rev 53341 : 8212206: Refactor AdaptiveSizePolicy to separate out code related to GC overhead
Summary: Move check_gc_overhead_limit() and related code to its own class
Reviewed-by:

   1 /*
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   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.
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  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  *
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  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
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  24 
  25 #include "precompiled.hpp"
  26 #include "aot/aotLoader.hpp"
  27 #include "classfile/classLoaderDataGraph.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "classfile/symbolTable.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "gc/parallel/parallelScavengeHeap.hpp"
  33 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  34 #include "gc/parallel/psMarkSweep.hpp"
  35 #include "gc/parallel/psMarkSweepDecorator.hpp"
  36 #include "gc/parallel/psOldGen.hpp"
  37 #include "gc/parallel/psScavenge.hpp"
  38 #include "gc/parallel/psYoungGen.hpp"
  39 #include "gc/serial/markSweep.hpp"
  40 #include "gc/shared/gcCause.hpp"
  41 #include "gc/shared/gcHeapSummary.hpp"
  42 #include "gc/shared/gcId.hpp"
  43 #include "gc/shared/gcLocker.hpp"
  44 #include "gc/shared/gcTimer.hpp"
  45 #include "gc/shared/gcTrace.hpp"
  46 #include "gc/shared/gcTraceTime.inline.hpp"
  47 #include "gc/shared/isGCActiveMark.hpp"
  48 #include "gc/shared/referencePolicy.hpp"
  49 #include "gc/shared/referenceProcessor.hpp"
  50 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  51 #include "gc/shared/spaceDecorator.hpp"
  52 #include "gc/shared/weakProcessor.hpp"
  53 #include "logging/log.hpp"
  54 #include "oops/oop.inline.hpp"
  55 #include "runtime/biasedLocking.hpp"
  56 #include "runtime/flags/flagSetting.hpp"
  57 #include "runtime/handles.inline.hpp"
  58 #include "runtime/safepoint.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "services/management.hpp"
  61 #include "services/memoryService.hpp"
  62 #include "utilities/align.hpp"
  63 #include "utilities/events.hpp"
  64 #include "utilities/stack.inline.hpp"
  65 
  66 elapsedTimer        PSMarkSweep::_accumulated_time;
  67 jlong               PSMarkSweep::_time_of_last_gc   = 0;
  68 CollectorCounters*  PSMarkSweep::_counters = NULL;
  69 
  70 SpanSubjectToDiscoveryClosure PSMarkSweep::_span_based_discoverer;
  71 
  72 void PSMarkSweep::initialize() {
  73   _span_based_discoverer.set_span(ParallelScavengeHeap::heap()->reserved_region());
  74   set_ref_processor(new ReferenceProcessor(&_span_based_discoverer));     // a vanilla ref proc
  75   _counters = new CollectorCounters("PSMarkSweep", 1);
  76   MarkSweep::initialize();
  77 }
  78 
  79 // This method contains all heap specific policy for invoking mark sweep.
  80 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
  81 // the heap. It will do nothing further. If we need to bail out for policy
  82 // reasons, scavenge before full gc, or any other specialized behavior, it
  83 // needs to be added here.
  84 //
  85 // Note that this method should only be called from the vm_thread while
  86 // at a safepoint!
  87 //
  88 // Note that the all_soft_refs_clear flag in the collector policy
  89 // may be true because this method can be called without intervening
  90 // activity.  For example when the heap space is tight and full measure
  91 // are being taken to free space.
  92 
  93 void PSMarkSweep::invoke(bool maximum_heap_compaction) {
  94   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
  95   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
  96   assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
  97 
  98   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
  99   GCCause::Cause gc_cause = heap->gc_cause();
 100   PSAdaptiveSizePolicy* policy = heap->size_policy();
 101   IsGCActiveMark mark;
 102 
 103   if (ScavengeBeforeFullGC) {
 104     PSScavenge::invoke_no_policy();
 105   }
 106 
 107   const bool clear_all_soft_refs =
 108     heap->soft_ref_policy()->should_clear_all_soft_refs();
 109 
 110   uint count = maximum_heap_compaction ? 1 : MarkSweepAlwaysCompactCount;
 111   UIntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
 112   PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
 113 }
 114 
 115 // This method contains no policy. You should probably
 116 // be calling invoke() instead.
