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/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.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.inline.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(Trace, gc) 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   // Process reference objects found during marking
 141   ReferenceProcessor* rp = GenMarkSweep::ref_processor();
 142   assert(rp == g1h->ref_processor_stw(), "Sanity");
 143 
 144   rp->setup_policy(clear_all_softrefs);
 145   const ReferenceProcessorStats& stats =
 146     rp->process_discovered_references(&GenMarkSweep::is_alive,
 147                                       &GenMarkSweep::keep_alive,
 148                                       &GenMarkSweep::follow_stack_closure,
 149                                       NULL,
 150                                       gc_timer());
 151   gc_tracer()->report_gc_reference_stats(stats);
 152 
 153 
 154   // This is the point where the entire marking should have completed.
 155   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 156 
 157   // Unload classes and purge the SystemDictionary.
 158   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
 159 
 160   // Unload nmethods.
 161   CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
 162 
 163   // Prune dead klasses from subklass/sibling/implementor lists.
 164   Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
 165 
 166   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 167   g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 168 
 169   if (VerifyDuringGC) {
 170     HandleMark hm;  // handle scope
 171 #if defined(COMPILER2) || INCLUDE_JVMCI
 172     DerivedPointerTableDeactivate dpt_deact;
 173 #endif
 174     g1h->prepare_for_verify();
 175     // Note: we can verify only the heap here. When an object is
 176     // marked, the previous value of the mark word (including
 177     // identity hash values, ages, etc) is preserved, and the mark
 178     // word is set to markOop::marked_value - effectively removing
 179     // any hash values from the mark word. These hash values are
 180     // used when verifying the dictionaries and so removing them
 181     // from the mark word can make verification of the dictionaries
 182     // fail. At the end of the GC, the original mark word values
 183     // (including hash values) are restored to the appropriate
 184     // objects.
 185     GCTraceTime(Info, gc, verify)("During GC (full)");
 186     g1h->verify(VerifyOption_G1UseMarkWord);





 187   }
 188 
 189   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 190 }
 191 
 192 
 193 void G1MarkSweep::mark_sweep_phase2() {
 194   // Now all live objects are marked, compute the new object addresses.
 195 
 196   // It is not required that we traverse spaces in the same order in
 197   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 198   // tracking expects us to do so. See comment under phase4.
 199 
 200   GCTraceTime(Trace, gc) tm("Phase 2: Compute new object addresses", gc_timer());
 201 
 202   prepare_compaction();
 203 }
 204 
 205 class G1AdjustPointersClosure: public HeapRegionClosure {
 206  public:
 207   bool doHeapRegion(HeapRegion* r) {
 208     if (r->is_humongous()) {
 209       if (r->is_starts_humongous()) {
 210         // We must adjust the pointers on the single H object.
 211         oop obj = oop(r->bottom());
 212         // point all the oops to the new location
 213         MarkSweep::adjust_pointers(obj);
 214       }
 215     } else if (!r->is_pinned()) {
 216       // This really ought to be "as_CompactibleSpace"...
 217       r->adjust_pointers();
 218     }
 219     return false;
 220   }
 221 };
 222 
 223 class G1AlwaysTrueClosure: public BoolObjectClosure {
 224 public:
 225   bool do_object_b(oop p) { return true; }
 226 };
 227 static G1AlwaysTrueClosure always_true;
 228 
 229 void G1MarkSweep::mark_sweep_phase3() {
 230   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 231 
 232   // Adjust the pointers to reflect the new locations
 233   GCTraceTime(Trace, gc) tm("Phase 3: Adjust pointers", gc_timer());
 234 
 235   // Need cleared claim bits for the roots processing
 236   ClassLoaderDataGraph::clear_claimed_marks();
 237 
 238   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 239   {
 240     G1RootProcessor root_processor(g1h, 1);
 241     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 242                                      &GenMarkSweep::adjust_cld_closure,
 243                                      &adjust_code_closure);
 244   }
 245 
 246   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 247   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 248 
 249   // Now adjust pointers in remaining weak roots.  (All of which should
 250   // have been cleared if they pointed to non-surviving objects.)
