1 /*
   2  * Copyright (c) 2001, 2017, 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 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
  60                                       bool clear_all_softrefs) {
  61   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  62 
  63   // hook up weak ref data so it can be used during Mark-Sweep
  64   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
  65   assert(rp != NULL, "should be non-NULL");
  66   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
  67 
  68   GenMarkSweep::set_ref_processor(rp);
  69   rp->setup_policy(clear_all_softrefs);
  70 
  71   // When collecting the permanent generation Method*s may be moving,
  72   // so we either have to flush all bcp data or convert it into bci.
  73   CodeCache::gc_prologue();
  74 
  75   bool marked_for_unloading = false;
  76 
  77   allocate_stacks();
  78 
  79   // We should save the marks of the currently locked biased monitors.
  80   // The marking doesn't preserve the marks of biased objects.
  81   BiasedLocking::preserve_marks();
  82 
  83   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
  84 
  85   mark_sweep_phase2();
  86 
  87 #if defined(COMPILER2) || INCLUDE_JVMCI
  88   // Don't add any more derived pointers during phase3
  89   DerivedPointerTable::set_active(false);
  90 #endif
  91 
  92   mark_sweep_phase3();
  93 
  94   mark_sweep_phase4();
  95 
  96   GenMarkSweep::restore_marks();
  97   BiasedLocking::restore_marks();
  98   GenMarkSweep::deallocate_stacks();
  99 
 100   CodeCache::gc_epilogue();
 101   JvmtiExport::gc_epilogue();
 102 
 103   // refs processing: clean slate
 104   GenMarkSweep::set_ref_processor(NULL);
 105 }
 106 
 107 
 108 void G1MarkSweep::allocate_stacks() {
 109   GenMarkSweep::_preserved_count_max = 0;
 110   GenMarkSweep::_preserved_marks = NULL;
 111   GenMarkSweep::_preserved_count = 0;
 112 }
 113 
 114 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
 115                                     bool clear_all_softrefs) {
 116   // Recursively traverse all live objects and mark them
 117   GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
 118 
 119   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 120 
 121   // Need cleared claim bits for the roots processing
 122   ClassLoaderDataGraph::clear_claimed_marks();
 123 
 124   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
 125   {
 126     G1RootProcessor root_processor(g1h, 1);
 127     if (ClassUnloading) {
 128       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
 129                                           &GenMarkSweep::follow_cld_closure,
 130                                           &follow_code_closure);
 131     } else {
 132       root_processor.process_all_roots_no_string_table(
 133                                           &GenMarkSweep::follow_root_closure,
 134                                           &GenMarkSweep::follow_cld_closure,
 135                                           &follow_code_closure);
 136     }
 137   }
 138 
 139   {
 140     GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
 141 
 142     // Process reference objects found during marking
 143     ReferenceProcessor* rp = GenMarkSweep::ref_processor();
 144     assert(rp == g1h->ref_processor_stw(), "Sanity");
 145 
 146     rp->setup_policy(clear_all_softrefs);
 147     const ReferenceProcessorStats& stats =
 148         rp->process_discovered_references(&GenMarkSweep::is_alive,
 149                                           &GenMarkSweep::keep_alive,
 150                                           &GenMarkSweep::follow_stack_closure,
 151                                           NULL,
 152                                           gc_timer());
 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   if (ClassUnloading) {
 160     GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
 161 
 162     // Unload classes and purge the SystemDictionary.
 163     bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive, gc_timer());
 164 
 165     g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class);
 166   } else {
 167     GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer());
 168     g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled());
 169   }
 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     GCTraceTime(Info, gc, verify)("During GC (full)");
 188     g1h->verify(VerifyOption_G1UseMarkWord);
 189   }
 190 
 191   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 192 }
 193 
 194 
 195 void G1MarkSweep::mark_sweep_phase2() {
 196   // Now all live objects are marked, compute the new object addresses.
 197 
 198   // It is not required that we traverse spaces in the same order in
 199   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 200   // tracking expects us to do so. See comment under phase4.
 201 
 202   GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
 203 
 204   prepare_compaction();
 205 }
 206 
 207 class G1AdjustPointersClosure: public HeapRegionClosure {
 208  public:
 209   bool doHeapRegion(HeapRegion* r) {
 210     if (r->is_humongous()) {
 211       if (r->is_starts_humongous()) {
 212         // We must adjust the pointers on the single H object.
