1 /*
2 * Copyright (c) 2024, 2025, 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
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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
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23 */
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 // Between HeapShared::start_scanning_for_oops() and HeapShared::end_scanning_for_oops(),
77 // we recursively search for the oops that need to be stored into the CDS archive.
78 // These are entered into HeapShared::archived_object_cache().
79 //
80 // - "buffered objects" are copies of the "source objects", and are stored in into
81 // ArchiveHeapWriter::_buffer, which is a GrowableArray that sits outside of
82 // the valid heap range. Therefore we avoid using the addresses of these copies
83 // as oops. They are usually called "buffered_addr" in the code (of the type "address").
84 //
85 // The buffered objects are stored contiguously, possibly with interleaving fillers
86 // to make sure no objects span across boundaries of MIN_GC_REGION_ALIGNMENT.
87 //
88 // - Each archived object has a "requested address" -- at run time, if the object
89 // can be mapped at this address, we can avoid relocation.
90 //
91 // The requested address is implemented differently depending on UseCompressedOops:
92 //
93 // UseCompressedOops == true:
94 // The archived objects are stored assuming that the runtime COOPS compression
95 // scheme is exactly the same as in dump time (or else a more expensive runtime relocation
96 // would be needed.)
97 //
98 // At dump time, we assume that the runtime heap range is exactly the same as
99 // in dump time. The requested addresses of the archived objects are chosen such that
100 // they would occupy the top end of a G1 heap (TBD when dumping is supported by other
101 // collectors. See JDK-8298614).
102 //
103 // UseCompressedOops == false:
104 // At runtime, the heap range is usually picked (randomly) by the OS, so we will almost always
105 // need to perform relocation. Hence, the goal of the "requested address" is to ensure that
106 // the contents of the archived objects are deterministic. I.e., the oop fields of archived
107 // objects will always point to deterministic addresses.
108 //
109 // For G1, the archived heap is written such that the lowest archived object is placed
110 // at NOCOOPS_REQUESTED_BASE. (TBD after JDK-8298614).
111 // ----------------------------------------------------------------------
112
113 public:
114 static const intptr_t NOCOOPS_REQUESTED_BASE = 0x10000000;
115
116 // The minimum region size of all collectors that are supported by CDS.
117 // G1 heap region size can never be smaller than 1M.
118 // Shenandoah heap region size can never be smaller than 256K.
119 static constexpr int MIN_GC_REGION_ALIGNMENT = 256 * K;
120
121 private:
122 class EmbeddedOopRelocator;
123 struct NativePointerInfo {
124 oop _src_obj;
125 int _field_offset;
126 };
127
128 static GrowableArrayCHeap<u1, mtClassShared>* _buffer;
129
130 // The number of bytes that have written into _buffer (may be smaller than _buffer->length()).
131 static size_t _buffer_used;
132
133 // The heap root segments information.
134 static HeapRootSegments _heap_root_segments;
135
136 // The address range of the requested location of the archived heap objects.
137 static address _requested_bottom;
138 static address _requested_top;
139
140 static GrowableArrayCHeap<NativePointerInfo, mtClassShared>* _native_pointers;
141 static GrowableArrayCHeap<oop, mtClassShared>* _source_objs;
142
143 // We sort _source_objs_order to minimize the number of bits in ptrmap and oopmap.
144 // See comments near the body of ArchiveHeapWriter::compare_objs_by_oop_fields().
145 // The objects will be written in the order of:
146 //_source_objs->at(_source_objs_order->at(0)._index)
147 // source_objs->at(_source_objs_order->at(1)._index)
148 // source_objs->at(_source_objs_order->at(2)._index)
149 // ...
150 struct HeapObjOrder {
151 int _index; // The location of this object in _source_objs
152 int _rank; // A lower rank means the object will be written at a lower location.
