jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/concurrentMark.hpp@64bf7c8270cb (annotated)

src/share/vm/gc_implementation/g1/concurrentMark.hpp@64bf7c8270cb (annotated)

src/share/vm/gc_implementation/g1/concurrentMark.hpp

Mon, 12 Mar 2012 14:59:00 -0700

author: johnc
date: Mon, 12 Mar 2012 14:59:00 -0700
changeset 3666: 64bf7c8270cb
parent 3464: eff609af17d7
child 3691: 2a0172480595
permissions: -rw-r--r--

7147724: G1: hang in SurrogateLockerThread::manipulatePLL
Summary: Attempting to initiate a marking cycle when allocating a humongous object can, if a marking cycle is successfully initiated by another thread, result in the allocating thread spinning until the marking cycle is complete. Eliminate a deadlock between the main ConcurrentMarkThread, the SurrogateLocker thread, the VM thread, and a mutator thread waiting on the SecondaryFreeList_lock (while free regions are going to become available) by not manipulating the pending list lock during the prologue and epilogue of the cleanup pause.
Reviewed-by: brutisso, jcoomes, tonyp

 /*
  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * 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
  * or visit www.oracle.com if you need additional information or have any
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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
 #include "gc_implementation/g1/heapRegionSets.hpp"
 #include "utilities/taskqueue.hpp"
 class G1CollectedHeap;
 class CMTask;
 typedef GenericTaskQueue<oop>            CMTaskQueue;
 typedef GenericTaskQueueSet<CMTaskQueue> CMTaskQueueSet;
 // Closure used by CM during concurrent reference discovery
 // and reference processing (during remarking) to determine
 // if a particular object is alive. It is primarily used
 // to determine if referents of discovered reference objects
 // are alive. An instance is also embedded into the
 // reference processor as the _is_alive_non_header field
 class G1CMIsAliveClosure: public BoolObjectClosure {
   G1CollectedHeap* _g1;
  public:
   G1CMIsAliveClosure(G1CollectedHeap* g1) :
     _g1(g1)
   {}
   void do_object(oop obj) {
     ShouldNotCallThis();
   }
   bool do_object_b(oop obj);
 };
 // A generic CM bit map.  This is essentially a wrapper around the BitMap
 // class, with one bit per (1<<_shifter) HeapWords.
 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
  protected:
   HeapWord* _bmStartWord;      // base address of range covered by map
   size_t    _bmWordSize;       // map size (in #HeapWords covered)
   const int _shifter;          // map to char or bit
   VirtualSpace _virtual_space; // underlying the bit map
   BitMap    _bm;               // the bit map itself
  public:
   // constructor
   CMBitMapRO(ReservedSpace rs, int shifter);
   enum { do_yield = true };
   // inquiries
   HeapWord* startWord()   const { return _bmStartWord; }
   size_t    sizeInWords() const { return _bmWordSize;  }
   // the following is one past the last word in space
   HeapWord* endWord()     const { return _bmStartWord + _bmWordSize; }
   // read marks
   bool isMarked(HeapWord* addr) const {
     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
            "outside underlying space?");
     return _bm.at(heapWordToOffset(addr));
   }
   // iteration
   inline bool iterate(BitMapClosure* cl, MemRegion mr);
   inline bool iterate(BitMapClosure* cl);
   // Return the address corresponding to the next marked bit at or after
   // "addr", and before "limit", if "limit" is non-NULL.  If there is no
   // such bit, returns "limit" if that is non-NULL, or else "endWord()".
   HeapWord* getNextMarkedWordAddress(HeapWord* addr,
                                      HeapWord* limit = NULL) const;
   // Return the address corresponding to the next unmarked bit at or after
   // "addr", and before "limit", if "limit" is non-NULL.  If there is no
   // such bit, returns "limit" if that is non-NULL, or else "endWord()".
   HeapWord* getNextUnmarkedWordAddress(HeapWord* addr,
                                        HeapWord* limit = NULL) const;
   // conversion utilities
   // XXX Fix these so that offsets are size_t's...
   HeapWord* offsetToHeapWord(size_t offset) const {
     return _bmStartWord + (offset << _shifter);
   }
   size_t heapWordToOffset(HeapWord* addr) const {
     return pointer_delta(addr, _bmStartWord) >> _shifter;
   }
   int heapWordDiffToOffsetDiff(size_t diff) const;
   HeapWord* nextWord(HeapWord* addr) {
     return offsetToHeapWord(heapWordToOffset(addr) + 1);
   }
   void mostly_disjoint_range_union(BitMap*   from_bitmap,
                                    size_t    from_start_index,
                                    HeapWord* to_start_word,
                                    size_t    word_num);
   // debugging
   NOT_PRODUCT(bool covers(ReservedSpace rs) const;)
 };
 class CMBitMap : public CMBitMapRO {
  public:
   // constructor
   CMBitMap(ReservedSpace rs, int shifter) :
     CMBitMapRO(rs, shifter) {}
   // write marks
   void mark(HeapWord* addr) {
     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
            "outside underlying space?");
     _bm.set_bit(heapWordToOffset(addr));
   }
   void clear(HeapWord* addr) {
     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
            "outside underlying space?");
     _bm.clear_bit(heapWordToOffset(addr));
   }
   bool parMark(HeapWord* addr) {
     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
            "outside underlying space?");
     return _bm.par_set_bit(heapWordToOffset(addr));
   }
   bool parClear(HeapWord* addr) {
     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
            "outside underlying space?");
     return _bm.par_clear_bit(heapWordToOffset(addr));
   }
   void markRange(MemRegion mr);
   void clearAll();
   void clearRange(MemRegion mr);
   // Starting at the bit corresponding to "addr" (inclusive), find the next
   // "1" bit, if any.  This bit starts some run of consecutive "1"'s; find
   // the end of this run (stopping at "end_addr").  Return the MemRegion
   // covering from the start of the region corresponding to the first bit
   // of the run to the end of the region corresponding to the last bit of
   // the run.  If there is no "1" bit at or after "addr", return an empty
   // MemRegion.
   MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
 };
 // Represents a marking stack used by the CM collector.
