1 /*
2 * Copyright (c) 2021, 2022, Red Hat, Inc. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "gc/shared/barrierSetNMethod.hpp"
28 #include "gc/shared/collectorCounters.hpp"
29 #include "gc/shared/continuationGCSupport.inline.hpp"
30 #include "gc/shenandoah/shenandoahBreakpoint.hpp"
31 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
32 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
33 #include "gc/shenandoah/shenandoahFreeSet.hpp"
34 #include "gc/shenandoah/shenandoahLock.hpp"
35 #include "gc/shenandoah/shenandoahMark.inline.hpp"
36 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
37 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
38 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
39 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
40 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
41 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
42 #include "gc/shenandoah/shenandoahUtils.hpp"
43 #include "gc/shenandoah/shenandoahVerifier.hpp"
44 #include "gc/shenandoah/shenandoahVMOperations.hpp"
45 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
46 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
47 #include "memory/allocation.hpp"
48 #include "prims/jvmtiTagMap.hpp"
49 #include "runtime/vmThread.hpp"
50 #include "utilities/events.hpp"
51
52 // Breakpoint support
53 class ShenandoahBreakpointGCScope : public StackObj {
54 private:
55 const GCCause::Cause _cause;
56 public:
57 ShenandoahBreakpointGCScope(GCCause::Cause cause) : _cause(cause) {
58 if (cause == GCCause::_wb_breakpoint) {
59 ShenandoahBreakpoint::start_gc();
60 ShenandoahBreakpoint::at_before_gc();
61 }
62 }
63
64 ~ShenandoahBreakpointGCScope() {
65 if (_cause == GCCause::_wb_breakpoint) {
66 ShenandoahBreakpoint::at_after_gc();
67 }
68 }
69 };
70
71 class ShenandoahBreakpointMarkScope : public StackObj {
72 private:
73 const GCCause::Cause _cause;
74 public:
75 ShenandoahBreakpointMarkScope(GCCause::Cause cause) : _cause(cause) {
76 if (_cause == GCCause::_wb_breakpoint) {
77 ShenandoahBreakpoint::at_after_marking_started();
78 }
79 }
80
81 ~ShenandoahBreakpointMarkScope() {
82 if (_cause == GCCause::_wb_breakpoint) {
83 ShenandoahBreakpoint::at_before_marking_completed();
84 }
85 }
86 };
87
88 ShenandoahConcurrentGC::ShenandoahConcurrentGC() :
89 _mark(),
90 _degen_point(ShenandoahDegenPoint::_degenerated_unset) {
91 }
92
93 ShenandoahGC::ShenandoahDegenPoint ShenandoahConcurrentGC::degen_point() const {
94 return _degen_point;
95 }
96
97 void ShenandoahConcurrentGC::cancel() {
98 ShenandoahConcurrentMark::cancel();
99 }
100
101 bool ShenandoahConcurrentGC::collect(GCCause::Cause cause) {
102 ShenandoahHeap* const heap = ShenandoahHeap::heap();
103 ShenandoahBreakpointGCScope breakpoint_gc_scope(cause);
104
105 // Reset for upcoming marking
106 entry_reset();
107
108 // Start initial mark under STW
109 vmop_entry_init_mark();
110
111 {
112 ShenandoahBreakpointMarkScope breakpoint_mark_scope(cause);
113 // Concurrent mark roots
114 entry_mark_roots();
115 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_outside_cycle)) return false;
116
117 // Continue concurrent mark
118 entry_mark();
119 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) return false;
120 }
121
122 // Complete marking under STW, and start evacuation
123 vmop_entry_final_mark();
124
125 // Concurrent stack processing
126 if (heap->is_evacuation_in_progress()) {
127 entry_thread_roots();
128 }
129
130 // Process weak roots that might still point to regions that would be broken by cleanup
131 if (heap->is_concurrent_weak_root_in_progress()) {
132 entry_weak_refs();
133 entry_weak_roots();
134 }
135
136 // Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
137 // the space. This would be the last action if there is nothing to evacuate.
138 entry_cleanup_early();
139
140 {
141 ShenandoahHeapLocker locker(heap->lock());
142 heap->free_set()->log_status();
143 }
144
145 // Perform concurrent class unloading
146 if (heap->unload_classes() &&
147 heap->is_concurrent_weak_root_in_progress()) {
148 entry_class_unloading();
149 }
150
151 // Processing strong roots
152 // This may be skipped if there is nothing to update/evacuate.
153 // If so, strong_root_in_progress would be unset.
154 if (heap->is_concurrent_strong_root_in_progress()) {
155 entry_strong_roots();
156 }
157
158 // Continue the cycle with evacuation and optional update-refs.
