1 /* 2 * Copyright (c) 2012, 2018, 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 #include "oops/access.inline.hpp" 38 #include "oops/compressedOops.inline.hpp" 39 40 class UpdateRSetDeferred : public ExtendedOopClosure { 41 private: 42 G1CollectedHeap* _g1; 43 DirtyCardQueue* _dcq; 44 G1CardTable* _ct; 45 46 public: 47 UpdateRSetDeferred(DirtyCardQueue* dcq) : 48 _g1(G1CollectedHeap::heap()), _ct(_g1->card_table()), _dcq(dcq) {} 49 50 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 51 virtual void do_oop( oop* p) { do_oop_work(p); } 52 template <class T> void do_oop_work(T* p) { 53 assert(_g1->heap_region_containing(p)->is_in_reserved(p), "paranoia"); 54 assert(!_g1->heap_region_containing(p)->is_survivor(), "Unexpected evac failure in survivor region"); 55 56 T const o = RawAccess<>::oop_load(p); 57 if (CompressedOops::is_null(o)) { 58 return; 59 } 60 61 if (HeapRegion::is_in_same_region(p, CompressedOops::decode(o))) { 62 return; 63 } 64 size_t card_index = _ct->index_for(p); 65 if (_ct->mark_card_deferred(card_index)) { 66 _dcq->enqueue((jbyte*)_ct->byte_for_index(card_index)); 67 } 68 } 69 }; 70 71 class RemoveSelfForwardPtrObjClosure: public ObjectClosure { 72 private: 73 G1CollectedHeap* _g1; 74 G1ConcurrentMark* _cm; 75 HeapRegion* _hr; 76 size_t _marked_bytes; 77 UpdateRSetDeferred* _update_rset_cl; 78 bool _during_initial_mark; 79 uint _worker_id; 80 HeapWord* _last_forwarded_object_end; 81 82 public: 83 RemoveSelfForwardPtrObjClosure(HeapRegion* hr, 84 UpdateRSetDeferred* update_rset_cl, 85 bool during_initial_mark, 86 uint worker_id) : 87 _g1(G1CollectedHeap::heap()), 88 _cm(_g1->concurrent_mark()), 89 _hr(hr), 90 _marked_bytes(0), 91 _update_rset_cl(update_rset_cl), 92 _during_initial_mark(during_initial_mark), 93 _worker_id(worker_id), 94 _last_forwarded_object_end(hr->bottom()) { } 95 96 size_t marked_bytes() { return _marked_bytes; } 97 98 // Iterate over the live objects in the region to find self-forwarded objects 99 // that need to be kept live. We need to update the remembered sets of these 100 // objects. Further update the BOT and marks. 101 // We can coalesce and overwrite the remaining heap contents with dummy objects 102 // as they have either been dead or evacuated (which are unreferenced now, i.e. 103 // dead too) already. 104 void do_object(oop obj) { 105 HeapWord* obj_addr = (HeapWord*) obj; 106 assert(_hr->is_in(obj_addr), "sanity"); 107 108 if (obj->is_forwarded() && obj->forwardee() == obj) { 109 // The object failed to move. 110 111 zap_dead_objects(_last_forwarded_object_end, obj_addr); 112 // We consider all objects that we find self-forwarded to be 113 // live. What we'll do is that we'll update the prev marking 114 // info so that they are all under PTAMS and explicitly marked. 115 if (!_cm->is_marked_in_prev_bitmap(obj)) { 116 _cm->mark_in_prev_bitmap(obj); 117 } 118 if (_during_initial_mark) { 119 // For the next marking info we'll only mark the 120 // self-forwarded objects explicitly if we are during 121 // initial-mark (since, normally, we only mark objects pointed 122 // to by roots if we succeed in copying them). By marking all 123 // self-forwarded objects we ensure that we mark any that are 124 // still pointed to be roots. During concurrent marking, and 125 // after initial-mark, we don't need to mark any objects 126 // explicitly and all objects in the CSet are considered 127 // (implicitly) live. So, we won't mark them explicitly and 128 // we'll leave them over NTAMS. 129 _cm->mark_in_next_bitmap(_worker_id, obj); 130 } 131 size_t obj_size = obj->size(); 132 133 _marked_bytes += (obj_size * HeapWordSize); 134 PreservedMarks::init_forwarded_mark(obj); 135 136 // While we were processing RSet buffers during the collection, 137 // we actually didn't scan any cards on the collection set, 138 // since we didn't want to update remembered sets with entries 139 // that point into the collection set, given that live objects 140 // from the collection set are about to move and such entries 141 // will be stale very soon. 142 // This change also dealt with a reliability issue which 143 // involved scanning a card in the collection set and coming 144 // across an array that was being chunked and looking malformed. 