 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
   ConcurrentMark* _cm;
   oop*   _base;        // bottom of stack
   jint   _index;       // one more than last occupied index
   jint   _capacity;    // max #elements
   jint   _saved_index; // value of _index saved at start of GC
   NOT_PRODUCT(jint _max_depth;)  // max depth plumbed during run
   bool   _overflow;
   DEBUG_ONLY(bool _drain_in_progress;)
   DEBUG_ONLY(bool _drain_in_progress_yields;)
  public:
   CMMarkStack(ConcurrentMark* cm);
   ~CMMarkStack();
   void allocate(size_t size);
   oop pop() {
     if (!isEmpty()) {
       return _base[--_index] ;
     }
     return NULL;
   }
   // If overflow happens, don't do the push, and record the overflow.
   // *Requires* that "ptr" is already marked.
   void push(oop ptr) {
     if (isFull()) {
       // Record overflow.
       _overflow = true;
       return;
     } else {
       _base[_index++] = ptr;
       NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
     }
   }
   // Non-block impl.  Note: concurrency is allowed only with other
   // "par_push" operations, not with "pop" or "drain".  We would need
   // parallel versions of them if such concurrency was desired.
   void par_push(oop ptr);
   // Pushes the first "n" elements of "ptr_arr" on the stack.
   // Non-block impl.  Note: concurrency is allowed only with other
   // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
   void par_adjoin_arr(oop* ptr_arr, int n);
   // Pushes the first "n" elements of "ptr_arr" on the stack.
   // Locking impl: concurrency is allowed only with
   // "par_push_arr" and/or "par_pop_arr" operations, which use the same
   // locking strategy.
   void par_push_arr(oop* ptr_arr, int n);
   // If returns false, the array was empty.  Otherwise, removes up to "max"
   // elements from the stack, and transfers them to "ptr_arr" in an
   // unspecified order.  The actual number transferred is given in "n" ("n
   // == 0" is deliberately redundant with the return value.)  Locking impl:
   // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
   // operations, which use the same locking strategy.
   bool par_pop_arr(oop* ptr_arr, int max, int* n);
   // Drain the mark stack, applying the given closure to all fields of
   // objects on the stack.  (That is, continue until the stack is empty,
   // even if closure applications add entries to the stack.)  The "bm"
   // argument, if non-null, may be used to verify that only marked objects
   // are on the mark stack.  If "yield_after" is "true", then the
   // concurrent marker performing the drain offers to yield after
   // processing each object.  If a yield occurs, stops the drain operation
   // and returns false.  Otherwise, returns true.
   template<class OopClosureClass>
   bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
   bool isEmpty()    { return _index == 0; }
   bool isFull()     { return _index == _capacity; }
   int maxElems()    { return _capacity; }
   bool overflow() { return _overflow; }
   void clear_overflow() { _overflow = false; }
   int  size() { return _index; }
   void setEmpty()   { _index = 0; clear_overflow(); }
   // Record the current index.
   void note_start_of_gc();
   // Make sure that we have not added any entries to the stack during GC.
   void note_end_of_gc();
   // iterate over the oops in the mark stack, up to the bound recorded via
   // the call above.
   void oops_do(OopClosure* f);
 };
 class CMRegionStack VALUE_OBJ_CLASS_SPEC {
   MemRegion* _base;
   jint _capacity;
   jint _index;
   jint _oops_do_bound;
   bool _overflow;
 public:
   CMRegionStack();
   ~CMRegionStack();
   void allocate(size_t size);
   // This is lock-free; assumes that it will only be called in parallel
   // with other "push" operations (no pops).
   void push_lock_free(MemRegion mr);
   // Lock-free; assumes that it will only be called in parallel
   // with other "pop" operations (no pushes).
   MemRegion pop_lock_free();
 #if 0
   // The routines that manipulate the region stack with a lock are
   // not currently used. They should be retained, however, as a
   // diagnostic aid.
   // These two are the implementations that use a lock. They can be
   // called concurrently with each other but they should not be called
   // concurrently with the lock-free versions (push() / pop()).
   void push_with_lock(MemRegion mr);
   MemRegion pop_with_lock();
 #endif
   bool isEmpty()    { return _index == 0; }
   bool isFull()     { return _index == _capacity; }
   bool overflow() { return _overflow; }
   void clear_overflow() { _overflow = false; }
   int  size() { return _index; }
   // It iterates over the entries in the region stack and it
   // invalidates (i.e. assigns MemRegion()) the ones that point to
   // regions in the collection set.
   bool invalidate_entries_into_cset();
   // This gives an upper bound up to which the iteration in
   // invalidate_entries_into_cset() will reach. This prevents
   // newly-added entries to be unnecessarily scanned.
   void set_oops_do_bound() {
     _oops_do_bound = _index;
   }
   void setEmpty()   { _index = 0; clear_overflow(); }
 };
 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
 private:
 #ifndef PRODUCT
   uintx _num_remaining;
   bool _force;
 #endif // !defined(PRODUCT)
 public:
   void init() PRODUCT_RETURN;
   void update() PRODUCT_RETURN;
   bool should_force() PRODUCT_RETURN_( return false; );
 };
 // this will enable a variety of different statistics per GC task
 #define _MARKING_STATS_       0
 // this will enable the higher verbose levels
 #define _MARKING_VERBOSE_     0
 #if _MARKING_STATS_
 #define statsOnly(statement)  \
 do {                          \
   statement ;                 \
 } while (0)
 #else // _MARKING_STATS_
 #define statsOnly(statement)  \
 do {                          \
 } while (0)
 #endif // _MARKING_STATS_
 typedef enum {
   no_verbose  = 0,   // verbose turned off
   stats_verbose,     // only prints stats at the end of marking
   low_verbose,       // low verbose, mostly per region and per major event
   medium_verbose,    // a bit more detailed than low
   high_verbose       // per object verbose
 } CMVerboseLevel;
 class YoungList;
 // Root Regions are regions that are not empty at the beginning of a
 // marking cycle and which we might collect during an evacuation pause
 // while the cycle is active. Given that, during evacuation pauses, we
 // do not copy objects that are explicitly marked, what we have to do
 // for the root regions is to scan them and mark all objects reachable
 // from them. According to the SATB assumptions, we only need to visit
 // each object once during marking. So, as long as we finish this scan
 // before the next evacuation pause, we can copy the objects from the
 // root regions without having to mark them or do anything else to them.
 //
 // Currently, we only support root region scanning once (at the start
 // of the marking cycle) and the root regions are all the survivor
 // regions populated during the initial-mark pause.
