1 /*
2 * Copyright (c) 2013, 2021, 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 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
27 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
28 #include "gc/shenandoah/shenandoahControlThread.hpp"
29 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
30 #include "gc/shenandoah/shenandoahFreeSet.hpp"
31 #include "gc/shenandoah/shenandoahFullGC.hpp"
32 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
33 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
34 #include "gc/shenandoah/shenandoahMark.inline.hpp"
35 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
36 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
37 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
38 #include "gc/shenandoah/shenandoahUtils.hpp"
39 #include "gc/shenandoah/shenandoahVMOperations.hpp"
40 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
41 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
42 #include "memory/iterator.hpp"
43 #include "memory/metaspaceUtils.hpp"
44 #include "memory/metaspaceStats.hpp"
45 #include "memory/universe.hpp"
46 #include "runtime/atomic.hpp"
47
48 ShenandoahControlThread::ShenandoahControlThread() :
49 ConcurrentGCThread(),
50 _alloc_failure_waiters_lock(Mutex::leaf, "ShenandoahAllocFailureGC_lock", Monitor::_safepoint_check_always, true),
51 _gc_waiters_lock(Mutex::leaf, "ShenandoahRequestedGC_lock", Monitor::_safepoint_check_always, true),
52 _periodic_task(this),
53 _requested_gc_cause(GCCause::_no_cause_specified),
54 _degen_point(ShenandoahGC::_degenerated_outside_cycle),
55 _allocs_seen(0) {
56
57 reset_gc_id();
58 create_and_start();
59 _periodic_task.enroll();
60 if (ShenandoahPacing) {
61 _periodic_pacer_notify_task.enroll();
62 }
63 }
64
65 ShenandoahControlThread::~ShenandoahControlThread() {
66 // This is here so that super is called.
67 }
68
69 void ShenandoahPeriodicTask::task() {
70 _thread->handle_force_counters_update();
71 _thread->handle_counters_update();
72 }
73
74 void ShenandoahPeriodicPacerNotify::task() {
75 assert(ShenandoahPacing, "Should not be here otherwise");
76 ShenandoahHeap::heap()->pacer()->notify_waiters();
77 }
78
79 void ShenandoahControlThread::run_service() {
80 ShenandoahHeap* heap = ShenandoahHeap::heap();
81
82 GCMode default_mode = concurrent_normal;
83 GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
84 int sleep = ShenandoahControlIntervalMin;
85
86 double last_shrink_time = os::elapsedTime();
87 double last_sleep_adjust_time = os::elapsedTime();
88
89 // Shrink period avoids constantly polling regions for shrinking.
90 // Having a period 10x lower than the delay would mean we hit the
91 // shrinking with lag of less than 1/10-th of true delay.
92 // ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
93 double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
94
95 ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
96 ShenandoahHeuristics* heuristics = heap->heuristics();
97 while (!in_graceful_shutdown() && !should_terminate()) {
98 // Figure out if we have pending requests.
99 bool alloc_failure_pending = _alloc_failure_gc.is_set();
100 bool explicit_gc_requested = _gc_requested.is_set() && is_explicit_gc(_requested_gc_cause);
101 bool implicit_gc_requested = _gc_requested.is_set() && !is_explicit_gc(_requested_gc_cause);
102
103 // This control loop iteration have seen this much allocations.
104 size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
105
106 // Check if we have seen a new target for soft max heap size.
107 bool soft_max_changed = check_soft_max_changed();
108
109 // Choose which GC mode to run in. The block below should select a single mode.
110 GCMode mode = none;
111 GCCause::Cause cause = GCCause::_last_gc_cause;
112 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset;
113
114 if (alloc_failure_pending) {
115 // Allocation failure takes precedence: we have to deal with it first thing
116 log_info(gc)("Trigger: Handle Allocation Failure");
117
118 cause = GCCause::_allocation_failure;
119
120 // Consume the degen point, and seed it with default value
121 degen_point = _degen_point;
122 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
123
124 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle()) {
125 heuristics->record_allocation_failure_gc();
126 policy->record_alloc_failure_to_degenerated(degen_point);
127 mode = stw_degenerated;
128 } else {
129 heuristics->record_allocation_failure_gc();
130 policy->record_alloc_failure_to_full();
131 mode = stw_full;
132 }
133
134 } else if (explicit_gc_requested) {
135 cause = _requested_gc_cause;
136 log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));
137
138 heuristics->record_requested_gc();
139
140 if (ExplicitGCInvokesConcurrent) {
141 policy->record_explicit_to_concurrent();
142 mode = default_mode;
143 // Unload and clean up everything
144 heap->set_unload_classes(heuristics->can_unload_classes());
145 } else {
146 policy->record_explicit_to_full();
147 mode = stw_full;
148 }
149 } else if (implicit_gc_requested) {
150 cause = _requested_gc_cause;
151 log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));
152
153 heuristics->record_requested_gc();
154
155 if (ShenandoahImplicitGCInvokesConcurrent) {
156 policy->record_implicit_to_concurrent();
157 mode = default_mode;
158
159 // Unload and clean up everything
160 heap->set_unload_classes(heuristics->can_unload_classes());
161 } else {
162 policy->record_implicit_to_full();
163 mode = stw_full;
164 }
165 } else {
166 // Potential normal cycle: ask heuristics if it wants to act
167 if (heuristics->should_start_gc()) {
168 mode = default_mode;
169 cause = default_cause;
170 }
171
172 // Ask policy if this cycle wants to process references or unload classes
173 heap->set_unload_classes(heuristics->should_unload_classes());
174 }
175
176 // Blow all soft references on this cycle, if handling allocation failure,
177 // either implicit or explicit GC request, or we are requested to do so unconditionally.
178 if (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs) {
179 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
180 }
181
182 bool gc_requested = (mode != none);
183 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");
184
185 if (gc_requested) {
186 // GC is starting, bump the internal ID
187 update_gc_id();
188
189 heap->reset_bytes_allocated_since_gc_start();
190
191 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics();
192
193 // If GC was requested, we are sampling the counters even without actual triggers
194 // from allocation machinery. This captures GC phases more accurately.
195 set_forced_counters_update(true);
196
197 // If GC was requested, we better dump freeset data for performance debugging
198 {
199 ShenandoahHeapLocker locker(heap->lock());
200 heap->free_set()->log_status();
201 }
202
203 switch (mode) {
204 case concurrent_normal:
205 service_concurrent_normal_cycle(cause);
206 break;
207 case stw_degenerated:
208 service_stw_degenerated_cycle(cause, degen_point);
209 break;
210 case stw_full:
211 service_stw_full_cycle(cause);
212 break;
213 default:
214 ShouldNotReachHere();
215 }
216
217 // If this was the requested GC cycle, notify waiters about it
218 if (explicit_gc_requested || implicit_gc_requested) {
219 notify_gc_waiters();
220 }
221
222 // If this was the allocation failure GC cycle, notify waiters about it
223 if (alloc_failure_pending) {
224 notify_alloc_failure_waiters();
225 }
226
227 // Report current free set state at the end of cycle, whether
228 // it is a normal completion, or the abort.
229 {
230 ShenandoahHeapLocker locker(heap->lock());
231 heap->free_set()->log_status();
232
233 // Notify Universe about new heap usage. This has implications for
234 // global soft refs policy, and we better report it every time heap
235 // usage goes down.
236 Universe::heap()->update_capacity_and_used_at_gc();
237
238 // Signal that we have completed a visit to all live objects.
239 Universe::heap()->record_whole_heap_examined_timestamp();
240 }
241
242 // Disable forced counters update, and update counters one more time
243 // to capture the state at the end of GC session.
244 handle_force_counters_update();
245 set_forced_counters_update(false);
246
247 // Retract forceful part of soft refs policy
248 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false);
249
250 // Clear metaspace oom flag, if current cycle unloaded classes
251 if (heap->unload_classes()) {
252 heuristics->clear_metaspace_oom();
253 }
254
255 // Commit worker statistics to cycle data
256 heap->phase_timings()->flush_par_workers_to_cycle();
257 if (ShenandoahPacing) {
258 heap->pacer()->flush_stats_to_cycle();
259 }
260
261 // Print GC stats for current cycle
262 {
263 LogTarget(Info, gc, stats) lt;
264 if (lt.is_enabled()) {
265 ResourceMark rm;
266 LogStream ls(lt);
267 heap->phase_timings()->print_cycle_on(&ls);
268 if (ShenandoahPacing) {
269 heap->pacer()->print_cycle_on(&ls);
270 }
271 }
272 }
273
274 // Commit statistics to globals
275 heap->phase_timings()->flush_cycle_to_global();
276
277 // Print Metaspace change following GC (if logging is enabled).
