1 /*
   2  * Copyright (c) 2001, 2018, 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_implementation/g1/g1Log.hpp"
  33 #include "gc_implementation/g1/g1MarkSweep.hpp"
  34 #include "gc_implementation/g1/g1RootProcessor.hpp"
  35 #include "gc_implementation/g1/g1StringDedup.hpp"
  36 #include "gc_implementation/shared/gcHeapSummary.hpp"
  37 #include "gc_implementation/shared/gcTimer.hpp"
  38 #include "gc_implementation/shared/gcTrace.hpp"
  39 #include "gc_implementation/shared/gcTraceTime.hpp"
  40 #include "memory/gcLocker.hpp"
  41 #include "memory/genCollectedHeap.hpp"
  42 #include "memory/modRefBarrierSet.hpp"
  43 #include "memory/referencePolicy.hpp"
  44 #include "memory/space.hpp"
  45 #include "oops/instanceRefKlass.hpp"
  46 #include "oops/oop.inline.hpp"
  47 #include "prims/jvmtiExport.hpp"
  48 #include "runtime/biasedLocking.hpp"
  49 #include "runtime/fprofiler.hpp"
  50 #include "runtime/synchronizer.hpp"
  51 #include "runtime/thread.hpp"
  52 #include "runtime/vmThread.hpp"
  53 #include "utilities/copy.hpp"
  54 #include "utilities/events.hpp"
  55 
  56 class HeapRegion;
  57 
  58 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
  59                                       bool clear_all_softrefs) {
  60   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
  61 
  62   SharedHeap* sh = SharedHeap::heap();
  63 #ifdef ASSERT
  64   if (sh->collector_policy()->should_clear_all_soft_refs()) {
  65     assert(clear_all_softrefs, "Policy should have been checked earler");
  66   }
  67 #endif
  68   // hook up weak ref data so it can be used during Mark-Sweep
  69   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
  70   assert(rp != NULL, "should be non-NULL");
  71   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
  72 
  73   GenMarkSweep::_ref_processor = rp;
  74   rp->setup_policy(clear_all_softrefs);
  75 
  76   // When collecting the permanent generation Method*s may be moving,
  77   // so we either have to flush all bcp data or convert it into bci.
  78   CodeCache::gc_prologue();
  79   Threads::gc_prologue();
  80 
  81   bool marked_for_unloading = false;
  82 
  83   allocate_stacks();
  84 
  85   // We should save the marks of the currently locked biased monitors.
  86   // The marking doesn't preserve the marks of biased objects.
  87   BiasedLocking::preserve_marks();
  88 
  89   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
  90 
  91   mark_sweep_phase2();
  92 
  93   // Don't add any more derived pointers during phase3
  94   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
  95 
  96   mark_sweep_phase3();
  97 
  98   mark_sweep_phase4();
  99 
 100   GenMarkSweep::restore_marks();
 101   BiasedLocking::restore_marks();
 102   GenMarkSweep::deallocate_stacks();
 103 
 104   // "free at last gc" is calculated from these.
 105   // CHF: cheating for now!!!
 106   //  Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
 107   //  Universe::set_heap_used_at_last_gc(Universe::heap()->used());
 108 
 109   Threads::gc_epilogue();
 110   CodeCache::gc_epilogue();
 111   JvmtiExport::gc_epilogue();
 112 
 113   // refs processing: clean slate
 114   GenMarkSweep::_ref_processor = NULL;
 115 }
 116 
 117 
 118 void G1MarkSweep::allocate_stacks() {
 119   GenMarkSweep::_preserved_count_max = 0;
 120   GenMarkSweep::_preserved_marks = NULL;
 121   GenMarkSweep::_preserved_count = 0;
 122 }
 123 
 124 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
 125                                     bool clear_all_softrefs) {
 126   // Recursively traverse all live objects and mark them
 127   GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 128   GenMarkSweep::trace(" 1");
 129 
 130   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 131 
 132   // Need cleared claim bits for the roots processing
 133   ClassLoaderDataGraph::clear_claimed_marks();
 134 
 135   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
 136   {
 137     G1RootProcessor root_processor(g1h);
 138     if (ClassUnloading) {
 139       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
 140                                           &GenMarkSweep::follow_cld_closure,
 141                                           &follow_code_closure);
 142     } else {
 143       root_processor.process_all_roots_no_string_table(
 144                                           &GenMarkSweep::follow_root_closure,
 145                                           &GenMarkSweep::follow_cld_closure,
 146                                           &follow_code_closure);
 147     }
 148   }
 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()->gc_id());
 162   gc_tracer()->report_gc_reference_stats(stats);
 163 
 164 
 165   // This is the point where the entire marking should have completed.
 166   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
 167 
 168   if (ClassUnloading) {
 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   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
 180   G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
 181 
 182   if (VerifyDuringGC) {
 183     HandleMark hm;  // handle scope
 184     COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
 185     Universe::heap()->prepare_for_verify();
 186     // Note: we can verify only the heap here. When an object is
 187     // marked, the previous value of the mark word (including
 188     // identity hash values, ages, etc) is preserved, and the mark
 189     // word is set to markOop::marked_value - effectively removing
 190     // any hash values from the mark word. These hash values are
 191     // used when verifying the dictionaries and so removing them
 192     // from the mark word can make verification of the dictionaries
 193     // fail. At the end of the GC, the orginal mark word values
 194     // (including hash values) are restored to the appropriate
 195     // objects.
