1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  24 
  25 #ifndef SHARE_VM_GC_G1_CONCURRENTMARK_HPP
  26 #define SHARE_VM_GC_G1_CONCURRENTMARK_HPP
  27 
  28 #include "classfile/javaClasses.hpp"
  29 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  30 #include "gc/g1/heapRegionSet.hpp"
  31 #include "gc/shared/taskqueue.hpp"
  32 
  33 class G1CollectedHeap;
  34 class CMBitMap;
  35 class CMTask;
  36 class ConcurrentMark;
  37 typedef GenericTaskQueue<oop, mtGC>            CMTaskQueue;
  38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
  39 
  40 // Closure used by CM during concurrent reference discovery
  41 // and reference processing (during remarking) to determine
  42 // if a particular object is alive. It is primarily used
  43 // to determine if referents of discovered reference objects
  44 // are alive. An instance is also embedded into the
  45 // reference processor as the _is_alive_non_header field
  46 class G1CMIsAliveClosure: public BoolObjectClosure {
  47   G1CollectedHeap* _g1;
  48  public:
  49   G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
  50 
  51   bool do_object_b(oop obj);
  52 };
  53 
  54 // A generic CM bit map.  This is essentially a wrapper around the BitMap
  55 // class, with one bit per (1<<_shifter) HeapWords.
  56 
  57 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
  58  protected:
  59   HeapWord* _bmStartWord;      // base address of range covered by map
  60   size_t    _bmWordSize;       // map size (in #HeapWords covered)
  61   const int _shifter;          // map to char or bit
  62   BitMap    _bm;               // the bit map itself
  63 
  64  public:
  65   // constructor
  66   CMBitMapRO(int shifter);
  67 
  68   // inquiries
  69   HeapWord* startWord()   const { return _bmStartWord; }
  70   // the following is one past the last word in space
  71   HeapWord* endWord()     const { return _bmStartWord + _bmWordSize; }
  72 
  73   // read marks
  74 
  75   bool isMarked(HeapWord* addr) const {
  76     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
  77            "outside underlying space?");
  78     return _bm.at(heapWordToOffset(addr));
  79   }
  80 
  81   // iteration
  82   inline bool iterate(BitMapClosure* cl, MemRegion mr);
  83 
  84   // Return the address corresponding to the next marked bit at or after
  85   // "addr", and before "limit", if "limit" is non-NULL.  If there is no
  86   // such bit, returns "limit" if that is non-NULL, or else "endWord()".
  87   HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
  88                                      const HeapWord* limit = NULL) const;
  89 
  90   // conversion utilities
  91   HeapWord* offsetToHeapWord(size_t offset) const {
  92     return _bmStartWord + (offset << _shifter);
  93   }
  94   size_t heapWordToOffset(const HeapWord* addr) const {
  95     return pointer_delta(addr, _bmStartWord) >> _shifter;
  96   }
  97 
  98   // The argument addr should be the start address of a valid object
  99   HeapWord* nextObject(HeapWord* addr) {
 100     oop obj = (oop) addr;
 101     HeapWord* res =  addr + obj->size();
 102     assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
 103     return res;
 104   }
 105 
 106   void print_on_error(outputStream* st, const char* prefix) const;
 107 
 108   // debugging
 109   NOT_PRODUCT(bool covers(MemRegion rs) const;)
 110 };
 111 
 112 class CMBitMapMappingChangedListener : public G1MappingChangedListener {
 113  private:
 114   CMBitMap* _bm;
 115  public:
 116   CMBitMapMappingChangedListener() : _bm(NULL) {}
 117 
 118   void set_bitmap(CMBitMap* bm) { _bm = bm; }
 119 
 120   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 121 };
 122 
 123 class CMBitMap : public CMBitMapRO {
 124  private:
 125   CMBitMapMappingChangedListener _listener;
 126 
 127  public:
 128   static size_t compute_size(size_t heap_size);
 129   // Returns the amount of bytes on the heap between two marks in the bitmap.
 130   static size_t mark_distance();
 131   // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
 132   // mark bitmap corresponds to. This is the same as the mark distance above.
 133   static size_t heap_map_factor() {
 134     return mark_distance();
 135   }
 136 
 137   CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
 138 
 139   // Initializes the underlying BitMap to cover the given area.
 140   void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
 141 
 142   // Write marks.
 143   inline void mark(HeapWord* addr);
 144   inline void clear(HeapWord* addr);
 145   inline bool parMark(HeapWord* addr);
 146 
 147   void clearRange(MemRegion mr);
 148 
 149   // Clear the whole mark bitmap.
 150   void clearAll();
 151 };
 152 
 153 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
 154 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
 155   VirtualSpace _virtual_space;   // Underlying backing store for actual stack
 156   ConcurrentMark* _cm;
 157   oop* _base;        // bottom of stack
 158   jint _index;       // one more than last occupied index
 159   jint _capacity;    // max #elements
 160   jint _saved_index; // value of _index saved at start of GC
 161 
 162   bool  _overflow;
 163   bool  _should_expand;
 164 
 165  public:
 166   CMMarkStack(ConcurrentMark* cm);
 167   ~CMMarkStack();
 168 
 169   bool allocate(size_t capacity);
 170 
 171   // Pushes the first "n" elements of "ptr_arr" on the stack.
