1 /*
2 * Copyright (c) 2001, 2015, 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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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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23 */
24
25 #ifndef SHARE_VM_GC_G1_PTRQUEUE_HPP
26 #define SHARE_VM_GC_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 // Noncopyable - not defined.
44 PtrQueue(const PtrQueue&);
45 PtrQueue& operator=(const PtrQueue&);
46
47 // The ptr queue set to which this queue belongs.
48 PtrQueueSet* const _qset;
49
50 // Whether updates should be logged.
51 bool _active;
52
53 // If true, the queue is permanent, and doesn't need to deallocate
54 // its buffer in the destructor (since that obtains a lock which may not
55 // be legally locked by then.
56 const bool _permanent;
57
58 protected:
59 // The buffer.
60 void** _buf;
61 // The (byte) index at which an object was last enqueued. Starts at "_sz"
62 // (indicating an empty buffer) and goes towards zero.
63 size_t _index;
64
65 // The (byte) size of the buffer.
66 size_t _sz;
67
68 // If there is a lock associated with this buffer, this is that lock.
69 Mutex* _lock;
70
71 PtrQueueSet* qset() { return _qset; }
72 bool is_permanent() const { return _permanent; }
73
74 // Process queue entries and release resources, if not permanent.
75 void flush_impl();
76
77 // Initialize this queue to contain a null buffer, and be part of the
78 // given PtrQueueSet.
79 PtrQueue(PtrQueueSet* qset, bool permanent = false, bool active = false);
80
81 // Requires queue flushed or permanent.
82 ~PtrQueue();
83
84 public:
85
86 // Associate a lock with a ptr queue.
87 void set_lock(Mutex* lock) { _lock = lock; }
88
89 void reset() { if (_buf != NULL) _index = _sz; }
90
91 void enqueue(volatile void* ptr) {
92 enqueue((void*)(ptr));
93 }
94
95 // Enqueues the given "obj".
96 void enqueue(void* ptr) {
97 if (!_active) return;
98 else enqueue_known_active(ptr);
99 }
100
101 // This method is called when we're doing the zero index handling
102 // and gives a chance to the queues to do any pre-enqueueing
103 // processing they might want to do on the buffer. It should return
104 // true if the buffer should be enqueued, or false if enough
105 // entries were cleared from it so that it can be re-used. It should
106 // not return false if the buffer is still full (otherwise we can
107 // get into an infinite loop).
108 virtual bool should_enqueue_buffer() { return true; }
109 void handle_zero_index();
110 void locking_enqueue_completed_buffer(void** buf);
111
112 void enqueue_known_active(void* ptr);
113
114 size_t size() {
115 assert(_sz >= _index, "Invariant.");
116 return _buf == NULL ? 0 : _sz - _index;
117 }
118
119 bool is_empty() {
120 return _buf == NULL || _sz == _index;
121 }
122
123 // Set the "active" property of the queue to "b". An enqueue to an
124 // inactive thread is a no-op. Setting a queue to inactive resets its
125 // log to the empty state.
126 void set_active(bool b) {
127 _active = b;
128 if (!b && _buf != NULL) {
129 _index = _sz;
130 } else if (b && _buf != NULL) {
131 assert(_index == _sz, "invariant: queues are empty when activated.");
132 }
133 }
134
135 bool is_active() { return _active; }
136
137 static size_t byte_index_to_index(size_t ind) {
138 assert((ind % sizeof(void*)) == 0, "Invariant.");
139 return ind / sizeof(void*);
140 }
141
142 // To support compiler.
143
144 protected:
145 template<typename Derived>
146 static ByteSize byte_offset_of_index() {
147 return byte_offset_of(Derived, _index);
148 }
149
150 static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
151
152 template<typename Derived>
153 static ByteSize byte_offset_of_buf() {
154 return byte_offset_of(Derived, _buf);
155 }
156
157 static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }
158
159 template<typename Derived>
160 static ByteSize byte_offset_of_active() {
161 return byte_offset_of(Derived, _active);
162 }
163
164 static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
165
166 };
167
168 class BufferNode {
169 size_t _index;
170 BufferNode* _next;
171 public:
172 BufferNode() : _index(0), _next(NULL) { }
173 BufferNode* next() const { return _next; }
174 void set_next(BufferNode* n) { _next = n; }
175 size_t index() const { return _index; }
176 void set_index(size_t i) { _index = i; }
177
178 // Align the size of the structure to the size of the pointer
179 static size_t aligned_size() {
180 static const size_t alignment = round_to(sizeof(BufferNode), sizeof(void*));
181 return alignment;
182 }
183
184 // BufferNode is allocated before the buffer.
185 // The chunk of memory that holds both of them is a block.
186
187 // Produce a new BufferNode given a buffer.
