1 /*
2 * Copyright Amazon.com Inc. or its affiliates. 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
26 #include "precompiled.hpp"
27
28 #include "gc/shared/strongRootsScope.hpp"
29 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
30 #include "gc/shenandoah/shenandoahAsserts.hpp"
31 #include "gc/shenandoah/shenandoahCardTable.hpp"
32 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
33 #include "gc/shenandoah/shenandoahFreeSet.hpp"
34 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
35 #include "gc/shenandoah/shenandoahHeap.hpp"
36 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
37 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
38 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
39 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
40 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
41 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
42 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
43 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
44 #include "gc/shenandoah/shenandoahUtils.hpp"
45 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
46 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
47 #include "runtime/threads.hpp"
48 #include "utilities/events.hpp"
49
50 class ShenandoahFlushAllSATB : public ThreadClosure {
51 private:
52 SATBMarkQueueSet& _satb_qset;
53
54 public:
55 explicit ShenandoahFlushAllSATB(SATBMarkQueueSet& satb_qset) :
56 _satb_qset(satb_qset) {}
57
58 void do_thread(Thread* thread) override {
59 // Transfer any partial buffer to the qset for completed buffer processing.
60 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
61 }
62 };
63
64 class ShenandoahProcessOldSATB : public SATBBufferClosure {
65 private:
66 ShenandoahObjToScanQueue* _queue;
67 ShenandoahHeap* _heap;
68 ShenandoahMarkingContext* const _mark_context;
69 size_t _trashed_oops;
70
71 public:
72 explicit ShenandoahProcessOldSATB(ShenandoahObjToScanQueue* q) :
73 _queue(q),
74 _heap(ShenandoahHeap::heap()),
75 _mark_context(_heap->marking_context()),
76 _trashed_oops(0) {}
77
78 void do_buffer(void** buffer, size_t size) override {
79 assert(size == 0 || !_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded objects are not expected here");
80 for (size_t i = 0; i < size; ++i) {
81 oop *p = (oop *) &buffer[i];
82 ShenandoahHeapRegion* region = _heap->heap_region_containing(*p);
83 if (region->is_old() && region->is_active()) {
84 ShenandoahMark::mark_through_ref<oop, OLD>(p, _queue, nullptr, _mark_context, false);
85 } else {
86 _trashed_oops++;
87 }
88 }
89 }
90
91 size_t trashed_oops() const {
92 return _trashed_oops;
93 }
94 };
95
96 class ShenandoahPurgeSATBTask : public WorkerTask {
97 private:
98 ShenandoahObjToScanQueueSet* _mark_queues;
99 volatile size_t _trashed_oops;
100
101 public:
102 explicit ShenandoahPurgeSATBTask(ShenandoahObjToScanQueueSet* queues) :
103 WorkerTask("Purge SATB"),
104 _mark_queues(queues),
105 _trashed_oops(0) {
106 Threads::change_thread_claim_token();
107 }
108
109 ~ShenandoahPurgeSATBTask() {
110 if (_trashed_oops > 0) {
111 log_debug(gc)("Purged " SIZE_FORMAT " oops from old generation SATB buffers", _trashed_oops);
112 }
113 }
114
115 void work(uint worker_id) override {
116 ShenandoahParallelWorkerSession worker_session(worker_id);
117 ShenandoahSATBMarkQueueSet &satb_queues = ShenandoahBarrierSet::satb_mark_queue_set();
118 ShenandoahFlushAllSATB flusher(satb_queues);
119 Threads::possibly_parallel_threads_do(true /* is_par */, &flusher);
120
121 ShenandoahObjToScanQueue* mark_queue = _mark_queues->queue(worker_id);
122 ShenandoahProcessOldSATB processor(mark_queue);
123 while (satb_queues.apply_closure_to_completed_buffer(&processor)) {}
124
125 Atomic::add(&_trashed_oops, processor.trashed_oops());
126 }
127 };
128
129 class ShenandoahConcurrentCoalesceAndFillTask : public WorkerTask {
130 private:
131 uint _nworkers;
132 ShenandoahHeapRegion** _coalesce_and_fill_region_array;
133 uint _coalesce_and_fill_region_count;
134 volatile bool _is_preempted;
135
136 public:
137 ShenandoahConcurrentCoalesceAndFillTask(uint nworkers,
138 ShenandoahHeapRegion** coalesce_and_fill_region_array,
139 uint region_count) :
140 WorkerTask("Shenandoah Concurrent Coalesce and Fill"),
141 _nworkers(nworkers),
142 _coalesce_and_fill_region_array(coalesce_and_fill_region_array),
143 _coalesce_and_fill_region_count(region_count),
144 _is_preempted(false) {
145 }
146
147 void work(uint worker_id) override {
148 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_coalesce_and_fill, ShenandoahPhaseTimings::ScanClusters, worker_id);
149 for (uint region_idx = worker_id; region_idx < _coalesce_and_fill_region_count; region_idx += _nworkers) {
150 ShenandoahHeapRegion* r = _coalesce_and_fill_region_array[region_idx];
151 if (r->is_humongous()) {
152 // There is only one object in this region and it is not garbage,
153 // so no need to coalesce or fill.