153 };
154 static GrowableArrayCHeap<HeapObjOrder, mtClassShared>* _source_objs_order;
155
156 typedef ResizeableResourceHashtable<size_t, oop,
157 AnyObj::C_HEAP,
158 mtClassShared> BufferOffsetToSourceObjectTable;
159 static BufferOffsetToSourceObjectTable* _buffer_offset_to_source_obj_table;
160
161 static void allocate_buffer();
162 static void ensure_buffer_space(size_t min_bytes);
163
164 // Both Java bytearray and GrowableArraty use int indices and lengths. Do a safe typecast with range check
165 static int to_array_index(size_t i) {
166 assert(i <= (size_t)max_jint, "must be");
167 return (int)i;
168 }
169 static int to_array_length(size_t n) {
170 return to_array_index(n);
171 }
172
173 template <typename T> static T offset_to_buffered_address(size_t offset) {
174 return (T)(_buffer->adr_at(to_array_index(offset)));
175 }
176
177 static address buffer_bottom() {
178 return offset_to_buffered_address<address>(0);
179 }
180
181 // The exclusive end of the last object that was copied into the buffer.
182 static address buffer_top() {
183 return buffer_bottom() + _buffer_used;
184 }
185
186 static bool in_buffer(address buffered_addr) {
187 return (buffer_bottom() <= buffered_addr) && (buffered_addr < buffer_top());
188 }
189
190 static size_t buffered_address_to_offset(address buffered_addr) {
191 assert(in_buffer(buffered_addr), "sanity");
192 return buffered_addr - buffer_bottom();
193 }
194
195 static void root_segment_at_put(objArrayOop segment, int index, oop root);
196 static objArrayOop allocate_root_segment(size_t offset, int element_count);
197 static void copy_roots_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots);
198 static void copy_source_objs_to_buffer(GrowableArrayCHeap<oop, mtClassShared>* roots);
199 static size_t copy_one_source_obj_to_buffer(oop src_obj);
200 static void update_stats(oop src_obj);
201
202 static void maybe_fill_gc_region_gap(size_t required_byte_size);
203 static size_t filler_array_byte_size(int length);
204 static int filler_array_length(size_t fill_bytes);
205 static HeapWord* init_filler_array_at_buffer_top(int array_length, size_t fill_bytes);
206
207 static void set_requested_address(ArchiveHeapInfo* info);
208 static void relocate_embedded_oops(GrowableArrayCHeap<oop, mtClassShared>* roots, ArchiveHeapInfo* info);
209 static void compute_ptrmap(ArchiveHeapInfo *info);
210 static bool is_in_requested_range(oop o);
211 static oop requested_obj_from_buffer_offset(size_t offset);
212
213 static oop load_oop_from_buffer(oop* buffered_addr);
214 static oop load_oop_from_buffer(narrowOop* buffered_addr);
215 inline static void store_oop_in_buffer(oop* buffered_addr, oop requested_obj);
216 inline static void store_oop_in_buffer(narrowOop* buffered_addr, oop requested_obj);
217
218 template <typename T> static oop load_source_oop_from_buffer(T* buffered_addr);
219 template <typename T> static void store_requested_oop_in_buffer(T* buffered_addr, oop request_oop);
220
221 template <typename T> static T* requested_addr_to_buffered_addr(T* p);
222 template <typename T> static void relocate_field_in_buffer(T* field_addr_in_buffer, CHeapBitMap* oopmap);
223 template <typename T> static void mark_oop_pointer(T* buffered_addr, CHeapBitMap* oopmap);
224
225 static void update_header_for_requested_obj(oop requested_obj, oop src_obj, Klass* src_klass);
226
227 static int compare_objs_by_oop_fields(HeapObjOrder* a, HeapObjOrder* b);
228 static void sort_source_objs();
229
230 public:
231 static void init() NOT_CDS_JAVA_HEAP_RETURN;
232 static void add_source_obj(oop src_obj);
233 static bool is_too_large_to_archive(size_t size);
234 static bool is_too_large_to_archive(oop obj);
235 static bool is_string_too_large_to_archive(oop string);
236 static void write(GrowableArrayCHeap<oop, mtClassShared>*, ArchiveHeapInfo* heap_info);
237 static address requested_address(); // requested address of the lowest achived heap object
238 static size_t get_filler_size_at(address buffered_addr);
239
240 static void mark_native_pointer(oop src_obj, int offset);
241 static bool is_marked_as_native_pointer(ArchiveHeapInfo* heap_info, oop src_obj, int field_offset);
242 static oop source_obj_to_requested_obj(oop src_obj);
243 static oop buffered_addr_to_source_obj(address buffered_addr);
244 static address buffered_addr_to_requested_addr(address buffered_addr);
245
246 };
247 #endif // INCLUDE_CDS_JAVA_HEAP
248 #endif // SHARE_CDS_ARCHIVEHEAPWRITER_HPP