1 /*
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3 * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
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12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
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20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26 #include "gc/shenandoah/shenandoahAgeCensus.hpp"
27 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
29 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
30 #include "gc/shenandoah/shenandoahFreeSet.hpp"
31 #include "gc/shenandoah/shenandoahGeneration.hpp"
32 #include "gc/shenandoah/shenandoahGenerationalControlThread.hpp"
33 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp"
34 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
35 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
36 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
37 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
38 #include "gc/shenandoah/shenandoahInitLogger.hpp"
39 #include "gc/shenandoah/shenandoahMemoryPool.hpp"
40 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
41 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
42 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
43 #include "gc/shenandoah/shenandoahRegulatorThread.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 "logging/log.hpp"
49 #include "utilities/events.hpp"
50
51
52 class ShenandoahGenerationalInitLogger : public ShenandoahInitLogger {
53 public:
54 static void print() {
55 ShenandoahGenerationalInitLogger logger;
56 logger.print_all();
57 }
58 protected:
59 void print_gc_specific() override {
60 ShenandoahInitLogger::print_gc_specific();
61
62 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap();
63 log_info(gc, init)("Young Heuristics: %s", heap->young_generation()->heuristics()->name());
64 log_info(gc, init)("Old Heuristics: %s", heap->old_generation()->heuristics()->name());
65 }
66 };
67
68 size_t ShenandoahGenerationalHeap::calculate_min_plab() {
69 return PLAB::min_size();
70 }
71
72 size_t ShenandoahGenerationalHeap::calculate_max_plab() {
73 return ShenandoahHeapRegion::max_tlab_size_words();
74 }
75
76 // Returns size in bytes
77 size_t ShenandoahGenerationalHeap::unsafe_max_tlab_alloc() const {
78 return MIN2(ShenandoahHeapRegion::max_tlab_size_bytes(), young_generation()->available());
79 }
80
81 ShenandoahGenerationalHeap::ShenandoahGenerationalHeap(ShenandoahCollectorPolicy* policy) :
82 ShenandoahHeap(policy),
83 _age_census(nullptr),
84 _min_plab_size(calculate_min_plab()),
85 _max_plab_size(calculate_max_plab()),
86 _regulator_thread(nullptr),
87 _young_gen_memory_pool(nullptr),
88 _old_gen_memory_pool(nullptr) {
89 }
90
91 void ShenandoahGenerationalHeap::initialize_generations() {
92 ShenandoahHeap::initialize_generations();
93 _young_generation->post_initialize(this);
94 _old_generation->post_initialize(this);
95 }
96
97 void ShenandoahGenerationalHeap::post_initialize() {
98 ShenandoahHeap::post_initialize();
99 _age_census = new ShenandoahAgeCensus();
100 }
101
102 void ShenandoahGenerationalHeap::post_initialize_heuristics() {
103 ShenandoahHeap::post_initialize_heuristics();
104 _young_generation->post_initialize_heuristics();
105 _old_generation->post_initialize_heuristics();
106 }
107
108 void ShenandoahGenerationalHeap::print_init_logger() const {
109 ShenandoahGenerationalInitLogger logger;
110 logger.print_all();
111 }
112
113 void ShenandoahGenerationalHeap::initialize_heuristics() {
114 // Initialize global generation and heuristics even in generational mode.
115 ShenandoahHeap::initialize_heuristics();
116
117 _young_generation = new ShenandoahYoungGeneration(max_workers());
118 _old_generation = new ShenandoahOldGeneration(max_workers());
119 _young_generation->initialize_heuristics(mode());
120 _old_generation->initialize_heuristics(mode());
121 }
122
123 void ShenandoahGenerationalHeap::initialize_serviceability() {
124 assert(mode()->is_generational(), "Only for the generational mode");
125 _young_gen_memory_pool = new ShenandoahYoungGenMemoryPool(this);
126 _old_gen_memory_pool = new ShenandoahOldGenMemoryPool(this);
127 cycle_memory_manager()->add_pool(_young_gen_memory_pool);
128 cycle_memory_manager()->add_pool(_old_gen_memory_pool);
129 stw_memory_manager()->add_pool(_young_gen_memory_pool);
130 stw_memory_manager()->add_pool(_old_gen_memory_pool);
131 }
132
133 GrowableArray<MemoryPool*> ShenandoahGenerationalHeap::memory_pools() {
134 assert(mode()->is_generational(), "Only for the generational mode");
135 GrowableArray<MemoryPool*> memory_pools(2);
136 memory_pools.append(_young_gen_memory_pool);
137 memory_pools.append(_old_gen_memory_pool);
138 return memory_pools;
139 }
140
141 void ShenandoahGenerationalHeap::initialize_controller() {
142 auto control_thread = new ShenandoahGenerationalControlThread();
143 _control_thread = control_thread;
144 _regulator_thread = new ShenandoahRegulatorThread(control_thread);
145 }
146
147 void ShenandoahGenerationalHeap::gc_threads_do(ThreadClosure* tcl) const {
148 if (!shenandoah_policy()->is_at_shutdown()) {
149 ShenandoahHeap::gc_threads_do(tcl);
150 tcl->do_thread(regulator_thread());
151 }
152 }
153
154 void ShenandoahGenerationalHeap::stop() {
155 ShenandoahHeap::stop();
156 regulator_thread()->stop();
157 }
158
159 void ShenandoahGenerationalHeap::start_idle_span() {
160 young_generation()->heuristics()->start_idle_span();
161 }
162
163 bool ShenandoahGenerationalHeap::requires_barriers(stackChunkOop obj) const {
164 if (is_idle()) {
165 return false;
166 }
167
168 if (is_concurrent_young_mark_in_progress() && is_in_young(obj) && !marking_context()->allocated_after_mark_start(obj)) {
169 // We are marking young, this object is in young, and it is below the TAMS
170 return true;
171 }
172
173 if (is_in_old(obj)) {
174 // Card marking barriers are required for objects in the old generation
175 return true;
176 }
177
178 if (has_forwarded_objects()) {
179 // Object may have pointers that need to be updated
180 return true;
181 }
182
183 return false;
184 }
185
186 void ShenandoahGenerationalHeap::evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent) {
187 ShenandoahRegionIterator regions;
188 ShenandoahGenerationalEvacuationTask task(this, generation, ®ions, concurrent, false /* only promote regions */);
189 workers()->run_task(&task);
190 }
191
192 void ShenandoahGenerationalHeap::promote_regions_in_place(ShenandoahGeneration* generation, bool concurrent) {
193 ShenandoahRegionIterator regions;
194 ShenandoahGenerationalEvacuationTask task(this, generation, ®ions, concurrent, true /* only promote regions */);
195 workers()->run_task(&task);
196 }
197
198 oop ShenandoahGenerationalHeap::evacuate_object(oop p, Thread* thread) {
199 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
200
201 ShenandoahHeapRegion* from_region = heap_region_containing(p);
202 assert(!from_region->is_humongous(), "never evacuate humongous objects");
203
204 // Try to keep the object in the same generation
205 const ShenandoahAffiliation target_gen = from_region->affiliation();
206
207 if (target_gen == YOUNG_GENERATION) {
208 markWord mark = p->mark();
209 if (mark.is_marked()) {
210 // Already forwarded.
