1 /*
2 * Copyright (c) 2024, 2026, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2021, 2022, Red Hat, Inc. All rights reserved.
4 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27
28 #include "gc/shared/barrierSetNMethod.hpp"
29 #include "gc/shared/collectorCounters.hpp"
30 #include "gc/shared/continuationGCSupport.inline.hpp"
31 #include "gc/shenandoah/shenandoahBreakpoint.hpp"
32 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
33 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
34 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
35 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
36 #include "gc/shenandoah/shenandoahFreeSet.hpp"
37 #include "gc/shenandoah/shenandoahGeneration.hpp"
38 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
39 #include "gc/shenandoah/shenandoahLock.hpp"
40 #include "gc/shenandoah/shenandoahMark.inline.hpp"
41 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
42 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
43 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
44 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
45 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
46 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
47 #include "gc/shenandoah/shenandoahUtils.hpp"
48 #include "gc/shenandoah/shenandoahVerifier.hpp"
49 #include "gc/shenandoah/shenandoahVMOperations.hpp"
50 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
51 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
52 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
53 #include "memory/allocation.hpp"
54 #include "prims/jvmtiTagMap.hpp"
55 #include "runtime/vmThread.hpp"
56 #include "utilities/events.hpp"
57
58 // Breakpoint support
59 class ShenandoahBreakpointGCScope : public StackObj {
60 private:
61 const GCCause::Cause _cause;
62 public:
63 ShenandoahBreakpointGCScope(GCCause::Cause cause) : _cause(cause) {
64 if (cause == GCCause::_wb_breakpoint) {
65 ShenandoahBreakpoint::start_gc();
66 ShenandoahBreakpoint::at_before_gc();
67 }
68 }
69
70 ~ShenandoahBreakpointGCScope() {
71 if (_cause == GCCause::_wb_breakpoint) {
72 ShenandoahBreakpoint::at_after_gc();
73 }
74 }
75 };
76
77 class ShenandoahBreakpointMarkScope : public StackObj {
78 private:
79 const GCCause::Cause _cause;
80 public:
81 ShenandoahBreakpointMarkScope(GCCause::Cause cause) : _cause(cause) {
82 if (_cause == GCCause::_wb_breakpoint) {
83 ShenandoahBreakpoint::at_after_marking_started();
84 }
85 }
86
87 ~ShenandoahBreakpointMarkScope() {
88 if (_cause == GCCause::_wb_breakpoint) {
89 ShenandoahBreakpoint::at_before_marking_completed();
90 }
91 }
92 };
93
94 ShenandoahConcurrentGC::ShenandoahConcurrentGC(ShenandoahGeneration* generation, bool do_old_gc_bootstrap) :
95 ShenandoahGC(generation),
96 _mark(generation),
97 _degen_point(ShenandoahDegenPoint::_degenerated_unset),
98 _abbreviated(false),
99 _do_old_gc_bootstrap(do_old_gc_bootstrap) {
100 }
101
102 ShenandoahGC::ShenandoahDegenPoint ShenandoahConcurrentGC::degen_point() const {
103 return _degen_point;
104 }
105
106 void ShenandoahConcurrentGC::entry_concurrent_update_refs_prepare(ShenandoahHeap* const heap) {
107 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
108 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent init update refs", "");
109 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs_prepare);
110 EventMark em("%s", msg);
111
112 heap->try_inject_pin();
113 // Evacuation is complete, retire gc labs and change gc state
114 heap->concurrent_prepare_for_update_refs();
115 }
116
117 void ShenandoahConcurrentGC::entry_update_card_table() {
118 ShenandoahHeap* const heap = ShenandoahHeap::heap();
119 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
120 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent update cards", "");
121 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_update_card_table);
122 EventMark em("%s", msg);
123
124 ShenandoahWorkerScope scope(heap->workers(),
125 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
126 "concurrent update cards");
127
128 heap->try_inject_pin();
129 // Heap needs to be parsable here.
130 // Also, parallel heap region iterate must have a phase set.
131 assert(ShenandoahTimingsTracker::is_current_phase_valid(), "Current phase must be set");
132 ShenandoahGenerationalHeap::heap()->old_generation()->update_card_table();
133 }
134
135 bool ShenandoahConcurrentGC::collect(GCCause::Cause cause) {
136 ShenandoahHeap* const heap = ShenandoahHeap::heap();
137 _generation->ref_processor()->set_soft_reference_policy(
138 GCCause::should_clear_all_soft_refs(cause));
139
140 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent GC", "");
141 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_gc, /* log_heap_usage = */ true);
142
143 ShenandoahBreakpointGCScope breakpoint_gc_scope(cause);
144
145 // Reset for upcoming marking
146 entry_reset();
147
148 // Start initial mark under STW
149 vmop_entry_init_mark();
150
151 {
152 ShenandoahBreakpointMarkScope breakpoint_mark_scope(cause);
153
154 // Reset task queue stats here, rather than in mark_concurrent_roots,
155 // because remembered set scan will `push` oops into the queues and
156 // resetting after this happens will lose those counts.
157 TASKQUEUE_STATS_ONLY(_mark.task_queues()->reset_taskqueue_stats());
158
159 // Concurrent remembered set scanning
160 entry_scan_remembered_set();
161
162 // Concurrent mark roots
163 entry_mark_roots();
164 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_roots)) {
165 return false;
166 }
167
168 // Continue concurrent mark
169 entry_mark();
170 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) {
171 return false;
172 }
173 }
174
175 // Complete marking under STW, and start evacuation
176 vmop_entry_final_mark();
177
178 // If the GC was cancelled before final mark, nothing happens on the safepoint. We are still
179 // in the marking phase and must resume the degenerated cycle from there. If the GC was cancelled
180 // after final mark, then we've entered the evacuation phase and must resume the degenerated cycle
181 // from that phase.
