1 /*
   2  * Copyright (c) 2001, 2015, 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 "classfile/javaClasses.hpp"
  27 #include "classfile/symbolTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "code/icBuffer.hpp"
  32 #include "gc/g1/g1Log.hpp"
  33 #include "gc/g1/g1MarkSweep.hpp"
  34 #include "gc/g1/g1RootProcessor.hpp"
  35 #include "gc/g1/g1StringDedup.hpp"
  36 #include "gc/serial/markSweep.inline.hpp"
  37 #include "gc/shared/gcHeapSummary.hpp"
  38 #include "gc/shared/gcLocker.hpp"
  39 #include "gc/shared/gcTimer.hpp"
  40 #include "gc/shared/gcTrace.hpp"
  41 #include "gc/shared/gcTraceTime.hpp"
  42 #include "gc/shared/genCollectedHeap.hpp"
  43 #include "gc/shared/modRefBarrierSet.hpp"
  44 #include "gc/shared/referencePolicy.hpp"
  45 #include "gc/shared/space.hpp"
  46 #include "oops/instanceRefKlass.hpp"
  47 #include "oops/oop.inline.hpp"
  48 #include "prims/jvmtiExport.hpp"
  49 #include "runtime/atomic.inline.hpp"
  50 #include "runtime/biasedLocking.hpp"
  51 #include "runtime/fprofiler.hpp"
  52 #include "runtime/synchronizer.hpp"
  53 #include "runtime/thread.hpp"
  54 #include "runtime/vmThread.hpp"
  55 #include "utilities/copy.hpp"
  56 #include "utilities/events.hpp"
  57 
  58 class HeapRegion;
  59 
  60 bool G1MarkSweep::_archive_check_enabled = false;
  61 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
  62 
  63 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
  64                                       bool clear_all_softrefs) {
  65   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  66 
  67 #ifdef ASSERT
  68   if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
  69     assert(clear_all_softrefs, "Policy should have been checked earler");
  70   }
  71 #endif
  72   // hook up weak ref data so it can be used during Mark-Sweep
  73   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
  74   assert(rp != NULL, "should be non-NULL");
  75   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
  76 
  77   GenMarkSweep::_ref_processor = rp;
  78   rp->setup_policy(clear_all_softrefs);
  79 
  80   // When collecting the permanent generation Method*s may be moving,
  81   // so we either have to flush all bcp data or convert it into bci.
  82   CodeCache::gc_prologue();
  83 
  84   bool marked_for_unloading = false;
  85 
  86   allocate_stacks();
  87 
  88   // We should save the marks of the currently locked biased monitors.
  89   // The marking doesn't preserve the marks of biased objects.
  90   BiasedLocking::preserve_marks();
  91 
  92   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
  93 
  94   mark_sweep_phase2();
  95 
  96 #if defined(COMPILER2) || INCLUDE_JVMCI
  97   // Don't add any more derived pointers during phase3
  98   DerivedPointerTable::set_active(false);
  99 #endif
 100 
 101   mark_sweep_phase3();
 102 
 103   mark_sweep_phase4();
 104 
 105   GenMarkSweep::restore_marks();
 106   BiasedLocking::restore_marks();
 107   GenMarkSweep::deallocate_stacks();
 108 
 109   CodeCache::gc_epilogue();
 110   JvmtiExport::gc_epilogue();
 111 
 112   // refs processing: clean slate
 113   GenMarkSweep::_ref_processor = NULL;
 114 }
 115 
 116 
 117 void G1MarkSweep::allocate_stacks() {
 118   GenMarkSweep::_preserved_count_max = 0;
 119   GenMarkSweep::_preserved_marks = NULL;
 120   GenMarkSweep::_preserved_count = 0;
 121 }
 122 
 123 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
 124                                     bool clear_all_softrefs) {
 125   // Recursively traverse all live objects and mark them
 126   GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 127 
 128   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 129 
 130   // Need cleared claim bits for the roots processing
 131   ClassLoaderDataGraph::clear_claimed_marks();
 132 
 133   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
 134   {
 135     G1RootProcessor root_processor(g1h, 1);
 136     root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
 137                                         &GenMarkSweep::follow_cld_closure,
 138                                         &follow_code_closure);
 139   }
 140 
 141   // Process reference objects found during marking
 142   ReferenceProcessor* rp = GenMarkSweep::ref_processor();
 143   assert(rp == g1h->ref_processor_stw(), "Sanity");
 144 
 145   rp->setup_policy(clear_all_softrefs);
 146   const ReferenceProcessorStats& stats =
 147     rp->process_discovered_references(&GenMarkSweep::is_alive,
 148                                       &GenMarkSweep::keep_alive,
 149                                       &GenMarkSweep::follow_stack_closure,
 150                                       NULL,
 151                                       gc_timer(),
 152                                       gc_tracer()->gc_id());
 153   gc_tracer()->report_gc_reference_stats(stats);
 154 
 155 
 156   // This is the point where the entire marking should have completed.
 157   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 158 
 159   // Unload classes and purge the SystemDictionary.
 160   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
 161 
 162   // Unload nmethods.
 163   CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
 164 
 165   // Prune dead klasses from subklass/sibling/implementor lists.
 166   Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
 167 
 168   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 169   g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 170 
 171   if (VerifyDuringGC) {
 172     HandleMark hm;  // handle scope
 173 #if defined(COMPILER2) || INCLUDE_JVMCI
 174     DerivedPointerTableDeactivate dpt_deact;
 175 #endif
 176     g1h->prepare_for_verify();
 177     // Note: we can verify only the heap here. When an object is
 178     // marked, the previous value of the mark word (including
 179     // identity hash values, ages, etc) is preserved, and the mark
 180     // word is set to markOop::marked_value - effectively removing
 181     // any hash values from the mark word. These hash values are
 182     // used when verifying the dictionaries and so removing them
 183     // from the mark word can make verification of the dictionaries
 184     // fail. At the end of the GC, the original mark word values
 185     // (including hash values) are restored to the appropriate
 186     // objects.
 187     if (!VerifySilently) {
 188       gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
 189     }
 190     g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);
 191     if (!VerifySilently) {
 192       gclog_or_tty->print_cr("]");
 193     }
 194   }
 195 
 196   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 197 }
 198 
 199 
 200 void G1MarkSweep::mark_sweep_phase2() {
 201   // Now all live objects are marked, compute the new object addresses.
 202 
 203   // It is not required that we traverse spaces in the same order in
 204   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 205   // tracking expects us to do so. See comment under phase4.
 206 
 207   GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 208 
 209   prepare_compaction();
 210 }
 211 
 212 class G1AdjustPointersClosure: public HeapRegionClosure {
 213  public:
 214   bool doHeapRegion(HeapRegion* r) {
 215     if (r->is_humongous()) {
 216       if (r->is_starts_humongous()) {
 217         // We must adjust the pointers on the single H object.
 218         oop obj = oop(r->bottom());
 219         // point all the oops to the new location
 220         MarkSweep::adjust_pointers(obj);
 221       }
 222     } else if (!r->is_pinned()) {
 223       // This really ought to be "as_CompactibleSpace"...
 224       r->adjust_pointers();
 225     }
 226     return false;
 227   }
 228 };
 229 
 230 class G1AlwaysTrueClosure: public BoolObjectClosure {
 231 public:
 232   bool do_object_b(oop p) { return true; }
 233 };
 234 static G1AlwaysTrueClosure always_true;
 235 
 236 void G1MarkSweep::mark_sweep_phase3() {
 237   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 238 
 239   // Adjust the pointers to reflect the new locations
 240   GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 241 
 242   // Need cleared claim bits for the roots processing
 243   ClassLoaderDataGraph::clear_claimed_marks();
 244 
 245   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 246   {
 247     G1RootProcessor root_processor(g1h, 1);
 248     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 249                                      &GenMarkSweep::adjust_cld_closure,
 250                                      &adjust_code_closure);
 251   }
 252 
 253   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 254   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 255 
 256   // Now adjust pointers in remaining weak roots.  (All of which should
 257   // have been cleared if they pointed to non-surviving objects.)
