1 /* 2 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved. 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. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 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). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 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/shenandoahFreeSet.hpp" 30 #include "gc/shenandoah/shenandoahGenerationalControlThread.hpp" 31 #include "gc/shenandoah/shenandoahGenerationalEvacuationTask.hpp" 32 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp" 33 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 34 #include "gc/shenandoah/shenandoahHeapRegion.hpp" 35 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp" 36 #include "gc/shenandoah/shenandoahInitLogger.hpp" 37 #include "gc/shenandoah/shenandoahMemoryPool.hpp" 38 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" 39 #include "gc/shenandoah/shenandoahOldGeneration.hpp" 40 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 41 #include "gc/shenandoah/shenandoahRegulatorThread.hpp" 42 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp" 43 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp" 44 #include "gc/shenandoah/shenandoahYoungGeneration.hpp" 45 #include "gc/shenandoah/shenandoahUtils.hpp" 46 #include "logging/log.hpp" 47 #include "utilities/events.hpp" 48 49 50 class ShenandoahGenerationalInitLogger : public ShenandoahInitLogger { 51 public: 52 static void print() { 53 ShenandoahGenerationalInitLogger logger; 54 logger.print_all(); 55 } 56 57 void print_heap() override { 58 ShenandoahInitLogger::print_heap(); 59 60 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap(); 61 62 ShenandoahYoungGeneration* young = heap->young_generation(); 63 log_info(gc, init)("Young Generation Soft Size: " EXACTFMT, EXACTFMTARGS(young->soft_max_capacity())); 64 log_info(gc, init)("Young Generation Max: " EXACTFMT, EXACTFMTARGS(young->max_capacity())); 65 66 ShenandoahOldGeneration* old = heap->old_generation(); 67 log_info(gc, init)("Old Generation Soft Size: " EXACTFMT, EXACTFMTARGS(old->soft_max_capacity())); 68 log_info(gc, init)("Old Generation Max: " EXACTFMT, EXACTFMTARGS(old->max_capacity())); 69 } 70 71 protected: 72 void print_gc_specific() override { 73 ShenandoahInitLogger::print_gc_specific(); 74 75 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap(); 76 log_info(gc, init)("Young Heuristics: %s", heap->young_generation()->heuristics()->name()); 77 log_info(gc, init)("Old Heuristics: %s", heap->old_generation()->heuristics()->name()); 78 } 79 }; 80 81 size_t ShenandoahGenerationalHeap::calculate_min_plab() { 82 return align_up(PLAB::min_size(), CardTable::card_size_in_words()); 83 } 84 85 size_t ShenandoahGenerationalHeap::calculate_max_plab() { 86 size_t MaxTLABSizeWords = ShenandoahHeapRegion::max_tlab_size_words(); 87 return align_down(MaxTLABSizeWords, CardTable::card_size_in_words()); 88 } 89 90 // Returns size in bytes 91 size_t ShenandoahGenerationalHeap::unsafe_max_tlab_alloc(Thread *thread) const { 92 return MIN2(ShenandoahHeapRegion::max_tlab_size_bytes(), young_generation()->available()); 93 } 94 95 ShenandoahGenerationalHeap::ShenandoahGenerationalHeap(ShenandoahCollectorPolicy* policy) : 96 ShenandoahHeap(policy), 97 _age_census(nullptr), 98 _evac_tracker(new ShenandoahEvacuationTracker()), 99 _min_plab_size(calculate_min_plab()), 100 _max_plab_size(calculate_max_plab()), 101 _regulator_thread(nullptr), 102 _young_gen_memory_pool(nullptr), 103 _old_gen_memory_pool(nullptr) { 104 assert(is_aligned(_min_plab_size, CardTable::card_size_in_words()), "min_plab_size must be aligned"); 105 assert(is_aligned(_max_plab_size, CardTable::card_size_in_words()), "max_plab_size must be aligned"); 106 } 107 108 void ShenandoahGenerationalHeap::post_initialize() { 109 ShenandoahHeap::post_initialize(); 110 _age_census = new ShenandoahAgeCensus(); 111 } 112 113 void ShenandoahGenerationalHeap::print_init_logger() const { 114 ShenandoahGenerationalInitLogger logger; 115 logger.print_all(); 116 } 117 118 void ShenandoahGenerationalHeap::print_tracing_info() const { 119 ShenandoahHeap::print_tracing_info(); 120 121 LogTarget(Info, gc, stats) lt; 122 if (lt.is_enabled()) { 123 LogStream ls(lt); 124 ls.cr(); 125 ls.cr(); 126 evac_tracker()->print_global_on(&ls); 127 } 128 } 129 130 void ShenandoahGenerationalHeap::initialize_heuristics() { 131 // Initialize global generation and heuristics even in generational mode. 132 ShenandoahHeap::initialize_heuristics(); 133 134 // Max capacity is the maximum _allowed_ capacity. That is, the maximum allowed capacity 135 // for old would be total heap - minimum capacity of young. This means the sum of the maximum 136 // allowed for old and young could exceed the total heap size. It remains the case that the 137 // _actual_ capacity of young + old = total. 138 _generation_sizer.heap_size_changed(max_capacity()); 139 size_t initial_capacity_young = _generation_sizer.max_young_size(); 140 size_t max_capacity_young = _generation_sizer.max_young_size(); 141 size_t initial_capacity_old = max_capacity() - max_capacity_young; 142 size_t max_capacity_old = max_capacity() - initial_capacity_young; 143 144 _young_generation = new ShenandoahYoungGeneration(max_workers(), max_capacity_young, initial_capacity_young); 145 _old_generation = new ShenandoahOldGeneration(max_workers(), max_capacity_old, initial_capacity_old); 146 _young_generation->initialize_heuristics(mode()); 147 _old_generation->initialize_heuristics(mode()); 148 } 149 150 void ShenandoahGenerationalHeap::initialize_serviceability() { 151 assert(mode()->is_generational(), "Only for the generational mode"); 152 _young_gen_memory_pool = new ShenandoahYoungGenMemoryPool(this); 153 _old_gen_memory_pool = new ShenandoahOldGenMemoryPool(this); 154 cycle_memory_manager()->add_pool(_young_gen_memory_pool); 155 cycle_memory_manager()->add_pool(_old_gen_memory_pool); 156 stw_memory_manager()->add_pool(_young_gen_memory_pool); 157 stw_memory_manager()->add_pool(_old_gen_memory_pool); 158 } 159 160 GrowableArray<MemoryPool*> ShenandoahGenerationalHeap::memory_pools() { 161 assert(mode()->is_generational(), "Only for the generational mode"); 162 GrowableArray<MemoryPool*> memory_pools(2); 163 memory_pools.append(_young_gen_memory_pool); 164 memory_pools.append(_old_gen_memory_pool); 165 return memory_pools; 