1 /*
2 * Copyright (c) 2024, 2025, 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/shenandoahFreeSet.hpp"
36 #include "gc/shenandoah/shenandoahGeneration.hpp"
37 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
38 #include "gc/shenandoah/shenandoahLock.hpp"
39 #include "gc/shenandoah/shenandoahMark.inline.hpp"
40 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
41 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
42 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
43 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
44 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
45 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
46 #include "gc/shenandoah/shenandoahUtils.hpp"
47 #include "gc/shenandoah/shenandoahVerifier.hpp"
48 #include "gc/shenandoah/shenandoahVMOperations.hpp"
49 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
50 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
51 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
52 #include "memory/allocation.hpp"
53 #include "prims/jvmtiTagMap.hpp"
54 #include "runtime/vmThread.hpp"
55 #include "utilities/events.hpp"
56
57 // Breakpoint support
58 class ShenandoahBreakpointGCScope : public StackObj {
59 private:
60 const GCCause::Cause _cause;
61 public:
62 ShenandoahBreakpointGCScope(GCCause::Cause cause) : _cause(cause) {
63 if (cause == GCCause::_wb_breakpoint) {
64 ShenandoahBreakpoint::start_gc();
65 ShenandoahBreakpoint::at_before_gc();
66 }
67 }
68
69 ~ShenandoahBreakpointGCScope() {
70 if (_cause == GCCause::_wb_breakpoint) {
71 ShenandoahBreakpoint::at_after_gc();
72 }
73 }
74 };
75
76 class ShenandoahBreakpointMarkScope : public StackObj {
77 private:
78 const GCCause::Cause _cause;
79 public:
80 ShenandoahBreakpointMarkScope(GCCause::Cause cause) : _cause(cause) {
81 if (_cause == GCCause::_wb_breakpoint) {
82 ShenandoahBreakpoint::at_after_marking_started();
83 }
84 }
85
86 ~ShenandoahBreakpointMarkScope() {
87 if (_cause == GCCause::_wb_breakpoint) {
88 ShenandoahBreakpoint::at_before_marking_completed();
89 }
90 }
91 };
92
93 ShenandoahConcurrentGC::ShenandoahConcurrentGC(ShenandoahGeneration* generation, bool do_old_gc_bootstrap) :
94 ShenandoahGC(generation),
95 _mark(generation),
96 _degen_point(ShenandoahDegenPoint::_degenerated_unset),
97 _abbreviated(false),
98 _do_old_gc_bootstrap(do_old_gc_bootstrap) {
99 }
100
101 ShenandoahGC::ShenandoahDegenPoint ShenandoahConcurrentGC::degen_point() const {
102 return _degen_point;
103 }
104
105 void ShenandoahConcurrentGC::entry_concurrent_update_refs_prepare(ShenandoahHeap* const heap) {
106 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
107 const char* msg = conc_init_update_refs_event_message();
108 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs_prepare);
109 EventMark em("%s", msg);
110
111 // Evacuation is complete, retire gc labs and change gc state
112 heap->concurrent_prepare_for_update_refs();
113 }
114
115 bool ShenandoahConcurrentGC::collect(GCCause::Cause cause) {
116 ShenandoahHeap* const heap = ShenandoahHeap::heap();
117 _generation->ref_processor()->set_soft_reference_policy(
118 GCCause::should_clear_all_soft_refs(cause));
119
120 ShenandoahBreakpointGCScope breakpoint_gc_scope(cause);
121
122 // Reset for upcoming marking
123 entry_reset();
124
125 // Start initial mark under STW
126 vmop_entry_init_mark();
127
128 {
129 ShenandoahBreakpointMarkScope breakpoint_mark_scope(cause);
130
131 // Reset task queue stats here, rather than in mark_concurrent_roots,
132 // because remembered set scan will `push` oops into the queues and
133 // resetting after this happens will lose those counts.
134 TASKQUEUE_STATS_ONLY(_mark.task_queues()->reset_taskqueue_stats());
135
136 // Concurrent remembered set scanning
137 entry_scan_remembered_set();
138
139 // Concurrent mark roots
140 entry_mark_roots();
141 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_roots)) {
142 return false;
143 }
144
145 // Continue concurrent mark
146 entry_mark();
147 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) {
148 return false;
149 }
150 }
151
152 // Complete marking under STW, and start evacuation
153 vmop_entry_final_mark();
154
155 // If the GC was cancelled before final mark, nothing happens on the safepoint. We are still
156 // in the marking phase and must resume the degenerated cycle from there. If the GC was cancelled
157 // after final mark, then we've entered the evacuation phase and must resume the degenerated cycle
158 // from that phase.
159 if (_generation->is_concurrent_mark_in_progress()) {
160 bool cancelled = check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark);
161 assert(cancelled, "GC must have been cancelled between concurrent and final mark");
162 return false;
163 }
164
165 assert(heap->is_concurrent_weak_root_in_progress(), "Must be doing weak roots now");
166
167 // Concurrent stack processing
168 if (heap->is_evacuation_in_progress()) {
169 entry_thread_roots();
170 }
171
172 // Process weak roots that might still point to regions that would be broken by cleanup.
173 // We cannot recycle regions because weak roots need to know what is marked in trashed regions.
174 entry_weak_refs();
175 entry_weak_roots();
176
177 // Perform concurrent class unloading before any regions get recycled. Class unloading may
178 // need to inspect unmarked objects in trashed regions.
179 if (heap->unload_classes()) {
180 entry_class_unloading();
181 }
182
183 // Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
184 // the space. This would be the last action if there is nothing to evacuate. Note that
185 // we will not age young-gen objects in the case that we skip evacuation.
186 entry_cleanup_early();
187
188 heap->free_set()->log_status_under_lock();
189
190 // Processing strong roots
191 // This may be skipped if there is nothing to update/evacuate.
192 // If so, strong_root_in_progress would be unset.
193 if (heap->is_concurrent_strong_root_in_progress()) {
194 entry_strong_roots();
195 }
196
197 // Continue the cycle with evacuation and optional update-refs.
198 // This may be skipped if there is nothing to evacuate.
199 // If so, evac_in_progress would be unset by collection set preparation code.
200 if (heap->is_evacuation_in_progress()) {
201 // Concurrently evacuate
202 entry_evacuate();
203 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) {
204 return false;
205 }
206
207 // Perform update-refs phase.