 258   JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
 259 
 260   if (G1StringDedup::is_enabled()) {
 261     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 262   }
 263 
 264   GenMarkSweep::adjust_marks();
 265 
 266   G1AdjustPointersClosure blk;
 267   g1h->heap_region_iterate(&blk);
 268 }
 269 
 270 class G1SpaceCompactClosure: public HeapRegionClosure {
 271 public:
 272   G1SpaceCompactClosure() {}
 273 
 274   bool doHeapRegion(HeapRegion* hr) {
 275     if (hr->is_humongous()) {
 276       if (hr->is_starts_humongous()) {
 277         oop obj = oop(hr->bottom());
 278         if (obj->is_gc_marked()) {
 279           obj->init_mark();
 280         } else {
 281           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 282         }
 283         hr->reset_during_compaction();
 284       }
 285     } else if (!hr->is_pinned()) {
 286       hr->compact();
 287     }
 288     return false;
 289   }
 290 };
 291 
 292 void G1MarkSweep::mark_sweep_phase4() {
 293   // All pointers are now adjusted, move objects accordingly
 294 
 295   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 296   // in the same order in phase2, phase3 and phase4. We don't quite do that
 297   // here (code and comment not fixed for perm removal), so we tell the validate code
 298   // to use a higher index (saved from phase2) when verifying perm_gen.
 299   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 300 
 301   GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 302 
 303   G1SpaceCompactClosure blk;
 304   g1h->heap_region_iterate(&blk);
 305 
 306 }
 307 
 308 void G1MarkSweep::enable_archive_object_check() {
 309   assert(!_archive_check_enabled, "archive range check already enabled");
 310   _archive_check_enabled = true;
 311   size_t length = Universe::heap()->max_capacity();
 312   _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
 313                                  (HeapWord*)Universe::heap()->base() + length,
 314                                  HeapRegion::GrainBytes);
 315 }
 316 
 317 void G1MarkSweep::mark_range_archive(MemRegion range) {
 318   assert(_archive_check_enabled, "archive range check not enabled");
 319   _archive_region_map.set_by_address(range, true);
 320 }
 321 
 322 bool G1MarkSweep::in_archive_range(oop object) {
 323   // This is the out-of-line part of is_archive_object test, done separately
 324   // to avoid additional performance impact when the check is not enabled.
 325   return _archive_region_map.get_by_address((HeapWord*)object);
 326 }
 327 
 328 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 329   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 330   g1h->heap_region_iterate(blk);
 331   blk->update_sets();
 332 }
 333 
 334 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 335   HeapWord* end = hr->end();
 336   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 337 
 338   assert(hr->is_starts_humongous(),
 339          "Only the start of a humongous region should be freed.");
 340 
 341   hr->set_containing_set(NULL);
 342   _humongous_regions_removed.increment(1u, hr->capacity());
 343 
 344   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
 345   prepare_for_compaction(hr, end);
 346   dummy_free_list.remove_all();
 347 }
 348 
 349 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 350   // If this is the first live region that we came across which we can compact,
 351   // initialize the CompactPoint.
 352   if (!is_cp_initialized()) {
 353     _cp.space = hr;
 354     _cp.threshold = hr->initialize_threshold();
 355   }
 356   prepare_for_compaction_work(&_cp, hr, end);
 357 }
 358 
 359 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 360                                                           HeapRegion* hr,
 361                                                           HeapWord* end) {
 362   hr->prepare_for_compaction(cp);
 363   // Also clear the part of the card table that will be unused after
 364   // compaction.
 365   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 366 }
 367 
 368 void G1PrepareCompactClosure::update_sets() {
 369   // We'll recalculate total used bytes and recreate the free list
 370   // at the end of the GC, so no point in updating those values here.
 371   HeapRegionSetCount empty_set;
 372   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
 373 }
 374 
 375 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 376   if (hr->is_humongous()) {
 377     if (hr->is_starts_humongous()) {
 378       oop obj = oop(hr->bottom());
 379       if (obj->is_gc_marked()) {
 380         obj->forward_to(obj);
 381       } else  {
 382         free_humongous_region(hr);
 383       }
 384     } else {
 385       assert(hr->is_continues_humongous(), "Invalid humongous.");
 386     }
 387   } else if (!hr->is_pinned()) {
 388     prepare_for_compaction(hr, hr->end());
 389   }
 390   return false;
 391 }