1 /*

     2  * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.

     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.

     8  *

     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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    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

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "gc/g1/dirtyCardQueue.hpp"

    27 #include "gc/g1/g1CollectedHeap.inline.hpp"

    28 #include "gc/g1/g1CollectorState.hpp"

    29 #include "gc/g1/g1ConcurrentMark.inline.hpp"

    30 #include "gc/g1/g1EvacFailure.hpp"

    31 #include "gc/g1/g1HeapVerifier.hpp"

    32 #include "gc/g1/g1OopClosures.inline.hpp"

    33 #include "gc/g1/g1_globals.hpp"

    34 #include "gc/g1/heapRegion.hpp"

    35 #include "gc/g1/heapRegionRemSet.hpp"

    36 #include "gc/shared/preservedMarks.inline.hpp"

    37 

    38 class UpdateRSetDeferred : public ExtendedOopClosure {

    39 private:

    40   G1CollectedHeap* _g1;

    41   DirtyCardQueue *_dcq;

    42   G1SATBCardTableModRefBS* _ct_bs;

    43 

    44 public:

    45   UpdateRSetDeferred(DirtyCardQueue* dcq) :

    46     _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}

    47 

    48   virtual void do_oop(narrowOop* p) { do_oop_work(p); }

    49   virtual void do_oop(      oop* p) { do_oop_work(p); }

    50   template <class T> void do_oop_work(T* p) {

    51     assert(_g1->heap_region_containing(p)->is_in_reserved(p), "paranoia");

    52     assert(!_g1->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region");

    53 

    54     T const o = oopDesc::load_heap_oop(p);

    55     if (oopDesc::is_null(o)) {

    56       return;

    57     }

    58 

    59     if (HeapRegion::is_in_same_region(p, oopDesc::decode_heap_oop(o))) {

    60       return;

    61     }

    62     size_t card_index = _ct_bs->index_for(p);

    63     if (_ct_bs->mark_card_deferred(card_index)) {

    64       _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));

    65     }

    66   }

    67 };

    68 

    69 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {

    70 private:

    71   G1CollectedHeap* _g1;

    72   G1ConcurrentMark* _cm;

    73   HeapRegion* _hr;

    74   size_t _marked_bytes;

    75   UpdateRSetDeferred* _update_rset_cl;

    76   bool _during_initial_mark;

    77   uint _worker_id;

    78   HeapWord* _last_forwarded_object_end;

    79 

    80 public:

    81   RemoveSelfForwardPtrObjClosure(HeapRegion* hr,

    82                                  UpdateRSetDeferred* update_rset_cl,

    83                                  bool during_initial_mark,

    84                                  uint worker_id) :

    85     _g1(G1CollectedHeap::heap()),

    86     _cm(_g1->concurrent_mark()),

    87     _hr(hr),

    88     _marked_bytes(0),

    89     _update_rset_cl(update_rset_cl),

    90     _during_initial_mark(during_initial_mark),

    91     _worker_id(worker_id),

    92     _last_forwarded_object_end(hr->bottom()) { }

    93 

    94   size_t marked_bytes() { return _marked_bytes; }

    95 

    96   // Iterate over the live objects in the region to find self-forwarded objects

    97   // that need to be kept live. We need to update the remembered sets of these

    98   // objects. Further update the BOT and marks.

    99   // We can coalesce and overwrite the remaining heap contents with dummy objects

   100   // as they have either been dead or evacuated (which are unreferenced now, i.e.

   101   // dead too) already.

   102   void do_object(oop obj) {

   103     HeapWord* obj_addr = (HeapWord*) obj;

   104     assert(_hr->is_in(obj_addr), "sanity");

   105 

   106     if (obj->is_forwarded() && obj->forwardee() == obj) {

   107       // The object failed to move.

   108 

   109       zap_dead_objects(_last_forwarded_object_end, obj_addr);

   110       // We consider all objects that we find self-forwarded to be

   111       // live. What we'll do is that we'll update the prev marking

   112       // info so that they are all under PTAMS and explicitly marked.

   113       if (!_cm->isPrevMarked(obj)) {

   114         _cm->markPrev(obj);

   115       }

   116       if (_during_initial_mark) {

   117         // For the next marking info we'll only mark the

   118         // self-forwarded objects explicitly if we are during

   119         // initial-mark (since, normally, we only mark objects pointed

   120         // to by roots if we succeed in copying them). By marking all

   121         // self-forwarded objects we ensure that we mark any that are

   122         // still pointed to be roots. During concurrent marking, and

   123         // after initial-mark, we don't need to mark any objects

   124         // explicitly and all objects in the CSet are considered

   125         // (implicitly) live. So, we won't mark them explicitly and

   126         // we'll leave them over NTAMS.

