1 /*
2 * Copyright (c) 2016, 2016, 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_MEMORY_VTBUFFER_HPP
26 #define SHARE_VM_MEMORY_VTBUFFER_HPP
27
28 #include "memory/allocation.hpp"
29 #include "runtime/globals.hpp"
30 #include "runtime/os.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 class VTBufferChunk {
34 friend class VMStructs;
35
36 static const int MAGIC_NUMBER = 3141592;
37
38 private:
39 int _magic;
40 int _index;
41 VTBufferChunk* _prev;
42 VTBufferChunk* _next;
43 JavaThread* _owner;
44 public:
45
46 /* A VTBufferChunk is a 4KB page used to create a thread-local
47 * buffer to store values. They are allocated in a global pool,
48 * and then threads can get them to create their own buffer.
49 * Each thread creates a linked list of VTBufferChunk to build
50 * its buffer. Fields _prev and _next are used to link the
51 * chunks together, the _owner field indicates to which thread
52 * this chunk belongs to (if NULL, it means the chunk has been
53 * returned to the global pool). When creating the linked list,
54 * the field _index is used to store the position of the chunk
55 * in the list. The index is used to optimize the comparison
56 * of addresses of buffered values. Because the thread local
57 * buffer is made of non-contiguous chunks, it is not possible
58 * to directly compare the two addresses. The comparison requires
59 * first to compare the indexes of each address' chunk, and if
60 * they are equal, compare the addresses directly. Without
61 * the _index field, this operation would require to walk the
62 * linked list for each comparison.
63 */
64
65 VTBufferChunk(JavaThread* thread) {
66 fatal("Should not reach here");
67 VTBufferChunk::init(this, thread);
68 }
69
70 static void init(VTBufferChunk* chunk, JavaThread* thread) {
71 chunk->_magic = MAGIC_NUMBER;
72 chunk->_index = -1;
73 chunk->_prev = NULL;
74 chunk->_next = NULL;
75 chunk->_owner = thread;
76 }
77
78 int index() { return _index; }
79 void set_index(int index) { _index = index; }
80 VTBufferChunk* prev() { return _prev; }
81 void set_prev(VTBufferChunk* prev) { _prev = prev; }
82 VTBufferChunk* next() { return _next; }
83 void set_next(VTBufferChunk* next) { _next = next; }
84 JavaThread* owner() { return _owner; }
85 void set_owner(JavaThread* thread) {
86 assert(thread == NULL || _owner == NULL || _owner == thread, "Sanity check");
87 _owner = thread;
88 }
89
90 bool is_valid() {
91 return _magic == MAGIC_NUMBER && _owner != NULL && _index != -1;
92 }
93
94 void* first_alloc() { return (void*)((char*)this + align_object_size(sizeof (VTBufferChunk))); }
95 void* alloc_limit() { return (void*)((char*)this + chunk_size() - 1); }
96
97 static int chunk_size() {
98 return os::vm_page_size();
99 }
100
101 static uintptr_t chunk_mask() {
102 return ~(chunk_size() - 1);
103 }
104
105 static ByteSize index_offset() { return byte_offset_of(VTBufferChunk, _index); }
106
107 static size_t max_alloc_size() {
108 return chunk_size() - align_object_size(sizeof (VTBufferChunk));
109 }
110
111 static VTBufferChunk* chunk(void* address) {
112 VTBufferChunk* c = (VTBufferChunk*)((intptr_t)address & chunk_mask());
113 assert(c->is_valid(), "Sanity check");
114 return c;
115 }
116
117 bool contains(void* address) {
118 return address > (char*)chunk(address) && address < ((char*)chunk(address) + chunk_size());
119 }
120
121 void zap(void *start);
122 };
123
124 /* VTBuffer is a thread-local buffer used to store values, or TLVB (Thread-Local Value Buffer).
125 * Values allocated in the TLVB have the same layout as values allocated in the Java heap:
126 * same header size, same offsets for fields. The only difference is on the meaning of the
127 * mark word: in a buffered value, the mark word contains an oop pointing to the Java mirror
128 * of the value's class, with the two least significant bits used for internal marking.
129 * Values allocated in the TLVB are references through oops, however, because TLVBs are not
130 * part of the Java heap, those oops *must never be exposed to GCs*. But buffered values
131 * can contain references to Java heap allocated objects or values, in addition to the
132 * reference to the Java mirror, and these oops have to be processed by GC. The solution is
133 * to let GC closures iterate over the internal oops, but not directly on the buffered value
134 * itself (see ValueKlass::iterate_over_inside_oops() method).
