1 /*
   2  * Copyright (c) 2001, 2016, 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/g1MarkSweep.hpp"
  33 #include "gc/g1/g1RootProcessor.hpp"
  34 #include "gc/g1/g1StringDedup.hpp"
  35 #include "gc/serial/markSweep.inline.hpp"
  36 #include "gc/shared/gcHeapSummary.hpp"
  37 #include "gc/shared/gcLocker.hpp"
  38 #include "gc/shared/gcTimer.hpp"
  39 #include "gc/shared/gcTrace.hpp"
  40 #include "gc/shared/gcTraceTime.inline.hpp"
  41 #include "gc/shared/genCollectedHeap.hpp"
  42 #include "gc/shared/modRefBarrierSet.hpp"
  43 #include "gc/shared/referencePolicy.hpp"
  44 #include "gc/shared/space.hpp"
  45 #include "oops/instanceRefKlass.hpp"
  46 #include "oops/oop.inline.hpp"
  47 #include "prims/jvmtiExport.hpp"
  48 #include "runtime/atomic.hpp"
  49 #include "runtime/biasedLocking.hpp"
  50 #include "runtime/fprofiler.hpp"
  51 #include "runtime/synchronizer.hpp"
  52 #include "runtime/thread.hpp"
  53 #include "runtime/vmThread.hpp"
  54 #include "utilities/copy.hpp"
  55 #include "utilities/events.hpp"
  56 
  57 class HeapRegion;
  58 
  59 bool G1MarkSweep::_archive_check_enabled = false;
  60 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
  61 
  62 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
  63                                       bool clear_all_softrefs) {
  64   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  65 
  66 #ifdef ASSERT
  67   if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
  68     assert(clear_all_softrefs, "Policy should have been checked earler");
  69   }
  70 #endif
  71   // hook up weak ref data so it can be used during Mark-Sweep
  72   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
  73   assert(rp != NULL, "should be non-NULL");
  74   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
  75 
  76   GenMarkSweep::set_ref_processor(rp);
  77   rp->setup_policy(clear_all_softrefs);
  78 
  79   // When collecting the permanent generation Method*s may be moving,
  80   // so we either have to flush all bcp data or convert it into bci.
  81   CodeCache::gc_prologue();
  82 
  83   bool marked_for_unloading = false;
  84 
  85   allocate_stacks();
  86 
  87   // We should save the marks of the currently locked biased monitors.
  88   // The marking doesn't preserve the marks of biased objects.
  89   BiasedLocking::preserve_marks();
  90 
  91   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
  92 
  93   mark_sweep_phase2();
  94 
  95 #if defined(COMPILER2) || INCLUDE_JVMCI
  96   // Don't add any more derived pointers during phase3
  97   DerivedPointerTable::set_active(false);
  98 #endif
  99 
 100   mark_sweep_phase3();
 101 
 102   mark_sweep_phase4();
 103 
 104   GenMarkSweep::restore_marks();
 105   BiasedLocking::restore_marks();
 106   GenMarkSweep::deallocate_stacks();
 107 
 108   CodeCache::gc_epilogue();
 109   JvmtiExport::gc_epilogue();
 110 
 111   // refs processing: clean slate
 112   GenMarkSweep::set_ref_processor(NULL);
 113 }
 114 
 115 
 116 void G1MarkSweep::allocate_stacks() {
 117   GenMarkSweep::_preserved_count_max = 0;
 118   GenMarkSweep::_preserved_marks = NULL;
 119   GenMarkSweep::_preserved_count = 0;
 120 }
 121 
 122 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
 123                                     bool clear_all_softrefs) {
 124   // Recursively traverse all live objects and mark them
 125   GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
 126 
 127   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 128 
 129   // Need cleared claim bits for the roots processing
 130   ClassLoaderDataGraph::clear_claimed_marks();
 131 
 132   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
 133   {
 134     G1RootProcessor root_processor(g1h, 1);
 135     if (ClassUnloading) {
 136       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
 137                                           &GenMarkSweep::follow_cld_closure,
 138                                           &follow_code_closure);
 139     } else {
 140       root_processor.process_all_roots_no_string_table(
 141                                           &GenMarkSweep::follow_root_closure,
 142                                           &GenMarkSweep::follow_cld_closure,
 143                                           &follow_code_closure);
 144     }
 145   }
 146 
 147   {
 148     GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
 149 
 150     // Process reference objects found during marking
 151     ReferenceProcessor* rp = GenMarkSweep::ref_processor();
 152     assert(rp == g1h->ref_processor_stw(), "Sanity");
 153 
 154     rp->setup_policy(clear_all_softrefs);
 155     const ReferenceProcessorStats& stats =
 156         rp->process_discovered_references(&GenMarkSweep::is_alive,
 157                                           &GenMarkSweep::keep_alive,
 158                                           &GenMarkSweep::follow_stack_closure,
 159                                           NULL,
 160                                           gc_timer());
 161     gc_tracer()->report_gc_reference_stats(stats);
 162   }
 163 
 164   // This is the point where the entire marking should have completed.
 165   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 166 
 167   if (ClassUnloading) {
 168     GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
 169 
 170     // Unload classes and purge the SystemDictionary.
 171     bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
 172 
 173     // Unload nmethods.
 174     CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
 175 
 176     // Prune dead klasses from subklass/sibling/implementor lists.
 177     Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
 178   }
 179 
 180   {
 181     GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
 182     // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 183     g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 184   }
 185 
 186   if (G1StringDedup::is_enabled()) {
 187     GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
 188     G1StringDedup::unlink(&GenMarkSweep::is_alive);
 189   }
 190 
 191   if (VerifyDuringGC) {
 192     HandleMark hm;  // handle scope
 193 #if defined(COMPILER2) || INCLUDE_JVMCI
 194     DerivedPointerTableDeactivate dpt_deact;
 195 #endif
 196     g1h->prepare_for_verify();
 197     // Note: we can verify only the heap here. When an object is
 198     // marked, the previous value of the mark word (including
 199     // identity hash values, ages, etc) is preserved, and the mark
 200     // word is set to markOop::marked_value - effectively removing
 201     // any hash values from the mark word. These hash values are
 202     // used when verifying the dictionaries and so removing them
 203     // from the mark word can make verification of the dictionaries
 204     // fail. At the end of the GC, the original mark word values
 205     // (including hash values) are restored to the appropriate
 206     // objects.
 207     GCTraceTime(Info, gc, verify)("During GC (full)");
 208     g1h->verify(VerifyOption_G1UseMarkWord);
 209   }
 210 
 211   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 212 }
 213 
 214 
 215 void G1MarkSweep::mark_sweep_phase2() {
 216   // Now all live objects are marked, compute the new object addresses.
 217 
 218   // It is not required that we traverse spaces in the same order in
 219   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 220   // tracking expects us to do so. See comment under phase4.
 221 
 222   GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
 223 
 224   prepare_compaction();
 225 }
 226 
 227 class G1AdjustPointersClosure: public HeapRegionClosure {
 228  public:
 229   bool doHeapRegion(HeapRegion* r) {
 230     if (r->is_humongous()) {
 231       if (r->is_starts_humongous()) {
 232         // We must adjust the pointers on the single H object.
 233         oop obj = oop(r->bottom());
 234         // point all the oops to the new location
 235         MarkSweep::adjust_pointers(obj);
 236       }
 237     } else if (!r->is_pinned()) {
 238       // This really ought to be "as_CompactibleSpace"...
 239       r->adjust_pointers();
 240     }
 241     return false;
 242   }
 243 };
 244 
 245 void G1MarkSweep::mark_sweep_phase3() {
 246   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 247 
 248   // Adjust the pointers to reflect the new locations
 249   GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
 250 
 251   // Need cleared claim bits for the roots processing
 252   ClassLoaderDataGraph::clear_claimed_marks();
 253 
 254   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 255   {
 256     G1RootProcessor root_processor(g1h, 1);
 257     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 258                                      &GenMarkSweep::adjust_cld_closure,
 259                                      &adjust_code_closure);
 260   }
 261 
 262   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 263   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 264 
 265   // Now adjust pointers in remaining weak roots.  (All of which should
 266   // have been cleared if they pointed to non-surviving objects.)