 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
 private:
   YoungList*           _young_list;
   ConcurrentMark*      _cm;
   volatile bool        _scan_in_progress;
   volatile bool        _should_abort;
   HeapRegion* volatile _next_survivor;
 public:
   CMRootRegions();
   // We actually do most of the initialization in this method.
   void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
   // Reset the claiming / scanning of the root regions.
   void prepare_for_scan();
   // Forces get_next() to return NULL so that the iteration aborts early.
   void abort() { _should_abort = true; }
   // Return true if the CM thread are actively scanning root regions,
   // false otherwise.
   bool scan_in_progress() { return _scan_in_progress; }
   // Claim the next root region to scan atomically, or return NULL if
   // all have been claimed.
   HeapRegion* claim_next();
   // Flag that we're done with root region scanning and notify anyone
   // who's waiting on it. If aborted is false, assume that all regions
   // have been claimed.
   void scan_finished();
   // If CM threads are still scanning root regions, wait until they
   // are done. Return true if we had to wait, false otherwise.
   bool wait_until_scan_finished();
 };
 class ConcurrentMarkThread;
 class ConcurrentMark : public CHeapObj {
   friend class ConcurrentMarkThread;
   friend class CMTask;
   friend class CMBitMapClosure;
   friend class CSetMarkOopClosure;
   friend class CMGlobalObjectClosure;
   friend class CMRemarkTask;
   friend class CMConcurrentMarkingTask;
   friend class G1ParNoteEndTask;
   friend class CalcLiveObjectsClosure;
   friend class G1CMRefProcTaskProxy;
   friend class G1CMRefProcTaskExecutor;
   friend class G1CMParKeepAliveAndDrainClosure;
   friend class G1CMParDrainMarkingStackClosure;
 protected:
   ConcurrentMarkThread* _cmThread;   // the thread doing the work
   G1CollectedHeap*      _g1h;        // the heap.
   uint                  _parallel_marking_threads; // the number of marking
                                                    // threads we're use
   uint                  _max_parallel_marking_threads; // max number of marking
                                                    // threads we'll ever use
   double                _sleep_factor; // how much we have to sleep, with
                                        // respect to the work we just did, to
                                        // meet the marking overhead goal
   double                _marking_task_overhead; // marking target overhead for
                                                 // a single task
   // same as the two above, but for the cleanup task
   double                _cleanup_sleep_factor;
   double                _cleanup_task_overhead;
   FreeRegionList        _cleanup_list;
   // Concurrent marking support structures
   CMBitMap                _markBitMap1;
   CMBitMap                _markBitMap2;
   CMBitMapRO*             _prevMarkBitMap; // completed mark bitmap
   CMBitMap*               _nextMarkBitMap; // under-construction mark bitmap
   bool                    _at_least_one_mark_complete;
   BitMap                  _region_bm;
   BitMap                  _card_bm;
   // Heap bounds
   HeapWord*               _heap_start;
   HeapWord*               _heap_end;
   // Root region tracking and claiming.
   CMRootRegions           _root_regions;
   // For gray objects
   CMMarkStack             _markStack; // Grey objects behind global finger.
   CMRegionStack           _regionStack; // Grey regions behind global finger.
   HeapWord* volatile      _finger;  // the global finger, region aligned,
                                     // always points to the end of the
                                     // last claimed region
   // marking tasks
   uint                    _max_task_num; // maximum task number
   uint                    _active_tasks; // task num currently active
   CMTask**                _tasks;        // task queue array (max_task_num len)
   CMTaskQueueSet*         _task_queues;  // task queue set
   ParallelTaskTerminator  _terminator;   // for termination
   // Two sync barriers that are used to synchronise tasks when an
   // overflow occurs. The algorithm is the following. All tasks enter
   // the first one to ensure that they have all stopped manipulating
   // the global data structures. After they exit it, they re-initialise
   // their data structures and task 0 re-initialises the global data
   // structures. Then, they enter the second sync barrier. This
   // ensure, that no task starts doing work before all data
   // structures (local and global) have been re-initialised. When they
   // exit it, they are free to start working again.
   WorkGangBarrierSync     _first_overflow_barrier_sync;
   WorkGangBarrierSync     _second_overflow_barrier_sync;
   // this is set by any task, when an overflow on the global data
   // structures is detected.
   volatile bool           _has_overflown;
   // true: marking is concurrent, false: we're in remark
   volatile bool           _concurrent;
   // set at the end of a Full GC so that marking aborts
   volatile bool           _has_aborted;
   // used when remark aborts due to an overflow to indicate that
   // another concurrent marking phase should start
   volatile bool           _restart_for_overflow;
   // This is true from the very start of concurrent marking until the
   // point when all the tasks complete their work. It is really used
   // to determine the points between the end of concurrent marking and
   // time of remark.
   volatile bool           _concurrent_marking_in_progress;
   // verbose level
   CMVerboseLevel          _verbose_level;
   // These two fields are used to implement the optimisation that
   // avoids pushing objects on the global/region stack if there are
   // no collection set regions above the lowest finger.
   // This is the lowest finger (among the global and local fingers),
   // which is calculated before a new collection set is chosen.
   HeapWord* _min_finger;
   // If this flag is true, objects/regions that are marked below the
   // finger should be pushed on the stack(s). If this is flag is
   // false, it is safe not to push them on the stack(s).
   bool      _should_gray_objects;
   // All of these times are in ms.