 213         oop obj = oop(r->bottom());
 214         // point all the oops to the new location
 215         MarkSweep::adjust_pointers(obj);
 216       }
 217     } else if (!r->is_pinned()) {
 218       // This really ought to be "as_CompactibleSpace"...
 219       r->adjust_pointers();
 220     }
 221     return false;
 222   }
 223 };
 224 
 225 void G1MarkSweep::mark_sweep_phase3() {
 226   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 227 
 228   // Adjust the pointers to reflect the new locations
 229   GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
 230 
 231   // Need cleared claim bits for the roots processing
 232   ClassLoaderDataGraph::clear_claimed_marks();
 233 
 234   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 235   {
 236     G1RootProcessor root_processor(g1h, 1);
 237     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 238                                      &GenMarkSweep::adjust_cld_closure,
 239                                      &adjust_code_closure);
 240   }
 241 
 242   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 243   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 244 
 245   // Now adjust pointers in remaining weak roots.  (All of which should
 246   // have been cleared if they pointed to non-surviving objects.)
 247   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 248 
 249   if (G1StringDedup::is_enabled()) {
 250     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 251   }
 252 
 253   GenMarkSweep::adjust_marks();
 254 
 255   G1AdjustPointersClosure blk;
 256   g1h->heap_region_iterate(&blk);
 257 }
 258 
 259 class G1SpaceCompactClosure: public HeapRegionClosure {
 260 public:
 261   G1SpaceCompactClosure() {}
 262 
 263   bool doHeapRegion(HeapRegion* hr) {
 264     if (hr->is_humongous()) {
 265       if (hr->is_starts_humongous()) {
 266         oop obj = oop(hr->bottom());
 267         if (obj->is_gc_marked()) {
 268           obj->init_mark();
 269         } else {
 270           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 271         }
 272       }
 273       hr->reset_during_compaction();
 274     } else if (!hr->is_pinned()) {
 275       hr->compact();
 276     }
 277     return false;
 278   }
 279 };
 280 
 281 void G1MarkSweep::mark_sweep_phase4() {
 282   // All pointers are now adjusted, move objects accordingly
 283 
 284   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 285   // in the same order in phase2, phase3 and phase4. We don't quite do that
 286   // here (code and comment not fixed for perm removal), so we tell the validate code
 287   // to use a higher index (saved from phase2) when verifying perm_gen.
 288   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 289 
 290   GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
 291 
 292   G1SpaceCompactClosure blk;
 293   g1h->heap_region_iterate(&blk);
 294 
 295 }
 296 
 297 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 298   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 299   g1h->heap_region_iterate(blk);
 300   blk->update_sets();
 301 }
 302 
 303 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 304   HeapWord* end = hr->end();
 305   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 306 
 307   hr->set_containing_set(NULL);
 308   _humongous_regions_removed++;
 309 
 310   _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
 311   prepare_for_compaction(hr, end);
 312   dummy_free_list.remove_all();
 313 }
 314 
 315 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 316   // If this is the first live region that we came across which we can compact,
 317   // initialize the CompactPoint.
 318   if (!is_cp_initialized()) {
 319     _cp.space = hr;
 320     _cp.threshold = hr->initialize_threshold();
 321   }
 322   prepare_for_compaction_work(&_cp, hr, end);
 323 }
 324 
 325 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 326                                                           HeapRegion* hr,
 327                                                           HeapWord* end) {
 328   hr->prepare_for_compaction(cp);
 329   // Also clear the part of the card table that will be unused after
 330   // compaction.
 331   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 332 }
 333 
 334 void G1PrepareCompactClosure::update_sets() {
 335   // We'll recalculate total used bytes and recreate the free list
 336   // at the end of the GC, so no point in updating those values here.
 337   _g1h->remove_from_old_sets(0, _humongous_regions_removed);
 338 }
 339 
 340 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 341   if (hr->is_humongous()) {
 342     oop obj = oop(hr->humongous_start_region()->bottom());
 343     if (hr->is_starts_humongous() && obj->is_gc_marked()) {
 344       obj->forward_to(obj);
 345     }
 346     if (!obj->is_gc_marked()) {
 347       free_humongous_region(hr);
 348     }
 349   } else if (!hr->is_pinned()) {
 350     prepare_for_compaction(hr, hr->end());
 351   }
 352   return false;
 353 }