1 /*
   2  * Copyright (c) 2001, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/serial/cardTableRS.hpp"
  27 #include "gc/serial/defNewGeneration.inline.hpp"
  28 #include "gc/serial/serialGcRefProcProxyTask.hpp"
  29 #include "gc/serial/serialHeap.inline.hpp"
  30 #include "gc/serial/serialStringDedup.inline.hpp"
  31 #include "gc/serial/tenuredGeneration.hpp"
  32 #include "gc/shared/adaptiveSizePolicy.hpp"
  33 #include "gc/shared/ageTable.inline.hpp"
  34 #include "gc/shared/collectorCounters.hpp"
  35 #include "gc/shared/continuationGCSupport.inline.hpp"
  36 #include "gc/shared/gcArguments.hpp"
  37 #include "gc/shared/gcHeapSummary.hpp"
  38 #include "gc/shared/gcLocker.hpp"
  39 #include "gc/shared/gcPolicyCounters.hpp"
  40 #include "gc/shared/gcTimer.hpp"
  41 #include "gc/shared/gcTrace.hpp"
  42 #include "gc/shared/gcTraceTime.inline.hpp"
  43 #include "gc/shared/generationSpec.hpp"
  44 #include "gc/shared/preservedMarks.inline.hpp"
  45 #include "gc/shared/referencePolicy.hpp"
  46 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  47 #include "gc/shared/space.inline.hpp"
  48 #include "gc/shared/spaceDecorator.inline.hpp"
  49 #include "gc/shared/strongRootsScope.hpp"
  50 #include "gc/shared/weakProcessor.hpp"
  51 #include "logging/log.hpp"
  52 #include "memory/iterator.inline.hpp"
  53 #include "memory/resourceArea.hpp"
  54 #include "oops/instanceRefKlass.hpp"
  55 #include "oops/oop.inline.hpp"
  56 #include "runtime/java.hpp"
  57 #include "runtime/javaThread.hpp"
  58 #include "runtime/prefetch.inline.hpp"
  59 #include "runtime/threads.hpp"
  60 #include "utilities/align.hpp"
  61 #include "utilities/copy.hpp"
  62 #include "utilities/globalDefinitions.hpp"
  63 #include "utilities/stack.inline.hpp"
  64 
  65 class ScavengeHelper {
  66   DefNewGeneration* _young_gen;
  67   HeapWord*         _young_gen_end;
  68 public:
  69   ScavengeHelper(DefNewGeneration* young_gen) :
  70     _young_gen(young_gen),
  71     _young_gen_end(young_gen->reserved().end()) {}
  72 
  73   bool is_in_young_gen(void* p) const {
  74     return p < _young_gen_end;
  75   }
  76 
  77   template <typename T, typename Func>
  78   void try_scavenge(T* p, Func&& f) {
  79     T heap_oop = RawAccess<>::oop_load(p);
  80     // Should we copy the obj?
  81     if (!CompressedOops::is_null(heap_oop)) {
  82       oop obj = CompressedOops::decode_not_null(heap_oop);
  83       if (is_in_young_gen(obj)) {
  84         assert(!_young_gen->to()->is_in_reserved(obj), "Scanning field twice?");
  85         oop new_obj = obj->is_forwarded() ? obj->forwardee()
  86                                           : _young_gen->copy_to_survivor_space(obj);
  87         RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
  88 
  89         // callback
  90         f(new_obj);
  91       }
  92     }
  93   }
  94 };
  95 
  96 class InHeapScanClosure : public BasicOopIterateClosure {
  97   ScavengeHelper _helper;
  98 protected:
  99   bool is_in_young_gen(void* p) const {
 100     return _helper.is_in_young_gen(p);
 101   }
 102 
 103   template <typename T, typename Func>
 104   void try_scavenge(T* p, Func&& f) {
 105     _helper.try_scavenge(p, f);
 106   }
 107 
 108   InHeapScanClosure(DefNewGeneration* young_gen) :
 109     BasicOopIterateClosure(young_gen->ref_processor()),
 110     _helper(young_gen) {}
 111 };
 112 
 113 class OffHeapScanClosure : public OopClosure {
 114   ScavengeHelper _helper;
 115 protected:
 116   bool is_in_young_gen(void* p) const {
 117     return _helper.is_in_young_gen(p);
 118   }
 119 
 120   template <typename T, typename Func>
 121   void try_scavenge(T* p, Func&& f) {
 122     _helper.try_scavenge(p, f);
 123   }
 124 
 125   OffHeapScanClosure(DefNewGeneration* young_gen) :  _helper(young_gen) {}
 126 };
 127 
 128 class OldGenScanClosure : public InHeapScanClosure {
 129   CardTableRS* _rs;
 130 
 131   template <typename T>
 132   void do_oop_work(T* p) {
 133     assert(!is_in_young_gen(p), "precondition");
 134 
 135     try_scavenge(p, [&] (oop new_obj) {
 136       // If p points to a younger generation, mark the card.
