1 /*
2 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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_G1INCSETSTATE_HPP
26 #define SHARE_VM_GC_G1_G1INCSETSTATE_HPP
27
28 #include "gc/g1/g1BiasedArray.hpp"
29 #include "gc/g1/heapRegion.hpp"
30 #include "memory/allocation.hpp"
31
32 // Per-region state during garbage collection.
33 struct InCSetState {
34 public:
35 // We use different types to represent the state value. Particularly SPARC puts
36 // values in structs from "left to right", i.e. MSB to LSB. This results in many
37 // unnecessary shift operations when loading and storing values of this type.
38 // This degrades performance significantly (>10%) on that platform.
39 // Other tested ABIs do not seem to have this problem, and actually tend to
40 // favor smaller types, so we use the smallest usable type there.
41 #ifdef SPARC
42 #define CSETSTATE_FORMAT INTPTR_FORMAT
43 typedef intptr_t in_cset_state_t;
44 #else
45 #define CSETSTATE_FORMAT "%d"
46 typedef int8_t in_cset_state_t;
47 #endif
48 private:
49 in_cset_state_t _value;
50 public:
51 enum {
52 // Selection of the values were driven to micro-optimize the encoding and
53 // frequency of the checks.
54 // The most common check is whether the region is in the collection set or not,
55 // this encoding allows us to use an > 0 check.
56 // The other values are simply encoded in increasing generation order, which
57 // makes getting the next generation fast by a simple increment.
58 Humongous = -1, // The region is humongous
59 NotInCSet = 0, // The region is not in the collection set.
60 Young = 1, // The region is in the collection set and a young region.
61 Old = 2, // The region is in the collection set and an old region.
62 Num
63 };
64
65 InCSetState(in_cset_state_t value = NotInCSet) : _value(value) {
66 assert(is_valid(), "Invalid state %d", _value);
67 }
68
69 in_cset_state_t value() const { return _value; }
70
71 void set_old() { _value = Old; }
72
73 bool is_in_cset_or_humongous() const { return is_in_cset() || is_humongous(); }
74 bool is_in_cset() const { return _value > NotInCSet; }
75
76 bool is_humongous() const { return _value == Humongous; }
77 bool is_young() const { return _value == Young; }
78 bool is_old() const { return _value == Old; }
79
80 #ifdef ASSERT
81 bool is_default() const { return !is_in_cset_or_humongous(); }
82 bool is_valid() const { return (_value >= Humongous) && (_value < Num); }
83 bool is_valid_gen() const { return (_value >= Young && _value <= Old); }
84 #endif
85 };
86
87 // Instances of this class are used for quick tests on whether a reference points
88 // into the collection set and into which generation or is a humongous object
89 //
90 // Each of the array's elements indicates whether the corresponding region is in
91 // the collection set and if so in which generation, or a humongous region.
92 //
93 // We use this to speed up reference processing during young collection and
94 // quickly reclaim humongous objects. For the latter, by making a humongous region
95 // succeed this test, we sort-of add it to the collection set. During the reference
96 // iteration closures, when we see a humongous region, we then simply mark it as
97 // referenced, i.e. live.
98 class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> {
99 protected:
100 InCSetState default_value() const { return InCSetState::NotInCSet; }
101 public:
102 void set_humongous(uintptr_t index) {
103 assert(get_by_index(index).is_default(),
104 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
105 set_by_index(index, InCSetState::Humongous);
106 }
107
108 void clear_humongous(uintptr_t index) {
109 set_by_index(index, InCSetState::NotInCSet);
110 }
111
112 void set_in_young(uintptr_t index) {
113 assert(get_by_index(index).is_default(),
114 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
115 set_by_index(index, InCSetState::Young);
116 }
117
118 void set_in_old(uintptr_t index) {
119 assert(get_by_index(index).is_default(),
120 "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
121 set_by_index(index, InCSetState::Old);
122 }
123
124 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); }
125 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); }
126 bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); }
127 InCSetState at(HeapWord* addr) const { return get_by_address(addr); }
128 void clear() { G1BiasedMappedArray<InCSetState>::clear(); }
129 void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), InCSetState::NotInCSet); }
130 };
131
132 #endif // SHARE_VM_GC_G1_G1INCSETSTATE_HPP