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 OopsInHeapRegionClosure { 39 private: 40 G1CollectedHeap* _g1; 41 DirtyCardQueue *_dcq; 42 G1CardTable* _ct; 43 44 public: 45 UpdateRSetDeferred(DirtyCardQueue* dcq) : 46 _g1(G1CollectedHeap::heap()), _ct(_g1->g1_card_table()), _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(_from->is_in_reserved(p), "paranoia"); 52 assert(!_from->is_survivor(), "Unexpected evac failure in survivor region"); 53 54 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p))) { 55 size_t card_index = _ct->index_for(p); 56 if (_ct->mark_card_deferred(card_index)) { 57 _dcq->enqueue((jbyte*)_ct->byte_for_index(card_index)); 58 } 59 } 60 } 61 }; 62 63 class RemoveSelfForwardPtrObjClosure: public ObjectClosure { 64 private: 65 G1CollectedHeap* _g1; 66 G1ConcurrentMark* _cm; 67 HeapRegion* _hr; 68 size_t _marked_bytes; 69 OopsInHeapRegionClosure *_update_rset_cl; 70 bool _during_initial_mark; 71 uint _worker_id; 72 HeapWord* _last_forwarded_object_end; 73 74 public: 75 RemoveSelfForwardPtrObjClosure(HeapRegion* hr, 76 OopsInHeapRegionClosure* update_rset_cl, 77 bool during_initial_mark, 78 uint worker_id) : 79 _g1(G1CollectedHeap::heap()), 80 _cm(_g1->concurrent_mark()), 81 _hr(hr), 82 _marked_bytes(0), 83 _update_rset_cl(update_rset_cl), 84 _during_initial_mark(during_initial_mark), 85 _worker_id(worker_id), 86 _last_forwarded_object_end(hr->bottom()) { } 87 88 size_t marked_bytes() { return _marked_bytes; } 89 90 // Iterate over the live objects in the region to find self-forwarded objects 91 // that need to be kept live. We need to update the remembered sets of these 92 // objects. Further update the BOT and marks. 93 // We can coalesce and overwrite the remaining heap contents with dummy objects 94 // as they have either been dead or evacuated (which are unreferenced now, i.e. 95 // dead too) already. 96 void do_object(oop obj) { 97 HeapWord* obj_addr = (HeapWord*) obj; 98 assert(_hr->is_in(obj_addr), "sanity"); 99 100 if (obj->is_forwarded() && obj->forwardee() == obj) { 101 // The object failed to move. 102 103 zap_dead_objects(_last_forwarded_object_end, obj_addr); 104 // We consider all objects that we find self-forwarded to be 105 // live. What we'll do is that we'll update the prev marking 106 // info so that they are all under PTAMS and explicitly marked. 107 if (!_cm->isPrevMarked(obj)) { 108 _cm->markPrev(obj); 109 } 110 if (_during_initial_mark) { 111 // For the next marking info we'll only mark the 112 // self-forwarded objects explicitly if we are during 113 // initial-mark (since, normally, we only mark objects pointed 114 // to by roots if we succeed in copying them). By marking all 115 // self-forwarded objects we ensure that we mark any that are 116 // still pointed to be roots. During concurrent marking, and 117 // after initial-mark, we don't need to mark any objects 118 // explicitly and all objects in the CSet are considered 119 // (implicitly) live. So, we won't mark them explicitly and 120 // we'll leave them over NTAMS. 121 _cm->grayRoot(obj, _hr); 122 } 123 size_t obj_size = obj->size(); 124 125 _marked_bytes += (obj_size * HeapWordSize); 126 PreservedMarks::init_forwarded_mark(obj); 127 128 // While we were processing RSet buffers during the collection, 129 // we actually didn't scan any cards on the collection set, 130 // since we didn't want to update remembered sets with entries 131 // that point into the collection set, given that live objects 132 // from the collection set are about to move and such entries 133 // will be stale very soon. 134 // This change also dealt with a reliability issue which 135 // involved scanning a card in the collection set and coming 136 // across an array that was being chunked and looking malformed. 