Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "gc_implementation/shared/liveRange.hpp"

 #include "gc_implementation/shared/markSweep.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "memory/blockOffsetTable.inline.hpp"

 #include "memory/defNewGeneration.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "memory/space.hpp"

 #include "memory/space.inline.hpp"

 #include "memory/universe.inline.hpp"

 #include "oops/oop.inline.hpp"

 #include "oops/oop.inline2.hpp"

 #include "runtime/java.hpp"

 #include "runtime/prefetch.inline.hpp"

 #include "runtime/orderAccess.inline.hpp"

 #include "runtime/safepoint.hpp"

 #include "utilities/copy.hpp"

 #include "utilities/globalDefinitions.hpp"

 #include "utilities/macros.hpp"

 void SpaceMemRegionOopsIterClosure::do_oop(oop* p)       { SpaceMemRegionOopsIterClosure::do_oop_work(p); }

 void SpaceMemRegionOopsIterClosure::do_oop(narrowOop* p) { SpaceMemRegionOopsIterClosure::do_oop_work(p); }

 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

 HeapWord* DirtyCardToOopClosure::get_actual_top(HeapWord* top,

                                                 HeapWord* top_obj) {

   if (top_obj != NULL) {

     if (_sp->block_is_obj(top_obj)) {

       if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {

         if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {

           // An arrayOop is starting on the dirty card - since we do exact

           // store checks for objArrays we are done.

         } else {

           // Otherwise, it is possible that the object starting on the dirty

           // card spans the entire card, and that the store happened on a

           // later card.  Figure out where the object ends.

           // Use the block_size() method of the space over which

           // the iteration is being done.  That space (e.g. CMS) may have

           // specific requirements on object sizes which will

           // be reflected in the block_size() method.

           top = top_obj + oop(top_obj)->size();

         }

       }

     } else {

       top = top_obj;

     }

   } else {

     assert(top == _sp->end(), "only case where top_obj == NULL");

   }

   return top;

 }

 void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,

                                             HeapWord* bottom,

                                             HeapWord* top) {

   // 1. Blocks may or may not be objects.

   // 2. Even when a block_is_obj(), it may not entirely

   //    occupy the block if the block quantum is larger than

   //    the object size.

   // We can and should try to optimize by calling the non-MemRegion

   // version of oop_iterate() for all but the extremal objects

   // (for which we need to call the MemRegion version of

   // oop_iterate()) To be done post-beta XXX

   for (; bottom < top; bottom += _sp->block_size(bottom)) {

     // As in the case of contiguous space above, we'd like to

     // just use the value returned by oop_iterate to increment the

     // current pointer; unfortunately, that won't work in CMS because

     // we'd need an interface change (it seems) to have the space

     // "adjust the object size" (for instance pad it up to its

     // block alignment or minimum block size restrictions. XXX

     if (_sp->block_is_obj(bottom) &&

         !_sp->obj_allocated_since_save_marks(oop(bottom))) {

       oop(bottom)->oop_iterate(_cl, mr);

     }

   }

 }

 // We get called with "mr" representing the dirty region

 // that we want to process. Because of imprecise marking,

 // we may need to extend the incoming "mr" to the right,

 // and scan more. However, because we may already have

 // scanned some of that extended region, we may need to

 // trim its right-end back some so we do not scan what

 // we (or another worker thread) may already have scanned

 // or planning to scan.

 void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {

   // Some collectors need to do special things whenever their dirty

   // cards are processed. For instance, CMS must remember mutator updates

   // (i.e. dirty cards) so as to re-scan mutated objects.

   // Such work can be piggy-backed here on dirty card scanning, so as to make

   // it slightly more efficient than doing a complete non-detructive pre-scan

   // of the card table.