   NumberSeq _init_times;
   NumberSeq _remark_times;
   NumberSeq   _remark_mark_times;
   NumberSeq   _remark_weak_ref_times;
   NumberSeq _cleanup_times;
   double    _total_counting_time;
   double    _total_rs_scrub_time;
   double*   _accum_task_vtime;   // accumulated task vtime
   FlexibleWorkGang* _parallel_workers;
   ForceOverflowSettings _force_overflow_conc;
   ForceOverflowSettings _force_overflow_stw;
   void weakRefsWork(bool clear_all_soft_refs);
   void swapMarkBitMaps();
   // It resets the global marking data structures, as well as the
   // task local ones; should be called during initial mark.
   void reset();
   // It resets all the marking data structures.
   void clear_marking_state(bool clear_overflow = true);
   // It should be called to indicate which phase we're in (concurrent
   // mark or remark) and how many threads are currently active.
   void set_phase(uint active_tasks, bool concurrent);
   // We do this after we're done with marking so that the marking data
   // structures are initialised to a sensible and predictable state.
   void set_non_marking_state();
   // prints all gathered CM-related statistics
   void print_stats();
   bool cleanup_list_is_empty() {
     return _cleanup_list.is_empty();
   }
   // accessor methods
   uint parallel_marking_threads() { return _parallel_marking_threads; }
   uint max_parallel_marking_threads() { return _max_parallel_marking_threads;}
   double sleep_factor()             { return _sleep_factor; }
   double marking_task_overhead()    { return _marking_task_overhead;}
   double cleanup_sleep_factor()     { return _cleanup_sleep_factor; }
   double cleanup_task_overhead()    { return _cleanup_task_overhead;}
   HeapWord*               finger()        { return _finger;   }
   bool                    concurrent()    { return _concurrent; }
   uint                    active_tasks()  { return _active_tasks; }
   ParallelTaskTerminator* terminator()    { return &_terminator; }
   // It claims the next available region to be scanned by a marking
   // task. It might return NULL if the next region is empty or we have
   // run out of regions. In the latter case, out_of_regions()
   // determines whether we've really run out of regions or the task
   // should call claim_region() again.  This might seem a bit
   // awkward. Originally, the code was written so that claim_region()
   // either successfully returned with a non-empty region or there
   // were no more regions to be claimed. The problem with this was
   // that, in certain circumstances, it iterated over large chunks of
   // the heap finding only empty regions and, while it was working, it
   // was preventing the calling task to call its regular clock
   // method. So, this way, each task will spend very little time in
   // claim_region() and is allowed to call the regular clock method
   // frequently.
   HeapRegion* claim_region(int task);
   // It determines whether we've run out of regions to scan.
   bool        out_of_regions() { return _finger == _heap_end; }
   // Returns the task with the given id
   CMTask* task(int id) {
     assert(0 <= id && id < (int) _active_tasks,
            "task id not within active bounds");
     return _tasks[id];
   }
   // Returns the task queue with the given id
   CMTaskQueue* task_queue(int id) {
     assert(0 <= id && id < (int) _active_tasks,
            "task queue id not within active bounds");
     return (CMTaskQueue*) _task_queues->queue(id);
   }
   // Returns the task queue set
   CMTaskQueueSet* task_queues()  { return _task_queues; }
   // Access / manipulation of the overflow flag which is set to
   // indicate that the global stack or region stack has overflown
   bool has_overflown()           { return _has_overflown; }
   void set_has_overflown()       { _has_overflown = true; }
   void clear_has_overflown()     { _has_overflown = false; }
   bool restart_for_overflow()    { return _restart_for_overflow; }
   bool has_aborted()             { return _has_aborted; }
   // Methods to enter the two overflow sync barriers
   void enter_first_sync_barrier(int task_num);
   void enter_second_sync_barrier(int task_num);
   ForceOverflowSettings* force_overflow_conc() {
     return &_force_overflow_conc;
   }
   ForceOverflowSettings* force_overflow_stw() {
     return &_force_overflow_stw;
   }
   ForceOverflowSettings* force_overflow() {
     if (concurrent()) {
       return force_overflow_conc();
     } else {
       return force_overflow_stw();
     }
   }
   // Live Data Counting data structures...
   // These data structures are initialized at the start of
   // marking. They are written to while marking is active.
   // They are aggregated during remark; the aggregated values
   // are then used to populate the _region_bm, _card_bm, and
   // the total live bytes, which are then subsequently updated
   // during cleanup.
   // An array of bitmaps (one bit map per task). Each bitmap
   // is used to record the cards spanned by the live objects
   // marked by that task/worker.
   BitMap*  _count_card_bitmaps;
   // Used to record the number of marked live bytes
   // (for each region, by worker thread).
   size_t** _count_marked_bytes;
   // Card index of the bottom of the G1 heap. Used for biasing indices into
   // the card bitmaps.
   intptr_t _heap_bottom_card_num;
 public:
   // Manipulation of the global mark stack.
   // Notice that the first mark_stack_push is CAS-based, whereas the
   // two below are Mutex-based. This is OK since the first one is only
   // called during evacuation pauses and doesn't compete with the
   // other two (which are called by the marking tasks during
   // concurrent marking or remark).
   bool mark_stack_push(oop p) {
     _markStack.par_push(p);
     if (_markStack.overflow()) {
       set_has_overflown();
       return false;
     }
     return true;
   }
   bool mark_stack_push(oop* arr, int n) {
     _markStack.par_push_arr(arr, n);
     if (_markStack.overflow()) {
       set_has_overflown();
       return false;
     }
     return true;
   }
   void mark_stack_pop(oop* arr, int max, int* n) {
     _markStack.par_pop_arr(arr, max, n);
   }
   size_t mark_stack_size()                { return _markStack.size(); }
   size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
   bool mark_stack_overflow()              { return _markStack.overflow(); }
   bool mark_stack_empty()                 { return _markStack.isEmpty(); }
   // (Lock-free) Manipulation of the region stack
   bool region_stack_push_lock_free(MemRegion mr) {
     // Currently we only call the lock-free version during evacuation
     // pauses.
     assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");
     _regionStack.push_lock_free(mr);
     if (_regionStack.overflow()) {
       set_has_overflown();
       return false;
     }
     return true;
   }
   // Lock-free version of region-stack pop. Should only be
   // called in tandem with other lock-free pops.
