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