208 entry_concurrent_update_refs_prepare(heap);
209 if (ShenandoahVerify) {
210 vmop_entry_init_update_refs();
211 }
212
213 entry_update_refs();
214 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_update_refs)) {
215 return false;
216 }
217
218 // Concurrent update thread roots
219 entry_update_thread_roots();
220 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_update_refs)) {
221 return false;
222 }
223
224 vmop_entry_final_update_refs();
225
226 // Update references freed up collection set, kick the cleanup to reclaim the space.
227 entry_cleanup_complete();
228 } else {
229 _abbreviated = true;
230 if (!entry_final_roots()) {
231 assert(_degen_point != _degenerated_unset, "Need to know where to start degenerated cycle");
232 return false;
233 }
234
235 if (VerifyAfterGC) {
236 vmop_entry_verify_final_roots();
237 }
238 }
239
240 // We defer generation resizing actions until after cset regions have been recycled. We do this even following an
241 // abbreviated cycle.
242 if (heap->mode()->is_generational()) {
243 ShenandoahGenerationalHeap::heap()->complete_concurrent_cycle();
244 }
245
246 // Instead of always resetting immediately before the start of a new GC, we can often reset at the end of the
247 // previous GC. This allows us to start the next GC cycle more quickly after a trigger condition is detected,
248 // reducing the likelihood that GC will degenerate.
249 entry_reset_after_collect();
250
251 return true;
252 }
253
254 bool ShenandoahConcurrentGC::complete_abbreviated_cycle() {
255 shenandoah_assert_generational();
256
257 ShenandoahGenerationalHeap* const heap = ShenandoahGenerationalHeap::heap();
258
259 // We chose not to evacuate because we found sufficient immediate garbage.
260 // However, there may still be regions to promote in place, so do that now.
261 if (heap->old_generation()->has_in_place_promotions()) {
262 entry_promote_in_place();
263
264 // If the promote-in-place operation was cancelled, we can have the degenerated
265 // cycle complete the operation. It will see that no evacuations are in progress,
266 // and that there are regions wanting promotion. The risk with not handling the
267 // cancellation would be failing to restore top for these regions and leaving
268 // them unable to serve allocations for the old generation.This will leave the weak
269 // roots flag set (the degenerated cycle will unset it).
270 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) {
271 return false;
272 }
273 }
274
275 // At this point, the cycle is effectively complete. If the cycle has been cancelled here,
276 // the control thread will detect it on its next iteration and run a degenerated young cycle.
277 if (!_generation->is_old()) {
278 heap->update_region_ages(_generation->complete_marking_context());
279 }
280
281 return true;
282 }
283
284 void ShenandoahConcurrentGC::vmop_entry_init_mark() {
285 ShenandoahHeap* const heap = ShenandoahHeap::heap();
286 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
287 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_mark_gross);
288
289 heap->try_inject_alloc_failure();
290 VM_ShenandoahInitMark op(this);
291 VMThread::execute(&op); // jump to entry_init_mark() under safepoint
292 }
293
294 void ShenandoahConcurrentGC::vmop_entry_final_mark() {
295 ShenandoahHeap* const heap = ShenandoahHeap::heap();
296 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
297 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_gross);
298
299 heap->try_inject_alloc_failure();
300 VM_ShenandoahFinalMarkStartEvac op(this);
301 VMThread::execute(&op); // jump to entry_final_mark under safepoint
302 }
303
304 void ShenandoahConcurrentGC::vmop_entry_init_update_refs() {
305 ShenandoahHeap* const heap = ShenandoahHeap::heap();
306 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
307 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_update_refs_gross);
308
309 heap->try_inject_alloc_failure();
310 VM_ShenandoahInitUpdateRefs op(this);
311 VMThread::execute(&op);
312 }
313
314 void ShenandoahConcurrentGC::vmop_entry_final_update_refs() {
315 ShenandoahHeap* const heap = ShenandoahHeap::heap();
316 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
317 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_gross);
318
319 heap->try_inject_alloc_failure();
320 VM_ShenandoahFinalUpdateRefs op(this);
321 VMThread::execute(&op);
322 }
323
324 void ShenandoahConcurrentGC::vmop_entry_verify_final_roots() {
325 ShenandoahHeap* const heap = ShenandoahHeap::heap();
326 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
327 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_roots_gross);
328
329 // This phase does not use workers, no need for setup
330 heap->try_inject_alloc_failure();
331 VM_ShenandoahFinalRoots op(this);
332 VMThread::execute(&op);
333 }
334
335 void ShenandoahConcurrentGC::entry_init_mark() {
336 const char* msg = init_mark_event_message();
337 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_mark);
338 EventMark em("%s", msg);
339
340 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
341 ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
342 "init marking");
343
344 op_init_mark();
345 }
346
347 void ShenandoahConcurrentGC::entry_final_mark() {
348 const char* msg = final_mark_event_message();
349 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_mark);
350 EventMark em("%s", msg);
351
352 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
353 ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
354 "final marking");
355
356 op_final_mark();
357 }
358
359 void ShenandoahConcurrentGC::entry_init_update_refs() {
360 static const char* msg = "Pause Init Update Refs";
361 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_update_refs);
362 EventMark em("%s", msg);
363
364 // No workers used in this phase, no setup required
365 op_init_update_refs();
366 }
367
368 void ShenandoahConcurrentGC::entry_final_update_refs() {
369 static const char* msg = "Pause Final Update Refs";
370 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_update_refs);
371 EventMark em("%s", msg);
372
373 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
374 ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
375 "final reference update");
376
377 op_final_update_refs();
378 }
379
380 void ShenandoahConcurrentGC::entry_verify_final_roots() {
381 const char* msg = verify_final_roots_event_message();
382 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_roots);
383 EventMark em("%s", msg);
384
385 op_verify_final_roots();
386 }
387
388 void ShenandoahConcurrentGC::entry_reset() {
389 ShenandoahHeap* const heap = ShenandoahHeap::heap();
390 heap->try_inject_alloc_failure();
391
392 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
393 {
394 const char* msg = conc_reset_event_message();
395 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset);
396 EventMark em("%s", msg);
397
398 ShenandoahWorkerScope scope(heap->workers(),
399 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
400 msg);
401 op_reset();
402 }
403 }
404
405 void ShenandoahConcurrentGC::entry_scan_remembered_set() {
406 if (_generation->is_young()) {
407 ShenandoahHeap* const heap = ShenandoahHeap::heap();
408 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
409 const char* msg = "Concurrent remembered set scanning";
410 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::init_scan_rset);
411 EventMark em("%s", msg);
412
413 ShenandoahWorkerScope scope(heap->workers(),
414 ShenandoahWorkerPolicy::calc_workers_for_rs_scanning(),
415 msg);
416
417 heap->try_inject_alloc_failure();
418 _generation->scan_remembered_set(true /* is_concurrent */);
419 }
420 }
