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 /*

  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 #include "precompiled.hpp"

 #include "classfile/javaClasses.hpp"

 #include "classfile/symbolTable.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "code/codeCache.hpp"

 #include "code/icBuffer.hpp"

 #include "gc_interface/collectedHeap.inline.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "memory/genMarkSweep.hpp"

 #include "memory/genOopClosures.inline.hpp"

 #include "memory/generation.inline.hpp"

 #include "memory/modRefBarrierSet.hpp"

 #include "memory/referencePolicy.hpp"

 #include "memory/space.hpp"

 #include "oops/instanceRefKlass.hpp"

 #include "oops/oop.inline.hpp"

 #include "prims/jvmtiExport.hpp"

 #include "runtime/fprofiler.hpp"

 #include "runtime/handles.inline.hpp"

 #include "runtime/synchronizer.hpp"

 #include "runtime/vmThread.hpp"

 #include "utilities/copy.hpp"

 #include "utilities/events.hpp"

 #ifdef TARGET_OS_FAMILY_linux

 # include "thread_linux.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_solaris

 # include "thread_solaris.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_windows

 # include "thread_windows.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_bsd

 # include "thread_bsd.inline.hpp"

 #endif

 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,

   bool clear_all_softrefs) {

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

   GenCollectedHeap* gch = GenCollectedHeap::heap();

 #ifdef ASSERT

   if (gch->collector_policy()->should_clear_all_soft_refs()) {

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

   }

 #endif

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

   assert(ref_processor() == NULL, "no stomping");

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

   _ref_processor = rp;

   rp->setup_policy(clear_all_softrefs);

   TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);

   // When collecting the permanent generation methodOops may be moving,

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

   CodeCache::gc_prologue();

   Threads::gc_prologue();

   // Increment the invocation count for the permanent generation, since it is

   // implicitly collected whenever we do a full mark sweep collection.

   gch->perm_gen()->stat_record()->invocations++;

   // Capture heap size before collection for printing.

   size_t gch_prev_used = gch->used();

   // Some of the card table updates below assume that the perm gen is

   // also being collected.

   assert(level == gch->n_gens() - 1,

          "All generations are being collected, ergo perm gen too.");

   // Capture used regions for each generation that will be

   // subject to collection, so that card table adjustments can

   // be made intelligently (see clear / invalidate further below).

   gch->save_used_regions(level, true /* perm */);

   allocate_stacks();

   mark_sweep_phase1(level, clear_all_softrefs);

   mark_sweep_phase2();

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

   COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));

   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));

   mark_sweep_phase3(level);

   VALIDATE_MARK_SWEEP_ONLY(

     if (ValidateMarkSweep) {

       guarantee(_root_refs_stack->length() == 0, "should be empty by now");

     }

   )

   mark_sweep_phase4();

   VALIDATE_MARK_SWEEP_ONLY(

     if (ValidateMarkSweep) {

       guarantee(_live_oops->length() == _live_oops_moved_to->length(),

                 "should be the same size");

     }

   )

   restore_marks();

   // Set saved marks for allocation profiler (and other things? -- dld)

   // (Should this be in general part?)

   gch->save_marks();

   deallocate_stacks();

   // If compaction completely evacuated all generations younger than this

   // one, then we can clear the card table.  Otherwise, we must invalidate

   // it (consider all cards dirty).  In the future, we might consider doing

   // compaction within generations only, and doing card-table sliding.

   bool all_empty = true;

   for (int i = 0; all_empty && i < level; i++) {

     Generation* g = gch->get_gen(i);

     all_empty = all_empty && gch->get_gen(i)->used() == 0;

   }

   GenRemSet* rs = gch->rem_set();

   // Clear/invalidate below make use of the "prev_used_regions" saved earlier.

   if (all_empty) {

     // We've evacuated all generations below us.

