1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_GC_SHARED_SPACE_INLINE_HPP
  26 #define SHARE_GC_SHARED_SPACE_INLINE_HPP
  27 
  28 #include "gc/shared/blockOffsetTable.inline.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "gc/shared/generation.hpp"
  31 #include "gc/shared/space.hpp"
  32 #include "gc/shared/spaceDecorator.hpp"
  33 #include "oops/oopsHierarchy.hpp"
  34 #include "oops/oop.inline.hpp"
  35 #include "runtime/prefetch.inline.hpp"
  36 #include "runtime/safepoint.hpp"
  37 #if INCLUDE_SERIALGC
  38 #include "gc/serial/markSweep.inline.hpp"
  39 #endif
  40 
  41 inline HeapWord* Space::block_start(const void* p) {
  42   return block_start_const(p);
  43 }
  44 
  45 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
  46   HeapWord* res = ContiguousSpace::allocate(size);
  47   if (res != NULL) {
  48     _offsets.alloc_block(res, size);
  49   }
  50   return res;
  51 }
  52 
  53 // Because of the requirement of keeping "_offsets" up to date with the
  54 // allocations, we sequentialize these with a lock.  Therefore, best if
  55 // this is used for larger LAB allocations only.
  56 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
  57   MutexLocker x(&_par_alloc_lock);
  58   // This ought to be just "allocate", because of the lock above, but that
  59   // ContiguousSpace::allocate asserts that either the allocating thread
  60   // holds the heap lock or it is the VM thread and we're at a safepoint.
  61   // The best I (dld) could figure was to put a field in ContiguousSpace
  62   // meaning "locking at safepoint taken care of", and set/reset that
  63   // here.  But this will do for now, especially in light of the comment
  64   // above.  Perhaps in the future some lock-free manner of keeping the
  65   // coordination.
  66   HeapWord* res = ContiguousSpace::par_allocate(size);
  67   if (res != NULL) {
  68     _offsets.alloc_block(res, size);
  69   }
  70   return res;
  71 }
  72 
  73 inline HeapWord*
  74 OffsetTableContigSpace::block_start_const(const void* p) const {
  75   return _offsets.block_start(p);
  76 }
  77 
  78 size_t CompactibleSpace::obj_size(const HeapWord* addr) const {
  79   return oop(addr)->size();
  80 }
  81 
  82 #if INCLUDE_SERIALGC
  83 
  84 class DeadSpacer : StackObj {
  85   size_t _allowed_deadspace_words;
  86   bool _active;
  87   CompactibleSpace* _space;
  88 
  89 public:
  90   DeadSpacer(CompactibleSpace* space) : _allowed_deadspace_words(0), _space(space) {
  91     size_t ratio = _space->allowed_dead_ratio();
  92     _active = ratio > 0;
  93 
  94     if (_active) {
  95       assert(!UseG1GC, "G1 should not be using dead space");
  96 
  97       // We allow some amount of garbage towards the bottom of the space, so
  98       // we don't start compacting before there is a significant gain to be made.
  99       // Occasionally, we want to ensure a full compaction, which is determined
 100       // by the MarkSweepAlwaysCompactCount parameter.
 101       if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) {
 102         _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
 103       } else {
 104         _active = false;
 105       }
 106     }
 107   }
 108 
 109 
 110   bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
 111     if (!_active) {
 112       return false;
 113     }
 114 
 115     size_t dead_length = pointer_delta(dead_end, dead_start);
 116     if (_allowed_deadspace_words >= dead_length) {
 117       _allowed_deadspace_words -= dead_length;
 118       CollectedHeap::fill_with_object(dead_start, dead_length);
 119       oop obj = oop(dead_start);
 120       obj->set_mark_raw(obj->mark_raw()->set_marked());
 121 
 122       assert(dead_length == (size_t)obj->size(), "bad filler object size");
 123       log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",
 124           p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
 125 
 126       return true;
 127     } else {
 128       _active = false;
 129       return false;
 130     }
 131   }
 132 
 133 };
 134 
 135 template <class SpaceType>
 136 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
 137   // Compute the new addresses for the live objects and store it in the mark
 138   // Used by universe::mark_sweep_phase2()
 139 
 140   // We're sure to be here before any objects are compacted into this
 141   // space, so this is a good time to initialize this:
 142   space->set_compaction_top(space->bottom());
 143 
 144   if (cp->space == NULL) {
 145     assert(cp->gen != NULL, "need a generation");
 146     assert(cp->threshold == NULL, "just checking");
 147     assert(cp->gen->first_compaction_space() == space, "just checking");
 148     cp->space = cp->gen->first_compaction_space();
 149     cp->threshold = cp->space->initialize_threshold();
 150     cp->space->set_compaction_top(cp->space->bottom());