421
422 void ShenandoahConcurrentGC::entry_mark_roots() {
423 ShenandoahHeap* const heap = ShenandoahHeap::heap();
424 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
425 const char* msg = "Concurrent marking roots";
426 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark_roots);
427 EventMark em("%s", msg);
428
429 ShenandoahWorkerScope scope(heap->workers(),
430 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
431 "concurrent marking roots");
432
433 heap->try_inject_alloc_failure();
434 op_mark_roots();
435 }
436
437 void ShenandoahConcurrentGC::entry_mark() {
438 ShenandoahHeap* const heap = ShenandoahHeap::heap();
439 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
440 const char* msg = conc_mark_event_message();
441 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark);
442 EventMark em("%s", msg);
443
444 ShenandoahWorkerScope scope(heap->workers(),
445 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
446 "concurrent marking");
447
448 heap->try_inject_alloc_failure();
449 op_mark();
450 }
451
452 void ShenandoahConcurrentGC::entry_thread_roots() {
453 ShenandoahHeap* const heap = ShenandoahHeap::heap();
454 static const char* msg = "Concurrent thread roots";
455 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_thread_roots);
456 EventMark em("%s", msg);
457
458 ShenandoahWorkerScope scope(heap->workers(),
459 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
460 msg);
461
462 heap->try_inject_alloc_failure();
463 op_thread_roots();
464 }
465
466 void ShenandoahConcurrentGC::entry_weak_refs() {
467 ShenandoahHeap* const heap = ShenandoahHeap::heap();
468 const char* msg = conc_weak_refs_event_message();
469 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_refs);
470 EventMark em("%s", msg);
471
472 ShenandoahWorkerScope scope(heap->workers(),
473 ShenandoahWorkerPolicy::calc_workers_for_conc_refs_processing(),
474 "concurrent weak references");
475
476 heap->try_inject_alloc_failure();
477 op_weak_refs();
478 }
479
480 void ShenandoahConcurrentGC::entry_weak_roots() {
481 ShenandoahHeap* const heap = ShenandoahHeap::heap();
482 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
483 const char* msg = conc_weak_roots_event_message();
484 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_roots);
485 EventMark em("%s", msg);
486
487 ShenandoahWorkerScope scope(heap->workers(),
488 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
489 "concurrent weak root");
490
491 heap->try_inject_alloc_failure();
492 op_weak_roots();
493 }
494
495 void ShenandoahConcurrentGC::entry_class_unloading() {
496 ShenandoahHeap* const heap = ShenandoahHeap::heap();
497 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
498 static const char* msg = "Concurrent class unloading";
499 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_class_unload);
500 EventMark em("%s", msg);
501
502 ShenandoahWorkerScope scope(heap->workers(),
503 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
504 "concurrent class unloading");
505
506 heap->try_inject_alloc_failure();
507 op_class_unloading();
508 }
509
510 void ShenandoahConcurrentGC::entry_strong_roots() {
511 ShenandoahHeap* const heap = ShenandoahHeap::heap();
512 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
513 static const char* msg = "Concurrent strong roots";
514 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_strong_roots);
515 EventMark em("%s", msg);
516
517 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_strong_roots);
518
519 ShenandoahWorkerScope scope(heap->workers(),
520 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
521 "concurrent strong root");
522
523 heap->try_inject_alloc_failure();
524 op_strong_roots();
525 }
526
527 void ShenandoahConcurrentGC::entry_cleanup_early() {
528 ShenandoahHeap* const heap = ShenandoahHeap::heap();
529 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
530 const char* msg = conc_cleanup_event_message();
531 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_early, true /* log_heap_usage */);
532 EventMark em("%s", msg);
533
534 // This phase does not use workers, no need for setup
535 heap->try_inject_alloc_failure();
536 op_cleanup_early();
537 if (!heap->is_evacuation_in_progress()) {
538 // This is an abbreviated cycle. Rebuild the freeset in order to establish reserves for the next GC cycle. Doing
539 // the rebuild ASAP also expedites availability of immediate trash, reducing the likelihood that we will degenerate
540 // during promote-in-place processing.
541 heap->rebuild_free_set(true /*concurrent*/);
542 }
543 }
544
545 void ShenandoahConcurrentGC::entry_evacuate() {
546 ShenandoahHeap* const heap = ShenandoahHeap::heap();
547 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
548
549 static const char* msg = "Concurrent evacuation";
550 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_evac);
551 EventMark em("%s", msg);
552
553 ShenandoahWorkerScope scope(heap->workers(),
554 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
555 "concurrent evacuation");
556
557 heap->try_inject_alloc_failure();
558 op_evacuate();
559 }
560
561 void ShenandoahConcurrentGC::entry_promote_in_place() const {
562 shenandoah_assert_generational();
563
564 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::promote_in_place);
565 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::promote_in_place);
566 EventMark em("%s", "Promote in place");
567
568 ShenandoahGenerationalHeap::heap()->promote_regions_in_place(_generation, true);
569 }
570
571 void ShenandoahConcurrentGC::entry_update_thread_roots() {
572 ShenandoahHeap* const heap = ShenandoahHeap::heap();
573 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
574
575 static const char* msg = "Concurrent update thread roots";
576 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_thread_roots);
577 EventMark em("%s", msg);
578
579 // No workers used in this phase, no setup required
580 heap->try_inject_alloc_failure();
581 op_update_thread_roots();
582 }
583
584 void ShenandoahConcurrentGC::entry_update_refs() {
585 ShenandoahHeap* const heap = ShenandoahHeap::heap();
586 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
587 static const char* msg = "Concurrent update references";
588 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs);
589 EventMark em("%s", msg);
590
591 ShenandoahWorkerScope scope(heap->workers(),
592 ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
593 "concurrent reference update");
594
595 heap->try_inject_alloc_failure();
596 op_update_refs();
597 }
598
599 void ShenandoahConcurrentGC::entry_cleanup_complete() {
600 ShenandoahHeap* const heap = ShenandoahHeap::heap();
601 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
602 const char* msg = conc_cleanup_event_message();
603 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_complete, true /* log_heap_usage */);
604 EventMark em("%s", msg);
605
606 // This phase does not use workers, no need for setup
607 heap->try_inject_alloc_failure();
608 op_cleanup_complete();
609 }
610
611 void ShenandoahConcurrentGC::entry_reset_after_collect() {
612 ShenandoahHeap* const heap = ShenandoahHeap::heap();
613 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
614 const char* msg = conc_reset_after_collect_event_message();
615 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset_after_collect);
616 EventMark em("%s", msg);
617
618 op_reset_after_collect();
619 }
620
621 void ShenandoahConcurrentGC::op_reset() {
622 ShenandoahHeap* const heap = ShenandoahHeap::heap();
623
624 // If it is old GC bootstrap cycle, always clear bitmap for global gen
625 // to ensure bitmap for old gen is clear for old GC cycle after this.
