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/g1FullGCScope.hpp"

    33 #include "gc/g1/g1MarkSweep.hpp"

    34 #include "gc/g1/g1RootProcessor.hpp"

    35 #include "gc/g1/g1StringDedup.hpp"

    36 #include "gc/serial/markSweep.inline.hpp"

    37 #include "gc/shared/gcHeapSummary.hpp"

    38 #include "gc/shared/gcLocker.hpp"

    39 #include "gc/shared/gcTimer.hpp"

    40 #include "gc/shared/gcTrace.hpp"

    41 #include "gc/shared/gcTraceTime.inline.hpp"

    42 #include "gc/shared/genCollectedHeap.hpp"

    43 #include "gc/shared/modRefBarrierSet.hpp"

    44 #include "gc/shared/referencePolicy.hpp"

    45 #include "gc/shared/space.hpp"

    46 #include "oops/instanceRefKlass.hpp"

    47 #include "oops/oop.inline.hpp"

    48 #include "prims/jvmtiExport.hpp"

    49 #include "runtime/atomic.hpp"

    50 #include "runtime/biasedLocking.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   HandleMark hm;  // Discard invalid handles created during gc

    63 

    64 #if defined(COMPILER2) || INCLUDE_JVMCI

    65   DerivedPointerTable::clear();

    66 #endif

    67 #ifdef ASSERT

    68   if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {

    69     assert(clear_all_softrefs, "Policy should have been checked earler");

    70   }

    71 #endif

    72   // hook up weak ref data so it can be used during Mark-Sweep

    73   assert(GenMarkSweep::ref_processor() == NULL, "no stomping");

    74   assert(rp != NULL, "should be non-NULL");

    75   assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");

    76 

    77   GenMarkSweep::set_ref_processor(rp);

    78   rp->setup_policy(clear_all_softrefs);

    79 

    80   // When collecting the permanent generation Method*s may be moving,

    81   // so we either have to flush all bcp data or convert it into bci.

    82   CodeCache::gc_prologue();

    83 

    84   bool marked_for_unloading = false;

    85 

    86   allocate_stacks();

    87 

    88   // We should save the marks of the currently locked biased monitors.

    89   // The marking doesn't preserve the marks of biased objects.

    90   BiasedLocking::preserve_marks();

    91 

    92   // Process roots and do the marking.

    93   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);

    94 

    95   // Prepare compaction.

    96   mark_sweep_phase2();

    97 

    98 #if defined(COMPILER2) || INCLUDE_JVMCI

    99   // Don't add any more derived pointers during phase3

   100   DerivedPointerTable::set_active(false);

   101 #endif

   102 

   103   // Adjust all pointers.

   104   mark_sweep_phase3();

   105 

   106   // Do the actual compaction.

   107   mark_sweep_phase4();

   108 

   109   GenMarkSweep::restore_marks();

   110   BiasedLocking::restore_marks();

   111   GenMarkSweep::deallocate_stacks();

   112 

   113 #if defined(COMPILER2) || INCLUDE_JVMCI

   114   // Now update the derived pointers.

   115   DerivedPointerTable::update_pointers();

   116 #endif

   117 

   118   CodeCache::gc_epilogue();

   119   JvmtiExport::gc_epilogue();

   120 

   121   // refs processing: clean slate

   122   GenMarkSweep::set_ref_processor(NULL);

   123 }

   124 

   125 STWGCTimer* G1MarkSweep::gc_timer() {

   126   return G1FullGCScope::instance()->timer();

   127 }

   128 

   129 SerialOldTracer* G1MarkSweep::gc_tracer() {

   130   return G1FullGCScope::instance()->tracer();

   131 }

   132 

   133 void G1MarkSweep::allocate_stacks() {

   134   GenMarkSweep::_preserved_count_max = 0;

   135   GenMarkSweep::_preserved_marks = NULL;

   136   GenMarkSweep::_preserved_count = 0;

   137 }

   138 

   139 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,

   140                                     bool clear_all_softrefs) {

   141   // Recursively traverse all live objects and mark them

   142   GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());

   143 

   144   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   145 

   146   // Need cleared claim bits for the roots processing

   147   ClassLoaderDataGraph::clear_claimed_marks();

   148 

   149   MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);

   150   {

   151     G1RootProcessor root_processor(g1h, 1);

   152     if (ClassUnloading) {

   153       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,

   154                                           &GenMarkSweep::follow_cld_closure,

   155                                           &follow_code_closure);

