src/share/vm/gc_implementation/g1/concurrentMark.inline.hpp

Thu, 22 Sep 2011 10:57:37 -0700

author
johnc
date
Thu, 22 Sep 2011 10:57:37 -0700
changeset 3175
4dfb2df418f2
parent 2973
23d434c6290d
child 3416
2ace1c4ee8da
permissions
-rw-r--r--

6484982: G1: process references during evacuation pauses
Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp

     1 /*
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     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.
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     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
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    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
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    22  *
    23  */
    25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_INLINE_HPP
    26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_INLINE_HPP
    28 #include "gc_implementation/g1/concurrentMark.hpp"
    29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
    31 inline void CMTask::push(oop obj) {
    32   HeapWord* objAddr = (HeapWord*) obj;
    33   assert(_g1h->is_in_g1_reserved(objAddr), "invariant");
    34   assert(!_g1h->is_on_master_free_list(
    35               _g1h->heap_region_containing((HeapWord*) objAddr)), "invariant");
    36   assert(!_g1h->is_obj_ill(obj), "invariant");
    37   assert(_nextMarkBitMap->isMarked(objAddr), "invariant");
    39   if (_cm->verbose_high()) {
    40     gclog_or_tty->print_cr("[%d] pushing "PTR_FORMAT, _task_id, (void*) obj);
    41   }
    43   if (!_task_queue->push(obj)) {
    44     // The local task queue looks full. We need to push some entries
    45     // to the global stack.
    47     if (_cm->verbose_medium()) {
    48       gclog_or_tty->print_cr("[%d] task queue overflow, "
    49                              "moving entries to the global stack",
    50                              _task_id);
    51     }
    52     move_entries_to_global_stack();
    54     // this should succeed since, even if we overflow the global
    55     // stack, we should have definitely removed some entries from the
    56     // local queue. So, there must be space on it.
    57     bool success = _task_queue->push(obj);
    58     assert(success, "invariant");
    59   }
    61   statsOnly( int tmp_size = _task_queue->size();
    62              if (tmp_size > _local_max_size) {
    63                _local_max_size = tmp_size;
    64              }
    65              ++_local_pushes );
    66 }
    68 // This determines whether the method below will check both the local
    69 // and global fingers when determining whether to push on the stack a
    70 // gray object (value 1) or whether it will only check the global one
    71 // (value 0). The tradeoffs are that the former will be a bit more
    72 // accurate and possibly push less on the stack, but it might also be
    73 // a little bit slower.
    75 #define _CHECK_BOTH_FINGERS_      1
    77 inline void CMTask::deal_with_reference(oop obj) {
    78   if (_cm->verbose_high()) {
    79     gclog_or_tty->print_cr("[%d] we're dealing with reference = "PTR_FORMAT,
    80                            _task_id, (void*) obj);
    81   }
    83   ++_refs_reached;
    85   HeapWord* objAddr = (HeapWord*) obj;
    86   assert(obj->is_oop_or_null(true /* ignore mark word */), "Error");
    87  if (_g1h->is_in_g1_reserved(objAddr)) {
    88     assert(obj != NULL, "null check is implicit");
    89     if (!_nextMarkBitMap->isMarked(objAddr)) {
    90       // Only get the containing region if the object is not marked on the
    91       // bitmap (otherwise, it's a waste of time since we won't do
    92       // anything with it).
    93       HeapRegion* hr = _g1h->heap_region_containing_raw(obj);
    94       if (!hr->obj_allocated_since_next_marking(obj)) {
    95         if (_cm->verbose_high()) {
    96           gclog_or_tty->print_cr("[%d] "PTR_FORMAT" is not considered marked",
    97                                  _task_id, (void*) obj);
    98         }
   100         // we need to mark it first
   101         if (_nextMarkBitMap->parMark(objAddr)) {
   102           // No OrderAccess:store_load() is needed. It is implicit in the
   103           // CAS done in parMark(objAddr) above
   104           HeapWord* global_finger = _cm->finger();
   106 #if _CHECK_BOTH_FINGERS_
   107           // we will check both the local and global fingers
   109           if (_finger != NULL && objAddr < _finger) {
   110             if (_cm->verbose_high()) {
   111               gclog_or_tty->print_cr("[%d] below the local finger ("PTR_FORMAT"), "
   112                                      "pushing it", _task_id, _finger);
   113             }
   114             push(obj);
   115           } else if (_curr_region != NULL && objAddr < _region_limit) {
   116             // do nothing
   117           } else if (objAddr < global_finger) {
   118             // Notice that the global finger might be moving forward
   119             // concurrently. This is not a problem. In the worst case, we
   120             // mark the object while it is above the global finger and, by
   121             // the time we read the global finger, it has moved forward
   122             // passed this object. In this case, the object will probably
   123             // be visited when a task is scanning the region and will also
   124             // be pushed on the stack. So, some duplicate work, but no
   125             // correctness problems.
   127             if (_cm->verbose_high()) {
   128               gclog_or_tty->print_cr("[%d] below the global finger "
   129                                      "("PTR_FORMAT"), pushing it",
   130                                      _task_id, global_finger);
   131             }
   132             push(obj);
   133           } else {
   134             // do nothing
   135           }
   136 #else // _CHECK_BOTH_FINGERS_
   137           // we will only check the global finger
   139           if (objAddr < global_finger) {
   140             // see long comment above
   142             if (_cm->verbose_high()) {
   143               gclog_or_tty->print_cr("[%d] below the global finger "
   144                                      "("PTR_FORMAT"), pushing it",
   145                                      _task_id, global_finger);
   146             }
   147             push(obj);
   148           }
   149 #endif // _CHECK_BOTH_FINGERS_
   150         }
   151       }
   152     }
   153   }
   154 }
   156 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_INLINE_HPP

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