278 MetaspaceUtils::print_metaspace_change(meta_sizes);
279
280 // GC is over, we are at idle now
281 if (ShenandoahPacing) {
282 heap->pacer()->setup_for_idle();
283 }
284 } else {
285 // Allow allocators to know we have seen this much regions
286 if (ShenandoahPacing && (allocs_seen > 0)) {
287 heap->pacer()->report_alloc(allocs_seen);
288 }
289 }
290
291 double current = os::elapsedTime();
292
293 if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
294 // Explicit GC tries to uncommit everything down to min capacity.
295 // Soft max change tries to uncommit everything down to target capacity.
296 // Periodic uncommit tries to uncommit suitable regions down to min capacity.
297
298 double shrink_before = (explicit_gc_requested || soft_max_changed) ?
299 current :
300 current - (ShenandoahUncommitDelay / 1000.0);
301
302 size_t shrink_until = soft_max_changed ?
303 heap->soft_max_capacity() :
304 heap->min_capacity();
305
306 service_uncommit(shrink_before, shrink_until);
307 heap->phase_timings()->flush_cycle_to_global();
308 last_shrink_time = current;
309 }
310
311 // Wait before performing the next action. If allocation happened during this wait,
312 // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
313 // back off exponentially.
314 if (_heap_changed.try_unset()) {
315 sleep = ShenandoahControlIntervalMin;
316 } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
317 sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2));
318 last_sleep_adjust_time = current;
319 }
320 os::naked_short_sleep(sleep);
321 }
322
323 // Wait for the actual stop(), can't leave run_service() earlier.
324 while (!should_terminate()) {
325 os::naked_short_sleep(ShenandoahControlIntervalMin);
326 }
327 }
328
329 bool ShenandoahControlThread::check_soft_max_changed() const {
330 ShenandoahHeap* heap = ShenandoahHeap::heap();
331 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
332 size_t old_soft_max = heap->soft_max_capacity();
333 if (new_soft_max != old_soft_max) {
334 new_soft_max = MAX2(heap->min_capacity(), new_soft_max);
335 new_soft_max = MIN2(heap->max_capacity(), new_soft_max);
336 if (new_soft_max != old_soft_max) {
337 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
338 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
339 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
340 );
341 heap->set_soft_max_capacity(new_soft_max);
342 return true;
343 }
344 }
345 return false;
346 }
347
348 void ShenandoahControlThread::service_concurrent_normal_cycle(GCCause::Cause cause) {
349 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during
350 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there.
351 // If second allocation failure happens during Degenerated GC cycle (for example, when GC
352 // tries to evac something and no memory is available), cycle degrades to Full GC.
353 //
354 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when
355 // heuristics says there are no regions to compact, and all the collection comes from immediately
356 // reclaimable regions.
357 //
358 // ................................................................................................
359 //
360 // (immediate garbage shortcut) Concurrent GC
361 // /-------------------------------------------\
362 // | |
363 // | |
364 // | |
365 // | v
366 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END]
367 // | | | ^
368 // | (af) | (af) | (af) |
369 // ..................|....................|.................|..............|.......................
370 // | | | |
371 // | | | | Degenerated GC
372 // v v v |
373 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o
374 // | | | ^
375 // | (af) | (af) | (af) |
376 // ..................|....................|.................|..............|.......................
