1 /*
  2  * Copyright (c) 2017, 2022, 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/g1CollectedHeap.hpp"
 27 #include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
 28 #include "gc/g1/g1FullCollector.inline.hpp"
 29 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 30 #include "gc/g1/g1FullGCCompactTask.hpp"
 31 #include "gc/g1/heapRegion.inline.hpp"
 32 #include "gc/shared/gcTraceTime.inline.hpp"
 33 #include "logging/log.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "utilities/ticks.hpp"
 36 
 37 // Do work for all skip-compacting regions.
 38 class G1ResetSkipCompactingClosure : public HeapRegionClosure {
 39   G1FullCollector* _collector;
 40 
 41 public:
 42   G1ResetSkipCompactingClosure(G1FullCollector* collector) : _collector(collector) { }
 43 
 44   bool do_heap_region(HeapRegion* r) {
 45     uint region_index = r->hrm_index();
 46     // Only for skip-compaction regions; early return otherwise.
 47     if (!_collector->is_skip_compacting(region_index)) {
 48       return false;
 49     }
 50 #ifdef ASSERT
 51     if (r->is_humongous()) {
 52       oop obj = cast_to_oop(r->humongous_start_region()->bottom());
 53       assert(_collector->mark_bitmap()->is_marked(obj), "must be live");
 54     } else if (r->is_open_archive()) {
 55       bool is_empty = (_collector->live_words(r->hrm_index()) == 0);
 56       assert(!is_empty, "should contain at least one live obj");
 57     } else if (r->is_closed_archive()) {
 58       // should early-return above
 59       ShouldNotReachHere();
 60     } else {
 61       assert(_collector->live_words(region_index) > _collector->scope()->region_compaction_threshold(),
 62              "should be quite full");
 63     }
 64 #endif
 65     assert(_collector->compaction_top(r) == nullptr,
 66            "region %u compaction_top " PTR_FORMAT " must not be different from bottom " PTR_FORMAT,
 67            r->hrm_index(), p2i(_collector->compaction_top(r)), p2i(r->bottom()));
 68 
 69     r->reset_skip_compacting_after_full_gc();
 70     return false;
 71   }
 72 };
 73 
 74 void G1FullGCCompactTask::G1CompactRegionClosure::clear_in_bitmap(oop obj) {
 75   assert(_bitmap->is_marked(obj), "Should only compact marked objects");
 76   _bitmap->clear(obj);
 77 }
 78 
 79 size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
 80   size_t size = obj->size();
 81   if (obj->is_forwarded()) {
 82     HeapWord* destination = cast_from_oop<HeapWord*>(obj->forwardee());
 83 
 84     // copy object and reinit its mark
 85     HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
 86     assert(obj_addr != destination, "everything in this pass should be moving");
 87     Copy::aligned_conjoint_words(obj_addr, destination, size);
 88 
 89     // There is no need to transform stack chunks - marking already did that.
 90     cast_to_oop(destination)->init_mark();
 91     assert(cast_to_oop(destination)->klass() != NULL, "should have a class");
 92   }
 93 
 94   // Clear the mark for the compacted object to allow reuse of the
 95   // bitmap without an additional clearing step.
 96   clear_in_bitmap(obj);
 97   return size;
 98 }
 99 
100 void G1FullGCCompactTask::compact_region(HeapRegion* hr) {
101   assert(!hr->is_pinned(), "Should be no pinned region in compaction queue");
102   assert(!hr->is_humongous(), "Should be no humongous regions in compaction queue");
103 
104   if (!collector()->is_free(hr->hrm_index())) {
105     // The compaction closure not only copies the object to the new
106     // location, but also clears the bitmap for it. This is needed
107     // for bitmap verification and to be able to use the bitmap
108     // for evacuation failures in the next young collection. Testing
109     // showed that it was better overall to clear bit by bit, compared
110     // to clearing the whole region at the end. This difference was
111     // clearly seen for regions with few marks.
112     G1CompactRegionClosure compact(collector()->mark_bitmap());
113     hr->apply_to_marked_objects(collector()->mark_bitmap(), &compact);
114   }
115 
116   hr->reset_compacted_after_full_gc(_collector->compaction_top(hr));
117 }
118 
119 void G1FullGCCompactTask::work(uint worker_id) {
120   Ticks start = Ticks::now();
121   GrowableArray<HeapRegion*>* compaction_queue = collector()->compaction_point(worker_id)->regions();
122   for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
123        it != compaction_queue->end();
124        ++it) {
125     compact_region(*it);
126   }
127 
128   G1ResetSkipCompactingClosure hc(collector());
129   G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&hc, &_claimer, worker_id);
130   log_task("Compaction task", worker_id, start);
131 }
132 
133 void G1FullGCCompactTask::serial_compaction() {
134   GCTraceTime(Debug, gc, phases) tm("Phase 4: Serial Compaction", collector()->scope()->timer());
135   GrowableArray<HeapRegion*>* compaction_queue = collector()->serial_compaction_point()->regions();
136   for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
137        it != compaction_queue->end();
138        ++it) {
139     compact_region(*it);
140   }
141 }