166 } 167 168 void ShenandoahGenerationalHeap::initialize_controller() { 169 auto control_thread = new ShenandoahGenerationalControlThread(); 170 _control_thread = control_thread; 171 _regulator_thread = new ShenandoahRegulatorThread(control_thread); 172 } 173 174 void ShenandoahGenerationalHeap::gc_threads_do(ThreadClosure* tcl) const { 175 if (!shenandoah_policy()->is_at_shutdown()) { 176 ShenandoahHeap::gc_threads_do(tcl); 177 tcl->do_thread(regulator_thread()); 178 } 179 } 180 181 void ShenandoahGenerationalHeap::stop() { 182 ShenandoahHeap::stop(); 183 regulator_thread()->stop(); 184 } 185 186 void ShenandoahGenerationalHeap::evacuate_collection_set(bool concurrent) { 187 ShenandoahRegionIterator regions; 188 ShenandoahGenerationalEvacuationTask task(this, ®ions, concurrent, false /* only promote regions */); 189 workers()->run_task(&task); 190 } 191 192 void ShenandoahGenerationalHeap::promote_regions_in_place(bool concurrent) { 193 ShenandoahRegionIterator regions; 194 ShenandoahGenerationalEvacuationTask task(this, ®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 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) { 201 // This thread went through the OOM during evac protocol and it is safe to return 202 // the forward pointer. It must not attempt to evacuate anymore. 203 return ShenandoahBarrierSet::resolve_forwarded(p); 204 } 205 206 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope"); 207 208 ShenandoahHeapRegion* r = heap_region_containing(p); 209 assert(!r->is_humongous(), "never evacuate humongous objects"); 210 211 ShenandoahAffiliation target_gen = r->affiliation(); 212 // gc_generation() can change asynchronously and should not be used here. 213 assert(active_generation() != nullptr, "Error"); 214 if (active_generation()->is_young() && target_gen == YOUNG_GENERATION) { 215 markWord mark = p->mark(); 216 if (mark.is_marked()) { 217 // Already forwarded. 218 return ShenandoahBarrierSet::resolve_forwarded(p); 219 } 220 221 if (mark.has_displaced_mark_helper()) { 222 // We don't want to deal with MT here just to ensure we read the right mark word. 223 // Skip the potential promotion attempt for this one. 224 } else if (r->age() + mark.age() >= age_census()->tenuring_threshold()) { 225 oop result = try_evacuate_object(p, thread, r, OLD_GENERATION); 226 if (result != nullptr) { 227 return result; 228 } 229 // If we failed to promote this aged object, we'll fall through to code below and evacuate to young-gen. 230 } 231 } 232 return try_evacuate_object(p, thread, r, target_gen); 233 } 234 235 // try_evacuate_object registers the object and dirties the associated remembered set information when evacuating 236 // to OLD_GENERATION. 237 oop ShenandoahGenerationalHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region, 238 ShenandoahAffiliation target_gen) { 239 bool alloc_from_lab = true; 240 bool has_plab = false; 241 HeapWord* copy = nullptr; 242 243 markWord mark = p->mark(); 244 if (ShenandoahForwarding::is_forwarded(mark)) { 245 return ShenandoahForwarding::get_forwardee(p); 246 } 247 size_t old_size = ShenandoahForwarding::size(p); 248 size_t size = p->copy_size(old_size, mark); 249 250 bool is_promotion = (target_gen == OLD_GENERATION) && from_region->is_young(); 251 252 #ifdef ASSERT 253 if (ShenandoahOOMDuringEvacALot && 254 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call 255 copy = nullptr; 256 } else { 257 #endif 258 if (UseTLAB) { 259 switch (target_gen) { 260 case YOUNG_GENERATION: { 261 copy = allocate_from_gclab(thread, size); 262 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) { 263 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting 264 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations. 265 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size()); 266 copy = allocate_from_gclab(thread, size); 267 // If we still get nullptr, we'll try a shared allocation below. 268 } 269 break; 270 } 271 case OLD_GENERATION: { 272 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 273 if (plab != nullptr) { 274 has_plab = true; 275 copy = allocate_from_plab(thread, size, is_promotion); 276 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::plab_size(thread)) && 277 ShenandoahThreadLocalData::plab_retries_enabled(thread)) { 278 // PLAB allocation failed because we are bumping up against the limit on old evacuation reserve or because 279 // the requested object does not fit within the current plab but the plab still has an "abundance" of memory, 280 // where abundance is defined as >= ShenGenHeap::plab_min_size(). In the former case, we try shrinking the 281 // desired PLAB size to the minimum and retry PLAB allocation to avoid cascading of shared memory allocations. 282 if (plab->words_remaining() < plab_min_size()) { 283 ShenandoahThreadLocalData::set_plab_size(thread, plab_min_size()); 284 copy = allocate_from_plab(thread, size, is_promotion); 285 // If we still get nullptr, we'll try a shared allocation below. 286 if (copy == nullptr) { 287 // If retry fails, don't continue to retry until we have success (probably in next GC pass) 288 ShenandoahThreadLocalData::disable_plab_retries(thread); 289 } 290 } 291 // else, copy still equals nullptr. this causes shared allocation below, preserving this plab for future needs. 292 } 293 } 294 break; 295 } 296 default: { 297 ShouldNotReachHere(); 298 break; 299 } 300 } 301 } 302 303 if (copy == nullptr) { 304 // If we failed to allocate in LAB, we'll try a shared allocation. 305 if (!is_promotion || !has_plab || (size > PLAB::min_size())) { 306 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen, is_promotion); 307 copy = allocate_memory(req); 308 alloc_from_lab = false; 309 } 310 // else, we leave copy equal to nullptr, signaling a promotion failure below if appropriate. 311 // We choose not to promote objects smaller than PLAB::min_size() by way of shared allocations, as this is too 312 // costly. Instead, we'll simply "evacuate" to young-gen memory (using a GCLAB) and will promote in a future 313 // evacuation pass. This condition is denoted by: is_promotion && has_plab && (size <= PLAB::min_size()) 314 } 315 #ifdef ASSERT 316 } 317 #endif 318 319 if (copy == nullptr) { 320 if (target_gen == OLD_GENERATION) { 321 if (from_region->is_young()) { 322 // Signal that promotion failed. Will evacuate this old object somewhere in young gen. 323 old_generation()->handle_failed_promotion(thread, size); 324 return nullptr; 325 } else { 326 // Remember that evacuation to old gen failed. We'll want to trigger a full gc to recover from this 327 // after the evacuation threads have finished. 