 172   // Locking impl: concurrency is allowed only with
 173   // "par_push_arr" and/or "par_pop_arr" operations, which use the same
 174   // locking strategy.
 175   void par_push_arr(oop* ptr_arr, int n);
 176 
 177   // If returns false, the array was empty.  Otherwise, removes up to "max"
 178   // elements from the stack, and transfers them to "ptr_arr" in an
 179   // unspecified order.  The actual number transferred is given in "n" ("n
 180   // == 0" is deliberately redundant with the return value.)  Locking impl:
 181   // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
 182   // operations, which use the same locking strategy.
 183   bool par_pop_arr(oop* ptr_arr, int max, int* n);
 184 
 185   bool isEmpty()    { return _index == 0; }
 186   int  maxElems()   { return _capacity; }
 187 
 188   bool overflow() { return _overflow; }
 189   void clear_overflow() { _overflow = false; }
 190 
 191   bool should_expand() const { return _should_expand; }
 192   void set_should_expand();
 193 
 194   // Expand the stack, typically in response to an overflow condition
 195   void expand();
 196 
 197   int  size() { return _index; }
 198 
 199   void setEmpty()   { _index = 0; clear_overflow(); }
 200 
 201   // Record the current index.
 202   void note_start_of_gc();
 203 
 204   // Make sure that we have not added any entries to the stack during GC.
 205   void note_end_of_gc();
 206 
 207   // Apply fn to each oop in the mark stack, up to the bound recorded
 208   // via one of the above "note" functions.  The mark stack must not
 209   // be modified while iterating.
 210   template<typename Fn> void iterate(Fn fn);
 211 };
 212 
 213 class YoungList;
 214 
 215 // Root Regions are regions that are not empty at the beginning of a
 216 // marking cycle and which we might collect during an evacuation pause
 217 // while the cycle is active. Given that, during evacuation pauses, we
 218 // do not copy objects that are explicitly marked, what we have to do
 219 // for the root regions is to scan them and mark all objects reachable
 220 // from them. According to the SATB assumptions, we only need to visit
 221 // each object once during marking. So, as long as we finish this scan
 222 // before the next evacuation pause, we can copy the objects from the
 223 // root regions without having to mark them or do anything else to them.
 224 //
 225 // Currently, we only support root region scanning once (at the start
 226 // of the marking cycle) and the root regions are all the survivor
 227 // regions populated during the initial-mark pause.
 228 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
 229 private:
 230   YoungList*           _young_list;
 231   ConcurrentMark*      _cm;
 232 
 233   volatile bool        _scan_in_progress;
 234   volatile bool        _should_abort;
 235   HeapRegion* volatile _next_survivor;
 236 
 237 public:
 238   CMRootRegions();
 239   // We actually do most of the initialization in this method.
 240   void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
 241 
 242   // Reset the claiming / scanning of the root regions.
 243   void prepare_for_scan();
 244 
 245   // Forces get_next() to return NULL so that the iteration aborts early.
 246   void abort() { _should_abort = true; }
 247 
 248   // Return true if the CM thread are actively scanning root regions,
 249   // false otherwise.
 250   bool scan_in_progress() { return _scan_in_progress; }
 251 
 252   // Claim the next root region to scan atomically, or return NULL if
 253   // all have been claimed.
 254   HeapRegion* claim_next();
 255 
 256   // Flag that we're done with root region scanning and notify anyone
 257   // who's waiting on it. If aborted is false, assume that all regions
 258   // have been claimed.
 259   void scan_finished();
 260 
 261   // If CM threads are still scanning root regions, wait until they
 262   // are done. Return true if we had to wait, false otherwise.
