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 /*

  * Copyright (c) 2001, 2012, 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 "gc_implementation/parallelScavenge/objectStartArray.hpp"

 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"

 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"

 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"

 #include "gc_implementation/shared/liveRange.hpp"

 #include "gc_implementation/shared/markSweep.inline.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "oops/oop.inline.hpp"

 PSMarkSweepDecorator* PSMarkSweepDecorator::_destination_decorator = NULL;

 void PSMarkSweepDecorator::set_destination_decorator_tenured() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   _destination_decorator = heap->old_gen()->object_mark_sweep();

 }

 void PSMarkSweepDecorator::advance_destination_decorator() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   assert(_destination_decorator != NULL, "Sanity");

   PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep();

   PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep();

   PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep();

   PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep();

   if ( _destination_decorator == first ) {

     _destination_decorator = second;

   } else if ( _destination_decorator == second ) {

     _destination_decorator = third;

   } else if ( _destination_decorator == third ) {

     _destination_decorator = fourth;

   } else {

     fatal("PSMarkSweep attempting to advance past last compaction area");

   }

 }

 PSMarkSweepDecorator* PSMarkSweepDecorator::destination_decorator() {

   assert(_destination_decorator != NULL, "Sanity");

   return _destination_decorator;

 }

 // FIX ME FIX ME FIX ME FIX ME!!!!!!!!!

 // The object forwarding code is duplicated. Factor this out!!!!!

 //

 // This method "precompacts" objects inside its space to dest. It places forwarding

 // pointers into markOops for use by adjust_pointers. If "dest" should overflow, we

 // finish by compacting into our own space.

 void PSMarkSweepDecorator::precompact() {

   // Reset our own compact top.

   set_compaction_top(space()->bottom());

   /* We allow some amount of garbage towards the bottom of the space, so

    * we don't start compacting before there is a significant gain to be made.

    * Occasionally, we want to ensure a full compaction, which is determined

    * by the MarkSweepAlwaysCompactCount parameter. This is a significant

    * performance improvement!

    */

   bool skip_dead = ((PSMarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0);

   size_t allowed_deadspace = 0;

   if (skip_dead) {

     const size_t ratio = allowed_dead_ratio();

     allowed_deadspace = space()->capacity_in_words() * ratio / 100;

   }

   // Fetch the current destination decorator

   PSMarkSweepDecorator* dest = destination_decorator();

   ObjectStartArray* start_array = dest->start_array();

   HeapWord* compact_top = dest->compaction_top();

   HeapWord* compact_end = dest->space()->end();

   HeapWord* q = space()->bottom();

   HeapWord* t = space()->top();

   HeapWord*  end_of_live= q;    /* One byte beyond the last byte of the last

                                    live object. */

   HeapWord*  first_dead = space()->end(); /* The first dead object. */

   LiveRange* liveRange  = NULL; /* The current live range, recorded in the

                                    first header of preceding free area. */

   _first_dead = first_dead;

   const intx interval = PrefetchScanIntervalInBytes;

   while (q < t) {

     assert(oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||

            oop(q)->mark()->has_bias_pattern(),

            "these are the only valid states during a mark sweep");

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

       /* prefetch beyond q */

       Prefetch::write(q, interval);

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

       size_t compaction_max_size = pointer_delta(compact_end, compact_top);

       // This should only happen if a space in the young gen overflows the

       // old gen. If that should happen, we null out the start_array, because

       // the young spaces are not covered by one.

       while(size > compaction_max_size) {

         // First record the last compact_top

         dest->set_compaction_top(compact_top);

         // Advance to the next compaction decorator

         advance_destination_decorator();

         dest = destination_decorator();

         // Update compaction info

         start_array = dest->start_array();

         compact_top = dest->compaction_top();

         compact_end = dest->space()->end();

         assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");

         assert(compact_end > compact_top, "Must always be space remaining");

         compaction_max_size =

           pointer_delta(compact_end, compact_top);

       }

       // store the forwarding pointer into the mark word

       if (q != compact_top) {

         oop(q)->forward_to(oop(compact_top));

         assert(oop(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.

         oop(q)->init_mark();

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

       }

       // Update object start array

       if (start_array) {

         start_array->allocate_block(compact_top);

       }

       compact_top += size;

       assert(compact_top <= dest->space()->end(),

         "Exceeding space in destination");

       q += size;

       end_of_live = q;

     } else {

       /* run over all the contiguous dead objects */

       HeapWord* end = q;

       do {

         /* prefetch beyond end */

         Prefetch::write(end, interval);

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

       } while (end < t && (!oop(end)->is_gc_marked()));

       /* see if we might want to pretend this object is alive so that

        * we don't have to compact quite as often.