377 // | | | |
378 // | v | | Full GC
379 // \------------------->o<----------------/ |
380 // | |
381 // v |
382 // Full GC --------------------------/
383 //
384 ShenandoahHeap* heap = ShenandoahHeap::heap();
385 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
386
387 GCIdMark gc_id_mark;
388 ShenandoahGCSession session(cause);
389
390 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
391
392 ShenandoahConcurrentGC gc;
393 if (gc.collect(cause)) {
394 // Cycle is complete
395 heap->heuristics()->record_success_concurrent();
396 heap->shenandoah_policy()->record_success_concurrent();
397 } else {
398 assert(heap->cancelled_gc(), "Must have been cancelled");
399 check_cancellation_or_degen(gc.degen_point());
400 }
401 }
402
403 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) {
404 ShenandoahHeap* heap = ShenandoahHeap::heap();
405 if (heap->cancelled_gc()) {
406 assert (is_alloc_failure_gc() || in_graceful_shutdown(), "Cancel GC either for alloc failure GC, or gracefully exiting");
407 if (!in_graceful_shutdown()) {
408 assert (_degen_point == ShenandoahGC::_degenerated_outside_cycle,
409 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point));
410 _degen_point = point;
411 }
412 return true;
413 }
414 return false;
415 }
416
417 void ShenandoahControlThread::stop_service() {
418 // Nothing to do here.
419 }
420
421 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) {
422 GCIdMark gc_id_mark;
423 ShenandoahGCSession session(cause);
424
425 ShenandoahFullGC gc;
426 gc.collect(cause);
427
428 ShenandoahHeap* const heap = ShenandoahHeap::heap();
429 heap->heuristics()->record_success_full();
430 heap->shenandoah_policy()->record_success_full();
431 }
432
433 void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) {
434 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set");
435
436 GCIdMark gc_id_mark;
437 ShenandoahGCSession session(cause);
438
439 ShenandoahDegenGC gc(point);
440 gc.collect(cause);
441
442 ShenandoahHeap* const heap = ShenandoahHeap::heap();
443 heap->heuristics()->record_success_degenerated();
444 heap->shenandoah_policy()->record_success_degenerated();
445 }
446
447 void ShenandoahControlThread::service_uncommit(double shrink_before, size_t shrink_until) {
448 ShenandoahHeap* heap = ShenandoahHeap::heap();
449
450 // Determine if there is work to do. This avoids taking heap lock if there is
451 // no work available, avoids spamming logs with superfluous logging messages,
452 // and minimises the amount of work while locks are taken.
453
454 if (heap->committed() <= shrink_until) return;
455
456 bool has_work = false;
457 for (size_t i = 0; i < heap->num_regions(); i++) {
458 ShenandoahHeapRegion *r = heap->get_region(i);
459 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
460 has_work = true;
461 break;
462 }
463 }
464
465 if (has_work) {
466 heap->entry_uncommit(shrink_before, shrink_until);
467 }
468 }
469
470 bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
471 return GCCause::is_user_requested_gc(cause) ||
472 GCCause::is_serviceability_requested_gc(cause);
473 }
474
475 void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
476 assert(GCCause::is_user_requested_gc(cause) ||
477 GCCause::is_serviceability_requested_gc(cause) ||
478 cause == GCCause::_metadata_GC_clear_soft_refs ||
479 cause == GCCause::_full_gc_alot ||
480 cause == GCCause::_wb_full_gc ||
481 cause == GCCause::_wb_breakpoint ||
482 cause == GCCause::_scavenge_alot,
483 "only requested GCs here");
484
485 if (is_explicit_gc(cause)) {
486 if (!DisableExplicitGC) {
487 handle_requested_gc(cause);
488 }
489 } else {
490 handle_requested_gc(cause);
491 }
492 }
493
494 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
495 // Make sure we have at least one complete GC cycle before unblocking
496 // from the explicit GC request.
497 //
498 // This is especially important for weak references cleanup and/or native
499 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request
500 // comes very late in the already running cycle, it would miss lots of new
501 // opportunities for cleanup that were made available before the caller
502 // requested the GC.