 137       if (is_in_young_gen(new_obj)) {
 138         _rs->inline_write_ref_field_gc(p);
 139       }
 140     });
 141   }
 142 public:
 143   OldGenScanClosure(DefNewGeneration* g) : InHeapScanClosure(g),
 144     _rs(SerialHeap::heap()->rem_set()) {}
 145 
 146   void do_oop(oop* p)       { do_oop_work(p); }
 147   void do_oop(narrowOop* p) { do_oop_work(p); }
 148 };
 149 
 150 class PromoteFailureClosure : public InHeapScanClosure {
 151   template <typename T>
 152   void do_oop_work(T* p) {
 153     assert(is_in_young_gen(p), "promote-fail objs must be in young-gen");
 154     assert(!SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "must not be in to-space");
 155 
 156     try_scavenge(p, [] (auto) {});
 157   }
 158 public:
 159   PromoteFailureClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
 160 
 161   void do_oop(oop* p)       { do_oop_work(p); }
 162   void do_oop(narrowOop* p) { do_oop_work(p); }
 163 };
 164 
 165 class YoungGenScanClosure : public InHeapScanClosure {
 166   template <typename T>
 167   void do_oop_work(T* p) {
 168     assert(SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "precondition");
 169 
 170     try_scavenge(p, [] (auto) {});
 171   }
 172 public:
 173   YoungGenScanClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
 174 
 175   void do_oop(oop* p)       { do_oop_work(p); }
 176   void do_oop(narrowOop* p) { do_oop_work(p); }
 177 };
 178 
 179 class RootScanClosure : public OffHeapScanClosure {
 180   template <typename T>
 181   void do_oop_work(T* p) {
 182     assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
 183 
 184     try_scavenge(p,  [] (auto) {});
 185   }
 186 public:
 187   RootScanClosure(DefNewGeneration* g) : OffHeapScanClosure(g) {}
 188 
 189   void do_oop(oop* p)       { do_oop_work(p); }
 190   void do_oop(narrowOop* p) { do_oop_work(p); }
 191 };
 192 
 193 class CLDScanClosure: public CLDClosure {
 194 
 195   class CLDOopClosure : public OffHeapScanClosure {
 196     ClassLoaderData* _scanned_cld;
 197 
 198     template <typename T>
 199     void do_oop_work(T* p) {
 200       assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
 201 
 202       try_scavenge(p, [&] (oop new_obj) {
 203         assert(_scanned_cld != nullptr, "inv");
 204         if (is_in_young_gen(new_obj) && !_scanned_cld->has_modified_oops()) {
 205           _scanned_cld->record_modified_oops();
 206         }
 207       });
 208     }
 209 
 210   public:
 211     CLDOopClosure(DefNewGeneration* g) : OffHeapScanClosure(g),
 212       _scanned_cld(nullptr) {}
 213 
 214     void set_scanned_cld(ClassLoaderData* cld) {
 215       assert(cld == nullptr || _scanned_cld == nullptr, "Must be");
 216       _scanned_cld = cld;
 217     }
 218 
 219     void do_oop(oop* p)       { do_oop_work(p); }
 220     void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 221   };
 222 
 223   CLDOopClosure _oop_closure;
 224  public:
 225   CLDScanClosure(DefNewGeneration* g) : _oop_closure(g) {}
 226 
 227   void do_cld(ClassLoaderData* cld) {
 228     // If the cld has not been dirtied we know that there's
 229     // no references into  the young gen and we can skip it.
 230     if (cld->has_modified_oops()) {
 231 
 232       // Tell the closure which CLD is being scanned so that it can be dirtied
 233       // if oops are left pointing into the young gen.
 234       _oop_closure.set_scanned_cld(cld);
 235 
 236       // Clean the cld since we're going to scavenge all the metadata.
 237       cld->oops_do(&_oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
 238 
 239       _oop_closure.set_scanned_cld(nullptr);
 240     }
 241   }
 242 };
 243 
 244 class IsAliveClosure: public BoolObjectClosure {
 245   HeapWord*         _young_gen_end;
 246 public:
 247   IsAliveClosure(DefNewGeneration* g): _young_gen_end(g->reserved().end()) {}
 248 
 249   bool do_object_b(oop p) {
 250     return cast_from_oop<HeapWord*>(p) >= _young_gen_end || p->is_forwarded();
 251   }
 252 };
 253 
 254 class AdjustWeakRootClosure: public OffHeapScanClosure {
 255   template <class T>
 256   void do_oop_work(T* p) {
 257     DEBUG_ONLY(SerialHeap* heap = SerialHeap::heap();)
 258     assert(!heap->is_in_reserved(p), "outside the heap");
 259 
 260     oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
 261     if (is_in_young_gen(obj)) {
 262       assert(!heap->young_gen()->to()->is_in_reserved(obj), "inv");
 263       assert(obj->is_forwarded(), "forwarded before weak-root-processing");
 264       oop new_obj = obj->forwardee();
 265       RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
 266     }
 267   }
 268  public:
 269   AdjustWeakRootClosure(DefNewGeneration* g): OffHeapScanClosure(g) {}
 270 
 271   void do_oop(oop* p)       { do_oop_work(p); }
 272   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 273 };
 274 
 275 class KeepAliveClosure: public OopClosure {
 276   DefNewGeneration* _young_gen;
 277   HeapWord*         _young_gen_end;
 278   CardTableRS* _rs;
 279 
 280   bool is_in_young_gen(void* p) const {
 281     return p < _young_gen_end;
 282   }
 283 
 284   template <class T>
 285   void do_oop_work(T* p) {
 286     oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
 287 
 288     if (is_in_young_gen(obj)) {
 289       oop new_obj = obj->is_forwarded() ? obj->forwardee()
 290                                         : _young_gen->copy_to_survivor_space(obj);
 291       RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
 292 
 293       if (is_in_young_gen(new_obj) && !is_in_young_gen(p)) {
 294         _rs->inline_write_ref_field_gc(p);
 295       }
 296     }
 297   }
 298 public:
 299   KeepAliveClosure(DefNewGeneration* g) :
 300     _young_gen(g),
 301     _young_gen_end(g->reserved().end()),