182 if (_generation->is_concurrent_mark_in_progress()) {
183 bool cancelled = check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark);
184 assert(cancelled, "GC must have been cancelled between concurrent and final mark");
185 return false;
186 }
187
188 assert(heap->is_concurrent_weak_root_in_progress(), "Must be doing weak roots now");
189
190 // Finish all thread/stack roots if needed. This completes stack watermark processing.
191 if (heap->is_evacuation_in_progress()) {
192 entry_thread_roots();
193 }
194
195 // Process weak roots that might still point to regions that would be broken by cleanup.
196 // We cannot recycle regions because weak roots need to know what is marked in trashed regions.
197 entry_weak_refs();
198 entry_weak_roots();
199
200 // Perform concurrent class unloading before any regions get recycled. Class unloading may
201 // need to inspect unmarked objects in trashed regions.
202 if (heap->unload_classes()) {
203 entry_class_unloading();
204 }
205
206 // Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
207 // the space. This would be the last action if there is nothing to evacuate. Note that
208 // we will not age young-gen objects in the case that we skip evacuation.
209 entry_cleanup_early();
210
211 // Processing strong roots
212 // This may be skipped if there is nothing to update/evacuate.
213 // If so, strong_root_in_progress would be unset.
214 if (heap->is_concurrent_strong_root_in_progress()) {
215 entry_strong_roots();
216 }
217
218 // Roots processing is complete, put the weak roots flag down.
219 entry_final_roots();
220
221 // Continue the cycle with evacuation and optional update-refs.
222 // This may be skipped if there is nothing to evacuate.
223 // If so, evac_in_progress would be unset by collection set preparation code.
224 if (heap->is_evacuation_in_progress()) {
225 // Concurrently evacuate
226 entry_evacuate();
227 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) {
228 return false;
229 }
230
231 // Perform update-refs phase.
232 entry_concurrent_update_refs_prepare(heap);
233
234 if (ShenandoahHeap::heap()->mode()->is_generational()) {
235 entry_update_card_table();
236 }
237
238 if (ShenandoahVerify) {
239 vmop_entry_init_update_refs();
240 }
241
242 entry_update_refs();
243 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_update_refs)) {
244 return false;
245 }
246
247 // Concurrent update thread roots
248 entry_update_thread_roots();
249 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_update_refs)) {
250 return false;
251 }
252
253 vmop_entry_final_update_refs();
254
255 // Update references freed up collection set, kick the cleanup to reclaim the space.
256 entry_cleanup_complete();
257 } else {
258 _abbreviated = true;
259
260 if (heap->mode()->is_generational()) {
261 entry_complete_abbreviated_cycle();
262
263 // If the promote-in-place operation was cancelled, we can have the degenerated
264 // cycle complete the operation. It will see that no evacuations are in progress,
265 // and that there are regions wanting promotion. The risk with not handling the
266 // cancellation would be failing to restore top for these regions and leaving
267 // them unable to serve allocations for the old generation.
268 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) {
269 return false;
270 }
271 }
272
273 // In normal cycle, final-update-refs would verify at the end of the cycle.
274 // In abbreviated cycle, we need to verify separately.
275 if (ShenandoahVerify) {
276 vmop_entry_final_verify();
277 }
278 }
279
280 // We defer generation resizing actions until after cset regions have been recycled. We do this even following an
281 // abbreviated cycle.
282 if (heap->mode()->is_generational()) {
283 ShenandoahGenerationalHeap::heap()->complete_concurrent_cycle();
284 }
285
286 // Instead of always resetting immediately before the start of a new GC, we can often reset at the end of the
287 // previous GC. This allows us to start the next GC cycle more quickly after a trigger condition is detected,
288 // reducing the likelihood that GC will degenerate.
289 entry_reset_after_collect();
290
291 return true;
292 }
293
294 void ShenandoahConcurrentGC::entry_complete_abbreviated_cycle() {
295 shenandoah_assert_generational();
296
297 ShenandoahGenerationalHeap* const heap = ShenandoahGenerationalHeap::heap();
298
299 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
300 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent complete abbreviated cycle", "");
301 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::complete_abbreviated);
302 EventMark em("%s", msg);
303
304 ShenandoahWorkerScope scope(heap->workers(),
305 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
306 msg);
307
308 heap->try_inject_pin();
309 // We chose not to evacuate because we found sufficient immediate garbage.
310 // However, there may still be regions to promote in place, so do that now.
311 if (heap->old_generation()->has_in_place_promotions()) {
312 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::complete_abbreviated_promote_in_place);
313 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::complete_abbreviated_promote_in_place);
314 heap->promote_regions_in_place(_generation, true);
315 }
316
317 // At this point, the cycle is effectively complete. If the cycle has been cancelled here,
318 // the control thread will detect it on its next iteration and run a degenerated young cycle.