 263   bool wait_until_scan_finished();
 264 };
 265 
 266 class ConcurrentMarkThread;
 267 
 268 class ConcurrentMark: public CHeapObj<mtGC> {
 269   friend class CMMarkStack;
 270   friend class ConcurrentMarkThread;
 271   friend class CMTask;
 272   friend class CMBitMapClosure;
 273   friend class CMRemarkTask;
 274   friend class CMConcurrentMarkingTask;
 275   friend class G1ParNoteEndTask;
 276   friend class CalcLiveObjectsClosure;
 277   friend class G1CMRefProcTaskProxy;
 278   friend class G1CMRefProcTaskExecutor;
 279   friend class G1CMKeepAliveAndDrainClosure;
 280   friend class G1CMDrainMarkingStackClosure;
 281 
 282 protected:
 283   ConcurrentMarkThread* _cmThread;   // The thread doing the work
 284   G1CollectedHeap*      _g1h;        // The heap
 285   uint                  _parallel_marking_threads; // The number of marking
 286                                                    // threads we're using
 287   uint                  _max_parallel_marking_threads; // Max number of marking
 288                                                        // threads we'll ever use
 289   double                _sleep_factor; // How much we have to sleep, with
 290                                        // respect to the work we just did, to
 291                                        // meet the marking overhead goal
 292   double                _marking_task_overhead; // Marking target overhead for
 293                                                 // a single task
 294 
 295   FreeRegionList        _cleanup_list;
 296 
 297   // Concurrent marking support structures
 298   CMBitMap                _markBitMap1;
 299   CMBitMap                _markBitMap2;
 300   CMBitMapRO*             _prevMarkBitMap; // Completed mark bitmap
 301   CMBitMap*               _nextMarkBitMap; // Under-construction mark bitmap
 302 
 303   BitMap                  _region_bm;
 304   BitMap                  _card_bm;
 305 
 306   // Heap bounds
 307   HeapWord*               _heap_start;
 308   HeapWord*               _heap_end;
 309 
 310   // Root region tracking and claiming
 311   CMRootRegions           _root_regions;
 312 
 313   // For gray objects
 314   CMMarkStack             _markStack; // Grey objects behind global finger
 315   HeapWord* volatile      _finger;  // The global finger, region aligned,
 316                                     // always points to the end of the
 317                                     // last claimed region
 318 
 319   // Marking tasks
 320   uint                    _max_worker_id;// Maximum worker id
 321   uint                    _active_tasks; // Task num currently active
 322   CMTask**                _tasks;        // Task queue array (max_worker_id len)
 323   CMTaskQueueSet*         _task_queues;  // Task queue set
 324   ParallelTaskTerminator  _terminator;   // For termination
 325 
 326   // Two sync barriers that are used to synchronize tasks when an
 327   // overflow occurs. The algorithm is the following. All tasks enter
 328   // the first one to ensure that they have all stopped manipulating
 329   // the global data structures. After they exit it, they re-initialize
 330   // their data structures and task 0 re-initializes the global data
 331   // structures. Then, they enter the second sync barrier. This
 332   // ensure, that no task starts doing work before all data
 333   // structures (local and global) have been re-initialized. When they
 334   // exit it, they are free to start working again.
 335   WorkGangBarrierSync     _first_overflow_barrier_sync;
 336   WorkGangBarrierSync     _second_overflow_barrier_sync;
 337 
 338   // This is set by any task, when an overflow on the global data
 339   // structures is detected
 340   volatile bool           _has_overflown;
 341   // True: marking is concurrent, false: we're in remark
 342   volatile bool           _concurrent;
 343   // Set at the end of a Full GC so that marking aborts
 344   volatile bool           _has_aborted;
 345 
 346   // Used when remark aborts due to an overflow to indicate that
 347   // another concurrent marking phase should start
 348   volatile bool           _restart_for_overflow;
 349 
 350   // This is true from the very start of concurrent marking until the
 351   // point when all the tasks complete their work. It is really used
 352   // to determine the points between the end of concurrent marking and
 353   // time of remark.
 354   volatile bool           _concurrent_marking_in_progress;
 355 
 356   // True only inside of markFromRoots().
 357   // Similar to _concurrent_marking_in_progress but this is set to false
 358   // when CMConcurrentMarkingTask is finished.
 359   volatile bool           _concurrent_marking_from_roots;
 360 
 361   // All of these times are in ms
 362   NumberSeq _init_times;
 363   NumberSeq _remark_times;
 364   NumberSeq _remark_mark_times;
 365   NumberSeq _remark_weak_ref_times;
 366   NumberSeq _cleanup_times;
 367   double    _total_counting_time;
 368   double    _total_rs_scrub_time;
 369 
 370   double*   _accum_task_vtime;   // Accumulated task vtime
 371 
 372   WorkGang* _parallel_workers;
 373 
 374   void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
 375   void weakRefsWork(bool clear_all_soft_refs);
 376 
 377   void swapMarkBitMaps();
 378 
 379   // It resets the global marking data structures, as well as the
 380   // task local ones; should be called during initial mark.
 381   void reset();
 382 
 383   // Resets all the marking data structures. Called when we have to restart
 384   // marking or when marking completes (via set_non_marking_state below).
 385   void reset_marking_state(bool clear_overflow = true);
 386 
 387   // We do this after we're done with marking so that the marking data
 388   // structures are initialized to a sensible and predictable state.
 389   void set_non_marking_state();
 390 
 391   // Called to indicate how many threads are currently active.
 392   void set_concurrency(uint active_tasks);
 393 
 394   // It should be called to indicate which phase we're in (concurrent
 395   // mark or remark) and how many threads are currently active.
