hotspot/src/share/vm/memory/cardTableRS.hpp

/*
 * Copyright 2001-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
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 */

class Space;
class OopsInGenClosure;
class DirtyCardToOopClosure;

// This kind of "GenRemSet" uses a card table both as shared data structure
// for a mod ref barrier set and for the rem set information.

class CardTableRS: public GenRemSet {
  friend class VMStructs;
  // Below are private classes used in impl.
  friend class VerifyCTSpaceClosure;
  friend class ClearNoncleanCardWrapper;

  static jbyte clean_card_val() {
    return CardTableModRefBS::clean_card;
  }

  static bool
  card_is_dirty_wrt_gen_iter(jbyte cv) {
    return CardTableModRefBS::card_is_dirty_wrt_gen_iter(cv);
  }

  CardTableModRefBSForCTRS _ct_bs;

  virtual void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl);

  void verify_space(Space* s, HeapWord* gen_start);

  enum ExtendedCardValue {
    youngergen_card   = CardTableModRefBS::CT_MR_BS_last_reserved + 1,
    // These are for parallel collection.
    // There are three P (parallel) youngergen card values.  In general, this
    // needs to be more than the number of generations (including the perm
    // gen) that might have younger_refs_do invoked on them separately.  So
    // if we add more gens, we have to add more values.
    youngergenP1_card  = CardTableModRefBS::CT_MR_BS_last_reserved + 2,
    youngergenP2_card  = CardTableModRefBS::CT_MR_BS_last_reserved + 3,
    youngergenP3_card  = CardTableModRefBS::CT_MR_BS_last_reserved + 4,
    cur_youngergen_and_prev_nonclean_card =
      CardTableModRefBS::CT_MR_BS_last_reserved + 5
  };

  // An array that contains, for each generation, the card table value last
  // used as the current value for a younger_refs_do iteration of that
  // portion of the table.  (The perm gen is index 0; other gens are at
  // their level plus 1.  They youngest gen is in the table, but will
  // always have the value "clean_card".)
  jbyte* _last_cur_val_in_gen;

  jbyte _cur_youngergen_card_val;

  jbyte cur_youngergen_card_val() {
    return _cur_youngergen_card_val;
  }
  void set_cur_youngergen_card_val(jbyte v) {
    _cur_youngergen_card_val = v;
  }
  bool is_prev_youngergen_card_val(jbyte v) {
    return
      youngergen_card <= v &&
      v < cur_youngergen_and_prev_nonclean_card &&
      v != _cur_youngergen_card_val;
  }
  // Return a youngergen_card_value that is not currently in use.
  jbyte find_unused_youngergenP_card_value();

public:
  CardTableRS(MemRegion whole_heap, int max_covered_regions);

  // *** GenRemSet functions.
  GenRemSet::Name rs_kind() { return GenRemSet::CardTable; }

  CardTableRS* as_CardTableRS() { return this; }

  CardTableModRefBS* ct_bs() { return &_ct_bs; }

  // Override.
  void prepare_for_younger_refs_iterate(bool parallel);

  // Card table entries are cleared before application; "blk" is
  // responsible for dirtying if the oop is still older-to-younger after
  // closure application.
  void younger_refs_iterate(Generation* g, OopsInGenClosure* blk);

  void inline_write_ref_field_gc(oop* field, oop new_val) {
    jbyte* byte = _ct_bs.byte_for(field);
    *byte = youngergen_card;
  }
  void write_ref_field_gc_work(oop* field, oop new_val) {
    inline_write_ref_field_gc(field, new_val);
  }

  // Override.  Might want to devirtualize this in the same fashion as
  // above.  Ensures that the value of the card for field says that it's
  // a younger card in the current collection.
  virtual void write_ref_field_gc_par(oop* field, oop new_val);

  void resize_covered_region(MemRegion new_region);

  bool is_aligned(HeapWord* addr) {
    return _ct_bs.is_card_aligned(addr);
  }

  void verify();
  void verify_empty(MemRegion mr);

  void clear(MemRegion mr) { _ct_bs.clear(mr); }
  void clear_into_younger(Generation* gen, bool clear_perm);

  void invalidate(MemRegion mr) { _ct_bs.invalidate(mr); }
  void invalidate_or_clear(Generation* gen, bool younger, bool perm);

  static uintx ct_max_alignment_constraint() {
    return CardTableModRefBS::ct_max_alignment_constraint();
  }

  jbyte* byte_for(void* p)     { return _ct_bs.byte_for(p); }
  jbyte* byte_after(void* p)   { return _ct_bs.byte_after(p); }
  HeapWord* addr_for(jbyte* p) { return _ct_bs.addr_for(p); }

  bool is_prev_nonclean_card_val(jbyte v) {
    return
      youngergen_card <= v &&
      v <= cur_youngergen_and_prev_nonclean_card &&
      v != _cur_youngergen_card_val;
  }

  static bool youngergen_may_have_been_dirty(jbyte cv) {
    return cv == CardTableRS::cur_youngergen_and_prev_nonclean_card;
  }

};