135 */
136
137 class VTBuffer : AllStatic {
138 friend class VMStructs;
139 private:
140 static address _base;
141 static size_t _size;
142 static address _commit_ptr;
143
144 static VTBufferChunk* _free_list;
145 static Mutex* _pool_lock;
146 static int _pool_counter;
147 static int _max_pool_counter;
148 static int _total_allocated;
149 static int _total_failed;
150
151 public:
152 static void init();
153 static VTBufferChunk* get_new_chunk(JavaThread* thread);
154
155 static Mutex* lock() { return _pool_lock; }
156 static oop allocate_value(ValueKlass* k, TRAPS);
157 static bool allocate_vt_chunk(JavaThread* thread);
158 static void recycle_chunk(JavaThread* thread, VTBufferChunk* chunk);
159 static void return_vt_chunk(JavaThread* thread, VTBufferChunk* chunk);
160
161 static int in_pool() { return _pool_counter; }
162 static int max_in_pool() { return _max_pool_counter; }
163 static int total_allocated() { return _total_allocated; }
164 static int total_failed() { return _total_failed; }
165
166 static bool is_in_vt_buffer(const void* p) {
167 #ifdef ASSERT
168 if (p >= _base && p < (_base + _size)) {
169 assert(p < _commit_ptr, "should not point to an uncommited page");
170 intptr_t chunk_mask = (~(VTBufferChunk::chunk_size() - 1));
171 VTBufferChunk* c = (VTBufferChunk*)((intptr_t)p & chunk_mask);
172 assert(c->is_valid(), "Sanity check");
173 }
174 #endif // ASSERT
175 return p >= _base && p < (_base + _size);
176 }
177
178 static bool value_belongs_to_frame(oop p, frame *f);
179 static bool is_value_allocated_after(oop p, void* a);
180 static void recycle_vt_in_frame(JavaThread* thread, frame* f);
181 static void recycle_vtbuffer(JavaThread *thread, void* alloc_ptr);
182 static address relocate_value(address old, address previous, int previous_size_in_words);
183 static oop relocate_return_value(JavaThread* thread, void* alloc_ptr, oop old);
184
185 static void fix_frame_vt_alloc_ptr(frame fr, VTBufferChunk* chunk);
186
187 enum Mark {
188 mark_A = 1,
189 mark_B = 2,
190 mark_mask = 3
191 };
192
193 static Mark switch_mark(Mark m) {
194 assert(m == mark_A || m == mark_B, "Sanity check");
195 return m == mark_A ? mark_B : mark_A;
196 }
197
198 };
199
200 struct VT_relocation_entry {
201 int chunk_index;
202 address old_ptr;
203 address new_ptr;
204 markOop mark_word;
205 };
206
207
208 class BufferedValuesMarking : public BufferedValueClosure {
209 frame* _frame;
210 struct VT_relocation_entry* _reloc_table;
211 int _size;
212 int* _index;
213 public:
214 BufferedValuesMarking(frame* frame, struct VT_relocation_entry* reloc_table, int size, int* index) {
215 _frame = frame;
216 _reloc_table = reloc_table;
217 _size = size;
218 _index = index;
219 }
220 virtual void do_buffered_value(oop* p);
221 };
222
223 class BufferedValuesPointersUpdate : public BufferedValueClosure {
224 frame* _frame;
225 public:
226 BufferedValuesPointersUpdate(frame* frame) {
227 _frame = frame;
228 }
229 virtual void do_buffered_value(oop* p);
230 };
231
232 /* Value buffered in a TLVB expose their internal oops as roots for GCs.
233 * A GC root must only be processed once by each GC closure. However,
234 * a Java Thread can have multiple oops (aliases) pointing to the same
235 * buffered value (from local variable entries, operand stack slots,
236 * Handles or runtime data structures). To prevent duplicated processing
237 * of a buffered value, each function processing a Java Thread's GC roots
238 * must allocates a BufferedValuesDealiaser which uses a marking mechanism
239 * to avoid processing a buffered value twice.
240 */
241 class BufferedValuesDealiaser : public StackObj {
242 private:
243 const JavaThread* _target;
244 VTBuffer::Mark _current_mark;
245
246 public:
247 BufferedValuesDealiaser(JavaThread* thread);
248 VTBuffer::Mark current_mark() const { return _current_mark; }
249 void oops_do(OopClosure* f, oop value);
250
251 ~BufferedValuesDealiaser();
252 };
253
254 #endif /* SHARE_VM_MEMORY_VTBUFFER_HPP */