 117 bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
 118   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
 119   assert(ref_processor() != NULL, "Sanity");
 120 
 121   if (GCLocker::check_active_before_gc()) {
 122     return false;
 123   }
 124 
 125   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 126   GCCause::Cause gc_cause = heap->gc_cause();
 127 
 128   GCIdMark gc_id_mark;
 129   _gc_timer->register_gc_start();
 130   _gc_tracer->report_gc_start(gc_cause, _gc_timer->gc_start());
 131 
 132   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 133 
 134   // The scope of casr should end after code that can change
 135   // CollectorPolicy::_should_clear_all_soft_refs.
 136   ClearedAllSoftRefs casr(clear_all_softrefs, heap->soft_ref_policy());
 137 
 138   PSYoungGen* young_gen = heap->young_gen();
 139   PSOldGen* old_gen = heap->old_gen();
 140 
 141   // Increment the invocation count
 142   heap->increment_total_collections(true /* full */);
 143 
 144   // Save information needed to minimize mangling
 145   heap->record_gen_tops_before_GC();
 146 
 147   // We need to track unique mark sweep invocations as well.
 148   _total_invocations++;
 149 
 150   heap->print_heap_before_gc();
 151   heap->trace_heap_before_gc(_gc_tracer);
 152 
 153   // Fill in TLABs
 154   heap->ensure_parsability(true);  // retire TLABs
 155 
 156   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 157     HandleMark hm;  // Discard invalid handles created during verification
 158     Universe::verify("Before GC");
 159   }
 160 
 161   // Verify object start arrays
 162   if (VerifyObjectStartArray &&
 163       VerifyBeforeGC) {
 164     old_gen->verify_object_start_array();
 165   }
 166 
 167   // Filled in below to track the state of the young gen after the collection.
 168   bool eden_empty;
 169   bool survivors_empty;
 170   bool young_gen_empty;
 171 
 172   {
 173     HandleMark hm;
 174 
 175     GCTraceCPUTime tcpu;
 176     GCTraceTime(Info, gc) t("Pause Full", NULL, gc_cause, true);
 177 
 178     heap->pre_full_gc_dump(_gc_timer);
 179 
 180     TraceCollectorStats tcs(counters());
 181     TraceMemoryManagerStats tms(heap->old_gc_manager(),gc_cause);
 182 
 183     if (log_is_enabled(Debug, gc, heap, exit)) {
 184       accumulated_time()->start();
 185     }
 186 
 187     // Let the size policy know we're starting
 188     size_policy->major_collection_begin();
 189 
 190     CodeCache::gc_prologue();
 191     BiasedLocking::preserve_marks();
 192 
 193     // Capture metadata size before collection for sizing.
 194     size_t metadata_prev_used = MetaspaceUtils::used_bytes();
 195 
 196     size_t old_gen_prev_used = old_gen->used_in_bytes();
 197     size_t young_gen_prev_used = young_gen->used_in_bytes();
 198 
 199     allocate_stacks();
 200 
 201 #if COMPILER2_OR_JVMCI
 202     DerivedPointerTable::clear();
 203 #endif
 204 
 205     ref_processor()->enable_discovery();
 206     ref_processor()->setup_policy(clear_all_softrefs);
 207 
 208     mark_sweep_phase1(clear_all_softrefs);
 209 
 210     mark_sweep_phase2();
 211 
 212 #if COMPILER2_OR_JVMCI
 213     // Don't add any more derived pointers during phase3
 214     assert(DerivedPointerTable::is_active(), "Sanity");
 215     DerivedPointerTable::set_active(false);
 216 #endif
 217 
 218     mark_sweep_phase3();
 219 
 220     mark_sweep_phase4();
 221 
 222     restore_marks();
 223 
 224     deallocate_stacks();
 225 
 226     if (ZapUnusedHeapArea) {
 227       // Do a complete mangle (top to end) because the usage for
 228       // scratch does not maintain a top pointer.