 302     _rs(SerialHeap::heap()->rem_set()) {}
 303 
 304   void do_oop(oop* p)       { do_oop_work(p); }
 305   void do_oop(narrowOop* p) { do_oop_work(p); }
 306 };
 307 
 308 class FastEvacuateFollowersClosure: public VoidClosure {
 309   SerialHeap* _heap;
 310   YoungGenScanClosure* _young_cl;
 311   OldGenScanClosure* _old_cl;
 312 public:
 313   FastEvacuateFollowersClosure(SerialHeap* heap,
 314                                YoungGenScanClosure* young_cl,
 315                                OldGenScanClosure* old_cl) :
 316     _heap(heap), _young_cl(young_cl), _old_cl(old_cl)
 317   {}
 318 
 319   void do_void() {
 320     do {
 321       _heap->oop_since_save_marks_iterate(_young_cl, _old_cl);
 322     } while (!_heap->no_allocs_since_save_marks());
 323     guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
 324   }
 325 };
 326 
 327 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 328                                    size_t initial_size,
 329                                    size_t min_size,
 330                                    size_t max_size,
 331                                    const char* policy)
 332   : Generation(rs, initial_size),
 333     _preserved_marks_set(false /* in_c_heap */),
 334     _promo_failure_drain_in_progress(false),
 335     _should_allocate_from_space(false),
 336     _string_dedup_requests()
 337 {
 338   MemRegion cmr((HeapWord*)_virtual_space.low(),
 339                 (HeapWord*)_virtual_space.high());
 340   GenCollectedHeap* gch = GenCollectedHeap::heap();
 341 
 342   gch->rem_set()->resize_covered_region(cmr);
 343 
 344   _eden_space = new ContiguousSpace();
 345   _from_space = new ContiguousSpace();
 346   _to_space   = new ContiguousSpace();
 347 
 348   // Compute the maximum eden and survivor space sizes. These sizes
 349   // are computed assuming the entire reserved space is committed.
 350   // These values are exported as performance counters.
 351   uintx size = _virtual_space.reserved_size();
 352   _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
 353   _max_eden_size = size - (2*_max_survivor_size);
 354 
 355   // allocate the performance counters
 356 
 357   // Generation counters -- generation 0, 3 subspaces
 358   _gen_counters = new GenerationCounters("new", 0, 3,
 359       min_size, max_size, &_virtual_space);
 360   _gc_counters = new CollectorCounters(policy, 0);
 361 
 362   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 363                                       _gen_counters);
 364   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 365                                       _gen_counters);
 366   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 367                                     _gen_counters);
 368 
 369   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 370   update_counters();
 371   _old_gen = nullptr;
 372   _tenuring_threshold = MaxTenuringThreshold;
 373   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 374 
 375   _ref_processor = nullptr;
 376 
 377   _gc_timer = new STWGCTimer();
 378 
 379   _gc_tracer = new DefNewTracer();
 380 }
 381 
 382 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 383                                                 bool clear_space,
 384                                                 bool mangle_space) {
 385   // If the spaces are being cleared (only done at heap initialization
 386   // currently), the survivor spaces need not be empty.
 387   // Otherwise, no care is taken for used areas in the survivor spaces
 388   // so check.
 389   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 390     "Initialization of the survivor spaces assumes these are empty");
 391 
 392   // Compute sizes
 393   uintx size = _virtual_space.committed_size();
 394   uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
 395   uintx eden_size = size - (2*survivor_size);
 396   if (eden_size > max_eden_size()) {
 397     // Need to reduce eden_size to satisfy the max constraint. The delta needs
 398     // to be 2*SpaceAlignment aligned so that both survivors are properly
 399     // aligned.
 400     uintx eden_delta = align_up(eden_size - max_eden_size(), 2*SpaceAlignment);
 401     eden_size     -= eden_delta;
 402     survivor_size += eden_delta/2;
 403   }
 404   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 405 
 406   if (eden_size < minimum_eden_size) {
 407     // May happen due to 64Kb rounding, if so adjust eden size back up
 408     minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
 409     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 410     uintx unaligned_survivor_size =
 411       align_down(maximum_survivor_size, SpaceAlignment);
 412     survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
 413     eden_size = size - (2*survivor_size);
 414     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 415     assert(eden_size >= minimum_eden_size, "just checking");
 416   }
 417 
 418   char *eden_start = _virtual_space.low();
 419   char *from_start = eden_start + eden_size;
 420   char *to_start   = from_start + survivor_size;
 421   char *to_end     = to_start   + survivor_size;
 422 
 423   assert(to_end == _virtual_space.high(), "just checking");
 424   assert(Space::is_aligned(eden_start), "checking alignment");
 425   assert(Space::is_aligned(from_start), "checking alignment");
 426   assert(Space::is_aligned(to_start),   "checking alignment");
 427 
 428   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 429   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 430   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 431 
 432   // A minimum eden size implies that there is a part of eden that
 433   // is being used and that affects the initialization of any
 434   // newly formed eden.
 435   bool live_in_eden = minimum_eden_size > 0;
 436 
 437   // If not clearing the spaces, do some checking to verify that
 438   // the space are already mangled.
 439   if (!clear_space) {
 440     // Must check mangling before the spaces are reshaped.  Otherwise,
 441     // the bottom or end of one space may have moved into another
 442     // a failure of the check may not correctly indicate which space
 443     // is not properly mangled.
 444     if (ZapUnusedHeapArea) {
 445       HeapWord* limit = (HeapWord*) _virtual_space.high();
 446       eden()->check_mangled_unused_area(limit);
 447       from()->check_mangled_unused_area(limit);
 448         to()->check_mangled_unused_area(limit);
 449     }
 450   }
 451 
 452   // Reset the spaces for their new regions.
 453   eden()->initialize(edenMR,
 454                      clear_space && !live_in_eden,
 455                      SpaceDecorator::Mangle);
 456   // If clear_space and live_in_eden, we will not have cleared any
 457   // portion of eden above its top. This can cause newly
 458   // expanded space not to be mangled if using ZapUnusedHeapArea.
 459   // We explicitly do such mangling here.
 460   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 461     eden()->mangle_unused_area();
 462   }
 463   from()->initialize(fromMR, clear_space, mangle_space);
 464   to()->initialize(toMR, clear_space, mangle_space);
 465 
 466   // Set next compaction spaces.
 467   eden()->set_next_compaction_space(from());
 468   // The to-space is normally empty before a compaction so need
 469   // not be considered.  The exception is during promotion
 470   // failure handling when to-space can contain live objects.
 471   from()->set_next_compaction_space(nullptr);
 472 }
 473 
 474 void DefNewGeneration::swap_spaces() {
 475   ContiguousSpace* s = from();
 476   _from_space        = to();
 477   _to_space          = s;
 478   eden()->set_next_compaction_space(from());
 479   // The to-space is normally empty before a compaction so need
 480   // not be considered.  The exception is during promotion
 481   // failure handling when to-space can contain live objects.
 482   from()->set_next_compaction_space(nullptr);
 483 
 484   if (UsePerfData) {
 485     CSpaceCounters* c = _from_counters;
 486     _from_counters = _to_counters;
 487     _to_counters = c;
 488   }
 489 }
 490 
 491 bool DefNewGeneration::expand(size_t bytes) {
 492   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 493   bool success = _virtual_space.expand_by(bytes);
 494   if (success && ZapUnusedHeapArea) {
 495     // Mangle newly committed space immediately because it
 496     // can be done here more simply that after the new
 497     // spaces have been computed.
 498     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 499     MemRegion mangle_region(prev_high, new_high);
 500     SpaceMangler::mangle_region(mangle_region);
 501   }
 502 
 503   // Do not attempt an expand-to-the reserve size.  The
 504   // request should properly observe the maximum size of
 505   // the generation so an expand-to-reserve should be
 506   // unnecessary.  Also a second call to expand-to-reserve
 507   // value potentially can cause an undue expansion.
 508   // For example if the first expand fail for unknown reasons,
 509   // but the second succeeds and expands the heap to its maximum
 510   // value.
 511   if (GCLocker::is_active()) {
 512     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 513   }
 514 
 515   return success;
 516 }
 517 
 518 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
 519     size_t thread_increase_size = 0;
 520     // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 521     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 522       thread_increase_size = threads_count * NewSizeThreadIncrease;
 523     }
 524     return thread_increase_size;
 525 }
 526 
 527 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 528                                                     size_t new_size_before,
 529                                                     size_t alignment,
 530                                                     size_t thread_increase_size) const {
 531   size_t desired_new_size = new_size_before;
 532 
 533   if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
 534 
 535     // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
 536     if (new_size_candidate <= max_uintx - thread_increase_size) {
 537       new_size_candidate += thread_increase_size;
 538 
 539       // 2. Check an overflow at 'align_up'.
 540       size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 541       if (new_size_candidate <= aligned_max) {
 542         desired_new_size = align_up(new_size_candidate, alignment);
 543       }
 544     }
 545   }
 546 
 547   return desired_new_size;
 548 }
 549 
 550 void DefNewGeneration::compute_new_size() {
 551   // This is called after a GC that includes the old generation, so from-space
 552   // will normally be empty.
 553   // Note that we check both spaces, since if scavenge failed they revert roles.
 554   // If not we bail out (otherwise we would have to relocate the objects).