   MemRegionClosure* pCl = _sp->preconsumptionDirtyCardClosure();

   if (pCl != NULL) {

     pCl->do_MemRegion(mr);

   }

   HeapWord* bottom = mr.start();

   HeapWord* last = mr.last();

   HeapWord* top = mr.end();

   HeapWord* bottom_obj;

   HeapWord* top_obj;

   assert(_precision == CardTableModRefBS::ObjHeadPreciseArray ||

          _precision == CardTableModRefBS::Precise,

          "Only ones we deal with for now.");

   assert(_precision != CardTableModRefBS::ObjHeadPreciseArray ||

          _cl->idempotent() || _last_bottom == NULL ||

          top <= _last_bottom,

          "Not decreasing");

   NOT_PRODUCT(_last_bottom = mr.start());

   bottom_obj = _sp->block_start(bottom);

   top_obj    = _sp->block_start(last);

   assert(bottom_obj <= bottom, "just checking");

   assert(top_obj    <= top,    "just checking");

   // Given what we think is the top of the memory region and

   // the start of the object at the top, get the actual

   // value of the top.

   top = get_actual_top(top, top_obj);

   // If the previous call did some part of this region, don't redo.

   if (_precision == CardTableModRefBS::ObjHeadPreciseArray &&

       _min_done != NULL &&

       _min_done < top) {

     top = _min_done;

   }

   // Top may have been reset, and in fact may be below bottom,

   // e.g. the dirty card region is entirely in a now free object

   // -- something that could happen with a concurrent sweeper.

   bottom = MIN2(bottom, top);

   MemRegion extended_mr = MemRegion(bottom, top);

   assert(bottom <= top &&

          (_precision != CardTableModRefBS::ObjHeadPreciseArray ||

           _min_done == NULL ||

           top <= _min_done),

          "overlap!");

   // Walk the region if it is not empty; otherwise there is nothing to do.

   if (!extended_mr.is_empty()) {

     walk_mem_region(extended_mr, bottom_obj, top);

   }

   // An idempotent closure might be applied in any order, so we don't

   // record a _min_done for it.

   if (!_cl->idempotent()) {

     _min_done = bottom;

   } else {

     assert(_min_done == _last_explicit_min_done,

            "Don't update _min_done for idempotent cl");

   }

 }

 DirtyCardToOopClosure* Space::new_dcto_cl(ExtendedOopClosure* cl,

                                           CardTableModRefBS::PrecisionStyle precision,

                                           HeapWord* boundary) {

   return new DirtyCardToOopClosure(this, cl, precision, boundary);

 }

 HeapWord* ContiguousSpaceDCTOC::get_actual_top(HeapWord* top,

                                                HeapWord* top_obj) {

   if (top_obj != NULL && top_obj < (_sp->toContiguousSpace())->top()) {

     if (_precision == CardTableModRefBS::ObjHeadPreciseArray) {

       if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {

         // An arrayOop is starting on the dirty card - since we do exact

         // store checks for objArrays we are done.

       } else {

         // Otherwise, it is possible that the object starting on the dirty

         // card spans the entire card, and that the store happened on a

         // later card.  Figure out where the object ends.

         assert(_sp->block_size(top_obj) == (size_t) oop(top_obj)->size(),

           "Block size and object size mismatch");

         top = top_obj + oop(top_obj)->size();

       }

     }

   } else {

     top = (_sp->toContiguousSpace())->top();

   }

   return top;

 }

 void Filtering_DCTOC::walk_mem_region(MemRegion mr,

                                       HeapWord* bottom,

                                       HeapWord* top) {

   // Note that this assumption won't hold if we have a concurrent

   // collector in this space, which may have freed up objects after

   // they were dirtied and before the stop-the-world GC that is

   // examining cards here.

   assert(bottom < top, "ought to be at least one obj on a dirty card.");

   if (_boundary != NULL) {

     // We have a boundary outside of which we don't want to look

     // at objects, so create a filtering closure around the

     // oop closure before walking the region.

     FilteringClosure filter(_boundary, _cl);

     walk_mem_region_with_cl(mr, bottom, top, &filter);

   } else {

     // No boundary, simply walk the heap with the oop closure.

     walk_mem_region_with_cl(mr, bottom, top, _cl);

   }

 }

 // We must replicate this so that the static type of "FilteringClosure"

 // (see above) is apparent at the oop_iterate calls.

 #define ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \

 void ContiguousSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr,        \

                                                    HeapWord* bottom,    \

                                                    HeapWord* top,       \

                                                    ClosureType* cl) {   \

   bottom += oop(bottom)->oop_iterate(cl, mr);                           \

   if (bottom < top) {                                                   \

     HeapWord* next_obj = bottom + oop(bottom)->size();                  \

     while (next_obj < top) {                                            \

       /* Bottom lies entirely below top, so we can call the */          \

       /* non-memRegion version of oop_iterate below. */                 \

       oop(bottom)->oop_iterate(cl);                                     \

       bottom = next_obj;                                                \

       next_obj = bottom + oop(bottom)->size();                          \

     }                                                                   \

     /* Last object. */                                                  \

     oop(bottom)->oop_iterate(cl, mr);                                   \

   }                                                                     \

 }

 // (There are only two of these, rather than N, because the split is due

 // only to the introduction of the FilteringClosure, a local part of the

 // impl of this abstraction.)