   MemRegion region_stack_pop_lock_free() {
     return _regionStack.pop_lock_free();
   }
 #if 0
   // The routines that manipulate the region stack with a lock are
   // not currently used. They should be retained, however, as a
   // diagnostic aid.
   bool region_stack_push_with_lock(MemRegion mr) {
     // Currently we only call the lock-based version during either
     // concurrent marking or remark.
     assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(),
            "if we are at a safepoint it should be the remark safepoint");
     _regionStack.push_with_lock(mr);
     if (_regionStack.overflow()) {
       set_has_overflown();
       return false;
     }
     return true;
   }
   MemRegion region_stack_pop_with_lock() {
     // Currently we only call the lock-based version during either
     // concurrent marking or remark.
     assert(!SafepointSynchronize::is_at_safepoint() || !concurrent(),
            "if we are at a safepoint it should be the remark safepoint");
     return _regionStack.pop_with_lock();
   }
 #endif
   int region_stack_size()               { return _regionStack.size(); }
   bool region_stack_overflow()          { return _regionStack.overflow(); }
   bool region_stack_empty()             { return _regionStack.isEmpty(); }
   // Iterate over any regions that were aborted while draining the
   // region stack (any such regions are saved in the corresponding
   // CMTask) and invalidate (i.e. assign to the empty MemRegion())
   // any regions that point into the collection set.
   bool invalidate_aborted_regions_in_cset();
   // Returns true if there are any aborted memory regions.
   bool has_aborted_regions();
   CMRootRegions* root_regions() { return &_root_regions; }
   bool concurrent_marking_in_progress() {
     return _concurrent_marking_in_progress;
   }
   void set_concurrent_marking_in_progress() {
     _concurrent_marking_in_progress = true;
   }
   void clear_concurrent_marking_in_progress() {
     _concurrent_marking_in_progress = false;
   }
   void update_accum_task_vtime(int i, double vtime) {
     _accum_task_vtime[i] += vtime;
   }
   double all_task_accum_vtime() {
     double ret = 0.0;
     for (int i = 0; i < (int)_max_task_num; ++i)
       ret += _accum_task_vtime[i];
     return ret;
   }
   // Attempts to steal an object from the task queues of other tasks
   bool try_stealing(int task_num, int* hash_seed, oop& obj) {
     return _task_queues->steal(task_num, hash_seed, obj);
   }
   // It grays an object by first marking it. Then, if it's behind the
   // global finger, it also pushes it on the global stack.
   void deal_with_reference(oop obj);
   ConcurrentMark(ReservedSpace rs, int max_regions);
   ~ConcurrentMark();
   ConcurrentMarkThread* cmThread() { return _cmThread; }
   CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
   CMBitMap*   nextMarkBitMap() const { return _nextMarkBitMap; }
   // Returns the number of GC threads to be used in a concurrent
   // phase based on the number of GC threads being used in a STW
   // phase.
   uint scale_parallel_threads(uint n_par_threads);
   // Calculates the number of GC threads to be used in a concurrent phase.
   uint calc_parallel_marking_threads();
   // The following three are interaction between CM and
   // G1CollectedHeap
   // This notifies CM that a root during initial-mark needs to be
   // grayed. It is MT-safe. word_size is the size of the object in
   // words. It is passed explicitly as sometimes we cannot calculate
   // it from the given object because it might be in an inconsistent
   // state (e.g., in to-space and being copied). So the caller is
   // responsible for dealing with this issue (e.g., get the size from
   // the from-space image when the to-space image might be
   // inconsistent) and always passing the size. hr is the region that
   // contains the object and it's passed optionally from callers who
   // might already have it (no point in recalculating it).
   inline void grayRoot(oop obj, size_t word_size,
                        uint worker_id, HeapRegion* hr = NULL);
   // It's used during evacuation pauses to gray a region, if
   // necessary, and it's MT-safe. It assumes that the caller has
   // marked any objects on that region. If _should_gray_objects is
   // true and we're still doing concurrent marking, the region is
   // pushed on the region stack, if it is located below the global
   // finger, otherwise we do nothing.
   void grayRegionIfNecessary(MemRegion mr);
   // It's used during evacuation pauses to mark and, if necessary,
   // gray a single object and it's MT-safe. It assumes the caller did
   // not mark the object. If _should_gray_objects is true and we're
   // still doing concurrent marking, the objects is pushed on the
   // global stack, if it is located below the global finger, otherwise
   // we do nothing.
   void markAndGrayObjectIfNecessary(oop p);
   // It iterates over the heap and for each object it comes across it
   // will dump the contents of its reference fields, as well as
   // liveness information for the object and its referents. The dump
   // will be written to a file with the following name:
   // G1PrintReachableBaseFile + "." + str.
   // vo decides whether the prev (vo == UsePrevMarking), the next
   // (vo == UseNextMarking) marking information, or the mark word
   // (vo == UseMarkWord) will be used to determine the liveness of
   // each object / referent.
   // If all is true, all objects in the heap will be dumped, otherwise
   // only the live ones. In the dump the following symbols / breviations
   // are used:
   //   M : an explicitly live object (its bitmap bit is set)
   //   > : an implicitly live object (over tams)
   //   O : an object outside the G1 heap (typically: in the perm gen)
   //   NOT : a reference field whose referent is not live
   //   AND MARKED : indicates that an object is both explicitly and
   //   implicitly live (it should be one or the other, not both)
   void print_reachable(const char* str,
                        VerifyOption vo, bool all) PRODUCT_RETURN;
   // Clear the next marking bitmap (will be called concurrently).
   void clearNextBitmap();
   // These two do the work that needs to be done before and after the
   // initial root checkpoint. Since this checkpoint can be done at two
   // different points (i.e. an explicit pause or piggy-backed on a
   // young collection), then it's nice to be able to easily share the
   // pre/post code. It might be the case that we can put everything in
   // the post method. TP
   void checkpointRootsInitialPre();
   void checkpointRootsInitialPost();
   // Scan all the root regions and mark everything reachable from
   // them.
   void scanRootRegions();
   // Scan a single root region and mark everything reachable from it.
   void scanRootRegion(HeapRegion* hr, uint worker_id);
   // Do concurrent phase of marking, to a tentative transitive closure.
   void markFromRoots();
   // Process all unprocessed SATB buffers. It is called at the
   // beginning of an evacuation pause.
   void drainAllSATBBuffers();
   void checkpointRootsFinal(bool clear_all_soft_refs);
   void checkpointRootsFinalWork();
   void cleanup();
   void completeCleanup();
   // Mark in the previous bitmap.  NB: this is usually read-only, so use
   // this carefully!
   inline void markPrev(oop p);
   // Clears marks for all objects in the given range, for the prev,
   // next, or both bitmaps.  NB: the previous bitmap is usually
   // read-only, so use this carefully!
   void clearRangePrevBitmap(MemRegion mr);
   void clearRangeNextBitmap(MemRegion mr);
   void clearRangeBothBitmaps(MemRegion mr);
   // Notify data structures that a GC has started.
   void note_start_of_gc() {
     _markStack.note_start_of_gc();
   }
   // Notify data structures that a GC is finished.