 555   if (!from()->is_empty() || !to()->is_empty()) {
 556     return;
 557   }
 558 
 559   GenCollectedHeap* gch = GenCollectedHeap::heap();
 560 
 561   size_t old_size = gch->old_gen()->capacity();
 562   size_t new_size_before = _virtual_space.committed_size();
 563   size_t min_new_size = initial_size();
 564   size_t max_new_size = reserved().byte_size();
 565   assert(min_new_size <= new_size_before &&
 566          new_size_before <= max_new_size,
 567          "just checking");
 568   // All space sizes must be multiples of Generation::GenGrain.
 569   size_t alignment = Generation::GenGrain;
 570 
 571   int threads_count = Threads::number_of_non_daemon_threads();
 572   size_t thread_increase_size = calculate_thread_increase_size(threads_count);
 573 
 574   size_t new_size_candidate = old_size / NewRatio;
 575   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 576   // and reverts to previous value if any overflow happens
 577   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
 578                                                        alignment, thread_increase_size);
 579 
 580   // Adjust new generation size
 581   desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
 582   assert(desired_new_size <= max_new_size, "just checking");
 583 
 584   bool changed = false;
 585   if (desired_new_size > new_size_before) {
 586     size_t change = desired_new_size - new_size_before;
 587     assert(change % alignment == 0, "just checking");
 588     if (expand(change)) {
 589        changed = true;
 590     }
 591     // If the heap failed to expand to the desired size,
 592     // "changed" will be false.  If the expansion failed
 593     // (and at this point it was expected to succeed),
 594     // ignore the failure (leaving "changed" as false).
 595   }
 596   if (desired_new_size < new_size_before && eden()->is_empty()) {
 597     // bail out of shrinking if objects in eden
 598     size_t change = new_size_before - desired_new_size;
 599     assert(change % alignment == 0, "just checking");
 600     _virtual_space.shrink_by(change);
 601     changed = true;
 602   }
 603   if (changed) {
 604     // The spaces have already been mangled at this point but
 605     // may not have been cleared (set top = bottom) and should be.
 606     // Mangling was done when the heap was being expanded.
 607     compute_space_boundaries(eden()->used(),
 608                              SpaceDecorator::Clear,
 609                              SpaceDecorator::DontMangle);
 610     MemRegion cmr((HeapWord*)_virtual_space.low(),
 611                   (HeapWord*)_virtual_space.high());
 612     gch->rem_set()->resize_covered_region(cmr);
 613 
 614     log_debug(gc, ergo, heap)(
 615         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 616         new_size_before/K, _virtual_space.committed_size()/K,
 617         eden()->capacity()/K, from()->capacity()/K);
 618     log_trace(gc, ergo, heap)(
 619         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 620           thread_increase_size/K, threads_count);
 621       }
 622 }
 623 
 624 void DefNewGeneration::ref_processor_init() {
 625   assert(_ref_processor == nullptr, "a reference processor already exists");
 626   assert(!_reserved.is_empty(), "empty generation?");
 627   _span_based_discoverer.set_span(_reserved);
 628   _ref_processor = new ReferenceProcessor(&_span_based_discoverer);    // a vanilla reference processor
 629 }
 630 
 631 size_t DefNewGeneration::capacity() const {
 632   return eden()->capacity()
 633        + from()->capacity();  // to() is only used during scavenge
 634 }
 635 
 636 
 637 size_t DefNewGeneration::used() const {
 638   return eden()->used()
 639        + from()->used();      // to() is only used during scavenge
 640 }
 641 
 642 
 643 size_t DefNewGeneration::free() const {
 644   return eden()->free()
 645        + from()->free();      // to() is only used during scavenge
 646 }
 647 
 648 size_t DefNewGeneration::max_capacity() const {
 649   const size_t reserved_bytes = reserved().byte_size();
 650   return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
 651 }
 652 
 653 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 654   return eden()->free();
 655 }
 656 
 657 size_t DefNewGeneration::capacity_before_gc() const {
 658   return eden()->capacity();
 659 }
 660 
 661 size_t DefNewGeneration::contiguous_available() const {
 662   return eden()->free();
 663 }
 664 
 665 
 666 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 667   eden()->object_iterate(blk);
 668   from()->object_iterate(blk);
 669 }
 670 
 671 
 672 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 673                                      bool usedOnly) {
 674   blk->do_space(eden());
 675   blk->do_space(from());
 676   blk->do_space(to());
 677 }
 678 
 679 // The last collection bailed out, we are running out of heap space,
 680 // so we try to allocate the from-space, too.
 681 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 682   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 683 
 684   // If the Heap_lock is not locked by this thread, this will be called
 685   // again later with the Heap_lock held.
 686   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 687 
 688   HeapWord* result = nullptr;
 689   if (do_alloc) {
 690     result = from()->allocate(size);
 691   }
 692 
 693   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 694                         size,
 695                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 696                           "true" : "false",
 697                         Heap_lock->is_locked() ? "locked" : "unlocked",
 698                         from()->free(),
 699                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 700                         do_alloc ? "  Heap_lock is not owned by self" : "",
 701                         result == nullptr ? "null" : "object");
 702 
 703   return result;
 704 }
 705 
 706 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
 707   // We don't attempt to expand the young generation (but perhaps we should.)