 151   }
 152 
 153   HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
 154 
 155   DeadSpacer dead_spacer(space);
 156 
 157   HeapWord*  end_of_live = space->bottom();  // One byte beyond the last byte of the last live object.
 158   HeapWord*  first_dead = NULL; // The first dead object.
 159 
 160   const intx interval = PrefetchScanIntervalInBytes;
 161 
 162   HeapWord* cur_obj = space->bottom();
 163   HeapWord* scan_limit = space->scan_limit();
 164 
 165   while (cur_obj < scan_limit) {
 166     assert(!space->scanned_block_is_obj(cur_obj) ||
 167            oop(cur_obj)->mark_raw()->is_marked() || oop(cur_obj)->mark_raw()->is_unlocked() ||
 168            oop(cur_obj)->mark_raw()->has_bias_pattern(),
 169            "these are the only valid states during a mark sweep (" INTPTR_FORMAT ")", p2i(cur_obj));
 170     if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) {
 171       // prefetch beyond cur_obj
 172       Prefetch::write(cur_obj, interval);
 173       size_t size = space->scanned_block_size(cur_obj);
 174       compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top);
 175       cur_obj += size;
 176       end_of_live = cur_obj;
 177     } else {
 178       // run over all the contiguous dead objects
 179       HeapWord* end = cur_obj;
 180       do {
 181         // prefetch beyond end
 182         Prefetch::write(end, interval);
 183         end += space->scanned_block_size(end);
 184       } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
 185 
 186       // see if we might want to pretend this object is alive so that
 187       // we don't have to compact quite as often.
 188       if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
 189         oop obj = oop(cur_obj);
 190         compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);
 191         end_of_live = end;
 192       } else {
 193         // otherwise, it really is a free region.
 194 
 195         // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
 196         *(HeapWord**)cur_obj = end;
 197 
 198         // see if this is the first dead region.
 199         if (first_dead == NULL) {
 200           first_dead = cur_obj;
 201         }
 202       }
 203 
 204       // move on to the next object
 205       cur_obj = end;
 206     }
 207   }
 208 
 209   assert(cur_obj == scan_limit, "just checking");
 210   space->_end_of_live = end_of_live;
 211   if (first_dead != NULL) {
 212     space->_first_dead = first_dead;
 213   } else {
 214     space->_first_dead = end_of_live;
 215   }
 216 
 217   // save the compaction_top of the compaction space.
 218   cp->space->set_compaction_top(compact_top);
 219 }
 220 
 221 template <class SpaceType>
 222 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
 223   // adjust all the interior pointers to point at the new locations of objects
 224   // Used by MarkSweep::mark_sweep_phase3()
 225 
 226   HeapWord* cur_obj = space->bottom();
 227   HeapWord* const end_of_live = space->_end_of_live;  // Established by "scan_and_forward".
 228   HeapWord* const first_dead = space->_first_dead;    // Established by "scan_and_forward".
 229 
 230   assert(first_dead <= end_of_live, "Stands to reason, no?");
 231 
 232   const intx interval = PrefetchScanIntervalInBytes;
 233 
 234   debug_only(HeapWord* prev_obj = NULL);
 235   while (cur_obj < end_of_live) {
 236     Prefetch::write(cur_obj, interval);
 237     if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) {
 238       // cur_obj is alive
 239       // point all the oops to the new location
 240       size_t size = MarkSweep::adjust_pointers(oop(cur_obj));
 241       size = space->adjust_obj_size(size);
 242       debug_only(prev_obj = cur_obj);
 243       cur_obj += size;
 244     } else {
 245       debug_only(prev_obj = cur_obj);
 246       // cur_obj is not a live object, instead it points at the next live object
 247       cur_obj = *(HeapWord**)cur_obj;
 248       assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj));
 249     }
 250   }
 251 
 252   assert(cur_obj == end_of_live, "just checking");
 253 }
 254 
 255 #ifdef ASSERT
 256 template <class SpaceType>
 257 inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) {
 258   HeapWord* cur_obj = space->bottom();
 259 
 260   if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
 261      // we have a chunk of the space which hasn't moved and we've reinitialized
 262      // the mark word during the previous pass, so we can't use is_gc_marked for
 263      // the traversal.
 264      HeapWord* prev_obj = NULL;
 265 
 266      while (cur_obj < space->_first_dead) {
 267        size_t size = space->obj_size(cur_obj);
 268        assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
 269        prev_obj = cur_obj;
 270        cur_obj += size;
 271      }
 272   }
 273 }
 274 #endif
 275 
 276 template <class SpaceType>
 277 inline void CompactibleSpace::clear_empty_region(SpaceType* space) {
 278   // Let's remember if we were empty before we did the compaction.
