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/g1Log.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.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.inline.hpp"

    50 #include "runtime/biasedLocking.hpp"

    51 #include "runtime/fprofiler.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 

    64 #ifdef ASSERT

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

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

    67   }

    68 #endif

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

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

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

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

    73 

    74   GenMarkSweep::_ref_processor = rp;

    75   rp->setup_policy(clear_all_softrefs);

    76 

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

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

    79   CodeCache::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   CodeCache::gc_epilogue();

   105   JvmtiExport::gc_epilogue();

   106 

   107   // refs processing: clean slate

   108   GenMarkSweep::_ref_processor = NULL;

   109 }

   110 

   111 

   112 void G1MarkSweep::allocate_stacks() {

   113   GenMarkSweep::_preserved_count_max = 0;

   114   GenMarkSweep::_preserved_marks = NULL;

   115   GenMarkSweep::_preserved_count = 0;

   116 }

   117 

   118 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,

   119                                     bool clear_all_softrefs) {

   120   // Recursively traverse all live objects and mark them

   121   GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   122 

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

   124 

   125   // Need cleared claim bits for the roots processing

   126   ClassLoaderDataGraph::clear_claimed_marks();

   127 

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

   129   {

   130     G1RootProcessor root_processor(g1h);

   131     root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,

   132                                         &GenMarkSweep::follow_cld_closure,

   133                                         &follow_code_closure);

   134   }

   135 

   136   // Process reference objects found during marking

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

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

   139 

   140   rp->setup_policy(clear_all_softrefs);

   141   const ReferenceProcessorStats& stats =

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

   143                                       &GenMarkSweep::keep_alive,

   144                                       &GenMarkSweep::follow_stack_closure,

   145                                       NULL,

   146                                       gc_timer(),

   147                                       gc_tracer()->gc_id());

   148   gc_tracer()->report_gc_reference_stats(stats);

   149 

   150 

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

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

   153 

   154   // Unload classes and purge the SystemDictionary.

   155   bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);

   156 

   157   // Unload nmethods.

   158   CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);

   159 

   160   // Prune dead klasses from subklass/sibling/implementor lists.

   161   Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);

   162 

   163   // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.

   164   g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);

   165 

   166   if (VerifyDuringGC) {

   167     HandleMark hm;  // handle scope

   168     COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);

   169     g1h->prepare_for_verify();

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

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

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

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

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

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

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

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

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

   179     // objects.

   180     if (!VerifySilently) {

   181       gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");

   182     }

   183     g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);

   184     if (!VerifySilently) {

   185       gclog_or_tty->print_cr("]");

   186     }

   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 tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   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 {

   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 tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   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);

   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         hr->reset_during_compaction();

   277       }

   278     } else {

   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 tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());

   295 

   296   G1SpaceCompactClosure blk;

   297   g1h->heap_region_iterate(&blk);

   298 

   299 }

   300 

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

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

   303   g1h->heap_region_iterate(blk);

   304   blk->update_sets();

   305 }

   306 

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

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

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

   310 

   311   assert(hr->is_starts_humongous(),

   312          "Only the start of a humongous region should be freed.");

   313 

   314   hr->set_containing_set(NULL);

   315   _humongous_regions_removed.increment(1u, hr->capacity());

   316 

   317   _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);

   318   prepare_for_compaction(hr, end);

   319   dummy_free_list.remove_all();

   320 }

   321 

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

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

   324   // initialize the CompactPoint.

   325   if (!is_cp_initialized()) {

   326     _cp.space = hr;

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

   328   }

   329   prepare_for_compaction_work(&_cp, hr, end);

   330 }

   331 

   332 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,

   333                                                           HeapRegion* hr,

   334                                                           HeapWord* end) {

   335   hr->prepare_for_compaction(cp);

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

   337   // compaction.

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

   339 }

   340 

   341 void G1PrepareCompactClosure::update_sets() {

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

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

   344   HeapRegionSetCount empty_set;

   345   _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);

   346 }

   347 

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

   349   if (hr->is_humongous()) {

   350     if (hr->is_starts_humongous()) {

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

   352       if (obj->is_gc_marked()) {

   353         obj->forward_to(obj);

   354       } else  {

   355         free_humongous_region(hr);

   356       }

   357     } else {

   358       assert(hr->is_continues_humongous(), "Invalid humongous.");

   359     }

   360   } else {

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

   362   }

   363   return false;

   364 }