 396   void set_concurrency_and_phase(uint active_tasks, bool concurrent);
 397 
 398   // Prints all gathered CM-related statistics
 399   void print_stats();
 400 
 401   bool cleanup_list_is_empty() {
 402     return _cleanup_list.is_empty();
 403   }
 404 
 405   // Accessor methods
 406   uint parallel_marking_threads() const     { return _parallel_marking_threads; }
 407   uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
 408   double sleep_factor()                     { return _sleep_factor; }
 409   double marking_task_overhead()            { return _marking_task_overhead;}
 410 
 411   HeapWord*               finger()          { return _finger;   }
 412   bool                    concurrent()      { return _concurrent; }
 413   uint                    active_tasks()    { return _active_tasks; }
 414   ParallelTaskTerminator* terminator()      { return &_terminator; }
 415 
 416   // It claims the next available region to be scanned by a marking
 417   // task/thread. It might return NULL if the next region is empty or
 418   // we have run out of regions. In the latter case, out_of_regions()
 419   // determines whether we've really run out of regions or the task
 420   // should call claim_region() again. This might seem a bit
 421   // awkward. Originally, the code was written so that claim_region()
 422   // either successfully returned with a non-empty region or there
 423   // were no more regions to be claimed. The problem with this was
 424   // that, in certain circumstances, it iterated over large chunks of
 425   // the heap finding only empty regions and, while it was working, it
 426   // was preventing the calling task to call its regular clock
 427   // method. So, this way, each task will spend very little time in
 428   // claim_region() and is allowed to call the regular clock method
 429   // frequently.
 430   HeapRegion* claim_region(uint worker_id);
 431 
 432   // It determines whether we've run out of regions to scan. Note that
 433   // the finger can point past the heap end in case the heap was expanded
 434   // to satisfy an allocation without doing a GC. This is fine, because all
 435   // objects in those regions will be considered live anyway because of
 436   // SATB guarantees (i.e. their TAMS will be equal to bottom).
 437   bool        out_of_regions() { return _finger >= _heap_end; }
 438 
 439   // Returns the task with the given id
 440   CMTask* task(int id) {
 441     assert(0 <= id && id < (int) _active_tasks,
 442            "task id not within active bounds");
 443     return _tasks[id];
 444   }
 445 
 446   // Returns the task queue with the given id
 447   CMTaskQueue* task_queue(int id) {
 448     assert(0 <= id && id < (int) _active_tasks,
 449            "task queue id not within active bounds");
 450     return (CMTaskQueue*) _task_queues->queue(id);
 451   }
 452 
 453   // Returns the task queue set
 454   CMTaskQueueSet* task_queues()  { return _task_queues; }
 455 
 456   // Access / manipulation of the overflow flag which is set to
 457   // indicate that the global stack has overflown
 458   bool has_overflown()           { return _has_overflown; }
 459   void set_has_overflown()       { _has_overflown = true; }
 460   void clear_has_overflown()     { _has_overflown = false; }
 461   bool restart_for_overflow()    { return _restart_for_overflow; }
 462 
 463   // Methods to enter the two overflow sync barriers
 464   void enter_first_sync_barrier(uint worker_id);
 465   void enter_second_sync_barrier(uint worker_id);
 466 
 467   // Start measuring concurrent mark from ConcurrentMark::markFromRoots().
 468   void register_mark_from_roots_phase_start();
 469 
 470   // End measuring concurrent mark from ConcurrentMark::markFromRoots().
 471   void register_mark_from_roots_phase_end();
 472 
 473   // Live Data Counting data structures...
 474   // These data structures are initialized at the start of
 475   // marking. They are written to while marking is active.
 476   // They are aggregated during remark; the aggregated values
 477   // are then used to populate the _region_bm, _card_bm, and
 478   // the total live bytes, which are then subsequently updated
 479   // during cleanup.
 480 
 481   // An array of bitmaps (one bit map per task). Each bitmap
 482   // is used to record the cards spanned by the live objects
 483   // marked by that task/worker.
 484   BitMap*  _count_card_bitmaps;
 485 
 486   // Used to record the number of marked live bytes
 487   // (for each region, by worker thread).
 488   size_t** _count_marked_bytes;
 489 
 490   // Card index of the bottom of the G1 heap. Used for biasing indices into
 491   // the card bitmaps.
 492   intptr_t _heap_bottom_card_num;
 493 
 494   // Set to true when initialization is complete
 495   bool _completed_initialization;
 496 
 497 public:
 498   // Manipulation of the global mark stack.
 499   // The push and pop operations are used by tasks for transfers
 500   // between task-local queues and the global mark stack, and use
 501   // locking for concurrency safety.