159 // This may be skipped if there is nothing to evacuate.
160 // If so, evac_in_progress would be unset by collection set preparation code.
161 if (heap->is_evacuation_in_progress()) {
162 // Concurrently evacuate
163 entry_evacuate();
164 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) return false;
165
166 // Perform update-refs phase.
167 vmop_entry_init_updaterefs();
168 entry_updaterefs();
169 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) return false;
170
171 // Concurrent update thread roots
172 entry_update_thread_roots();
173 if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) return false;
174
175 vmop_entry_final_updaterefs();
176
177 // Update references freed up collection set, kick the cleanup to reclaim the space.
178 entry_cleanup_complete();
179 } else {
180 vmop_entry_final_roots();
181 }
182
183 return true;
184 }
185
186 void ShenandoahConcurrentGC::vmop_entry_init_mark() {
187 ShenandoahHeap* const heap = ShenandoahHeap::heap();
188 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
189 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_mark_gross);
190
191 heap->try_inject_alloc_failure();
192 VM_ShenandoahInitMark op(this);
193 VMThread::execute(&op); // jump to entry_init_mark() under safepoint
194 }
195
196 void ShenandoahConcurrentGC::vmop_entry_final_mark() {
197 ShenandoahHeap* const heap = ShenandoahHeap::heap();
198 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
199 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_mark_gross);
200
201 heap->try_inject_alloc_failure();
202 VM_ShenandoahFinalMarkStartEvac op(this);
203 VMThread::execute(&op); // jump to entry_final_mark under safepoint
204 }
205
206 void ShenandoahConcurrentGC::vmop_entry_init_updaterefs() {
207 ShenandoahHeap* const heap = ShenandoahHeap::heap();
208 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
209 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::init_update_refs_gross);
210
211 heap->try_inject_alloc_failure();
212 VM_ShenandoahInitUpdateRefs op(this);
213 VMThread::execute(&op);
214 }
215
216 void ShenandoahConcurrentGC::vmop_entry_final_updaterefs() {
217 ShenandoahHeap* const heap = ShenandoahHeap::heap();
218 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
219 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_update_refs_gross);
220
221 heap->try_inject_alloc_failure();
222 VM_ShenandoahFinalUpdateRefs op(this);
223 VMThread::execute(&op);
224 }
225
226 void ShenandoahConcurrentGC::vmop_entry_final_roots() {
227 ShenandoahHeap* const heap = ShenandoahHeap::heap();
228 TraceCollectorStats tcs(heap->monitoring_support()->stw_collection_counters());
229 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::final_roots_gross);
230
231 // This phase does not use workers, no need for setup
232 heap->try_inject_alloc_failure();
233 VM_ShenandoahFinalRoots op(this);
234 VMThread::execute(&op);
235 }
236
237 void ShenandoahConcurrentGC::entry_init_mark() {
238 const char* msg = init_mark_event_message();
239 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_mark);
240 EventMark em("%s", msg);
241
242 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
243 ShenandoahWorkerPolicy::calc_workers_for_init_marking(),
244 "init marking");
245
246 op_init_mark();
247 }
248
249 void ShenandoahConcurrentGC::entry_final_mark() {
250 const char* msg = final_mark_event_message();
251 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_mark);
252 EventMark em("%s", msg);
253
254 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
255 ShenandoahWorkerPolicy::calc_workers_for_final_marking(),
256 "final marking");
257
258 op_final_mark();
259 }
260
261 void ShenandoahConcurrentGC::entry_init_updaterefs() {
262 static const char* msg = "Pause Init Update Refs";
263 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::init_update_refs);
264 EventMark em("%s", msg);
265
266 // No workers used in this phase, no setup required
267 op_init_updaterefs();
268 }
269
270 void ShenandoahConcurrentGC::entry_final_updaterefs() {
271 static const char* msg = "Pause Final Update Refs";
272 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_update_refs);
273 EventMark em("%s", msg);
274
275 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
276 ShenandoahWorkerPolicy::calc_workers_for_final_update_ref(),
277 "final reference update");
278
279 op_final_updaterefs();
280 }
281
282 void ShenandoahConcurrentGC::entry_final_roots() {
283 static const char* msg = "Pause Final Roots";
284 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::final_roots);
285 EventMark em("%s", msg);
286
287 op_final_roots();
288 }
289
290 void ShenandoahConcurrentGC::entry_reset() {
291 ShenandoahHeap* const heap = ShenandoahHeap::heap();
292 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
293 static const char* msg = "Concurrent reset";
