1 /*
2 * Copyright (c) 2014, 2020, 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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7 * published by the Free Software Foundation.
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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 *
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24
25 #ifndef SHARE_GC_G1_G1HEAPREGIONATTR_HPP
26 #define SHARE_GC_G1_G1HEAPREGIONATTR_HPP
27
28 #include "gc/g1/g1BiasedArray.hpp"
29 #include "gc/g1/heapRegion.hpp"
30
31 // Per-region attributes often used during garbage collection to avoid costly
32 // lookups for that information all over the place.
33 struct G1HeapRegionAttr {
34 public:
35 #if defined(_M_ARM64)&& defined(_MSC_VER) && _MSC_VER <= 1927
36 // workaround for MSCV ARM64 bug
37 // https://developercommunity.visualstudio.com/content/problem/1079221/arm64-bad-code-generation-around-signed-char-arith.html
38 typedef int32_t region_type_t;
39 #else
40 typedef int8_t region_type_t;
41 #endif
42 typedef uint8_t needs_remset_update_t;
43
44 private:
45 needs_remset_update_t _needs_remset_update;
46 region_type_t _type;
47
48 public:
49 // Selection of the values for the _type field were driven to micro-optimize the
50 // encoding and frequency of the checks.
51 // The most common check for a given reference is whether the region is in the
52 // collection set or not, and which generation this region is in.
53 // The selected encoding allows us to use a single check (> NotInCSet) for the
54 // former.
55 //
56 // The other values are used for objects in regions requiring various special handling,
57 // eager reclamation of humongous objects or optional regions.
58 static const region_type_t Optional = -3; // The region is optional not in the current collection set.
59 static const region_type_t Humongous = -2; // The region is a humongous candidate not in the current collection set.
60 static const region_type_t NotInCSet = -1; // The region is not in the collection set.
61 static const region_type_t Young = 0; // The region is in the collection set and a young region.
62 static const region_type_t Old = 1; // The region is in the collection set and an old region.
63 static const region_type_t Num = 2;
64
65 G1HeapRegionAttr(region_type_t type = NotInCSet, bool needs_remset_update = false) :
66 _needs_remset_update(needs_remset_update), _type(type) {
67
68 assert(is_valid(), "Invalid type %d", _type);
69 }
70
71 region_type_t type() const { return _type; }
72
73 const char* get_type_str() const {
74 switch (type()) {
75 case Optional: return "Optional";
76 case Humongous: return "Humongous";
77 case NotInCSet: return "NotInCSet";
78 case Young: return "Young";
79 case Old: return "Old";
80 default: ShouldNotReachHere(); return "";
81 }
82 }
83
84 bool needs_remset_update() const { return _needs_remset_update != 0; }
85
86 void set_old() { _type = Old; }
87 void clear_humongous() {
88 assert(is_humongous() || !is_in_cset(), "must be");
89 _type = NotInCSet;
90 }
91 void set_has_remset(bool value) { _needs_remset_update = value ? 1 : 0; }
92
93 bool is_in_cset_or_humongous() const { return is_in_cset() || is_humongous(); }
94 bool is_in_cset() const { return type() >= Young; }
95
96 bool is_humongous() const { return type() == Humongous; }
97 bool is_young() const { return type() == Young; }
98 bool is_old() const { return type() == Old; }
99 bool is_optional() const { return type() == Optional; }
100
101 #ifdef ASSERT
102 bool is_default() const { return type() == NotInCSet; }
103 bool is_valid() const { return (type() >= Optional && type() < Num); }
104 bool is_valid_gen() const { return (type() >= Young && type() <= Old); }
105 #endif
106 };
107
108 // Table for all regions in the heap for above.
109 //
110 // We use this to speed up reference processing during young collection and
111 // quickly reclaim humongous objects. For the latter, at the start of GC, by adding
112 // it as a humongous region we enable special handling for that region. During the
113 // reference iteration closures, when we see a humongous region, we then simply mark
114 // it as referenced, i.e. live, and remove it from this table to prevent further
115 // processing on it.
116 //
117 // This means that this does NOT completely correspond to the information stored
118 // in a HeapRegion, but only to what is interesting for the current young collection.
119 class G1HeapRegionAttrBiasedMappedArray : public G1BiasedMappedArray<G1HeapRegionAttr> {
120 protected:
121 G1HeapRegionAttr default_value() const { return G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet); }
122 public:
123 void set_optional(uintptr_t index, bool needs_remset_update) {
124 assert(get_by_index(index).is_default(),
125 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());
126 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Optional, needs_remset_update));
127 }
128
129 void set_humongous(uintptr_t index, bool needs_remset_update) {
130 assert(get_by_index(index).is_default(),
131 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());
132 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Humongous, needs_remset_update));
133 }
134
135 void clear_humongous(uintptr_t index) {
136 get_ref_by_index(index)->clear_humongous();
137 }
138
139 void set_has_remset(uintptr_t index, bool needs_remset_update) {
140 get_ref_by_index(index)->set_has_remset(needs_remset_update);
141 }
142
143 void set_in_young(uintptr_t index) {
144 assert(get_by_index(index).is_default(),
145 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());
146 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Young, true));
147 }
148
149 void set_in_old(uintptr_t index, bool needs_remset_update) {
150 assert(get_by_index(index).is_default(),
151 "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());
152 set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Old, needs_remset_update));
153 }
154
155 bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); }
156 bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); }
157 bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); }
158 G1HeapRegionAttr at(HeapWord* addr) const { return get_by_address(addr); }
159 void clear() { G1BiasedMappedArray<G1HeapRegionAttr>::clear(); }
160 void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet)); }
161 };
162
163 #endif // SHARE_GC_G1_G1HEAPREGIONATTR_HPP