     Generation* g = gch->get_gen(level);

     rs->clear_into_younger(g, true /* perm */);

   } else {

     // Invalidate the cards corresponding to the currently used

     // region and clear those corresponding to the evacuated region

     // of all generations just collected (i.e. level and younger).

     rs->invalidate_or_clear(gch->get_gen(level),

                             true /* younger */,

                             true /* perm */);

   }

   Threads::gc_epilogue();

   CodeCache::gc_epilogue();

   JvmtiExport::gc_epilogue();

   if (PrintGC && !PrintGCDetails) {

     gch->print_heap_change(gch_prev_used);

   }

   // refs processing: clean slate

   _ref_processor = NULL;

   // Update heap occupancy information which is used as

   // input to soft ref clearing policy at the next gc.

   Universe::update_heap_info_at_gc();

   // Update time of last gc for all generations we collected

   // (which curently is all the generations in the heap).

   // We need to use a monotonically non-deccreasing time in ms

   // or we will see time-warp warnings and os::javaTimeMillis()

   // does not guarantee monotonicity.

   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;

   gch->update_time_of_last_gc(now);

 }

 void GenMarkSweep::allocate_stacks() {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   // Scratch request on behalf of oldest generation; will do no

   // allocation.

   ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);

   // $$$ To cut a corner, we'll only use the first scratch block, and then

   // revert to malloc.

   if (scratch != NULL) {

     _preserved_count_max =

       scratch->num_words * HeapWordSize / sizeof(PreservedMark);

   } else {

     _preserved_count_max = 0;

   }

   _preserved_marks = (PreservedMark*)scratch;

   _preserved_count = 0;

 #ifdef VALIDATE_MARK_SWEEP

   if (ValidateMarkSweep) {

     _root_refs_stack    = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);

     _other_refs_stack   = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);

     _adjusted_pointers  = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);

     _live_oops          = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);

     _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);

     _live_oops_size     = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);

   }

   if (RecordMarkSweepCompaction) {

     if (_cur_gc_live_oops == NULL) {

       _cur_gc_live_oops           = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);

       _cur_gc_live_oops_moved_to  = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);

       _cur_gc_live_oops_size      = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);

       _last_gc_live_oops          = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);

       _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);

       _last_gc_live_oops_size     = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);

     } else {

       _cur_gc_live_oops->clear();

       _cur_gc_live_oops_moved_to->clear();

       _cur_gc_live_oops_size->clear();

     }

   }

 #endif

 }

 void GenMarkSweep::deallocate_stacks() {

   if (!UseG1GC) {

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     gch->release_scratch();

   }

   _preserved_mark_stack.clear(true);

   _preserved_oop_stack.clear(true);

   _marking_stack.clear();

   _objarray_stack.clear(true);

   _revisit_klass_stack.clear(true);

   _revisit_mdo_stack.clear(true);

 #ifdef VALIDATE_MARK_SWEEP

   if (ValidateMarkSweep) {

     delete _root_refs_stack;

     delete _other_refs_stack;

     delete _adjusted_pointers;

     delete _live_oops;

     delete _live_oops_size;

     delete _live_oops_moved_to;

     _live_oops_index = 0;

     _live_oops_index_at_perm = 0;

   }

 #endif

 }

 void GenMarkSweep::mark_sweep_phase1(int level,

                                   bool clear_all_softrefs) {

   // Recursively traverse all live objects and mark them

   TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);

   trace(" 1");

   VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   // Because follow_root_closure is created statically, cannot

   // use OopsInGenClosure constructor which takes a generation,

   // as the Universe has not been created when the static constructors

   // are run.

   follow_root_closure.set_orig_generation(gch->get_gen(level));

   gch->gen_process_strong_roots(level,

                                 false, // Younger gens are not roots.

                                 true,  // activate StrongRootsScope

                                 true,  // Collecting permanent generation.