294 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset);
295 EventMark em("%s", msg);
296
297 ShenandoahWorkerScope scope(heap->workers(),
298 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
299 "concurrent reset");
300
301 heap->try_inject_alloc_failure();
302 op_reset();
303 }
304
305 void ShenandoahConcurrentGC::entry_mark_roots() {
306 ShenandoahHeap* const heap = ShenandoahHeap::heap();
307 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
308 const char* msg = "Concurrent marking roots";
309 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark_roots);
310 EventMark em("%s", msg);
311
312 ShenandoahWorkerScope scope(heap->workers(),
313 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
314 "concurrent marking roots");
315
316 heap->try_inject_alloc_failure();
317 op_mark_roots();
318 }
319
320 void ShenandoahConcurrentGC::entry_mark() {
321 ShenandoahHeap* const heap = ShenandoahHeap::heap();
322 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
323 const char* msg = conc_mark_event_message();
324 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark);
325 EventMark em("%s", msg);
326
327 ShenandoahWorkerScope scope(heap->workers(),
328 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
329 "concurrent marking");
330
331 heap->try_inject_alloc_failure();
332 op_mark();
333 }
334
335 void ShenandoahConcurrentGC::entry_thread_roots() {
336 ShenandoahHeap* const heap = ShenandoahHeap::heap();
337 static const char* msg = "Concurrent thread roots";
338 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_thread_roots);
339 EventMark em("%s", msg);
340
341 ShenandoahWorkerScope scope(heap->workers(),
342 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
343 msg);
344
345 heap->try_inject_alloc_failure();
346 op_thread_roots();
347 }
348
349 void ShenandoahConcurrentGC::entry_weak_refs() {
350 ShenandoahHeap* const heap = ShenandoahHeap::heap();
351 static const char* msg = "Concurrent weak references";
352 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_refs);
353 EventMark em("%s", msg);
354
355 ShenandoahWorkerScope scope(heap->workers(),
356 ShenandoahWorkerPolicy::calc_workers_for_conc_refs_processing(),
357 "concurrent weak references");
358
359 heap->try_inject_alloc_failure();
360 op_weak_refs();
361 }
362
363 void ShenandoahConcurrentGC::entry_weak_roots() {
364 ShenandoahHeap* const heap = ShenandoahHeap::heap();
365 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
366 static const char* msg = "Concurrent weak roots";
367 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_weak_roots);
368 EventMark em("%s", msg);
369
370 ShenandoahWorkerScope scope(heap->workers(),
371 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
372 "concurrent weak root");
373
374 heap->try_inject_alloc_failure();
375 op_weak_roots();
376 }
377
378 void ShenandoahConcurrentGC::entry_class_unloading() {
379 ShenandoahHeap* const heap = ShenandoahHeap::heap();
380 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
381 static const char* msg = "Concurrent class unloading";
382 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_class_unload);
383 EventMark em("%s", msg);
384
385 ShenandoahWorkerScope scope(heap->workers(),
386 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
387 "concurrent class unloading");
388
389 heap->try_inject_alloc_failure();
390 op_class_unloading();
391 }
392
393 void ShenandoahConcurrentGC::entry_strong_roots() {
394 ShenandoahHeap* const heap = ShenandoahHeap::heap();
395 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
396 static const char* msg = "Concurrent strong roots";
397 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_strong_roots);
398 EventMark em("%s", msg);
399
400 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_strong_roots);
401
402 ShenandoahWorkerScope scope(heap->workers(),
403 ShenandoahWorkerPolicy::calc_workers_for_conc_root_processing(),
404 "concurrent strong root");
405
406 heap->try_inject_alloc_failure();
407 op_strong_roots();
408 }
409
410 void ShenandoahConcurrentGC::entry_cleanup_early() {
411 ShenandoahHeap* const heap = ShenandoahHeap::heap();
412 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
413 static const char* msg = "Concurrent cleanup";
414 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_early, true /* log_heap_usage */);
415 EventMark em("%s", msg);
416
417 // This phase does not use workers, no need for setup
418 heap->try_inject_alloc_failure();
419 op_cleanup_early();
420 }
421
422 void ShenandoahConcurrentGC::entry_evacuate() {
423 ShenandoahHeap* const heap = ShenandoahHeap::heap();
424 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
425
426 static const char* msg = "Concurrent evacuation";
427 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_evac);
428 EventMark em("%s", msg);
429
430 ShenandoahWorkerScope scope(heap->workers(),