319 if (!heap->cancelled_gc() && !_generation->is_old()) {
320 ShenandoahTimingsTracker tracker(ShenandoahPhaseTimings::complete_abbreviated_update_region_ages);
321 heap->update_region_ages(_generation->complete_marking_context());
322 }
323 }
324
325 void ShenandoahConcurrentGC::vmop_entry_init_mark() {
326 ShenandoahHeap* const heap = ShenandoahHeap::heap();
327 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
328 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_mark_gross);
329
330 heap->try_inject_alloc_failure();
331 VM_ShenandoahInitMark op(this);
332 VMThread::execute(&op); // jump to entry_init_mark() under safepoint
333 }
334
335 void ShenandoahConcurrentGC::vmop_entry_final_mark() {
336 ShenandoahHeap* const heap = ShenandoahHeap::heap();
337 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
338 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_gross);
339
340 heap->try_inject_alloc_failure();
341 VM_ShenandoahFinalMarkStartEvac op(this);
342 VMThread::execute(&op); // jump to entry_final_mark under safepoint
343 heap->try_inject_pin();
344 }
345
346 void ShenandoahConcurrentGC::vmop_entry_init_update_refs() {
347 ShenandoahHeap* const heap = ShenandoahHeap::heap();
348 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
349 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_update_refs_gross);
350
351 heap->try_inject_alloc_failure();
352 heap->try_inject_pin();
353 VM_ShenandoahInitUpdateRefs op(this);
354 VMThread::execute(&op);
355 }
356
357 void ShenandoahConcurrentGC::vmop_entry_final_update_refs() {
358 ShenandoahHeap* const heap = ShenandoahHeap::heap();
359 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
360 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_gross);
361
362 heap->try_inject_alloc_failure();
363 heap->try_inject_pin();
364 VM_ShenandoahFinalUpdateRefs op(this);
365 VMThread::execute(&op);
366 }
367
368 void ShenandoahConcurrentGC::vmop_entry_final_verify() {
369 ShenandoahHeap* const heap = ShenandoahHeap::heap();
370 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
371 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_verify_gross);
372
373 // This phase does not use workers, no need for setup
374 heap->try_inject_alloc_failure();
375 heap->try_inject_pin();
376 VM_ShenandoahFinalVerify op(this);
377 VMThread::execute(&op);
378 }
379
380 void ShenandoahConcurrentGC::entry_init_mark() {
381 ShenandoahHeap* const heap = ShenandoahHeap::heap();
382 assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
383
384 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Pause Init Mark", "");
385 ShenandoahPauseSubphase gc_phase(msg, ShenandoahPhaseTimings::init_mark);
386 EventMark em("%s", msg);
387
388 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
389 ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
390 "init marking");
391
392 op_init_mark();
393 }
394
395 void ShenandoahConcurrentGC::entry_final_mark() {
396 ShenandoahHeap* const heap = ShenandoahHeap::heap();
397 assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
398 "Should not have forwarded objects during final mark, unless old gen concurrent mark is running");
399
400 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Pause Final Mark", "");
401 ShenandoahPauseSubphase gc_phase(msg, ShenandoahPhaseTimings::final_mark);
402 EventMark em("%s", msg);
403
404 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
405 ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
406 "final marking");
407
408 op_final_mark();
409 }
410
411 void ShenandoahConcurrentGC::entry_init_update_refs() {
412 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Pause Init Update Refs", "");
413 ShenandoahPauseSubphase gc_phase(msg, ShenandoahPhaseTimings::init_update_refs);
414 EventMark em("%s", msg);
415
416 // No workers used in this phase, no setup required
417 op_init_update_refs();
418 }
419
420 void ShenandoahConcurrentGC::entry_final_update_refs() {
421 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Pause Final Update Refs", "");
422 ShenandoahPauseSubphase gc_phase(msg, ShenandoahPhaseTimings::final_update_refs);
423 EventMark em("%s", msg);
424
425 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
426 ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
427 "final reference update");
428
429 op_final_update_refs();
430 }
431
432 void ShenandoahConcurrentGC::entry_final_verify() {
433 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Pause Verify Final", "");
434 ShenandoahPauseSubphase gc_phase(msg, ShenandoahPhaseTimings::final_verify);
435 EventMark em("%s", msg);
436
437 op_verify_final();
438 }
439
440 void ShenandoahConcurrentGC::entry_reset() {
441 ShenandoahHeap* const heap = ShenandoahHeap::heap();
442 heap->release_injected_pins();
443 heap->try_inject_alloc_failure();
444
445 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
446 {
447 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent reset", "");
448 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_reset);
449 EventMark em("%s", msg);
450
451 ShenandoahWorkerScope scope(heap->workers(),
452 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
453 msg);
454 op_reset();
455 }
456 }
457
458 void ShenandoahConcurrentGC::entry_scan_remembered_set() {
459 if (_generation->is_young()) {
460 ShenandoahHeap* const heap = ShenandoahHeap::heap();
461 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
462
463 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent remembered set scanning", "");
464 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::init_scan_rset);
465 EventMark em("%s", msg);
466
467 ShenandoahWorkerScope scope(heap->workers(),
468 ShenandoahWorkerPolicy::calc_workers_for_rs_scanning(),
469 msg);
470
471 heap->try_inject_alloc_failure();
472 _generation->scan_remembered_set(true /* is_concurrent */);
473 }
474 }
475
476 void ShenandoahConcurrentGC::entry_mark_roots() {
477 ShenandoahHeap* const heap = ShenandoahHeap::heap();
478 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
479 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent marking roots", "");
480 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_mark_roots);
481 EventMark em("%s", msg);
482
483 ShenandoahWorkerScope scope(heap->workers(),
484 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
485 "concurrent marking roots");
486
487 heap->try_inject_alloc_failure();
488 op_mark_roots();
489 }
490
491 void ShenandoahConcurrentGC::entry_mark() {
492 ShenandoahHeap* const heap = ShenandoahHeap::heap();
493 assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
494 "Should not have forwarded objects concurrent mark, unless old gen concurrent mark is running");
495
496 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
497 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent marking", "");
498 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_mark);
499 EventMark em("%s", msg);
500
501 ShenandoahWorkerScope scope(heap->workers(),
502 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
503 "concurrent marking");
504
505 heap->try_inject_alloc_failure();
506 op_mark();
507 heap->try_inject_pin();
508 }
509
510 void ShenandoahConcurrentGC::entry_thread_roots() {
511 ShenandoahHeap* const heap = ShenandoahHeap::heap();
512 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent thread roots", "");
513 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_thread_roots);