328 old_generation()->handle_failed_evacuation(); 329 } 330 } 331 332 control_thread()->handle_alloc_failure_evac(size); 333 334 oom_evac_handler()->handle_out_of_memory_during_evacuation(); 335 336 return ShenandoahBarrierSet::resolve_forwarded(p); 337 } 338 339 // Copy the object: 340 NOT_PRODUCT(evac_tracker()->begin_evacuation(thread, size * HeapWordSize)); 341 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, old_size); 342 oop copy_val = cast_to_oop(copy); 343 344 // Update the age of the evacuated object 345 if (target_gen == YOUNG_GENERATION && is_aging_cycle()) { 346 ShenandoahHeap::increase_object_age(copy_val, from_region->age() + 1); 347 } 348 349 // Try to install the new forwarding pointer. 350 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val); 351 if (result == copy_val) { 352 // Successfully evacuated. Our copy is now the public one! 353 354 // This is necessary for virtual thread support. This uses the mark word without 355 // considering that it may now be a forwarding pointer (and could therefore crash). 356 // Secondarily, we do not want to spend cycles relativizing stack chunks for oops 357 // that lost the evacuation race (and will therefore not become visible). It is 358 // safe to do this on the public copy (this is also done during concurrent mark). 359 copy_val->initialize_hash_if_necessary(p); 360 ContinuationGCSupport::relativize_stack_chunk(copy_val); 361 362 // Record that the evacuation succeeded 363 NOT_PRODUCT(evac_tracker()->end_evacuation(thread, size * HeapWordSize)); 364 365 if (target_gen == OLD_GENERATION) { 366 old_generation()->handle_evacuation(copy, size, from_region->is_young()); 367 } else { 368 // When copying to the old generation above, we don't care 369 // about recording object age in the census stats. 370 assert(target_gen == YOUNG_GENERATION, "Error"); 371 // We record this census only when simulating pre-adaptive tenuring behavior, or 372 // when we have been asked to record the census at evacuation rather than at mark 373 if (ShenandoahGenerationalCensusAtEvac || !ShenandoahGenerationalAdaptiveTenuring) { 374 evac_tracker()->record_age(thread, size * HeapWordSize, ShenandoahHeap::get_object_age(copy_val)); 375 } 376 } 377 shenandoah_assert_correct(nullptr, copy_val); 378 return copy_val; 379 } else { 380 // Failed to evacuate. We need to deal with the object that is left behind. Since this 381 // new allocation is certainly after TAMS, it will be considered live in the next cycle. 382 // But if it happens to contain references to evacuated regions, those references would 383 // not get updated for this stale copy during this cycle, and we will crash while scanning 384 // it the next cycle. 385 if (alloc_from_lab) { 386 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next 387 // object will overwrite this stale copy, or the filler object on LAB retirement will 388 // do this. 389 switch (target_gen) { 390 case YOUNG_GENERATION: { 391 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size); 392 break; 393 } 394 case OLD_GENERATION: { 395 ShenandoahThreadLocalData::plab(thread)->undo_allocation(copy, size); 396 if (is_promotion) { 397 ShenandoahThreadLocalData::subtract_from_plab_promoted(thread, size * HeapWordSize); 398 } 399 break; 400 } 401 default: { 402 ShouldNotReachHere(); 403 break; 404 } 405 } 406 } else { 407 // For non-LAB allocations, we have no way to retract the allocation, and 408 // have to explicitly overwrite the copy with the filler object. With that overwrite, 409 // we have to keep the fwdptr initialized and pointing to our (stale) copy. 410 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size"); 411 fill_with_object(copy, size); 412 shenandoah_assert_correct(nullptr, copy_val); 413 // For non-LAB allocations, the object has already been registered 414 } 415 shenandoah_assert_correct(nullptr, result); 416 return result; 417 } 418 } 419 420 inline HeapWord* ShenandoahGenerationalHeap::allocate_from_plab(Thread* thread, size_t size, bool is_promotion) { 421 assert(UseTLAB, "TLABs should be enabled"); 422 423 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 424 HeapWord* obj; 425 426 if (plab == nullptr) { 427 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(), "Performance: thread should have PLAB: %s", thread->name()); 428 // No PLABs in this thread, fallback to shared allocation 429 return nullptr; 430 } else if (is_promotion && !ShenandoahThreadLocalData::allow_plab_promotions(thread)) { 431 return nullptr; 432 } 433 // if plab->word_size() <= 0, thread's plab not yet initialized for this pass, so allow_plab_promotions() is not trustworthy 434 obj = plab->allocate(size); 435 if ((obj == nullptr) && (plab->words_remaining() < plab_min_size())) { 436 // allocate_from_plab_slow will establish allow_plab_promotions(thread) for future invocations 437 obj = allocate_from_plab_slow(thread, size, is_promotion); 438 } 439 // if plab->words_remaining() >= ShenGenHeap::heap()->plab_min_size(), just return nullptr so we can use a shared allocation 440 if (obj == nullptr) { 441 return nullptr; 442 } 443 444 if (is_promotion) { 445 ShenandoahThreadLocalData::add_to_plab_promoted(thread, size * HeapWordSize); 446 } 447 return obj; 448 } 449 450 // Establish a new PLAB and allocate size HeapWords within it. 451 HeapWord* ShenandoahGenerationalHeap::allocate_from_plab_slow(Thread* thread, size_t size, bool is_promotion) { 452 // New object should fit the PLAB size 453 454 assert(mode()->is_generational(), "PLABs only relevant to generational GC"); 455 const size_t plab_min_size = this->plab_min_size(); 456 // PLABs are aligned to card boundaries to avoid synchronization with concurrent 457 // allocations in other PLABs. 458 const size_t min_size = (size > plab_min_size)? align_up(size, CardTable::card_size_in_words()): plab_min_size; 459 460 // Figure out size of new PLAB, using value determined at last refill. 461 size_t cur_size = ShenandoahThreadLocalData::plab_size(thread); 462 if (cur_size == 0) { 463 cur_size = plab_min_size; 464 } 465 466 // Expand aggressively, doubling at each refill in this epoch, ceiling at plab_max_size() 467 size_t future_size = MIN2(cur_size * 2, plab_max_size()); 468 // Doubling, starting at a card-multiple, should give us a card-multiple. (Ceiling and floor 469 // are card multiples.) 470 assert(is_aligned(future_size, CardTable::card_size_in_words()), "Card multiple by construction, future_size: %zu" 471 ", card_size: %zu, cur_size: %zu, max: %zu", 472 future_size, (size_t) CardTable::card_size_in_words(), cur_size, plab_max_size()); 473 474 // Record new heuristic value even if we take any shortcut. This captures 475 // the case when moderately-sized objects always take a shortcut. At some point, 476 // heuristics should catch up with them. Note that the requested cur_size may 477 // not be honored, but we remember that this is the preferred size. 478 log_debug(gc, free)("Set new PLAB size: %zu", future_size); 479 ShenandoahThreadLocalData::set_plab_size(thread, future_size); 480 if (cur_size < size) { 481 // The PLAB to be allocated is still not large enough to hold the object. Fall back to shared allocation. 482 // This avoids retiring perfectly good PLABs in order to represent a single large object allocation. 483 log_debug(gc, free)("Current PLAB size (%zu) is too small for %zu", cur_size, size); 484 return nullptr; 485 } 486 487 // Retire current PLAB, and allocate a new one. 488 PLAB* plab = ShenandoahThreadLocalData::plab(thread); 489 if (plab->words_remaining() < plab_min_size) { 490 // Retire current PLAB. This takes care of any PLAB book-keeping. 491 // retire_plab() registers the remnant filler object with the remembered set scanner without a lock. 492 // Since PLABs are card-aligned, concurrent registrations in other PLABs don't interfere. 493 retire_plab(plab, thread); 494 495 size_t actual_size = 0; 496 HeapWord* plab_buf = allocate_new_plab(min_size, cur_size, &actual_size); 497 if (plab_buf == nullptr) { 498 if (min_size == plab_min_size) { 499 // Disable PLAB promotions for this thread because we cannot even allocate a minimal PLAB. This allows us 500 // to fail faster on subsequent promotion attempts. 501 ShenandoahThreadLocalData::disable_plab_promotions(thread); 502 } 503 return nullptr; 504 } else { 505 ShenandoahThreadLocalData::enable_plab_retries(thread); 506 } 507 // Since the allocated PLAB may have been down-sized for alignment, plab->allocate(size) below may still fail. 508 if (ZeroTLAB) { 509 // ... and clear it. 510 Copy::zero_to_words(plab_buf, actual_size); 511 } else { 512 // ...and zap just allocated object. 513 #ifdef ASSERT 514 // Skip mangling the space corresponding to the object header to 515 // ensure that the returned space is not considered parsable by 516 // any concurrent GC thread. 517 size_t hdr_size = oopDesc::header_size(); 518 Copy::fill_to_words(plab_buf + hdr_size, actual_size - hdr_size, badHeapWordVal); 519 #endif // ASSERT 520 } 521 assert(is_aligned(actual_size, CardTable::card_size_in_words()), "Align by design"); 522 plab->set_buf(plab_buf, actual_size); 523 if (is_promotion && !ShenandoahThreadLocalData::allow_plab_promotions(thread)) { 524 return nullptr; 525 } 526 return plab->allocate(size); 527 } else { 528 // If there's still at least min_size() words available within the current plab, don't retire it. Let's nibble 529 // away on this plab as long as we can. Meanwhile, return nullptr to force this particular allocation request 530 // to be satisfied with a shared allocation. By packing more promotions into the previously allocated PLAB, we 531 // reduce the likelihood of evacuation failures, and we reduce the need for downsizing our PLABs. 532 return nullptr; 533 } 534 } 535 536 HeapWord* ShenandoahGenerationalHeap::allocate_new_plab(size_t min_size, size_t word_size, size_t* actual_size) { 537 // Align requested sizes to card-sized multiples. Align down so that we don't violate max size of TLAB. 538 assert(is_aligned(min_size, CardTable::card_size_in_words()), "Align by design"); 539 assert(word_size >= min_size, "Requested PLAB is too small"); 540 541 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_plab(min_size, word_size); 542 // Note that allocate_memory() sets a thread-local flag to prohibit further promotions by this thread 543 // if we are at risk of infringing on the old-gen evacuation budget. 544 HeapWord* res = allocate_memory(req); 545 if (res != nullptr) { 546 *actual_size = req.actual_size(); 547 } else { 548 *actual_size = 0; 549 } 550 assert(is_aligned(res, CardTable::card_size_in_words()), "Align by design"); 551 return res; 552 } 553 554 void ShenandoahGenerationalHeap::retire_plab(PLAB* plab, Thread* thread) { 555 // We don't enforce limits on plab evacuations. We let it consume all available old-gen memory in order to reduce 556 // probability of an evacuation failure. We do enforce limits on promotion, to make sure that excessive promotion 557 // does not result in an old-gen evacuation failure. Note that a failed promotion is relatively harmless. Any 558 // object that fails to promote in the current cycle will be eligible for promotion in a subsequent cycle. 559 560 // When the plab was instantiated, its entirety was treated as if the entire buffer was going to be dedicated to 561 // promotions. Now that we are retiring the buffer, we adjust for the reality that the plab is not entirely promotions. 562 // 1. Some of the plab may have been dedicated to evacuations. 563 // 2. Some of the plab may have been abandoned due to waste (at the end of the plab). 564 size_t not_promoted = 565 ShenandoahThreadLocalData::get_plab_actual_size(thread) - ShenandoahThreadLocalData::get_plab_promoted(thread); 566 ShenandoahThreadLocalData::reset_plab_promoted(thread); 567 ShenandoahThreadLocalData::set_plab_actual_size(thread, 0); 568 if (not_promoted > 0) { 569 old_generation()->unexpend_promoted(not_promoted); 570 } 571 const size_t original_waste = plab->waste(); 572 HeapWord* const top = plab->top(); 573 574 // plab->retire() overwrites unused memory between plab->top() and plab->hard_end() with a dummy object to make memory parsable. 575 // It adds the size of this unused memory, in words, to plab->waste(). 576 plab->retire(); 577 if (top != nullptr && plab->waste() > original_waste && is_in_old(top)) { 578 // If retiring the plab created a filler object, then we need to register it with our card scanner so it can 579 // safely walk the region backing the plab. 580 log_debug(gc)("retire_plab() is registering remnant of size %zu at " PTR_FORMAT, 581 plab->waste() - original_waste, p2i(top)); 582 // No lock is necessary because the PLAB memory is aligned on card boundaries. 583 old_generation()->card_scan()->register_object_without_lock(top); 584 } 585 } 586 587 void ShenandoahGenerationalHeap::retire_plab(PLAB* plab) { 588 Thread* thread = Thread::current(); 589 retire_plab(plab, thread); 590 } 591 592 ShenandoahGenerationalHeap::TransferResult ShenandoahGenerationalHeap::balance_generations() { 593 shenandoah_assert_heaplocked_or_safepoint(); 594 595 ShenandoahOldGeneration* old_gen = old_generation(); 596 const ssize_t old_region_balance = old_gen->get_region_balance(); 597 old_gen->set_region_balance(0); 598 599 if (old_region_balance > 0) { 600 const auto old_region_surplus = checked_cast<size_t>(old_region_balance); 601 const bool success = generation_sizer()->transfer_to_young(old_region_surplus); 602 return TransferResult { 603 success, old_region_surplus, "young" 604 }; 605 } 606 607 if (old_region_balance < 0) { 608 const auto old_region_deficit = checked_cast<size_t>(-old_region_balance); 609 const bool success = generation_sizer()->transfer_to_old(old_region_deficit); 610 if (!success) { 611 old_gen->handle_failed_transfer(); 612 } 613 return TransferResult { 614 success, old_region_deficit, "old" 615 }; 616 } 617 618 return TransferResult {true, 0, "none"}; 619 } 620 621 // Make sure old-generation is large enough, but no larger than is necessary, to hold mixed evacuations 622 // and promotions, if we anticipate either. Any deficit is provided by the young generation, subject to 623 // xfer_limit, and any surplus is transferred to the young generation. 624 // xfer_limit is the maximum we're able to transfer from young to old. 625 void ShenandoahGenerationalHeap::compute_old_generation_balance(size_t old_xfer_limit, size_t old_cset_regions) { 626 627 // We can limit the old reserve to the size of anticipated promotions: 628 // max_old_reserve is an upper bound on memory evacuated from old and promoted to old, 629 // clamped by the old generation space available. 630 // 631 // Here's the algebra. 632 // Let SOEP = ShenandoahOldEvacRatioPercent, 633 // OE = old evac, 634 // YE = young evac, and 635 // TE = total evac = OE + YE 636 // By definition: 637 // SOEP/100 = OE/TE 638 // = OE/(OE+YE) 639 // => SOEP/(100-SOEP) = OE/((OE+YE)-OE) // componendo-dividendo: If a/b = c/d, then a/(b-a) = c/(d-c) 640 // = OE/YE 641 // => OE = YE*SOEP/(100-SOEP) 642 643 // We have to be careful in the event that SOEP is set to 100 by the user. 644 assert(ShenandoahOldEvacRatioPercent <= 100, "Error"); 645 const size_t old_available = old_generation()->available(); 646 // The free set will reserve this amount of memory to hold young evacuations 647 const size_t young_reserve = (young_generation()->max_capacity() * ShenandoahEvacReserve) / 100; 648 649 // In the case that ShenandoahOldEvacRatioPercent equals 100, max_old_reserve is limited only by xfer_limit. 650 651 const double bound_on_old_reserve = old_available + old_xfer_limit + young_reserve; 652 const double max_old_reserve = (ShenandoahOldEvacRatioPercent == 100)? 653 bound_on_old_reserve: MIN2(double(young_reserve * ShenandoahOldEvacRatioPercent) / double(100 - ShenandoahOldEvacRatioPercent), 654 bound_on_old_reserve); 655 656 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 657 658 // Decide how much old space we should reserve for a mixed collection 659 double reserve_for_mixed = 0; 660 if (old_generation()->has_unprocessed_collection_candidates()) { 661 // We want this much memory to be unfragmented in order to reliably evacuate old. This is conservative because we 662 // may not evacuate the entirety of unprocessed candidates in a single mixed evacuation. 663 const double max_evac_need = (double(old_generation()->unprocessed_collection_candidates_live_memory()) * ShenandoahOldEvacWaste); 664 assert(old_available >= old_generation()->free_unaffiliated_regions() * region_size_bytes, 665 "Unaffiliated available must be less than total available"); 666 const double old_fragmented_available = double(old_available - old_generation()->free_unaffiliated_regions() * region_size_bytes); 667 reserve_for_mixed = max_evac_need + old_fragmented_available; 668 if (reserve_for_mixed > max_old_reserve) { 669 reserve_for_mixed = max_old_reserve; 670 } 671 } 672 673 // Decide how much space we should reserve for promotions from young 674 size_t reserve_for_promo = 0; 675 const size_t promo_load = old_generation()->get_promotion_potential(); 676 const bool doing_promotions = promo_load > 0; 677 if (doing_promotions) { 678 // We're promoting and have a bound on the maximum amount that can be promoted 679 assert(max_old_reserve >= reserve_for_mixed, "Sanity"); 680 const size_t available_for_promotions = max_old_reserve - reserve_for_mixed; 681 reserve_for_promo = MIN2((size_t)(promo_load * ShenandoahPromoEvacWaste), available_for_promotions); 682 } 683 684 // This is the total old we want to ideally reserve 685 const size_t old_reserve = reserve_for_mixed + reserve_for_promo; 686 assert(old_reserve <= max_old_reserve, "cannot reserve more than max for old evacuations"); 687 688 // We now check if the old generation is running a surplus or a deficit. 689 const size_t max_old_available = old_generation()->available() + old_cset_regions * region_size_bytes; 690 if (max_old_available >= old_reserve) { 691 // We are running a surplus, so the old region surplus can go to young 692 const size_t old_surplus = (max_old_available - old_reserve) / region_size_bytes; 693 const size_t unaffiliated_old_regions = old_generation()->free_unaffiliated_regions() + old_cset_regions; 694 const size_t old_region_surplus = MIN2(old_surplus, unaffiliated_old_regions); 695 old_generation()->set_region_balance(checked_cast<ssize_t>(old_region_surplus)); 696 } else { 697 // We are running a deficit which we'd like to fill from young. 698 // Ignore that this will directly impact young_generation()->max_capacity(), 699 // indirectly impacting young_reserve and old_reserve. These computations are conservative. 700 // Note that deficit is rounded up by one region. 