431 ShenandoahWorkerPolicy::calc_workers_for_conc_evac(),
432 "concurrent evacuation");
433
434 heap->try_inject_alloc_failure();
435 op_evacuate();
436 }
437
438 void ShenandoahConcurrentGC::entry_update_thread_roots() {
439 ShenandoahHeap* const heap = ShenandoahHeap::heap();
440 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
441
442 static const char* msg = "Concurrent update thread roots";
443 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_thread_roots);
444 EventMark em("%s", msg);
445
446 // No workers used in this phase, no setup required
447 heap->try_inject_alloc_failure();
448 op_update_thread_roots();
449 }
450
451 void ShenandoahConcurrentGC::entry_updaterefs() {
452 ShenandoahHeap* const heap = ShenandoahHeap::heap();
453 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
454 static const char* msg = "Concurrent update references";
455 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_update_refs);
456 EventMark em("%s", msg);
457
458 ShenandoahWorkerScope scope(heap->workers(),
459 ShenandoahWorkerPolicy::calc_workers_for_conc_update_ref(),
460 "concurrent reference update");
461
462 heap->try_inject_alloc_failure();
463 op_updaterefs();
464 }
465
466 void ShenandoahConcurrentGC::entry_cleanup_complete() {
467 ShenandoahHeap* const heap = ShenandoahHeap::heap();
468 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
469 static const char* msg = "Concurrent cleanup";
470 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_cleanup_complete, true /* log_heap_usage */);
471 EventMark em("%s", msg);
472
473 // This phase does not use workers, no need for setup
474 heap->try_inject_alloc_failure();
475 op_cleanup_complete();
476 }
477
478 void ShenandoahConcurrentGC::op_reset() {
479 ShenandoahHeap* const heap = ShenandoahHeap::heap();
480 if (ShenandoahPacing) {
481 heap->pacer()->setup_for_reset();
482 }
483
484 heap->prepare_gc();
485 }
486
487 class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
488 private:
489 ShenandoahMarkingContext* const _ctx;
490 public:
491 ShenandoahInitMarkUpdateRegionStateClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
492
493 void heap_region_do(ShenandoahHeapRegion* r) {
494 assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
495 if (r->is_active()) {
496 // Check if region needs updating its TAMS. We have updated it already during concurrent
497 // reset, so it is very likely we don't need to do another write here.
498 if (_ctx->top_at_mark_start(r) != r->top()) {
499 _ctx->capture_top_at_mark_start(r);
500 }
501 } else {
502 assert(_ctx->top_at_mark_start(r) == r->top(),
503 "Region " SIZE_FORMAT " should already have correct TAMS", r->index());
504 }
505 }
506
507 bool is_thread_safe() { return true; }
508 };
509
510 void ShenandoahConcurrentGC::start_mark() {
511 _mark.start_mark();
512 }
513
514 void ShenandoahConcurrentGC::op_init_mark() {
515 ShenandoahHeap* const heap = ShenandoahHeap::heap();
516 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
517 assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
518
519 assert(heap->marking_context()->is_bitmap_clear(), "need clear marking bitmap");
520 assert(!heap->marking_context()->is_complete(), "should not be complete");
521 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
522
523 if (ShenandoahVerify) {
524 heap->verifier()->verify_before_concmark();
525 }
526
527 if (VerifyBeforeGC) {
528 Universe::verify();
529 }
530
531 heap->set_concurrent_mark_in_progress(true);
532
533 start_mark();
534
535 {
536 ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
537 ShenandoahInitMarkUpdateRegionStateClosure cl;
538 heap->parallel_heap_region_iterate(&cl);
539 }
540
541 // Weak reference processing
542 ShenandoahReferenceProcessor* rp = heap->ref_processor();
543 rp->reset_thread_locals();
544 rp->set_soft_reference_policy(heap->soft_ref_policy()->should_clear_all_soft_refs());
545
546 // Make above changes visible to worker threads
547 OrderAccess::fence();
548
549 // Arm nmethods for concurrent mark
550 ShenandoahCodeRoots::arm_nmethods_for_mark();
551
552 ShenandoahStackWatermark::change_epoch_id();
553 if (ShenandoahPacing) {
554 heap->pacer()->setup_for_mark();
555 }
556 }
557
558 void ShenandoahConcurrentGC::op_mark_roots() {
559 _mark.mark_concurrent_roots();
560 }
561
562 void ShenandoahConcurrentGC::op_mark() {
563 _mark.concurrent_mark();
564 }
565
566 void ShenandoahConcurrentGC::op_final_mark() {
567 ShenandoahHeap* const heap = ShenandoahHeap::heap();
568 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
569 assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
570
571 if (ShenandoahVerify) {
572 heap->verifier()->verify_roots_no_forwarded();
573 }
574
575 if (!heap->cancelled_gc()) {
576 _mark.finish_mark();
577 assert(!heap->cancelled_gc(), "STW mark cannot OOM");
578
579 // Notify JVMTI that the tagmap table will need cleaning.