        */

       if (allowed_deadspace > 0 && q == compact_top) {

         size_t sz = pointer_delta(end, q);

         if (insert_deadspace(allowed_deadspace, q, sz)) {

           size_t compaction_max_size = pointer_delta(compact_end, compact_top);

           // This should only happen if a space in the young gen overflows the

           // old gen. If that should happen, we null out the start_array, because

           // the young spaces are not covered by one.

           while (sz > compaction_max_size) {

             // First record the last compact_top

             dest->set_compaction_top(compact_top);

             // Advance to the next compaction decorator

             advance_destination_decorator();

             dest = destination_decorator();

             // Update compaction info

             start_array = dest->start_array();

             compact_top = dest->compaction_top();

             compact_end = dest->space()->end();

             assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");

             assert(compact_end > compact_top, "Must always be space remaining");

             compaction_max_size =

               pointer_delta(compact_end, compact_top);

           }

           // store the forwarding pointer into the mark word

           if (q != compact_top) {

             oop(q)->forward_to(oop(compact_top));

             assert(oop(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.

             oop(q)->init_mark();

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

           }

           // Update object start array

           if (start_array) {

             start_array->allocate_block(compact_top);

           }

           compact_top += sz;

           assert(compact_top <= dest->space()->end(),

             "Exceeding space in destination");

           q = end;

           end_of_live = end;

           continue;

         }

       }

       /* for the previous LiveRange, record the end of the live objects. */

       if (liveRange) {

         liveRange->set_end(q);

       }

       /* record the current LiveRange object.

        * liveRange->start() is overlaid on the mark word.

        */

       liveRange = (LiveRange*)q;

       liveRange->set_start(end);

       liveRange->set_end(end);

       /* see if this is the first dead region. */

       if (q < first_dead) {

         first_dead = q;

       }

       /* move on to the next object */

       q = end;

     }

   }

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

   if (liveRange != NULL) {

     liveRange->set_end(q);

   }

   _end_of_live = end_of_live;

   if (end_of_live < first_dead) {

     first_dead = end_of_live;

   }

   _first_dead = first_dead;

   // Update compaction top

   dest->set_compaction_top(compact_top);

 }

 bool PSMarkSweepDecorator::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;

   }

 }

 void PSMarkSweepDecorator::adjust_pointers() {

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

   // Used by MarkSweep::mark_sweep_phase3()

   HeapWord* q = space()->bottom();

   HeapWord* t = _end_of_live;  // Established by "prepare_for_compaction".

   assert(_first_dead <= _end_of_live, "Stands to reason, no?");

   if (q < t && _first_dead > q &&

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

     // we have a chunk of the space which hasn't moved and we've

     // reinitialized the mark word during the previous pass, so we can't

     // use is_gc_marked for the traversal.

     HeapWord* end = _first_dead;

     while (q < end) {

       // point all the oops to the new location

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

       q += size;

     }

     if (_first_dead == t) {

       q = t;

     } else {

       // $$$ This is funky.  Using this to read the previously written

       // LiveRange.  See also use below.

       q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer();

     }

   }

   const intx interval = PrefetchScanIntervalInBytes;

   debug_only(HeapWord* prev_q = NULL);

   while (q < t) {

     // prefetch beyond q

     Prefetch::write(q, interval);

     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, so its mark should point at the next

       // live object

       debug_only(prev_q = q);

       q = (HeapWord*) oop(q)->mark()->decode_pointer();

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

     }

   }

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

 }

 void PSMarkSweepDecorator::compact(bool mangle_free_space ) {

   // Copy all live objects to their new location

   // Used by MarkSweep::mark_sweep_phase4()

   HeapWord*       q = space()->bottom();

   HeapWord* const t = _end_of_live;

   debug_only(HeapWord* prev_q = NULL);

   if (q < t && _first_dead > q &&

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

 #ifdef ASSERT

     // we have a chunk of the space which hasn't moved and we've reinitialized the

     // mark word during the previous pass, so we can't use is_gc_marked for the

     // traversal.

     HeapWord* const end = _first_dead;

     while (q < end) {

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

       assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");

       debug_only(prev_q = q);

       q += size;

     }

 #endif

     if (_first_dead == t) {

       q = t;

     } else {

       // $$$ Funky

       q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer();

     }

   }

   const intx scan_interval = PrefetchScanIntervalInBytes;

   const intx copy_interval = PrefetchCopyIntervalInBytes;

   while (q < t) {

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

       // mark is pointer to next marked oop

       debug_only(prev_q = q);

       q = (HeapWord*) oop(q)->mark()->decode_pointer();

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

     } else {

       // prefetch beyond q

       Prefetch::read(q, scan_interval);

       // size and destination

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

       HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();

       // prefetch beyond compaction_top

       Prefetch::write(compaction_top, copy_interval);

       // copy object and reinit its mark

       assert(q != compaction_top, "everything in this pass should be moving");

       Copy::aligned_conjoint_words(q, compaction_top, size);

       oop(compaction_top)->init_mark();

       assert(oop(compaction_top)->klass() != NULL, "should have a class");

       debug_only(prev_q = q);

       q += size;

     }

   }

   assert(compaction_top() >= space()->bottom() && compaction_top() <= space()->end(),

          "should point inside space");

   space()->set_top(compaction_top());

   if (mangle_free_space) {

     space()->mangle_unused_area();

   }

 }