 502   bool mark_stack_push(oop* arr, int n) {
 503     _markStack.par_push_arr(arr, n);
 504     if (_markStack.overflow()) {
 505       set_has_overflown();
 506       return false;
 507     }
 508     return true;
 509   }
 510   void mark_stack_pop(oop* arr, int max, int* n) {
 511     _markStack.par_pop_arr(arr, max, n);
 512   }
 513   size_t mark_stack_size()                { return _markStack.size(); }
 514   size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
 515   bool mark_stack_overflow()              { return _markStack.overflow(); }
 516   bool mark_stack_empty()                 { return _markStack.isEmpty(); }
 517 
 518   CMRootRegions* root_regions() { return &_root_regions; }
 519 
 520   bool concurrent_marking_in_progress() {
 521     return _concurrent_marking_in_progress;
 522   }
 523   void set_concurrent_marking_in_progress() {
 524     _concurrent_marking_in_progress = true;
 525   }
 526   void clear_concurrent_marking_in_progress() {
 527     _concurrent_marking_in_progress = false;
 528   }
 529 
 530   bool concurrent_marking_from_roots() const {
 531     return _concurrent_marking_from_roots;
 532   }
 533 
 534   void update_accum_task_vtime(int i, double vtime) {
 535     _accum_task_vtime[i] += vtime;
 536   }
 537 
 538   double all_task_accum_vtime() {
 539     double ret = 0.0;
 540     for (uint i = 0; i < _max_worker_id; ++i)
 541       ret += _accum_task_vtime[i];
 542     return ret;
 543   }
 544 
 545   // Attempts to steal an object from the task queues of other tasks
 546   bool try_stealing(uint worker_id, int* hash_seed, oop& obj);
 547 
 548   ConcurrentMark(G1CollectedHeap* g1h,
 549                  G1RegionToSpaceMapper* prev_bitmap_storage,
 550                  G1RegionToSpaceMapper* next_bitmap_storage);
 551   ~ConcurrentMark();
 552 
 553   ConcurrentMarkThread* cmThread() { return _cmThread; }
 554 
 555   CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
 556   CMBitMap*   nextMarkBitMap() const { return _nextMarkBitMap; }
 557 
 558   // Returns the number of GC threads to be used in a concurrent
 559   // phase based on the number of GC threads being used in a STW
 560   // phase.
 561   uint scale_parallel_threads(uint n_par_threads);
 562 
 563   // Calculates the number of GC threads to be used in a concurrent phase.
 564   uint calc_parallel_marking_threads();
 565 
 566   // The following three are interaction between CM and
 567   // G1CollectedHeap
 568 
 569   // This notifies CM that a root during initial-mark needs to be
 570   // grayed. It is MT-safe. word_size is the size of the object in
 571   // words. It is passed explicitly as sometimes we cannot calculate
 572   // it from the given object because it might be in an inconsistent
 573   // state (e.g., in to-space and being copied). So the caller is
 574   // responsible for dealing with this issue (e.g., get the size from
 575   // the from-space image when the to-space image might be
 576   // inconsistent) and always passing the size. hr is the region that
 577   // contains the object and it's passed optionally from callers who
 578   // might already have it (no point in recalculating it).
 579   inline void grayRoot(oop obj,
 580                        size_t word_size,
 581                        uint worker_id,
 582                        HeapRegion* hr = NULL);
 583 
 584   // Clear the next marking bitmap (will be called concurrently).
 585   void clearNextBitmap();
 586 
 587   // Return whether the next mark bitmap has no marks set. To be used for assertions
 588   // only. Will not yield to pause requests.
 589   bool nextMarkBitmapIsClear();
 590 
 591   // These two do the work that needs to be done before and after the
 592   // initial root checkpoint. Since this checkpoint can be done at two
 593   // different points (i.e. an explicit pause or piggy-backed on a
 594   // young collection), then it's nice to be able to easily share the
 595   // pre/post code. It might be the case that we can put everything in
 596   // the post method. TP
 597   void checkpointRootsInitialPre();
 598   void checkpointRootsInitialPost();
 599 
 600   // Scan all the root regions and mark everything reachable from
 601   // them.
 602   void scanRootRegions();
 603 
 604   // Scan a single root region and mark everything reachable from it.
 605   void scanRootRegion(HeapRegion* hr, uint worker_id);
 606 
 607   // Do concurrent phase of marking, to a tentative transitive closure.
 608   void markFromRoots();
 609 
 610   void checkpointRootsFinal(bool clear_all_soft_refs);
 611   void checkpointRootsFinalWork();
 612   void cleanup();
 613   void completeCleanup();
 614 
 615   // Mark in the previous bitmap.  NB: this is usually read-only, so use
 616   // this carefully!
 617   inline void markPrev(oop p);
 618 
 619   // Clears marks for all objects in the given range, for the prev or
 620   // next bitmaps.  NB: the previous bitmap is usually
 621   // read-only, so use this carefully!
 622   void clearRangePrevBitmap(MemRegion mr);
 623 
 624   // Notify data structures that a GC has started.
 625   void note_start_of_gc() {
 626     _markStack.note_start_of_gc();
 627   }
 628 
 629   // Notify data structures that a GC is finished.
 630   void note_end_of_gc() {
 631     _markStack.note_end_of_gc();
 632   }
 633 
 634   // Verify that there are no CSet oops on the stacks (taskqueues /
 635   // global mark stack) and fingers (global / per-task).
 636   // If marking is not in progress, it's a no-op.
 637   void verify_no_cset_oops() PRODUCT_RETURN;
 638 
 639   bool isPrevMarked(oop p) const {
 640     assert(p != NULL && p->is_oop(), "expected an oop");
 641     HeapWord* addr = (HeapWord*)p;
 642     assert(addr >= _prevMarkBitMap->startWord() ||
 643            addr < _prevMarkBitMap->endWord(), "in a region");
 644 
 645     return _prevMarkBitMap->isMarked(addr);
 646   }
 647 
 648   inline bool do_yield_check(uint worker_i = 0);
 649 
 650   // Called to abort the marking cycle after a Full GC takes place.