 708   return allocate(size, is_tlab);
 709 }
 710 
 711 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 712   // Set the desired survivor size to half the real survivor space
 713   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 714   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 715 
 716   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 717 
 718   if (UsePerfData) {
 719     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 720     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 721     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 722   }
 723 
 724   age_table()->print_age_table(_tenuring_threshold);
 725 }
 726 
 727 void DefNewGeneration::collect(bool   full,
 728                                bool   clear_all_soft_refs,
 729                                size_t size,
 730                                bool   is_tlab) {
 731   assert(full || size > 0, "otherwise we don't want to collect");
 732 
 733   SerialHeap* heap = SerialHeap::heap();
 734 
 735   // If the next generation is too full to accommodate promotion
 736   // from this generation, pass on collection; let the next generation
 737   // do it.
 738   if (!collection_attempt_is_safe()) {
 739     log_trace(gc)(":: Collection attempt not safe ::");
 740     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 741     return;
 742   }
 743   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 744   _gc_timer->register_gc_start();
 745   _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
 746   _ref_processor->start_discovery(clear_all_soft_refs);
 747 
 748   _old_gen = heap->old_gen();
 749 
 750   init_assuming_no_promotion_failure();
 751 
 752   GCTraceTime(Trace, gc, phases) tm("DefNew", nullptr, heap->gc_cause());
 753 
 754   heap->trace_heap_before_gc(_gc_tracer);
 755 
 756   // These can be shared for all code paths
 757   IsAliveClosure is_alive(this);
 758 
 759   age_table()->clear();
 760   to()->clear(SpaceDecorator::Mangle);
 761   // The preserved marks should be empty at the start of the GC.
 762   _preserved_marks_set.init(1);
 763 
 764   assert(heap->no_allocs_since_save_marks(),
 765          "save marks have not been newly set.");
 766 
 767   YoungGenScanClosure young_gen_cl(this);
 768   OldGenScanClosure   old_gen_cl(this);
 769 
 770   FastEvacuateFollowersClosure evacuate_followers(heap,
 771                                                   &young_gen_cl,
 772                                                   &old_gen_cl);
 773 
 774   assert(heap->no_allocs_since_save_marks(),
 775          "save marks have not been newly set.");
 776 
 777   {
 778     StrongRootsScope srs(0);
 779     RootScanClosure root_cl{this};
 780     CLDScanClosure cld_scan_closure{this};
 781 
 782     heap->young_process_roots(&root_cl,
 783                               &old_gen_cl,
 784                               &cld_scan_closure);
 785   }
 786 
 787   // "evacuate followers".
 788   evacuate_followers.do_void();
 789 
 790   {
 791     // Reference processing
 792     KeepAliveClosure keep_alive(this);
 793     ReferenceProcessor* rp = ref_processor();
 794     ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
 795     SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
 796     const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
 797     _gc_tracer->report_gc_reference_stats(stats);
 798     _gc_tracer->report_tenuring_threshold(tenuring_threshold());
 799     pt.print_all_references();
 800   }
 801   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 802 
 803   {
 804     AdjustWeakRootClosure cl{this};
 805     WeakProcessor::weak_oops_do(&is_alive, &cl);
 806   }
 807 
 808   // Verify that the usage of keep_alive didn't copy any objects.
 809   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 810 
 811   _string_dedup_requests.flush();
 812 
 813   if (!_promotion_failed) {
 814     // Swap the survivor spaces.
 815     eden()->clear(SpaceDecorator::Mangle);
 816     from()->clear(SpaceDecorator::Mangle);
 817     if (ZapUnusedHeapArea) {
 818       // This is now done here because of the piece-meal mangling which
 819       // can check for valid mangling at intermediate points in the
 820       // collection(s).  When a young collection fails to collect
 821       // sufficient space resizing of the young generation can occur
 822       // an redistribute the spaces in the young generation.  Mangle
 823       // here so that unzapped regions don't get distributed to
 824       // other spaces.
 825       to()->mangle_unused_area();
 826     }
 827     swap_spaces();
 828 
 829     assert(to()->is_empty(), "to space should be empty now");
 830 
 831     adjust_desired_tenuring_threshold();
 832 
 833     // A successful scavenge should restart the GC time limit count which is
 834     // for full GC's.
 835     AdaptiveSizePolicy* size_policy = heap->size_policy();
 836     size_policy->reset_gc_overhead_limit_count();
 837     assert(!heap->incremental_collection_failed(), "Should be clear");
 838   } else {
 839     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 840     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 841 
 842     remove_forwarding_pointers();
 843     log_info(gc, promotion)("Promotion failed");
 844     // Add to-space to the list of space to compact
 845     // when a promotion failure has occurred.  In that
 846     // case there can be live objects in to-space
 847     // as a result of a partial evacuation of eden
 848     // and from-space.
 849     swap_spaces();   // For uniformity wrt ParNewGeneration.
 850     from()->set_next_compaction_space(to());
 851     heap->set_incremental_collection_failed();
 852 
 853     // Inform the next generation that a promotion failure occurred.
 854     _old_gen->promotion_failure_occurred();
 855     _gc_tracer->report_promotion_failed(_promotion_failed_info);
 856 
 857     // Reset the PromotionFailureALot counters.
 858     NOT_PRODUCT(heap->reset_promotion_should_fail();)
 859   }
 860   // We should have processed and cleared all the preserved marks.