 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(ExtendedOopClosure)

 ContiguousSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)

 DirtyCardToOopClosure*

 ContiguousSpace::new_dcto_cl(ExtendedOopClosure* cl,

                              CardTableModRefBS::PrecisionStyle precision,

                              HeapWord* boundary) {

   return new ContiguousSpaceDCTOC(this, cl, precision, boundary);

 }

 void Space::initialize(MemRegion mr,

                        bool clear_space,

                        bool mangle_space) {

   HeapWord* bottom = mr.start();

   HeapWord* end    = mr.end();

   assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),

          "invalid space boundaries");

   set_bottom(bottom);

   set_end(end);

   if (clear_space) clear(mangle_space);

 }

 void Space::clear(bool mangle_space) {

   if (ZapUnusedHeapArea && mangle_space) {

     mangle_unused_area();

   }

 }

 ContiguousSpace::ContiguousSpace(): CompactibleSpace(), _top(NULL),

     _concurrent_iteration_safe_limit(NULL) {

   _mangler = new GenSpaceMangler(this);

 }

 ContiguousSpace::~ContiguousSpace() {

   delete _mangler;

 }

 void ContiguousSpace::initialize(MemRegion mr,

                                  bool clear_space,

                                  bool mangle_space)

 {

   CompactibleSpace::initialize(mr, clear_space, mangle_space);

   set_concurrent_iteration_safe_limit(top());

 }

 void ContiguousSpace::clear(bool mangle_space) {

   set_top(bottom());

   set_saved_mark();

   CompactibleSpace::clear(mangle_space);

 }

 bool ContiguousSpace::is_in(const void* p) const {

   return _bottom <= p && p < _top;

 }

 bool ContiguousSpace::is_free_block(const HeapWord* p) const {

   return p >= _top;

 }

 void OffsetTableContigSpace::clear(bool mangle_space) {

   ContiguousSpace::clear(mangle_space);

   _offsets.initialize_threshold();

 }

 void OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {

   Space::set_bottom(new_bottom);

   _offsets.set_bottom(new_bottom);

 }

 void OffsetTableContigSpace::set_end(HeapWord* new_end) {

   // Space should not advertize an increase in size

   // until after the underlying offest table has been enlarged.

   _offsets.resize(pointer_delta(new_end, bottom()));

   Space::set_end(new_end);

 }

 #ifndef PRODUCT

 void ContiguousSpace::set_top_for_allocations(HeapWord* v) {

   mangler()->set_top_for_allocations(v);

 }

 void ContiguousSpace::set_top_for_allocations() {

   mangler()->set_top_for_allocations(top());

 }

 void ContiguousSpace::check_mangled_unused_area(HeapWord* limit) {

   mangler()->check_mangled_unused_area(limit);

 }

 void ContiguousSpace::check_mangled_unused_area_complete() {

   mangler()->check_mangled_unused_area_complete();

 }

 // Mangled only the unused space that has not previously

 // been mangled and that has not been allocated since being

 // mangled.

 void ContiguousSpace::mangle_unused_area() {

   mangler()->mangle_unused_area();

 }

 void ContiguousSpace::mangle_unused_area_complete() {

   mangler()->mangle_unused_area_complete();

 }

 void ContiguousSpace::mangle_region(MemRegion mr) {

   // Although this method uses SpaceMangler::mangle_region() which

   // is not specific to a space, the when the ContiguousSpace version

   // is called, it is always with regard to a space and this

   // bounds checking is appropriate.