626 if (_do_old_gc_bootstrap) {
627 assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot reset old without making it parsable");
628 heap->global_generation()->prepare_gc();
629 } else {
630 _generation->prepare_gc();
631 }
632
633 if (heap->mode()->is_generational()) {
634 heap->old_generation()->card_scan()->mark_read_table_as_clean();
635 }
636 }
637
638 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
639 private:
640 ShenandoahMarkingContext* const _ctx;
641 public:
642 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
643
644 void heap_region_do(ShenandoahHeapRegion* r) {
645 assert(!r->has_live(), "Region %zu should have no live data", r->index());
646 if (r->is_active()) {
647 // Check if region needs updating its TAMS. We have updated it already during concurrent
648 // reset, so it is very likely we don't need to do another write here. Since most regions
649 // are not "active", this path is relatively rare.
650 if (_ctx->top_at_mark_start(r) != r->top()) {
651 _ctx->capture_top_at_mark_start(r);
652 }
653 } else {
654 assert(_ctx->top_at_mark_start(r) == r->top(),
655 "Region %zu should already have correct TAMS", r->index());
656 }
657 }
658
659 bool is_thread_safe() { return true; }
660 };
661
662 void ShenandoahConcurrentGC::start_mark() {
663 _mark.start_mark();
664 }
665
666 void ShenandoahConcurrentGC::op_init_mark() {
667 ShenandoahHeap* const heap = ShenandoahHeap::heap();
668 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
669 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
670
671 assert(_generation->is_bitmap_clear(), "need clear marking bitmap");
672 assert(!_generation->is_mark_complete(), "should not be complete");
673 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
674
675 if (heap->mode()->is_generational()) {
676 if (_generation->is_global()) {
677 heap->old_generation()->cancel_gc();
678 }
679
680 {
681 // After we swap card table below, the write-table is all clean, and the read table holds
682 // cards dirty prior to the start of GC. Young and bootstrap collection will update
683 // the write card table as a side effect of remembered set scanning. Global collection will
684 // update the card table as a side effect of global marking of old objects.
685 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_swap_rset);
686 _generation->swap_card_tables();
687 }
688 }
689
690 if (ShenandoahVerify) {
691 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::init_mark_verify);
692 heap->verifier()->verify_before_concmark(_generation);
693 }
694
695 if (VerifyBeforeGC) {
696 Universe::verify();
697 }
698
699 _generation->set_concurrent_mark_in_progress(true);
700
701 start_mark();
702
703 if (_do_old_gc_bootstrap) {
704 shenandoah_assert_generational();
705 // Update region state for both young and old regions
706 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
707 ShenandoahInitMarkUpdateRegionStateClosure cl;
708 heap->parallel_heap_region_iterate(&cl);
709 heap->old_generation()->ref_processor()->reset_thread_locals();
710 } else {
711 // Update region state for only young regions
712 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
713 ShenandoahInitMarkUpdateRegionStateClosure cl;
714 _generation->parallel_heap_region_iterate(&cl);
715 }
716
717 // Weak reference processing
718 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
719 rp->reset_thread_locals();
720
721 // Make above changes visible to worker threads
722 OrderAccess::fence();
723
724 // Arm nmethods for concurrent mark
725 ShenandoahCodeRoots::arm_nmethods_for_mark();
726
727 ShenandoahStackWatermark::change_epoch_id();
728
729 {
730 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_propagate_gc_state);
731 heap->propagate_gc_state_to_all_threads();
732 }
733 }
734
735 void ShenandoahConcurrentGC::op_mark_roots() {
736 _mark.mark_concurrent_roots();
737 }
738
739 void ShenandoahConcurrentGC::op_mark() {
740 _mark.concurrent_mark();
741 if (ShenandoahDelayGC > 0) {
742 os::naked_sleep(ShenandoahDelayGC);
743 }
744 }
745
746 void ShenandoahConcurrentGC::op_final_mark() {
747 ShenandoahHeap* const heap = ShenandoahHeap::heap();
748 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
749 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
750
751 if (ShenandoahVerify) {
752 heap->verifier()->verify_roots_no_forwarded(_generation);
753 }
754
755 if (!heap->cancelled_gc()) {
756 _mark.finish_mark();
757 assert(!heap->cancelled_gc(), "STW mark cannot OOM");
758
759 // Notify JVMTI that the tagmap table will need cleaning.
760 JvmtiTagMap::set_needs_cleaning();
761
762 // The collection set is chosen by prepare_regions_and_collection_set(). Additionally, certain parameters have been
763 // established to govern the evacuation efforts that are about to begin. Refer to comments on reserve members in
764 // ShenandoahGeneration and ShenandoahOldGeneration for more detail.
