378   assert(capacity() == HeapRegion::GrainBytes, "should be back to normal");
 379   HeapRegionRemSet* hrrs = rem_set();
 380   hrrs->clear();
 381   CardTableModRefBS* ct_bs =
 382                    (CardTableModRefBS*)G1CollectedHeap::heap()->barrier_set();
 383   ct_bs->clear(MemRegion(bottom(), end()));
 384 }
 385 
 386 void HeapRegion::calc_gc_efficiency() {
 387   // GC efficiency is the ratio of how much space would be
 388   // reclaimed over how long we predict it would take to reclaim it.
 389   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 390   G1CollectorPolicy* g1p = g1h->g1_policy();
 391 
 392   // Retrieve a prediction of the elapsed time for this region for
 393   // a mixed gc because the region will only be evacuated during a
 394   // mixed gc.
 395   double region_elapsed_time_ms =
 396     g1p->predict_region_elapsed_time_ms(this, false /* for_young_gc */);
 397   _gc_efficiency = (double) reclaimable_bytes() / region_elapsed_time_ms;
 398 }
 399 
 400 void HeapRegion::set_startsHumongous(HeapWord* new_top, HeapWord* new_end) {
 401   assert(!isHumongous(), "sanity / pre-condition");
 402   assert(end() == _orig_end,
 403          "Should be normal before the humongous object allocation");
 404   assert(top() == bottom(), "should be empty");
 405   assert(bottom() <= new_top && new_top <= new_end, "pre-condition");
 406 
 407   _humongous_type = StartsHumongous;
 408   _humongous_start_region = this;
 409 
 410   set_end(new_end);
 411   _offsets.set_for_starts_humongous(new_top);
 412 }
 413 
 414 void HeapRegion::set_continuesHumongous(HeapRegion* first_hr) {
 415   assert(!isHumongous(), "sanity / pre-condition");
 416   assert(end() == _orig_end,
 417          "Should be normal before the humongous object allocation");
 418   assert(top() == bottom(), "should be empty");
 419   assert(first_hr->startsHumongous(), "pre-condition");
 420 
 421   _humongous_type = ContinuesHumongous;
 422   _humongous_start_region = first_hr;
 423 }
 424 
 425 void HeapRegion::set_notHumongous() {
 426   assert(isHumongous(), "pre-condition");
 427 
 428   if (startsHumongous()) {
 429     assert(top() <= end(), "pre-condition");
 430     set_end(_orig_end);
 431     if (top() > end()) {
 432       // at least one "continues humongous" region after it
 433       set_top(end());
 434     }
 435   } else {
 436     // continues humongous
 437     assert(end() == _orig_end, "sanity");
 438   }
 439 
 440   assert(capacity() == HeapRegion::GrainBytes, "pre-condition");
 441   _humongous_type = NotHumongous;
 442   _humongous_start_region = NULL;
 443 }
 444 
 445 bool HeapRegion::claimHeapRegion(jint claimValue) {
 446   jint current = _claimed;
 447   if (current != claimValue) {
 448     jint res = Atomic::cmpxchg(claimValue, &_claimed, current);
 449     if (res == current) {
 450       return true;
 451     }
 452   }
 453   return false;
 454 }
 455 
 456 HeapWord* HeapRegion::next_block_start_careful(HeapWord* addr) {
 457   HeapWord* low = addr;
 458   HeapWord* high = end();
 459   while (low < high) {
 460     size_t diff = pointer_delta(high, low);
 461     // Must add one below to bias toward the high amount.  Otherwise, if
 462   // "high" were at the desired value, and "low" were one less, we
 463     // would not converge on "high".  This is not symmetric, because
 464     // we set "high" to a block start, which might be the right one,
 465     // which we don't do for "low".