580 JvmtiTagMap::set_needs_cleaning();
581
582 heap->prepare_regions_and_collection_set(true /*concurrent*/);
583
584 // Has to be done after cset selection
585 heap->prepare_concurrent_roots();
586
587 if (!heap->collection_set()->is_empty()) {
588 if (ShenandoahVerify) {
589 heap->verifier()->verify_before_evacuation();
590 }
591
592 heap->set_evacuation_in_progress(true);
593 // From here on, we need to update references.
594 heap->set_has_forwarded_objects(true);
595
596 // Verify before arming for concurrent processing.
597 // Otherwise, verification can trigger stack processing.
598 if (ShenandoahVerify) {
599 heap->verifier()->verify_during_evacuation();
600 }
601
602 // Arm nmethods/stack for concurrent processing
603 ShenandoahCodeRoots::arm_nmethods_for_evac();
604 ShenandoahStackWatermark::change_epoch_id();
605
606 if (ShenandoahPacing) {
607 heap->pacer()->setup_for_evac();
608 }
609 } else {
610 if (ShenandoahVerify) {
611 heap->verifier()->verify_after_concmark();
612 }
613
614 if (VerifyAfterGC) {
615 Universe::verify();
616 }
617 }
618 }
619 }
620
621 class ShenandoahConcurrentEvacThreadClosure : public ThreadClosure {
622 private:
623 OopClosure* const _oops;
624
625 public:
626 ShenandoahConcurrentEvacThreadClosure(OopClosure* oops);
627 void do_thread(Thread* thread);
628 };
629
630 ShenandoahConcurrentEvacThreadClosure::ShenandoahConcurrentEvacThreadClosure(OopClosure* oops) :
631 _oops(oops) {
632 }
633
634 void ShenandoahConcurrentEvacThreadClosure::do_thread(Thread* thread) {
635 JavaThread* const jt = JavaThread::cast(thread);
636 StackWatermarkSet::finish_processing(jt, _oops, StackWatermarkKind::gc);
637 }
638
639 class ShenandoahConcurrentEvacUpdateThreadTask : public WorkerTask {
640 private:
641 ShenandoahJavaThreadsIterator _java_threads;
642
643 public:
644 ShenandoahConcurrentEvacUpdateThreadTask(uint n_workers) :
645 WorkerTask("Shenandoah Evacuate/Update Concurrent Thread Roots"),
646 _java_threads(ShenandoahPhaseTimings::conc_thread_roots, n_workers) {
647 }
648
649 void work(uint worker_id) {
650 // ShenandoahEvacOOMScope has to be setup by ShenandoahContextEvacuateUpdateRootsClosure.
651 // Otherwise, may deadlock with watermark lock
652 ShenandoahContextEvacuateUpdateRootsClosure oops_cl;
653 ShenandoahConcurrentEvacThreadClosure thr_cl(&oops_cl);
654 _java_threads.threads_do(&thr_cl, worker_id);
655 }
656 };
657
658 void ShenandoahConcurrentGC::op_thread_roots() {
659 ShenandoahHeap* const heap = ShenandoahHeap::heap();
660 assert(heap->is_evacuation_in_progress(), "Checked by caller");
661 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_thread_roots);
662 ShenandoahConcurrentEvacUpdateThreadTask task(heap->workers()->active_workers());
663 heap->workers()->run_task(&task);
664 }
665
666 void ShenandoahConcurrentGC::op_weak_refs() {
667 ShenandoahHeap* const heap = ShenandoahHeap::heap();
668 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
669 // Concurrent weak refs processing
670 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_refs);
671 if (heap->gc_cause() == GCCause::_wb_breakpoint) {
672 ShenandoahBreakpoint::at_after_reference_processing_started();
673 }
674 heap->ref_processor()->process_references(ShenandoahPhaseTimings::conc_weak_refs, heap->workers(), true /* concurrent */);
675 }
676
677 class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
678 private:
679 ShenandoahHeap* const _heap;
680 ShenandoahMarkingContext* const _mark_context;
681 bool _evac_in_progress;
682 Thread* const _thread;
683
684 public:
685 ShenandoahEvacUpdateCleanupOopStorageRootsClosure();
686 void do_oop(oop* p);
687 void do_oop(narrowOop* p);
688 };
689