211 return ShenandoahForwarding::get_forwardee(p);
212 }
213
214 if (mark.has_displaced_mark_helper()) {
215 // We don't want to deal with MT here just to ensure we read the right mark word.
216 // Skip the potential promotion attempt for this one.
217 } else if (age_census()->is_tenurable(from_region->age() + mark.age())) {
218 // If the object is tenurable, try to promote it
219 oop result = try_evacuate_object<YOUNG_GENERATION, OLD_GENERATION>(p, thread, from_region->age());
220
221 // If we failed to promote this aged object, we'll fall through to code below and evacuate to young-gen.
222 if (result != nullptr) {
223 return result;
224 }
225 }
226 return try_evacuate_object<YOUNG_GENERATION, YOUNG_GENERATION>(p, thread, from_region->age());
227 }
228
229 assert(target_gen == OLD_GENERATION, "Expected evacuation to old");
230 return try_evacuate_object<OLD_GENERATION, OLD_GENERATION>(p, thread, from_region->age());
231 }
232
233 // try_evacuate_object registers the object and dirties the associated remembered set information when evacuating
234 // to OLD_GENERATION.
235 template<ShenandoahAffiliation FROM_GENERATION, ShenandoahAffiliation TO_GENERATION>
236 oop ShenandoahGenerationalHeap::try_evacuate_object(oop p, Thread* thread, uint from_region_age) {
237 bool alloc_from_lab = true;
238 bool has_plab = false;
239 HeapWord* copy = nullptr;
240 size_t size = ShenandoahForwarding::size(p);
241 constexpr bool is_promotion = (TO_GENERATION == OLD_GENERATION) && (FROM_GENERATION == YOUNG_GENERATION);
242
243 #ifdef ASSERT
244 if (ShenandoahOOMDuringEvacALot &&
245 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
246 copy = nullptr;
247 } else {
248 #endif
249 if (UseTLAB) {
250 switch (TO_GENERATION) {
251 case YOUNG_GENERATION: {
252 copy = allocate_from_gclab(thread, size);
253 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) {
254 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting
255 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations.
256 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size());
257 copy = allocate_from_gclab(thread, size);
258 // If we still get nullptr, we'll try a shared allocation below.
259 }
260 break;
261 }
262 case OLD_GENERATION: {
263 ShenandoahPLAB* shenandoah_plab = ShenandoahThreadLocalData::shenandoah_plab(thread);
264 if (shenandoah_plab != nullptr) {
265 has_plab = true;
266 copy = shenandoah_plab->allocate(size, is_promotion);
267 if (copy == nullptr && size < shenandoah_plab->desired_size() && shenandoah_plab->retries_enabled()) {
268 // PLAB allocation failed because we are bumping up against the limit on old evacuation reserve or because
269 // the requested object does not fit within the current plab but the plab still has an "abundance" of memory,
270 // where abundance is defined as >= ShenGenHeap::plab_min_size(). In the former case, we try shrinking the
271 // desired PLAB size to the minimum and retry PLAB allocation to avoid cascading of shared memory allocations.
272 // Shrinking the desired PLAB size may allow us to eke out a small PLAB while staying beneath evacuation reserve.
273 if (shenandoah_plab->plab()->words_remaining() < plab_min_size()) {
274 shenandoah_plab->set_desired_size(plab_min_size());
275 copy = shenandoah_plab->allocate(size, is_promotion);
276 if (copy == nullptr) {
277 // If we still get nullptr, we'll try a shared allocation below.
278 // However, don't continue to retry until we have success (probably in next GC pass)
279 shenandoah_plab->disable_retries();
280 }
281 }
282 }
283 }
284 break;
285 }
286 default: {
287 ShouldNotReachHere();
288 break;
289 }
290 }
291 }
292
293 if (copy == nullptr) {
294 // If we failed to allocate in LAB, we'll try a shared allocation.
295 if (!is_promotion || !has_plab || (size > PLAB::min_size())) {
296 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, TO_GENERATION, is_promotion);
297 copy = allocate_memory(req);
298 alloc_from_lab = false;
299 }
300 // else, we leave copy equal to nullptr, signaling a promotion failure below if appropriate.
301 // We choose not to promote objects smaller than size_threshold by way of shared allocations as this is too
302 // costly. Instead, we'll simply "evacuate" to young-gen memory (using a GCLAB) and will promote in a future
303 // evacuation pass. This condition is denoted by: is_promotion && has_plab && (size <= size_threshhold).
304 }
305 #ifdef ASSERT
306 }
307 #endif
308
309 if (copy == nullptr) {
310 if (TO_GENERATION == OLD_GENERATION) {
311 if (FROM_GENERATION == YOUNG_GENERATION) {
312 // Signal that promotion failed. Will evacuate this old object somewhere in young gen.
