1 /*
2 * Copyright (c) 2002, 2026, 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 "classfile/javaClasses.inline.hpp"
26 #include "gc/parallel/mutableSpace.hpp"
27 #include "gc/parallel/parallelScavengeHeap.hpp"
28 #include "gc/parallel/psOldGen.hpp"
29 #include "gc/parallel/psPromotionManager.inline.hpp"
30 #include "gc/parallel/psScavenge.hpp"
31 #include "gc/shared/continuationGCSupport.inline.hpp"
32 #include "gc/shared/gc_globals.hpp"
33 #include "gc/shared/gcTrace.hpp"
34 #include "gc/shared/partialArraySplitter.inline.hpp"
35 #include "gc/shared/partialArrayState.hpp"
36 #include "gc/shared/preservedMarks.inline.hpp"
37 #include "gc/shared/taskqueue.inline.hpp"
38 #include "logging/log.hpp"
39 #include "logging/logStream.hpp"
40 #include "memory/allocation.inline.hpp"
41 #include "memory/iterator.inline.hpp"
42 #include "memory/memRegion.hpp"
43 #include "memory/padded.inline.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "oops/access.inline.hpp"
46 #include "oops/compressedOops.inline.hpp"
47 #include "oops/oopsHierarchy.hpp"
48 #include "utilities/checkedCast.hpp"
49 #include "utilities/debug.hpp"
50
51 PaddedEnd<PSPromotionManager>* PSPromotionManager::_manager_array = nullptr;
52 PSPromotionManager::PSScannerTasksQueueSet* PSPromotionManager::_stack_array_depth = nullptr;
53 PreservedMarksSet* PSPromotionManager::_preserved_marks_set = nullptr;
54 PSOldGen* PSPromotionManager::_old_gen = nullptr;
55 MutableSpace* PSPromotionManager::_young_space = nullptr;
56 PartialArrayStateManager* PSPromotionManager::_partial_array_state_manager = nullptr;
57
58 void PSPromotionManager::initialize() {
59 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
60
61 _old_gen = heap->old_gen();
62 _young_space = heap->young_gen()->to_space();
63
64 const uint promotion_manager_num = ParallelGCThreads;
65
66 assert(_partial_array_state_manager == nullptr, "Attempt to initialize twice");
67 _partial_array_state_manager
68 = new PartialArrayStateManager(promotion_manager_num);
69
70 // To prevent false sharing, we pad the PSPromotionManagers
71 // and make sure that the first instance starts at a cache line.
72 assert(_manager_array == nullptr, "Attempt to initialize twice");
73 _manager_array = PaddedArray<PSPromotionManager, mtGC>::create_unfreeable(promotion_manager_num);
74
75 _stack_array_depth = new PSScannerTasksQueueSet(promotion_manager_num);
76
77 // Create and register the PSPromotionManager(s) for the worker threads.
78 for(uint i=0; i<ParallelGCThreads; i++) {
79 stack_array_depth()->register_queue(i, _manager_array[i].claimed_stack_depth());
80 }
81 // The VMThread gets its own PSPromotionManager, which is not available
82 // for work stealing.
83
84 assert(_preserved_marks_set == nullptr, "Attempt to initialize twice");
85 _preserved_marks_set = new PreservedMarksSet(true /* in_c_heap */);
86 _preserved_marks_set->init(promotion_manager_num);
87 for (uint i = 0; i < promotion_manager_num; i += 1) {
88 _manager_array[i].register_preserved_marks(_preserved_marks_set->get(i));
89 }
90 }
91
92 PSPromotionManager* PSPromotionManager::gc_thread_promotion_manager(uint index) {
93 assert(index < ParallelGCThreads, "index out of range");
94 assert(_manager_array != nullptr, "Sanity");
95 return &_manager_array[index];
96 }
97
98 PSPromotionManager* PSPromotionManager::vm_thread_promotion_manager() {
99 assert(_manager_array != nullptr, "Sanity");
100 return &_manager_array[0];
101 }
102
103 void PSPromotionManager::pre_scavenge() {
104 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
105
106 _preserved_marks_set->assert_empty();
107 _young_space = heap->young_gen()->to_space();
108
109 for(uint i=0; i<ParallelGCThreads; i++) {
110 manager_array(i)->reset();
111 }
112 }
113
114 bool PSPromotionManager::post_scavenge(YoungGCTracer& gc_tracer) {
115 bool promotion_failure_occurred = false;
116
117 TASKQUEUE_STATS_ONLY(print_and_reset_taskqueue_stats());
118 for (uint i = 0; i < ParallelGCThreads; i++) {
119 PSPromotionManager* manager = manager_array(i);
120 assert(manager->claimed_stack_depth()->is_empty(), "should be empty");
121 if (manager->_promotion_failed_info.has_failed()) {
122 gc_tracer.report_promotion_failed(manager->_promotion_failed_info);
123 promotion_failure_occurred = true;
124 }
125 manager->flush_labs();
126 manager->flush_string_dedup_requests();
127 }
128 // All PartialArrayStates have been returned to the allocator, since the
129 // claimed_stack_depths are all empty. Leave them there for use by future
130 // collections.