188 static BufferNode* new_from_buffer(void** buf) {
189 return new (make_block_from_buffer(buf)) BufferNode;
190 }
191
192 // The following are the required conversion routines:
193 static BufferNode* make_node_from_buffer(void** buf) {
194 return (BufferNode*)make_block_from_buffer(buf);
195 }
196 static void** make_buffer_from_node(BufferNode *node) {
197 return make_buffer_from_block(node);
198 }
199 static void* make_block_from_node(BufferNode *node) {
200 return (void*)node;
201 }
202 static void** make_buffer_from_block(void* p) {
203 return (void**)((char*)p + aligned_size());
204 }
205 static void* make_block_from_buffer(void** p) {
206 return (void*)((char*)p - aligned_size());
207 }
208 };
209
210 // A PtrQueueSet represents resources common to a set of pointer queues.
211 // In particular, the individual queues allocate buffers from this shared
212 // set, and return completed buffers to the set.
213 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
214 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
215 protected:
216 Monitor* _cbl_mon; // Protects the fields below.
217 BufferNode* _completed_buffers_head;
218 BufferNode* _completed_buffers_tail;
219 int _n_completed_buffers;
220 int _process_completed_threshold;
221 volatile bool _process_completed;
222
223 // This (and the interpretation of the first element as a "next"
224 // pointer) are protected by the TLOQ_FL_lock.
225 Mutex* _fl_lock;
226 BufferNode* _buf_free_list;
227 size_t _buf_free_list_sz;
228 // Queue set can share a freelist. The _fl_owner variable
229 // specifies the owner. It is set to "this" by default.
230 PtrQueueSet* _fl_owner;
231
232 // The size of all buffers in the set.
233 size_t _sz;
234
235 bool _all_active;
236
237 // If true, notify_all on _cbl_mon when the threshold is reached.
238 bool _notify_when_complete;
239
240 // Maximum number of elements allowed on completed queue: after that,
241 // enqueuer does the work itself. Zero indicates no maximum.
242 int _max_completed_queue;
243 int _completed_queue_padding;
244
245 int completed_buffers_list_length();
246 void assert_completed_buffer_list_len_correct_locked();
247 void assert_completed_buffer_list_len_correct();
248
249 protected:
250 // A mutator thread does the the work of processing a buffer.
251 // Returns "true" iff the work is complete (and the buffer may be
252 // deallocated).
253 virtual bool mut_process_buffer(void** buf) {
254 ShouldNotReachHere();
255 return false;
256 }
257
258 // Create an empty ptr queue set.
259 PtrQueueSet(bool notify_when_complete = false);
260 ~PtrQueueSet();
261
262 // Because of init-order concerns, we can't pass these as constructor
263 // arguments.
264 void initialize(Monitor* cbl_mon,
265 Mutex* fl_lock,
266 int process_completed_threshold,
267 int max_completed_queue,
268 PtrQueueSet *fl_owner = NULL);
269
270 public:
271
272 // Return an empty array of size _sz (required to be non-zero).
273 void** allocate_buffer();
274
275 // Return an empty buffer to the free list. The "buf" argument is
276 // required to be a pointer to the head of an array of length "_sz".
277 void deallocate_buffer(void** buf);
278
279 // Declares that "buf" is a complete buffer.
280 void enqueue_complete_buffer(void** buf, size_t index = 0);
281
282 // To be invoked by the mutator.
283 bool process_or_enqueue_complete_buffer(void** buf);
284
285 bool completed_buffers_exist_dirty() {
286 return _n_completed_buffers > 0;
287 }
288
289 bool process_completed_buffers() { return _process_completed; }
290 void set_process_completed(bool x) { _process_completed = x; }
291
292 bool is_active() { return _all_active; }
293
294 // Set the buffer size. Should be called before any "enqueue" operation
295 // can be called. And should only be called once.
296 void set_buffer_size(size_t sz);
297
298 // Get the buffer size.
299 size_t buffer_size() { return _sz; }
300
301 // Get/Set the number of completed buffers that triggers log processing.
302 void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
303 int process_completed_threshold() const { return _process_completed_threshold; }
304
305 // Must only be called at a safe point. Indicates that the buffer free
306 // list size may be reduced, if that is deemed desirable.
307 void reduce_free_list();
308
309 int completed_buffers_num() { return _n_completed_buffers; }
310
311 void merge_bufferlists(PtrQueueSet* src);
312
313 void set_max_completed_queue(int m) { _max_completed_queue = m; }
314 int max_completed_queue() { return _max_completed_queue; }
315
316 void set_completed_queue_padding(int padding) { _completed_queue_padding = padding; }
317 int completed_queue_padding() { return _completed_queue_padding; }
318
319 // Notify the consumer if the number of buffers crossed the threshold
320 void notify_if_necessary();
321 };
322
323 #endif // SHARE_VM_GC_G1_PTRQUEUE_HPP