1 /* 2 * Copyright (c) 2012, 2015, 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/concurrentMark.inline.hpp" 27 #include "gc/g1/dirtyCardQueue.hpp" 28 #include "gc/g1/g1CollectedHeap.inline.hpp" 29 #include "gc/g1/g1CollectorState.hpp" 30 #include "gc/g1/g1EvacFailure.hpp" 31 #include "gc/g1/g1OopClosures.inline.hpp" 32 #include "gc/g1/g1_globals.hpp" 33 #include "gc/g1/heapRegion.hpp" 34 #include "gc/g1/heapRegionRemSet.hpp" 35 36 class UpdateRSetDeferred : public OopsInHeapRegionClosure { 37 private: 38 G1CollectedHeap* _g1; 39 DirtyCardQueue *_dcq; 40 G1SATBCardTableModRefBS* _ct_bs; 41 42 public: 43 UpdateRSetDeferred(DirtyCardQueue* dcq) : 44 _g1(G1CollectedHeap::heap()), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {} 45 46 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 47 virtual void do_oop( oop* p) { do_oop_work(p); } 48 template <class T> void do_oop_work(T* p) { 49 assert(_from->is_in_reserved(p), "paranoia"); 50 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && 51 !_from->is_survivor()) { 52 size_t card_index = _ct_bs->index_for(p); 53 if (_ct_bs->mark_card_deferred(card_index)) { 54 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index)); 55 } 56 } 57 } 58 }; 59 60 class RemoveSelfForwardPtrObjClosure: public ObjectClosure { 61 private: 62 G1CollectedHeap* _g1; 63 ConcurrentMark* _cm; 64 HeapRegion* _hr; 65 size_t _marked_bytes; 66 OopsInHeapRegionClosure *_update_rset_cl; 67 bool _during_initial_mark; 68 uint _worker_id; 69 HeapWord* _last_forwarded_object_end; 70 71 public: 72 RemoveSelfForwardPtrObjClosure(HeapRegion* hr, 73 OopsInHeapRegionClosure* update_rset_cl, 74 bool during_initial_mark, 75 uint worker_id) : 76 _g1(G1CollectedHeap::heap()), 77 _cm(_g1->concurrent_mark()), 78 _hr(hr), 79 _marked_bytes(0), 80 _update_rset_cl(update_rset_cl), 81 _during_initial_mark(during_initial_mark), 82 _worker_id(worker_id), 83 _last_forwarded_object_end(hr->bottom()) { } 84 85 size_t marked_bytes() { return _marked_bytes; } 86 87 // Iterate over the live objects in the region to find self-forwarded objects 88 // that need to be kept live. We need to update the remembered sets of these 89 // objects. Further update the BOT and marks. 90 // We can coalesce and overwrite the remaining heap contents with dummy objects 91 // as they have either been dead or evacuated (which are unreferenced now, i.e. 92 // dead too) already. 93 void do_object(oop obj) { 94 HeapWord* obj_addr = (HeapWord*) obj; 95 assert(_hr->is_in(obj_addr), "sanity"); 96 size_t obj_size = obj->size(); 97 HeapWord* obj_end = obj_addr + obj_size; 98 99 if (obj->is_forwarded() && obj->forwardee() == obj) { 100 // The object failed to move. 101 102 zap_dead_objects(_last_forwarded_object_end, obj_addr); 103 // We consider all objects that we find self-forwarded to be 104 // live. What we'll do is that we'll update the prev marking 105 // info so that they are all under PTAMS and explicitly marked. 106 if (!_cm->isPrevMarked(obj)) { 107 _cm->markPrev(obj); 108 } 109 if (_during_initial_mark) { 110 // For the next marking info we'll only mark the 111 // self-forwarded objects explicitly if we are during 112 // initial-mark (since, normally, we only mark objects pointed 113 // to by roots if we succeed in copying them). By marking all 114 // self-forwarded objects we ensure that we mark any that are 115 // still pointed to be roots. During concurrent marking, and 116 // after initial-mark, we don't need to mark any objects 117 // explicitly and all objects in the CSet are considered 118 // (implicitly) live. So, we won't mark them explicitly and 119 // we'll leave them over NTAMS. 120 _cm->grayRoot(obj, obj_size, _worker_id, _hr); 121 } 122 _marked_bytes += (obj_size * HeapWordSize); 123 obj->set_mark(markOopDesc::prototype()); 124 125 // While we were processing RSet buffers during the collection, 126 // we actually didn't scan any cards on the collection set, 127 // since we didn't want to update remembered sets with entries 128 // that point into the collection set, given that live objects 129 // from the collection set are about to move and such entries 130 // will be stale very soon. 131 // This change also dealt with a reliability issue which 132 // involved scanning a card in the collection set and coming 133 // across an array that was being chunked and looking malformed. 