1 /*
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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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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_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 class BufferNode;
37 class PtrQueueSet;
38 class PtrQueue VALUE_OBJ_CLASS_SPEC {
39 friend class VMStructs;
40
41 // Noncopyable - not defined.
42 PtrQueue(const PtrQueue&);
43 PtrQueue& operator=(const PtrQueue&);
44
45 // The ptr queue set to which this queue belongs.
46 PtrQueueSet* const _qset;
47
48 // Whether updates should be logged.
49 bool _active;
50
51 // If true, the queue is permanent, and doesn't need to deallocate
52 // its buffer in the destructor (since that obtains a lock which may not
53 // be legally locked by then.
54 const bool _permanent;
55
56 // The (byte) index at which an object was last enqueued. Starts at
57 // capacity_in_bytes (indicating an empty buffer) and goes towards zero.
58 // Value is always pointer-size aligned.
59 size_t _index;
60
61 // Size of the current buffer, in bytes.
62 // Value is always pointer-size aligned.
63 size_t _capacity_in_bytes;
64
65 static const size_t _element_size = sizeof(void*);
66
67 // Get the capacity, in bytes. The capacity must have been set.
68 size_t capacity_in_bytes() const {
69 assert(_capacity_in_bytes > 0, "capacity not set");
70 return _capacity_in_bytes;
71 }
72
73 void set_capacity(size_t entries) {
74 size_t byte_capacity = index_to_byte_index(entries);
75 assert(_capacity_in_bytes == 0 || _capacity_in_bytes == byte_capacity,
76 "changing capacity " SIZE_FORMAT " -> " SIZE_FORMAT,
77 _capacity_in_bytes, byte_capacity);
78 _capacity_in_bytes = byte_capacity;
79 }
80
81 static size_t byte_index_to_index(size_t ind) {
82 assert(is_aligned(ind, _element_size), "precondition");
83 return ind / _element_size;
84 }
85
86 static size_t index_to_byte_index(size_t ind) {
87 return ind * _element_size;
88 }
89
90 protected:
91 // The buffer.
92 void** _buf;
93
94 size_t index() const {
95 return byte_index_to_index(_index);
96 }
97
98 void set_index(size_t new_index) {
99 size_t byte_index = index_to_byte_index(new_index);
100 assert(byte_index <= capacity_in_bytes(), "precondition");
101 _index = byte_index;
102 }
103
104 size_t capacity() const {
105 return byte_index_to_index(capacity_in_bytes());
106 }
107
108 // If there is a lock associated with this buffer, this is that lock.
109 Mutex* _lock;
110
111 PtrQueueSet* qset() { return _qset; }
112 bool is_permanent() const { return _permanent; }
113
114 // Process queue entries and release resources.
115 void flush_impl();
116
117 // Initialize this queue to contain a null buffer, and be part of the
118 // given PtrQueueSet.
119 PtrQueue(PtrQueueSet* qset, bool permanent = false, bool active = false);
120
121 // Requires queue flushed or permanent.
122 ~PtrQueue();
123
124 public:
125
126 // Associate a lock with a ptr queue.
127 void set_lock(Mutex* lock) { _lock = lock; }
128
129 // Forcibly set empty.
130 void reset() {
131 if (_buf != NULL) {
132 _index = capacity_in_bytes();
133 }
134 }
135
136 void enqueue(volatile void* ptr) {
137 enqueue((void*)(ptr));
138 }
139
140 // Enqueues the given "obj".
141 void enqueue(void* ptr) {
142 if (!_active) return;
143 else enqueue_known_active(ptr);
144 }
145
146 // This method is called when we're doing the zero index handling
147 // and gives a chance to the queues to do any pre-enqueueing
148 // processing they might want to do on the buffer. It should return
149 // true if the buffer should be enqueued, or false if enough
150 // entries were cleared from it so that it can be re-used. It should
151 // not return false if the buffer is still full (otherwise we can
152 // get into an infinite loop).
153 virtual bool should_enqueue_buffer() { return true; }
154 void handle_zero_index();
155 void locking_enqueue_completed_buffer(BufferNode* node);
156
157 void enqueue_known_active(void* ptr);
158
159 // Return the size of the in-use region.
160 size_t size() const {
161 size_t result = 0;
162 if (_buf != NULL) {
163 assert(_index <= capacity_in_bytes(), "Invariant");
164 result = byte_index_to_index(capacity_in_bytes() - _index);
165 }
166 return result;
167 }
168
169 bool is_empty() const {
170 return _buf == NULL || capacity_in_bytes() == _index;
171 }
172
173 // Set the "active" property of the queue to "b". An enqueue to an
174 // inactive thread is a no-op. Setting a queue to inactive resets its
175 // log to the empty state.