313 old_generation()->handle_failed_promotion(thread, size);
314 return nullptr;
315 } else {
316 // Remember that evacuation to old gen failed. We'll want to trigger a full gc to recover from this
317 // after the evacuation threads have finished.
318 old_generation()->handle_failed_evacuation();
319 }
320 }
321
322 control_thread()->handle_alloc_failure_evac(size);
323
324 // Install the self-forwarded bit so other evacuators/LRBs see the
325 // object as "already handled, do not try to evacuate". The CAS may
326 // fail if another thread concurrently installed a real forwardee or
327 // self-forwarded first.
328 markWord old_mark = p->mark();
329 if (old_mark.is_forwarded()) {
330 return ShenandoahForwarding::get_forwardee(p);
331 }
332 oop winner = ShenandoahForwarding::try_forward_to_self(p, old_mark);
333 if (winner == nullptr) {
334 // We own the self-forwarding. Flag the from-region so the degen/full
335 // GC entry drain knows to scan it for self_fwd bits to clear.
336 heap_region_containing(p)->set_has_self_forwards();
337 return p;
338 }
339 return winner;
340 }
341
342 if (ShenandoahEvacTracking) {
343 evac_tracker()->begin_evacuation(thread, size * HeapWordSize, FROM_GENERATION, TO_GENERATION);
344 }
345
346 // Copy the object:
347 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
348 oop copy_val = cast_to_oop(copy);
349
350 // Update the age of the evacuated object
351 if (TO_GENERATION == YOUNG_GENERATION) {
352 increase_object_age(copy_val, from_region_age + 1);
353 }
354
355 // Relativize stack chunks before publishing the copy. After the forwarding CAS,
356 // mutators can see the copy and thaw it via the fast path if flags == 0. We must
357 // relativize derived pointers and set gc_mode before that happens. Skip if the
358 // copy's mark word is already a forwarding pointer (another thread won the race
359 // and overwrote the original's header before we copied it).
360 if (!ShenandoahForwarding::is_forwarded(copy_val)) {
361 ContinuationGCSupport::relativize_stack_chunk(copy_val);
362 }
363
364 // Try to install the new forwarding pointer.
365 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
366 if (result == copy_val) {
367 // Successfully evacuated. Our copy is now the public one!
368 if (ShenandoahEvacTracking) {
369 // Record that the evacuation succeeded
370 evac_tracker()->end_evacuation(thread, size * HeapWordSize, FROM_GENERATION, TO_GENERATION);
371 }
372 } else {
373 // Failed to evacuate. We need to deal with the object that is left behind. Since this
374 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
375 // But if it happens to contain references to evacuated regions, those references would
376 // not get updated for this stale copy during this cycle, and we will crash while scanning
377 // it the next cycle.
378 if (alloc_from_lab) {
379 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
380 // object will overwrite this stale copy, or the filler object on LAB retirement will
381 // do this.
382 switch (TO_GENERATION) {
383 case YOUNG_GENERATION: {
384 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
385 break;
386 }
387 case OLD_GENERATION: {
388 ShenandoahThreadLocalData::shenandoah_plab(thread)->plab()->undo_allocation(copy, size);
389 if (is_promotion) {
390 ShenandoahThreadLocalData::shenandoah_plab(thread)->subtract_from_promoted(size * HeapWordSize);
391 }
392 break;
393 }
394 default: {
395 ShouldNotReachHere();
396 break;
397 }
398 }
399 } else {
400 // For non-LAB allocations, we have no way to retract the allocation, and
401 // have to explicitly overwrite the copy with the filler object. With that overwrite,
402 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
403 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
404 fill_with_object(copy, size);
405 }
406 }
407 shenandoah_assert_correct(nullptr, result);
408 return result;
409 }
410
411 template oop ShenandoahGenerationalHeap::try_evacuate_object<YOUNG_GENERATION, YOUNG_GENERATION>(oop p, Thread* thread, uint from_region_age);
412 template oop ShenandoahGenerationalHeap::try_evacuate_object<YOUNG_GENERATION, OLD_GENERATION>(oop p, Thread* thread, uint from_region_age);
413 template oop ShenandoahGenerationalHeap::try_evacuate_object<OLD_GENERATION, OLD_GENERATION>(oop p, Thread* thread, uint from_region_age);
414
415 // Call this function at the end of a GC cycle in order to establish proper sizes of young and old reserves,
416 // setting the old-generation balance so that GC can perform the anticipated evacuations.
417 //
418 // Make sure old-generation is large enough, but no larger than is necessary, to hold mixed evacuations
419 // and promotions, if we anticipate either. Any deficit is provided by the young generation, subject to
420 // mutator_xfer_limit, and any surplus is transferred to the young generation. mutator_xfer_limit is
421 // the maximum we're able to transfer from young to old. The mutator_xfer_limit constrains the transfer
422 // of memory from young to old. It does not limit young reserves.
423 void ShenandoahGenerationalHeap::compute_old_generation_balance(size_t mutator_xfer_limit,
424 size_t old_trashed_regions, size_t young_trashed_regions) {
425 shenandoah_assert_heaplocked();
426 // We can limit the old reserve to the size of anticipated promotions:
427 // max_old_reserve is an upper bound on memory evacuated from old and promoted to old,
428 // clamped by the old generation space available.
429 //
430 // Here's the algebra.
431 // Let SOEP = ShenandoahOldEvacPercent,
432 // OE = old evac,
433 // YE = young evac, and
434 // TE = total evac = OE + YE
435 // By definition:
436 // SOEP/100 = OE/TE
437 // = OE/(OE+YE)
438 // => SOEP/(100-SOEP) = OE/((OE+YE)-OE) // componendo-dividendo: If a/b = c/d, then a/(b-a) = c/(d-c)
439 // = OE/YE
440 // => OE = YE*SOEP/(100-SOEP)
441
442 // We have to be careful in the event that SOEP is set to 100 by the user.