701 const size_t old_need = (old_reserve - max_old_available + region_size_bytes - 1) / region_size_bytes; 702 const size_t max_old_region_xfer = old_xfer_limit / region_size_bytes; 703 704 // Round down the regions we can transfer from young to old. If we're running short 705 // on young-gen memory, we restrict the xfer. Old-gen collection activities will be 706 // curtailed if the budget is restricted. 707 const size_t old_region_deficit = MIN2(old_need, max_old_region_xfer); 708 old_generation()->set_region_balance(0 - checked_cast<ssize_t>(old_region_deficit)); 709 } 710 } 711 712 void ShenandoahGenerationalHeap::reset_generation_reserves() { 713 young_generation()->set_evacuation_reserve(0); 714 old_generation()->set_evacuation_reserve(0); 715 old_generation()->set_promoted_reserve(0); 716 } 717 718 void ShenandoahGenerationalHeap::TransferResult::print_on(const char* when, outputStream* ss) const { 719 auto heap = ShenandoahGenerationalHeap::heap(); 720 ShenandoahYoungGeneration* const young_gen = heap->young_generation(); 721 ShenandoahOldGeneration* const old_gen = heap->old_generation(); 722 const size_t young_available = young_gen->available(); 723 const size_t old_available = old_gen->available(); 724 ss->print_cr("After %s, %s %zu regions to %s to prepare for next gc, old available: " 725 PROPERFMT ", young_available: " PROPERFMT, 726 when, 727 success? "successfully transferred": "failed to transfer", region_count, region_destination, 728 PROPERFMTARGS(old_available), PROPERFMTARGS(young_available)); 729 } 730 731 void ShenandoahGenerationalHeap::coalesce_and_fill_old_regions(bool concurrent) { 732 class ShenandoahGlobalCoalesceAndFill : public WorkerTask { 733 private: 734 ShenandoahPhaseTimings::Phase _phase; 735 ShenandoahRegionIterator _regions; 736 public: 737 explicit ShenandoahGlobalCoalesceAndFill(ShenandoahPhaseTimings::Phase phase) : 738 WorkerTask("Shenandoah Global Coalesce"), 739 _phase(phase) {} 740 741 void work(uint worker_id) override { 742 ShenandoahWorkerTimingsTracker timer(_phase, 743 ShenandoahPhaseTimings::ScanClusters, 744 worker_id, true); 745 ShenandoahHeapRegion* region; 746 while ((region = _regions.next()) != nullptr) { 747 // old region is not in the collection set and was not immediately trashed 748 if (region->is_old() && region->is_active() && !region->is_humongous()) { 749 // Reset the coalesce and fill boundary because this is a global collect 750 // and cannot be preempted by young collects. We want to be sure the entire 751 // region is coalesced here and does not resume from a previously interrupted 752 // or completed coalescing. 753 region->begin_preemptible_coalesce_and_fill(); 754 region->oop_coalesce_and_fill(false); 755 } 756 } 757 } 758 }; 759 760 ShenandoahPhaseTimings::Phase phase = concurrent ? 761 ShenandoahPhaseTimings::conc_coalesce_and_fill : 762 ShenandoahPhaseTimings::degen_gc_coalesce_and_fill; 763 764 // This is not cancellable 765 ShenandoahGlobalCoalesceAndFill coalesce(phase); 766 workers()->run_task(&coalesce); 767 old_generation()->set_parsable(true); 768 } 769 770 template<bool CONCURRENT> 771 class ShenandoahGenerationalUpdateHeapRefsTask : public WorkerTask { 772 private: 773 ShenandoahGenerationalHeap* _heap; 774 ShenandoahRegionIterator* _regions; 775 ShenandoahRegionChunkIterator* _work_chunks; 776 777 public: 778 explicit ShenandoahGenerationalUpdateHeapRefsTask(ShenandoahRegionIterator* regions, 779 ShenandoahRegionChunkIterator* work_chunks) : 780 WorkerTask("Shenandoah Update References"), 781 _heap(ShenandoahGenerationalHeap::heap()), 782 _regions(regions), 783 _work_chunks(work_chunks) 784 { 785 bool old_bitmap_stable = _heap->old_generation()->is_mark_complete(); 786 log_debug(gc, remset)("Update refs, scan remembered set using bitmap: %s", BOOL_TO_STR(old_bitmap_stable)); 787 } 788 789 void work(uint worker_id) { 790 if (CONCURRENT) { 791 ShenandoahConcurrentWorkerSession worker_session(worker_id); 792 ShenandoahSuspendibleThreadSetJoiner stsj; 793 do_work<ShenandoahConcUpdateRefsClosure>(worker_id); 794 } else { 795 ShenandoahParallelWorkerSession worker_session(worker_id); 796 do_work<ShenandoahNonConcUpdateRefsClosure>(worker_id); 797 } 798 } 799 800 private: 801 template<class T> 802 void do_work(uint worker_id) { 803 T cl; 804 805 if (CONCURRENT && (worker_id == 0)) { 806 // We ask the first worker to replenish the Mutator free set by moving regions previously reserved to hold the 807 // results of evacuation. These reserves are no longer necessary because evacuation has completed. 808 size_t cset_regions = _heap->collection_set()->count(); 809 810 // Now that evacuation is done, we can reassign any regions that had been reserved to hold the results of evacuation 811 // to the mutator free set. At the end of GC, we will have cset_regions newly evacuated fully empty regions from 812 // which we will be able to replenish the Collector free set and the OldCollector free set in preparation for the 813 // next GC cycle. 814 _heap->free_set()->move_regions_from_collector_to_mutator(cset_regions); 815 } 816 // If !CONCURRENT, there's no value in expanding Mutator free set 817 818 ShenandoahHeapRegion* r = _regions->next(); 819 // We update references for global, old, and young collections. 820 ShenandoahGeneration* const gc_generation = _heap->gc_generation(); 821 shenandoah_assert_generations_reconciled(); 822 assert(gc_generation->is_mark_complete(), "Expected complete marking"); 823 ShenandoahMarkingContext* const ctx = _heap->marking_context(); 824 bool is_mixed = _heap->collection_set()->has_old_regions(); 825 while (r != nullptr) { 826 HeapWord* update_watermark = r->get_update_watermark(); 827 assert(update_watermark >= r->bottom(), "sanity"); 828 829 log_debug(gc)("Update refs worker " UINT32_FORMAT ", looking at region %zu", worker_id, r->index()); 830 bool region_progress = false; 831 if (r->is_active() && !r->is_cset()) { 832 if (r->is_young()) { 833 _heap->marked_object_oop_iterate(r, &cl, update_watermark); 834 region_progress = true; 835 } else if (r->is_old()) { 836 if (gc_generation->is_global()) { 837 838 _heap->marked_object_oop_iterate(r, &cl, update_watermark); 839 region_progress = true; 840 } 841 // Otherwise, this is an old region in a young or mixed cycle. Process it during a second phase, below. 842 // Don't bother to report pacing progress in this case. 843 } else { 844 // Because updating of references runs concurrently, it is possible that a FREE inactive region transitions 845 // to a non-free active region while this loop is executing. Whenever this happens, the changing of a region's 846 // active status may propagate at a different speed than the changing of the region's affiliation. 847 848 // When we reach this control point, it is because a race has allowed a region's is_active() status to be seen 849 // by this thread before the region's affiliation() is seen by this thread. 850 851 // It's ok for this race to occur because the newly transformed region does not have any references to be 852 // updated. 853 854 assert(r->get_update_watermark() == r->bottom(), 855 "%s Region %zu is_active but not recognized as YOUNG or OLD so must be newly transitioned from FREE", 856 r->affiliation_name(), r->index()); 857 } 858 } 859 860 if (region_progress && ShenandoahPacing) { 861 _heap->pacer()->report_update_refs(pointer_delta(update_watermark, r->bottom())); 862 } 863 864 if (_heap->check_cancelled_gc_and_yield(CONCURRENT)) { 865 return; 866 } 867 868 r = _regions->next(); 869 } 870 871 if (!gc_generation->is_global()) { 872 // Since this is generational and not GLOBAL, we have to process the remembered set. There's no remembered 873 // set processing if not in generational mode or if GLOBAL mode. 874 875 // After this thread has exhausted its traditional update-refs work, it continues with updating refs within 876 // remembered set. The remembered set workload is better balanced between threads, so threads that are "behind" 877 // can catch up with other threads during this phase, allowing all threads to work more effectively in parallel. 878 update_references_in_remembered_set(worker_id, cl, ctx, is_mixed); 879 } 880 } 881 882 template<class T> 883 void update_references_in_remembered_set(uint worker_id, T &cl, const ShenandoahMarkingContext* ctx, bool is_mixed) { 884 885 struct ShenandoahRegionChunk assignment; 886 ShenandoahScanRemembered* scanner = _heap->old_generation()->card_scan(); 887 888 while (!_heap->check_cancelled_gc_and_yield(CONCURRENT) && _work_chunks->next(&assignment)) { 889 // Keep grabbing next work chunk to process until finished, or asked to yield 890 ShenandoahHeapRegion* r = assignment._r; 891 if (r->is_active() && !r->is_cset() && r->is_old()) { 892 HeapWord* start_of_range = r->bottom() + assignment._chunk_offset; 893 HeapWord* end_of_range = r->get_update_watermark(); 894 if (end_of_range > start_of_range + assignment._chunk_size) { 895 end_of_range = start_of_range + assignment._chunk_size; 896 } 897 898 if (start_of_range >= end_of_range) { 899 continue; 900 } 901 902 // Old region in a young cycle or mixed cycle. 903 if (is_mixed) { 904 if (r->is_humongous()) { 905 // Need to examine both dirty and clean cards during mixed evac. 906 r->oop_iterate_humongous_slice_all(&cl,start_of_range, assignment._chunk_size); 907 } else { 908 // Since this is mixed evacuation, old regions that are candidates for collection have not been coalesced 909 // and filled. This will use mark bits to find objects that need to be updated. 910 update_references_in_old_region(cl, ctx, scanner, r, start_of_range, end_of_range); 911 } 912 } else { 913 // This is a young evacuation 914 size_t cluster_size = CardTable::card_size_in_words() * ShenandoahCardCluster::CardsPerCluster; 915 size_t clusters = assignment._chunk_size / cluster_size; 916 assert(clusters * cluster_size == assignment._chunk_size, "Chunk assignment must align on cluster boundaries"); 917 scanner->process_region_slice(r, assignment._chunk_offset, clusters, end_of_range, &cl, true, worker_id); 918 } 919 920 if (ShenandoahPacing) { 921 _heap->pacer()->report_update_refs(pointer_delta(end_of_range, start_of_range)); 922 } 923 } 924 } 925 } 926 927 template<class T> 928 void update_references_in_old_region(T &cl, const ShenandoahMarkingContext* ctx, ShenandoahScanRemembered* scanner, 929 const ShenandoahHeapRegion* r, HeapWord* start_of_range, 930 HeapWord* end_of_range) const { 931 // In case last object in my range spans boundary of my chunk, I may need to scan all the way to top() 932 ShenandoahObjectToOopBoundedClosure<T> objs(&cl, start_of_range, r->top()); 933 934 // Any object that begins in a previous range is part of a different scanning assignment. Any object that 935 // starts after end_of_range is also not my responsibility. (Either allocated during evacuation, so does 936 // not hold pointers to from-space, or is beyond the range of my assigned work chunk.) 937 938 // Find the first object that begins in my range, if there is one. Note that `p` will be set to `end_of_range` 939 // when no live object is found in the range. 940 HeapWord* tams = ctx->top_at_mark_start(r); 941 HeapWord* p = get_first_object_start_word(ctx, scanner, tams, start_of_range, end_of_range); 942 943 while (p < end_of_range) { 944 // p is known to point to the beginning of marked object obj 945 oop obj = cast_to_oop(p); 946 objs.do_object(obj); 947 HeapWord* prev_p = p; 948 p += obj->size(); 949 if (p < tams) { 950 p = ctx->get_next_marked_addr(p, tams); 951 // If there are no more marked objects before tams, this returns tams. Note that tams is 952 // either >= end_of_range, or tams is the start of an object that is marked. 953 } 954 assert(p != prev_p, "Lack of forward progress"); 955 } 956 } 957 958 HeapWord* get_first_object_start_word(const ShenandoahMarkingContext* ctx, ShenandoahScanRemembered* scanner, HeapWord* tams, 959 HeapWord* start_of_range, HeapWord* end_of_range) const { 960 HeapWord* p = start_of_range; 961 962 if (p >= tams) { 963 // We cannot use ctx->is_marked(obj) to test whether an object begins at this address. Instead, 964 // we need to use the remembered set crossing map to advance p to the first object that starts 965 // within the enclosing card. 966 size_t card_index = scanner->card_index_for_addr(start_of_range); 967 while (true) { 968 HeapWord* first_object = scanner->first_object_in_card(card_index); 969 if (first_object != nullptr) { 970 p = first_object; 971 break; 972 } else if (scanner->addr_for_card_index(card_index + 1) < end_of_range) { 973 card_index++; 974 } else { 975 // Signal that no object was found in range 976 p = end_of_range; 977 break; 978 } 979 } 980 } else if (!ctx->is_marked(cast_to_oop(p))) { 981 p = ctx->get_next_marked_addr(p, tams); 982 // If there are no more marked objects before tams, this returns tams. 983 // Note that tams is either >= end_of_range, or tams is the start of an object that is marked. 