 229       young_gen->to_space()->mangle_unused_area_complete();
 230     }
 231 
 232     eden_empty = young_gen->eden_space()->is_empty();
 233     if (!eden_empty) {
 234       eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
 235     }
 236 
 237     // Update heap occupancy information which is used as
 238     // input to soft ref clearing policy at the next gc.
 239     Universe::update_heap_info_at_gc();
 240 
 241     survivors_empty = young_gen->from_space()->is_empty() &&
 242                       young_gen->to_space()->is_empty();
 243     young_gen_empty = eden_empty && survivors_empty;
 244 
 245     PSCardTable* card_table = heap->card_table();
 246     MemRegion old_mr = heap->old_gen()->reserved();
 247     if (young_gen_empty) {
 248       card_table->clear(MemRegion(old_mr.start(), old_mr.end()));
 249     } else {
 250       card_table->invalidate(MemRegion(old_mr.start(), old_mr.end()));
 251     }
 252 
 253     // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 254     ClassLoaderDataGraph::purge();
 255     MetaspaceUtils::verify_metrics();
 256 
 257     BiasedLocking::restore_marks();
 258     CodeCache::gc_epilogue();
 259     JvmtiExport::gc_epilogue();
 260 
 261 #if COMPILER2_OR_JVMCI
 262     DerivedPointerTable::update_pointers();
 263 #endif
 264 
 265     assert(!ref_processor()->discovery_enabled(), "Should have been disabled earlier");
 266 
 267     // Update time of last GC
 268     reset_millis_since_last_gc();
 269 
 270     // Let the size policy know we're done
 271     size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
 272 
 273     if (UseAdaptiveSizePolicy) {
 274 
 275      log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
 276      log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
 277                          old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 278 
 279       // Don't check if the size_policy is ready here.  Let
 280       // the size_policy check that internally.
 281       if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
 282           AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
 283         // Swap the survivor spaces if from_space is empty. The
 284         // resize_young_gen() called below is normally used after
 285         // a successful young GC and swapping of survivor spaces;
 286         // otherwise, it will fail to resize the young gen with
 287         // the current implementation.
 288         if (young_gen->from_space()->is_empty()) {
 289           young_gen->from_space()->clear(SpaceDecorator::Mangle);
 290           young_gen->swap_spaces();
 291         }
 292 
 293         // Calculate optimal free space amounts
 294         assert(young_gen->max_size() >
 295           young_gen->from_space()->capacity_in_bytes() +
 296           young_gen->to_space()->capacity_in_bytes(),
 297           "Sizes of space in young gen are out of bounds");
 298 
 299         size_t young_live = young_gen->used_in_bytes();
 300         size_t eden_live = young_gen->eden_space()->used_in_bytes();
 301         size_t old_live = old_gen->used_in_bytes();
 302         size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
 303         size_t max_old_gen_size = old_gen->max_gen_size();
 304         size_t max_eden_size = young_gen->max_size() -
 305           young_gen->from_space()->capacity_in_bytes() -
 306           young_gen->to_space()->capacity_in_bytes();
 307 
 308         // Used for diagnostics
 309         size_policy->clear_generation_free_space_flags();
 310 
 311         size_policy->compute_generations_free_space(young_live,
 312                                                     eden_live,
 313                                                     old_live,
 314                                                     cur_eden,
 315                                                     max_old_gen_size,
 316                                                     max_eden_size,
 317                                                     true /* full gc*/);
 318 
 319         size_policy->check_gc_overhead_limit(eden_live,

 320                                              max_old_gen_size,
 321                                              max_eden_size,
 322                                              true /* full gc*/,
 323                                              gc_cause,
 324                                              heap->soft_ref_policy());
 325 
 326         size_policy->decay_supplemental_growth(true /* full gc*/);
 327 
 328         heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
 329 
 330         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 331                                size_policy->calculated_survivor_size_in_bytes());
 332       }
 333       log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
 334     }
 335 
 336     if (UsePerfData) {
 337       heap->gc_policy_counters()->update_counters();
