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 "gc/shared/weakProcessor.hpp"

    47 #include "oops/instanceRefKlass.hpp"

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

    49 #include "prims/jvmtiExport.hpp"

    50 #include "runtime/atomic.hpp"

    51 #include "runtime/biasedLocking.hpp"

    52 #include "runtime/synchronizer.hpp"

    53 #include "runtime/thread.hpp"

    54 #include "runtime/vmThread.hpp"

    55 #include "utilities/copy.hpp"

    56 #include "utilities/events.hpp"

    57 

    58 class HeapRegion;

    59 

    60 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,

    61                                       bool clear_all_softrefs) {

    62   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");

    63   HandleMark hm;  // Discard invalid handles created during gc

    64 

    65 #if COMPILER2_OR_JVMCI

    66   DerivedPointerTable::clear();

    67 #endif

    68 #ifdef ASSERT

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

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

    71   }

    72 #endif

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

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

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

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

    77 

    78   GenMarkSweep::set_ref_processor(rp);

    79   rp->setup_policy(clear_all_softrefs);

    80 

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

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

    83   CodeCache::gc_prologue();

    84 

    85   bool marked_for_unloading = false;

    86 

    87   allocate_stacks();

    88 

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

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

    91   BiasedLocking::preserve_marks();

    92 

    93   // Process roots and do the marking.

    94   mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);

    95 

    96   // Prepare compaction.

    97   mark_sweep_phase2();

    98 

    99 #if COMPILER2_OR_JVMCI

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

   101   DerivedPointerTable::set_active(false);

   102 #endif

   103 

   104   // Adjust all pointers.

   105   mark_sweep_phase3();

   106 

   107   // Do the actual compaction.

   108   mark_sweep_phase4();

   109 

   110   GenMarkSweep::restore_marks();

   111   BiasedLocking::restore_marks();

   112   GenMarkSweep::deallocate_stacks();

   113 

   114 #if COMPILER2_OR_JVMCI

   115   // Now update the derived pointers.

   116   DerivedPointerTable::update_pointers();

   117 #endif

   118 

   119   CodeCache::gc_epilogue();

   120   JvmtiExport::gc_epilogue();

   121 

   122   // refs processing: clean slate

   123   GenMarkSweep::set_ref_processor(NULL);

   124 }

   125 

   126 STWGCTimer* G1MarkSweep::gc_timer() {

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

   128 }

   129 

   130 SerialOldTracer* G1MarkSweep::gc_tracer() {

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

   132 }

   133 

   134 void G1MarkSweep::allocate_stacks() {

   135   GenMarkSweep::_preserved_count_max = 0;

   136   GenMarkSweep::_preserved_marks = NULL;

   137   GenMarkSweep::_preserved_count = 0;

   138 }

   139 

   140 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,

   141                                     bool clear_all_softrefs) {

   142   // Recursively traverse all live objects and mark them

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

   144 

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

   146 

   147   // Need cleared claim bits for the roots processing

   148   ClassLoaderDataGraph::clear_claimed_marks();

   149 

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

   151   {

   152     G1RootProcessor root_processor(g1h, 1);

   153     if (ClassUnloading) {

   154       root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,

   155                                           &GenMarkSweep::follow_cld_closure,

   156                                           &follow_code_closure);

   157     } else {

   158       root_processor.process_all_roots_no_string_table(

   159                                           &GenMarkSweep::follow_root_closure,

   160                                           &GenMarkSweep::follow_cld_closure,

   161                                           &follow_code_closure);

   162     }

   163   }

   164 

   165   {

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

   167 

   168     // Process reference objects found during marking

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

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

   171 

   172     rp->setup_policy(clear_all_softrefs);

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

   174 

   175     const ReferenceProcessorStats& stats =

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

   177                                           &GenMarkSweep::keep_alive,

   178                                           &GenMarkSweep::follow_stack_closure,

   179                                           NULL,

   180                                           &pt);

   181     gc_tracer()->report_gc_reference_stats(stats);

   182     pt.print_all_references();

   183   }

   184 

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

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

   187 

   188   {

   189     GCTraceTime(Debug, gc, phases) trace("Weak Processing", gc_timer());

   190     WeakProcessor::weak_oops_do(&GenMarkSweep::is_alive, &do_nothing_cl);

   191   }

   192 

   193   if (ClassUnloading) {

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

   195 

   196     // Unload classes and purge the SystemDictionary.