443 assert(ShenandoahOldEvacPercent <= 100, "Error");
444 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
445
446 ShenandoahOldGeneration* old_gen = old_generation();
447 size_t old_capacity = old_gen->max_capacity();
448 size_t old_usage = old_gen->used(); // includes humongous waste
449 size_t old_currently_available =
450 ((old_capacity >= old_usage)? old_capacity - old_usage: 0) + old_trashed_regions * region_size_bytes;
451
452 ShenandoahYoungGeneration* young_gen = young_generation();
453 size_t young_capacity = young_gen->max_capacity();
454 size_t young_usage = young_gen->used(); // includes humongous waste
455 size_t young_available = ((young_capacity >= young_usage)? young_capacity - young_usage: 0);
456 size_t freeset_available = free_set()->available_locked();
457 if (young_available > freeset_available) {
458 young_available = freeset_available;
459 }
460 young_available += young_trashed_regions * region_size_bytes;
461
462 // The free set will reserve this amount of memory to hold young evacuations (initialized to the ideal reserve)
463 size_t young_reserve = (young_generation()->max_capacity() * ShenandoahEvacReserve) / 100;
464
465 // If ShenandoahOldEvacPercent equals 100, max_old_reserve is limited only by mutator_xfer_limit and young_reserve
466 const size_t bound_on_old_reserve =
467 ((old_currently_available + mutator_xfer_limit + young_reserve) * ShenandoahOldEvacPercent) / 100;
468 size_t proposed_max_old = ((ShenandoahOldEvacPercent == 100)?
469 bound_on_old_reserve:
470 MIN2((young_reserve * ShenandoahOldEvacPercent) / (100 - ShenandoahOldEvacPercent),
471 bound_on_old_reserve));
472 assert(mutator_xfer_limit <= young_available,
473 "Cannot transfer (%zu) memory that is not available (%zu)", mutator_xfer_limit, young_available);
474
475 if (young_reserve > young_available) {
476 young_reserve = young_available;
477 }
478 // We allow young_reserve to exceed mutator_xfer_limit. Essentially, this means the GC is already behind the pace
479 // of mutator allocations, and we'll need to trigger the next GC as soon as possible.
480 if (mutator_xfer_limit > young_reserve) {
481 mutator_xfer_limit -= young_reserve;
482 } else {
483 mutator_xfer_limit = 0;
484 }
485
486 // Decide how much old space we should reserve for a mixed collection
487 size_t proposed_reserve_for_mixed = 0;
488 const size_t old_fragmented_available =
489 old_currently_available - (old_generation()->free_unaffiliated_regions() + old_trashed_regions) * region_size_bytes;
490
491 if (old_fragmented_available > proposed_max_old) {
492 // In this case, the old_fragmented_available is greater than the desired amount of evacuation to old.
493 // We'll use all of this memory to hold results of old evacuation, and we'll give back to the young generation
494 // any old regions that are not fragmented.
495 //
496 // This scenario may happen after we have promoted many regions in place, and each of these regions had non-zero
497 // unused memory, so there is now an abundance of old-fragmented available memory, even more than the desired
498 // percentage for old reserve. We cannot transfer these fragmented regions back to young. Instead we make the
499 // best of the situation by using this fragmented memory for both promotions and evacuations.
500
501 proposed_max_old = old_fragmented_available;
502 }
503 // Otherwise: old_fragmented_available <= proposed_max_old. Do not shrink proposed_max_old from the original computation.
504
505 // Though we initially set proposed_reserve_for_promo to equal the entirety of old fragmented available, we have the
506 // opportunity below to shift some of this memory into the proposed_reserve_for_mixed.
507 size_t proposed_reserve_for_promo = old_fragmented_available;
508 const size_t max_old_reserve = proposed_max_old;
509
510 const size_t mixed_candidate_live_memory = old_generation()->unprocessed_collection_candidates_live_memory();
511 const bool doing_mixed = (mixed_candidate_live_memory > 0);
512 if (doing_mixed) {
513 // In the ideal, all of the memory reserved for mixed evacuation would be unfragmented, but we don't enforce
514 // this. Note that the initial value of max_evac_need is conservative because we may not evacuate all of the
515 // remaining mixed evacuation candidates in a single cycle.
516 const size_t max_evac_need = (size_t) (mixed_candidate_live_memory * ShenandoahOldEvacWaste);
517 assert(old_currently_available >= old_generation()->free_unaffiliated_regions() * region_size_bytes,
518 "Unaffiliated available must be less than total available");
519
520 // We prefer to evacuate all of mixed into unfragmented memory, and will expand old in order to do so, unless
521 // we already have too much fragmented available memory in old.
522 proposed_reserve_for_mixed = max_evac_need;
523 if (proposed_reserve_for_mixed + proposed_reserve_for_promo > max_old_reserve) {
524 // We're trying to reserve more memory than is available. So we need to shrink our reserves.
525 size_t excess_reserves = (proposed_reserve_for_mixed + proposed_reserve_for_promo) - max_old_reserve;
526 // We need to shrink reserves by excess_reserves. We prefer to shrink by reducing promotion, giving priority to mixed
527 // evacuation. If the promotion reserve is larger than the amount we need to shrink by, do all the shrinkage there.
528 if (proposed_reserve_for_promo > excess_reserves) {
529 proposed_reserve_for_promo -= excess_reserves;
530 } else {
531 // Otherwise, we'll shrink promotion reserve to zero and we'll shrink the mixed-evac reserve by the remaining excess.
532 excess_reserves -= proposed_reserve_for_promo;
533 proposed_reserve_for_promo = 0;
534 proposed_reserve_for_mixed -= excess_reserves;
535 }
536 }
537 }
538 assert(proposed_reserve_for_mixed + proposed_reserve_for_promo <= max_old_reserve,
539 "Reserve for mixed (%zu) plus reserve for promotions (%zu) must be less than maximum old reserve (%zu)",
540 proposed_reserve_for_mixed, proposed_reserve_for_promo, max_old_reserve);
541
542 // Decide how much additional space we should reserve for promotions from young. We give priority to mixed evacations
543 // over promotions.