 466     HeapWord* middle = low + (diff+1)/2;
 467     if (middle == high) return high;
 468     HeapWord* mid_bs = block_start_careful(middle);
 469     if (mid_bs < addr) {
 470       low = middle;
 471     } else {
 472       high = mid_bs;
 473     }
 474   }
 475   assert(low == high && low >= addr, "Didn't work.");
 476   return low;
 477 }
 478 
 479 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 480 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 481 #endif // _MSC_VER
 482 
 483 
 484 HeapRegion::HeapRegion(uint hrs_index,
 485                        G1BlockOffsetSharedArray* sharedOffsetArray,
 486                        MemRegion mr) :
 487     G1OffsetTableContigSpace(sharedOffsetArray, mr),
 488     _hrs_index(hrs_index),
 489     _humongous_type(NotHumongous), _humongous_start_region(NULL),
 490     _in_collection_set(false),
 491     _next_in_special_set(NULL), _orig_end(NULL),
 492     _claimed(InitialClaimValue), _evacuation_failed(false),
 493     _prev_marked_bytes(0), _next_marked_bytes(0), _gc_efficiency(0.0),
 494     _young_type(NotYoung), _next_young_region(NULL),
 495     _next_dirty_cards_region(NULL), _next(NULL), _pending_removal(false),
 496 #ifdef ASSERT
 497     _containing_set(NULL),
 498 #endif // ASSERT
 499      _young_index_in_cset(-1), _surv_rate_group(NULL), _age_index(-1),
 500     _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0),
 501     _predicted_bytes_to_copy(0)
 502 {
 503   _orig_end = mr.end();
 504   // Note that initialize() will set the start of the unmarked area of the
 505   // region.
 506   hr_clear(false /*par*/, false /*clear_space*/);
 507   set_top(bottom());
 508   set_saved_mark();
 509 
 510   _rem_set =  new HeapRegionRemSet(sharedOffsetArray, this);
 511 
 512   assert(HeapRegionRemSet::num_par_rem_sets() > 0, "Invariant.");
 513 }
 514 
 515 CompactibleSpace* HeapRegion::next_compaction_space() const {
 516   // We're not using an iterator given that it will wrap around when
 517   // it reaches the last region and this is not what we want here.
 518   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 519   uint index = hrs_index() + 1;
 520   while (index < g1h->n_regions()) {
 521     HeapRegion* hr = g1h->region_at(index);
 522     if (!hr->isHumongous()) {
 523       return hr;
 524     }
 525     index += 1;
 526   }
 527   return NULL;
 528 }
 529 
 530 void HeapRegion::save_marks() {
 531   set_saved_mark();
 532 }
 533 
 534 void HeapRegion::oops_in_mr_iterate(MemRegion mr, ExtendedOopClosure* cl) {
 535   HeapWord* p = mr.start();
 536   HeapWord* e = mr.end();
 537   oop obj;
 538   while (p < e) {
 539     obj = oop(p);
 540     p += obj->oop_iterate(cl);
 541   }
 542   assert(p == e, "bad memregion: doesn't end on obj boundary");
 543 }
 544 
 545 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
 546 void HeapRegion::oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
 547   ContiguousSpace::oop_since_save_marks_iterate##nv_suffix(cl);              \
 548 }
 549 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DEFN)
 550 
 551 
 552 void HeapRegion::oop_before_save_marks_iterate(ExtendedOopClosure* cl) {
 553   oops_in_mr_iterate(MemRegion(bottom(), saved_mark_word()), cl);
 554 }
 555 
 556 void HeapRegion::note_self_forwarding_removal_start(bool during_initial_mark,
 557                                                     bool during_conc_mark) {
 558   // We always recreate the prev marking info and we'll explicitly
 559   // mark all objects we find to be self-forwarded on the prev
 560   // bitmap. So all objects need to be below PTAMS.
 561   _prev_top_at_mark_start = top();
 562   _prev_marked_bytes = 0;
 563 
 564   if (during_initial_mark) {
 565     // During initial-mark, we'll also explicitly mark all objects
 566     // we find to be self-forwarded on the next bitmap. So all
 567     // objects need to be below NTAMS.
