1 /*
  2  * Copyright (c) 2017, 2021, 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.hpp"
 29 #include "gc/g1/g1FullCollector.inline.hpp"
 30 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 31 #include "gc/g1/g1FullGCCompactTask.hpp"
 32 #include "gc/g1/heapRegion.inline.hpp"
 33 #include "gc/shared/gcTraceTime.inline.hpp"
 34 #include "gc/shared/slidingForwarding.inline.hpp"
 35 #include "logging/log.hpp"
 36 #include "oops/oop.inline.hpp"
 37 #include "utilities/ticks.hpp"
 38 
 39 // Do work for all skip-compacting regions.
 40 class G1ResetSkipCompactingClosure : public HeapRegionClosure {
 41   G1FullCollector* _collector;
 42 
 43 public:
 44   G1ResetSkipCompactingClosure(G1FullCollector* collector) : _collector(collector) { }
 45 
 46   bool do_heap_region(HeapRegion* r) {
 47     uint region_index = r->hrm_index();
 48     // Only for skip-compaction regions; early return otherwise.
 49     if (!_collector->is_skip_compacting(region_index)) {
 50       return false;
 51     }
 52 #ifdef ASSERT
 53     if (r->is_humongous()) {
 54       oop obj = cast_to_oop(r->humongous_start_region()->bottom());
 55       assert(_collector->mark_bitmap()->is_marked(obj), "must be live");
 56     } else if (r->is_open_archive()) {
 57       bool is_empty = (_collector->live_words(r->hrm_index()) == 0);
 58       assert(!is_empty, "should contain at least one live obj");
 59     } else if (r->is_closed_archive()) {
 60       // should early-return above
 61       ShouldNotReachHere();
 62     } else {
 63       assert(_collector->live_words(region_index) > _collector->scope()->region_compaction_threshold(),
 64              "should be quite full");
 65     }
 66 #endif
 67     r->reset_skip_compacting_after_full_gc();
 68     return false;
 69   }
 70 };
 71 
 72 void G1FullGCCompactTask::G1CompactRegionClosure::clear_in_prev_bitmap(oop obj) {
 73   assert(_bitmap->is_marked(obj), "Should only compact marked objects");
 74   _bitmap->clear(obj);
 75 }
 76 
 77 size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
 78   size_t size = obj->size();
 79   if (!obj->is_forwarded()) {
 80     // Object not moving, but clear the mark to allow reuse of the bitmap.
 81     clear_in_prev_bitmap(obj);
 82     return size;
 83   }
 84   HeapWord* destination = cast_from_oop<HeapWord*>(_forwarding->forwardee(obj));

 85 
 86   // copy object and reinit its mark
 87   HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
 88   assert(obj_addr != destination, "everything in this pass should be moving");
 89   Copy::aligned_conjoint_words(obj_addr, destination, size);
 90   cast_to_oop(destination)->init_mark();
 91   assert(cast_to_oop(destination)->klass() != NULL, "should have a class");
 92 
 93   // Clear the mark for the compacted object to allow reuse of the
 94   // bitmap without an additional clearing step.
 95   clear_in_prev_bitmap(obj);
 96   return size;
 97 }
 98 
 99 void G1FullGCCompactTask::compact_region(HeapRegion* hr) {
100   assert(!hr->is_pinned(), "Should be no pinned region in compaction queue");
101   assert(!hr->is_humongous(), "Should be no humongous regions in compaction queue");
102 
103   if (!collector()->is_free(hr->hrm_index())) {
104     // The compaction closure not only copies the object to the new
105     // location, but also clears the bitmap for it. This is needed
106     // for bitmap verification and to be able to use the prev_bitmap
107     // for evacuation failures in the next young collection. Testing
108     // showed that it was better overall to clear bit by bit, compared
109     // to clearing the whole region at the end. This difference was
110     // clearly seen for regions with few marks.
111     G1CompactRegionClosure compact(collector()->mark_bitmap());
112     hr->apply_to_marked_objects(collector()->mark_bitmap(), &compact);
113   }
114 
115   hr->reset_compacted_after_full_gc();
116 }
117 
118 void G1FullGCCompactTask::work(uint worker_id) {
119   Ticks start = Ticks::now();
120   GrowableArray<HeapRegion*>* compaction_queue = collector()->compaction_point(worker_id)->regions();
121   for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
122        it != compaction_queue->end();
123        ++it) {
124     compact_region(*it);
125   }
126 
127   G1ResetSkipCompactingClosure hc(collector());
128   G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&hc, &_claimer, worker_id);
129   log_task("Compaction task", worker_id, start);
130 }
131 
132 void G1FullGCCompactTask::serial_compaction() {
133   GCTraceTime(Debug, gc, phases) tm("Phase 4: Serial Compaction", collector()->scope()->timer());
134   GrowableArray<HeapRegion*>* compaction_queue = collector()->serial_compaction_point()->regions();
135   for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
136        it != compaction_queue->end();
137        ++it) {
138     compact_region(*it);
139   }
140 }
--- EOF ---