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