514 EventMark em("%s", msg);
515
516 ShenandoahWorkerScope scope(heap->workers(),
517 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
518 msg);
519
520 heap->try_inject_alloc_failure();
521 heap->try_inject_pin();
522 op_thread_roots();
523 }
524
525 void ShenandoahConcurrentGC::entry_weak_refs() {
526 ShenandoahHeap* const heap = ShenandoahHeap::heap();
527 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent weak references", "");
528 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_refs);
529 EventMark em("%s", msg);
530
531 ShenandoahWorkerScope scope(heap->workers(),
532 ShenandoahWorkerPolicy::calc_workers_for_conc_refs_processing(),
533 "concurrent weak references");
534
535 heap->try_inject_alloc_failure();
536 heap->try_inject_pin();
537 op_weak_refs();
538 }
539
540 void ShenandoahConcurrentGC::entry_weak_roots() {
541 ShenandoahHeap* const heap = ShenandoahHeap::heap();
542 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
543 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent weak roots", "");
544 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_roots);
545 EventMark em("%s", msg);
546
547 ShenandoahWorkerScope scope(heap->workers(),
548 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
549 "concurrent weak root");
550
551 heap->try_inject_alloc_failure();
552 heap->try_inject_pin();
553 op_weak_roots();
554 }
555
556 void ShenandoahConcurrentGC::entry_class_unloading() {
557 ShenandoahHeap* const heap = ShenandoahHeap::heap();
558 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
559 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent class unloading", "");
560 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_class_unload);
561 EventMark em("%s", msg);
562
563 ShenandoahWorkerScope scope(heap->workers(),
564 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
565 "concurrent class unloading");
566
567 heap->try_inject_alloc_failure();
568 heap->try_inject_pin();
569 op_class_unloading();
570 }
571
572 void ShenandoahConcurrentGC::entry_strong_roots() {
573 ShenandoahHeap* const heap = ShenandoahHeap::heap();
574 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
575 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent strong roots", "");
576 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_strong_roots);
577 EventMark em("%s", msg);
578
579 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_strong_roots);
580
581 ShenandoahWorkerScope scope(heap->workers(),
582 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
583 "concurrent strong root");
584
585 heap->try_inject_alloc_failure();
586 heap->try_inject_pin();
587 op_strong_roots();
588 }
589
590 void ShenandoahConcurrentGC::entry_cleanup_early() {
591 ShenandoahHeap* const heap = ShenandoahHeap::heap();
592 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
593 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent cleanup", "");
594 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_early, false /* log_heap_usage */);
595 EventMark em("%s", msg);
596
597 // This phase does not use workers, no need for setup
598 heap->try_inject_alloc_failure();
599 heap->try_inject_pin();
600 op_cleanup_early();
601 if (!heap->is_evacuation_in_progress()) {
602 // This is an abbreviated cycle. Rebuild the freeset in order to establish reserves for the next GC cycle. Doing
603 // the rebuild ASAP also expedites availability of immediate trash, reducing the likelihood that we will degenerate
604 // during promote-in-place processing.
605 heap->rebuild_free_set(true /*concurrent*/);
606 }
607 }
608
609 void ShenandoahConcurrentGC::entry_evacuate() {
610 ShenandoahHeap* const heap = ShenandoahHeap::heap();
611 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
612 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent evacuation", "");
613 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_evac);
614 EventMark em("%s", msg);
615
616 ShenandoahWorkerScope scope(heap->workers(),
617 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
618 "concurrent evacuation");
619
620 heap->try_inject_alloc_failure();
621 heap->try_inject_pin();
622 op_evacuate();
623 }
624
625 void ShenandoahConcurrentGC::entry_update_thread_roots() {
626 ShenandoahHeap* const heap = ShenandoahHeap::heap();
627 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
628 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent update thread roots", "");
629 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_update_thread_roots);
630 EventMark em("%s", msg);
631
632 // No workers used in this phase, no setup required
633 heap->try_inject_alloc_failure();
634 heap->try_inject_pin();
635 op_update_thread_roots();
636 }
637
638 void ShenandoahConcurrentGC::entry_update_refs() {
639 ShenandoahHeap* const heap = ShenandoahHeap::heap();
640 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
641 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent update references", "");
642 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs);
643 EventMark em("%s", msg);
644
645 ShenandoahWorkerScope scope(heap->workers(),
646 ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
647 "concurrent reference update");
648
649 heap->try_inject_alloc_failure();
650 heap->try_inject_pin();
651 op_update_refs();
652 }
653
654 void ShenandoahConcurrentGC::entry_cleanup_complete() {
655 ShenandoahHeap* const heap = ShenandoahHeap::heap();
656 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
657 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent cleanup", "");
658 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_complete, false /* log_heap_usage */);
659 EventMark em("%s", msg);
660
661 // This phase does not use workers, no need for setup
662 heap->try_inject_alloc_failure();
663 op_cleanup_complete();
664 }
665
666 void ShenandoahConcurrentGC::entry_reset_after_collect() {
667 ShenandoahHeap* const heap = ShenandoahHeap::heap();
668 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
669 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent reset after collect", "");
670 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_reset_after_collect);
671 EventMark em("%s", msg);
672
673 op_reset_after_collect();
674 }
675
676 void ShenandoahConcurrentGC::op_reset() {
677 ShenandoahHeap* const heap = ShenandoahHeap::heap();
678
679 // If it is old GC bootstrap cycle, always clear bitmap for global gen
680 // to ensure bitmap for old gen is clear for old GC cycle after this.
681 if (_do_old_gc_bootstrap) {
682 assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot reset old without making it parsable");
683 heap->global_generation()->prepare_gc();
684 } else {
685 _generation->prepare_gc();
686 }
687
688 if (heap->mode()->is_generational()) {
689 heap->old_generation()->card_scan()->mark_read_table_as_clean();
690 }
691 }
692
693 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
694 private:
695 ShenandoahMarkingContext* const _ctx;
696 public:
697 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
698
699 void heap_region_do(ShenandoahHeapRegion* r) {
700 assert(!r->has_live(), "Region %zu should have no live data", r->index());
701 if (r->is_active()) {
702 // Check if region needs updating its TAMS. We have updated it already during concurrent
703 // reset, so it is very likely we don't need to do another write here. Since most regions
704 // are not "active", this path is relatively rare.