 861   _preserved_marks_set.reclaim();
 862 
 863   heap->trace_heap_after_gc(_gc_tracer);
 864 
 865   _gc_timer->register_gc_end();
 866 
 867   _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 868 }
 869 
 870 void DefNewGeneration::init_assuming_no_promotion_failure() {
 871   _promotion_failed = false;
 872   _promotion_failed_info.reset();
 873   from()->set_next_compaction_space(nullptr);
 874 }
 875 
 876 void DefNewGeneration::remove_forwarding_pointers() {
 877   assert(_promotion_failed, "precondition");
 878 
 879   // Will enter Full GC soon due to failed promotion. Must reset the mark word
 880   // of objs in young-gen so that no objs are marked (forwarded) when Full GC
 881   // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
 882   struct ResetForwardedMarkWord : ObjectClosure {
 883     void do_object(oop obj) override {
 884       if (obj->is_forwarded()) {
 885         obj->forward_safe_init_mark();
 886       }
 887     }
 888   } cl;
 889   eden()->object_iterate(&cl);
 890   from()->object_iterate(&cl);
 891 
 892   restore_preserved_marks();
 893 }
 894 
 895 void DefNewGeneration::restore_preserved_marks() {
 896   _preserved_marks_set.restore(nullptr);
 897 }
 898 
 899 void DefNewGeneration::handle_promotion_failure(oop old) {
 900   log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
 901 
 902   _promotion_failed = true;
 903   _promotion_failed_info.register_copy_failure(old->size());
 904   _preserved_marks_set.get()->push_if_necessary(old, old->mark());
 905 
 906   ContinuationGCSupport::transform_stack_chunk(old);
 907 
 908   old->forward_to_self();

 909 
 910   _promo_failure_scan_stack.push(old);
 911 
 912   if (!_promo_failure_drain_in_progress) {
 913     // prevent recursion in copy_to_survivor_space()
 914     _promo_failure_drain_in_progress = true;
 915     drain_promo_failure_scan_stack();
 916     _promo_failure_drain_in_progress = false;
 917   }
 918 }
 919 
 920 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 921   assert(is_in_reserved(old) && !old->is_forwarded(),
 922          "shouldn't be scavenging this oop");
 923   size_t s = old->size();
 924   oop obj = nullptr;
 925 
 926   // Try allocating obj in to-space (unless too old)
 927   if (old->age() < tenuring_threshold()) {
 928     obj = cast_to_oop(to()->allocate(s));
 929   }
 930 
 931   bool new_obj_is_tenured = false;
 932   // Otherwise try allocating obj tenured
 933   if (obj == nullptr) {
 934     obj = _old_gen->promote(old, s);
 935     if (obj == nullptr) {
 936       handle_promotion_failure(old);
 937       return old;
 938     }
 939     new_obj_is_tenured = true;
 940   } else {
 941     // Prefetch beyond obj
 942     const intx interval = PrefetchCopyIntervalInBytes;
 943     Prefetch::write(obj, interval);
 944 
 945     // Copy obj
 946     Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
 947 
 948     ContinuationGCSupport::transform_stack_chunk(obj);
 949 
 950     // Increment age if obj still in new generation
 951     obj->incr_age();
 952     age_table()->add(obj, s);
 953   }
 954 
 955   // Done, insert forward pointer to obj in this header
 956   old->forward_to(obj);
 957 
 958   if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
 959     // Record old; request adds a new weak reference, which reference
 960     // processing expects to refer to a from-space object.
 961     _string_dedup_requests.add(old);
 962   }
 963   return obj;
 964 }
 965 
 966 void DefNewGeneration::drain_promo_failure_scan_stack() {
 967   PromoteFailureClosure cl{this};
 968   while (!_promo_failure_scan_stack.is_empty()) {
 969      oop obj = _promo_failure_scan_stack.pop();
 970      obj->oop_iterate(&cl);
 971   }
 972 }
 973 
 974 void DefNewGeneration::save_marks() {
 975   eden()->set_saved_mark();
 976   to()->set_saved_mark();
 977   from()->set_saved_mark();
 978 }
 979 
 980 
 981 bool DefNewGeneration::no_allocs_since_save_marks() {
 982   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 983   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 984   return to()->saved_mark_at_top();
 985 }
 986 
 987 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 988                                          size_t max_alloc_words) {
 989   if (requestor == this || _promotion_failed) {
 990     return;
 991   }
 992   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 993 
 994   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 995   if (to_space->top() > to_space->bottom()) {
 996     trace("to_space not empty when contribute_scratch called");
 997   }
 998   */
 999 
1000   ContiguousSpace* to_space = to();
1001   assert(to_space->end() >= to_space->top(), "pointers out of order");
1002   size_t free_words = pointer_delta(to_space->end(), to_space->top());
1003   if (free_words >= MinFreeScratchWords) {
1004     ScratchBlock* sb = (ScratchBlock*)to_space->top();
1005     sb->num_words = free_words;
1006     sb->next = list;
1007     list = sb;
1008   }
1009 }
1010 
1011 void DefNewGeneration::reset_scratch() {
1012   // If contributing scratch in to_space, mangle all of
1013   // to_space if ZapUnusedHeapArea.  This is needed because
1014   // top is not maintained while using to-space as scratch.