 568     _next_top_at_mark_start = top();
 569     _next_marked_bytes = 0;
 570   } else if (during_conc_mark) {
 571     // During concurrent mark, all objects in the CSet (including
 572     // the ones we find to be self-forwarded) are implicitly live.
 573     // So all objects need to be above NTAMS.
 574     _next_top_at_mark_start = bottom();
 575     _next_marked_bytes = 0;
 576   }
 577 }
 578 
 579 void HeapRegion::note_self_forwarding_removal_end(bool during_initial_mark,
 580                                                   bool during_conc_mark,
 581                                                   size_t marked_bytes) {
 582   assert(0 <= marked_bytes && marked_bytes <= used(),
 583          err_msg("marked: "SIZE_FORMAT" used: "SIZE_FORMAT,
 584                  marked_bytes, used()));
 585   _prev_marked_bytes = marked_bytes;
 586 }
 587 
 588 HeapWord*
 589 HeapRegion::object_iterate_mem_careful(MemRegion mr,
 590                                                  ObjectClosure* cl) {
 591   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 592   // We used to use "block_start_careful" here.  But we're actually happy
 593   // to update the BOT while we do this...
 594   HeapWord* cur = block_start(mr.start());
 595   mr = mr.intersection(used_region());
 596   if (mr.is_empty()) return NULL;
 597   // Otherwise, find the obj that extends onto mr.start().
 598 
 599   assert(cur <= mr.start()
 600          && (oop(cur)->klass_or_null() == NULL ||
 601              cur + oop(cur)->size() > mr.start()),
 602          "postcondition of block_start");
 603   oop obj;
 604   while (cur < mr.end()) {
 605     obj = oop(cur);
 606     if (obj->klass_or_null() == NULL) {
 607       // Ran into an unparseable point.
 608       return cur;
 609     } else if (!g1h->is_obj_dead(obj)) {
 610       cl->do_object(obj);
 611     }
 612     if (cl->abort()) return cur;
 613     // The check above must occur before the operation below, since an
 614     // abort might invalidate the "size" operation.
 615     cur += obj->size();
 616   }
 617   return NULL;
 618 }
 619 
 620 HeapWord*
 621 HeapRegion::
 622 oops_on_card_seq_iterate_careful(MemRegion mr,
 623                                  FilterOutOfRegionClosure* cl,
 624                                  bool filter_young,
 625                                  jbyte* card_ptr) {
 626   // Currently, we should only have to clean the card if filter_young
 627   // is true and vice versa.
 628   if (filter_young) {
 629     assert(card_ptr != NULL, "pre-condition");
 630   } else {
 631     assert(card_ptr == NULL, "pre-condition");
 632   }
 633   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 634 
 635   // If we're within a stop-world GC, then we might look at a card in a
 636   // GC alloc region that extends onto a GC LAB, which may not be
 637   // parseable.  Stop such at the "saved_mark" of the region.
 638   if (g1h->is_gc_active()) {
 639     mr = mr.intersection(used_region_at_save_marks());
 640   } else {
 641     mr = mr.intersection(used_region());
 642   }
 643   if (mr.is_empty()) return NULL;
 644   // Otherwise, find the obj that extends onto mr.start().
 645 
 646   // The intersection of the incoming mr (for the card) and the
 647   // allocated part of the region is non-empty. This implies that
 648   // we have actually allocated into this region. The code in
 649   // G1CollectedHeap.cpp that allocates a new region sets the
 650   // is_young tag on the region before allocating. Thus we
 651   // safely know if this region is young.
 652   if (is_young() && filter_young) {
 653     return NULL;
 654   }
 655 
 656   assert(!is_young(), "check value of filter_young");
 657 
 658   // We can only clean the card here, after we make the decision that
 659   // the card is not young. And we only clean the card if we have been
 660   // asked to (i.e., card_ptr != NULL).
 661   if (card_ptr != NULL) {
 662     *card_ptr = CardTableModRefBS::clean_card_val();
 663     // We must complete this write before we do any of the reads below.