 651   void abort();
 652 
 653   bool has_aborted()      { return _has_aborted; }
 654 
 655   void print_summary_info();
 656 
 657   void print_worker_threads_on(outputStream* st) const;
 658 
 659   void print_on_error(outputStream* st) const;
 660 
 661   // Liveness counting
 662 
 663   // Utility routine to set an exclusive range of cards on the given
 664   // card liveness bitmap
 665   inline void set_card_bitmap_range(BitMap* card_bm,
 666                                     BitMap::idx_t start_idx,
 667                                     BitMap::idx_t end_idx,
 668                                     bool is_par);
 669 
 670   // Returns the card number of the bottom of the G1 heap.
 671   // Used in biasing indices into accounting card bitmaps.
 672   intptr_t heap_bottom_card_num() const {
 673     return _heap_bottom_card_num;
 674   }
 675 
 676   // Returns the card bitmap for a given task or worker id.
 677   BitMap* count_card_bitmap_for(uint worker_id) {
 678     assert(worker_id < _max_worker_id, "oob");
 679     assert(_count_card_bitmaps != NULL, "uninitialized");
 680     BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
 681     assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
 682     return task_card_bm;
 683   }
 684 
 685   // Returns the array containing the marked bytes for each region,
 686   // for the given worker or task id.
 687   size_t* count_marked_bytes_array_for(uint worker_id) {
 688     assert(worker_id < _max_worker_id, "oob");
 689     assert(_count_marked_bytes != NULL, "uninitialized");
 690     size_t* marked_bytes_array = _count_marked_bytes[worker_id];
 691     assert(marked_bytes_array != NULL, "uninitialized");
 692     return marked_bytes_array;
 693   }
 694 
 695   // Returns the index in the liveness accounting card table bitmap
 696   // for the given address
 697   inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
 698 
 699   // Counts the size of the given memory region in the the given
 700   // marked_bytes array slot for the given HeapRegion.
 701   // Sets the bits in the given card bitmap that are associated with the
 702   // cards that are spanned by the memory region.
 703   inline void count_region(MemRegion mr,
 704                            HeapRegion* hr,
 705                            size_t* marked_bytes_array,
 706                            BitMap* task_card_bm);
 707 
 708   // Counts the given object in the given task/worker counting
 709   // data structures.
 710   inline void count_object(oop obj,
 711                            HeapRegion* hr,
 712                            size_t* marked_bytes_array,
 713                            BitMap* task_card_bm,
 714                            size_t word_size);
 715 
 716   // Attempts to mark the given object and, if successful, counts
 717   // the object in the given task/worker counting structures.
 718   inline bool par_mark_and_count(oop obj,
 719                                  HeapRegion* hr,
 720                                  size_t* marked_bytes_array,
 721                                  BitMap* task_card_bm);
 722 
 723   // Attempts to mark the given object and, if successful, counts
 724   // the object in the task/worker counting structures for the
 725   // given worker id.
 726   inline bool par_mark_and_count(oop obj,
 727                                  size_t word_size,
 728                                  HeapRegion* hr,
 729                                  uint worker_id);
 730 
 731   // Returns true if initialization was successfully completed.
 732   bool completed_initialization() const {
 733     return _completed_initialization;
 734   }
 735 
 736 protected:
 737   // Clear all the per-task bitmaps and arrays used to store the
 738   // counting data.
 739   void clear_all_count_data();
 740 
 741   // Aggregates the counting data for each worker/task
 742   // that was constructed while marking. Also sets
 743   // the amount of marked bytes for each region and
 744   // the top at concurrent mark count.
 745   void aggregate_count_data();
 746 
 747   // Verification routine
 748   void verify_count_data();
 749 };
 750 
 751 // A class representing a marking task.
 752 class CMTask : public TerminatorTerminator {
 753 private:
 754   enum PrivateConstants {
 755     // the regular clock call is called once the scanned words reaches
 756     // this limit
 757     words_scanned_period          = 12*1024,
 758     // the regular clock call is called once the number of visited
 759     // references reaches this limit
 760     refs_reached_period           = 384,
 761     // initial value for the hash seed, used in the work stealing code
 762     init_hash_seed                = 17,
 763     // how many entries will be transferred between global stack and
 764     // local queues
 765     global_stack_transfer_size    = 16
 766   };
 767 
 768   uint                        _worker_id;
 769   G1CollectedHeap*            _g1h;
 770   ConcurrentMark*             _cm;
 771   CMBitMap*                   _nextMarkBitMap;
 772   // the task queue of this task
 773   CMTaskQueue*                _task_queue;
 774 private:
 775   // the task queue set---needed for stealing
 776   CMTaskQueueSet*             _task_queues;
 777   // indicates whether the task has been claimed---this is only  for
 778   // debugging purposes
 779   bool                        _claimed;
 780 
 781   // number of calls to this task
 782   int                         _calls;
 783 
 784   // when the virtual timer reaches this time, the marking step should
 785   // exit
 786   double                      _time_target_ms;
 787   // the start time of the current marking step
 788   double                      _start_time_ms;
 789 
 790   // the oop closure used for iterations over oops
 791   G1CMOopClosure*             _cm_oop_closure;
 792 
 793   // the region this task is scanning, NULL if we're not scanning any
 794   HeapRegion*                 _curr_region;
 795   // the local finger of this task, NULL if we're not scanning a region
 796   HeapWord*                   _finger;
 797   // limit of the region this task is scanning, NULL if we're not scanning one
 798   HeapWord*                   _region_limit;
 799 
 800   // the number of words this task has scanned
 801   size_t                      _words_scanned;
 802   // When _words_scanned reaches this limit, the regular clock is
 803   // called. Notice that this might be decreased under certain
 804   // circumstances (i.e. when we believe that we did an expensive
 805   // operation).