 338       heap->gc_policy_counters()->update_old_capacity(
 339         old_gen->capacity_in_bytes());
 340       heap->gc_policy_counters()->update_young_capacity(
 341         young_gen->capacity_in_bytes());
 342     }
 343 
 344     heap->resize_all_tlabs();
 345 
 346     // We collected the heap, recalculate the metaspace capacity
 347     MetaspaceGC::compute_new_size();
 348 
 349     if (log_is_enabled(Debug, gc, heap, exit)) {
 350       accumulated_time()->stop();
 351     }
 352 
 353     young_gen->print_used_change(young_gen_prev_used);
 354     old_gen->print_used_change(old_gen_prev_used);
 355     MetaspaceUtils::print_metaspace_change(metadata_prev_used);
 356 
 357     // Track memory usage and detect low memory
 358     MemoryService::track_memory_usage();
 359     heap->update_counters();
 360 
 361     heap->post_full_gc_dump(_gc_timer);
 362   }
 363 
 364   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 365     HandleMark hm;  // Discard invalid handles created during verification
 366     Universe::verify("After GC");
 367   }
 368 
 369   // Re-verify object start arrays
 370   if (VerifyObjectStartArray &&
 371       VerifyAfterGC) {
 372     old_gen->verify_object_start_array();
 373   }
 374 
 375   if (ZapUnusedHeapArea) {
 376     old_gen->object_space()->check_mangled_unused_area_complete();
 377   }
 378 
 379   NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
 380 
 381   heap->print_heap_after_gc();
 382   heap->trace_heap_after_gc(_gc_tracer);
 383 
 384 #ifdef TRACESPINNING
 385   ParallelTaskTerminator::print_termination_counts();
 386 #endif
 387 
 388   AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
 389 
 390   _gc_timer->register_gc_end();
 391 
 392   _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 393 
 394   return true;
 395 }
 396 
 397 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
 398                                              PSYoungGen* young_gen,
 399                                              PSOldGen* old_gen) {
 400   MutableSpace* const eden_space = young_gen->eden_space();
 401   assert(!eden_space->is_empty(), "eden must be non-empty");
 402   assert(young_gen->virtual_space()->alignment() ==
 403          old_gen->virtual_space()->alignment(), "alignments do not match");
 404 
 405   if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
 406     return false;
 407   }
 408 
 409   // Both generations must be completely committed.
 410   if (young_gen->virtual_space()->uncommitted_size() != 0) {
 411     return false;
 412   }
 413   if (old_gen->virtual_space()->uncommitted_size() != 0) {
 414     return false;
 415   }
 416 
 417   // Figure out how much to take from eden.  Include the average amount promoted
 418   // in the total; otherwise the next young gen GC will simply bail out to a
 419   // full GC.
 420   const size_t alignment = old_gen->virtual_space()->alignment();
 421   const size_t eden_used = eden_space->used_in_bytes();
 422   const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
 423   const size_t absorb_size = align_up(eden_used + promoted, alignment);
 424   const size_t eden_capacity = eden_space->capacity_in_bytes();
 425 
 426   if (absorb_size >= eden_capacity) {
 427     return false; // Must leave some space in eden.
 428   }
 429 
 430   const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
 431   if (new_young_size < young_gen->min_gen_size()) {
 432     return false; // Respect young gen minimum size.
 433   }
 434 
 435   log_trace(gc, ergo, heap)(" absorbing " SIZE_FORMAT "K:  "
 436                             "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
 437                             "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
 438                             "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
 439                             absorb_size / K,
 440                             eden_capacity / K, (eden_capacity - absorb_size) / K,
 441                             young_gen->from_space()->used_in_bytes() / K,
 442                             young_gen->to_space()->used_in_bytes() / K,
 443                             young_gen->capacity_in_bytes() / K, new_young_size / K);
 444 
 445   // Fill the unused part of the old gen.
 446   MutableSpace* const old_space = old_gen->object_space();
 447   HeapWord* const unused_start = old_space->top();
 448   size_t const unused_words = pointer_delta(old_space->end(), unused_start);
 449 
 450   if (unused_words > 0) {
 451     if (unused_words < CollectedHeap::min_fill_size()) {
 452       return false;  // If the old gen cannot be filled, must give up.
 453     }
 454     CollectedHeap::fill_with_objects(unused_start, unused_words);
 455   }
 456 
 457   // Take the live data from eden and set both top and end in the old gen to
 458   // eden top.  (Need to set end because reset_after_change() mangles the region
 459   // from end to virtual_space->high() in debug builds).