544 const size_t promo_load = old_generation()->get_promotion_potential();
545 const bool doing_promotions = promo_load > 0;
546
547 // promo_load represents the combined total of live memory within regions that have reached tenure age. The true
548 // promotion potential is larger than this, because individual objects within regions that have not yet reached tenure
549 // age may be promotable. On the other hand, some of the objects that we intend to promote in the next GC cycle may
550 // die before they are next marked. In the future, the promo_load will include the total size of tenurable objects
551 // residing in regions that have not yet reached tenure age.
552
553 if (doing_promotions) {
554 // We are always doing promotions, even when old_generation->get_promotion_potential() returns 0. As currently implemented,
555 // get_promotion_potential() only knows the total live memory contained within young-generation regions whose age is
556 // tenurable. It does not know whether that memory will still be live at the end of the next mark cycle, and it doesn't
557 // know how much memory is contained within objects whose individual ages are tenurable, which reside in regions with
558 // non-tenurable age. We use this, as adjusted by ShenandoahPromoEvacWaste, as an approximation of the total amount of
559 // memory to be promoted. In the near future, we expect to implement a change that will allow get_promotion_potential()
560 // to account also for the total memory contained within individual objects that are tenure-ready even when they do
561 // not reside in aged regions. This will represent a conservative over approximation of promotable memory because
562 // some of these objects may die before the next GC cycle executes.
563
564 // Be careful not to ask for too much promotion reserves. We have observed jtreg test failures under which a greedy
565 // promotion reserve causes a humongous allocation which is awaiting a full GC to fail (specifically
566 // gc/TestAllocHumongousFragment.java). This happens if too much of the memory reclaimed by the full GC
567 // is immediately reserved so that it cannot be allocated by the waiting mutator. It's not clear that this
568 // particular test is representative of the needs of typical GenShen users. It is really a test of high frequency
569 // Full GCs under heap fragmentation stress.
570
571 size_t promo_need = (size_t) (promo_load * ShenandoahPromoEvacWaste);
572 if (promo_need > proposed_reserve_for_promo) {
573 const size_t available_for_additional_promotions =
574 max_old_reserve - (proposed_reserve_for_mixed + proposed_reserve_for_promo);
575 if (proposed_reserve_for_promo + available_for_additional_promotions >= promo_need) {
576 proposed_reserve_for_promo = promo_need;
577 } else {
578 proposed_reserve_for_promo += available_for_additional_promotions;
579 }
580 }
581 }
582 // else, leave proposed_reserve_for_promo as is. By default, it is initialized to represent old_fragmented_available.
583
584 // This is the total old we want to reserve (initialized to the ideal reserve)
585 size_t proposed_old_reserve = proposed_reserve_for_mixed + proposed_reserve_for_promo;
586
587 // We now check if the old generation is running a surplus or a deficit.
588 size_t old_region_deficit = 0;
589 size_t old_region_surplus = 0;
590
591 size_t mutator_region_xfer_limit = mutator_xfer_limit / region_size_bytes;
592 // align the mutator_xfer_limit on region size
593 mutator_xfer_limit = mutator_region_xfer_limit * region_size_bytes;
594
595 if (old_currently_available >= proposed_old_reserve) {
596 // We are running a surplus, so the old region surplus can go to young
597 const size_t old_surplus = old_currently_available - proposed_old_reserve;
598 old_region_surplus = old_surplus / region_size_bytes;
599 const size_t unaffiliated_old_regions = old_generation()->free_unaffiliated_regions() + old_trashed_regions;
600 old_region_surplus = MIN2(old_region_surplus, unaffiliated_old_regions);
601 old_generation()->set_region_balance(checked_cast<ssize_t>(old_region_surplus));
602 old_currently_available -= old_region_surplus * region_size_bytes;
603 young_available += old_region_surplus * region_size_bytes;
604 } else if (old_currently_available + mutator_xfer_limit >= proposed_old_reserve) {
605 // We know that old_currently_available < proposed_old_reserve because above test failed. Expand old_currently_available.
606 // Mutator's xfer limit is sufficient to satisfy our need: transfer all memory from there.
607 size_t old_deficit = proposed_old_reserve - old_currently_available;
608 old_region_deficit = (old_deficit + region_size_bytes - 1) / region_size_bytes;
609 old_generation()->set_region_balance(0 - checked_cast<ssize_t>(old_region_deficit));
610 old_currently_available += old_region_deficit * region_size_bytes;
611 young_available -= old_region_deficit * region_size_bytes;
612 } else {
613 // We know that (old_currently_available < proposed_old_reserve) and
614 // (old_currently_available + mutator_xfer_limit < proposed_old_reserve) because above tests failed.
615 // We need to shrink proposed_old_reserves.
616
617 // We could potentially shrink young_reserves in order to further expand proposed_old_reserves. Let's not bother. The
618 // important thing is that we keep a total amount of memory in reserve in preparation for the next GC cycle. At
619 // the time we choose the next collection set, we'll have an opportunity to shift some of these young reserves
620 // into old reserves if that makes sense.
621
622 // Start by taking all of mutator_xfer_limit into old_currently_available.
623 size_t old_region_deficit = mutator_region_xfer_limit;
624 old_generation()->set_region_balance(0 - checked_cast<ssize_t>(old_region_deficit));
625 old_currently_available += old_region_deficit * region_size_bytes;
626 young_available -= old_region_deficit * region_size_bytes;
627
628 assert(old_currently_available < proposed_old_reserve,
629 "Old currently available (%zu) must be less than old reserve (%zu)", old_currently_available, proposed_old_reserve);
630
631 // There's not enough memory to satisfy our desire. Scale back our old-gen intentions. We prefer to satisfy
632 // the budget_overrun entirely from the promotion reserve, if that is large enough. Otherwise, we'll satisfy
633 // the overrun from a combination of promotion and mixed-evacuation reserves.