 806   size_t                      _words_scanned_limit;
 807   // the initial value of _words_scanned_limit (i.e. what it was
 808   // before it was decreased).
 809   size_t                      _real_words_scanned_limit;
 810 
 811   // the number of references this task has visited
 812   size_t                      _refs_reached;
 813   // When _refs_reached reaches this limit, the regular clock is
 814   // called. Notice this this might be decreased under certain
 815   // circumstances (i.e. when we believe that we did an expensive
 816   // operation).
 817   size_t                      _refs_reached_limit;
 818   // the initial value of _refs_reached_limit (i.e. what it was before
 819   // it was decreased).
 820   size_t                      _real_refs_reached_limit;
 821 
 822   // used by the work stealing stuff
 823   int                         _hash_seed;
 824   // if this is true, then the task has aborted for some reason
 825   bool                        _has_aborted;
 826   // set when the task aborts because it has met its time quota
 827   bool                        _has_timed_out;
 828   // true when we're draining SATB buffers; this avoids the task
 829   // aborting due to SATB buffers being available (as we're already
 830   // dealing with them)
 831   bool                        _draining_satb_buffers;
 832 
 833   // number sequence of past step times
 834   NumberSeq                   _step_times_ms;
 835   // elapsed time of this task
 836   double                      _elapsed_time_ms;
 837   // termination time of this task
 838   double                      _termination_time_ms;
 839   // when this task got into the termination protocol
 840   double                      _termination_start_time_ms;
 841 
 842   // true when the task is during a concurrent phase, false when it is
 843   // in the remark phase (so, in the latter case, we do not have to
 844   // check all the things that we have to check during the concurrent
 845   // phase, i.e. SATB buffer availability...)
 846   bool                        _concurrent;
 847 
 848   TruncatedSeq                _marking_step_diffs_ms;
 849 
 850   // Counting data structures. Embedding the task's marked_bytes_array
 851   // and card bitmap into the actual task saves having to go through
 852   // the ConcurrentMark object.
 853   size_t*                     _marked_bytes_array;
 854   BitMap*                     _card_bm;
 855 
 856   // it updates the local fields after this task has claimed
 857   // a new region to scan
 858   void setup_for_region(HeapRegion* hr);
 859   // it brings up-to-date the limit of the region
 860   void update_region_limit();
 861 
 862   // called when either the words scanned or the refs visited limit
 863   // has been reached
 864   void reached_limit();
 865   // recalculates the words scanned and refs visited limits
 866   void recalculate_limits();
 867   // decreases the words scanned and refs visited limits when we reach
 868   // an expensive operation
 869   void decrease_limits();
 870   // it checks whether the words scanned or refs visited reached their
 871   // respective limit and calls reached_limit() if they have
 872   void check_limits() {
 873     if (_words_scanned >= _words_scanned_limit ||
 874         _refs_reached >= _refs_reached_limit) {
 875       reached_limit();
 876     }
 877   }
 878   // this is supposed to be called regularly during a marking step as
 879   // it checks a bunch of conditions that might cause the marking step
 880   // to abort
 881   void regular_clock_call();
 882   bool concurrent() { return _concurrent; }
 883 
 884   // Test whether obj might have already been passed over by the
 885   // mark bitmap scan, and so needs to be pushed onto the mark stack.
 886   bool is_below_finger(oop obj, HeapWord* global_finger) const;
 887 
 888   template<bool scan> void process_grey_object(oop obj);
 889 
 890 public:
 891   // It resets the task; it should be called right at the beginning of
 892   // a marking phase.
 893   void reset(CMBitMap* _nextMarkBitMap);
 894   // it clears all the fields that correspond to a claimed region.
 895   void clear_region_fields();
 896 
 897   void set_concurrent(bool concurrent) { _concurrent = concurrent; }
 898 
 899   // The main method of this class which performs a marking step
 900   // trying not to exceed the given duration. However, it might exit
 901   // prematurely, according to some conditions (i.e. SATB buffers are
 902   // available for processing).
 903   void do_marking_step(double target_ms,
 904                        bool do_termination,
 905                        bool is_serial);
 906 
 907   // These two calls start and stop the timer
 908   void record_start_time() {
 909     _elapsed_time_ms = os::elapsedTime() * 1000.0;
 910   }
 911   void record_end_time() {
 912     _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
 913   }
 914 
 915   // returns the worker ID associated with this task.