   void note_end_of_gc() {
     _markStack.note_end_of_gc();
   }
   // Iterate over the oops in the mark stack and all local queues. It
   // also calls invalidate_entries_into_cset() on the region stack.
   void oops_do(OopClosure* f);
   // Verify that there are no CSet oops on the stacks (taskqueues /
   // global mark stack), enqueued SATB buffers, per-thread SATB
   // buffers, and fingers (global / per-task). The boolean parameters
   // decide which of the above data structures to verify. If marking
   // is not in progress, it's a no-op.
   void verify_no_cset_oops(bool verify_stacks,
                            bool verify_enqueued_buffers,
                            bool verify_thread_buffers,
                            bool verify_fingers) PRODUCT_RETURN;
   // It is called at the end of an evacuation pause during marking so
   // that CM is notified of where the new end of the heap is. It
   // doesn't do anything if concurrent_marking_in_progress() is false,
   // unless the force parameter is true.
   void update_g1_committed(bool force = false);
   void complete_marking_in_collection_set();
   // It indicates that a new collection set is being chosen.
   void newCSet();
   // It registers a collection set heap region with CM. This is used
   // to determine whether any heap regions are located above the finger.
   void registerCSetRegion(HeapRegion* hr);
   // Resets the region fields of any active CMTask whose region fields
   // are in the collection set (i.e. the region currently claimed by
   // the CMTask will be evacuated and may be used, subsequently, as
   // an alloc region). When this happens the region fields in the CMTask
   // are stale and, hence, should be cleared causing the worker thread
   // to claim a new region.
   void reset_active_task_region_fields_in_cset();
   // Registers the maximum region-end associated with a set of
   // regions with CM. Again this is used to determine whether any
   // heap regions are located above the finger.
   void register_collection_set_finger(HeapWord* max_finger) {
     // max_finger is the highest heap region end of the regions currently
     // contained in the collection set. If this value is larger than
     // _min_finger then we need to gray objects.
     // This routine is like registerCSetRegion but for an entire
     // collection of regions.
     if (max_finger > _min_finger) {
       _should_gray_objects = true;
     }
   }
   // Returns "true" if at least one mark has been completed.
   bool at_least_one_mark_complete() { return _at_least_one_mark_complete; }
   bool isMarked(oop p) const {
     assert(p != NULL && p->is_oop(), "expected an oop");
     HeapWord* addr = (HeapWord*)p;
     assert(addr >= _nextMarkBitMap->startWord() ||
            addr < _nextMarkBitMap->endWord(), "in a region");
     return _nextMarkBitMap->isMarked(addr);
   }
   inline bool not_yet_marked(oop p) const;
   // XXX Debug code
   bool containing_card_is_marked(void* p);
   bool containing_cards_are_marked(void* start, void* last);
   bool isPrevMarked(oop p) const {
     assert(p != NULL && p->is_oop(), "expected an oop");
     HeapWord* addr = (HeapWord*)p;
     assert(addr >= _prevMarkBitMap->startWord() ||
            addr < _prevMarkBitMap->endWord(), "in a region");
     return _prevMarkBitMap->isMarked(addr);
   }
   inline bool do_yield_check(uint worker_i = 0);
   inline bool should_yield();
   // Called to abort the marking cycle after a Full GC takes palce.
   void abort();
   // This prints the global/local fingers. It is used for debugging.
   NOT_PRODUCT(void print_finger();)
   void print_summary_info();
   void print_worker_threads_on(outputStream* st) const;
   // The following indicate whether a given verbose level has been
   // set. Notice that anything above stats is conditional to
   // _MARKING_VERBOSE_ having been set to 1
   bool verbose_stats() {
     return _verbose_level >= stats_verbose;
   }
   bool verbose_low() {
     return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
   }
   bool verbose_medium() {
     return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
   }
   bool verbose_high() {
     return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
   }
   // Counting data structure accessors
   // Returns the card number of the bottom of the G1 heap.
   // Used in biasing indices into accounting card bitmaps.
   intptr_t heap_bottom_card_num() const {
     return _heap_bottom_card_num;
   }
   // Returns the card bitmap for a given task or worker id.
   BitMap* count_card_bitmap_for(uint worker_id) {
     assert(0 <= worker_id && worker_id < _max_task_num, "oob");
     assert(_count_card_bitmaps != NULL, "uninitialized");
     BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
     assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
     return task_card_bm;
   }
   // Returns the array containing the marked bytes for each region,
   // for the given worker or task id.
   size_t* count_marked_bytes_array_for(uint worker_id) {
     assert(0 <= worker_id && worker_id < _max_task_num, "oob");
     assert(_count_marked_bytes != NULL, "uninitialized");
     size_t* marked_bytes_array = _count_marked_bytes[worker_id];
     assert(marked_bytes_array != NULL, "uninitialized");
     return marked_bytes_array;
   }
   // Returns the index in the liveness accounting card table bitmap
   // for the given address
   inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
   // Counts the size of the given memory region in the the given
   // marked_bytes array slot for the given HeapRegion.
   // Sets the bits in the given card bitmap that are associated with the
   // cards that are spanned by the memory region.
   inline void count_region(MemRegion mr, HeapRegion* hr,
                            size_t* marked_bytes_array,
                            BitMap* task_card_bm);
   // Counts the given memory region in the task/worker counting
   // data structures for the given worker id.
   inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
   // Counts the given memory region in the task/worker counting
   // data structures for the given worker id.
   inline void count_region(MemRegion mr, uint worker_id);
   // Counts the given object in the given task/worker counting
   // data structures.
   inline void count_object(oop obj, HeapRegion* hr,
                            size_t* marked_bytes_array,
                            BitMap* task_card_bm);
   // Counts the given object in the task/worker counting data
   // structures for the given worker id.
   inline void count_object(oop obj, HeapRegion* hr, uint worker_id);
   // Attempts to mark the given object and, if successful, counts
   // the object in the given task/worker counting structures.
   inline bool par_mark_and_count(oop obj, HeapRegion* hr,
                                  size_t* marked_bytes_array,
                                  BitMap* task_card_bm);
   // Attempts to mark the given object and, if successful, counts
   // the object in the task/worker counting structures for the
   // given worker id.
   inline bool par_mark_and_count(oop obj, size_t word_size,
                                  HeapRegion* hr, uint worker_id);
   // Attempts to mark the given object and, if successful, counts
   // the object in the task/worker counting structures for the
   // given worker id.
   inline bool par_mark_and_count(oop obj, HeapRegion* hr, uint worker_id);
   // Similar to the above routine but we don't know the heap region that
   // contains the object to be marked/counted, which this routine looks up.
   inline bool par_mark_and_count(oop obj, uint worker_id);
   // Similar to the above routine but there are times when we cannot
   // safely calculate the size of obj due to races and we, therefore,
   // pass the size in as a parameter. It is the caller's reponsibility
   // to ensure that the size passed in for obj is valid.
   inline bool par_mark_and_count(oop obj, size_t word_size, uint worker_id);
   // Unconditionally mark the given object, and unconditinally count
   // the object in the counting structures for worker id 0.