 460   HeapWord* const new_top = eden_space->top();
 461   old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
 462                                         absorb_size);
 463   young_gen->reset_after_change();
 464   old_space->set_top(new_top);
 465   old_space->set_end(new_top);
 466   old_gen->reset_after_change();
 467 
 468   // Update the object start array for the filler object and the data from eden.
 469   ObjectStartArray* const start_array = old_gen->start_array();
 470   for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
 471     start_array->allocate_block(p);
 472   }
 473 
 474   // Could update the promoted average here, but it is not typically updated at
 475   // full GCs and the value to use is unclear.  Something like
 476   //
 477   // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
 478 
 479   size_policy->set_bytes_absorbed_from_eden(absorb_size);
 480   return true;
 481 }
 482 
 483 void PSMarkSweep::allocate_stacks() {
 484   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 485   PSYoungGen* young_gen = heap->young_gen();
 486 
 487   MutableSpace* to_space = young_gen->to_space();
 488   _preserved_marks = (PreservedMark*)to_space->top();
 489   _preserved_count = 0;
 490 
 491   // We want to calculate the size in bytes first.
 492   _preserved_count_max  = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
 493   // Now divide by the size of a PreservedMark
 494   _preserved_count_max /= sizeof(PreservedMark);
 495 }
 496 
 497 
 498 void PSMarkSweep::deallocate_stacks() {
 499   _preserved_mark_stack.clear(true);
 500   _preserved_oop_stack.clear(true);
 501   _marking_stack.clear();
 502   _objarray_stack.clear(true);
 503 }
 504 
 505 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
 506   // Recursively traverse all live objects and mark them
 507   GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
 508 
 509   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 510 
 511   // Need to clear claim bits before the tracing starts.
 512   ClassLoaderDataGraph::clear_claimed_marks();
 513 
 514   // General strong roots.
 515   {
 516     ParallelScavengeHeap::ParStrongRootsScope psrs;
 517     Universe::oops_do(mark_and_push_closure());
 518     JNIHandles::oops_do(mark_and_push_closure());   // Global (strong) JNI handles
 519     MarkingCodeBlobClosure each_active_code_blob(mark_and_push_closure(), !CodeBlobToOopClosure::FixRelocations);
 520     Threads::oops_do(mark_and_push_closure(), &each_active_code_blob);
 521     ObjectSynchronizer::oops_do(mark_and_push_closure());
 522     Management::oops_do(mark_and_push_closure());
 523     JvmtiExport::oops_do(mark_and_push_closure());
 524     SystemDictionary::oops_do(mark_and_push_closure());
 525     ClassLoaderDataGraph::always_strong_cld_do(follow_cld_closure());
 526     // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
 527     //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
 528     AOTLoader::oops_do(mark_and_push_closure());
 529   }
 530 
 531   // Flush marking stack.
 532   follow_stack();
 533 
 534   // Process reference objects found during marking
 535   {
 536     GCTraceTime(Debug, gc, phases) t("Reference Processing", _gc_timer);
 537 
 538     ref_processor()->setup_policy(clear_all_softrefs);
 539     ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
 540     const ReferenceProcessorStats& stats =
 541       ref_processor()->process_discovered_references(
 542         is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL, &pt);
 543     gc_tracer()->report_gc_reference_stats(stats);
 544     pt.print_all_references();
 545   }
 546 
 547   // This is the point where the entire marking should have completed.
 548   assert(_marking_stack.is_empty(), "Marking should have completed");
 549 
 550   {
 551     GCTraceTime(Debug, gc, phases) t("Weak Processing", _gc_timer);
 552     WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
 553   }
 554 
 555   {
 556     GCTraceTime(Debug, gc, phases) t("Class Unloading", _gc_timer);
 557 
 558     // Unload classes and purge the SystemDictionary.
 559     bool purged_class = SystemDictionary::do_unloading(_gc_timer);
 560 
 561     // Unload nmethods.
 562     CodeCache::do_unloading(is_alive_closure(), purged_class);
 563 
 564     // Prune dead klasses from subklass/sibling/implementor lists.