154 continue;
155 }
156
157 if (!r->oop_coalesce_and_fill(true)) {
158 // Coalesce and fill has been preempted
159 Atomic::store(&_is_preempted, true);
160 return;
161 }
162 }
163 }
164
165 // Value returned from is_completed() is only valid after all worker thread have terminated.
166 bool is_completed() {
167 return !Atomic::load(&_is_preempted);
168 }
169 };
170
171 ShenandoahOldGeneration::ShenandoahOldGeneration(uint max_queues, size_t max_capacity, size_t soft_max_capacity)
172 : ShenandoahGeneration(OLD, max_queues, max_capacity, soft_max_capacity),
173 _coalesce_and_fill_region_array(NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, ShenandoahHeap::heap()->num_regions(), mtGC)),
174 _old_heuristics(nullptr),
175 _region_balance(0),
176 _promoted_reserve(0),
177 _promoted_expended(0),
178 _promotion_potential(0),
179 _pad_for_promote_in_place(0),
180 _promotable_humongous_regions(0),
181 _promotable_regular_regions(0),
182 _is_parsable(true),
183 _card_scan(nullptr),
184 _state(WAITING_FOR_BOOTSTRAP),
185 _growth_before_compaction(INITIAL_GROWTH_BEFORE_COMPACTION),
186 _min_growth_before_compaction ((ShenandoahMinOldGenGrowthPercent * FRACTIONAL_DENOMINATOR) / 100)
187 {
188 _live_bytes_after_last_mark = ShenandoahHeap::heap()->capacity() * INITIAL_LIVE_FRACTION / FRACTIONAL_DENOMINATOR;
189 // Always clear references for old generation
190 ref_processor()->set_soft_reference_policy(true);
191
192 if (ShenandoahCardBarrier) {
193 ShenandoahCardTable* card_table = ShenandoahBarrierSet::barrier_set()->card_table();
194 size_t card_count = card_table->cards_required(ShenandoahHeap::heap()->reserved_region().word_size());
195 auto rs = new ShenandoahDirectCardMarkRememberedSet(card_table, card_count);
196 _card_scan = new ShenandoahScanRemembered(rs);
197 }
198 }
199
200 void ShenandoahOldGeneration::set_promoted_reserve(size_t new_val) {
201 shenandoah_assert_heaplocked_or_safepoint();
202 _promoted_reserve = new_val;
203 }
204
205 size_t ShenandoahOldGeneration::get_promoted_reserve() const {
206 return _promoted_reserve;
207 }
208
209 void ShenandoahOldGeneration::augment_promoted_reserve(size_t increment) {
210 shenandoah_assert_heaplocked_or_safepoint();
211 _promoted_reserve += increment;
212 }
213
214 void ShenandoahOldGeneration::reset_promoted_expended() {
215 shenandoah_assert_heaplocked_or_safepoint();
216 Atomic::store(&_promoted_expended, (size_t) 0);
217 }
218
219 size_t ShenandoahOldGeneration::expend_promoted(size_t increment) {
220 shenandoah_assert_heaplocked_or_safepoint();
221 assert(get_promoted_expended() + increment <= get_promoted_reserve(), "Do not expend more promotion than budgeted");
222 return Atomic::add(&_promoted_expended, increment);
223 }
224
225 size_t ShenandoahOldGeneration::unexpend_promoted(size_t decrement) {
226 return Atomic::sub(&_promoted_expended, decrement);
227 }
228
229 size_t ShenandoahOldGeneration::get_promoted_expended() const {
230 return Atomic::load(&_promoted_expended);
231 }
232
233 bool ShenandoahOldGeneration::can_allocate(const ShenandoahAllocRequest &req) const {
234 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "GCLAB pertains only to young-gen memory");
235
236 const size_t requested_bytes = req.size() * HeapWordSize;
237 // The promotion reserve may also be used for evacuations. If we can promote this object,
238 // then we can also evacuate it.