   MemRegion space_mr(bottom(), end());

   assert(space_mr.contains(mr), "Mangling outside space");

   SpaceMangler::mangle_region(mr);

 }

 #endif  // NOT_PRODUCT

 void CompactibleSpace::initialize(MemRegion mr,

                                   bool clear_space,

                                   bool mangle_space) {

   Space::initialize(mr, clear_space, mangle_space);

   set_compaction_top(bottom());

   _next_compaction_space = NULL;

 }

 void CompactibleSpace::clear(bool mangle_space) {

   Space::clear(mangle_space);

   _compaction_top = bottom();

 }

 HeapWord* CompactibleSpace::forward(oop q, size_t size,

                                     CompactPoint* cp, HeapWord* compact_top) {

   // q is alive

   // First check if we should switch compaction space

   assert(this == cp->space, "'this' should be current compaction space.");

   size_t compaction_max_size = pointer_delta(end(), compact_top);

   while (size > compaction_max_size) {

     // switch to next compaction space

     cp->space->set_compaction_top(compact_top);

     cp->space = cp->space->next_compaction_space();

     if (cp->space == NULL) {

       cp->gen = GenCollectedHeap::heap()->prev_gen(cp->gen);

       assert(cp->gen != NULL, "compaction must succeed");

       cp->space = cp->gen->first_compaction_space();

       assert(cp->space != NULL, "generation must have a first compaction space");

     }

     compact_top = cp->space->bottom();

     cp->space->set_compaction_top(compact_top);

     cp->threshold = cp->space->initialize_threshold();

     compaction_max_size = pointer_delta(cp->space->end(), compact_top);

   }

   // store the forwarding pointer into the mark word

   if ((HeapWord*)q != compact_top) {

     q->forward_to(oop(compact_top));

     assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");

   } else {

     // if the object isn't moving we can just set the mark to the default

     // mark and handle it specially later on.

     q->init_mark();

     assert(q->forwardee() == NULL, "should be forwarded to NULL");

   }

   compact_top += size;

   // we need to update the offset table so that the beginnings of objects can be

   // found during scavenge.  Note that we are updating the offset table based on

   // where the object will be once the compaction phase finishes.

   if (compact_top > cp->threshold)

     cp->threshold =

       cp->space->cross_threshold(compact_top - size, compact_top);

   return compact_top;

 }

 bool CompactibleSpace::insert_deadspace(size_t& allowed_deadspace_words,

                                         HeapWord* q, size_t deadlength) {

   if (allowed_deadspace_words >= deadlength) {

     allowed_deadspace_words -= deadlength;

     CollectedHeap::fill_with_object(q, deadlength);

     oop(q)->set_mark(oop(q)->mark()->set_marked());

     assert((int) deadlength == oop(q)->size(), "bad filler object size");

     // Recall that we required "q == compaction_top".

     return true;

   } else {

     allowed_deadspace_words = 0;

     return false;

   }

 }

 #define block_is_always_obj(q) true

 #define obj_size(q) oop(q)->size()

 #define adjust_obj_size(s) s

 void CompactibleSpace::prepare_for_compaction(CompactPoint* cp) {

   SCAN_AND_FORWARD(cp, end, block_is_obj, block_size);

 }

 // Faster object search.

 void ContiguousSpace::prepare_for_compaction(CompactPoint* cp) {

   SCAN_AND_FORWARD(cp, top, block_is_always_obj, obj_size);

 }

 void Space::adjust_pointers() {

   // adjust all the interior pointers to point at the new locations of objects

   // Used by MarkSweep::mark_sweep_phase3()

   // First check to see if there is any work to be done.

   if (used() == 0) {

     return;  // Nothing to do.

   }

   // Otherwise...

   HeapWord* q = bottom();

   HeapWord* t = end();

   debug_only(HeapWord* prev_q = NULL);

   while (q < t) {

     if (oop(q)->is_gc_marked()) {

       // q is alive

       // point all the oops to the new location

       size_t size = oop(q)->adjust_pointers();

       debug_only(prev_q = q);

       q += size;

     } else {

       // q is not a live object.  But we're not in a compactible space,

       // So we don't have live ranges.

       debug_only(prev_q = q);

       q += block_size(q);

       assert(q > prev_q, "we should be moving forward through memory");

     }

   }

   assert(q == t, "just checking");

 }

 void CompactibleSpace::adjust_pointers() {

   // Check first is there is any work to do.

   if (used() == 0) {

     return;   // Nothing to do.