 916   uint worker_id() { return _worker_id; }
 917 
 918   // From TerminatorTerminator. It determines whether this task should
 919   // exit the termination protocol after it's entered it.
 920   virtual bool should_exit_termination();
 921 
 922   // Resets the local region fields after a task has finished scanning a
 923   // region; or when they have become stale as a result of the region
 924   // being evacuated.
 925   void giveup_current_region();
 926 
 927   HeapWord* finger()            { return _finger; }
 928 
 929   bool has_aborted()            { return _has_aborted; }
 930   void set_has_aborted()        { _has_aborted = true; }
 931   void clear_has_aborted()      { _has_aborted = false; }
 932   bool has_timed_out()          { return _has_timed_out; }
 933   bool claimed()                { return _claimed; }
 934 
 935   void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
 936 
 937   // Increment the number of references this task has visited.
 938   void increment_refs_reached() { ++_refs_reached; }
 939 
 940   // Grey the object by marking it.  If not already marked, push it on
 941   // the local queue if below the finger.
 942   // Precondition: obj is in region.
 943   // Precondition: obj is below region's NTAMS.
 944   inline void make_reference_grey(oop obj, HeapRegion* region);
 945 
 946   // Grey the object (by calling make_grey_reference) if required,
 947   // e.g. obj is below its containing region's NTAMS.
 948   // Precondition: obj is a valid heap object.
 949   inline void deal_with_reference(oop obj);
 950 
 951   // It scans an object and visits its children.
 952   inline void scan_object(oop obj);
 953 
 954   // It pushes an object on the local queue.
 955   inline void push(oop obj);
 956 
 957   // These two move entries to/from the global stack.
 958   void move_entries_to_global_stack();
 959   void get_entries_from_global_stack();
 960 
 961   // It pops and scans objects from the local queue. If partially is
 962   // true, then it stops when the queue size is of a given limit. If
 963   // partially is false, then it stops when the queue is empty.
 964   void drain_local_queue(bool partially);
 965   // It moves entries from the global stack to the local queue and
 966   // drains the local queue. If partially is true, then it stops when
 967   // both the global stack and the local queue reach a given size. If
 968   // partially if false, it tries to empty them totally.
 969   void drain_global_stack(bool partially);
 970   // It keeps picking SATB buffers and processing them until no SATB
 971   // buffers are available.
 972   void drain_satb_buffers();
 973 
 974   // moves the local finger to a new location
 975   inline void move_finger_to(HeapWord* new_finger) {
 976     assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
 977     _finger = new_finger;
 978   }
 979 
 980   CMTask(uint worker_id,
 981          ConcurrentMark *cm,
 982          size_t* marked_bytes,
 983          BitMap* card_bm,
 984          CMTaskQueue* task_queue,
 985          CMTaskQueueSet* task_queues);
 986 
 987   // it prints statistics associated with this task
 988   void print_stats();
 989 };
 990 
 991 // Class that's used to to print out per-region liveness
 992 // information. It's currently used at the end of marking and also
 993 // after we sort the old regions at the end of the cleanup operation.
 994 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
 995 private:
 996   // Accumulators for these values.
 997   size_t _total_used_bytes;
 998   size_t _total_capacity_bytes;
 999   size_t _total_prev_live_bytes;
1000   size_t _total_next_live_bytes;
1001 
1002   // These are set up when we come across a "stars humongous" region
1003   // (as this is where most of this information is stored, not in the
1004   // subsequent "continues humongous" regions). After that, for every
1005   // region in a given humongous region series we deduce the right
1006   // values for it by simply subtracting the appropriate amount from
1007   // these fields. All these values should reach 0 after we've visited
1008   // the last region in the series.
1009   size_t _hum_used_bytes;
1010   size_t _hum_capacity_bytes;
1011   size_t _hum_prev_live_bytes;
1012   size_t _hum_next_live_bytes;
1013 
1014   // Accumulator for the remembered set size
1015   size_t _total_remset_bytes;
1016 
1017   // Accumulator for strong code roots memory size
1018   size_t _total_strong_code_roots_bytes;
1019 
1020   static double perc(size_t val, size_t total) {
1021     if (total == 0) {
1022       return 0.0;
1023     } else {
1024       return 100.0 * ((double) val / (double) total);
1025     }
1026   }
1027 
1028   static double bytes_to_mb(size_t val) {
1029     return (double) val / (double) M;
1030   }
1031 
1032   // See the .cpp file.
1033   size_t get_hum_bytes(size_t* hum_bytes);
1034   void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1035                      size_t* prev_live_bytes, size_t* next_live_bytes);
1036 
1037 public:
1038   // The header and footer are printed in the constructor and
1039   // destructor respectively.
1040   G1PrintRegionLivenessInfoClosure(const char* phase_name);
1041   virtual bool doHeapRegion(HeapRegion* r);
1042   ~G1PrintRegionLivenessInfoClosure();
1043 };
1044 
1045 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP
--- EOF ---