   156     } else {

   157       root_processor.process_all_roots_no_string_table(

   158                                           &GenMarkSweep::follow_root_closure,

   159                                           &GenMarkSweep::follow_cld_closure,

   160                                           &follow_code_closure);

   161     }

   162   }

   163 

   164   {

   165     GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());

   166 

   167     // Process reference objects found during marking

   168     ReferenceProcessor* rp = GenMarkSweep::ref_processor();

   169     assert(rp == g1h->ref_processor_stw(), "Sanity");

   170 

   171     rp->setup_policy(clear_all_softrefs);

   172     ReferenceProcessorPhaseTimes pt(gc_timer(), rp->num_q());

   173 

   174     const ReferenceProcessorStats& stats =

   175         rp->process_discovered_references(&GenMarkSweep::is_alive,

   176                                           &GenMarkSweep::keep_alive,

   177                                           &GenMarkSweep::follow_stack_closure,

   178                                           NULL,

   179                                           &pt);

   180     gc_tracer()->report_gc_reference_stats(stats);

   181     pt.print_all_references();

   182   }

   183 

   184   // This is the point where the entire marking should have completed.

   185   assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");

   186 

   187   if (ClassUnloading) {

   188     GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());

   189 

   190     // Unload classes and purge the SystemDictionary.

   191     bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive, gc_timer());

   192 

   193     g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class);

   194   } else {

   195     GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer());

   196     g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled());

   197   }

   198 

   199   if (VerifyDuringGC) {

   200     HandleMark hm;  // handle scope

   201 #if defined(COMPILER2) || INCLUDE_JVMCI

   202     DerivedPointerTableDeactivate dpt_deact;

   203 #endif

   204     g1h->prepare_for_verify();

   205     // Note: we can verify only the heap here. When an object is

   206     // marked, the previous value of the mark word (including

   207     // identity hash values, ages, etc) is preserved, and the mark

   208     // word is set to markOop::marked_value - effectively removing

   209     // any hash values from the mark word. These hash values are

   210     // used when verifying the dictionaries and so removing them

   211     // from the mark word can make verification of the dictionaries

   212     // fail. At the end of the GC, the original mark word values

   213     // (including hash values) are restored to the appropriate

   214     // objects.

   215     GCTraceTime(Info, gc, verify)("During GC (full)");

   216     g1h->verify(VerifyOption_G1UseMarkWord);

   217   }

   218 

   219   gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);

   220 }

   221 

   222 

   223 void G1MarkSweep::mark_sweep_phase2() {

   224   // Now all live objects are marked, compute the new object addresses.

   225 

   226   // It is not required that we traverse spaces in the same order in

   227   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops

   228   // tracking expects us to do so. See comment under phase4.

   229 

   230   GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());

   231 

   232   prepare_compaction();

   233 }

   234 

   235 class G1AdjustPointersClosure: public HeapRegionClosure {

   236  public:

   237   bool doHeapRegion(HeapRegion* r) {

   238     if (r->is_humongous()) {

   239       if (r->is_starts_humongous()) {

   240         // We must adjust the pointers on the single H object.

   241         oop obj = oop(r->bottom());

   242         // point all the oops to the new location

   243         MarkSweep::adjust_pointers(obj);

   244       }

   245     } else if (!r->is_closed_archive()) {

   246       // This really ought to be "as_CompactibleSpace"...