                                 SharedHeap::SO_SystemClasses,

                                 &follow_root_closure,

                                 true,   // walk code active on stacks

                                 &follow_root_closure);

   // Process reference objects found during marking

   {

     ref_processor()->setup_policy(clear_all_softrefs);

     ref_processor()->process_discovered_references(

       &is_alive, &keep_alive, &follow_stack_closure, NULL);

   }

   // Follow system dictionary roots and unload classes

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

   // Follow code cache roots

   CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);

   follow_stack(); // Flush marking stack

   // Update subklass/sibling/implementor links of live klasses

   follow_weak_klass_links();

   assert(_marking_stack.is_empty(), "just drained");

   // Visit memoized MDO's and clear any unmarked weak refs

   follow_mdo_weak_refs();

   assert(_marking_stack.is_empty(), "just drained");

   // Visit interned string tables and delete unmarked oops

   StringTable::unlink(&is_alive);

   // Clean up unreferenced symbols in symbol table.

   SymbolTable::unlink();

   assert(_marking_stack.is_empty(), "stack should be empty by now");

 }

 void GenMarkSweep::mark_sweep_phase2() {

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

   // It is imperative that we traverse perm_gen LAST. If dead space is

   // allowed a range of dead object may get overwritten by a dead int

   // array. If perm_gen is not traversed last a klassOop may get

   // overwritten. This is fine since it is dead, but if the class has dead

   // instances we have to skip them, and in order to find their size we

   // need the klassOop!

   //

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

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

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

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   Generation* pg = gch->perm_gen();

   TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);

   trace("2");

   VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));

   gch->prepare_for_compaction();

   VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);

   CompactPoint perm_cp(pg, NULL, NULL);

   pg->prepare_for_compaction(&perm_cp);

 }

 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {

 public:

   void do_generation(Generation* gen) {

     gen->adjust_pointers();

   }

 };

 void GenMarkSweep::mark_sweep_phase3(int level) {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   Generation* pg = gch->perm_gen();

   // Adjust the pointers to reflect the new locations

   TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);

   trace("3");

   VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));

   // Needs to be done before the system dictionary is adjusted.

   pg->pre_adjust_pointers();

   // Because the two closures below are created statically, cannot

   // use OopsInGenClosure constructor which takes a generation,

   // as the Universe has not been created when the static constructors

   // are run.

   adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));

   adjust_pointer_closure.set_orig_generation(gch->get_gen(level));

   gch->gen_process_strong_roots(level,

                                 false, // Younger gens are not roots.

                                 true,  // activate StrongRootsScope

                                 true,  // Collecting permanent generation.

                                 SharedHeap::SO_AllClasses,

                                 &adjust_root_pointer_closure,

                                 false, // do not walk code

                                 &adjust_root_pointer_closure);

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

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

   CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,

                                                    /*do_marking=*/ false);

   gch->gen_process_weak_roots(&adjust_root_pointer_closure,

                               &adjust_code_pointer_closure,

                               &adjust_pointer_closure);

   adjust_marks();

   GenAdjustPointersClosure blk;

   gch->generation_iterate(&blk, true);

   pg->adjust_pointers();

 }

 class GenCompactClosure: public GenCollectedHeap::GenClosure {

 public:

   void do_generation(Generation* gen) {

     gen->compact();

   }

 };

 void GenMarkSweep::mark_sweep_phase4() {

   // All pointers are now adjusted, move objects accordingly

   // It is imperative that we traverse perm_gen first in phase4. All

   // classes must be allocated earlier than their instances, and traversing

   // perm_gen first makes sure that all klassOops have moved to their new

   // location before any instance does a dispatch through it's klass!

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

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

   // here (perm_gen first rather than last), so we tell the validate code

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

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   Generation* pg = gch->perm_gen();

   TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);

   trace("4");

   VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));

   pg->compact();

   VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));

   GenCompactClosure blk;

   gch->generation_iterate(&blk, true);

   VALIDATE_MARK_SWEEP_ONLY(compaction_complete());

   pg->post_compact(); // Shared spaces verification.

 }