jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp@d06a2d7fcd5b (annotated)

src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp@d06a2d7fcd5b (annotated)

src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp

Mon, 21 Nov 2011 07:47:34 +0100

author: brutisso
date: Mon, 21 Nov 2011 07:47:34 +0100
changeset 3290: d06a2d7fcd5b
parent 2314: f95d63e2154a
child 4037: da91efe96a93
permissions: -rw-r--r--

7110718: -XX:MarkSweepAlwaysCompactCount=0 crashes the JVM
Summary: Interpret MarkSweepAlwaysCompactCount < 1 as never do full compaction
Reviewed-by: ysr, tonyp, jmasa, johnc

 /*
  * Copyright (c) 2001, 2011, 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::set_destination_decorator_perm_gen() {
   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   _destination_decorator = heap->perm_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");
   guarantee(_destination_decorator != heap->perm_gen()->object_mark_sweep(), "Cannot advance perm gen decorator");
   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 = (MarkSweepAlwaysCompactCount < 1)
     || ((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);
       }
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(oop(q), size));
       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);
           }
           VALIDATE_MARK_SWEEP_ONLY(MarkSweep::register_live_oop(oop(q), sz));
           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) {
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));
       // point all the oops to the new location
       size_t size = oop(q)->adjust_pointers();
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));
       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
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::track_interior_pointers(oop(q)));
       // point all the oops to the new location
       size_t size = oop(q)->adjust_pointers();
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::check_interior_pointers());
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::validate_live_oop(oop(q), size));
       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)");
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, q));
       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
       VALIDATE_MARK_SWEEP_ONLY(MarkSweep::live_oop_moved_to(q, size, compaction_top));
       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();
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp@d06a2d7fcd5b (annotated)

src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp