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::set_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::set_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());
 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()->report_gc_reference_stats(stats);
 153 
 154 
 155   // This is the point where the entire marking should have completed.
 156   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 157 
 158   // Unload classes and purge the SystemDictionary.
 159   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
 160 
 161   // Unload nmethods.
 162   CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
 163 
 164   // Prune dead klasses from subklass/sibling/implementor lists.
 165   Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
 166 
 167   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 168   g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 169 
 170   if (VerifyDuringGC) {
 171     HandleMark hm;  // handle scope
 172 #if defined(COMPILER2) || INCLUDE_JVMCI
 173     DerivedPointerTableDeactivate dpt_deact;
 174 #endif
 175     g1h->prepare_for_verify();
 176     // Note: we can verify only the heap here. When an object is
 177     // marked, the previous value of the mark word (including
 178     // identity hash values, ages, etc) is preserved, and the mark
 179     // word is set to markOop::marked_value - effectively removing
 180     // any hash values from the mark word. These hash values are
 181     // used when verifying the dictionaries and so removing them
 182     // from the mark word can make verification of the dictionaries
 183     // fail. At the end of the GC, the original mark word values
 184     // (including hash values) are restored to the appropriate
 185     // objects.
 186     if (!VerifySilently) {
 187       gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
 188     }
 189     g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);
 190     if (!VerifySilently) {
 191       gclog_or_tty->print_cr("]");
 192     }
 193   }
 194 
 195   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 196 }
 197 
 198 
 199 void G1MarkSweep::mark_sweep_phase2() {
 200   // Now all live objects are marked, compute the new object addresses.
 201 
 202   // It is not required that we traverse spaces in the same order in
 203   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 204   // tracking expects us to do so. See comment under phase4.
 205 
 206   GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
 207 
 208   prepare_compaction();
 209 }
 210 
 211 class G1AdjustPointersClosure: public HeapRegionClosure {
 212  public:
 213   bool doHeapRegion(HeapRegion* r) {
 214     if (r->is_humongous()) {
 215       if (r->is_starts_humongous()) {
 216         // We must adjust the pointers on the single H object.
 217         oop obj = oop(r->bottom());
 218         // point all the oops to the new location
 219         MarkSweep::adjust_pointers(obj);
 220       }
 221     } else if (!r->is_pinned()) {
 222       // This really ought to be "as_CompactibleSpace"...
 223       r->adjust_pointers();
 224     }
 225     return false;
 226   }
 227 };
 228 
 229 class G1AlwaysTrueClosure: public BoolObjectClosure {
 230 public:
 231   bool do_object_b(oop p) { return true; }
 232 };
 233 static G1AlwaysTrueClosure always_true;
 234 
 235 void G1MarkSweep::mark_sweep_phase3() {
 236   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 237 
 238   // Adjust the pointers to reflect the new locations
 239   GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
 240 
 241   // Need cleared claim bits for the roots processing
 242   ClassLoaderDataGraph::clear_claimed_marks();
 243 
 244   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 245   {
 246     G1RootProcessor root_processor(g1h, 1);
 247     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 248                                      &GenMarkSweep::adjust_cld_closure,
 249                                      &adjust_code_closure);
 250   }
 251 
 252   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 253   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 254 
 255   // Now adjust pointers in remaining weak roots.  (All of which should
 256   // have been cleared if they pointed to non-surviving objects.)
 257   JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
 258 
 259   if (G1StringDedup::is_enabled()) {
 260     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 261   }
 262 
 263   GenMarkSweep::adjust_marks();
 264 
 265   G1AdjustPointersClosure blk;
 266   g1h->heap_region_iterate(&blk);
 267 }
 268 
 269 class G1SpaceCompactClosure: public HeapRegionClosure {
 270 public:
 271   G1SpaceCompactClosure() {}
 272 
 273   bool doHeapRegion(HeapRegion* hr) {
 274     if (hr->is_humongous()) {
 275       if (hr->is_starts_humongous()) {
 276         oop obj = oop(hr->bottom());
 277         if (obj->is_gc_marked()) {
 278           obj->init_mark();
 279         } else {
 280           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 281         }
 282       }
 283       hr->reset_during_compaction();
 284     } else if (!hr->is_pinned()) {
 285       hr->compact();
 286     }
 287     return false;
 288   }
 289 };
 290 
 291 void G1MarkSweep::mark_sweep_phase4() {
 292   // All pointers are now adjusted, move objects accordingly
 293 
 294   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 295   // in the same order in phase2, phase3 and phase4. We don't quite do that
 296   // here (code and comment not fixed for perm removal), so we tell the validate code
 297   // to use a higher index (saved from phase2) when verifying perm_gen.
 298   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 299 
 300   GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
 301 
 302   G1SpaceCompactClosure blk;
 303   g1h->heap_region_iterate(&blk);
 304 
 305 }
 306 
 307 void G1MarkSweep::enable_archive_object_check() {
 308   assert(!_archive_check_enabled, "archive range check already enabled");
 309   _archive_check_enabled = true;
 310   size_t length = Universe::heap()->max_capacity();
 311   _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
 312                                  (HeapWord*)Universe::heap()->base() + length,
 313                                  HeapRegion::GrainBytes);
 314 }
 315 
 316 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
 317   assert(_archive_check_enabled, "archive range check not enabled");
 318   _archive_region_map.set_by_address(range, is_archive);
 319 }
 320 
 321 bool G1MarkSweep::in_archive_range(oop object) {
 322   // This is the out-of-line part of is_archive_object test, done separately
 323   // to avoid additional performance impact when the check is not enabled.
 324   return _archive_region_map.get_by_address((HeapWord*)object);
 325 }
 326 
 327 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 328   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 329   g1h->heap_region_iterate(blk);
 330   blk->update_sets();
 331 }
 332 
 333 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 334   HeapWord* end = hr->end();
 335   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 336 
 337   hr->set_containing_set(NULL);
 338   _humongous_regions_removed.increment(1u, hr->capacity());
 339 
 340   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
 341   prepare_for_compaction(hr, end);
 342   dummy_free_list.remove_all();
 343 }
 344 
 345 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 346   // If this is the first live region that we came across which we can compact,
 347   // initialize the CompactPoint.
 348   if (!is_cp_initialized()) {
 349     _cp.space = hr;
 350     _cp.threshold = hr->initialize_threshold();
 351   }
 352   prepare_for_compaction_work(&_cp, hr, end);
 353 }
 354 
 355 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 356                                                           HeapRegion* hr,
 357                                                           HeapWord* end) {
 358   hr->prepare_for_compaction(cp);
 359   // Also clear the part of the card table that will be unused after
 360   // compaction.
 361   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 362 }
 363 
 364 void G1PrepareCompactClosure::update_sets() {
 365   // We'll recalculate total used bytes and recreate the free list
 366   // at the end of the GC, so no point in updating those values here.
 367   HeapRegionSetCount empty_set;
 368   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
 369 }
 370 
 371 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 372   if (hr->is_humongous()) {
 373     oop obj = oop(hr->humongous_start_region()->bottom());
 374     if (hr->is_starts_humongous() && obj->is_gc_marked()) {
 375       obj->forward_to(obj);
 376     }
 377     if (!obj->is_gc_marked()) {
 378       free_humongous_region(hr);
 379     }
 380   } else if (!hr->is_pinned()) {
 381     prepare_for_compaction(hr, hr->end());
 382   }
 383   return false;
 384 }
--- EOF ---