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

   198 

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

   200   } else {

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

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

   203   }

   204 

   205   if (VerifyDuringGC) {

   206     HandleMark hm;  // handle scope

   207 #if COMPILER2_OR_JVMCI

   208     DerivedPointerTableDeactivate dpt_deact;

   209 #endif

   210     g1h->prepare_for_verify();

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

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

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

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

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

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

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

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

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

   220     // objects.

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

   222     g1h->verify(VerifyOption_G1UseMarkWord);

   223   }

   224 

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

   226 }

   227 

   228 

   229 void G1MarkSweep::mark_sweep_phase2() {

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

   231 

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

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

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

   235 

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

   237 

   238   prepare_compaction();

   239 }

   240 

   241 class G1AdjustPointersClosure: public HeapRegionClosure {

   242  public:

   243   bool doHeapRegion(HeapRegion* r) {

   244     if (r->is_humongous()) {

   245       if (r->is_starts_humongous()) {

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

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

   248         // point all the oops to the new location

   249         MarkSweep::adjust_pointers(obj);

   250       }

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

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

   253       r->adjust_pointers();

   254     }

   255     return false;

   256   }

   257 };

   258 

   259 void G1MarkSweep::mark_sweep_phase3() {

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

   261 

   262   // Adjust the pointers to reflect the new locations

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

   264 

   265   // Need cleared claim bits for the roots processing

   266   ClassLoaderDataGraph::clear_claimed_marks();

   267 

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

   269   {

   270     G1RootProcessor root_processor(g1h, 1);

   271     root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,

   272                                      &GenMarkSweep::adjust_cld_closure,

   273                                      &adjust_code_closure);

   274   }

   275 

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

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

   278 

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

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

   281   WeakProcessor::oops_do(&GenMarkSweep::adjust_pointer_closure);

   282 

   283   if (G1StringDedup::is_enabled()) {

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

   285   }

   286 

   287   GenMarkSweep::adjust_marks();

   288 

   289   G1AdjustPointersClosure blk;

   290   g1h->heap_region_iterate(&blk);

   291 }

   292 

   293 class G1SpaceCompactClosure: public HeapRegionClosure {

   294 public:

   295   G1SpaceCompactClosure() {}

   296 

   297   bool doHeapRegion(HeapRegion* hr) {

   298     if (hr->is_humongous()) {

   299       if (hr->is_starts_humongous()) {

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

   301         if (obj->is_gc_marked()) {

   302           obj->init_mark();

   303         } else {

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

   305         }

   306       }

   307       hr->reset_during_compaction();

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

   309       hr->compact();

   310     }

   311     return false;

   312   }

   313 };

   314 

   315 void G1MarkSweep::mark_sweep_phase4() {

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

   317 

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

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

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

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

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

   323 

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

   325 

   326   G1SpaceCompactClosure blk;

   327   g1h->heap_region_iterate(&blk);

   328 

   329 }

   330 

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

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

   333   g1h->heap_region_iterate(blk);

   334   blk->update_sets();

   335 }

   336 

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

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

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

   340 

   341   hr->set_containing_set(NULL);

   342   _humongous_regions_removed++;

   343 

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

   345   prepare_for_compaction(hr, end);

   346   dummy_free_list.remove_all();

   347 }

   348 

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

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

   351   // initialize the CompactPoint.

   352   if (!is_cp_initialized()) {

   353     _cp.space = hr;

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

   355   }

   356   prepare_for_compaction_work(&_cp, hr, end);

   357 }

   358 

   359 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,

   360                                                           HeapRegion* hr,

   361                                                           HeapWord* end) {

   362   hr->prepare_for_compaction(cp);

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

   364   // compaction.

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

   366 }

   367 

   368 void G1PrepareCompactClosure::update_sets() {

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

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

   371   _g1h->remove_from_old_sets(0, _humongous_regions_removed);

   372 }

   373 

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

   375   if (hr->is_humongous()) {

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

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

   378       obj->forward_to(obj);

   379     }

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

   381       free_humongous_region(hr);

   382     }

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

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

   385   }

   386   return false;

   387 }