634 size_t budget_overrun = proposed_old_reserve - old_currently_available;
635 if (proposed_reserve_for_promo > budget_overrun) {
636 proposed_reserve_for_promo -= budget_overrun;
637 // Dead code:
638 // proposed_old_reserve -= budget_overrun;
639 } else {
640 budget_overrun -= proposed_reserve_for_promo;
641 proposed_reserve_for_promo = 0;
642 proposed_reserve_for_mixed = (proposed_reserve_for_mixed > budget_overrun)? proposed_reserve_for_mixed - budget_overrun: 0;
643 // Dead code:
644 // Note: proposed_reserve_for_promo is 0 and proposed_reserve_for_mixed may equal 0.
645 // proposed_old_reserve = proposed_reserve_for_mixed;
646 }
647 }
648
649 assert(old_region_deficit == 0 || old_region_surplus == 0,
650 "Only surplus (%zu) or deficit (%zu), never both", old_region_surplus, old_region_deficit);
651 assert(young_reserve + proposed_reserve_for_mixed + proposed_reserve_for_promo <= old_currently_available + young_available,
652 "Cannot reserve more memory than is available: %zu + %zu + %zu <= %zu + %zu",
653 young_reserve, proposed_reserve_for_mixed, proposed_reserve_for_promo, old_currently_available, young_available);
654
655 // deficit/surplus adjustments to generation sizes will precede rebuild
656 young_generation()->set_evacuation_reserve(young_reserve);
657 old_generation()->set_evacuation_reserve(proposed_reserve_for_mixed);
658 old_generation()->set_promoted_reserve(proposed_reserve_for_promo);
659 }
660
661 void ShenandoahGenerationalHeap::coalesce_and_fill_old_regions(bool concurrent) {
662 class ShenandoahGlobalCoalesceAndFill : public WorkerTask {
663 private:
664 ShenandoahPhaseTimings::Phase _phase;
665 ShenandoahRegionIterator _regions;
666 public:
667 explicit ShenandoahGlobalCoalesceAndFill(ShenandoahPhaseTimings::Phase phase) :
668 WorkerTask("Shenandoah Global Coalesce"),
669 _phase(phase) {}
670
671 void work(uint worker_id) override {
672 ShenandoahWorkerTimingsTracker timer(_phase,
673 ShenandoahPhaseTimings::Work,
674 worker_id, true);
675 ShenandoahHeapRegion* region;
676 while ((region = _regions.next()) != nullptr) {
677 // old region is not in the collection set and was not immediately trashed
678 if (region->is_old() && region->is_active() && !region->is_humongous()) {
679 // Reset the coalesce and fill boundary because this is a global collect
680 // and cannot be preempted by young collects. We want to be sure the entire
681 // region is coalesced here and does not resume from a previously interrupted
682 // or completed coalescing.
683 region->begin_preemptible_coalesce_and_fill();
684 region->oop_coalesce_and_fill(false);
685 }
686 }
687 }
688 };
689
690 ShenandoahPhaseTimings::Phase phase = concurrent ?
691 ShenandoahPhaseTimings::conc_coalesce_and_fill :
692 ShenandoahPhaseTimings::degen_gc_coalesce_and_fill;
693
694 // This is not cancellable
695 ShenandoahGlobalCoalesceAndFill coalesce(phase);
696 workers()->run_task(&coalesce);
697 old_generation()->set_parsable(true);
698 }
699
700 template<bool CONCURRENT>
701 class ShenandoahGenerationalUpdateHeapRefsTask : public WorkerTask {
702 private:
703 // For update refs, _generation will be young or global. Mixed collections use the young generation.
704 ShenandoahGeneration* _generation;
705 ShenandoahGenerationalHeap* _heap;
706 ShenandoahRegionIterator* _regions;
707 ShenandoahRegionChunkIterator* _work_chunks;
708
709 public:
710 ShenandoahGenerationalUpdateHeapRefsTask(ShenandoahGeneration* generation,
711 ShenandoahRegionIterator* regions,
712 ShenandoahRegionChunkIterator* work_chunks) :
713 WorkerTask("Shenandoah Update References"),
714 _generation(generation),
715 _heap(ShenandoahGenerationalHeap::heap()),
716 _regions(regions),
717 _work_chunks(work_chunks)
718 {
719 const bool old_bitmap_stable = _heap->old_generation()->is_mark_complete();
720 log_debug(gc, remset)("Update refs, scan remembered set using bitmap: %s", BOOL_TO_STR(old_bitmap_stable));
721 }
722
723 void work(uint worker_id) override {
724 if (CONCURRENT) {
725 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
726 ShenandoahConcurrentWorkerSession worker_session(worker_id);
727 SuspendibleThreadSetJoiner stsj;
728 do_work<ShenandoahConcUpdateRefsClosure>(worker_id);
729 } else {
730 ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::degen_gc_update_refs, ShenandoahPhaseTimings::Work, worker_id, true);
731 ShenandoahParallelWorkerSession worker_session(worker_id);
732 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id);
733 }
734 }
735
736 private:
737 template<class T>
738 void do_work(uint worker_id) {
739 T cl;
740
741 if (CONCURRENT && (worker_id == 0)) {
742 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the
743 // results of evacuation. These reserves are no longer necessary because evacuation has completed.
744 size_t cset_regions = _heap->collection_set()->count();
745
746 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation
747 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from
748 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the
749 // next GC cycle.
750 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions);
751 }
752 // If !CONCURRENT, there's no value in expanding Mutator free set
753
754 ShenandoahHeapRegion* r = _regions->next();
755 // We update references for global, mixed, and young collections.
756 assert(_generation->is_mark_complete(), "Expected complete marking");
757 ShenandoahMarkingContext* const ctx = _heap->marking_context();
758 bool is_mixed = _heap->collection_set()->has_old_regions();
759 while (r != nullptr) {
760 HeapWord* update_watermark = r->get_update_watermark();
761 assert(update_watermark >= r->bottom(), "sanity");
762
763 log_debug(gc)("Update refs worker " UINT32_FORMAT ", looking at region %zu", worker_id, r->index());
764 if (r->is_active() && !r->is_cset()) {
765 if (r->is_young()) {
766 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
767 } else if (r->is_old()) {
768 if (_generation->is_global()) {
769
770 _heap->marked_object_oop_iterate(r, &cl, update_watermark);
771 }
772 // Otherwise, this is an old region in a young or mixed cycle. Process it during a second phase, below.
