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     root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
 136                                         &GenMarkSweep::follow_cld_closure,
 137                                         &follow_code_closure);
 138   }
 139 
 140   {
 141     GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
 142 
 143     // Process reference objects found during marking
 144     ReferenceProcessor* rp = GenMarkSweep::ref_processor();
 145     assert(rp == g1h->ref_processor_stw(), "Sanity");
 146 
 147     rp->setup_policy(clear_all_softrefs);
 148     const ReferenceProcessorStats& stats =
 149         rp->process_discovered_references(&GenMarkSweep::is_alive,
 150                                           &GenMarkSweep::keep_alive,
 151                                           &GenMarkSweep::follow_stack_closure,
 152                                           NULL,
 153                                           gc_timer());
 154     gc_tracer()->report_gc_reference_stats(stats);
 155   }
 156 
 157   // This is the point where the entire marking should have completed.
 158   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 159 
 160   {
 161     GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
 162 
 163     // Unload classes and purge the SystemDictionary.
 164     bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
 165 
 166     // Unload nmethods.
 167     CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
 168 
 169     // Prune dead klasses from subklass/sibling/implementor lists.
 170     Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
 171   }
 172 
 173   {
 174     GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
 175     // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 176     g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 177   }
 178 
 179   if (G1StringDedup::is_enabled()) {
 180     GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
 181     G1StringDedup::unlink(&GenMarkSweep::is_alive);
 182   }
 183 
 184   if (VerifyDuringGC) {
 185     HandleMark hm;  // handle scope
 186 #if defined(COMPILER2) || INCLUDE_JVMCI
 187     DerivedPointerTableDeactivate dpt_deact;
 188 #endif
 189     g1h->prepare_for_verify();
 190     // Note: we can verify only the heap here. When an object is
 191     // marked, the previous value of the mark word (including
 192     // identity hash values, ages, etc) is preserved, and the mark
 193     // word is set to markOop::marked_value - effectively removing
 194     // any hash values from the mark word. These hash values are
 195     // used when verifying the dictionaries and so removing them
 196     // from the mark word can make verification of the dictionaries
 197     // fail. At the end of the GC, the original mark word values
 198     // (including hash values) are restored to the appropriate
 199     // objects.
 200     GCTraceTime(Info, gc, verify)("During GC (full)");
 201     g1h->verify(VerifyOption_G1UseMarkWord);
 202   }
 203 
 204   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 205 }
 206 
 207 
 208 void G1MarkSweep::mark_sweep_phase2() {
 209   // Now all live objects are marked, compute the new object addresses.
 210 
 211   // It is not required that we traverse spaces in the same order in
 212   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 213   // tracking expects us to do so. See comment under phase4.
 214 
 215   GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
 216 
 217   prepare_compaction();
 218 }
 219 
 220 class G1AdjustPointersClosure: public HeapRegionClosure {
 221  public:
 222   bool doHeapRegion(HeapRegion* r) {
 223     if (r->is_humongous()) {
 224       if (r->is_starts_humongous()) {
 225         // We must adjust the pointers on the single H object.
 226         oop obj = oop(r->bottom());
 227         // point all the oops to the new location
 228         MarkSweep::adjust_pointers(obj);
 229       }
 230     } else if (!r->is_pinned()) {
 231       // This really ought to be "as_CompactibleSpace"...
 232       r->adjust_pointers();
 233     }
 234     return false;
 235   }
 236 };
 237 
 238 void G1MarkSweep::mark_sweep_phase3() {
 239   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 240 
 241   // Adjust the pointers to reflect the new locations
 242   GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
 243 
 244   // Need cleared claim bits for the roots processing
 245   ClassLoaderDataGraph::clear_claimed_marks();
 246 
 247   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 248   {
 249     G1RootProcessor root_processor(g1h, 1);
 250     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 251                                      &GenMarkSweep::adjust_cld_closure,
 252                                      &adjust_code_closure);
 253   }
 254 
 255   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 256   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 257 
 258   // Now adjust pointers in remaining weak roots.  (All of which should
 259   // have been cleared if they pointed to non-surviving objects.)