131
132 if (!promotion_failure_occurred) {
133 // If there was no promotion failure, the preserved mark stacks
134 // should be empty.
135 _preserved_marks_set->assert_empty();
136 }
137 return promotion_failure_occurred;
138 }
139
140 #if TASKQUEUE_STATS
141
142 void PSPromotionManager::print_and_reset_taskqueue_stats() {
143 stack_array_depth()->print_and_reset_taskqueue_stats("Young GC");
144
145 auto get_pa_stats = [&](uint i) {
146 return manager_array(i)->partial_array_task_stats();
147 };
148 PartialArrayTaskStats::log_set(ParallelGCThreads, get_pa_stats,
149 "Young GC Partial Array");
150 for (uint i = 0; i < ParallelGCThreads; ++i) {
151 get_pa_stats(i)->reset();
152 }
153 }
154
155 PartialArrayTaskStats* PSPromotionManager::partial_array_task_stats() {
156 return _partial_array_splitter.stats();
157 }
158
159 #endif // TASKQUEUE_STATS
160
161 // Most members are initialized either by initialize() or reset().
162 PSPromotionManager::PSPromotionManager()
163 : _partial_array_splitter(_partial_array_state_manager, ParallelGCThreads)
164 {
165 // We set the old lab's start array.
166 _old_lab.set_start_array(old_gen()->start_array());
167
168 // let's choose 1.5x the chunk size
169 _min_array_size_for_chunking = (3 * ParGCArrayScanChunk / 2);
170
171 _preserved_marks = nullptr;
172
173 reset();
174 }
175
176 void PSPromotionManager::reset() {
177 assert(stacks_empty(), "reset of non-empty stack");
178
179 // We need to get an assert in here to make sure the labs are always flushed.
180
181 // Do not prefill the LAB's, save heap wastage!
182 HeapWord* lab_base = young_space()->top();
183 _young_lab.initialize(MemRegion(lab_base, (size_t)0));
184 _young_gen_has_alloc_failure = false;
185 _young_gen_is_full = false;
186
187 lab_base = old_gen()->object_space()->top();
188 _old_lab.initialize(MemRegion(lab_base, (size_t)0));
189 _old_gen_is_full = false;
190
191 _promotion_failed_info.reset();
192 }
193
194 void PSPromotionManager::register_preserved_marks(PreservedMarks* preserved_marks) {
195 assert(_preserved_marks == nullptr, "do not set it twice");
196 _preserved_marks = preserved_marks;
197 }
198
199 void PSPromotionManager::restore_preserved_marks() {
200 _preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
201 }
202
203 void PSPromotionManager::trim_stacks_to_threshold(uint threshold) {
204 PSScannerTasksQueue* const tq = claimed_stack_depth();
205 do {
206 ScannerTask task;
207
208 // Drain overflow stack first, so other threads can steal from
209 // claimed stack while we work.