690 ShenandoahEvacUpdateCleanupOopStorageRootsClosure::ShenandoahEvacUpdateCleanupOopStorageRootsClosure() :
691 _heap(ShenandoahHeap::heap()),
692 _mark_context(ShenandoahHeap::heap()->marking_context()),
693 _evac_in_progress(ShenandoahHeap::heap()->is_evacuation_in_progress()),
694 _thread(Thread::current()) {
695 }
696
697 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
698 const oop obj = RawAccess<>::oop_load(p);
699 if (!CompressedOops::is_null(obj)) {
700 if (!_mark_context->is_marked(obj)) {
701 shenandoah_assert_correct(p, obj);
702 ShenandoahHeap::atomic_clear_oop(p, obj);
703 } else if (_evac_in_progress && _heap->in_collection_set(obj)) {
704 oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
705 if (resolved == obj) {
706 resolved = _heap->evacuate_object(obj, _thread);
707 }
708 ShenandoahHeap::atomic_update_oop(resolved, p, obj);
709 assert(_heap->cancelled_gc() ||
710 _mark_context->is_marked(resolved) && !_heap->in_collection_set(resolved),
711 "Sanity");
712 }
713 }
714 }
715
716 void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(narrowOop* p) {
717 ShouldNotReachHere();
718 }
719
720 class ShenandoahIsCLDAliveClosure : public CLDClosure {
721 public:
722 void do_cld(ClassLoaderData* cld) {
723 cld->is_alive();
724 }
725 };
726
727 class ShenandoahIsNMethodAliveClosure: public NMethodClosure {
728 public:
729 void do_nmethod(nmethod* n) {
730 n->is_unloading();
731 }
732 };
733
734 // This task not only evacuates/updates marked weak roots, but also "null"
735 // dead weak roots.
736 class ShenandoahConcurrentWeakRootsEvacUpdateTask : public WorkerTask {
737 private:
738 ShenandoahVMWeakRoots<true /*concurrent*/> _vm_roots;
739
740 // Roots related to concurrent class unloading
741 ShenandoahClassLoaderDataRoots<true /* concurrent */>
742 _cld_roots;
743 ShenandoahConcurrentNMethodIterator _nmethod_itr;
744 ShenandoahPhaseTimings::Phase _phase;
745
746 public:
747 ShenandoahConcurrentWeakRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
748 WorkerTask("Shenandoah Evacuate/Update Concurrent Weak Roots"),
749 _vm_roots(phase),
750 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
751 _nmethod_itr(ShenandoahCodeRoots::table()),
752 _phase(phase) {
753 if (ShenandoahHeap::heap()->unload_classes()) {
754 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
755 _nmethod_itr.nmethods_do_begin();
756 }
757 }
758
759 ~ShenandoahConcurrentWeakRootsEvacUpdateTask() {
760 if (ShenandoahHeap::heap()->unload_classes()) {
761 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
762 _nmethod_itr.nmethods_do_end();
763 }
764 // Notify runtime data structures of potentially dead oops
765 _vm_roots.report_num_dead();
766 }
767
768 void work(uint worker_id) {
769 ShenandoahConcurrentWorkerSession worker_session(worker_id);
770 ShenandoahSuspendibleThreadSetJoiner sts_join;
771 {
772 ShenandoahEvacOOMScope oom;
773 // jni_roots and weak_roots are OopStorage backed roots, concurrent iteration
774 // may race against OopStorage::release() calls.
775 ShenandoahEvacUpdateCleanupOopStorageRootsClosure cl;
776 _vm_roots.oops_do(&cl, worker_id);
777 }
778
779 // If we are going to perform concurrent class unloading later on, we need to
780 // cleanup the weak oops in CLD and determinate nmethod's unloading state, so that we
781 // can cleanup immediate garbage sooner.
782 if (ShenandoahHeap::heap()->unload_classes()) {
783 // Applies ShenandoahIsCLDAlive closure to CLDs, native barrier will either null the
784 // CLD's holder or evacuate it.
785 {
786 ShenandoahIsCLDAliveClosure is_cld_alive;
787 _cld_roots.cld_do(&is_cld_alive, worker_id);
788 }
789
790 // Applies ShenandoahIsNMethodAliveClosure to registered nmethods.