 565     Klass::clean_weak_klass_links(purged_class);
 566   }
 567 
 568   {
 569     GCTraceTime(Debug, gc, phases) t("Scrub String Table", _gc_timer);
 570     // Delete entries for dead interned strings.
 571     StringTable::unlink(is_alive_closure());
 572   }
 573 
 574   {
 575     GCTraceTime(Debug, gc, phases) t("Scrub Symbol Table", _gc_timer);
 576     // Clean up unreferenced symbols in symbol table.
 577     SymbolTable::unlink();
 578   }
 579 
 580   _gc_tracer->report_object_count_after_gc(is_alive_closure());
 581 }
 582 
 583 
 584 void PSMarkSweep::mark_sweep_phase2() {
 585   GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
 586 
 587   // Now all live objects are marked, compute the new object addresses.
 588 
 589   // It is not required that we traverse spaces in the same order in
 590   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 591   // tracking expects us to do so. See comment under phase4.
 592 
 593   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 594   PSOldGen* old_gen = heap->old_gen();
 595 
 596   // Begin compacting into the old gen
 597   PSMarkSweepDecorator::set_destination_decorator_tenured();
 598 
 599   // This will also compact the young gen spaces.
 600   old_gen->precompact();
 601 }
 602 
 603 void PSMarkSweep::mark_sweep_phase3() {
 604   // Adjust the pointers to reflect the new locations
 605   GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", _gc_timer);
 606 
 607   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 608   PSYoungGen* young_gen = heap->young_gen();
 609   PSOldGen* old_gen = heap->old_gen();
 610 
 611   // Need to clear claim bits before the tracing starts.
 612   ClassLoaderDataGraph::clear_claimed_marks();
 613 
 614   // General strong roots.
 615   Universe::oops_do(adjust_pointer_closure());
 616   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
 617   Threads::oops_do(adjust_pointer_closure(), NULL);
 618   ObjectSynchronizer::oops_do(adjust_pointer_closure());
 619   Management::oops_do(adjust_pointer_closure());
 620   JvmtiExport::oops_do(adjust_pointer_closure());
 621   SystemDictionary::oops_do(adjust_pointer_closure());
 622   ClassLoaderDataGraph::cld_do(adjust_cld_closure());
 623 
 624   // Now adjust pointers in remaining weak roots.  (All of which should
 625   // have been cleared if they pointed to non-surviving objects.)
 626   // Global (weak) JNI handles
 627   WeakProcessor::oops_do(adjust_pointer_closure());
 628 
 629   CodeBlobToOopClosure adjust_from_blobs(adjust_pointer_closure(), CodeBlobToOopClosure::FixRelocations);
 630   CodeCache::blobs_do(&adjust_from_blobs);
 631   AOTLoader::oops_do(adjust_pointer_closure());
 632   StringTable::oops_do(adjust_pointer_closure());
 633   ref_processor()->weak_oops_do(adjust_pointer_closure());
 634   PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
 635 
 636   adjust_marks();
 637 
 638   young_gen->adjust_pointers();
 639   old_gen->adjust_pointers();
 640 }
 641 
 642 void PSMarkSweep::mark_sweep_phase4() {
 643   EventMark m("4 compact heap");
 644   GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
 645 
 646   // All pointers are now adjusted, move objects accordingly
 647 
 648   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 649   PSYoungGen* young_gen = heap->young_gen();
 650   PSOldGen* old_gen = heap->old_gen();
 651 
 652   old_gen->compact();
 653   young_gen->compact();
 654 }
 655 
 656 jlong PSMarkSweep::millis_since_last_gc() {
 657   // We need a monotonically non-decreasing time in ms but
 658   // os::javaTimeMillis() does not guarantee monotonicity.
 659   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 660   jlong ret_val = now - _time_of_last_gc;
 661   // XXX See note in genCollectedHeap::millis_since_last_gc().
 662   if (ret_val < 0) {
 663     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
 664     return 0;
 665   }
 666   return ret_val;
 667 }
 668 
 669 void PSMarkSweep::reset_millis_since_last_gc() {
 670   // We need a monotonically non-decreasing time in ms but
 671   // os::javaTimeMillis() does not guarantee monotonicity.
 672   _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 673 }
--- EOF ---