239 if (can_promote(requested_bytes)) {
240 // The promotion reserve should be able to accommodate this request. The request
241 // might still fail if alignment with the card table increases the size. The request
242 // may also fail if the heap is badly fragmented and the free set cannot find room for it.
243 return true;
244 }
245
246 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
247 // The promotion reserve cannot accommodate this plab request. Check if we still have room for
248 // evacuations. Note that we cannot really know how much of the plab will be used for evacuations,
249 // so here we only check that some evacuation reserve still exists.
250 return get_evacuation_reserve() > 0;
251 }
252
253 // This is a shared allocation request. We've already checked that it can't be promoted, so if
254 // it is a promotion, we return false. Otherwise, it is a shared evacuation request, and we allow
255 // the allocation to proceed.
256 return !req.is_promotion();
257 }
258
259 void
260 ShenandoahOldGeneration::configure_plab_for_current_thread(const ShenandoahAllocRequest &req) {
261 // Note: Even when a mutator is performing a promotion outside a LAB, we use a 'shared_gc' request.
262 if (req.is_gc_alloc()) {
263 const size_t actual_size = req.actual_size() * HeapWordSize;
264 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
265 // We've created a new plab. Now we configure it whether it will be used for promotions
266 // and evacuations - or just evacuations.
267 Thread* thread = Thread::current();
268 ShenandoahThreadLocalData::reset_plab_promoted(thread);
269
270 // The actual size of the allocation may be larger than the requested bytes (due to alignment on card boundaries).
271 // If this puts us over our promotion budget, we need to disable future PLAB promotions for this thread.
272 if (can_promote(actual_size)) {
273 // Assume the entirety of this PLAB will be used for promotion. This prevents promotion from overreach.
274 // When we retire this plab, we'll unexpend what we don't really use.
275 expend_promoted(actual_size);
276 ShenandoahThreadLocalData::enable_plab_promotions(thread);
277 ShenandoahThreadLocalData::set_plab_actual_size(thread, actual_size);
278 } else {
279 // Disable promotions in this thread because entirety of this PLAB must be available to hold old-gen evacuations.
280 ShenandoahThreadLocalData::disable_plab_promotions(thread);
281 ShenandoahThreadLocalData::set_plab_actual_size(thread, 0);
282 }
283 } else if (req.is_promotion()) {
284 // Shared promotion.
285 expend_promoted(actual_size);
286 }
287 }
288 }
289
290 size_t ShenandoahOldGeneration::get_live_bytes_after_last_mark() const {
291 return _live_bytes_after_last_mark;
292 }
293
294 void ShenandoahOldGeneration::set_live_bytes_after_last_mark(size_t bytes) {
295 if (bytes == 0) {
296 // Restart search for best old-gen size to the initial state
297 _live_bytes_after_last_mark = ShenandoahHeap::heap()->capacity() * INITIAL_LIVE_FRACTION / FRACTIONAL_DENOMINATOR;
298 _growth_before_compaction = INITIAL_GROWTH_BEFORE_COMPACTION;
299 } else {
300 _live_bytes_after_last_mark = bytes;
301 _growth_before_compaction /= 2;
302 if (_growth_before_compaction < _min_growth_before_compaction) {
303 _growth_before_compaction = _min_growth_before_compaction;
304 }
305 }
306 }
307
308 void ShenandoahOldGeneration::handle_failed_transfer() {
309 _old_heuristics->trigger_cannot_expand();
310 }
311
312 size_t ShenandoahOldGeneration::usage_trigger_threshold() const {
313 size_t result = _live_bytes_after_last_mark + (_live_bytes_after_last_mark * _growth_before_compaction) / FRACTIONAL_DENOMINATOR;
314 return result;
315 }
316
317 bool ShenandoahOldGeneration::contains(ShenandoahAffiliation affiliation) const {
318 return affiliation == OLD_GENERATION;
319 }
320 bool ShenandoahOldGeneration::contains(ShenandoahHeapRegion* region) const {
321 return region->is_old();
322 }
323
324 void ShenandoahOldGeneration::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* cl) {
325 ShenandoahIncludeRegionClosure<OLD_GENERATION> old_regions_cl(cl);
