hotspot/src/share/vm/gc/g1/g1RemSet.hpp

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#ifndef SHARE_VM_GC_G1_G1REMSET_HPP
#define SHARE_VM_GC_G1_G1REMSET_HPP

#include "gc/g1/dirtyCardQueue.hpp"
#include "gc/g1/g1CardLiveData.hpp"
#include "gc/g1/g1RemSetSummary.hpp"
#include "gc/g1/heapRegion.hpp"
#include "memory/allocation.hpp"
#include "memory/iterator.hpp"

// A G1RemSet provides ways of iterating over pointers into a selected
// collection set.

class BitMap;
class CardTableModRefBS;
class G1BlockOffsetTable;
class CodeBlobClosure;
class G1CollectedHeap;
class G1HotCardCache;
class G1ParPushHeapRSClosure;
class G1RemSetScanState;
class G1Policy;
class G1SATBCardTableModRefBS;
class HeapRegionClaimer;

// A G1RemSet in which each heap region has a rem set that records the
// external heap references into it.  Uses a mod ref bs to track updates,
// so that they can be used to update the individual region remsets.
class G1RemSet: public CHeapObj<mtGC> {
private:
  G1RemSetScanState* _scan_state;
  G1CardLiveData _card_live_data;

  G1RemSetSummary _prev_period_summary;

  // A DirtyCardQueueSet that is used to hold cards that contain
  // references into the current collection set. This is used to
  // update the remembered sets of the regions in the collection
  // set in the event of an evacuation failure.
  DirtyCardQueueSet _into_cset_dirty_card_queue_set;

protected:
  G1CollectedHeap* _g1;
  size_t _conc_refine_cards;
  uint n_workers();

protected:
  CardTableModRefBS*     _ct_bs;
  G1Policy*              _g1p;
  G1HotCardCache*        _hot_card_cache;

public:
  // Gives an approximation on how many threads can be expected to add records to
  // a remembered set in parallel. This can be used for sizing data structures to
  // decrease performance losses due to data structure sharing.
  // Examples for quantities that influence this value are the maximum number of
  // mutator threads, maximum number of concurrent refinement or GC threads.
  static uint num_par_rem_sets();

  // Initialize data that depends on the heap size being known.
  void initialize(size_t capacity, uint max_regions);

  // This is called to reset dual hash tables after the gc pause
  // is finished and the initial hash table is no longer being
  // scanned.
  void cleanupHRRS();

  G1RemSet(G1CollectedHeap* g1,
           CardTableModRefBS* ct_bs,
           G1HotCardCache* hot_card_cache);
  ~G1RemSet();

  // Invoke "cl->do_oop" on all pointers into the collection set
  // from objects in regions outside the collection set (having
  // invoked "cl->set_region" to set the "from" region correctly
  // beforehand.)
  //
  // Apply non_heap_roots on the oops of the unmarked nmethods
  // on the strong code roots list for each region in the
  // collection set.
  //
  // The "worker_i" param is for the parallel case where the id
  // of the worker thread calling this function can be helpful in
  // partitioning the work to be done. It should be the same as
  // the "i" passed to the calling thread's work(i) function.
  // In the sequential case this param will be ignored.
  //
  // Returns the number of cards scanned while looking for pointers
  // into the collection set.
  size_t oops_into_collection_set_do(G1ParPushHeapRSClosure* cl,
                                     CodeBlobClosure* heap_region_codeblobs,
                                     uint worker_i);

  // Prepare for and cleanup after an oops_into_collection_set_do
  // call.  Must call each of these once before and after (in sequential
  // code) any threads call oops_into_collection_set_do.  (This offers an
  // opportunity to sequential setup and teardown of structures needed by a
  // parallel iteration over the CS's RS.)
  void prepare_for_oops_into_collection_set_do();
  void cleanup_after_oops_into_collection_set_do();

  size_t scan_rem_set(G1ParPushHeapRSClosure* oops_in_heap_closure,
                      CodeBlobClosure* heap_region_codeblobs,
                      uint worker_i);