765 _generation->prepare_regions_and_collection_set(true /*concurrent*/);
766
767 // Has to be done after cset selection
768 heap->prepare_concurrent_roots();
769
770 if (!heap->collection_set()->is_empty()) {
771 LogTarget(Debug, gc, cset) lt;
772 if (lt.is_enabled()) {
773 ResourceMark rm;
774 LogStream ls(lt);
775 heap->collection_set()->print_on(&ls);
776 }
777
778 if (ShenandoahVerify) {
779 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_mark_verify);
780 heap->verifier()->verify_before_evacuation(_generation);
781 }
782
783 heap->set_evacuation_in_progress(true);
784 // From here on, we need to update references.
785 heap->set_has_forwarded_objects(true);
786
787 // Arm nmethods/stack for concurrent processing
788 ShenandoahCodeRoots::arm_nmethods_for_evac();
789 ShenandoahStackWatermark::change_epoch_id();
790
791 } else {
792 if (ShenandoahVerify) {
793 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_mark_verify);
794 if (has_in_place_promotions(heap)) {
795 heap->verifier()->verify_after_concmark_with_promotions(_generation);
796 } else {
797 heap->verifier()->verify_after_concmark(_generation);
798 }
799 }
800 }
801 }
802
803 {
804 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_propagate_gc_state);
805 heap->propagate_gc_state_to_all_threads();
806 }
807 }
808
809 bool ShenandoahConcurrentGC::has_in_place_promotions(ShenandoahHeap* heap) {
810 return heap->mode()->is_generational() && heap->old_generation()->has_in_place_promotions();
811 }
812
813 class ShenandoahConcurrentEvacThreadClosure : public ThreadClosure {
814 private:
815 OopClosure* const _oops;
816 public:
817 explicit ShenandoahConcurrentEvacThreadClosure(OopClosure* oops) : _oops(oops) {}
818
819 void do_thread(Thread* thread) override {
820 JavaThread* const jt = JavaThread::cast(thread);
821 StackWatermarkSet::finish_processing(jt, _oops, StackWatermarkKind::gc);
822 }
823 };
824
825 class ShenandoahConcurrentEvacUpdateThreadTask : public WorkerTask {
826 private:
827 ShenandoahJavaThreadsIterator _java_threads;
828
829 public:
830 explicit ShenandoahConcurrentEvacUpdateThreadTask(uint n_workers) :
831 WorkerTask("Shenandoah Evacuate/Update Concurrent Thread Roots"),
832 _java_threads(ShenandoahPhaseTimings::conc_thread_roots, n_workers) {
833 }
834
835 void work(uint worker_id) override {
836 // ShenandoahEvacOOMScope has to be setup by ShenandoahContextEvacuateUpdateRootsClosure.
837 // Otherwise, may deadlock with watermark lock
838 ShenandoahContextEvacuateUpdateRootsClosure oops_cl;
839 ShenandoahConcurrentEvacThreadClosure thr_cl(&oops_cl);
840 _java_threads.threads_do(&thr_cl, worker_id);
841 }
842 };
843
844 void ShenandoahConcurrentGC::op_thread_roots() {
845 const ShenandoahHeap* const heap = ShenandoahHeap::heap();
846 assert(heap->is_evacuation_in_progress(), "Checked by caller");
847 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_thread_roots);
848 ShenandoahConcurrentEvacUpdateThreadTask task(heap->workers()->active_workers());
849 heap->workers()->run_task(&task);
850 }
851
852 void ShenandoahConcurrentGC::op_weak_refs() {
853 ShenandoahHeap* const heap = ShenandoahHeap::heap();
854 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
855 // Concurrent weak refs processing
856 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_refs);
857 if (heap->gc_cause() == GCCause::_wb_breakpoint) {
858 ShenandoahBreakpoint::at_after_reference_processing_started();
859 }
860 _generation->ref_processor()->process_references(ShenandoahPhaseTimings::conc_weak_refs, heap->workers(), true /* concurrent */);
861 }
862
863 class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
864 private:
865 ShenandoahHeap* const _heap;
866 ShenandoahGeneration* const _generation;
867 ShenandoahMarkingContext* const _mark_context;
868 bool _evac_in_progress;
869 Thread* const _thread;
870
871 public:
872 explicit ShenandoahEvacUpdateCleanupOopStorageRootsClosure(ShenandoahGeneration* generation);
873 void do_oop(oop* p);
874 void do_oop(narrowOop* p);
875 };
876
877 ShenandoahEvacUpdateCleanupOopStorageRootsClosure::ShenandoahEvacUpdateCleanupOopStorageRootsClosure(ShenandoahGeneration* generation) :
878 _heap(ShenandoahHeap::heap()),
879 _generation(generation),
880 _mark_context(ShenandoahHeap::heap()->marking_context()),
881 _evac_in_progress(ShenandoahHeap::heap()->is_evacuation_in_progress()),
882 _thread(Thread::current()) {
883 }
884
885 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
886 const oop obj = RawAccess<>::oop_load(p);
887 if (!CompressedOops::is_null(obj)) {
888 if (!_mark_context->is_marked(obj)) {
889 if (_generation->contains(obj)) {
890 // Note: The obj is dead here. Do not touch it, just clear.
891 ShenandoahHeap::atomic_clear_oop(p, obj);
892 }
893 } else if (_evac_in_progress && _heap->in_collection_set(obj)) {
894 oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
895 if (resolved == obj) {
896 resolved = _heap->evacuate_object(obj, _thread);
897 }
898 shenandoah_assert_not_in_cset_except(p, resolved, _heap->cancelled_gc());
899 ShenandoahHeap::atomic_update_oop(resolved, p, obj);
900 }
901 }
902 }
903
904 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(narrowOop* p) {
905 ShouldNotReachHere();
906 }
907
908 class ShenandoahIsCLDAliveClosure : public CLDClosure {
909 public:
910 void do_cld(ClassLoaderData* cld) {
911 cld->is_alive();
912 }
913 };
914
915 class ShenandoahIsNMethodAliveClosure: public NMethodClosure {
916 public:
917 void do_nmethod(nmethod* n) {
918 n->is_unloading();
919 }
920 };
921
922 // This task not only evacuates/updates marked weak roots, but also "null"
923 // dead weak roots.