326 ShenandoahHeap::heap()->parallel_heap_region_iterate(&old_regions_cl);
327 }
328
329 void ShenandoahOldGeneration::heap_region_iterate(ShenandoahHeapRegionClosure* cl) {
330 ShenandoahIncludeRegionClosure<OLD_GENERATION> old_regions_cl(cl);
331 ShenandoahHeap::heap()->heap_region_iterate(&old_regions_cl);
332 }
333
334 void ShenandoahOldGeneration::set_concurrent_mark_in_progress(bool in_progress) {
335 ShenandoahHeap::heap()->set_concurrent_old_mark_in_progress(in_progress);
336 }
337
338 bool ShenandoahOldGeneration::is_concurrent_mark_in_progress() {
339 return ShenandoahHeap::heap()->is_concurrent_old_mark_in_progress();
340 }
341
342 void ShenandoahOldGeneration::cancel_marking() {
343 if (is_concurrent_mark_in_progress()) {
344 log_debug(gc)("Abandon SATB buffers");
345 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
346 }
347
348 ShenandoahGeneration::cancel_marking();
349 }
350
351 void ShenandoahOldGeneration::cancel_gc() {
352 shenandoah_assert_safepoint();
353 if (is_idle()) {
354 #ifdef ASSERT
355 validate_waiting_for_bootstrap();
356 #endif
357 } else {
358 log_info(gc)("Terminating old gc cycle.");
359 // Stop marking
360 cancel_marking();
361 // Stop tracking old regions
362 abandon_collection_candidates();
363 // Remove old generation access to young generation mark queues
364 ShenandoahHeap::heap()->young_generation()->set_old_gen_task_queues(nullptr);
365 // Transition to IDLE now.
366 transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP);
367 }
368 }
369
370 void ShenandoahOldGeneration::prepare_gc() {
371 // Now that we have made the old generation parsable, it is safe to reset the mark bitmap.
372 assert(state() != FILLING, "Cannot reset old without making it parsable");
373
374 ShenandoahGeneration::prepare_gc();
375 }
376
377 bool ShenandoahOldGeneration::entry_coalesce_and_fill() {
378 ShenandoahHeap* const heap = ShenandoahHeap::heap();
379
380 static const char* msg = "Coalescing and filling (Old)";
381 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_coalesce_and_fill);
382
383 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
384 EventMark em("%s", msg);
385 ShenandoahWorkerScope scope(heap->workers(),
386 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
387 msg);
388
389 return coalesce_and_fill();
390 }
391
392 // Make the old generation regions parsable, so they can be safely
393 // scanned when looking for objects in memory indicated by dirty cards.
394 bool ShenandoahOldGeneration::coalesce_and_fill() {
395 transition_to(FILLING);
396
397 // This code will see the same set of regions to fill on each resumption as it did
398 // on the initial run. That's okay because each region keeps track of its own coalesce
399 // and fill state. Regions that were filled on a prior attempt will not try to fill again.
400 uint coalesce_and_fill_regions_count = _old_heuristics->get_coalesce_and_fill_candidates(_coalesce_and_fill_region_array);
401 assert(coalesce_and_fill_regions_count <= ShenandoahHeap::heap()->num_regions(), "Sanity");
402 if (coalesce_and_fill_regions_count == 0) {
403 // No regions need to be filled.
404 abandon_collection_candidates();
405 return true;
406 }
407
408 ShenandoahHeap* const heap = ShenandoahHeap::heap();
409 WorkerThreads* workers = heap->workers();
410 uint nworkers = workers->active_workers();
411 ShenandoahConcurrentCoalesceAndFillTask task(nworkers, _coalesce_and_fill_region_array, coalesce_and_fill_regions_count);
412
413 log_debug(gc)("Starting (or resuming) coalesce-and-fill of " UINT32_FORMAT " old heap regions", coalesce_and_fill_regions_count);
414 workers->run_task(&task);
415 if (task.is_completed()) {
416 // We no longer need to track regions that need to be coalesced and filled.
417 abandon_collection_candidates();
418 return true;
419 } else {
420 // Coalesce-and-fill has been preempted. We'll finish that effort in the future. Do not invoke
421 // ShenandoahGeneration::prepare_gc() until coalesce-and-fill is done because it resets the mark bitmap
422 // and invokes set_mark_incomplete(). Coalesce-and-fill depends on the mark bitmap.