   }

   SCAN_AND_ADJUST_POINTERS(adjust_obj_size);

 }

 void CompactibleSpace::compact() {

   SCAN_AND_COMPACT(obj_size);

 }

 void Space::print_short() const { print_short_on(tty); }

 void Space::print_short_on(outputStream* st) const {

   st->print(" space " SIZE_FORMAT "K, %3d%% used", capacity() / K,

               (int) ((double) used() * 100 / capacity()));

 }

 void Space::print() const { print_on(tty); }

 void Space::print_on(outputStream* st) const {

   print_short_on(st);

   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ")",

                 bottom(), end());

 }

 void ContiguousSpace::print_on(outputStream* st) const {

   print_short_on(st);

   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",

                 bottom(), top(), end());

 }

 void OffsetTableContigSpace::print_on(outputStream* st) const {

   print_short_on(st);

   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "

                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",

               bottom(), top(), _offsets.threshold(), end());

 }

 void ContiguousSpace::verify() const {

   HeapWord* p = bottom();

   HeapWord* t = top();

   HeapWord* prev_p = NULL;

   while (p < t) {

     oop(p)->verify();

     prev_p = p;

     p += oop(p)->size();

   }

   guarantee(p == top(), "end of last object must match end of space");

   if (top() != end()) {

     guarantee(top() == block_start_const(end()-1) &&

               top() == block_start_const(top()),

               "top should be start of unallocated block, if it exists");

   }

 }

 void Space::oop_iterate(ExtendedOopClosure* blk) {

   ObjectToOopClosure blk2(blk);

   object_iterate(&blk2);

 }

 HeapWord* Space::object_iterate_careful(ObjectClosureCareful* cl) {

   guarantee(false, "NYI");

   return bottom();

 }

 HeapWord* Space::object_iterate_careful_m(MemRegion mr,

                                           ObjectClosureCareful* cl) {

   guarantee(false, "NYI");

   return bottom();

 }

 void Space::object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl) {

   assert(!mr.is_empty(), "Should be non-empty");

   // We use MemRegion(bottom(), end()) rather than used_region() below

   // because the two are not necessarily equal for some kinds of

   // spaces, in particular, certain kinds of free list spaces.

   // We could use the more complicated but more precise:

   // MemRegion(used_region().start(), round_to(used_region().end(), CardSize))

   // but the slight imprecision seems acceptable in the assertion check.

   assert(MemRegion(bottom(), end()).contains(mr),

          "Should be within used space");

   HeapWord* prev = cl->previous();   // max address from last time

   if (prev >= mr.end()) { // nothing to do

     return;

   }

   // This assert will not work when we go from cms space to perm

   // space, and use same closure. Easy fix deferred for later. XXX YSR

   // assert(prev == NULL || contains(prev), "Should be within space");

   bool last_was_obj_array = false;

   HeapWord *blk_start_addr, *region_start_addr;

   if (prev > mr.start()) {

     region_start_addr = prev;

     blk_start_addr    = prev;

     // The previous invocation may have pushed "prev" beyond the

     // last allocated block yet there may be still be blocks

     // in this region due to a particular coalescing policy.

     // Relax the assertion so that the case where the unallocated

     // block is maintained and "prev" is beyond the unallocated

     // block does not cause the assertion to fire.

     assert((BlockOffsetArrayUseUnallocatedBlock &&

             (!is_in(prev))) ||

            (blk_start_addr == block_start(region_start_addr)), "invariant");

   } else {

     region_start_addr = mr.start();

     blk_start_addr    = block_start(region_start_addr);

   }

   HeapWord* region_end_addr = mr.end();

   MemRegion derived_mr(region_start_addr, region_end_addr);

   while (blk_start_addr < region_end_addr) {

     const size_t size = block_size(blk_start_addr);

     if (block_is_obj(blk_start_addr)) {

       last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);

     } else {

       last_was_obj_array = false;

     }

     blk_start_addr += size;

   }

   if (!last_was_obj_array) {

     assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),

            "Should be within (closed) used space");

     assert(blk_start_addr > prev, "Invariant");

     cl->set_previous(blk_start_addr); // min address for next time

   }

 }

 bool Space::obj_is_alive(const HeapWord* p) const {

   assert (block_is_obj(p), "The address should point to an object");

   return true;

 }

 void ContiguousSpace::object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl) {

   assert(!mr.is_empty(), "Should be non-empty");

   assert(used_region().contains(mr), "Should be within used space");

   HeapWord* prev = cl->previous();   // max address from last time

   if (prev >= mr.end()) { // nothing to do

     return;

