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