705 if (_ctx->top_at_mark_start(r) != r->top()) {
706 _ctx->capture_top_at_mark_start(r);
707 }
708 } else {
709 assert(_ctx->top_at_mark_start(r) == r->top(),
710 "Region %zu should already have correct TAMS", r->index());
711 }
712 }
713
714 bool is_thread_safe() { return true; }
715 };
716
717 void ShenandoahConcurrentGC::start_mark() {
718 _mark.start_mark();
719 }
720
721 void ShenandoahConcurrentGC::op_init_mark() {
722 ShenandoahHeap* const heap = ShenandoahHeap::heap();
723 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
724 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
725
726 assert(_generation->is_bitmap_clear(), "need clear marking bitmap");
727 assert(!_generation->is_mark_complete(), "should not be complete");
728 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
729
730 if (heap->mode()->is_generational()) {
731 if (_generation->is_global()) {
732 heap->old_generation()->cancel_gc();
733 }
734
735 {
736 // After we swap card table below, the write-table is all clean, and the read table holds
737 // cards dirty prior to the start of GC. Young and bootstrap collection will update
738 // the write card table as a side effect of remembered set scanning. Global collection will
739 // update the card table as a side effect of global marking of old objects.
740 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_swap_rset);
741 _generation->swap_card_tables();
742 }
743 }
744
745 if (ShenandoahVerify) {
746 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::init_mark_verify);
747 heap->verifier()->verify_before_concmark(_generation);
748 }
749
750 if (VerifyBeforeGC) {
751 Universe::verify();
752 }
753
754 _generation->set_concurrent_mark_in_progress(true);
755
756 start_mark();
757
758 if (_do_old_gc_bootstrap) {
759 shenandoah_assert_generational();
760 // Update region state for both young and old regions
761 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
762 ShenandoahInitMarkUpdateRegionStateClosure cl;
763 heap->parallel_heap_region_iterate(&cl);
764 heap->old_generation()->ref_processor()->reset_thread_locals();
765 } else {
766 // Update region state for only young regions
767 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
768 ShenandoahInitMarkUpdateRegionStateClosure cl;
769 _generation->parallel_heap_region_iterate(&cl);
770 }
771
772 // Weak reference processing
773 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
774 rp->reset_thread_locals();
775
776 // Make above changes visible to worker threads
777 OrderAccess::fence();
778
779 // Arm nmethods/stack for concurrent processing
780 ShenandoahCodeRoots::arm_nmethods();
781 ShenandoahStackWatermark::change_epoch_id();
782
783 {
784 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_propagate_gc_state);
785 heap->propagate_gc_state_to_all_threads();
786 }
787 }
788
789 void ShenandoahConcurrentGC::op_mark_roots() {
790 _mark.mark_concurrent_roots();
791 }
792
793 void ShenandoahConcurrentGC::op_mark() {
794 _mark.concurrent_mark();
795 }
796
797 void ShenandoahConcurrentGC::op_final_mark() {
798 ShenandoahHeap* const heap = ShenandoahHeap::heap();
799 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
800 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
801
802 if (ShenandoahVerify) {
803 heap->verifier()->verify_roots_no_forwarded(_generation);
804 }
805
806 if (!heap->cancelled_gc()) {
807 _mark.finish_mark();
808 assert(!heap->cancelled_gc(), "STW mark cannot OOM");
809
810 // Notify JVMTI that the tagmap table will need cleaning.
811 JvmtiTagMap::set_needs_cleaning();
812
813 // The collection set is chosen by prepare_regions_and_collection_set(). Additionally, certain parameters have been
814 // established to govern the evacuation efforts that are about to begin. Refer to comments on reserve members in
815 // ShenandoahGeneration and ShenandoahOldGeneration for more detail.
816 _generation->prepare_regions_and_collection_set(true /*concurrent*/);
817
818 // Has to be done after cset selection
819 heap->prepare_concurrent_roots();
820
821 if (!heap->collection_set()->is_empty()) {
822 LogTarget(Debug, gc, cset) lt;
823 if (lt.is_enabled()) {
824 ResourceMark rm;
825 LogStream ls(lt);
826 heap->collection_set()->print_on(&ls);
827 }
828
829 if (ShenandoahVerify) {
830 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_mark_verify);
831 heap->verifier()->verify_before_evacuation(_generation);
832 }
833
834 heap->set_evacuation_in_progress(true);
835 // From here on, we need to update references.