423 log_debug(gc)("Suspending coalesce-and-fill of old heap regions");
424 return false;
425 }
426 }
427
428 void ShenandoahOldGeneration::transfer_pointers_from_satb() {
429 ShenandoahHeap* heap = ShenandoahHeap::heap();
430 shenandoah_assert_safepoint();
431 assert(heap->is_concurrent_old_mark_in_progress(), "Only necessary during old marking.");
432 log_debug(gc)("Transfer SATB buffers");
433 uint nworkers = heap->workers()->active_workers();
434 StrongRootsScope scope(nworkers);
435
436 ShenandoahPurgeSATBTask purge_satb_task(task_queues());
437 heap->workers()->run_task(&purge_satb_task);
438 }
439
440 bool ShenandoahOldGeneration::contains(oop obj) const {
441 return ShenandoahHeap::heap()->is_in_old(obj);
442 }
443
444 void ShenandoahOldGeneration::prepare_regions_and_collection_set(bool concurrent) {
445 ShenandoahHeap* heap = ShenandoahHeap::heap();
446 assert(!heap->is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
447
448 {
449 ShenandoahGCPhase phase(concurrent ?
450 ShenandoahPhaseTimings::final_update_region_states :
451 ShenandoahPhaseTimings::degen_gc_final_update_region_states);
452 ShenandoahFinalMarkUpdateRegionStateClosure cl(complete_marking_context());
453
454 parallel_heap_region_iterate(&cl);
455 heap->assert_pinned_region_status();
456 }
457
458 {
459 // This doesn't actually choose a collection set, but prepares a list of
460 // regions as 'candidates' for inclusion in a mixed collection.
461 ShenandoahGCPhase phase(concurrent ?
462 ShenandoahPhaseTimings::choose_cset :
463 ShenandoahPhaseTimings::degen_gc_choose_cset);
464 ShenandoahHeapLocker locker(heap->lock());
465 _old_heuristics->prepare_for_old_collections();
466 }
467
468 {
469 // Though we did not choose a collection set above, we still may have
470 // freed up immediate garbage regions so proceed with rebuilding the free set.
471 ShenandoahGCPhase phase(concurrent ?
472 ShenandoahPhaseTimings::final_rebuild_freeset :
473 ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
474 ShenandoahHeapLocker locker(heap->lock());
475 size_t cset_young_regions, cset_old_regions;
476 size_t first_old, last_old, num_old;
477 heap->free_set()->prepare_to_rebuild(cset_young_regions, cset_old_regions, first_old, last_old, num_old);
478 // This is just old-gen completion. No future budgeting required here. The only reason to rebuild the freeset here
479 // is in case there was any immediate old garbage identified.
480 heap->free_set()->finish_rebuild(cset_young_regions, cset_old_regions, num_old);
481 }
482 }
483
484 const char* ShenandoahOldGeneration::state_name(State state) {
485 switch (state) {
486 case WAITING_FOR_BOOTSTRAP: return "Waiting for Bootstrap";
487 case FILLING: return "Coalescing";
488 case BOOTSTRAPPING: return "Bootstrapping";
489 case MARKING: return "Marking";
490 case EVACUATING: return "Evacuating";
491 case EVACUATING_AFTER_GLOBAL: return "Evacuating (G)";
492 default:
493 ShouldNotReachHere();
494 return "Unknown";
495 }
496 }
497
498 void ShenandoahOldGeneration::transition_to(State new_state) {
499 if (_state != new_state) {
500 log_debug(gc)("Old generation transition from %s to %s", state_name(_state), state_name(new_state));
501 EventMark event("Old was %s, now is %s", state_name(_state), state_name(new_state));
502 validate_transition(new_state);
503 _state = new_state;
504 }
505 }
506
507 #ifdef ASSERT
508 // This diagram depicts the expected state transitions for marking the old generation
509 // and preparing for old collections. When a young generation cycle executes, the
510 // remembered set scan must visit objects in old regions. Visiting an object which
511 // has become dead on previous old cycles will result in crashes. To avoid visiting
512 // such objects, the remembered set scan will use the old generation mark bitmap when
513 // possible. It is _not_ possible to use the old generation bitmap when old marking
514 // is active (bitmap is not complete). For this reason, the old regions are made
515 // parsable _before_ the old generation bitmap is reset. The diagram does not depict
516 // cancellation of old collections by global or full collections.