 260   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 261 
 262   if (G1StringDedup::is_enabled()) {
 263     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 264   }
 265 
 266   GenMarkSweep::adjust_marks();
 267 
 268   G1AdjustPointersClosure blk;
 269   g1h->heap_region_iterate(&blk);
 270 }
 271 
 272 class G1SpaceCompactClosure: public HeapRegionClosure {
 273 public:
 274   G1SpaceCompactClosure() {}
 275 
 276   bool doHeapRegion(HeapRegion* hr) {
 277     if (hr->is_humongous()) {
 278       if (hr->is_starts_humongous()) {
 279         oop obj = oop(hr->bottom());
 280         if (obj->is_gc_marked()) {
 281           obj->init_mark();
 282         } else {
 283           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 284         }
 285       }
 286       hr->reset_during_compaction();
 287     } else if (!hr->is_pinned()) {
 288       hr->compact();
 289     }
 290     return false;
 291   }
 292 };
 293 
 294 void G1MarkSweep::mark_sweep_phase4() {
 295   // All pointers are now adjusted, move objects accordingly
 296 
 297   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 298   // in the same order in phase2, phase3 and phase4. We don't quite do that
 299   // here (code and comment not fixed for perm removal), so we tell the validate code
 300   // to use a higher index (saved from phase2) when verifying perm_gen.
 301   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 302 
 303   GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
 304 
 305   G1SpaceCompactClosure blk;
 306   g1h->heap_region_iterate(&blk);
 307 
 308 }
 309 
 310 void G1MarkSweep::enable_archive_object_check() {
 311   assert(!_archive_check_enabled, "archive range check already enabled");
 312   _archive_check_enabled = true;
 313   size_t length = Universe::heap()->max_capacity();
 314   _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
 315                                  (HeapWord*)Universe::heap()->base() + length,
 316                                  HeapRegion::GrainBytes);
 317 }
 318 
 319 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
 320   assert(_archive_check_enabled, "archive range check not enabled");
 321   _archive_region_map.set_by_address(range, is_archive);
 322 }
 323 
 324 bool G1MarkSweep::in_archive_range(oop object) {
 325   // This is the out-of-line part of is_archive_object test, done separately
 326   // to avoid additional performance impact when the check is not enabled.
 327   return _archive_region_map.get_by_address((HeapWord*)object);
 328 }
 329 
 330 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 331   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 332   g1h->heap_region_iterate(blk);
 333   blk->update_sets();
 334 }
 335 
 336 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 337   HeapWord* end = hr->end();
 338   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 339 
 340   hr->set_containing_set(NULL);
 341   _humongous_regions_removed++;
 342 
 343   _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
 344   prepare_for_compaction(hr, end);
 345   dummy_free_list.remove_all();
 346 }
 347 
 348 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 349   // If this is the first live region that we came across which we can compact,
 350   // initialize the CompactPoint.
 351   if (!is_cp_initialized()) {
 352     _cp.space = hr;
 353     _cp.threshold = hr->initialize_threshold();
 354   }
 355   prepare_for_compaction_work(&_cp, hr, end);
 356 }
 357 
 358 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 359                                                           HeapRegion* hr,
 360                                                           HeapWord* end) {
 361   hr->prepare_for_compaction(cp);
 362   // Also clear the part of the card table that will be unused after
 363   // compaction.
 364   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 365 }
 366 
 367 void G1PrepareCompactClosure::update_sets() {
 368   // We'll recalculate total used bytes and recreate the free list
 369   // at the end of the GC, so no point in updating those values here.
 370   _g1h->remove_from_old_sets(0, _humongous_regions_removed);
 371 }
 372 
 373 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 374   if (hr->is_humongous()) {
 375     oop obj = oop(hr->humongous_start_region()->bottom());
 376     if (hr->is_starts_humongous() && obj->is_gc_marked()) {
 377       obj->forward_to(obj);
 378     }
 379     if (!obj->is_gc_marked()) {
 380       free_humongous_region(hr);
 381     }
 382   } else if (!hr->is_pinned()) {
 383     prepare_for_compaction(hr, hr->end());
 384   }
 385   return false;
 386 }