924 class ShenandoahConcurrentWeakRootsEvacUpdateTask : public WorkerTask {
925 private:
926 ShenandoahVMWeakRoots<true /*concurrent*/> _vm_roots;
927
928 // Roots related to concurrent class unloading
929 ShenandoahClassLoaderDataRoots<true /* concurrent */>
930 _cld_roots;
931 ShenandoahConcurrentNMethodIterator _nmethod_itr;
932 ShenandoahGeneration* _generation;
933 ShenandoahPhaseTimings::Phase _phase;
934
935 public:
936 ShenandoahConcurrentWeakRootsEvacUpdateTask(ShenandoahGeneration* generation, ShenandoahPhaseTimings::Phase phase) :
937 WorkerTask("Shenandoah Evacuate/Update Concurrent Weak Roots"),
938 _vm_roots(phase),
939 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
940 _nmethod_itr(ShenandoahCodeRoots::table()),
941 _generation(generation),
942 _phase(phase) {}
943
944 ~ShenandoahConcurrentWeakRootsEvacUpdateTask() {
945 // Notify runtime data structures of potentially dead oops
946 _vm_roots.report_num_dead();
947 }
948
949 void work(uint worker_id) override {
950 ShenandoahConcurrentWorkerSession worker_session(worker_id);
951 ShenandoahSuspendibleThreadSetJoiner sts_join;
952 {
953 ShenandoahEvacOOMScope oom;
954 // jni_roots and weak_roots are OopStorage backed roots, concurrent iteration
955 // may race against OopStorage::release() calls.
956 ShenandoahEvacUpdateCleanupOopStorageRootsClosure cl(_generation);
957 _vm_roots.oops_do(&cl, worker_id);
958 }
959
960 // If we are going to perform concurrent class unloading later on, we need to
961 // clean up the weak oops in CLD and determine nmethod's unloading state, so that we
962 // can clean up immediate garbage sooner.
963 if (ShenandoahHeap::heap()->unload_classes()) {
964 // Applies ShenandoahIsCLDAlive closure to CLDs, native barrier will either null the
965 // CLD's holder or evacuate it.
966 {
967 ShenandoahIsCLDAliveClosure is_cld_alive;
968 _cld_roots.cld_do(&is_cld_alive, worker_id);
969 }
970
971 // Applies ShenandoahIsNMethodAliveClosure to registered nmethods.
972 // The closure calls nmethod->is_unloading(). The is_unloading
973 // state is cached, therefore, during concurrent class unloading phase,
974 // we will not touch the metadata of unloading nmethods
975 {
976 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCacheRoots, worker_id);
977 ShenandoahIsNMethodAliveClosure is_nmethod_alive;
978 _nmethod_itr.nmethods_do(&is_nmethod_alive);
979 }
980 }
981 }
982 };
983
984 void ShenandoahConcurrentGC::op_weak_roots() {
985 ShenandoahHeap* const heap = ShenandoahHeap::heap();
986 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
987 {
988 // Concurrent weak root processing
989 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_work);
990 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_roots_work);
991 ShenandoahConcurrentWeakRootsEvacUpdateTask task(_generation, ShenandoahPhaseTimings::conc_weak_roots_work);
992 heap->workers()->run_task(&task);
993 }
994
995 {
996 // It is possible for mutators executing the load reference barrier to have
997 // loaded an oop through a weak handle that has since been nulled out by
998 // weak root processing. Handshaking here forces them to complete the
999 // barrier before the GC cycle continues and does something that would
1000 // change the evaluation of the barrier (for example, resetting the TAMS
1001 // on trashed regions could make an oop appear to be marked _after_ the
1002 // region has been recycled).
1003 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
1004 heap->rendezvous_threads("Shenandoah Concurrent Weak Roots");
1005 }
1006 }
1007
1008 void ShenandoahConcurrentGC::op_class_unloading() {
1009 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1010 assert (heap->is_concurrent_weak_root_in_progress() &&
1011 heap->unload_classes(),
1012 "Checked by caller");
1013 heap->do_class_unloading();
1014 }
1015
1016 class ShenandoahEvacUpdateCodeCacheClosure : public NMethodClosure {
1017 private:
1018 BarrierSetNMethod* const _bs;
1019 ShenandoahEvacuateUpdateMetadataClosure _cl;
1020
1021 public:
1022 ShenandoahEvacUpdateCodeCacheClosure() :
1023 _bs(BarrierSet::barrier_set()->barrier_set_nmethod()),
1024 _cl() {
1025 }
1026
1027 void do_nmethod(nmethod* n) {
1028 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(n);
1029 ShenandoahNMethodLocker locker(data->lock());
1030 // Setup EvacOOM scope below reentrant lock to avoid deadlock with
1031 // nmethod_entry_barrier
1032 ShenandoahEvacOOMScope oom;
1033 data->oops_do(&_cl, true/*fix relocation*/);
1034 _bs->disarm(n);
1035 }
1036 };
1037
1038 class ShenandoahConcurrentRootsEvacUpdateTask : public WorkerTask {
1039 private:
1040 ShenandoahPhaseTimings::Phase _phase;
1041 ShenandoahVMRoots<true /*concurrent*/> _vm_roots;
1042 ShenandoahClassLoaderDataRoots<true /*concurrent*/>
1043 _cld_roots;
1044 ShenandoahConcurrentNMethodIterator _nmethod_itr;
1045
1046 public:
1047 ShenandoahConcurrentRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
1048 WorkerTask("Shenandoah Evacuate/Update Concurrent Strong Roots"),
1049 _phase(phase),
1050 _vm_roots(phase),
1051 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
1052 _nmethod_itr(ShenandoahCodeRoots::table()) {}
1053
1054 void work(uint worker_id) {
1055 ShenandoahConcurrentWorkerSession worker_session(worker_id);
1056 {
1057 ShenandoahEvacOOMScope oom;
1058 {
1059 // vm_roots and weak_roots are OopStorage backed roots, concurrent iteration
1060 // may race against OopStorage::release() calls.
1061 ShenandoahContextEvacuateUpdateRootsClosure cl;
1062 _vm_roots.oops_do<ShenandoahContextEvacuateUpdateRootsClosure>(&cl, worker_id);
1063 }
1064
1065 {
1066 ShenandoahEvacuateUpdateMetadataClosure cl;
1067 CLDToOopClosure clds(&cl, ClassLoaderData::_claim_strong);
1068 _cld_roots.cld_do(&clds, worker_id);
1069 }
1070 }
1071
1072 // Cannot setup ShenandoahEvacOOMScope here, due to potential deadlock with nmethod_entry_barrier.