517 //
518 // When a global collection supersedes an old collection, the global mark still
519 // "completes" the old mark bitmap. Subsequent remembered set scans may use the
520 // old generation mark bitmap, but any uncollected old regions must still be made parsable
521 // before the next old generation cycle begins. For this reason, a global collection may
522 // create mixed collection candidates and coalesce and fill candidates and will put
523 // the old generation in the respective states (EVACUATING or FILLING). After a Full GC,
524 // the mark bitmaps are all reset, all regions are parsable and the mark context will
525 // not be "complete". After a Full GC, remembered set scans will _not_ use the mark bitmap
526 // and we expect the old generation to be waiting for bootstrap.
527 //
528 // +-----------------+
529 // +------------> | FILLING | <---+
530 // | +--------> | | |
531 // | | +-----------------+ |
532 // | | | |
533 // | | | Filling Complete | <-> A global collection may
534 // | | v | move the old generation
535 // | | +-----------------+ | directly from waiting for
536 // +-- |-- |--------> | WAITING | | bootstrap to filling or
537 // | | | +---- | FOR BOOTSTRAP | ----+ evacuating. It may also
538 // | | | | +-----------------+ move from filling to waiting
539 // | | | | | for bootstrap.
540 // | | | | | Reset Bitmap
541 // | | | | v
542 // | | | | +-----------------+ +----------------------+
543 // | | | | | BOOTSTRAP | <-> | YOUNG GC |
544 // | | | | | | | (RSet Parses Region) |
545 // | | | | +-----------------+ +----------------------+
546 // | | | | |
547 // | | | | | Old Marking
548 // | | | | v
549 // | | | | +-----------------+ +----------------------+
550 // | | | | | MARKING | <-> | YOUNG GC |
551 // | | +--------- | | | (RSet Parses Region) |
552 // | | | +-----------------+ +----------------------+
553 // | | | |
554 // | | | | Has Evacuation Candidates
555 // | | | v
556 // | | | +-----------------+ +--------------------+
557 // | | +---> | EVACUATING | <-> | YOUNG GC |
558 // | +------------- | | | (RSet Uses Bitmap) |
559 // | +-----------------+ +--------------------+
560 // | |
561 // | | Global Cycle Coalesces and Fills Old Regions
562 // | v
563 // | +-----------------+ +--------------------+
564 // +----------------- | EVACUATING | <-> | YOUNG GC |
565 // | AFTER GLOBAL | | (RSet Uses Bitmap) |
566 // +-----------------+ +--------------------+
567 //
568 //
569 void ShenandoahOldGeneration::validate_transition(State new_state) {
570 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap();
571 switch (new_state) {
572 case FILLING:
573 assert(_state != BOOTSTRAPPING, "Cannot begin making old regions parsable after bootstrapping");
574 assert(is_mark_complete(), "Cannot begin filling without first completing marking, state is '%s'", state_name(_state));
575 assert(_old_heuristics->has_coalesce_and_fill_candidates(), "Cannot begin filling without something to fill.");
576 break;
577 case WAITING_FOR_BOOTSTRAP:
578 // GC cancellation can send us back here from any state.
579 validate_waiting_for_bootstrap();
580 break;
581 case BOOTSTRAPPING:
582 assert(_state == WAITING_FOR_BOOTSTRAP, "Cannot reset bitmap without making old regions parsable, state is '%s'", state_name(_state));
583 assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Cannot bootstrap with mixed collection candidates");
584 assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot still be making old regions parsable.");
585 break;
586 case MARKING:
587 assert(_state == BOOTSTRAPPING, "Must have finished bootstrapping before marking, state is '%s'", state_name(_state));
588 assert(heap->young_generation()->old_gen_task_queues() != nullptr, "Young generation needs old mark queues.");
589 assert(heap->is_concurrent_old_mark_in_progress(), "Should be marking old now.");
590 break;
591 case EVACUATING_AFTER_GLOBAL:
592 assert(_state == EVACUATING, "Must have been evacuating, state is '%s'", state_name(_state));
593 break;
594 case EVACUATING:
595 assert(_state == WAITING_FOR_BOOTSTRAP || _state == MARKING, "Cannot have old collection candidates without first marking, state is '%s'", state_name(_state));
