1 /*
  2  * Copyright (c) 2017, 2023, 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/g1FullCollector.inline.hpp"
 27 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 28 #include "gc/g1/g1HeapRegion.hpp"
 29 #include "gc/shared/preservedMarks.inline.hpp"
 30 #include "oops/oop.inline.hpp"
 31 #include "utilities/debug.hpp"
 32 
 33 G1FullGCCompactionPoint::G1FullGCCompactionPoint(G1FullCollector* collector, PreservedMarks* preserved_stack) :
 34     _collector(collector),
 35     _current_region(nullptr),
 36     _compaction_top(nullptr),
 37     _preserved_stack(preserved_stack) {
 38   _compaction_regions = new (mtGC) GrowableArray<G1HeapRegion*>(32, mtGC);
 39   _compaction_region_iterator = _compaction_regions->begin();
 40 }
 41 
 42 G1FullGCCompactionPoint::~G1FullGCCompactionPoint() {
 43   delete _compaction_regions;
 44 }
 45 
 46 void G1FullGCCompactionPoint::update() {
 47   if (is_initialized()) {
 48     _collector->set_compaction_top(_current_region, _compaction_top);
 49   }
 50 }
 51 
 52 void G1FullGCCompactionPoint::initialize_values() {
 53   _compaction_top = _collector->compaction_top(_current_region);
 54 }
 55 
 56 bool G1FullGCCompactionPoint::has_regions() {
 57   return !_compaction_regions->is_empty();
 58 }
 59 
 60 bool G1FullGCCompactionPoint::is_initialized() {
 61   return _current_region != nullptr;
 62 }
 63 
 64 void G1FullGCCompactionPoint::initialize(G1HeapRegion* hr) {
 65   _current_region = hr;
 66   initialize_values();
 67 }
 68 
 69 G1HeapRegion* G1FullGCCompactionPoint::current_region() {
 70   return *_compaction_region_iterator;
 71 }
 72 
 73 G1HeapRegion* G1FullGCCompactionPoint::next_region() {
 74   G1HeapRegion* next = *(++_compaction_region_iterator);
 75   assert(next != nullptr, "Must return valid region");
 76   return next;
 77 }
 78 
 79 GrowableArray<G1HeapRegion*>* G1FullGCCompactionPoint::regions() {
 80   return _compaction_regions;
 81 }
 82 
 83 bool G1FullGCCompactionPoint::object_will_fit(size_t size) {
 84   size_t space_left = pointer_delta(_current_region->end(), _compaction_top);
 85   return size <= space_left;
 86 }
 87 
 88 void G1FullGCCompactionPoint::switch_region() {
 89   // Save compaction top in the region.
 90   _collector->set_compaction_top(_current_region, _compaction_top);
 91   // Get the next region and re-initialize the values.
 92   _current_region = next_region();
 93   initialize_values();
 94 }
 95 
 96 void G1FullGCCompactionPoint::forward(oop object, size_t size) {
 97   assert(_current_region != nullptr, "Must have been initialized");
 98 
 99   // Ensure the object fit in the current region.
100   while (!object_will_fit(size)) {
101     switch_region();
102   }
103 
104   // Store a forwarding pointer if the object should be moved.
105   if (cast_from_oop<HeapWord*>(object) != _compaction_top) {
106     if (!object->is_forwarded()) {
107       preserved_stack()->push_if_necessary(object, object->mark());
108     }
109     object->forward_to(cast_to_oop(_compaction_top));
110     assert(object->is_forwarded(), "must be forwarded");
111   } else {
112     assert(!object->is_forwarded(), "must not be forwarded");
113   }
114 
115   // Update compaction values.
116   _compaction_top += size;
117   _current_region->update_bot_for_block(_compaction_top - size, _compaction_top);
118 }
119 
120 void G1FullGCCompactionPoint::add(G1HeapRegion* hr) {
121   _compaction_regions->append(hr);
122 }
123 
124 void G1FullGCCompactionPoint::remove_at_or_above(uint bottom) {
125   G1HeapRegion* cur = current_region();
126   assert(cur->hrm_index() >= bottom, "Sanity!");
127 
128   int start_index = 0;
129   for (G1HeapRegion* r : *_compaction_regions) {
130     if (r->hrm_index() < bottom) {
131       start_index++;
132     }
133   }
134 
135   assert(start_index >= 0, "Should have at least one region");
136   _compaction_regions->trunc_to(start_index);
137 }
138 
139 void G1FullGCCompactionPoint::add_humongous(G1HeapRegion* hr) {
140   assert(hr->is_starts_humongous(), "Sanity!");
141 
142   _collector->add_humongous_region(hr);
143 
144   G1CollectedHeap* g1h = G1CollectedHeap::heap();
145   g1h->humongous_obj_regions_iterate(hr,
146                                      [&] (G1HeapRegion* r) {
147                                        add(r);
148                                        _collector->update_from_skip_compacting_to_compacting(r->hrm_index());
149                                      });
150 }
151 
152 void G1FullGCCompactionPoint::forward_humongous(G1HeapRegion* hr) {
153   assert(hr->is_starts_humongous(), "Sanity!");
154 
155   oop obj = cast_to_oop(hr->bottom());
156   size_t obj_size = obj->size();
157   uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size);
158 
159   if (!has_regions()) {
160     return;
161   }
162 
163   // Find contiguous compaction target regions for the humongous object.
164   uint range_begin = find_contiguous_before(hr, num_regions);
165 
166   if (range_begin == UINT_MAX) {
167     // No contiguous compaction target regions found, so the object cannot be moved.
168     return;
169   }
170 
171   // Preserve the mark for the humongous object as the region was initially not compacting.
172   preserved_stack()->push_if_necessary(obj, obj->mark());
173 
174   G1HeapRegion* dest_hr = _compaction_regions->at(range_begin);
175   obj->forward_to(cast_to_oop(dest_hr->bottom()));
176   assert(obj->is_forwarded(), "Object must be forwarded!");
177 
178   // Add the humongous object regions to the compaction point.
179   add_humongous(hr);
180 
181   // Remove covered regions from compaction target candidates.
182   _compaction_regions->remove_range(range_begin, (range_begin + num_regions));
183 
184   return;
185 }
186 
187 uint G1FullGCCompactionPoint::find_contiguous_before(G1HeapRegion* hr, uint num_regions) {
188   assert(num_regions > 0, "Sanity!");
189   assert(has_regions(), "Sanity!");
190 
191   if (num_regions == 1) {
192     // If only one region, return the first region.
193     return 0;
194   }
195 
196   uint contiguous_region_count = 1;
197 
198   uint range_end = 1;
199   uint range_limit = (uint)_compaction_regions->length();
200 
201   for (; range_end < range_limit; range_end++) {
202     if (contiguous_region_count == num_regions) {
203       break;
204     }
205     // Check if the current region and the previous region are contiguous.
206     bool regions_are_contiguous = (_compaction_regions->at(range_end)->hrm_index() - _compaction_regions->at(range_end - 1)->hrm_index()) == 1;
207     contiguous_region_count = regions_are_contiguous ? contiguous_region_count + 1 : 1;
208   }
209 
210   if (contiguous_region_count < num_regions &&
211       hr->hrm_index() - _compaction_regions->at(range_end-1)->hrm_index() != 1) {
212     // We reached the end but the final region is not contiguous with the target region;
213     // no contiguous regions to move to.
214     return UINT_MAX;
215   }
216   // Return the index of the first region in the range of contiguous regions.
217   return range_end - contiguous_region_count;
218 }