1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_SHARED_GENREMSET_HPP
26 #define SHARE_VM_GC_SHARED_GENREMSET_HPP
27
28 #include "oops/oop.hpp"
29
30 // A GenRemSet provides ways of iterating over pointers across generations.
31 // (This is especially useful for older-to-younger.)
32
33 class Generation;
34 class BarrierSet;
35 class OopsInGenClosure;
36 class CardTableRS;
37
38 // Helper to remember modified oops in all klasses.
39 class KlassRemSet {
40 bool _accumulate_modified_oops;
41 public:
42 KlassRemSet() : _accumulate_modified_oops(false) {}
43 void set_accumulate_modified_oops(bool value) { _accumulate_modified_oops = value; }
44 bool accumulate_modified_oops() { return _accumulate_modified_oops; }
45 bool mod_union_is_clear();
46 void clear_mod_union();
47 };
48
49 class GenRemSet: public CHeapObj<mtGC> {
50 friend class Generation;
51
52 BarrierSet* _bs;
53 KlassRemSet _klass_rem_set;
54
55 public:
56 GenRemSet(BarrierSet * bs) : _bs(bs) {}
57 GenRemSet() : _bs(NULL) {}
58
59 // These are for dynamic downcasts. Unfortunately that it names the
60 // possible subtypes (but not that they are subtypes!) Return NULL if
61 // the cast is invalid.
62 virtual CardTableRS* as_CardTableRS() { return NULL; }
63
64 // Return the barrier set associated with "this."
65 BarrierSet* bs() { return _bs; }
66
67 // Set the barrier set.
68 void set_bs(BarrierSet* bs) { _bs = bs; }
69
70 KlassRemSet* klass_rem_set() { return &_klass_rem_set; }
71
72 // Do any (sequential) processing necessary to prepare for (possibly
73 // "parallel", if that arg is true) calls to younger_refs_iterate.
74 virtual void prepare_for_younger_refs_iterate(bool parallel) = 0;
75
76 // Apply the "do_oop" method of "blk" to (exactly) all oop locations
77 // 1) that are in objects allocated in "g" at the time of the last call
78 // to "save_Marks", and
79 // 2) that point to objects in younger generations.
80 virtual void younger_refs_iterate(Generation* g, OopsInGenClosure* blk, uint n_threads) = 0;
81
82 virtual void younger_refs_in_space_iterate(Space* sp,
83 OopsInGenClosure* cl,
84 uint n_threads) = 0;
85
86 // This method is used to notify the remembered set that "new_val" has
87 // been written into "field" by the garbage collector.
88 void write_ref_field_gc(void* field, oop new_val);
89 protected:
90 virtual void write_ref_field_gc_work(void* field, oop new_val) = 0;
91 public:
92
93 // A version of the above suitable for use by parallel collectors.
94 virtual void write_ref_field_gc_par(void* field, oop new_val) = 0;
95
96 // Resize one of the regions covered by the remembered set.
97 virtual void resize_covered_region(MemRegion new_region) = 0;
98
99 // If the rem set imposes any alignment restrictions on boundaries
100 // within the heap, this function tells whether they are met.
101 virtual bool is_aligned(HeapWord* addr) = 0;
102
103 // Returns any alignment constraint that the remembered set imposes upon the
104 // heap.
105 static uintx max_alignment_constraint();
106
107 virtual void verify() = 0;
108
109 // If appropriate, print some information about the remset on "tty".
110 virtual void print() {}
111
112 // Informs the RS that the given memregion contains no references to
113 // younger generations.
114 virtual void clear(MemRegion mr) = 0;
115
116 // Informs the RS that there are no references to generations
117 // younger than gen from generations gen and older.
118 // The parameter clear_perm indicates if the perm_gen's
119 // remembered set should also be processed/cleared.
120 virtual void clear_into_younger(Generation* old_gen) = 0;
121
122 // Informs the RS that refs in the given "mr" may have changed
123 // arbitrarily, and therefore may contain old-to-young pointers.
124 // If "whole heap" is true, then this invalidation is part of an
125 // invalidation of the whole heap, which an implementation might
126 // handle differently than that of a sub-part of the heap.
127 virtual void invalidate(MemRegion mr, bool whole_heap = false) = 0;
128
129 // Informs the RS that refs in this generation
130 // may have changed arbitrarily, and therefore may contain
131 // old-to-young pointers in arbitrary locations.
132 virtual void invalidate_or_clear(Generation* old_gen) = 0;
133 };
134
135 #endif // SHARE_VM_GC_SHARED_GENREMSET_HPP