1 /*
2 * Copyright (c) 2001, 2012, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/sizes.hpp"
30
31 // There are various techniques that require threads to be able to log
32 // addresses. For example, a generational write barrier might log
33 // the addresses of modified old-generation objects. This type supports
34 // this operation.
35
36 // The definition of placement operator new(size_t, void*) in the <new>.
37 #include <new>
38
39 class PtrQueueSet;
40 class PtrQueue VALUE_OBJ_CLASS_SPEC {
41 friend class VMStructs;
42
43 protected:
44 // The ptr queue set to which this queue belongs.
45 PtrQueueSet* _qset;
46
47 // Whether updates should be logged.
48 bool _active;
49
50 // The buffer.
51 void** _buf;
52 // The index at which an object was last enqueued. Starts at "_sz"
53 // (indicating an empty buffer) and goes towards zero.
54 size_t _index;
55
56 // The size of the buffer.
57 size_t _sz;
58
59 // If true, the queue is permanent, and doesn't need to deallocate
60 // its buffer in the destructor (since that obtains a lock which may not
61 // be legally locked by then.
62 bool _perm;
63
64 // If there is a lock associated with this buffer, this is that lock.
65 Mutex* _lock;
66
67 PtrQueueSet* qset() { return _qset; }
68
69 public:
70 // Initialize this queue to contain a null buffer, and be part of the
71 // given PtrQueueSet.
72 PtrQueue(PtrQueueSet* qset, bool perm = false, bool active = false);
73 // Release any contained resources.
74 virtual void flush();
75 // Calls flush() when destroyed.
76 ~PtrQueue() { flush(); }
77
78 // Associate a lock with a ptr queue.
79 void set_lock(Mutex* lock) { _lock = lock; }
80
81 void reset() { if (_buf != NULL) _index = _sz; }
82
83 // Enqueues the given "obj".
84 void enqueue(void* ptr) {
85 if (!_active) return;
86 else enqueue_known_active(ptr);
87 }
88
89 // This method is called when we're doing the zero index handling
90 // and gives a chance to the queues to do any pre-enqueueing
91 // processing they might want to do on the buffer. It should return
92 // true if the buffer should be enqueued, or false if enough
93 // entries were cleared from it so that it can be re-used. It should
94 // not return false if the buffer is still full (otherwise we can
95 // get into an infinite loop).
96 virtual bool should_enqueue_buffer() { return true; }
97 void handle_zero_index();
98 void locking_enqueue_completed_buffer(void** buf);
99
100 void enqueue_known_active(void* ptr);
101
102 size_t size() {
103 assert(_sz >= _index, "Invariant.");
104 return _buf == NULL ? 0 : _sz - _index;
105 }
106
107 bool is_empty() {
108 return _buf == NULL || _sz == _index;
109 }
110
111 // Set the "active" property of the queue to "b". An enqueue to an
112 // inactive thread is a no-op. Setting a queue to inactive resets its
113 // log to the empty state.
114 void set_active(bool b) {
115 _active = b;
116 if (!b && _buf != NULL) {
117 _index = _sz;
118 } else if (b && _buf != NULL) {
119 assert(_index == _sz, "invariant: queues are empty when activated.");
120 }
121 }
122
123 bool is_active() { return _active; }
124
125 static int byte_index_to_index(int ind) {
126 assert((ind % oopSize) == 0, "Invariant.");
127 return ind / oopSize;
128 }
129
130 static int index_to_byte_index(int byte_ind) {
131 return byte_ind * oopSize;
132 }
133
134 // To support compiler.
135 static ByteSize byte_offset_of_index() {
136 return byte_offset_of(PtrQueue, _index);
137 }
138 static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
139
140 static ByteSize byte_offset_of_buf() {
141 return byte_offset_of(PtrQueue, _buf);
142 }
143 static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }
144
145 static ByteSize byte_offset_of_active() {
146 return byte_offset_of(PtrQueue, _active);
147 }
148 static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
149
150 };
151
152 class BufferNode {
153 size_t _index;
154 BufferNode* _next;
155 public:
156 BufferNode() : _index(0), _next(NULL) { }
157 BufferNode* next() const { return _next; }
158 void set_next(BufferNode* n) { _next = n; }
159 size_t index() const { return _index; }
160 void set_index(size_t i) { _index = i; }
161
162 // Align the size of the structure to the size of the pointer
163 static size_t aligned_size() {
164 static const size_t alignment = round_to(sizeof(BufferNode), sizeof(void*));
165 return alignment;
166 }
167
168 // BufferNode is allocated before the buffer.
169 // The chunk of memory that holds both of them is a block.
170
171 // Produce a new BufferNode given a buffer.