 664     OrderAccess::storeload();
 665   }
 666 
 667   // Cache the boundaries of the memory region in some const locals
 668   HeapWord* const start = mr.start();
 669   HeapWord* const end = mr.end();
 670 
 671   // We used to use "block_start_careful" here.  But we're actually happy
 672   // to update the BOT while we do this...
 673   HeapWord* cur = block_start(start);
 674   assert(cur <= start, "Postcondition");
 675 
 676   oop obj;
 677 
 678   HeapWord* next = cur;
 679   while (next <= start) {
 680     cur = next;
 681     obj = oop(cur);
 682     if (obj->klass_or_null() == NULL) {
 683       // Ran into an unparseable point.
 684       return cur;
 685     }
 686     // Otherwise...
 687     next = (cur + obj->size());
 688   }
 689 
 690   // If we finish the above loop...We have a parseable object that
 691   // begins on or before the start of the memory region, and ends
 692   // inside or spans the entire region.
 693 
 694   assert(obj == oop(cur), "sanity");
 695   assert(cur <= start &&
 696          obj->klass_or_null() != NULL &&
 697          (cur + obj->size()) > start,
 698          "Loop postcondition");
 699 
 700   if (!g1h->is_obj_dead(obj)) {
 701     obj->oop_iterate(cl, mr);
 702   }
 703 
 704   while (cur < end) {
 705     obj = oop(cur);
 706     if (obj->klass_or_null() == NULL) {
 707       // Ran into an unparseable point.
 708       return cur;
 709     };
 710 
 711     // Otherwise:
 712     next = (cur + obj->size());
 713 
 714     if (!g1h->is_obj_dead(obj)) {
 715       if (next < end || !obj->is_objArray()) {
 716         // This object either does not span the MemRegion
 717         // boundary, or if it does it's not an array.
 718         // Apply closure to whole object.
 719         obj->oop_iterate(cl);
 720       } else {
 721         // This obj is an array that spans the boundary.
 722         // Stop at the boundary.
 723         obj->oop_iterate(cl, mr);
 724       }
 725     }
 726     cur = next;
 727   }
 728   return NULL;
 729 }
 730 
 731 void HeapRegion::print() const { print_on(gclog_or_tty); }
 732 void HeapRegion::print_on(outputStream* st) const {
 733   if (isHumongous()) {
 734     if (startsHumongous())
 735       st->print(" HS");
 736     else
 737       st->print(" HC");
 738   } else {
 739     st->print("   ");
 740   }
 741   if (in_collection_set())
 742     st->print(" CS");
 743   else
 744     st->print("   ");
 745   if (is_young())
 746     st->print(is_survivor() ? " SU" : " Y ");
 747   else
 748     st->print("   ");
 749   if (is_empty())
 750     st->print(" F");
 751   else
 752     st->print("  ");
 753   st->print(" TS %5d", _gc_time_stamp);
 754   st->print(" PTAMS "PTR_FORMAT" NTAMS "PTR_FORMAT,
 755             prev_top_at_mark_start(), next_top_at_mark_start());
 756   G1OffsetTableContigSpace::print_on(st);
 757 }
 758 
 759 void HeapRegion::verify() const {
 760   bool dummy = false;
 761   verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
 762 }
 763 
 764 // This really ought to be commoned up into OffsetTableContigSpace somehow.
 765 // We would need a mechanism to make that code skip dead objects.