596 assert(_old_heuristics->unprocessed_old_collection_candidates() > 0, "Must have collection candidates here.");
597 break;
598 default:
599 fatal("Unknown new state");
600 }
601 }
602
603 bool ShenandoahOldGeneration::validate_waiting_for_bootstrap() {
604 ShenandoahHeap* heap = ShenandoahHeap::heap();
605 assert(!heap->is_concurrent_old_mark_in_progress(), "Cannot become ready for bootstrap during old mark.");
606 assert(heap->young_generation()->old_gen_task_queues() == nullptr, "Cannot become ready for bootstrap when still setup for bootstrapping.");
607 assert(!is_concurrent_mark_in_progress(), "Cannot be marking in IDLE");
608 assert(!heap->young_generation()->is_bootstrap_cycle(), "Cannot have old mark queues if IDLE");
609 assert(!_old_heuristics->has_coalesce_and_fill_candidates(), "Cannot have coalesce and fill candidates in IDLE");
610 assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Cannot have mixed collection candidates in IDLE");
611 return true;
612 }
613 #endif
614
615 ShenandoahHeuristics* ShenandoahOldGeneration::initialize_heuristics(ShenandoahMode* gc_mode) {
616 _old_heuristics = new ShenandoahOldHeuristics(this, ShenandoahGenerationalHeap::heap());
617 _old_heuristics->set_guaranteed_gc_interval(ShenandoahGuaranteedOldGCInterval);
618 _heuristics = _old_heuristics;
619 return _heuristics;
620 }
621
622 void ShenandoahOldGeneration::record_success_concurrent(bool abbreviated) {
623 heuristics()->record_success_concurrent();
624 ShenandoahHeap::heap()->shenandoah_policy()->record_success_old();
625 }
626
627 void ShenandoahOldGeneration::handle_failed_evacuation() {
628 if (_failed_evacuation.try_set()) {
629 log_debug(gc)("Old gen evac failure.");
630 }
631 }
632
633 void ShenandoahOldGeneration::handle_failed_promotion(Thread* thread, size_t size) {
634 // We squelch excessive reports to reduce noise in logs.
635 const size_t MaxReportsPerEpoch = 4;
636 static size_t last_report_epoch = 0;
637 static size_t epoch_report_count = 0;
638 auto heap = ShenandoahGenerationalHeap::heap();
639
640 size_t promotion_reserve;
641 size_t promotion_expended;
642
643 const size_t gc_id = heap->control_thread()->get_gc_id();
644
645 if ((gc_id != last_report_epoch) || (epoch_report_count++ < MaxReportsPerEpoch)) {
646 {
647 // Promotion failures should be very rare. Invest in providing useful diagnostic info.
648 ShenandoahHeapLocker locker(heap->lock());
649 promotion_reserve = get_promoted_reserve();
650 promotion_expended = get_promoted_expended();
651 }
652 PLAB* const plab = ShenandoahThreadLocalData::plab(thread);
653 const size_t words_remaining = (plab == nullptr)? 0: plab->words_remaining();
654 const char* promote_enabled = ShenandoahThreadLocalData::allow_plab_promotions(thread)? "enabled": "disabled";
655
656 log_info(gc, ergo)("Promotion failed, size " SIZE_FORMAT ", has plab? %s, PLAB remaining: " SIZE_FORMAT
657 ", plab promotions %s, promotion reserve: " SIZE_FORMAT ", promotion expended: " SIZE_FORMAT
658 ", old capacity: " SIZE_FORMAT ", old_used: " SIZE_FORMAT ", old unaffiliated regions: " SIZE_FORMAT,
659 size * HeapWordSize, plab == nullptr? "no": "yes",
660 words_remaining * HeapWordSize, promote_enabled, promotion_reserve, promotion_expended,
661 max_capacity(), used(), free_unaffiliated_regions());
662
663 if ((gc_id == last_report_epoch) && (epoch_report_count >= MaxReportsPerEpoch)) {
664 log_debug(gc, ergo)("Squelching additional promotion failure reports for current epoch");
665 } else if (gc_id != last_report_epoch) {
666 last_report_epoch = gc_id;
667 epoch_report_count = 1;
668 }
669 }
670 }
671
672 void ShenandoahOldGeneration::handle_evacuation(HeapWord* obj, size_t words, bool promotion) {
673 // Only register the copy of the object that won the evacuation race.
674 _card_scan->register_object_without_lock(obj);
675
676 // Mark the entire range of the evacuated object as dirty. At next remembered set scan,
677 // we will clear dirty bits that do not hold interesting pointers. It's more efficient to
678 // do this in batch, in a background GC thread than to try to carefully dirty only cards
679 // that hold interesting pointers right now.