172 static BufferNode* new_from_buffer(void** buf) {
173 return new (make_block_from_buffer(buf)) BufferNode;
174 }
175
176 // The following are the required conversion routines:
177 static BufferNode* make_node_from_buffer(void** buf) {
178 return (BufferNode*)make_block_from_buffer(buf);
179 }
180 static void** make_buffer_from_node(BufferNode *node) {
181 return make_buffer_from_block(node);
182 }
183 static void* make_block_from_node(BufferNode *node) {
184 return (void*)node;
185 }
186 static void** make_buffer_from_block(void* p) {
187 return (void**)((char*)p + aligned_size());
188 }
189 static void* make_block_from_buffer(void** p) {
190 return (void*)((char*)p - aligned_size());
191 }
192 };
193
194 // A PtrQueueSet represents resources common to a set of pointer queues.
195 // In particular, the individual queues allocate buffers from this shared
196 // set, and return completed buffers to the set.
197 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
198 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
199 protected:
200 Monitor* _cbl_mon; // Protects the fields below.
201 BufferNode* _completed_buffers_head;
202 BufferNode* _completed_buffers_tail;
203 int _n_completed_buffers;
204 int _process_completed_threshold;
205 volatile bool _process_completed;
206
207 // This (and the interpretation of the first element as a "next"
208 // pointer) are protected by the TLOQ_FL_lock.
209 Mutex* _fl_lock;
210 BufferNode* _buf_free_list;
211 size_t _buf_free_list_sz;
212 // Queue set can share a freelist. The _fl_owner variable
213 // specifies the owner. It is set to "this" by default.
214 PtrQueueSet* _fl_owner;
215
216 // The size of all buffers in the set.
217 size_t _sz;
218
219 bool _all_active;
220
221 // If true, notify_all on _cbl_mon when the threshold is reached.
222 bool _notify_when_complete;
223
224 // Maximum number of elements allowed on completed queue: after that,
225 // enqueuer does the work itself. Zero indicates no maximum.
226 int _max_completed_queue;
227 int _completed_queue_padding;
228
229 int completed_buffers_list_length();
230 void assert_completed_buffer_list_len_correct_locked();
231 void assert_completed_buffer_list_len_correct();
232
233 protected:
234 // A mutator thread does the the work of processing a buffer.
235 // Returns "true" iff the work is complete (and the buffer may be
236 // deallocated).
237 virtual bool mut_process_buffer(void** buf) {
238 ShouldNotReachHere();
239 return false;
240 }
241
242 public:
243 // Create an empty ptr queue set.
244 PtrQueueSet(bool notify_when_complete = false);
245
246 // Because of init-order concerns, we can't pass these as constructor
247 // arguments.
248 void initialize(Monitor* cbl_mon, Mutex* fl_lock,
249 int process_completed_threshold,
250 int max_completed_queue,
251 PtrQueueSet *fl_owner = NULL) {
252 _max_completed_queue = max_completed_queue;
253 _process_completed_threshold = process_completed_threshold;
254 _completed_queue_padding = 0;
255 assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
256 _cbl_mon = cbl_mon;
257 _fl_lock = fl_lock;
258 _fl_owner = (fl_owner != NULL) ? fl_owner : this;
259 }
260
261 // Return an empty oop array of size _sz (required to be non-zero).
262 void** allocate_buffer();
263
264 // Return an empty buffer to the free list. The "buf" argument is
265 // required to be a pointer to the head of an array of length "_sz".
266 void deallocate_buffer(void** buf);
267
268 // Declares that "buf" is a complete buffer.
269 void enqueue_complete_buffer(void** buf, size_t index = 0);
270
271 // To be invoked by the mutator.
272 bool process_or_enqueue_complete_buffer(void** buf);
273
274 bool completed_buffers_exist_dirty() {
275 return _n_completed_buffers > 0;
276 }
277
278 bool process_completed_buffers() { return _process_completed; }
279 void set_process_completed(bool x) { _process_completed = x; }
280
281 bool is_active() { return _all_active; }
282
283 // Set the buffer size. Should be called before any "enqueue" operation
284 // can be called. And should only be called once.
285 void set_buffer_size(size_t sz);
286
287 // Get the buffer size.
288 size_t buffer_size() { return _sz; }
289
290 // Get/Set the number of completed buffers that triggers log processing.
291 void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
292 int process_completed_threshold() const { return _process_completed_threshold; }
293
294 // Must only be called at a safe point. Indicates that the buffer free
295 // list size may be reduced, if that is deemed desirable.
296 void reduce_free_list();
297
298 int completed_buffers_num() { return _n_completed_buffers; }
299
300 void merge_bufferlists(PtrQueueSet* src);
301
302 void set_max_completed_queue(int m) { _max_completed_queue = m; }
303 int max_completed_queue() { return _max_completed_queue; }
304
305 void set_completed_queue_padding(int padding) { _completed_queue_padding = padding; }
306 int completed_queue_padding() { return _completed_queue_padding; }
307
308 // Notify the consumer if the number of buffers crossed the threshold
309 void notify_if_necessary();
310 };
311
312 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP