1 /*
2 * Copyright (c) 2023, 2024, 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.
8 *
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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).
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24
25 #ifndef SHARE_CDS_ARCHIVEHEAPWRITER_HPP
26 #define SHARE_CDS_ARCHIVEHEAPWRITER_HPP
27
28 #include "cds/heapShared.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/allStatic.hpp"
31 #include "oops/oopHandle.hpp"
32 #include "utilities/bitMap.hpp"
33 #include "utilities/exceptions.hpp"
34 #include "utilities/growableArray.hpp"
35 #include "utilities/macros.hpp"
36 #include "utilities/resourceHash.hpp"
37
38 class MemRegion;
39
40 class ArchiveHeapInfo {
41 MemRegion _buffer_region; // Contains the archived objects to be written into the CDS archive.
42 CHeapBitMap _oopmap;
43 CHeapBitMap _ptrmap;
44 HeapRootSegments _heap_root_segments;
45
46 public:
47 ArchiveHeapInfo() : _buffer_region(), _oopmap(128, mtClassShared), _ptrmap(128, mtClassShared) {}
48 bool is_used() { return !_buffer_region.is_empty(); }
49
50 MemRegion buffer_region() { return _buffer_region; }
51 void set_buffer_region(MemRegion r) { _buffer_region = r; }
52
53 char* buffer_start() { return (char*)_buffer_region.start(); }
54 size_t buffer_byte_size() { return _buffer_region.byte_size(); }
55
56 CHeapBitMap* oopmap() { return &_oopmap; }
57 CHeapBitMap* ptrmap() { return &_ptrmap; }
58
59 void set_heap_root_segments(HeapRootSegments segments) { _heap_root_segments = segments; };
60 HeapRootSegments heap_root_segments() { return _heap_root_segments; }
61 };
62
63 #if INCLUDE_CDS_JAVA_HEAP
64 class ArchiveHeapWriter : AllStatic {
65 friend class HeapShared;
66 // ArchiveHeapWriter manipulates three types of addresses:
67 //
68 // "source" vs "buffered" vs "requested"
69 //
70 // (Note: the design and convention is the same as for the archiving of Metaspace objects.
71 // See archiveBuilder.hpp.)
72 //
73 // - "source objects" are regular Java objects allocated during the execution
74 // of "java -Xshare:dump". They can be used as regular oops.
75 //
76 // HeapShared::archive_objects() recursively searches for the oops that need to be
77 // stored into the CDS archive. These are entered into HeapShared::archived_object_cache().
78 //
79 // - "buffered objects" are copies of the "source objects", and are stored in into
80 // ArchiveHeapWriter::_buffer, which is a GrowableArray that sits outside of
81 // the valid heap range. Therefore we avoid using the addresses of these copies
82 // as oops. They are usually called "buffered_addr" in the code (of the type "address").
83 //
84 // The buffered objects are stored contiguously, possibly with interleaving fillers
85 // to make sure no objects span across boundaries of MIN_GC_REGION_ALIGNMENT.
86 //
87 // - Each archived object has a "requested address" -- at run time, if the object
88 // can be mapped at this address, we can avoid relocation.
89 //
90 // The requested address is implemented differently depending on UseCompressedOops:
91 //
92 // UseCompressedOops == true:
93 // The archived objects are stored assuming that the runtime COOPS compression
94 // scheme is exactly the same as in dump time (or else a more expensive runtime relocation
95 // would be needed.)
96 //
97 // At dump time, we assume that the runtime heap range is exactly the same as
98 // in dump time. The requested addresses of the archived objects are chosen such that
99 // they would occupy the top end of a G1 heap (TBD when dumping is supported by other
100 // collectors. See JDK-8298614).
101 //
102 // UseCompressedOops == false:
103 // At runtime, the heap range is usually picked (randomly) by the OS, so we will almost always
104 // need to perform relocation. Hence, the goal of the "requested address" is to ensure that
105 // the contents of the archived objects are deterministic. I.e., the oop fields of archived
106 // objects will always point to deterministic addresses.
107 //
108 // For G1, the archived heap is written such that the lowest archived object is placed
109 // at NOCOOPS_REQUESTED_BASE. (TBD after JDK-8298614).
110 // ----------------------------------------------------------------------
111
112 public:
113 static const intptr_t NOCOOPS_REQUESTED_BASE = 0x10000000;
114
115 // The minimum region size of all collectors that are supported by CDS.
116 // G1 heap region size can never be smaller than 1M.
117 // Shenandoah heap region size can never be smaller than 256K.
118 static constexpr int MIN_GC_REGION_ALIGNMENT = 256 * K;
119
120 private:
121 class EmbeddedOopRelocator;
122 struct NativePointerInfo {
123 oop _src_obj;
124 int _field_offset;
125 };
126
127 static GrowableArrayCHeap<u1, mtClassShared>* _buffer;
128
129 // The number of bytes that have written into _buffer (may be smaller than _buffer->length()).
130 static size_t _buffer_used;
131
132 // The heap root segments information.
133 static HeapRootSegments _heap_root_segments;
134
135 // The address range of the requested location of the archived heap objects.
136 static address _requested_bottom;
137 static address _requested_top;
138
139 static GrowableArrayCHeap<NativePointerInfo, mtClassShared>* _native_pointers;
140 static GrowableArrayCHeap<oop, mtClassShared>* _source_objs;
141
142 // We sort _source_objs_order to minimize the number of bits in ptrmap and oopmap.
143 // See comments near the body of ArchiveHeapWriter::compare_objs_by_oop_fields().
144 // The objects will be written in the order of:
145 //_source_objs->at(_source_objs_order->at(0)._index)
146 // source_objs->at(_source_objs_order->at(1)._index)
147 // source_objs->at(_source_objs_order->at(2)._index)
148 // ...
149 struct HeapObjOrder {
150 int _index; // The location of this object in _source_objs
151 int _rank; // A lower rank means the object will be written at a lower location.
152 };
153 static GrowableArrayCHeap<HeapObjOrder, mtClassShared>* _source_objs_order;
154
155 typedef ResizeableResourceHashtable<size_t, oop,
156 AnyObj::C_HEAP,
157 mtClassShared> BufferOffsetToSourceObjectTable;
158 static BufferOffsetToSourceObjectTable* _buffer_offset_to_source_obj_table;
159
160 static void allocate_buffer();
161 static void ensure_buffer_space(size_t min_bytes);
162
163 // Both Java bytearray and GrowableArraty use int indices and lengths. Do a safe typecast with range check
164 static int to_array_index(size_t i) {
165 assert(i <= (size_t)max_jint, "must be");
166 return (int)i;
167 }
168 static int to_array_length(size_t n) {
169 return to_array_index(n);
170 }
171
172 template <typename T> static T offset_to_buffered_address(size_t offset) {
173 return (T)(_buffer->adr_at(to_array_index(offset)));
174 }
175
176 static address buffer_bottom() {
177 return offset_to_buffered_address<address>(0);
178 }
179
180 // The exclusive end of the last object that was copied into the buffer.
181 static address buffer_top() {
182 return buffer_bottom() + _buffer_used;
183 }
184
185 static bool in_buffer(address buffered_addr) {
186 return (buffer_bottom() <= buffered_addr) && (buffered_addr < buffer_top());
187 }
188
189 static size_t buffered_address_to_offset(address buffered_addr) {
190 assert(in_buffer(buffered_addr), "sanity");
191 return buffered_addr - buffer_bottom();
192 }
193
194 static void root_segment_at_put(objArrayOop segment, int index, oop root);
195 static objArrayOop allocate_root_segment(size_t offset, int element_count);
196 static void copy_roots_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots);
197 static void copy_source_objs_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots);
198 static size_t copy_one_source_obj_to_buffer(oop src_obj);
199 static void update_stats(oop src_obj);
200
201 static void maybe_fill_gc_region_gap(size_t required_byte_size);
202 static size_t filler_array_byte_size(int length);
203 static int filler_array_length(size_t fill_bytes);
204 static HeapWord* init_filler_array_at_buffer_top(int array_length, size_t fill_bytes);
205
206 static void set_requested_address(ArchiveHeapInfo* info);
207 static void relocate_embedded_oops(GrowableArrayCHeap<oop, mtClassShared>* roots, ArchiveHeapInfo* info);
208 static void compute_ptrmap(ArchiveHeapInfo *info);
209 static bool is_in_requested_range(oop o);
210 static oop requested_obj_from_buffer_offset(size_t offset);
211
212 static oop load_oop_from_buffer(oop* buffered_addr);
213 static oop load_oop_from_buffer(narrowOop* buffered_addr);
214 inline static void store_oop_in_buffer(oop* buffered_addr, oop requested_obj);
215 inline static void store_oop_in_buffer(narrowOop* buffered_addr, oop requested_obj);
216
217 template <typename T> static oop load_source_oop_from_buffer(T* buffered_addr);
218 template <typename T> static void store_requested_oop_in_buffer(T* buffered_addr, oop request_oop);
219
220 template <typename T> static T* requested_addr_to_buffered_addr(T* p);
221 template <typename T> static void relocate_field_in_buffer(T* field_addr_in_buffer, CHeapBitMap* oopmap);
222 template <typename T> static void mark_oop_pointer(T* buffered_addr, CHeapBitMap* oopmap);
223
224 static void update_header_for_requested_obj(oop requested_obj, oop src_obj, Klass* src_klass);
225
226 static int compare_objs_by_oop_fields(HeapObjOrder* a, HeapObjOrder* b);
227 static void sort_source_objs();
228
229 public:
230 static void init() NOT_CDS_JAVA_HEAP_RETURN;
231 static void add_source_obj(oop src_obj);
232 static bool is_too_large_to_archive(size_t size);
233 static bool is_too_large_to_archive(oop obj);
234 static bool is_string_too_large_to_archive(oop string);
235 static void write(GrowableArrayCHeap<oop, mtClassShared>*, ArchiveHeapInfo* heap_info);
236 static address requested_address(); // requested address of the lowest achived heap object
237 static size_t get_filler_size_at(address buffered_addr);
238
239 static void mark_native_pointer(oop src_obj, int offset);
240 static bool is_marked_as_native_pointer(ArchiveHeapInfo* heap_info, oop src_obj, int field_offset);
241 static oop source_obj_to_requested_obj(oop src_obj);
242 static oop buffered_addr_to_source_obj(address buffered_addr);
243 static address buffered_addr_to_requested_addr(address buffered_addr);
244
245 // Archived heap object headers carry pre-computed narrow Klass ids calculated with the
246 // following scheme:
247 // 1) the encoding base must be the mapping start address.
248 // 2) shift must be large enough to result in an encoding range that covers the runtime Klass range.
249 // That Klass range is defined by CDS archive size and runtime class space size. Luckily, the maximum
250 // size can be predicted: archive size is assumed to be <1G, class space size capped at 3G, and at
251 // runtime we put both regions adjacent to each other. Therefore, runtime Klass range size < 4G.
252 // Since nKlass itself is 32 bit, our encoding range len is 4G, and since we set the base directly
253 // at mapping start, these 4G are enough. Therefore, we don't need to shift at all (shift=0).
254 static constexpr int precomputed_narrow_klass_shift = 0;
255
256 };
257 #endif // INCLUDE_CDS_JAVA_HEAP
258 #endif // SHARE_CDS_ARCHIVEHEAPWRITER_HPP