  G1RemSetScanState* scan_state() const { return _scan_state; }

  // Flush remaining refinement buffers into the remembered set,
  // applying oops_in_heap_closure on the references found.
  void update_rem_set(DirtyCardQueue* into_cset_dcq, G1ParPushHeapRSClosure* oops_in_heap_closure, uint worker_i);

  // Record, if necessary, the fact that *p (where "p" is in region "from",
  // which is required to be non-NULL) has changed to a new non-NULL value.
  template <class T> void par_write_ref(HeapRegion* from, T* p, uint tid);

  // Requires "region_bm" and "card_bm" to be bitmaps with 1 bit per region
  // or card, respectively, such that a region or card with a corresponding
  // 0 bit contains no part of any live object.  Eliminates any remembered
  // set entries that correspond to dead heap ranges. "worker_num" is the
  // parallel thread id of the current thread, and "hrclaimer" is the
  // HeapRegionClaimer that should be used.
  void scrub(uint worker_num, HeapRegionClaimer* hrclaimer);

  // Refine the card corresponding to "card_ptr".
  // If oops_in_heap_closure is not NULL, a true result is returned
  // if the given card contains oops that have references into the
  // current collection set.
  virtual bool refine_card(jbyte* card_ptr,
                           uint worker_i,
                           G1ParPushHeapRSClosure* oops_in_heap_closure);

  // Print accumulated summary info from the start of the VM.
  virtual void print_summary_info();

  // Print accumulated summary info from the last time called.
  virtual void print_periodic_summary_info(const char* header, uint period_count);

  // Prepare remembered set for verification.
  virtual void prepare_for_verify();

  size_t conc_refine_cards() const {
    return _conc_refine_cards;
  }

  void create_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap);
  void finalize_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap);

  // Verify that the liveness count data created concurrently matches one created
  // during this safepoint.
  void verify_card_live_data(WorkGang* workers, G1CMBitMap* actual_bitmap);

  void clear_card_live_data(WorkGang* workers);

#ifdef ASSERT
  void verify_card_live_data_is_clear();
#endif
};

class G1ScanRSClosure : public HeapRegionClosure {
  G1RemSetScanState* _scan_state;

  size_t _cards_done;
  size_t _cards;
  G1CollectedHeap* _g1h;

  G1ParPushHeapRSClosure* _push_heap_cl;
  CodeBlobClosure* _code_root_cl;

  G1BlockOffsetTable* _bot;
  G1SATBCardTableModRefBS *_ct_bs;

  double _strong_code_root_scan_time_sec;
  uint   _worker_i;
  size_t _block_size;

  void scan_card(size_t index, HeapRegion *r);
  void scan_strong_code_roots(HeapRegion* r);
public:
  G1ScanRSClosure(G1RemSetScanState* scan_state,
                  G1ParPushHeapRSClosure* push_heap_cl,
                  CodeBlobClosure* code_root_cl,
                  uint worker_i);

  bool doHeapRegion(HeapRegion* r);

  double strong_code_root_scan_time_sec() {
    return _strong_code_root_scan_time_sec;
  }

  size_t cards_done() { return _cards_done;}
  size_t cards_looked_up() { return _cards;}
};

class UpdateRSOopClosure: public ExtendedOopClosure {
  HeapRegion* _from;
  G1RemSet* _rs;
  uint _worker_i;

  template <class T> void do_oop_work(T* p);

public:
  UpdateRSOopClosure(G1RemSet* rs, uint worker_i = 0) :
    _from(NULL), _rs(rs), _worker_i(worker_i)
  {}

  void set_from(HeapRegion* from) {
    assert(from != NULL, "from region must be non-NULL");
    _from = from;
  }

  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  virtual void do_oop(oop* p)       { do_oop_work(p); }
};

#endif // SHARE_VM_GC_G1_G1REMSET_HPP