984 } 985 return p; 986 } 987 }; 988 989 void ShenandoahGenerationalHeap::update_heap_references(bool concurrent) { 990 assert(!is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); 991 const uint nworkers = workers()->active_workers(); 992 ShenandoahRegionChunkIterator work_list(nworkers); 993 if (concurrent) { 994 ShenandoahGenerationalUpdateHeapRefsTask<true> task(&_update_refs_iterator, &work_list); 995 workers()->run_task(&task); 996 } else { 997 ShenandoahGenerationalUpdateHeapRefsTask<false> task(&_update_refs_iterator, &work_list); 998 workers()->run_task(&task); 999 } 1000 1001 if (ShenandoahEnableCardStats) { 1002 // Only do this if we are collecting card stats 1003 ShenandoahScanRemembered* card_scan = old_generation()->card_scan(); 1004 assert(card_scan != nullptr, "Card table must exist when card stats are enabled"); 1005 card_scan->log_card_stats(nworkers, CARD_STAT_UPDATE_REFS); 1006 } 1007 } 1008 1009 struct ShenandoahCompositeRegionClosure { 1010 template<typename C1, typename C2> 1011 class Closure : public ShenandoahHeapRegionClosure { 1012 private: 1013 C1 &_c1; 1014 C2 &_c2; 1015 1016 public: 1017 Closure(C1 &c1, C2 &c2) : ShenandoahHeapRegionClosure(), _c1(c1), _c2(c2) {} 1018 1019 void heap_region_do(ShenandoahHeapRegion* r) override { 1020 _c1.heap_region_do(r); 1021 _c2.heap_region_do(r); 1022 } 1023 1024 bool is_thread_safe() override { 1025 return _c1.is_thread_safe() && _c2.is_thread_safe(); 1026 } 1027 }; 1028 1029 template<typename C1, typename C2> 1030 static Closure<C1, C2> of(C1 &c1, C2 &c2) { 1031 return Closure<C1, C2>(c1, c2); 1032 } 1033 }; 1034 1035 class ShenandoahUpdateRegionAges : public ShenandoahHeapRegionClosure { 1036 private: 1037 ShenandoahMarkingContext* _ctx; 1038 1039 public: 1040 explicit ShenandoahUpdateRegionAges(ShenandoahMarkingContext* ctx) : _ctx(ctx) { } 1041 1042 void heap_region_do(ShenandoahHeapRegion* r) override { 1043 // Maintenance of region age must follow evacuation in order to account for 1044 // evacuation allocations within survivor regions. We consult region age during 1045 // the subsequent evacuation to determine whether certain objects need to 1046 // be promoted. 1047 if (r->is_young() && r->is_active()) { 1048 HeapWord *tams = _ctx->top_at_mark_start(r); 1049 HeapWord *top = r->top(); 1050 1051 // Allocations move the watermark when top moves. However, compacting 1052 // objects will sometimes lower top beneath the watermark, after which, 1053 // attempts to read the watermark will assert out (watermark should not be 1054 // higher than top). 1055 if (top > tams) { 1056 // There have been allocations in this region since the start of the cycle. 1057 // Any objects new to this region must not assimilate elevated age. 1058 r->reset_age(); 1059 } else if (ShenandoahGenerationalHeap::heap()->is_aging_cycle()) { 1060 r->increment_age(); 1061 } 1062 } 1063 } 1064 1065 bool is_thread_safe() override { 1066 return true; 1067 } 1068 }; 1069 1070 void ShenandoahGenerationalHeap::final_update_refs_update_region_states() { 1071 ShenandoahSynchronizePinnedRegionStates pins; 1072 ShenandoahUpdateRegionAges ages(active_generation()->complete_marking_context()); 1073 auto cl = ShenandoahCompositeRegionClosure::of(pins, ages); 1074 parallel_heap_region_iterate(&cl); 1075 } 1076 1077 void ShenandoahGenerationalHeap::complete_degenerated_cycle() { 1078 shenandoah_assert_heaplocked_or_safepoint(); 1079 if (is_concurrent_old_mark_in_progress()) { 1080 // This is still necessary for degenerated cycles because the degeneration point may occur 1081 // after final mark of the young generation. See ShenandoahConcurrentGC::op_final_update_refs for 1082 // a more detailed explanation. 1083 old_generation()->transfer_pointers_from_satb(); 1084 } 1085 1086 // We defer generation resizing actions until after cset regions have been recycled. 1087 TransferResult result = balance_generations(); 1088 LogTarget(Info, gc, ergo) lt; 1089 if (lt.is_enabled()) { 1090 LogStream ls(lt); 1091 result.print_on("Degenerated GC", &ls); 1092 } 1093 1094 // In case degeneration interrupted concurrent evacuation or update references, we need to clean up 1095 // transient state. Otherwise, these actions have no effect. 1096 reset_generation_reserves(); 1097 1098 if (!old_generation()->is_parsable()) { 1099 ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_coalesce_and_fill); 1100 coalesce_and_fill_old_regions(false); 1101 } 1102 } 1103 1104 void ShenandoahGenerationalHeap::complete_concurrent_cycle() { 1105 if (!old_generation()->is_parsable()) { 1106 // Class unloading may render the card offsets unusable, so we must rebuild them before 1107 // the next remembered set scan. We _could_ let the control thread do this sometime after 1108 // the global cycle has completed and before the next young collection, but under memory 1109 // pressure the control thread may not have the time (that is, because it's running back 1110 // to back GCs). In that scenario, we would have to make the old regions parsable before 1111 // we could start a young collection. This could delay the start of the young cycle and 1112 // throw off the heuristics. 1113 entry_global_coalesce_and_fill(); 1114 } 1115 1116 TransferResult result; 1117 { 1118 ShenandoahHeapLocker locker(lock()); 1119 1120 result = balance_generations(); 1121 reset_generation_reserves(); 1122 } 1123 1124 LogTarget(Info, gc, ergo) lt; 1125 if (lt.is_enabled()) { 1126 LogStream ls(lt); 1127 result.print_on("Concurrent GC", &ls); 1128 } 1129 } 1130 1131 void ShenandoahGenerationalHeap::entry_global_coalesce_and_fill() { 1132 const char* msg = "Coalescing and filling old regions"; 1133 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_coalesce_and_fill); 1134 1135 TraceCollectorStats tcs(monitoring_support()->concurrent_collection_counters()); 1136 EventMark em("%s", msg); 1137 ShenandoahWorkerScope scope(workers(), 1138 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(), 1139 "concurrent coalesce and fill"); 1140 1141 coalesce_and_fill_old_regions(true); 1142 } 1143 1144 void ShenandoahGenerationalHeap::update_region_ages(ShenandoahMarkingContext* ctx) { 1145 ShenandoahUpdateRegionAges cl(ctx); 1146 parallel_heap_region_iterate(&cl); 1147 }