   }

   // See comment above (in more general method above) in case you

   // happen to use this method.

   assert(prev == NULL || is_in_reserved(prev), "Should be within space");

   bool last_was_obj_array = false;

   HeapWord *obj_start_addr, *region_start_addr;

   if (prev > mr.start()) {

     region_start_addr = prev;

     obj_start_addr    = prev;

     assert(obj_start_addr == block_start(region_start_addr), "invariant");

   } else {

     region_start_addr = mr.start();

     obj_start_addr    = block_start(region_start_addr);

   }

   HeapWord* region_end_addr = mr.end();

   MemRegion derived_mr(region_start_addr, region_end_addr);

   while (obj_start_addr < region_end_addr) {

     oop obj = oop(obj_start_addr);

     const size_t size = obj->size();

     last_was_obj_array = cl->do_object_bm(obj, derived_mr);

     obj_start_addr += size;

   }

   if (!last_was_obj_array) {

     assert((bottom() <= obj_start_addr)  && (obj_start_addr <= end()),

            "Should be within (closed) used space");

     assert(obj_start_addr > prev, "Invariant");

     cl->set_previous(obj_start_addr); // min address for next time

   }

 }

 #if INCLUDE_ALL_GCS

 #define ContigSpace_PAR_OOP_ITERATE_DEFN(OopClosureType, nv_suffix)         \

                                                                             \

   void ContiguousSpace::par_oop_iterate(MemRegion mr, OopClosureType* blk) {\

     HeapWord* obj_addr = mr.start();                                        \

     HeapWord* t = mr.end();                                                 \

     while (obj_addr < t) {                                                  \

       assert(oop(obj_addr)->is_oop(), "Should be an oop");                  \

       obj_addr += oop(obj_addr)->oop_iterate(blk);                          \

     }                                                                       \

   }

   ALL_PAR_OOP_ITERATE_CLOSURES(ContigSpace_PAR_OOP_ITERATE_DEFN)

 #undef ContigSpace_PAR_OOP_ITERATE_DEFN

 #endif // INCLUDE_ALL_GCS

 void ContiguousSpace::oop_iterate(ExtendedOopClosure* blk) {

   if (is_empty()) return;

   HeapWord* obj_addr = bottom();

   HeapWord* t = top();

   // Could call objects iterate, but this is easier.

   while (obj_addr < t) {

     obj_addr += oop(obj_addr)->oop_iterate(blk);

   }

 }

 void ContiguousSpace::oop_iterate(MemRegion mr, ExtendedOopClosure* blk) {

   if (is_empty()) {

     return;

   }

   MemRegion cur = MemRegion(bottom(), top());

   mr = mr.intersection(cur);

   if (mr.is_empty()) {

     return;

   }

   if (mr.equals(cur)) {

     oop_iterate(blk);

     return;

   }

   assert(mr.end() <= top(), "just took an intersection above");

   HeapWord* obj_addr = block_start(mr.start());

   HeapWord* t = mr.end();

   // Handle first object specially.

   oop obj = oop(obj_addr);

   SpaceMemRegionOopsIterClosure smr_blk(blk, mr);

   obj_addr += obj->oop_iterate(&smr_blk);

   while (obj_addr < t) {

     oop obj = oop(obj_addr);

     assert(obj->is_oop(), "expected an oop");

     obj_addr += obj->size();

     // If "obj_addr" is not greater than top, then the

     // entire object "obj" is within the region.

     if (obj_addr <= t) {

       obj->oop_iterate(blk);

     } else {

       // "obj" extends beyond end of region

       obj->oop_iterate(&smr_blk);

       break;

     }

   };

 }

 void ContiguousSpace::object_iterate(ObjectClosure* blk) {

   if (is_empty()) return;

   WaterMark bm = bottom_mark();

   object_iterate_from(bm, blk);

 }

 // For a continguous space object_iterate() and safe_object_iterate()

 // are the same.

 void ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {

   object_iterate(blk);

 }

 void ContiguousSpace::object_iterate_from(WaterMark mark, ObjectClosure* blk) {

   assert(mark.space() == this, "Mark does not match space");

   HeapWord* p = mark.point();

   while (p < top()) {

     blk->do_object(oop(p));

     p += oop(p)->size();

   }

 }

 HeapWord*

 ContiguousSpace::object_iterate_careful(ObjectClosureCareful* blk) {

   HeapWord * limit = concurrent_iteration_safe_limit();

   assert(limit <= top(), "sanity check");

   for (HeapWord* p = bottom(); p < limit;) {

     size_t size = blk->do_object_careful(oop(p));

     if (size == 0) {

       return p;  // failed at p

     } else {

       p += size;

     }

   }

   return NULL; // all done

 }

 #define ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix)  \

                                                                           \

 void ContiguousSpace::                                                    \

 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) {            \

   HeapWord* t;                                                            \

   HeapWord* p = saved_mark_word();                                        \

   assert(p != NULL, "expected saved mark");                               \

                                                                           \

   const intx interval = PrefetchScanIntervalInBytes;                      \

   do {                                                                    \

     t = top();                                                            \

     while (p < t) {                                                       \

       Prefetch::write(p, interval);                                       \

       debug_only(HeapWord* prev = p);                                     \

       oop m = oop(p);                                                     \

       p += m->oop_iterate(blk);                                           \

     }                                                                     \

   } while (t < top());                                                    \

                                                                           \

   set_saved_mark_word(p);                                                 \

 }

 ALL_SINCE_SAVE_MARKS_CLOSURES(ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN)

 #undef ContigSpace_OOP_SINCE_SAVE_MARKS_DEFN

 // Very general, slow implementation.

 HeapWord* ContiguousSpace::block_start_const(const void* p) const {

   assert(MemRegion(bottom(), end()).contains(p),

          err_msg("p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",

                   p, bottom(), end()));

   if (p >= top()) {

     return top();

   } else {

     HeapWord* last = bottom();

     HeapWord* cur = last;

     while (cur <= p) {

       last = cur;

       cur += oop(cur)->size();

     }

     assert(oop(last)->is_oop(),

            err_msg(PTR_FORMAT " should be an object start", last));

     return last;

   }

 }

 size_t ContiguousSpace::block_size(const HeapWord* p) const {

   assert(MemRegion(bottom(), end()).contains(p),

          err_msg("p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",

                   p, bottom(), end()));

   HeapWord* current_top = top();

   assert(p <= current_top,

          err_msg("p > current top - p: " PTR_FORMAT ", current top: " PTR_FORMAT,

                   p, current_top));

   assert(p == current_top || oop(p)->is_oop(),

          err_msg("p (" PTR_FORMAT ") is not a block start - "

                  "current_top: " PTR_FORMAT ", is_oop: %s",

                  p, current_top, BOOL_TO_STR(oop(p)->is_oop())));

   if (p < current_top) {

     return oop(p)->size();

   } else {

     assert(p == current_top, "just checking");

     return pointer_delta(end(), (HeapWord*) p);

   }

 }

 // This version requires locking.

 inline HeapWord* ContiguousSpace::allocate_impl(size_t size,

                                                 HeapWord* const end_value) {

   // In G1 there are places where a GC worker can allocates into a

   // region using this serial allocation code without being prone to a

   // race with other GC workers (we ensure that no other GC worker can

   // access the same region at the same time). So the assert below is

   // too strong in the case of G1.

   assert(Heap_lock->owned_by_self() ||

          (SafepointSynchronize::is_at_safepoint() &&

                                (Thread::current()->is_VM_thread() || UseG1GC)),

          "not locked");

   HeapWord* obj = top();

   if (pointer_delta(end_value, obj) >= size) {

     HeapWord* new_top = obj + size;

     set_top(new_top);

     assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");

     return obj;

   } else {

     return NULL;

   }

 }

 // This version is lock-free.

 inline HeapWord* ContiguousSpace::par_allocate_impl(size_t size,

                                                     HeapWord* const end_value) {

   do {

     HeapWord* obj = top();

     if (pointer_delta(end_value, obj) >= size) {

       HeapWord* new_top = obj + size;

       HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);

       // result can be one of two:

       //  the old top value: the exchange succeeded

       //  otherwise: the new value of the top is returned.

       if (result == obj) {

         assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");

         return obj;

       }

     } else {

       return NULL;

     }

   } while (true);

 }

 // Requires locking.

 HeapWord* ContiguousSpace::allocate(size_t size) {

   return allocate_impl(size, end());

 }

 // Lock-free.

 HeapWord* ContiguousSpace::par_allocate(size_t size) {

   return par_allocate_impl(size, end());

 }

 void ContiguousSpace::allocate_temporary_filler(int factor) {

   // allocate temporary type array decreasing free size with factor 'factor'

   assert(factor >= 0, "just checking");

   size_t size = pointer_delta(end(), top());

   // if space is full, return

   if (size == 0) return;

   if (factor > 0) {

     size -= size/factor;

   }

   size = align_object_size(size);

   const size_t array_header_size = typeArrayOopDesc::header_size(T_INT);

   if (size >= (size_t)align_object_size(array_header_size)) {

     size_t length = (size - array_header_size) * (HeapWordSize / sizeof(jint));

     // allocate uninitialized int array

     typeArrayOop t = (typeArrayOop) allocate(size);

     assert(t != NULL, "allocation should succeed");

     t->set_mark(markOopDesc::prototype());

     t->set_klass(Universe::intArrayKlassObj());

     t->set_length((int)length);

   } else {

     assert(size == CollectedHeap::min_fill_size(),

            "size for smallest fake object doesn't match");

     instanceOop obj = (instanceOop) allocate(size);

     obj->set_mark(markOopDesc::prototype());

     obj->set_klass_gap(0);

     obj->set_klass(SystemDictionary::Object_klass());

   }

 }

 void EdenSpace::clear(bool mangle_space) {

   ContiguousSpace::clear(mangle_space);

   set_soft_end(end());

 }

 // Requires locking.

 HeapWord* EdenSpace::allocate(size_t size) {

   return allocate_impl(size, soft_end());

 }

 // Lock-free.

 HeapWord* EdenSpace::par_allocate(size_t size) {

   return par_allocate_impl(size, soft_end());

 }

 HeapWord* ConcEdenSpace::par_allocate(size_t size)

 {

   do {

     // The invariant is top() should be read before end() because

     // top() can't be greater than end(), so if an update of _soft_end

     // occurs between 'end_val = end();' and 'top_val = top();' top()

     // also can grow up to the new end() and the condition

     // 'top_val > end_val' is true. To ensure the loading order

     // OrderAccess::loadload() is required after top() read.

     HeapWord* obj = top();

     OrderAccess::loadload();

     if (pointer_delta(*soft_end_addr(), obj) >= size) {

       HeapWord* new_top = obj + size;

       HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);

       // result can be one of two:

       //  the old top value: the exchange succeeded

       //  otherwise: the new value of the top is returned.

       if (result == obj) {

         assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");

         return obj;

       }

     } else {

       return NULL;

     }

   } while (true);

 }

 HeapWord* OffsetTableContigSpace::initialize_threshold() {

   return _offsets.initialize_threshold();

 }

 HeapWord* OffsetTableContigSpace::cross_threshold(HeapWord* start, HeapWord* end) {

   _offsets.alloc_block(start, end);

   return _offsets.threshold();

 }

 OffsetTableContigSpace::OffsetTableContigSpace(BlockOffsetSharedArray* sharedOffsetArray,

                                                MemRegion mr) :

   _offsets(sharedOffsetArray, mr),

   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true)

 {

   _offsets.set_contig_space(this);

   initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);

 }

 #define OBJ_SAMPLE_INTERVAL 0

 #define BLOCK_SAMPLE_INTERVAL 100

 void OffsetTableContigSpace::verify() const {

   HeapWord* p = bottom();

   HeapWord* prev_p = NULL;

   int objs = 0;

   int blocks = 0;

   if (VerifyObjectStartArray) {

     _offsets.verify();

   }

   while (p < top()) {

     size_t size = oop(p)->size();

     // For a sampling of objects in the space, find it using the

     // block offset table.

     if (blocks == BLOCK_SAMPLE_INTERVAL) {

       guarantee(p == block_start_const(p + (size/2)),

                 "check offset computation");

       blocks = 0;

     } else {

       blocks++;

     }

     if (objs == OBJ_SAMPLE_INTERVAL) {

       oop(p)->verify();

       objs = 0;

     } else {

       objs++;

     }

     prev_p = p;

     p += size;

   }

   guarantee(p == top(), "end of last object must match end of space");

 }

 size_t TenuredSpace::allowed_dead_ratio() const {

   return MarkSweepDeadRatio;

 }