 766 
 767 void HeapRegion::verify(VerifyOption vo,
 768                         bool* failures) const {
 769   G1CollectedHeap* g1 = G1CollectedHeap::heap();
 770   *failures = false;
 771   HeapWord* p = bottom();
 772   HeapWord* prev_p = NULL;
 773   VerifyLiveClosure vl_cl(g1, vo);
 774   bool is_humongous = isHumongous();
 775   bool do_bot_verify = !is_young();
 776   size_t object_num = 0;
 777   while (p < top()) {
 778     oop obj = oop(p);
 779     size_t obj_size = obj->size();
 780     object_num += 1;
 781 
 782     if (is_humongous != g1->isHumongous(obj_size)) {
 783       gclog_or_tty->print_cr("obj "PTR_FORMAT" is of %shumongous size ("
 784                              SIZE_FORMAT" words) in a %shumongous region",
 785                              p, g1->isHumongous(obj_size) ? "" : "non-",
 786                              obj_size, is_humongous ? "" : "non-");
 787        *failures = true;
 788        return;
 789     }
 790 
 791     // If it returns false, verify_for_object() will output the
 792     // appropriate messasge.
 793     if (do_bot_verify && !_offsets.verify_for_object(p, obj_size)) {
 794       *failures = true;
 795       return;
 796     }
 797 
 798     if (!g1->is_obj_dead_cond(obj, this, vo)) {
 799       if (obj->is_oop()) {
 800         Klass* klass = obj->klass();
 801         if (!klass->is_metadata()) {
 802           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 803                                  "not metadata", klass, obj);
 804           *failures = true;
 805           return;
 806         } else if (!klass->is_klass()) {
 807           gclog_or_tty->print_cr("klass "PTR_FORMAT" of object "PTR_FORMAT" "
 808                                  "not a klass", klass, obj);
 809           *failures = true;
 810           return;
 811         } else {
 812           vl_cl.set_containing_obj(obj);
 813           obj->oop_iterate_no_header(&vl_cl);
 814           if (vl_cl.failures()) {
 815             *failures = true;
 816           }
 817           if (G1MaxVerifyFailures >= 0 &&
 818               vl_cl.n_failures() >= G1MaxVerifyFailures) {
 819             return;
 820           }
 821         }
 822       } else {
 823         gclog_or_tty->print_cr(PTR_FORMAT" no an oop", obj);
 824         *failures = true;
 825         return;
 826       }
 827     }
 828     prev_p = p;
 829     p += obj_size;
 830   }
 831 
 832   if (p != top()) {
 833     gclog_or_tty->print_cr("end of last object "PTR_FORMAT" "
 834                            "does not match top "PTR_FORMAT, p, top());
 835     *failures = true;
 836     return;
 837   }
 838 
 839   HeapWord* the_end = end();
 840   assert(p == top(), "it should still hold");
 841   // Do some extra BOT consistency checking for addresses in the
 842   // range [top, end). BOT look-ups in this range should yield
 843   // top. No point in doing that if top == end (there's nothing there).
 844   if (p < the_end) {
 845     // Look up top
 846     HeapWord* addr_1 = p;
 847     HeapWord* b_start_1 = _offsets.block_start_const(addr_1);
 848     if (b_start_1 != p) {
 849       gclog_or_tty->print_cr("BOT look up for top: "PTR_FORMAT" "
 850                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 851                              addr_1, b_start_1, p);
 852       *failures = true;
 853       return;
 854     }
 855 
 856     // Look up top + 1
 857     HeapWord* addr_2 = p + 1;
 858     if (addr_2 < the_end) {
 859       HeapWord* b_start_2 = _offsets.block_start_const(addr_2);
 860       if (b_start_2 != p) {
 861         gclog_or_tty->print_cr("BOT look up for top + 1: "PTR_FORMAT" "
 862                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 863                                addr_2, b_start_2, p);
 864         *failures = true;
 865         return;
 866       }
 867     }
 868 
 869     // Look up an address between top and end
 870     size_t diff = pointer_delta(the_end, p) / 2;
 871     HeapWord* addr_3 = p + diff;
 872     if (addr_3 < the_end) {
 873       HeapWord* b_start_3 = _offsets.block_start_const(addr_3);
 874       if (b_start_3 != p) {
 875         gclog_or_tty->print_cr("BOT look up for top + diff: "PTR_FORMAT" "
 876                                " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 877                                addr_3, b_start_3, p);
 878         *failures = true;
 879         return;
 880       }
 881     }
 882 
 883     // Loook up end - 1
 884     HeapWord* addr_4 = the_end - 1;
 885     HeapWord* b_start_4 = _offsets.block_start_const(addr_4);
 886     if (b_start_4 != p) {
 887       gclog_or_tty->print_cr("BOT look up for end - 1: "PTR_FORMAT" "
 888                              " yielded "PTR_FORMAT", expecting "PTR_FORMAT,
 889                              addr_4, b_start_4, p);
 890       *failures = true;
 891       return;
 892     }
 893   }
 894 
 895   if (is_humongous && object_num > 1) {
 896     gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
 897                            "but has "SIZE_FORMAT", objects",
 898                            bottom(), end(), object_num);
 899     *failures = true;
 900     return;
 901   }
 902 }
 903 
 904 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
 905 // away eventually.