836 heap->set_has_forwarded_objects(true);
837
838 // Arm nmethods/stack for concurrent processing
839 ShenandoahCodeRoots::arm_nmethods();
840 ShenandoahStackWatermark::change_epoch_id();
841
842 } else {
843 if (ShenandoahVerify) {
844 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_mark_verify);
845 if (has_in_place_promotions(heap)) {
846 heap->verifier()->verify_after_concmark_with_promotions(_generation);
847 } else {
848 heap->verifier()->verify_after_concmark(_generation);
849 }
850 }
851 }
852 }
853
854 {
855 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_propagate_gc_state);
856 heap->propagate_gc_state_to_all_threads();
857 }
858 }
859
860 bool ShenandoahConcurrentGC::has_in_place_promotions(ShenandoahHeap* heap) {
861 return heap->mode()->is_generational() && heap->old_generation()->has_in_place_promotions();
862 }
863
864 class ShenandoahConcurrentEvacThreadClosure : public ThreadClosure {
865 private:
866 OopClosure* const _oops;
867 public:
868 explicit ShenandoahConcurrentEvacThreadClosure(OopClosure* oops) : _oops(oops) {}
869
870 void do_thread(Thread* thread) override {
871 JavaThread* const jt = JavaThread::cast(thread);
872 StackWatermarkSet::finish_processing(jt, _oops, StackWatermarkKind::gc);
873 }
874 };
875
876 class ShenandoahConcurrentEvacUpdateThreadTask : public WorkerTask {
877 private:
878 ShenandoahJavaThreadsIterator _java_threads;
879
880 public:
881 explicit ShenandoahConcurrentEvacUpdateThreadTask(uint n_workers) :
882 WorkerTask("Shenandoah Evacuate/Update Concurrent Thread Roots"),
883 _java_threads(ShenandoahPhaseTimings::conc_thread_roots, n_workers) {
884 }
885
886 void work(uint worker_id) override {
887 ShenandoahContextEvacuateUpdateRootsClosure oops_cl;
888 ShenandoahConcurrentEvacThreadClosure thr_cl(&oops_cl);
889 _java_threads.threads_do(&thr_cl, worker_id);
890 }
891 };
892
893 void ShenandoahConcurrentGC::op_thread_roots() {
894 const ShenandoahHeap* const heap = ShenandoahHeap::heap();
895 assert(heap->is_evacuation_in_progress(), "Checked by caller");
896 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_thread_roots);
897 ShenandoahConcurrentEvacUpdateThreadTask task(heap->workers()->active_workers());
898 heap->workers()->run_task(&task);
899 }
900
901 void ShenandoahConcurrentGC::op_weak_refs() {
902 ShenandoahHeap* const heap = ShenandoahHeap::heap();
903 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
904 // Concurrent weak refs processing
905 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_refs);
906 if (heap->gc_cause() == GCCause::_wb_breakpoint) {
907 ShenandoahBreakpoint::at_after_reference_processing_started();
908 }
909 _generation->ref_processor()->process_references(ShenandoahPhaseTimings::conc_weak_refs, heap->workers(), true /* concurrent */);
910 }
911
912 class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
913 private:
914 ShenandoahHeap* const _heap;
915 ShenandoahGeneration* const _generation;
916 ShenandoahMarkingContext* const _mark_context;
917 bool _evac_in_progress;
918 Thread* const _thread;
919
920 public:
921 explicit ShenandoahEvacUpdateCleanupOopStorageRootsClosure(ShenandoahGeneration* generation);
922 void do_oop(oop* p);
923 void do_oop(narrowOop* p);
924 };
925
926 ShenandoahEvacUpdateCleanupOopStorageRootsClosure::ShenandoahEvacUpdateCleanupOopStorageRootsClosure(ShenandoahGeneration* generation) :
927 _heap(ShenandoahHeap::heap()),
928 _generation(generation),
929 _mark_context(ShenandoahHeap::heap()->marking_context()),
930 _evac_in_progress(ShenandoahHeap::heap()->is_evacuation_in_progress()),
931 _thread(Thread::current()) {
932 }
933
934 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
935 const oop obj = RawAccess<>::oop_load(p);
936 if (!CompressedOops::is_null(obj)) {
937 if (!_mark_context->is_marked(obj)) {
938 if (_generation->contains(obj)) {
939 // Note: The obj is dead here. Do not touch it, just clear.
940 ShenandoahHeap::atomic_clear_oop(p, obj);
941 }
942 } else if (_evac_in_progress && _heap->in_collection_set(obj)) {
943 oop resolved = ShenandoahForwarding::get_forwardee(obj);
944 if (resolved == obj) {
945 resolved = _heap->evacuate_object(obj, _thread);
946 }
947 shenandoah_assert_not_in_cset_except(p, resolved, _heap->cancelled_gc());
948 ShenandoahHeap::atomic_update_oop(resolved, p, obj);
949 }
950 }
951 }
952
953 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(narrowOop* p) {
954 ShouldNotReachHere();
955 }
956
957 class ShenandoahIsCLDAliveClosure : public CLDClosure {
958 public:
959 void do_cld(ClassLoaderData* cld) {
960 cld->is_alive();
961 }
962 };
963
964 class ShenandoahIsNMethodAliveClosure: public NMethodClosure {
965 public:
966 void do_nmethod(nmethod* n) {
967 n->is_unloading();
968 }
969 };
970
971 // This task not only evacuates/updates marked weak roots, but also "null"
972 // dead weak roots.
973 class ShenandoahConcurrentWeakRootsEvacUpdateTask : public WorkerTask {
974 private:
975 ShenandoahVMWeakRoots<true /*concurrent*/> _vm_roots;
976
977 // Roots related to concurrent class unloading
978 ShenandoahClassLoaderDataRoots<true /* concurrent */>
979 _cld_roots;
980 ShenandoahConcurrentNMethodIterator _nmethod_itr;
981 ShenandoahGeneration* _generation;
982 ShenandoahPhaseTimings::Phase _phase;
983
984 public:
985 ShenandoahConcurrentWeakRootsEvacUpdateTask(ShenandoahGeneration* generation, ShenandoahPhaseTimings::Phase phase) :
986 WorkerTask("Shenandoah Evacuate/Update Concurrent Weak Roots"),
987 _vm_roots(phase),
988 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
989 _nmethod_itr(ShenandoahCodeRoots::table()),
990 _generation(generation),
991 _phase(phase) {}
992
993 ~ShenandoahConcurrentWeakRootsEvacUpdateTask() {
994 // Notify runtime data structures of potentially dead oops
995 _vm_roots.report_num_dead();
996 }
997
998 void work(uint worker_id) override {
999 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1000 SuspendibleThreadSetJoiner sts_join;
1001 {
1002 // jni_roots and weak_roots are OopStorage backed roots, concurrent iteration
1003 // may race against OopStorage::release() calls.
1004 ShenandoahEvacUpdateCleanupOopStorageRootsClosure cl(_generation);
1005 _vm_roots.oops_do(&cl, worker_id);
1006 }
1007
1008 // If we are going to perform concurrent class unloading later on, we need to
1009 // clean up the weak oops in CLD and determine nmethod's unloading state, so that we
1010 // can clean up immediate garbage sooner.
1011 if (ShenandoahHeap::heap()->unload_classes()) {
1012 // Applies ShenandoahIsCLDAlive closure to CLDs, native barrier will either null the
1013 // CLD's holder or evacuate it.
1014 {
1015 ShenandoahIsCLDAliveClosure is_cld_alive;
1016 _cld_roots.cld_do(&is_cld_alive, worker_id);
1017 }
1018
1019 // Applies ShenandoahIsNMethodAliveClosure to registered nmethods.