1073 if (!ShenandoahHeap::heap()->unload_classes()) {
1074 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCacheRoots, worker_id);
1075 ShenandoahEvacUpdateCodeCacheClosure cl;
1076 _nmethod_itr.nmethods_do(&cl);
1077 }
1078 }
1079 };
1080
1081 void ShenandoahConcurrentGC::op_strong_roots() {
1082 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1083 assert(heap->is_concurrent_strong_root_in_progress(), "Checked by caller");
1084 ShenandoahConcurrentRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_strong_roots);
1085 heap->workers()->run_task(&task);
1086 heap->set_concurrent_strong_root_in_progress(false);
1087 }
1088
1089 void ShenandoahConcurrentGC::op_cleanup_early() {
1090 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1091 ShenandoahWorkerPolicy::calc_workers_for_conc_cleanup(),
1092 "cleanup early.");
1093 ShenandoahHeap::heap()->recycle_trash();
1094 }
1095
1096 void ShenandoahConcurrentGC::op_evacuate() {
1097 ShenandoahHeap::heap()->evacuate_collection_set(_generation, true /*concurrent*/);
1098 if (ShenandoahDelayGC > 0) {
1099 os::naked_sleep(ShenandoahDelayGC);
1100 }
1101 }
1102
1103 void ShenandoahConcurrentGC::op_init_update_refs() {
1104 if (ShenandoahVerify) {
1105 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1106 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::init_update_refs_verify);
1107 heap->verifier()->verify_before_update_refs(_generation);
1108 }
1109 }
1110
1111 void ShenandoahConcurrentGC::op_update_refs() {
1112 ShenandoahHeap::heap()->update_heap_references(_generation, true /*concurrent*/);
1113 if (ShenandoahDelayGC > 0) {
1114 os::naked_sleep(ShenandoahDelayGC);
1115 }
1116 }
1117
1118 class ShenandoahUpdateThreadHandshakeClosure : public HandshakeClosure {
1119 private:
1120 // This closure runs when thread is stopped for handshake, which means
1121 // we can use non-concurrent closure here, as long as it only updates
1122 // locations modified by the thread itself, i.e. stack locations.
1123 ShenandoahNonConcUpdateRefsClosure _cl;
1124 public:
1125 ShenandoahUpdateThreadHandshakeClosure();
1126 void do_thread(Thread* thread) override;
1127 };
1128
1129 ShenandoahUpdateThreadHandshakeClosure::ShenandoahUpdateThreadHandshakeClosure() :
1130 HandshakeClosure("Shenandoah Update Thread Roots") {
1131 }
1132
1133 void ShenandoahUpdateThreadHandshakeClosure::do_thread(Thread* thread) {
1134 if (thread->is_Java_thread()) {
1135 JavaThread* jt = JavaThread::cast(thread);
1136 ResourceMark rm;
1137 jt->oops_do(&_cl, nullptr);
1138 }
1139 }
1140
1141 class ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers final : public HandshakeClosure {
1142 // When Shenandoah is marking the old generation, it is possible for the SATB barrier
1143 // to pick up overwritten pointers that point into a cset region. If these pointers
1144 // are accessed by mark threads, they will crash. Once update refs has completed, it is
1145 // no longer possible for a mutator thread to overwrite a pointer into a cset region.
1146 //
1147 // Therefore, at the end of update refs, we use this closure to update the thread roots
1148 // and 'complete' all the thread local SATB buffers. Completing these will filter out
1149 // anything that has already been marked or anything that points to a region which is
1150 // not old. We do not need to worry about ABA situations where a region may become old
1151 // after the pointer is enqueued but before it is filtered. There are only two ways a
1152 // region may become old:
1153 // 1. The region is promoted in place. This is safe because such regions will never
1154 // be in the collection set. If this happens, the pointer will be preserved, essentially
1155 // becoming part of the old snapshot.
1156 // 2. The region is allocated during evacuation of old. This is also not a concern because
1157 // we haven't yet finished marking old so no mixed evacuations will happen.
1158 ShenandoahUpdateThreadHandshakeClosure _update_roots;
1159 ShenandoahFlushSATB _flush_all_satb;
1160
1161 public:
1162 ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers() :
1163 HandshakeClosure("Shenandoah Update Thread Roots and Flush SATB"),
1164 _flush_all_satb(ShenandoahBarrierSet::satb_mark_queue_set()) {
1165 assert(ShenandoahBarrierSet::satb_mark_queue_set().get_filter_out_young(),
1166 "Should be filtering pointers outside of old during old marking");
1167 }
1168
1169 void do_thread(Thread* thread) override {
1170 _update_roots.do_thread(thread);
1171 _flush_all_satb.do_thread(thread);
1172 }
1173 };
1174
1175 void ShenandoahConcurrentGC::op_update_thread_roots() {
1176 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1177 if (heap->is_concurrent_old_mark_in_progress()) {
1178 ShenandoahUpdateThreadRootsAndFlushOldSatbBuffers cl;
1179 Handshake::execute(&cl);
1180 } else {
1181 ShenandoahUpdateThreadHandshakeClosure cl;
1182 Handshake::execute(&cl);
1183 }
1184 }
1185
1186 void ShenandoahConcurrentGC::op_final_update_refs() {
1187 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1188 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
1189 assert(!heap->_update_refs_iterator.has_next(), "Should have finished update references");
1190
1191 heap->finish_concurrent_roots();
1192
1193 // Clear cancelled GC, if set. On cancellation path, the block before would handle
1194 // everything.
1195 if (heap->cancelled_gc()) {
1196 heap->clear_cancelled_gc();
1197 }
1198
1199 // Has to be done before cset is clear
1200 if (ShenandoahVerify) {
1201 heap->verifier()->verify_roots_in_to_space(_generation);
1202 }
1203
1204 // If we are running in generational mode and this is an aging cycle, this will also age active
1205 // regions that haven't been used for allocation.
1206 heap->update_heap_region_states(true /*concurrent*/);
1207
1208 heap->set_update_refs_in_progress(false);
1209 heap->set_has_forwarded_objects(false);
1210
1211 if (heap->mode()->is_generational() && heap->is_concurrent_old_mark_in_progress()) {
1212 // Aging_cycle is only relevant during evacuation cycle for individual objects and during final mark for
1213 // entire regions. Both of these relevant operations occur before final update refs.