   // Should *not* be called from parallel code.
   inline bool mark_and_count(oop obj, HeapRegion* hr);
   // Similar to the above routine but we don't know the heap region that
   // contains the object to be marked/counted, which this routine looks up.
   // Should *not* be called from parallel code.
   inline bool mark_and_count(oop obj);
 protected:
   // Clear all the per-task bitmaps and arrays used to store the
   // counting data.
   void clear_all_count_data();
   // Aggregates the counting data for each worker/task
   // that was constructed while marking. Also sets
   // the amount of marked bytes for each region and
   // the top at concurrent mark count.
   void aggregate_count_data();
   // Verification routine
   void verify_count_data();
 };
 // A class representing a marking task.
 class CMTask : public TerminatorTerminator {
 private:
   enum PrivateConstants {
     // the regular clock call is called once the scanned words reaches
     // this limit
     words_scanned_period          = 12*1024,
     // the regular clock call is called once the number of visited
     // references reaches this limit
     refs_reached_period           = 384,
     // initial value for the hash seed, used in the work stealing code
     init_hash_seed                = 17,
     // how many entries will be transferred between global stack and
     // local queues
     global_stack_transfer_size    = 16
   };
   int                         _task_id;
   G1CollectedHeap*            _g1h;
   ConcurrentMark*             _cm;
   CMBitMap*                   _nextMarkBitMap;
   // the task queue of this task
   CMTaskQueue*                _task_queue;
 private:
   // the task queue set---needed for stealing
   CMTaskQueueSet*             _task_queues;
   // indicates whether the task has been claimed---this is only  for
   // debugging purposes
   bool                        _claimed;
   // number of calls to this task
   int                         _calls;
   // when the virtual timer reaches this time, the marking step should
   // exit
   double                      _time_target_ms;
   // the start time of the current marking step
   double                      _start_time_ms;
   // the oop closure used for iterations over oops
   G1CMOopClosure*             _cm_oop_closure;
   // the region this task is scanning, NULL if we're not scanning any
   HeapRegion*                 _curr_region;
   // the local finger of this task, NULL if we're not scanning a region
   HeapWord*                   _finger;
   // limit of the region this task is scanning, NULL if we're not scanning one
   HeapWord*                   _region_limit;
   // This is used only when we scan regions popped from the region
   // stack. It records what the last object on such a region we
   // scanned was. It is used to ensure that, if we abort region
   // iteration, we do not rescan the first part of the region. This
   // should be NULL when we're not scanning a region from the region
   // stack.
   HeapWord*                   _region_finger;
   // If we abort while scanning a region we record the remaining
   // unscanned portion and check this field when marking restarts.
   // This avoids having to push on the region stack while other
   // marking threads may still be popping regions.
   // If we were to push the unscanned portion directly to the
   // region stack then we would need to using locking versions
   // of the push and pop operations.
   MemRegion                   _aborted_region;
   // the number of words this task has scanned
   size_t                      _words_scanned;
   // When _words_scanned reaches this limit, the regular clock is
   // called. Notice that this might be decreased under certain
   // circumstances (i.e. when we believe that we did an expensive
   // operation).
   size_t                      _words_scanned_limit;
   // the initial value of _words_scanned_limit (i.e. what it was
   // before it was decreased).
   size_t                      _real_words_scanned_limit;
   // the number of references this task has visited
   size_t                      _refs_reached;
   // When _refs_reached reaches this limit, the regular clock is
   // called. Notice this this might be decreased under certain
   // circumstances (i.e. when we believe that we did an expensive
   // operation).
   size_t                      _refs_reached_limit;
   // the initial value of _refs_reached_limit (i.e. what it was before
   // it was decreased).
   size_t                      _real_refs_reached_limit;
   // used by the work stealing stuff
   int                         _hash_seed;
   // if this is true, then the task has aborted for some reason
   bool                        _has_aborted;
   // set when the task aborts because it has met its time quota
   bool                        _has_timed_out;
   // true when we're draining SATB buffers; this avoids the task
   // aborting due to SATB buffers being available (as we're already
   // dealing with them)
   bool                        _draining_satb_buffers;
   // number sequence of past step times
   NumberSeq                   _step_times_ms;
   // elapsed time of this task
   double                      _elapsed_time_ms;
   // termination time of this task
   double                      _termination_time_ms;
   // when this task got into the termination protocol
   double                      _termination_start_time_ms;
   // true when the task is during a concurrent phase, false when it is
   // in the remark phase (so, in the latter case, we do not have to
   // check all the things that we have to check during the concurrent
   // phase, i.e. SATB buffer availability...)
   bool                        _concurrent;
   TruncatedSeq                _marking_step_diffs_ms;
   // Counting data structures. Embedding the task's marked_bytes_array
   // and card bitmap into the actual task saves having to go through
   // the ConcurrentMark object.