773 } else {
774 // Because updating of references runs concurrently, it is possible that a FREE inactive region transitions
775 // to a non-free active region while this loop is executing. Whenever this happens, the changing of a region's
776 // active status may propagate at a different speed than the changing of the region's affiliation.
777
778 // When we reach this control point, it is because a race has allowed a region's is_active() status to be seen
779 // by this thread before the region's affiliation() is seen by this thread.
780
781 // It's ok for this race to occur because the newly transformed region does not have any references to be
782 // updated.
783
784 assert(r->get_update_watermark() == r->bottom(),
785 "%s Region %zu is_active but not recognized as YOUNG or OLD so must be newly transitioned from FREE",
786 r->affiliation_name(), r->index());
787 }
788 }
789
790 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) {
791 return;
792 }
793
794 r = _regions->next();
795 }
796
797 if (_generation->is_young()) {
798 // Since this is generational and not GLOBAL, we have to process the remembered set. There's no remembered
799 // set processing if not in generational mode or if GLOBAL mode.
800
801 // After this thread has exhausted its traditional update-refs work, it continues with updating refs within
802 // remembered set. The remembered set workload is better balanced between threads, so threads that are "behind"
803 // can catch up with other threads during this phase, allowing all threads to work more effectively in parallel.
804 update_references_in_remembered_set(worker_id, cl, ctx, is_mixed);
805 }
806 }
807
808 template<class T>
809 void update_references_in_remembered_set(uint worker_id, T &cl, const ShenandoahMarkingContext* ctx, bool is_mixed) {
810
811 struct ShenandoahRegionChunk assignment;
812 ShenandoahScanRemembered* scanner = _heap->old_generation()->card_scan();
813
814 while (!_heap->check_cancelled_gc_and_yield(CONCURRENT) && _work_chunks->next(&assignment)) {
815 // Keep grabbing next work chunk to process until finished, or asked to yield
816 ShenandoahHeapRegion* r = assignment._r;
817 if (r->is_active() && !r->is_cset() && r->is_old()) {
818 HeapWord* start_of_range = r->bottom() + assignment._chunk_offset;
819 HeapWord* end_of_range = r->get_update_watermark();
820 if (end_of_range > start_of_range + assignment._chunk_size) {
821 end_of_range = start_of_range + assignment._chunk_size;
822 }
823
824 if (start_of_range >= end_of_range) {
825 continue;
826 }
827
828 // Old region in a young cycle or mixed cycle.
829 if (is_mixed) {
830 if (r->is_humongous()) {
831 // Need to examine both dirty and clean cards during mixed evac.
832 r->oop_iterate_humongous_slice_all(&cl,start_of_range, assignment._chunk_size);
833 } else {
834 // Since this is mixed evacuation, old regions that are candidates for collection have not been coalesced
835 // and filled. This will use mark bits to find objects that need to be updated.
836 update_references_in_old_region(cl, ctx, scanner, r, start_of_range, end_of_range);
837 }
838 } else {
839 // This is a young evacuation
840 size_t cluster_size = CardTable::card_size_in_words() * ShenandoahCardCluster::CardsPerCluster;
841 size_t clusters = assignment._chunk_size / cluster_size;
842 assert(clusters * cluster_size == assignment._chunk_size, "Chunk assignment must align on cluster boundaries");
843 scanner->process_region_slice(r, assignment._chunk_offset, clusters, end_of_range, &cl, true, worker_id);
844 }
845 }
846 }
847 }
848
849 template<class T>
850 void update_references_in_old_region(T &cl, const ShenandoahMarkingContext* ctx, ShenandoahScanRemembered* scanner,
851 const ShenandoahHeapRegion* r, HeapWord* start_of_range,
852 HeapWord* end_of_range) const {
853 // In case last object in my range spans boundary of my chunk, I may need to scan all the way to top()
854 ShenandoahObjectToOopBoundedClosure<T> objs(&cl, start_of_range, r->top());
855
856 // Any object that begins in a previous range is part of a different scanning assignment. Any object that
857 // starts after end_of_range is also not my responsibility. (Either allocated during evacuation, so does
858 // not hold pointers to from-space, or is beyond the range of my assigned work chunk.)
859
860 // Find the first object that begins in my range, if there is one. Note that `p` will be set to `end_of_range`
861 // when no live object is found in the range.
862 HeapWord* tams = ctx->top_at_mark_start(r);
863 HeapWord* p = get_first_object_start_word(ctx, scanner, tams, start_of_range, end_of_range);
864
865 while (p < end_of_range) {
866 // p is known to point to the beginning of marked object obj
867 oop obj = cast_to_oop(p);
868 objs.do_object(obj);
869 HeapWord* prev_p = p;
870 p += obj->size();
871 if (p < tams) {
872 p = ctx->get_next_marked_addr(p, tams);
873 // If there are no more marked objects before tams, this returns tams. Note that tams is
874 // either >= end_of_range, or tams is the start of an object that is marked.
875 }
876 assert(p != prev_p, "Lack of forward progress");
877 }
878 }
879
880 HeapWord* get_first_object_start_word(const ShenandoahMarkingContext* ctx, ShenandoahScanRemembered* scanner, HeapWord* tams,
881 HeapWord* start_of_range, HeapWord* end_of_range) const {
882 HeapWord* p = start_of_range;
883
884 if (p >= tams) {
885 // We cannot use ctx->is_marked(obj) to test whether an object begins at this address. Instead,
886 // we need to use the remembered set crossing map to advance p to the first object that starts
887 // within the enclosing card.