1015   if (ZapUnusedHeapArea) {
1016     to()->mangle_unused_area_complete();
1017   }
1018 }
1019 
1020 bool DefNewGeneration::collection_attempt_is_safe() {
1021   if (!to()->is_empty()) {
1022     log_trace(gc)(":: to is not empty ::");
1023     return false;
1024   }
1025   if (_old_gen == nullptr) {
1026     GenCollectedHeap* gch = GenCollectedHeap::heap();
1027     _old_gen = gch->old_gen();
1028   }
1029   return _old_gen->promotion_attempt_is_safe(used());
1030 }
1031 
1032 void DefNewGeneration::gc_epilogue(bool full) {
1033   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
1034 
1035   assert(!GCLocker::is_active(), "We should not be executing here");
1036   // Check if the heap is approaching full after a collection has
1037   // been done.  Generally the young generation is empty at
1038   // a minimum at the end of a collection.  If it is not, then
1039   // the heap is approaching full.
1040   GenCollectedHeap* gch = GenCollectedHeap::heap();
1041   if (full) {
1042     DEBUG_ONLY(seen_incremental_collection_failed = false;)
1043     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
1044       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
1045                             GCCause::to_string(gch->gc_cause()));
1046       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
1047       set_should_allocate_from_space(); // we seem to be running out of space
1048     } else {
1049       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
1050                             GCCause::to_string(gch->gc_cause()));
1051       gch->clear_incremental_collection_failed(); // We just did a full collection
1052       clear_should_allocate_from_space(); // if set
1053     }
1054   } else {
1055 #ifdef ASSERT
1056     // It is possible that incremental_collection_failed() == true
1057     // here, because an attempted scavenge did not succeed. The policy
1058     // is normally expected to cause a full collection which should
1059     // clear that condition, so we should not be here twice in a row
1060     // with incremental_collection_failed() == true without having done
1061     // a full collection in between.
1062     if (!seen_incremental_collection_failed &&
1063         gch->incremental_collection_failed()) {
1064       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
1065                             GCCause::to_string(gch->gc_cause()));
1066       seen_incremental_collection_failed = true;
1067     } else if (seen_incremental_collection_failed) {
1068       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
1069                             GCCause::to_string(gch->gc_cause()));
1070       seen_incremental_collection_failed = false;
1071     }
1072 #endif // ASSERT
1073   }
1074 
1075   if (ZapUnusedHeapArea) {
1076     eden()->check_mangled_unused_area_complete();
1077     from()->check_mangled_unused_area_complete();
1078     to()->check_mangled_unused_area_complete();
1079   }
1080 
1081   // update the generation and space performance counters
1082   update_counters();
1083   gch->counters()->update_counters();
1084 }
1085 
1086 void DefNewGeneration::record_spaces_top() {
1087   assert(ZapUnusedHeapArea, "Not mangling unused space");
1088   eden()->set_top_for_allocations();
1089   to()->set_top_for_allocations();
1090   from()->set_top_for_allocations();
1091 }
1092 
1093 void DefNewGeneration::update_counters() {
1094   if (UsePerfData) {
1095     _eden_counters->update_all();
1096     _from_counters->update_all();
1097     _to_counters->update_all();
1098     _gen_counters->update_all();
1099   }
1100 }
1101 
1102 void DefNewGeneration::verify() {
1103   eden()->verify();
1104   from()->verify();
1105     to()->verify();
1106 }
1107 
1108 void DefNewGeneration::print_on(outputStream* st) const {
1109   Generation::print_on(st);
1110   st->print("  eden");
1111   eden()->print_on(st);
1112   st->print("  from");
1113   from()->print_on(st);
1114   st->print("  to  ");
1115   to()->print_on(st);
1116 }
1117 
1118 
1119 const char* DefNewGeneration::name() const {
1120   return "def new generation";
1121 }
1122 
1123 // Moved from inline file as they are not called inline
1124 ContiguousSpace* DefNewGeneration::first_compaction_space() const {
1125   return eden();
1126 }
1127 
1128 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1129   // This is the slow-path allocation for the DefNewGeneration.
1130   // Most allocations are fast-path in compiled code.
1131   // We try to allocate from the eden.  If that works, we are happy.
1132   // Note that since DefNewGeneration supports lock-free allocation, we
1133   // have to use it here, as well.
1134   HeapWord* result = eden()->par_allocate(word_size);
1135   if (result == nullptr) {
1136     // If the eden is full and the last collection bailed out, we are running
1137     // out of heap space, and we try to allocate the from-space, too.
1138     // allocate_from_space can't be inlined because that would introduce a
1139     // circular dependency at compile time.
1140     result = allocate_from_space(word_size);
1141   }
1142   return result;
1143 }
1144 
1145 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1146                                          bool is_tlab) {
1147   return eden()->par_allocate(word_size);
1148 }
1149 
1150 size_t DefNewGeneration::tlab_capacity() const {
1151   return eden()->capacity();
1152 }
1153 
1154 size_t DefNewGeneration::tlab_used() const {
1155   return eden()->used();
1156 }
1157 
1158 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1159   return unsafe_max_alloc_nogc();
1160 }
--- EOF ---