134 // The problem is that, if evacuation fails, we might have 135 // remembered set entries missing given that we skipped cards on 136 // the collection set. So, we'll recreate such entries now. 137 obj->oop_iterate(_update_rset_cl); 138 139 _last_forwarded_object_end = obj_end; 140 _hr->cross_threshold(obj_addr, obj_end); 141 } 142 } 143 144 // Fill the memory area from start to end with filler objects, and update the BOT 145 // and the mark bitmap accordingly. 146 void zap_dead_objects(HeapWord* start, HeapWord* end) { 147 if (start == end) { 148 return; 149 } 150 151 size_t gap_size = pointer_delta(end, start); 152 MemRegion mr(start, gap_size); 153 if (gap_size >= CollectedHeap::min_fill_size()) { 154 CollectedHeap::fill_with_objects(start, gap_size); 155 156 HeapWord* end_first_obj = start + ((oop)start)->size(); 157 _hr->cross_threshold(start, end_first_obj); 158 // Fill_with_objects() may have created multiple (i.e. two) 159 // objects, as the max_fill_size() is half a region. 160 // After updating the BOT for the first object, also update the 161 // BOT for the second object to make the BOT complete. 162 if (end_first_obj != end) { 163 _hr->cross_threshold(end_first_obj, end); 164 #ifdef ASSERT 165 size_t size_second_obj = ((oop)end_first_obj)->size(); 166 HeapWord* end_of_second_obj = end_first_obj + size_second_obj; 167 assert(end == end_of_second_obj, 168 "More than two objects were used to fill the area from " PTR_FORMAT " to " PTR_FORMAT ", " 169 "second objects size " SIZE_FORMAT " ends at " PTR_FORMAT, 170 p2i(start), p2i(end), size_second_obj, p2i(end_of_second_obj)); 171 #endif 172 } 173 } 174 _cm->clearRangePrevBitmap(mr); 175 } 176 177 void zap_remainder() { 178 zap_dead_objects(_last_forwarded_object_end, _hr->top()); 179 } 180 }; 181 182 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure { 183 G1CollectedHeap* _g1h; 184 uint _worker_id; 185 HeapRegionClaimer* _hrclaimer; 186 187 DirtyCardQueue _dcq; 188 UpdateRSetDeferred _update_rset_cl; 189 190 public: 191 RemoveSelfForwardPtrHRClosure(uint worker_id, 192 HeapRegionClaimer* hrclaimer) : 193 _g1h(G1CollectedHeap::heap()), 194 _dcq(&_g1h->dirty_card_queue_set()), 195 _update_rset_cl(&_dcq), 196 _worker_id(worker_id), 197 _hrclaimer(hrclaimer) { 198 } 199 200 size_t remove_self_forward_ptr_by_walking_hr(HeapRegion* hr, 201 bool during_initial_mark) { 202 RemoveSelfForwardPtrObjClosure rspc(hr, 203 &_update_rset_cl, 204 during_initial_mark, 205 _worker_id); 206 _update_rset_cl.set_region(hr); 207 hr->object_iterate(&rspc); 208 // Need to zap the remainder area of the processed region. 209 rspc.zap_remainder(); 210 211 return rspc.marked_bytes(); 212 } 213 214 bool doHeapRegion(HeapRegion *hr) { 215 bool during_initial_mark = _g1h->collector_state()->during_initial_mark_pause(); 216 bool during_conc_mark = _g1h->collector_state()->mark_in_progress(); 217 218 assert(!hr->is_pinned(), "Unexpected pinned region at index %u", hr->hrm_index()); 219 assert(hr->in_collection_set(), "bad CS"); 220 221 if (_hrclaimer->claim_region(hr->hrm_index())) { 222 if (hr->evacuation_failed()) { 223 hr->note_self_forwarding_removal_start(during_initial_mark, 224 during_conc_mark); 225 _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr); 226 227 // In the common case (i.e. when there is no evacuation 228 // failure) we make sure that the following is done when 229 // the region is freed so that it is "ready-to-go" when it's 230 // re-allocated. However, when evacuation failure happens, a 231 // region will remain in the heap and might ultimately be added 232 // to a CSet in the future. So we have to be careful here and 233 // make sure the region's RSet is ready for parallel iteration 234 // whenever this might be required in the future. 235 hr->rem_set()->reset_for_par_iteration(); 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(during_initial_mark, 243 during_conc_mark, 244 live_bytes); 245 } 246 } 247 return false; 248 } 249 }; 250 251 G1ParRemoveSelfForwardPtrsTask::G1ParRemoveSelfForwardPtrsTask() : 252 AbstractGangTask("G1 Remove Self-forwarding Pointers"), 253 _g1h(G1CollectedHeap::heap()), 254 _hrclaimer(_g1h->workers()->active_workers()) { } 255 256 void G1ParRemoveSelfForwardPtrsTask::work(uint worker_id) { 257 RemoveSelfForwardPtrHRClosure rsfp_cl(worker_id, &_hrclaimer); 258 259 HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id); 260 _g1h->collection_set_iterate_from(hr, &rsfp_cl); 261 }