791 // The closure calls nmethod->is_unloading(). The is_unloading
792 // state is cached, therefore, during concurrent class unloading phase,
793 // we will not touch the metadata of unloading nmethods
794 {
795 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCacheRoots, worker_id);
796 ShenandoahIsNMethodAliveClosure is_nmethod_alive;
797 _nmethod_itr.nmethods_do(&is_nmethod_alive);
798 }
799 }
800 }
801 };
802
803 void ShenandoahConcurrentGC::op_weak_roots() {
804 ShenandoahHeap* const heap = ShenandoahHeap::heap();
805 assert(heap->is_concurrent_weak_root_in_progress(), "Only during this phase");
806 // Concurrent weak root processing
807 {
808 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_work);
809 ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_roots_work);
810 ShenandoahConcurrentWeakRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_weak_roots_work);
811 heap->workers()->run_task(&task);
812 }
813
814 // Perform handshake to flush out dead oops
815 {
816 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_weak_roots_rendezvous);
817 heap->rendezvous_threads();
818 }
819 }
820
821 void ShenandoahConcurrentGC::op_class_unloading() {
822 ShenandoahHeap* const heap = ShenandoahHeap::heap();
823 assert (heap->is_concurrent_weak_root_in_progress() &&
824 heap->unload_classes(),
825 "Checked by caller");
826 heap->do_class_unloading();
827 }
828
829 class ShenandoahEvacUpdateCodeCacheClosure : public NMethodClosure {
830 private:
831 BarrierSetNMethod* const _bs;
832 ShenandoahEvacuateUpdateMetadataClosure _cl;
833
834 public:
835 ShenandoahEvacUpdateCodeCacheClosure() :
836 _bs(BarrierSet::barrier_set()->barrier_set_nmethod()),
837 _cl() {
838 }
839
840 void do_nmethod(nmethod* n) {
841 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(n);
842 ShenandoahReentrantLocker locker(data->lock());
843 // Setup EvacOOM scope below reentrant lock to avoid deadlock with
844 // nmethod_entry_barrier
845 ShenandoahEvacOOMScope oom;
846 data->oops_do(&_cl, true/*fix relocation*/);
847 _bs->disarm(n);
848 }
849 };
850
851 class ShenandoahConcurrentRootsEvacUpdateTask : public WorkerTask {
852 private:
853 ShenandoahPhaseTimings::Phase _phase;
854 ShenandoahVMRoots<true /*concurrent*/> _vm_roots;
855 ShenandoahClassLoaderDataRoots<true /*concurrent*/>
856 _cld_roots;
857 ShenandoahConcurrentNMethodIterator _nmethod_itr;
858
859 public:
860 ShenandoahConcurrentRootsEvacUpdateTask(ShenandoahPhaseTimings::Phase phase) :
861 WorkerTask("Shenandoah Evacuate/Update Concurrent Strong Roots"),
862 _phase(phase),
863 _vm_roots(phase),
864 _cld_roots(phase, ShenandoahHeap::heap()->workers()->active_workers(), false /*heap iteration*/),
865 _nmethod_itr(ShenandoahCodeRoots::table()) {
866 if (!ShenandoahHeap::heap()->unload_classes()) {
867 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
868 _nmethod_itr.nmethods_do_begin();
869 }
870 }
871
872 ~ShenandoahConcurrentRootsEvacUpdateTask() {
873 if (!ShenandoahHeap::heap()->unload_classes()) {
874 MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
875 _nmethod_itr.nmethods_do_end();
876 }
877 }
878
879 void work(uint worker_id) {
880 ShenandoahConcurrentWorkerSession worker_session(worker_id);
881 {
882 ShenandoahEvacOOMScope oom;
883 {
884 // vm_roots and weak_roots are OopStorage backed roots, concurrent iteration
885 // may race against OopStorage::release() calls.
886 ShenandoahContextEvacuateUpdateRootsClosure cl;
887 _vm_roots.oops_do<ShenandoahContextEvacuateUpdateRootsClosure>(&cl, worker_id);
888 }
889
890 {
891 ShenandoahEvacuateUpdateMetadataClosure cl;
892 CLDToOopClosure clds(&cl, ClassLoaderData::_claim_strong);
893 _cld_roots.cld_do(&clds, worker_id);
894 }
895 }
896
897 // Cannot setup ShenandoahEvacOOMScope here, due to potential deadlock with nmethod_entry_barrier.