1214 ShenandoahGenerationalHeap::heap()->set_aging_cycle(false);
1215 }
1216
1217 if (ShenandoahVerify) {
1218 ShenandoahTimingsTracker v(ShenandoahPhaseTimings::final_update_refs_verify);
1219 heap->verifier()->verify_after_update_refs(_generation);
1220 }
1221
1222 if (VerifyAfterGC) {
1223 Universe::verify();
1224 }
1225
1226 heap->rebuild_free_set(true /*concurrent*/);
1227 _generation->heuristics()->start_idle_span();
1228
1229 {
1230 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_propagate_gc_state);
1231 heap->propagate_gc_state_to_all_threads();
1232 }
1233 }
1234
1235 bool ShenandoahConcurrentGC::entry_final_roots() {
1236 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1237 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
1238
1239
1240 const char* msg = conc_final_roots_event_message();
1241 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_final_roots);
1242 EventMark em("%s", msg);
1243 ShenandoahWorkerScope scope(heap->workers(),
1244 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
1245 msg);
1246
1247 if (heap->mode()->is_generational()) {
1248 if (!complete_abbreviated_cycle()) {
1249 return false;
1250 }
1251 }
1252
1253 heap->concurrent_final_roots();
1254 return true;
1255 }
1256
1257 void ShenandoahConcurrentGC::op_verify_final_roots() {
1258 if (VerifyAfterGC) {
1259 Universe::verify();
1260 }
1261 }
1262
1263 void ShenandoahConcurrentGC::op_cleanup_complete() {
1264 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1265 ShenandoahWorkerPolicy::calc_workers_for_conc_cleanup(),
1266 "cleanup complete.");
1267 ShenandoahHeap::heap()->recycle_trash();
1268 }
1269
1270 void ShenandoahConcurrentGC::op_reset_after_collect() {
1271 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
1272 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
1273 "reset after collection.");
1274
1275 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1276 if (heap->mode()->is_generational()) {
1277 // If we are in the midst of an old gc bootstrap or an old marking, we want to leave the mark bit map of
1278 // the young generation intact. In particular, reference processing in the old generation may potentially
1279 // need the reachability of a young generation referent of a Reference object in the old generation.
1280 if (!_do_old_gc_bootstrap && !heap->is_concurrent_old_mark_in_progress()) {
1281 heap->young_generation()->reset_mark_bitmap<false>();
1282 }
1283 } else {
1284 _generation->reset_mark_bitmap<false>();
1285 }
1286 }
1287
1288 bool ShenandoahConcurrentGC::check_cancellation_and_abort(ShenandoahDegenPoint point) {
1289 if (ShenandoahHeap::heap()->cancelled_gc()) {
1290 _degen_point = point;
1291 return true;
1292 }
1293 return false;
1294 }
1295
1296 const char* ShenandoahConcurrentGC::init_mark_event_message() const {
1297 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1298 assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
1299 if (heap->unload_classes()) {
1300 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Init Mark", " (unload classes)");
1301 } else {
1302 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Init Mark", "");
1303 }
1304 }
1305
1306 const char* ShenandoahConcurrentGC::final_mark_event_message() const {
1307 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1308 assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
1309 "Should not have forwarded objects during final mark, unless old gen concurrent mark is running");
1310
1311 if (heap->unload_classes()) {
1312 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Final Mark", " (unload classes)");
1313 } else {
1314 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Final Mark", "");
1315 }
1316 }
1317
1318 const char* ShenandoahConcurrentGC::conc_mark_event_message() const {
1319 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1320 assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
1321 "Should not have forwarded objects concurrent mark, unless old gen concurrent mark is running");
1322 if (heap->unload_classes()) {
1323 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent marking", " (unload classes)");
1324 } else {
1325 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent marking", "");
1326 }
1327 }
1328
1329 const char* ShenandoahConcurrentGC::conc_reset_event_message() const {
1330 if (ShenandoahHeap::heap()->unload_classes()) {
1331 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent reset", " (unload classes)");
1332 } else {
1333 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent reset", "");
1334 }
1335 }
1336
1337 const char* ShenandoahConcurrentGC::conc_reset_after_collect_event_message() const {
1338 if (ShenandoahHeap::heap()->unload_classes()) {
1339 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent reset after collect", " (unload classes)");
1340 } else {
1341 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent reset after collect", "");
1342 }
1343 }
1344
1345 const char* ShenandoahConcurrentGC::verify_final_roots_event_message() const {
1346 if (ShenandoahHeap::heap()->unload_classes()) {
1347 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Verify Final Roots", " (unload classes)");
1348 } else {
1349 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Verify Final Roots", "");
1350 }
1351 }
1352
1353 const char* ShenandoahConcurrentGC::conc_final_roots_event_message() const {
1354 if (ShenandoahHeap::heap()->unload_classes()) {
1355 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent Final Roots", " (unload classes)");
1356 } else {
1357 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent Final Roots", "");
1358 }
1359 }
1360
1361 const char* ShenandoahConcurrentGC::conc_weak_refs_event_message() const {
1362 if (ShenandoahHeap::heap()->unload_classes()) {
1363 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent weak references", " (unload classes)");
1364 } else {
1365 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent weak references", "");
1366 }
1367 }
1368
1369 const char* ShenandoahConcurrentGC::conc_weak_roots_event_message() const {
1370 if (ShenandoahHeap::heap()->unload_classes()) {
1371 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent weak roots", " (unload classes)");
1372 } else {
1373 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent weak roots", "");
1374 }
1375 }
1376
1377 const char* ShenandoahConcurrentGC::conc_cleanup_event_message() const {
1378 if (ShenandoahHeap::heap()->unload_classes()) {
1379 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent cleanup", " (unload classes)");
1380 } else {
1381 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent cleanup", "");
1382 }
1383 }
1384
1385 const char* ShenandoahConcurrentGC::conc_init_update_refs_event_message() const {
1386 if (ShenandoahHeap::heap()->unload_classes()) {
1387 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent Init Update Refs", " (unload classes)");
1388 } else {
1389 SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Concurrent Init Update Refs", "");
1390 }
1391 }