1 /*
  2  * Copyright (c) 2017, 2025, 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 "gc/g1/g1FullCollector.inline.hpp"
 26 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 27 #include "gc/g1/g1HeapRegion.hpp"
 28 #include "gc/shared/fullGCForwarding.inline.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   size_t old_size = size;
100   size_t new_size = object->copy_size(old_size, object->mark());
101   size = cast_from_oop<HeapWord*>(object) != _compaction_top ? new_size : old_size;
102 
103   // Ensure the object fit in the current region.
104   while (!object_will_fit(size)) {
105     switch_region();
106     size = cast_from_oop<HeapWord*>(object) != _compaction_top ? new_size : old_size;
107   }
108 
109   // Store a forwarding pointer if the object should be moved.
110   if (cast_from_oop<HeapWord*>(object) != _compaction_top) {
111     if (!object->is_forwarded()) {
112       preserved_stack()->push_if_necessary(object, object->mark());
113     }
114     FullGCForwarding::forward_to(object, cast_to_oop(_compaction_top));
115     assert(FullGCForwarding::is_forwarded(object), "must be forwarded");
116   } else {
117     assert(!FullGCForwarding::is_forwarded(object), "must not be forwarded");
118   }
119 
120   // Update compaction values.
121   _compaction_top += size;
122   _current_region->update_bot_for_block(_compaction_top - size, _compaction_top);
123 }
124 
125 void G1FullGCCompactionPoint::add(G1HeapRegion* hr) {
126   _compaction_regions->append(hr);
127 }
128 
129 void G1FullGCCompactionPoint::remove_at_or_above(uint bottom) {
130   G1HeapRegion* cur = current_region();
131   assert(cur->hrm_index() >= bottom, "Sanity!");
132 
133   int start_index = 0;
134   for (G1HeapRegion* r : *_compaction_regions) {
135     if (r->hrm_index() < bottom) {
136       start_index++;
137     }
138   }
139 
140   assert(start_index >= 0, "Should have at least one region");
141   _compaction_regions->trunc_to(start_index);
142 }
143 
144 void G1FullGCCompactionPoint::add_humongous(G1HeapRegion* hr) {
145   assert(hr->is_starts_humongous(), "Sanity!");
146 
147   _collector->add_humongous_region(hr);
148 
149   G1CollectedHeap* g1h = G1CollectedHeap::heap();
150   g1h->humongous_obj_regions_iterate(hr,
151                                      [&] (G1HeapRegion* r) {
152                                        add(r);
153                                        _collector->update_from_skip_compacting_to_compacting(r->hrm_index());
154                                      });
155 }
156 
157 void G1FullGCCompactionPoint::forward_humongous(G1HeapRegion* hr) {
158   assert(hr->is_starts_humongous(), "Sanity!");
159 
160   oop obj = cast_to_oop(hr->bottom());
161   size_t old_size = obj->size();
162   size_t new_size = obj->copy_size(old_size, obj->mark());
163   uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(new_size);
164 
165   if (!has_regions()) {
166     return;
167   }
168 
169   // Find contiguous compaction target regions for the humongous object.
170   uint range_begin = find_contiguous_before(hr, num_regions);
171 
172   if (range_begin == UINT_MAX) {
173     // No contiguous compaction target regions found, so the object cannot be moved.
174     return;
175   }
176 
177   // Preserve the mark for the humongous object as the region was initially not compacting.
178   preserved_stack()->push_if_necessary(obj, obj->mark());
179 
180   G1HeapRegion* dest_hr = _compaction_regions->at(range_begin);
181   assert(hr->bottom() != dest_hr->bottom(), "assuming actual humongous move");
182   FullGCForwarding::forward_to(obj, cast_to_oop(dest_hr->bottom()));
183   assert(FullGCForwarding::is_forwarded(obj), "Object must be forwarded!");
184 
185   // Add the humongous object regions to the compaction point.
186   add_humongous(hr);
187 
188   // Remove covered regions from compaction target candidates.
189   _compaction_regions->remove_range(range_begin, (range_begin + num_regions));
190 
191   return;
192 }
193 
194 uint G1FullGCCompactionPoint::find_contiguous_before(G1HeapRegion* hr, uint num_regions) {
195   assert(num_regions > 0, "Sanity!");
196   assert(has_regions(), "Sanity!");
197 
198   if (num_regions == 1) {
199     // If only one region, return the first region.
200     return 0;
201   }
202 
203   uint contiguous_region_count = 1;
204 
205   uint range_end = 1;
206   uint range_limit = (uint)_compaction_regions->length();
207 
208   for (; range_end < range_limit; range_end++) {
209     if (contiguous_region_count == num_regions) {
210       break;
211     }
212     // Check if the current region and the previous region are contiguous.
213     bool regions_are_contiguous = (_compaction_regions->at(range_end)->hrm_index() - _compaction_regions->at(range_end - 1)->hrm_index()) == 1;
214     contiguous_region_count = regions_are_contiguous ? contiguous_region_count + 1 : 1;
215   }
216 
217   if (contiguous_region_count < num_regions &&
218       hr->hrm_index() - _compaction_regions->at(range_end-1)->hrm_index() != 1) {
219     // We reached the end but the final region is not contiguous with the target region;
220     // no contiguous regions to move to.
221     return UINT_MAX;
222   }
223   // Return the index of the first region in the range of contiguous regions.
224   return range_end - contiguous_region_count;
225 }