210 while (tq->pop_overflow(task)) {
211 if (!tq->try_push_to_taskqueue(task)) {
212 process_popped_location_depth(task, false);
213 }
214 }
215
216 while (tq->pop_local(task, threshold)) {
217 process_popped_location_depth(task, false);
218 }
219 } while (!tq->overflow_empty());
220
221 assert(tq->size() <= threshold, "Sanity");
222 assert(tq->overflow_empty(), "Sanity");
223 }
224
225 void PSPromotionManager::trim_stacks() {
226 const uint target_stack_size = GCDrainStackTargetSize;
227 const uint max_stack_size = target_stack_size * 2 + 1;
228
229 PSScannerTasksQueue* const tq = claimed_stack_depth();
230 if (!tq->overflow_empty() || tq->size() > max_stack_size) {
231 trim_stacks_to_threshold(target_stack_size);
232 }
233 }
234
235 void PSPromotionManager::drain_stacks() {
236 trim_stacks_to_threshold(0);
237 }
238
239 void PSPromotionManager::flush_labs() {
240 assert(stacks_empty(), "Attempt to flush lab with live stack");
241
242 // If either promotion lab fills up, we can flush the
243 // lab but not refill it, so check first.
244 assert(!_young_lab.is_flushed() || _young_gen_is_full, "Sanity");
245 if (!_young_lab.is_flushed())
246 _young_lab.flush();
247
248 assert(!_old_lab.is_flushed() || _old_gen_is_full, "Sanity");
249 if (!_old_lab.is_flushed())
250 _old_lab.flush();
251
252 // Let PSScavenge know if we overflowed
253 if (_young_gen_is_full || _young_gen_has_alloc_failure) {
254 PSScavenge::set_survivor_overflow(true);
255 }
256 }
257
258 void PSPromotionManager::process_array_chunk(objArrayOop obj, size_t start, size_t end) {
259 PSPushContentsClosure pcc(this);
260 obj->oop_iterate_elements_range(&pcc,
261 checked_cast<int>(start),
262 checked_cast<int>(end));
263 }
264
265 void PSPromotionManager::process_array_chunk(PartialArrayState* state, bool stolen) {
266 // Access before release by claim().
267 objArrayOop to_array = objArrayOop(state->destination());
268 precond(to_array->is_array_with_oops());
269
270 PartialArraySplitter::Claim claim =
271 _partial_array_splitter.claim(state, &_claimed_stack_depth, stolen);
272
273 process_array_chunk(to_array, claim._start, claim._end);
274 }
275
276 void PSPromotionManager::push_objArray(oop old_obj, oop new_obj) {
277 assert(old_obj->is_forwarded(), "precondition");
278 assert(old_obj->forwardee() == new_obj, "precondition");
279 precond(new_obj->is_array_with_oops());
280
281 objArrayOop to_array = objArrayOop(new_obj);
282 size_t array_length = to_array->length();
283 size_t initial_chunk_size =
284 // The source array is unused when processing states.
285 _partial_array_splitter.start(&_claimed_stack_depth, nullptr, to_array, array_length, ParGCArrayScanChunk);
286
287 process_array_chunk(to_array, 0, initial_chunk_size);
288 }
289
290 oop PSPromotionManager::oop_promotion_failed(oop obj, markWord obj_mark) {
291 assert(_old_gen_is_full || PromotionFailureALot, "Sanity");
292
293 // Attempt to CAS in the header.
294 // This tests if the header is still the same as when
295 // this started. If it is the same (i.e., no forwarding
296 // pointer has been installed), then this thread owns
297 // it.
298 if (obj->forward_to_self_atomic(obj_mark) == nullptr) {
299 // We won any races, we "own" this object.
300 assert(obj == obj->forwardee(), "Sanity");
301
302 _promotion_failed_info.register_copy_failure(obj->size());
303
304 ContinuationGCSupport::transform_stack_chunk(obj);
305
306 push_contents(obj, obj->klass());
307
308 // Save the markWord of promotion-failed objs in _preserved_marks for later
309 // restoration. This way we don't have to walk the young-gen to locate
310 // these promotion-failed objs.
311 _preserved_marks->push_always(obj, obj_mark);
312 } else {
313 // We lost, someone else "owns" this object
314 guarantee(obj->is_forwarded(), "Object must be forwarded if the cas failed.");
315
316 // No unallocation to worry about.
317 obj = obj->forwardee();
318 }
319
320 return obj;
321 }