137 // The problem is that, if evacuation fails, we might have 138 // remembered set entries missing given that we skipped cards on 139 // the collection set. So, we'll recreate such entries now. 140 obj->oop_iterate(_update_rset_cl); 141 142 HeapWord* obj_end = obj_addr + obj_size; 143 _last_forwarded_object_end = obj_end; 144 _hr->cross_threshold(obj_addr, obj_end); 145 } 146 } 147 148 // Fill the memory area from start to end with filler objects, and update the BOT 149 // and the mark bitmap accordingly. 150 void zap_dead_objects(HeapWord* start, HeapWord* end) { 151 if (start == end) { 152 return; 153 } 154 155 size_t gap_size = pointer_delta(end, start); 156 MemRegion mr(start, gap_size); 157 if (gap_size >= CollectedHeap::min_fill_size()) { 158 CollectedHeap::fill_with_objects(start, gap_size); 159 160 HeapWord* end_first_obj = start + ((oop)start)->size(); 161 _hr->cross_threshold(start, end_first_obj); 162 // Fill_with_objects() may have created multiple (i.e. two) 163 // objects, as the max_fill_size() is half a region. 164 // After updating the BOT for the first object, also update the 165 // BOT for the second object to make the BOT complete. 166 if (end_first_obj != end) { 167 _hr->cross_threshold(end_first_obj, end); 168 #ifdef ASSERT 169 size_t size_second_obj = ((oop)end_first_obj)->size(); 170 HeapWord* end_of_second_obj = end_first_obj + size_second_obj; 171 assert(end == end_of_second_obj, 172 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", " 173 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT, 174 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj)); 175 #endif 176 } 177 } 178 _cm->clearRangePrevBitmap(mr); 179 } 180 181 void zap_remainder() { 182 zap_dead_objects(_last_forwarded_object_end, _hr->top()); 183 } 184 }; 185 186 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure { 187 G1CollectedHeap* _g1h; 188 uint _worker_id; 189 HeapRegionClaimer* _hrclaimer; 190 191 DirtyCardQueue _dcq; 192 UpdateRSetDeferred _update_rset_cl; 193 194 public: 195 RemoveSelfForwardPtrHRClosure(uint worker_id, 196 HeapRegionClaimer* hrclaimer) : 197 _g1h(G1CollectedHeap::heap()), 198 _dcq(&_g1h->dirty_card_queue_set()), 199 _update_rset_cl(&_dcq), 200 _worker_id(worker_id), 201 _hrclaimer(hrclaimer) { 202 } 203 204 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr, 205 bool during_initial_mark) { 206 RemoveSelfForwardPtrObjClosure rspc(hr, 207 &_update_rset_cl, 208 during_initial_mark, 209 _worker_id); 210 _update_rset_cl.set_region(hr); 211 hr->object_iterate(&rspc); 212 // Need to zap the remainder area of the processed region. 213 rspc.zap_remainder(); 214 215 return rspc.marked_bytes(); 216 } 217 218 bool doHeapRegion(HeapRegion *hr) { 219 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index()); 220 assert(hr->in_collection_set(), "bad CS"); 221 222 if (_hrclaimer->claim_region(hr->hrm_index())) { 223 if (hr->evacuation_failed()) { 224 bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause(); 225 bool during_conc_mark = _g1h->collector_state()->mark_in_progress(); 226 227 hr->note_self_forwarding_removal_start(during_initial_mark, 228 during_conc_mark); 229 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr); 230 231 hr->reset_bot(); 232 233 size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark); 234 235 hr->rem_set()->clean_strong_code_roots(hr); 236 237 hr->note_self_forwarding_removal_end(live_bytes); 238 } 239 } 240 return false; 241 } 242 }; 243 244 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() : 245 AbstractGangTask("G1 Remove Self-forwarding Pointers"), 246 _g1h(G1CollectedHeap::heap()), 247 _hrclaimer(_g1h->workers()->active_workers()) { } 248 249 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) { 250 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer); 251 252 _g1h->collection_set_iterate_from(&rsfp_cl, worker_id); 253 }