503
504 MonitorLocker ml(&_gc_waiters_lock);
505 size_t current_gc_id = get_gc_id();
506 size_t required_gc_id = current_gc_id + 1;
507 while (current_gc_id < required_gc_id) {
508 _gc_requested.set();
509 _requested_gc_cause = cause;
510
511 if (cause != GCCause::_wb_breakpoint) {
512 ml.wait();
513 }
514 current_gc_id = get_gc_id();
515 }
516 }
517
518 void ShenandoahControlThread::handle_alloc_failure(ShenandoahAllocRequest& req) {
519 ShenandoahHeap* heap = ShenandoahHeap::heap();
520
521 assert(current()->is_Java_thread(), "expect Java thread here");
522
523 if (try_set_alloc_failure_gc()) {
524 // Only report the first allocation failure
525 log_info(gc)("Failed to allocate %s, " SIZE_FORMAT "%s",
526 req.type_string(),
527 byte_size_in_proper_unit(req.size() * HeapWordSize), proper_unit_for_byte_size(req.size() * HeapWordSize));
528
529 // Now that alloc failure GC is scheduled, we can abort everything else
530 heap->cancel_gc(GCCause::_allocation_failure);
531 }
532
533 MonitorLocker ml(&_alloc_failure_waiters_lock);
534 while (is_alloc_failure_gc()) {
535 ml.wait();
536 }
537 }
538
539 void ShenandoahControlThread::handle_alloc_failure_evac(size_t words) {
540 ShenandoahHeap* heap = ShenandoahHeap::heap();
541
542 if (try_set_alloc_failure_gc()) {
543 // Only report the first allocation failure
544 log_info(gc)("Failed to allocate " SIZE_FORMAT "%s for evacuation",
545 byte_size_in_proper_unit(words * HeapWordSize), proper_unit_for_byte_size(words * HeapWordSize));
546 }
547
548 // Forcefully report allocation failure
549 heap->cancel_gc(GCCause::_shenandoah_allocation_failure_evac);
550 }
551
552 void ShenandoahControlThread::notify_alloc_failure_waiters() {
553 _alloc_failure_gc.unset();
554 MonitorLocker ml(&_alloc_failure_waiters_lock);
555 ml.notify_all();
556 }
557
558 bool ShenandoahControlThread::try_set_alloc_failure_gc() {
559 return _alloc_failure_gc.try_set();
560 }
561
562 bool ShenandoahControlThread::is_alloc_failure_gc() {
563 return _alloc_failure_gc.is_set();
564 }
565
566 void ShenandoahControlThread::notify_gc_waiters() {
567 _gc_requested.unset();
568 MonitorLocker ml(&_gc_waiters_lock);
569 ml.notify_all();
570 }
571
572 void ShenandoahControlThread::handle_counters_update() {
573 if (_do_counters_update.is_set()) {
574 _do_counters_update.unset();
575 ShenandoahHeap::heap()->monitoring_support()->update_counters();
576 }
577 }
578
579 void ShenandoahControlThread::handle_force_counters_update() {
580 if (_force_counters_update.is_set()) {
581 _do_counters_update.unset(); // reset these too, we do update now!
582 ShenandoahHeap::heap()->monitoring_support()->update_counters();
583 }
584 }
585
586 void ShenandoahControlThread::notify_heap_changed() {
587 // This is called from allocation path, and thus should be fast.
588
589 // Update monitoring counters when we took a new region. This amortizes the
590 // update costs on slow path.
591 if (_do_counters_update.is_unset()) {
592 _do_counters_update.set();
593 }
594 // Notify that something had changed.
595 if (_heap_changed.is_unset()) {
596 _heap_changed.set();
597 }
598 }
599
600 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
601 assert(ShenandoahPacing, "should only call when pacing is enabled");
602 Atomic::add(&_allocs_seen, words, memory_order_relaxed);
603 }
604
605 void ShenandoahControlThread::set_forced_counters_update(bool value) {
606 _force_counters_update.set_cond(value);
607 }
608
609 void ShenandoahControlThread::reset_gc_id() {
610 Atomic::store(&_gc_id, (size_t)0);
611 }
612
613 void ShenandoahControlThread::update_gc_id() {
614 Atomic::inc(&_gc_id);
615 }
616
617 size_t ShenandoahControlThread::get_gc_id() {
618 return Atomic::load(&_gc_id);
619 }
620
621 void ShenandoahControlThread::print() const {
622 print_on(tty);
623 }
624
625 void ShenandoahControlThread::print_on(outputStream* st) const {
626 st->print("Shenandoah Concurrent Thread");
627 Thread::print_on(st);
628 st->cr();
629 }
630
631 void ShenandoahControlThread::start() {
632 create_and_start();
633 }
634
635 void ShenandoahControlThread::prepare_for_graceful_shutdown() {
636 _graceful_shutdown.set();
637 }
638
639 bool ShenandoahControlThread::in_graceful_shutdown() {
640 return _graceful_shutdown.is_set();
641 }