145 // The problem is that, if evacuation fails, we might have 146 // remembered set entries missing given that we skipped cards on 147 // the collection set. So, we'll recreate such entries now. 148 obj->oop_iterate(_update_rset_cl); 149 150 HeapWord* obj_end = obj_addr + obj_size; 151 _last_forwarded_object_end = obj_end; 152 _hr->cross_threshold(obj_addr, obj_end); 153 } 154 } 155 156 // Fill the memory area from start to end with filler objects, and update the BOT 157 // and the mark bitmap accordingly. 158 void zap_dead_objects(HeapWord* start, HeapWord* end) { 159 if (start == end) { 160 return; 161 } 162 163 size_t gap_size = pointer_delta(end, start); 164 MemRegion mr(start, gap_size); 165 if (gap_size >= CollectedHeap::min_fill_size()) { 166 CollectedHeap::fill_with_objects(start, gap_size); 167 168 HeapWord* end_first_obj = start + ((oop)start)->size(); 169 _hr->cross_threshold(start, end_first_obj); 170 // Fill_with_objects() may have created multiple (i.e. two) 171 // objects, as the max_fill_size() is half a region. 172 // After updating the BOT for the first object, also update the 173 // BOT for the second object to make the BOT complete. 174 if (end_first_obj != end) { 175 _hr->cross_threshold(end_first_obj, end); 176 #ifdef ASSERT 177 size_t size_second_obj = ((oop)end_first_obj)->size(); 178 HeapWord* end_of_second_obj = end_first_obj + size_second_obj; 179 assert(end == end_of_second_obj, 180 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", " 181 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT, 182 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj)); 183 #endif 184 } 185 } 186 _cm->clear_range_in_prev_bitmap(mr); 187 } 188 189 void zap_remainder() { 190 zap_dead_objects(_last_forwarded_object_end, _hr->top()); 191 } 192 }; 193 194 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure { 195 G1CollectedHeap* _g1h; 196 uint _worker_id; 197 HeapRegionClaimer* _hrclaimer; 198 199 DirtyCardQueue _dcq; 200 UpdateRSetDeferred _update_rset_cl; 201 202 public: 203 RemoveSelfForwardPtrHRClosure(uint worker_id, 204 HeapRegionClaimer* hrclaimer) : 205 _g1h(G1CollectedHeap::heap()), 206 _dcq(&_g1h->dirty_card_queue_set()), 207 _update_rset_cl(&_dcq), 208 _worker_id(worker_id), 209 _hrclaimer(hrclaimer) { 210 } 211 212 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr, 213 bool during_initial_mark) { 214 RemoveSelfForwardPtrObjClosure rspc(hr, 215 &_update_rset_cl, 216 during_initial_mark, 217 _worker_id); 218 hr->object_iterate(&rspc); 219 // Need to zap the remainder area of the processed region. 220 rspc.zap_remainder(); 221 222 return rspc.marked_bytes(); 223 } 224 225 bool do_heap_region(HeapRegion *hr) { 226 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index()); 227 assert(hr->in_collection_set(), "bad CS"); 228 229 if (_hrclaimer->claim_region(hr->hrm_index())) { 230 if (hr->evacuation_failed()) { 231 bool during_initial_mark = _g1h->collector_state()->in_initial_mark_gc(); 232 bool during_conc_mark = _g1h->collector_state()->mark_or_rebuild_in_progress(); 233 234 hr->note_self_forwarding_removal_start(during_initial_mark, 235 during_conc_mark); 236 _g1h->verifier()->check_bitmaps("Self-Forwarding Ptr Removal", hr); 237 238 hr->reset_bot(); 239 240 size_t live_bytes = remove_self_forward_ptr_by_walking_hr(hr, during_initial_mark); 241 242 hr->rem_set()->clean_strong_code_roots(hr); 243 hr->rem_set()->clear_locked(true); 244 245 hr->note_self_forwarding_removal_end(live_bytes); 246 } 247 } 248 return false; 249 } 250 }; 251 252 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() : 253 AbstractGangTask("G1 Remove Self-forwarding Pointers"), 254 _g1h(G1CollectedHeap::heap()), 255 _hrclaimer(_g1h->workers()->active_workers()) { } 256 257 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) { 258 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer); 259 260 _g1h->collection_set_iterate_from(&rsfp_cl, worker_id); 261 }