888 size_t card_index = scanner->card_index_for_addr(start_of_range);
889 while (true) {
890 HeapWord* first_object = scanner->first_object_in_card(card_index);
891 if (first_object != nullptr) {
892 p = first_object;
893 break;
894 } else if (scanner->addr_for_card_index(card_index + 1) < end_of_range) {
895 card_index++;
896 } else {
897 // Signal that no object was found in range
898 p = end_of_range;
899 break;
900 }
901 }
902 } else if (!ctx->is_marked(cast_to_oop(p))) {
903 p = ctx->get_next_marked_addr(p, tams);
904 // If there are no more marked objects before tams, this returns tams.
905 // Note that tams is either >= end_of_range, or tams is the start of an object that is marked.
906 }
907 return p;
908 }
909 };
910
911 void ShenandoahGenerationalHeap::update_heap_references(ShenandoahGeneration* generation, bool concurrent) {
912 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
913 const uint nworkers = workers()->active_workers();
914 ShenandoahRegionChunkIterator work_list(nworkers);
915 if (concurrent) {
916 ShenandoahGenerationalUpdateHeapRefsTask<true> task(generation, &_update_refs_iterator, &work_list);
917 workers()->run_task(&task);
918 } else {
919 ShenandoahGenerationalUpdateHeapRefsTask<false> task(generation, &_update_refs_iterator, &work_list);
920 workers()->run_task(&task);
921 }
922
923 if (ShenandoahEnableCardStats) {
924 // Only do this if we are collecting card stats
925 ShenandoahScanRemembered* card_scan = old_generation()->card_scan();
926 assert(card_scan != nullptr, "Card table must exist when card stats are enabled");
927 card_scan->log_card_stats(nworkers, CARD_STAT_UPDATE_REFS);
928 }
929 }
930
931 struct ShenandoahCompositeRegionClosure {
932 template<typename C1, typename C2>
933 class Closure : public ShenandoahHeapRegionClosure {
934 private:
935 C1 &_c1;
936 C2 &_c2;
937
938 public:
939 Closure(C1 &c1, C2 &c2) : ShenandoahHeapRegionClosure(), _c1(c1), _c2(c2) {}
940
941 void heap_region_do(ShenandoahHeapRegion* r) override {
942 _c1.heap_region_do(r);
943 _c2.heap_region_do(r);
944 }
945
946 bool is_thread_safe() override {
947 return _c1.is_thread_safe() && _c2.is_thread_safe();
948 }
949 };
950
951 template<typename C1, typename C2>
952 static Closure<C1, C2> of(C1 &c1, C2 &c2) {
953 return Closure<C1, C2>(c1, c2);
954 }
955 };
956
957 class ShenandoahUpdateRegionAges : public ShenandoahHeapRegionClosure {
958 private:
959 ShenandoahMarkingContext* _ctx;
960
961 public:
962 explicit ShenandoahUpdateRegionAges(ShenandoahMarkingContext* ctx) : _ctx(ctx) { }
963
964 void heap_region_do(ShenandoahHeapRegion* r) override {
965 // Maintenance of region age must follow evacuation in order to account for
966 // evacuation allocations within survivor regions. We consult region age during
967 // the subsequent evacuation to determine whether certain objects need to
968 // be promoted.
969 if (r->is_young() && r->is_active()) {
970 HeapWord *tams = _ctx->top_at_mark_start(r);
971 HeapWord *top = r->top();
972
973 // Allocations move the watermark when top moves. However, compacting
974 // objects will sometimes lower top beneath the watermark, after which,
975 // attempts to read the watermark will assert out (watermark should not be
976 // higher than top).
977 if (top > tams) {
978 // There have been allocations in this region since the start of the cycle.
979 // Any objects new to this region must not assimilate elevated age.
980 r->reset_age();
981 } else {
982 r->increment_age();
983 }
984 }
985 }
986
987 bool is_thread_safe() override {
988 return true;
989 }
990 };
991
992 void ShenandoahGenerationalHeap::final_update_refs_update_region_states() {
993 ShenandoahSynchronizePinnedRegionStates pins;
994 ShenandoahUpdateRegionAges ages(marking_context());
995 auto cl = ShenandoahCompositeRegionClosure::of(pins, ages);
996 parallel_heap_region_iterate(&cl);
997 }
998
999 void ShenandoahGenerationalHeap::complete_degenerated_cycle() {
1000 shenandoah_assert_heaplocked_or_safepoint();
1001 if (!old_generation()->is_parsable()) {
1002 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_coalesce_and_fill);
1003 coalesce_and_fill_old_regions(false);
1004 }
1005
1006 old_generation()->maybe_log_promotion_failure_stats(false);
1007 }
1008
1009 void ShenandoahGenerationalHeap::complete_concurrent_cycle() {
1010 if (!old_generation()->is_parsable()) {
1011 // Class unloading may render the card offsets unusable, so we must rebuild them before
1012 // the next remembered set scan. We _could_ let the control thread do this sometime after
1013 // the global cycle has completed and before the next young collection, but under memory
1014 // pressure the control thread may not have the time (that is, because it's running back
1015 // to back GCs). In that scenario, we would have to make the old regions parsable before
1016 // we could start a young collection. This could delay the start of the young cycle and
1017 // throw off the heuristics.
1018 entry_global_coalesce_and_fill();
1019 }
1020
1021 old_generation()->maybe_log_promotion_failure_stats(true);
1022 }
1023
1024 void ShenandoahGenerationalHeap::entry_global_coalesce_and_fill() {
1025 const char* msg = "Coalescing and filling old regions";
1026 ShenandoahConcurrentSubphase gc_phase(msg, ShenandoahPhaseTimings::conc_coalesce_and_fill);
1027
1028 TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters());
1029 EventMark em("%s", msg);
1030 ShenandoahWorkerScope scope(workers(),
1031 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
1032 "concurrent coalesce and fill");
1033
1034 coalesce_and_fill_old_regions(true);
1035 }
1036
1037 void ShenandoahGenerationalHeap::update_region_ages(ShenandoahMarkingContext* ctx) {
1038 ShenandoahUpdateRegionAges cl(ctx);
1039 parallel_heap_region_iterate(&cl);
1040 }