   size_t*                     _marked_bytes_array;
   BitMap*                     _card_bm;
   // LOTS of statistics related with this task
 #if _MARKING_STATS_
   NumberSeq                   _all_clock_intervals_ms;
   double                      _interval_start_time_ms;
   int                         _aborted;
   int                         _aborted_overflow;
   int                         _aborted_cm_aborted;
   int                         _aborted_yield;
   int                         _aborted_timed_out;
   int                         _aborted_satb;
   int                         _aborted_termination;
   int                         _steal_attempts;
   int                         _steals;
   int                         _clock_due_to_marking;
   int                         _clock_due_to_scanning;
   int                         _local_pushes;
   int                         _local_pops;
   int                         _local_max_size;
   int                         _objs_scanned;
   int                         _global_pushes;
   int                         _global_pops;
   int                         _global_max_size;
   int                         _global_transfers_to;
   int                         _global_transfers_from;
   int                         _region_stack_pops;
   int                         _regions_claimed;
   int                         _objs_found_on_bitmap;
   int                         _satb_buffers_processed;
 #endif // _MARKING_STATS_
   // it updates the local fields after this task has claimed
   // a new region to scan
   void setup_for_region(HeapRegion* hr);
   // it brings up-to-date the limit of the region
   void update_region_limit();
   // called when either the words scanned or the refs visited limit
   // has been reached
   void reached_limit();
   // recalculates the words scanned and refs visited limits
   void recalculate_limits();
   // decreases the words scanned and refs visited limits when we reach
   // an expensive operation
   void decrease_limits();
   // it checks whether the words scanned or refs visited reached their
   // respective limit and calls reached_limit() if they have
   void check_limits() {
     if (_words_scanned >= _words_scanned_limit ||
         _refs_reached >= _refs_reached_limit) {
       reached_limit();
     }
   }
   // this is supposed to be called regularly during a marking step as
   // it checks a bunch of conditions that might cause the marking step
   // to abort
   void regular_clock_call();
   bool concurrent() { return _concurrent; }
 public:
   // It resets the task; it should be called right at the beginning of
   // a marking phase.
   void reset(CMBitMap* _nextMarkBitMap);
   // it clears all the fields that correspond to a claimed region.
   void clear_region_fields();
   void set_concurrent(bool concurrent) { _concurrent = concurrent; }
   // The main method of this class which performs a marking step
   // trying not to exceed the given duration. However, it might exit
   // prematurely, according to some conditions (i.e. SATB buffers are
   // available for processing).
   void do_marking_step(double target_ms, bool do_stealing, bool do_termination);
   // These two calls start and stop the timer
   void record_start_time() {
     _elapsed_time_ms = os::elapsedTime() * 1000.0;
   }
   void record_end_time() {
     _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
   }
   // returns the task ID
   int task_id() { return _task_id; }
   // From TerminatorTerminator. It determines whether this task should
   // exit the termination protocol after it's entered it.
   virtual bool should_exit_termination();
   // Resets the local region fields after a task has finished scanning a
   // region; or when they have become stale as a result of the region
   // being evacuated.
   void giveup_current_region();
   HeapWord* finger()            { return _finger; }
   bool has_aborted()            { return _has_aborted; }
   void set_has_aborted()        { _has_aborted = true; }
   void clear_has_aborted()      { _has_aborted = false; }
   bool has_timed_out()          { return _has_timed_out; }
   bool claimed()                { return _claimed; }
   // Support routines for the partially scanned region that may be
   // recorded as a result of aborting while draining the CMRegionStack
   MemRegion aborted_region()    { return _aborted_region; }
   void set_aborted_region(MemRegion mr)
                                 { _aborted_region = mr; }
   // Clears any recorded partially scanned region
   void clear_aborted_region()   { set_aborted_region(MemRegion()); }
   void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
   // It grays the object by marking it and, if necessary, pushing it
   // on the local queue
   inline void deal_with_reference(oop obj);
   // It scans an object and visits its children.
   void scan_object(oop obj);
   // It pushes an object on the local queue.
   inline void push(oop obj);
   // These two move entries to/from the global stack.
   void move_entries_to_global_stack();
   void get_entries_from_global_stack();
   // It pops and scans objects from the local queue. If partially is
   // true, then it stops when the queue size is of a given limit. If
   // partially is false, then it stops when the queue is empty.
   void drain_local_queue(bool partially);
   // It moves entries from the global stack to the local queue and
   // drains the local queue. If partially is true, then it stops when
   // both the global stack and the local queue reach a given size. If
   // partially if false, it tries to empty them totally.
   void drain_global_stack(bool partially);
   // It keeps picking SATB buffers and processing them until no SATB
   // buffers are available.
   void drain_satb_buffers();
   // It keeps popping regions from the region stack and processing
   // them until the region stack is empty.
   void drain_region_stack(BitMapClosure* closure);
   // moves the local finger to a new location
   inline void move_finger_to(HeapWord* new_finger) {
     assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
     _finger = new_finger;
   }
   // moves the region finger to a new location
   inline void move_region_finger_to(HeapWord* new_finger) {
     assert(new_finger < _cm->finger(), "invariant");
     _region_finger = new_finger;
   }
   CMTask(int task_num, ConcurrentMark *cm,
          size_t* marked_bytes, BitMap* card_bm,
          CMTaskQueue* task_queue, CMTaskQueueSet* task_queues);
   // it prints statistics associated with this task
   void print_stats();
 #if _MARKING_STATS_
   void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
 #endif // _MARKING_STATS_
 };
 // Class that's used to to print out per-region liveness
 // information. It's currently used at the end of marking and also
 // after we sort the old regions at the end of the cleanup operation.
 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
 private:
   outputStream* _out;
   // Accumulators for these values.
   size_t _total_used_bytes;
   size_t _total_capacity_bytes;
   size_t _total_prev_live_bytes;
   size_t _total_next_live_bytes;
   // These are set up when we come across a "stars humongous" region
   // (as this is where most of this information is stored, not in the
   // subsequent "continues humongous" regions). After that, for every
   // region in a given humongous region series we deduce the right
   // values for it by simply subtracting the appropriate amount from
   // these fields. All these values should reach 0 after we've visited
   // the last region in the series.
   size_t _hum_used_bytes;
   size_t _hum_capacity_bytes;
   size_t _hum_prev_live_bytes;
   size_t _hum_next_live_bytes;
   static double perc(size_t val, size_t total) {
     if (total == 0) {
       return 0.0;
     } else {
       return 100.0 * ((double) val / (double) total);
     }
   }
   static double bytes_to_mb(size_t val) {
     return (double) val / (double) M;
   }
   // See the .cpp file.
   size_t get_hum_bytes(size_t* hum_bytes);
   void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
                      size_t* prev_live_bytes, size_t* next_live_bytes);
 public:
   // The header and footer are printed in the constructor and
   // destructor respectively.
   G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
   virtual bool doHeapRegion(HeapRegion* r);
   ~G1PrintRegionLivenessInfoClosure();
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/concurrentMark.hpp@64bf7c8270cb (annotated)

src/share/vm/gc_implementation/g1/concurrentMark.hpp