1020 // The closure calls nmethod->is_unloading(). The is_unloading
1021 // state is cached, therefore, during concurrent class unloading phase,
1022 // we will not touch the metadata of unloading nmethods
1023 {
1024 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCache, worker_id);
1025 ShenandoahIsNMethodAliveClosure is_nmethod_alive;
1026 _nmethod_itr.nmethods_do(&is_nmethod_alive);
1027 }
1028 }
1029 }
1030 };
1031
1032 void ShenandoahConcurrentGC::op_weak_roots() {
1033 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1034 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
1035 {
1036 // Concurrent weak root processing
1037 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_roots);
1038 ShenandoahConcurrentWeakRootsEvacUpdateTask task(_generation, ShenandoahPhaseTimings::conc_weak_roots);
1039 heap->workers()->run_task(&task);
1040 }
1041
1042 {
1043 // It is possible for mutators executing the load reference barrier to have
1044 // loaded an oop through a weak handle that has since been nulled out by
1045 // weak root processing. Handshaking here forces them to complete the
1046 // barrier before the GC cycle continues and does something that would
1047 // change the evaluation of the barrier (for example, resetting the TAMS
1048 // on trashed regions could make an oop appear to be marked _after_ the
1049 // region has been recycled).
1050 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
1051 heap->rendezvous_threads("Shenandoah Concurrent Weak Roots");
1052 }
1053 }
1054
1055 void ShenandoahConcurrentGC::op_class_unloading() {
1056 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1057 assert (heap->is_concurrent_weak_root_in_progress() &&
1058 heap->unload_classes(),
1059 "Checked by caller");
1060 heap->do_class_unloading();
1061 }
1062
1063 class ShenandoahEvacUpdateCodeCacheClosure : public NMethodClosure {
1064 private:
1065 ShenandoahEvacuateUpdateMetadataClosure _cl;
1066
1067 public:
1068 ShenandoahEvacUpdateCodeCacheClosure() : _cl() {}
1069
1070 void do_nmethod(nmethod* n) {
1071 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(n);
1072 ShenandoahNMethodLocker locker(data->lock());
1073 data->oops_do(&_cl, /* fix_relocations = */ true);
1074 ShenandoahNMethod::disarm_nmethod(n);
1075 }
1076 };
1077
1078 class ShenandoahConcurrentRootsEvacUpdateTask : public WorkerTask {
1079 private:
1080 ShenandoahPhaseTimings::Phase _phase;
1081 ShenandoahVMRoots<true /*concurrent*/> _vm_roots;
1082 ShenandoahClassLoaderDataRoots<true /*concurrent*/>
1083 _cld_roots;
1084 ShenandoahConcurrentNMethodIterator _nmethod_itr;
1085
1086 public:
1087 ShenandoahConcurrentRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1088 WorkerTask("Shenandoah Evacuate/Update Concurrent Strong Roots"),
1089 _phase(phase),
1090 _vm_roots(phase),
1091 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
1092 _nmethod_itr(ShenandoahCodeRoots::table()) {}
1093
1094 void work(uint worker_id) {
1095 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1096 {
1097 {
1098 // vm_roots and weak_roots are OopStorage backed roots, concurrent iteration
1099 // may race against OopStorage::release() calls.
1100 ShenandoahContextEvacuateUpdateRootsClosure cl;
1101 _vm_roots.oops_do<ShenandoahContextEvacuateUpdateRootsClosure>(&cl, worker_id);
1102 }
1103
1104 {
1105 ShenandoahEvacuateUpdateMetadataClosure cl;
1106 CLDToOopClosure clds(&cl, ClassLoaderData::_claim_strong);
1107 _cld_roots.cld_do(&clds, worker_id);
1108 }
1109 }
1110
1111 if (!ShenandoahHeap::heap()->unload_classes()) {
1112 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCache, worker_id);
1113 ShenandoahEvacUpdateCodeCacheClosure cl;
1114 _nmethod_itr.nmethods_do(&cl);
1115 }
1116 }
1117 };
1118
1119 void ShenandoahConcurrentGC::op_strong_roots() {
1120 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1121 assert(heap->is_concurrent_strong_root_in_progress(), "Checked by caller");
1122 ShenandoahConcurrentRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_strong_roots);
1123 heap->workers()->run_task(&task);
1124 heap->set_concurrent_strong_root_in_progress(false);
1125 }
1126
1127 void ShenandoahConcurrentGC::op_cleanup_early() {
1128 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1129 ShenandoahWorkerPolicy::calc_workers_for_conc_cleanup(),
1130 "cleanup early.");
1131 ShenandoahHeap::heap()->recycle_trash();
1132 }
1133
1134 void ShenandoahConcurrentGC::op_evacuate() {
1135 ShenandoahHeap::heap()->evacuate_collection_set(_generation, true /*concurrent*/);
1136 }
1137
1138 void ShenandoahConcurrentGC::op_init_update_refs() {
1139 if (ShenandoahVerify) {
1140 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1141 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::init_update_refs_verify);
1142 heap->verifier()->verify_before_update_refs(_generation);
1143 }
1144 }
1145
1146 void ShenandoahConcurrentGC::op_update_refs() {
1147 ShenandoahHeap::heap()->update_heap_references(_generation, true /*concurrent*/);
1148 }
1149
1150 class ShenandoahUpdateThreadHandshakeClosure : public HandshakeClosure {
1151 private:
1152 // This closure runs when thread is stopped for handshake, which means
1153 // we can use non-concurrent closure here, as long as it only updates
1154 // locations modified by the thread itself, i.e. stack locations.