 279   bool was_empty = space->used_region().is_empty();
 280   // Reset space after compaction is complete
 281   space->reset_after_compaction();
 282   // We do this clear, below, since it has overloaded meanings for some
 283   // space subtypes.  For example, OffsetTableContigSpace's that were
 284   // compacted into will have had their offset table thresholds updated
 285   // continuously, but those that weren't need to have their thresholds
 286   // re-initialized.  Also mangles unused area for debugging.
 287   if (space->used_region().is_empty()) {
 288     if (!was_empty) space->clear(SpaceDecorator::Mangle);
 289   } else {
 290     if (ZapUnusedHeapArea) space->mangle_unused_area();
 291   }
 292 }
 293 
 294 template <class SpaceType>
 295 inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
 296   // Copy all live objects to their new location
 297   // Used by MarkSweep::mark_sweep_phase4()
 298 
 299   verify_up_to_first_dead(space);
 300 
 301   HeapWord* const bottom = space->bottom();
 302   HeapWord* const end_of_live = space->_end_of_live;
 303 
 304   assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live));
 305   if (space->_first_dead == end_of_live && (bottom == end_of_live || !oop(bottom)->is_gc_marked())) {
 306     // Nothing to compact. The space is either empty or all live object should be left in place.
 307     clear_empty_region(space);
 308     return;
 309   }
 310 
 311   const intx scan_interval = PrefetchScanIntervalInBytes;
 312   const intx copy_interval = PrefetchCopyIntervalInBytes;
 313 
 314   assert(bottom < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(bottom), p2i(end_of_live));
 315   HeapWord* cur_obj = bottom;
 316   if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
 317     // All object before _first_dead can be skipped. They should not be moved.
 318     // A pointer to the first live object is stored at the memory location for _first_dead.
 319     cur_obj = *(HeapWord**)(space->_first_dead);
 320   }
 321 
 322   debug_only(HeapWord* prev_obj = NULL);
 323   while (cur_obj < end_of_live) {
 324     if (!oop(cur_obj)->is_gc_marked()) {
 325       debug_only(prev_obj = cur_obj);
 326       // The first word of the dead object contains a pointer to the next live object or end of space.
 327       cur_obj = *(HeapWord**)cur_obj;
 328       assert(cur_obj > prev_obj, "we should be moving forward through memory");
 329     } else {
 330       // prefetch beyond q
 331       Prefetch::read(cur_obj, scan_interval);
 332 
 333       // size and destination
 334       size_t size = space->obj_size(cur_obj);
 335       HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee();
 336 
 337       // prefetch beyond compaction_top
 338       Prefetch::write(compaction_top, copy_interval);
 339 
 340       // copy object and reinit its mark
 341       assert(cur_obj != compaction_top, "everything in this pass should be moving");
 342       Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
 343       oop(compaction_top)->init_mark_raw();
 344       assert(oop(compaction_top)->klass() != NULL, "should have a class");
 345 
 346       debug_only(prev_obj = cur_obj);
 347       cur_obj += size;
 348     }
 349   }
 350 
 351   clear_empty_region(space);
 352 }
 353 
 354 #endif // INCLUDE_SERIALGC
 355 
 356 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const {
 357   return oop(addr)->size();
 358 }
 359 
 360 template <typename OopClosureType>
 361 void ContiguousSpace::oop_since_save_marks_iterate(OopClosureType* blk) {
 362   HeapWord* t;
 363   HeapWord* p = saved_mark_word();
 364   assert(p != NULL, "expected saved mark");
 365 
 366   const intx interval = PrefetchScanIntervalInBytes;
 367   do {
 368     t = top();
 369     while (p < t) {
 370       Prefetch::write(p, interval);
 371       debug_only(HeapWord* prev = p);
 372       oop m = oop(p);
 373       p += m->oop_iterate_size(blk);
 374     }
 375   } while (t < top());
 376 
 377   set_saved_mark_word(p);
 378 }
 379 
 380 template <typename OopClosureType>
 381 void ContiguousSpace::par_oop_iterate(MemRegion mr, OopClosureType* blk) {
 382   HeapWord* obj_addr = mr.start();
 383   HeapWord* limit = mr.end();
 384   while (obj_addr < limit) {
 385     assert(oopDesc::is_oop(oop(obj_addr)), "Should be an oop");
 386     obj_addr += oop(obj_addr)->oop_iterate_size(blk);
 387   }
 388 }
 389 
 390 #endif // SHARE_GC_SHARED_SPACE_INLINE_HPP