 196     if (!VerifySilently) {
 197       gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
 198     }
 199     Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
 200     if (!VerifySilently) {
 201       gclog_or_tty->print_cr("]");
 202     }
 203   }
 204 
 205   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
 206 }
 207 
 208 
 209 void G1MarkSweep::mark_sweep_phase2() {
 210   // Now all live objects are marked, compute the new object addresses.
 211 
 212   // It is not required that we traverse spaces in the same order in
 213   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
 214   // tracking expects us to do so. See comment under phase4.
 215 
 216   GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 217   GenMarkSweep::trace("2");
 218 
 219   prepare_compaction();
 220 }
 221 
 222 class G1AdjustPointersClosure: public HeapRegionClosure {
 223  public:
 224   bool doHeapRegion(HeapRegion* r) {
 225     if (r->isHumongous()) {
 226       if (r->startsHumongous()) {
 227         // We must adjust the pointers on the single H object.
 228         oop obj = oop(r->bottom());
 229         // point all the oops to the new location
 230         obj->adjust_pointers();
 231       }
 232     } else {
 233       // This really ought to be "as_CompactibleSpace"...
 234       r->adjust_pointers();
 235     }
 236     return false;
 237   }
 238 };
 239 
 240 void G1MarkSweep::mark_sweep_phase3() {
 241   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 242 
 243   // Adjust the pointers to reflect the new locations
 244   GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 245   GenMarkSweep::trace("3");
 246 
 247   // Need cleared claim bits for the roots processing
 248   ClassLoaderDataGraph::clear_claimed_marks();
 249 
 250   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
 251   {
 252     G1RootProcessor root_processor(g1h);
 253     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
 254                                      &GenMarkSweep::adjust_cld_closure,
 255                                      &adjust_code_closure);
 256   }
 257 
 258   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
 259   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 260 
 261   // Now adjust pointers in remaining weak roots.  (All of which should
 262   // have been cleared if they pointed to non-surviving objects.)
 263   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
 264 
 265   if (G1StringDedup::is_enabled()) {
 266     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
 267   }
 268 
 269   GenMarkSweep::adjust_marks();
 270 
 271   G1AdjustPointersClosure blk;
 272   g1h->heap_region_iterate(&blk);
 273 }
 274 
 275 class G1SpaceCompactClosure: public HeapRegionClosure {
 276 public:
 277   G1SpaceCompactClosure() {}
 278 
 279   bool doHeapRegion(HeapRegion* hr) {
 280     if (hr->isHumongous()) {
 281       if (hr->startsHumongous()) {
 282         oop obj = oop(hr->bottom());
 283         if (obj->is_gc_marked()) {
 284           obj->init_mark();
 285         } else {
 286           assert(hr->is_empty(), "Should have been cleared in phase 2.");
 287         }
 288         hr->reset_during_compaction();
 289       }
 290     } else {
 291       hr->compact();
 292     }
 293     return false;
 294   }
 295 };
 296 
 297 void G1MarkSweep::mark_sweep_phase4() {
 298   // All pointers are now adjusted, move objects accordingly
 299 
 300   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
 301   // in the same order in phase2, phase3 and phase4. We don't quite do that
 302   // here (code and comment not fixed for perm removal), so we tell the validate code
 303   // to use a higher index (saved from phase2) when verifying perm_gen.
 304   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 305 
 306   GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
 307   GenMarkSweep::trace("4");
 308 
 309   G1SpaceCompactClosure blk;
 310   g1h->heap_region_iterate(&blk);
 311 
 312 }
 313 
 314 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
 315   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 316   g1h->heap_region_iterate(blk);
 317   blk->update_sets();
 318 }
 319 
 320 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
 321   HeapWord* end = hr->end();
 322   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
 323 
 324   assert(hr->startsHumongous(),
 325          "Only the start of a humongous region should be freed.");
 326 
 327   hr->set_containing_set(NULL);
 328   _humongous_regions_removed.increment(1u, hr->capacity());
 329 
 330   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
 331   prepare_for_compaction(hr, end);
 332   dummy_free_list.remove_all();
 333 }
 334 
 335 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
 336   // If this is the first live region that we came across which we can compact,
 337   // initialize the CompactPoint.
 338   if (!is_cp_initialized()) {
 339     _cp.space = hr;
 340     _cp.threshold = hr->initialize_threshold();
 341   }
 342   prepare_for_compaction_work(&_cp, hr, end);
 343 }
 344 
 345 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
 346                                                           HeapRegion* hr,
 347                                                           HeapWord* end) {
 348   hr->prepare_for_compaction(cp);
 349   // Also clear the part of the card table that will be unused after
 350   // compaction.
 351   _mrbs->clear(MemRegion(hr->compaction_top(), end));
 352 }
 353 
 354 void G1PrepareCompactClosure::update_sets() {
 355   // We'll recalculate total used bytes and recreate the free list
 356   // at the end of the GC, so no point in updating those values here.
 357   HeapRegionSetCount empty_set;
 358   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
 359 }
 360 
 361 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
 362   if (hr->isHumongous()) {
 363     if (hr->startsHumongous()) {
 364       oop obj = oop(hr->bottom());
 365       if (obj->is_gc_marked()) {
 366         obj->forward_to(obj);
 367       } else  {
 368         free_humongous_region(hr);
 369       }
 370     } else {
 371       assert(hr->continuesHumongous(), "Invalid humongous.");
 372     }
 373   } else {
 374     prepare_for_compaction(hr, hr->end());
 375   }
 376   return false;
 377 }