1155 ShenandoahNonConcUpdateRefsClosure _cl;
1156 public:
1157 ShenandoahUpdateThreadHandshakeClosure();
1158 void do_thread(Thread* thread) override;
1159 };
1160
1161 ShenandoahUpdateThreadHandshakeClosure::ShenandoahUpdateThreadHandshakeClosure() :
1162 HandshakeClosure("Shenandoah Update Thread Roots") {
1163 }
1164
1165 void ShenandoahUpdateThreadHandshakeClosure::do_thread(Thread* thread) {
1166 if (thread->is_Java_thread()) {
1167 JavaThread* jt = JavaThread::cast(thread);
1168 ResourceMark rm;
1169 jt->oops_do(&_cl, nullptr);
1170 }
1171 }
1172
1173 class ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers final : public HandshakeClosure {
1174 // When Shenandoah is marking the old generation, it is possible for the SATB barrier
1175 // to pick up overwritten pointers that point into a cset region. If these pointers
1176 // are accessed by mark threads, they will crash. Once update refs has completed, it is
1177 // no longer possible for a mutator thread to overwrite a pointer into a cset region.
1178 //
1179 // Therefore, at the end of update refs, we use this closure to update the thread roots
1180 // and 'complete' all the thread local SATB buffers. Completing these will filter out
1181 // anything that has already been marked or anything that points to a region which is
1182 // not old. We do not need to worry about ABA situations where a region may become old
1183 // after the pointer is enqueued but before it is filtered. There are only two ways a
1184 // region may become old:
1185 // 1. The region is promoted in place. This is safe because such regions will never
1186 // be in the collection set. If this happens, the pointer will be preserved, essentially
1187 // becoming part of the old snapshot.
1188 // 2. The region is allocated during evacuation of old. This is also not a concern because
1189 // we haven't yet finished marking old so no mixed evacuations will happen.
1190 ShenandoahUpdateThreadHandshakeClosure _update_roots;
1191 ShenandoahFlushSATB _flush_all_satb;
1192
1193 public:
1194 ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers() :
1195 HandshakeClosure("Shenandoah Update Thread Roots and Flush SATB"),
1196 _flush_all_satb(ShenandoahBarrierSet::satb_mark_queue_set()) {
1197 assert(ShenandoahBarrierSet::satb_mark_queue_set().get_filter_out_young(),
1198 "Should be filtering pointers outside of old during old marking");
1199 }
1200
1201 void do_thread(Thread* thread) override {
1202 _update_roots.do_thread(thread);
1203 _flush_all_satb.do_thread(thread);
1204 }
1205 };
1206
1207 void ShenandoahConcurrentGC::op_update_thread_roots() {
1208 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1209 if (heap->is_concurrent_old_mark_in_progress()) {
1210 ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers cl;
1211 Handshake::execute(&cl);
1212 } else {
1213 ShenandoahUpdateThreadHandshakeClosure cl;
1214 Handshake::execute(&cl);
1215 }
1216 }
1217
1218 void ShenandoahConcurrentGC::op_final_update_refs() {
1219 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1220 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1221 assert(!heap->_update_refs_iterator.has_next(), "Should have finished update references");
1222
1223 heap->finish_concurrent_roots();
1224
1225 // Clear cancelled GC, if set. On cancellation path, the block before would handle
1226 // everything.
1227 if (heap->cancelled_gc()) {
1228 heap->clear_cancelled_gc();
1229 }
1230
1231 // Has to be done before cset is clear
1232 if (ShenandoahVerify) {
1233 heap->verifier()->verify_roots_in_to_space(_generation);
1234 }
1235
1236 // If we are running in generational mode, this will also age active regions that
1237 // haven't been used for allocation.
1238 heap->update_heap_region_states(true /*concurrent*/);
1239
1240 heap->set_update_refs_in_progress(false);
1241 heap->set_has_forwarded_objects(false);
1242
1243 if (ShenandoahVerify) {
1244 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_update_refs_verify);
1245 heap->verifier()->verify_after_update_refs(_generation);
1246 }
1247
1248 if (VerifyAfterGC) {
1249 Universe::verify();
1250 }
1251
1252 heap->rebuild_free_set(true /*concurrent*/);
1253 _generation->heuristics()->start_idle_span();
1254
1255 {
1256 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_propagate_gc_state);
1257 heap->propagate_gc_state_to_all_threads();
1258 }
1259 }
1260
1261 void ShenandoahConcurrentGC::entry_final_roots() {
1262 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1263 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
1264 SHENANDOAH_EVENT_MESSAGE(msg, _generation->type(), "Concurrent final roots", "");
1265 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_final_roots);
1266 EventMark em("%s", msg);
1267
1268 heap->concurrent_final_roots();
1269 }
1270
1271 void ShenandoahConcurrentGC::op_verify_final() {
1272 assert(ShenandoahVerify, "Should have been checked before");
1273 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1274 heap->verifier()->verify_after_gc(_generation);
1275 }
1276
1277 void ShenandoahConcurrentGC::op_cleanup_complete() {
1278 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1279 ShenandoahWorkerPolicy::calc_workers_for_conc_cleanup(),
1280 "cleanup complete.");
1281 ShenandoahHeap::heap()->recycle_trash();
1282 }
1283
1284 void ShenandoahConcurrentGC::op_reset_after_collect() {
1285 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1286 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
1287 "reset after collection.");
1288
1289 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1290 if (heap->mode()->is_generational()) {
1291 // If we are in the midst of an old gc bootstrap or an old marking, we want to leave the mark bit map of
1292 // the young generation intact. In particular, reference processing in the old generation may potentially
1293 // need the reachability of a young generation referent of a Reference object in the old generation.
1294 if (!_do_old_gc_bootstrap && !heap->is_concurrent_old_mark_in_progress()) {
1295 heap->young_generation()->reset_mark_bitmap<false>();
1296 }
1297 } else {
1298 _generation->reset_mark_bitmap<false>();
1299 }
1300 }
1301
1302 bool ShenandoahConcurrentGC::check_cancellation_and_abort(ShenandoahDegenPoint point) {
1303 if (ShenandoahHeap::heap()->cancelled_gc()) {
1304 _degen_point = point;
1305 return true;
1306 }
1307 return false;
1308 }