 906 
 907 void G1OffsetTableContigSpace::clear(bool mangle_space) {
 908   ContiguousSpace::clear(mangle_space);
 909   _offsets.zero_bottom_entry();
 910   _offsets.initialize_threshold();
 911 }
 912 
 913 void G1OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
 914   Space::set_bottom(new_bottom);
 915   _offsets.set_bottom(new_bottom);
 916 }
 917 
 918 void G1OffsetTableContigSpace::set_end(HeapWord* new_end) {
 919   Space::set_end(new_end);
 920   _offsets.resize(new_end - bottom());
 921 }
 922 
 923 void G1OffsetTableContigSpace::print() const {
 924   print_short();
 925   gclog_or_tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
 926                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
 927                 bottom(), top(), _offsets.threshold(), end());
 928 }
 929 
 930 HeapWord* G1OffsetTableContigSpace::initialize_threshold() {
 931   return _offsets.initialize_threshold();
 932 }
 933 
 934 HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
 935                                                     HeapWord* end) {
 936   _offsets.alloc_block(start, end);
 937   return _offsets.threshold();
 938 }
 939 
 940 HeapWord* G1OffsetTableContigSpace::saved_mark_word() const {
 941   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 942   assert( _gc_time_stamp <= g1h->get_gc_time_stamp(), "invariant" );
 943   if (_gc_time_stamp < g1h->get_gc_time_stamp())
 944     return top();
 945   else
 946     return ContiguousSpace::saved_mark_word();
 947 }
 948 
 949 void G1OffsetTableContigSpace::set_saved_mark() {
 950   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 951   unsigned curr_gc_time_stamp = g1h->get_gc_time_stamp();
 952 
 953   if (_gc_time_stamp < curr_gc_time_stamp) {
 954     // The order of these is important, as another thread might be
 955     // about to start scanning this region. If it does so after
 956     // set_saved_mark and before _gc_time_stamp = ..., then the latter
 957     // will be false, and it will pick up top() as the high water mark
 958     // of region. If it does so after _gc_time_stamp = ..., then it
 959     // will pick up the right saved_mark_word() as the high water mark
 960     // of the region. Either way, the behaviour will be correct.
 961     ContiguousSpace::set_saved_mark();
 962     OrderAccess::storestore();
 963     _gc_time_stamp = curr_gc_time_stamp;
 964     // No need to do another barrier to flush the writes above. If
 965     // this is called in parallel with other threads trying to
 966     // allocate into the region, the caller should call this while
 967     // holding a lock and when the lock is released the writes will be
 968     // flushed.
 969   }
 970 }
 971 
 972 G1OffsetTableContigSpace::
 973 G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
 974                          MemRegion mr) :
 975   _offsets(sharedOffsetArray, mr),
 976   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
 977   _gc_time_stamp(0)
 978 {
 979   _offsets.set_space(this);
 980   // false ==> we'll do the clearing if there's clearing to be done.
 981   ContiguousSpace::initialize(mr, false, SpaceDecorator::Mangle);
 982   _offsets.zero_bottom_entry();
 983   _offsets.initialize_threshold();
 984 }