   247       r->adjust_pointers();

   248     }

   249     return false;

   250   }

   251 };

   252 

   253 void G1MarkSweep::mark_sweep_phase3() {

   254   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   255 

   256   // Adjust the pointers to reflect the new locations

   257   GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());

   258 

   259   // Need cleared claim bits for the roots processing

   260   ClassLoaderDataGraph::clear_claimed_marks();

   261 

   262   CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);

   263   {

   264     G1RootProcessor root_processor(g1h, 1);

   265     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,

   266                                      &GenMarkSweep::adjust_cld_closure,

   267                                      &adjust_code_closure);

   268   }

   269 

   270   assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");

   271   g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);

   272 

   273   // Now adjust pointers in remaining weak roots.  (All of which should

   274   // have been cleared if they pointed to non-surviving objects.)

   275   JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);

   276 

   277   if (G1StringDedup::is_enabled()) {

   278     G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);

   279   }

   280 

   281   GenMarkSweep::adjust_marks();

   282 

   283   G1AdjustPointersClosure blk;

   284   g1h->heap_region_iterate(&blk);

   285 }

   286 

   287 class G1SpaceCompactClosure: public HeapRegionClosure {

   288 public:

   289   G1SpaceCompactClosure() {}

   290 

   291   bool doHeapRegion(HeapRegion* hr) {

   292     if (hr->is_humongous()) {

   293       if (hr->is_starts_humongous()) {

   294         oop obj = oop(hr->bottom());

   295         if (obj->is_gc_marked()) {

   296           obj->init_mark();

   297         } else {

   298           assert(hr->is_empty(), "Should have been cleared in phase 2.");

   299         }

   300       }

   301       hr->reset_during_compaction();

   302     } else if (!hr->is_pinned()) {

   303       hr->compact();

   304     }

   305     return false;

   306   }

   307 };

   308 

   309 void G1MarkSweep::mark_sweep_phase4() {

   310   // All pointers are now adjusted, move objects accordingly

   311 

   312   // The ValidateMarkSweep live oops tracking expects us to traverse spaces

   313   // in the same order in phase2, phase3 and phase4. We don't quite do that

   314   // here (code and comment not fixed for perm removal), so we tell the validate code

   315   // to use a higher index (saved from phase2) when verifying perm_gen.

   316   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   317 

   318   GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());

   319 

   320   G1SpaceCompactClosure blk;

   321   g1h->heap_region_iterate(&blk);

   322 

   323 }

   324 

   325 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {

   326   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   327   g1h->heap_region_iterate(blk);

   328   blk->update_sets();

   329 }

   330 

   331 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {

   332   HeapWord* end = hr->end();

   333   FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");

   334 

   335   hr->set_containing_set(NULL);

   336   _humongous_regions_removed++;

   337 

   338   _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);

   339   prepare_for_compaction(hr, end);

   340   dummy_free_list.remove_all();

   341 }

   342 

   343 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {

   344   // If this is the first live region that we came across which we can compact,

   345   // initialize the CompactPoint.

   346   if (!is_cp_initialized()) {

   347     _cp.space = hr;

   348     _cp.threshold = hr->initialize_threshold();

   349   }

   350   prepare_for_compaction_work(&_cp, hr, end);

   351 }

   352 

   353 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,

   354                                                           HeapRegion* hr,

   355                                                           HeapWord* end) {

   356   hr->prepare_for_compaction(cp);

   357   // Also clear the part of the card table that will be unused after

   358   // compaction.

   359   _mrbs->clear(MemRegion(hr->compaction_top(), end));

   360 }

   361 

   362 void G1PrepareCompactClosure::update_sets() {

   363   // We'll recalculate total used bytes and recreate the free list

   364   // at the end of the GC, so no point in updating those values here.

   365   _g1h->remove_from_old_sets(0, _humongous_regions_removed);

   366 }

   367 

   368 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {

   369   if (hr->is_humongous()) {

   370     oop obj = oop(hr->humongous_start_region()->bottom());

   371     if (hr->is_starts_humongous() && obj->is_gc_marked()) {

   372       obj->forward_to(obj);

   373     }

   374     if (!obj->is_gc_marked()) {

   375       free_humongous_region(hr);

   376     }

   377   } else if (!hr->is_pinned()) {

   378     prepare_for_compaction(hr, hr->end());

   379   }

   380   return false;

   381 }