   127         _cm->mark_in_next_bitmap(_hr, obj);

   128       }

   129       size_t obj_size = obj->size();

   130 

   131       _marked_bytes += (obj_size * HeapWordSize);

   132       PreservedMarks::init_forwarded_mark(obj);

   133 

   134       // While we were processing RSet buffers during the collection,

   135       // we actually didn't scan any cards on the collection set,

   136       // since we didn't want to update remembered sets with entries

   137       // that point into the collection set, given that live objects

   138       // from the collection set are about to move and such entries

   139       // will be stale very soon.

   140       // This change also dealt with a reliability issue which

   141       // involved scanning a card in the collection set and coming

   142       // across an array that was being chunked and looking malformed.

   143       // The problem is that, if evacuation fails, we might have

   144       // remembered set entries missing given that we skipped cards on

   145       // the collection set. So, we'll recreate such entries now.

   146       obj->oop_iterate(_update_rset_cl);

   147 

   148       HeapWord* obj_end = obj_addr + obj_size;

   149       _last_forwarded_object_end = obj_end;

   150       _hr->cross_threshold(obj_addr, obj_end);

   151     }

   152   }

   153 

   154   // Fill the memory area from start to end with filler objects, and update the BOT

   155   // and the mark bitmap accordingly.

   156   void zap_dead_objects(HeapWord* start, HeapWord* end) {

   157     if (start == end) {

   158       return;

   159     }

   160 

   161     size_t gap_size = pointer_delta(end, start);

   162     MemRegion mr(start, gap_size);

   163     if (gap_size >= CollectedHeap::min_fill_size()) {

   164       CollectedHeap::fill_with_objects(start, gap_size);

   165 

   166       HeapWord* end_first_obj = start + ((oop)start)->size();

   167       _hr->cross_threshold(start, end_first_obj);

   168       // Fill_with_objects() may have created multiple (i.e. two)

   169       // objects, as the max_fill_size() is half a region.

   170       // After updating the BOT for the first object, also update the

   171       // BOT for the second object to make the BOT complete.

   172       if (end_first_obj != end) {

   173         _hr->cross_threshold(end_first_obj, end);

   174 #ifdef ASSERT

   175         size_t size_second_obj = ((oop)end_first_obj)->size();

   176         HeapWord* end_of_second_obj = end_first_obj + size_second_obj;

   177         assert(end == end_of_second_obj,

   178                "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", "

   179                "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT,

   180                p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj));

   181 #endif

   182       }

   183     }

   184     _cm->clearRangePrevBitmap(mr);

   185   }

   186 

   187   void zap_remainder() {

   188     zap_dead_objects(_last_forwarded_object_end, _hr->top());

   189   }

   190 };

   191 

   192 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {

   193   G1CollectedHeap* _g1h;

   194   uint _worker_id;

   195   HeapRegionClaimer* _hrclaimer;

   196 

   197   DirtyCardQueue _dcq;

   198   UpdateRSetDeferred _update_rset_cl;

   199 

   200 public:

   201   RemoveSelfForwardPtrHRClosure(uint worker_id,

   202                                 HeapRegionClaimer* hrclaimer) :

   203     _g1h(G1CollectedHeap::heap()),

   204     _dcq(&_g1h->dirty_card_queue_set()),

   205     _update_rset_cl(&_dcq),

   206     _worker_id(worker_id),

   207     _hrclaimer(hrclaimer) {

   208   }

   209 

   210   size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr,

   211                                                bool during_initial_mark) {

   212     RemoveSelfForwardPtrObjClosure rspc(hr,

   213                                         &_update_rset_cl,

   214                                         during_initial_mark,

   215                                         _worker_id);

   216     hr->object_iterate(&rspc);

   217     // Need to zap the remainder area of the processed region.

   218     rspc.zap_remainder();

   219 

   220     return rspc.marked_bytes();

   221   }

   222 

   223   bool doHeapRegion(HeapRegion *hr) {

   224     assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index());

   225     assert(hr->in_collection_set(), "bad CS");

   226 

   227     if (_hrclaimer->claim_region(hr->hrm_index())) {

   228       if (hr->evacuation_failed()) {

   229         bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause();

   230         bool during_conc_mark = _g1h->collector_state()->mark_in_progress();

   231 

   232         hr->note_self_forwarding_removal_start(during_initial_mark,

   233                                                during_conc_mark);

   234         _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr);

   235 

   236         hr->reset_bot();

   237 

   238         size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark);

   239 

   240         hr->rem_set()->clean_strong_code_roots(hr);

   241 

   242         hr->note_self_forwarding_removal_end(live_bytes);

   243       }

   244     }

   245     return false;

   246   }

   247 };

   248 

   249 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() :

   250   AbstractGangTask("G1 Remove Self-forwarding Pointers"),

   251   _g1h(G1CollectedHeap::heap()),

   252   _hrclaimer(_g1h->workers()->active_workers()) { }

   253 

   254 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) {

   255   RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer);

   256 

   257   _g1h->collection_set_iterate_from(&rsfp_cl, worker_id);

   258 }