898 if (!ShenandoahHeap::heap()->unload_classes()) {
899 ShenandoahWorkerTimingsTracker timer(_phase, ShenandoahPhaseTimings::CodeCacheRoots, worker_id);
900 ShenandoahEvacUpdateCodeCacheClosure cl;
901 _nmethod_itr.nmethods_do(&cl);
902 }
903 }
904 };
905
906 void ShenandoahConcurrentGC::op_strong_roots() {
907 ShenandoahHeap* const heap = ShenandoahHeap::heap();
908 assert(heap->is_concurrent_strong_root_in_progress(), "Checked by caller");
909 ShenandoahConcurrentRootsEvacUpdateTask task(ShenandoahPhaseTimings::conc_strong_roots);
910 heap->workers()->run_task(&task);
911 heap->set_concurrent_strong_root_in_progress(false);
912 }
913
914 void ShenandoahConcurrentGC::op_cleanup_early() {
915 ShenandoahHeap::heap()->free_set()->recycle_trash();
916 }
917
918 void ShenandoahConcurrentGC::op_evacuate() {
919 ShenandoahHeap::heap()->evacuate_collection_set(true /*concurrent*/);
920 }
921
922 void ShenandoahConcurrentGC::op_init_updaterefs() {
923 ShenandoahHeap* const heap = ShenandoahHeap::heap();
924 heap->set_evacuation_in_progress(false);
925 heap->set_concurrent_weak_root_in_progress(false);
926 heap->prepare_update_heap_references(true /*concurrent*/);
927 heap->set_update_refs_in_progress(true);
928
929 if (ShenandoahPacing) {
930 heap->pacer()->setup_for_updaterefs();
931 }
932 }
933
934 void ShenandoahConcurrentGC::op_updaterefs() {
935 ShenandoahHeap::heap()->update_heap_references(true /*concurrent*/);
936 }
937
938 class ShenandoahUpdateThreadClosure : public HandshakeClosure {
939 private:
940 ShenandoahUpdateRefsClosure _cl;
941 public:
942 ShenandoahUpdateThreadClosure();
943 void do_thread(Thread* thread);
944 };
945
946 ShenandoahUpdateThreadClosure::ShenandoahUpdateThreadClosure() :
947 HandshakeClosure("Shenandoah Update Thread Roots") {
948 }
949
950 void ShenandoahUpdateThreadClosure::do_thread(Thread* thread) {
951 if (thread->is_Java_thread()) {
952 JavaThread* jt = JavaThread::cast(thread);
953 ResourceMark rm;
954 jt->oops_do(&_cl, nullptr);
955 }
956 }
957
958 void ShenandoahConcurrentGC::op_update_thread_roots() {
959 ShenandoahUpdateThreadClosure cl;
960 Handshake::execute(&cl);
961 }
962
963 void ShenandoahConcurrentGC::op_final_updaterefs() {
964 ShenandoahHeap* const heap = ShenandoahHeap::heap();
965 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at safepoint");
966 assert(!heap->_update_refs_iterator.has_next(), "Should have finished update references");
967
968 heap->finish_concurrent_roots();
969
970 // Clear cancelled GC, if set. On cancellation path, the block before would handle
971 // everything.
972 if (heap->cancelled_gc()) {
973 heap->clear_cancelled_gc();
974 }
975
976 // Has to be done before cset is clear
977 if (ShenandoahVerify) {
978 heap->verifier()->verify_roots_in_to_space();
979 }
980
981 heap->update_heap_region_states(true /*concurrent*/);
982
983 heap->set_update_refs_in_progress(false);
984 heap->set_has_forwarded_objects(false);
985
986 if (ShenandoahVerify) {
987 heap->verifier()->verify_after_updaterefs();
988 }
989
990 if (VerifyAfterGC) {
991 Universe::verify();
992 }
993
994 heap->rebuild_free_set(true /*concurrent*/);
995 }
996
997 void ShenandoahConcurrentGC::op_final_roots() {
998 ShenandoahHeap::heap()->set_concurrent_weak_root_in_progress(false);
999 }
1000
1001 void ShenandoahConcurrentGC::op_cleanup_complete() {
1002 ShenandoahHeap::heap()->free_set()->recycle_trash();
1003 }
1004
1005 bool ShenandoahConcurrentGC::check_cancellation_and_abort(ShenandoahDegenPoint point) {
1006 if (ShenandoahHeap::heap()->cancelled_gc()) {
1007 _degen_point = point;
1008 return true;
1009 }
1010 return false;
1011 }
1012
1013 const char* ShenandoahConcurrentGC::init_mark_event_message() const {
1014 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1015 assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
1016 if (heap->unload_classes()) {
1017 return "Pause Init Mark (unload classes)";
1018 } else {
1019 return "Pause Init Mark";
1020 }
1021 }
1022
1023 const char* ShenandoahConcurrentGC::final_mark_event_message() const {
1024 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1025 assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
1026 if (heap->unload_classes()) {
1027 return "Pause Final Mark (unload classes)";
1028 } else {
1029 return "Pause Final Mark";
1030 }
1031 }
1032
1033 const char* ShenandoahConcurrentGC::conc_mark_event_message() const {
1034 ShenandoahHeap* const heap = ShenandoahHeap::heap();
1035 assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
1036 if (heap->unload_classes()) {
1037 return "Concurrent marking (unload classes)";
1038 } else {
1039 return "Concurrent marking";
1040 }
1041 }