 251   JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
 252 
 253   if (G1StringDedup::is_enabled()) {
 254     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 255   }
 256 
 257   GenMarkSweep::adjust_marks();
 258 
 259   G1AdjustPointersClosure blk;
 260   g1h->heap_region_iterate(&blk);
 261 }
 262 
 263 class G1SpaceCompactClosure: public HeapRegionClosure {
 264 public:
 265   G1SpaceCompactClosure() {}
 266 
 267   bool doHeapRegion(HeapRegion* hr) {
 268     if (hr->is_humongous()) {
 269       if (hr->is_starts_humongous()) {
 270         oop obj = oop(hr->bottom());
 271         if (obj->is_gc_marked()) {
 272           obj->init_mark();
 273         } else {
 274           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 275         }
 276       }
 277       hr->reset_during_compaction();
 278     } else if (!hr->is_pinned()) {
 279       hr->compact();
 280     }
 281     return false;
 282   }
 283 };
 284 
 285 void G1MarkSweep::mark_sweep_phase4() {
 286   // All pointers are now adjusted, move objects accordingly
 287 
 288   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 289   // in the same order in phase2, phase3 and phase4. We don't quite do that
 290   // here (code and comment not fixed for perm removal), so we tell the validate code
 291   // to use a higher index (saved from phase2) when verifying perm_gen.
 292   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 293 
 294   GCTraceTime(Trace, gc) tm("Phase 4: Move objects", gc_timer());
 295 
 296   G1SpaceCompactClosure blk;
 297   g1h->heap_region_iterate(&blk);
 298 
 299 }
 300 
 301 void G1MarkSweep::enable_archive_object_check() {
 302   assert(!_archive_check_enabled, "archive range check already enabled");
 303   _archive_check_enabled = true;
 304   size_t length = Universe::heap()->max_capacity();
 305   _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
 306                                  (HeapWord*)Universe::heap()->base() + length,
 307                                  HeapRegion::GrainBytes);
 308 }
 309 
 310 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
 311   assert(_archive_check_enabled, "archive range check not enabled");
 312   _archive_region_map.set_by_address(range, is_archive);
 313 }
 314 
 315 bool G1MarkSweep::in_archive_range(oop object) {
 316   // This is the out-of-line part of is_archive_object test, done separately
 317   // to avoid additional performance impact when the check is not enabled.
 318   return _archive_region_map.get_by_address((HeapWord*)object);
 319 }
 320 
 321 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 322   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 323   g1h->heap_region_iterate(blk);
 324   blk->update_sets();
 325 }
 326 
 327 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 328   HeapWord* end = hr->end();
 329   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 330 
 331   hr->set_containing_set(NULL);
 332   _humongous_regions_removed.increment(1u, hr->capacity());
 333 
 334   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
 335   prepare_for_compaction(hr, end);
 336   dummy_free_list.remove_all();
 337 }
 338 
 339 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 340   // If this is the first live region that we came across which we can compact,
 341   // initialize the CompactPoint.
 342   if (!is_cp_initialized()) {
 343     _cp.space = hr;
 344     _cp.threshold = hr->initialize_threshold();
 345   }
 346   prepare_for_compaction_work(&_cp, hr, end);
 347 }
 348 
 349 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 350                                                           HeapRegion* hr,
 351                                                           HeapWord* end) {
 352   hr->prepare_for_compaction(cp);
 353   // Also clear the part of the card table that will be unused after
 354   // compaction.
 355   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 356 }
 357 
 358 void G1PrepareCompactClosure::update_sets() {
 359   // We'll recalculate total used bytes and recreate the free list
 360   // at the end of the GC, so no point in updating those values here.
 361   HeapRegionSetCount empty_set;
 362   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
 363 }
 364 
 365 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 366   if (hr->is_humongous()) {
 367     oop obj = oop(hr->humongous_start_region()->bottom());
 368     if (hr->is_starts_humongous() && obj->is_gc_marked()) {
 369       obj->forward_to(obj);
 370     }
 371     if (!obj->is_gc_marked()) {
 372       free_humongous_region(hr);
 373     }
 374   } else if (!hr->is_pinned()) {
 375     prepare_for_compaction(hr, hr->end());
 376   }
 377   return false;
 378 }
--- EOF ---