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 38 class UpdateRSetDeferred : public ExtendedOopClosure { 39 private: 40 G1CollectedHeap* _g1; 41 DirtyCardQueue* _dcq; 42 G1CardTable* _ct; 43 44 public: 45 UpdateRSetDeferred(DirtyCardQueue* dcq) : 46 _g1(G1CollectedHeap::heap()), _ct(_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(_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->index_for(p); 63 if (_ct->mark_card_deferred(card_index)) { 64 _dcq->enqueue((jbyte*)_ct->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->is_marked_in_prev_bitmap(obj)) { 114 _cm->mark_in_prev_bitmap(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->clear_range_in_prev_bitmap(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 do_heap_region(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 }