 267   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 268 
 269   if (G1StringDedup::is_enabled()) {
 270     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 271   }
 272 
 273   GenMarkSweep::adjust_marks();
 274 
 275   G1AdjustPointersClosure blk;
 276   g1h->heap_region_iterate(&blk);
 277 }
 278 
 279 class G1SpaceCompactClosure: public HeapRegionClosure {
 280 public:
 281   G1SpaceCompactClosure() {}
 282 
 283   bool doHeapRegion(HeapRegion* hr) {
 284     if (hr->is_humongous()) {
 285       if (hr->is_starts_humongous()) {
 286         oop obj = oop(hr->bottom());
 287         if (obj->is_gc_marked()) {
 288           obj->init_mark();
 289         } else {
 290           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 291         }
 292       }
 293       hr->reset_during_compaction();
 294     } else if (!hr->is_pinned()) {
 295       hr->compact();
 296     }
 297     return false;
 298   }
 299 };
 300 
 301 void G1MarkSweep::mark_sweep_phase4() {
 302   // All pointers are now adjusted, move objects accordingly
 303 
 304   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 305   // in the same order in phase2, phase3 and phase4. We don't quite do that
 306   // here (code and comment not fixed for perm removal), so we tell the validate code
 307   // to use a higher index (saved from phase2) when verifying perm_gen.
 308   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 309 
 310   GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
 311 
 312   G1SpaceCompactClosure blk;
 313   g1h->heap_region_iterate(&blk);
 314 
 315 }
 316 
 317 void G1MarkSweep::enable_archive_object_check() {
 318   assert(!_archive_check_enabled, "archive range check already enabled");
 319   _archive_check_enabled = true;
 320   size_t length = Universe::heap()->max_capacity();
 321   _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
 322                                  (HeapWord*)Universe::heap()->base() + length,
 323                                  HeapRegion::GrainBytes);
 324 }
 325 
 326 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
 327   assert(_archive_check_enabled, "archive range check not enabled");
 328   _archive_region_map.set_by_address(range, is_archive);
 329 }
 330 
 331 bool G1MarkSweep::in_archive_range(oop object) {
 332   // This is the out-of-line part of is_archive_object test, done separately
 333   // to avoid additional performance impact when the check is not enabled.
 334   return _archive_region_map.get_by_address((HeapWord*)object);
 335 }
 336 
 337 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 338   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 339   g1h->heap_region_iterate(blk);
 340   blk->update_sets();
 341 }
 342 
 343 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 344   HeapWord* end = hr->end();
 345   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 346 
 347   hr->set_containing_set(NULL);
 348   _humongous_regions_removed++;
 349 
 350   _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
 351   prepare_for_compaction(hr, end);
 352   dummy_free_list.remove_all();
 353 }
 354 
 355 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 356   // If this is the first live region that we came across which we can compact,
 357   // initialize the CompactPoint.
 358   if (!is_cp_initialized()) {
 359     _cp.space = hr;
 360     _cp.threshold = hr->initialize_threshold();
 361   }
 362   prepare_for_compaction_work(&_cp, hr, end);
 363 }
 364 
 365 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 366                                                           HeapRegion* hr,
 367                                                           HeapWord* end) {
 368   hr->prepare_for_compaction(cp);
 369   // Also clear the part of the card table that will be unused after
 370   // compaction.
 371   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 372 }
 373 
 374 void G1PrepareCompactClosure::update_sets() {
 375   // We'll recalculate total used bytes and recreate the free list
 376   // at the end of the GC, so no point in updating those values here.
 377   _g1h->remove_from_old_sets(0, _humongous_regions_removed);
 378 }
 379 
 380 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 381   if (hr->is_humongous()) {
 382     oop obj = oop(hr->humongous_start_region()->bottom());
 383     if (hr->is_starts_humongous() && obj->is_gc_marked()) {
 384       obj->forward_to(obj);
 385     }
 386     if (!obj->is_gc_marked()) {
 387       free_humongous_region(hr);
 388     }
 389   } else if (!hr->is_pinned()) {
 390     prepare_for_compaction(hr, hr->end());
 391   }
 392   return false;
 393 }