680 _card_scan->mark_range_as_dirty(obj, words);
681
682 if (promotion) {
683 // This evacuation was a promotion, track this as allocation against old gen
684 increase_allocated(words * HeapWordSize);
685 }
686 }
687
688 bool ShenandoahOldGeneration::has_unprocessed_collection_candidates() {
689 return _old_heuristics->unprocessed_old_collection_candidates() > 0;
690 }
691
692 size_t ShenandoahOldGeneration::unprocessed_collection_candidates_live_memory() {
693 return _old_heuristics->unprocessed_old_collection_candidates_live_memory();
694 }
695
696 void ShenandoahOldGeneration::abandon_collection_candidates() {
697 _old_heuristics->abandon_collection_candidates();
698 }
699
700 void ShenandoahOldGeneration::prepare_for_mixed_collections_after_global_gc() {
701 assert(is_mark_complete(), "Expected old generation mark to be complete after global cycle.");
702 _old_heuristics->prepare_for_old_collections();
703 log_info(gc, ergo)("After choosing global collection set, mixed candidates: " UINT32_FORMAT ", coalescing candidates: " SIZE_FORMAT,
704 _old_heuristics->unprocessed_old_collection_candidates(),
705 _old_heuristics->coalesce_and_fill_candidates_count());
706 }
707
708 void ShenandoahOldGeneration::parallel_heap_region_iterate_free(ShenandoahHeapRegionClosure* cl) {
709 // Iterate over old and free regions (exclude young).
710 ShenandoahExcludeRegionClosure<YOUNG_GENERATION> exclude_cl(cl);
711 ShenandoahGeneration::parallel_heap_region_iterate_free(&exclude_cl);
712 }
713
714 void ShenandoahOldGeneration::set_parsable(bool parsable) {
715 _is_parsable = parsable;
716 if (_is_parsable) {
717 // The current state would have been chosen during final mark of the global
718 // collection, _before_ any decisions about class unloading have been made.
719 //
720 // After unloading classes, we have made the old generation regions parsable.
721 // We can skip filling or transition to a state that knows everything has
722 // already been filled.
723 switch (state()) {
724 case ShenandoahOldGeneration::EVACUATING:
725 transition_to(ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL);
726 break;
727 case ShenandoahOldGeneration::FILLING:
728 assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Expected no mixed collection candidates");
729 assert(_old_heuristics->coalesce_and_fill_candidates_count() > 0, "Expected coalesce and fill candidates");
730 // When the heuristic put the old generation in this state, it didn't know
731 // that we would unload classes and make everything parsable. But, we know
732 // that now so we can override this state.
733 abandon_collection_candidates();
734 transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP);
735 break;
736 default:
737 // We can get here during a full GC. The full GC will cancel anything
738 // happening in the old generation and return it to the waiting for bootstrap
739 // state. The full GC will then record that the old regions are parsable
740 // after rebuilding the remembered set.
741 assert(is_idle(), "Unexpected state %s at end of global GC", state_name());
742 break;
743 }
744 }
745 }
746
747 void ShenandoahOldGeneration::complete_mixed_evacuations() {
748 assert(is_doing_mixed_evacuations(), "Mixed evacuations should be in progress");
749 if (!_old_heuristics->has_coalesce_and_fill_candidates()) {
750 // No candidate regions to coalesce and fill
751 transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP);
752 return;
753 }
754
755 if (state() == ShenandoahOldGeneration::EVACUATING) {
756 transition_to(ShenandoahOldGeneration::FILLING);
757 return;
758 }
759
760 // Here, we have no more candidates for mixed collections. The candidates for coalescing
761 // and filling have already been processed during the global cycle, so there is nothing
762 // more to do.
763 assert(state() == ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL, "Should be evacuating after a global cycle");
764 abandon_collection_candidates();
765 transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP);
766 }
767
768 void ShenandoahOldGeneration::abandon_mixed_evacuations() {
769 switch(state()) {
770 case ShenandoahOldGeneration::EVACUATING:
771 transition_to(ShenandoahOldGeneration::FILLING);
772 break;
773 case ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL:
774 abandon_collection_candidates();
775 transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP);
776 break;
777 default:
778 log_warning(gc)("Abandon mixed evacuations in unexpected state: %s", state_name(state()));
779 ShouldNotReachHere();
780 break;
781 }
782 }
783
784 void ShenandoahOldGeneration::clear_cards_for(ShenandoahHeapRegion* region) {
785 _card_scan->mark_range_as_empty(region->bottom(), pointer_delta(region->end(), region->bottom()));
786 }
787
788 void ShenandoahOldGeneration::mark_card_as_dirty(void* location) {
789 _card_scan->mark_card_as_dirty((HeapWord*)location);
790 }