176 void set_active(bool b) {
177 _active = b;
178 if (!b && _buf != NULL) {
179 reset();
180 } else if (b && _buf != NULL) {
181 assert(index() == capacity(),
182 "invariant: queues are empty when activated.");
183 }
184 }
185
186 bool is_active() const { return _active; }
187
188 // To support compiler.
189
190 protected:
191 template<typename Derived>
192 static ByteSize byte_offset_of_index() {
193 return byte_offset_of(Derived, _index);
194 }
195
196 static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
197
198 template<typename Derived>
199 static ByteSize byte_offset_of_buf() {
200 return byte_offset_of(Derived, _buf);
201 }
202
203 static ByteSize byte_width_of_buf() { return in_ByteSize(_element_size); }
204
205 template<typename Derived>
206 static ByteSize byte_offset_of_active() {
207 return byte_offset_of(Derived, _active);
208 }
209
210 static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
211
212 };
213
214 class BufferNode {
215 size_t _index;
216 BufferNode* _next;
217 void* _buffer[1]; // Pseudo flexible array member.
218
219 BufferNode() : _index(0), _next(NULL) { }
220 ~BufferNode() { }
221
222 static size_t buffer_offset() {
223 return offset_of(BufferNode, _buffer);
224 }
225
226 public:
227 BufferNode* next() const { return _next; }
228 void set_next(BufferNode* n) { _next = n; }
229 size_t index() const { return _index; }
230 void set_index(size_t i) { _index = i; }
231
232 // Allocate a new BufferNode with the "buffer" having size elements.
233 static BufferNode* allocate(size_t size);
234
235 // Free a BufferNode.
236 static void deallocate(BufferNode* node);
237
238 // Return the BufferNode containing the buffer, after setting its index.
239 static BufferNode* make_node_from_buffer(void** buffer, size_t index) {
240 BufferNode* node =
241 reinterpret_cast<BufferNode*>(
242 reinterpret_cast<char*>(buffer) - buffer_offset());
243 node->set_index(index);
244 return node;
245 }
246
247 // Return the buffer for node.
248 static void** make_buffer_from_node(BufferNode *node) {
249 // &_buffer[0] might lead to index out of bounds warnings.
250 return reinterpret_cast<void**>(
251 reinterpret_cast<char*>(node) + buffer_offset());
252 }
253 };
254
255 // A PtrQueueSet represents resources common to a set of pointer queues.
256 // In particular, the individual queues allocate buffers from this shared
257 // set, and return completed buffers to the set.
258 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
259 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
260 private:
261 // The size of all buffers in the set.
262 size_t _buffer_size;
263
264 protected:
265 Monitor* _cbl_mon; // Protects the fields below.
266 BufferNode* _completed_buffers_head;
267 BufferNode* _completed_buffers_tail;
268 size_t _n_completed_buffers;
269 int _process_completed_threshold;
270 volatile bool _process_completed;
271
272 // This (and the interpretation of the first element as a "next"
273 // pointer) are protected by the TLOQ_FL_lock.
274 Mutex* _fl_lock;
275 BufferNode* _buf_free_list;
276 size_t _buf_free_list_sz;
277 // Queue set can share a freelist. The _fl_owner variable
278 // specifies the owner. It is set to "this" by default.
279 PtrQueueSet* _fl_owner;
280
281 bool _all_active;
282
283 // If true, notify_all on _cbl_mon when the threshold is reached.
284 bool _notify_when_complete;
285
286 // Maximum number of elements allowed on completed queue: after that,
287 // enqueuer does the work itself. Zero indicates no maximum.
288 int _max_completed_queue;
289 size_t _completed_queue_padding;
290
291 size_t completed_buffers_list_length();
292 void assert_completed_buffer_list_len_correct_locked();
293 void assert_completed_buffer_list_len_correct();
294
295 protected:
296 // A mutator thread does the the work of processing a buffer.
297 // Returns "true" iff the work is complete (and the buffer may be
298 // deallocated).
299 virtual bool mut_process_buffer(BufferNode* node) {
300 ShouldNotReachHere();
301 return false;
302 }
303
304 // Create an empty ptr queue set.
305 PtrQueueSet(bool notify_when_complete = false);
306 ~PtrQueueSet();
307
308 // Because of init-order concerns, we can't pass these as constructor
309 // arguments.
310 void initialize(Monitor* cbl_mon,
311 Mutex* fl_lock,
312 int process_completed_threshold,
313 int max_completed_queue,
314 PtrQueueSet *fl_owner = NULL);
315
316 public:
317
318 // Return the buffer for a BufferNode of size buffer_size().
319 void** allocate_buffer();
320
321 // Return an empty buffer to the free list. The node is required
322 // to have been allocated with a size of buffer_size().
323 void deallocate_buffer(BufferNode* node);
324
325 // Declares that "buf" is a complete buffer.
326 void enqueue_complete_buffer(BufferNode* node);
327
328 // To be invoked by the mutator.
329 bool process_or_enqueue_complete_buffer(BufferNode* node);
330
331 bool completed_buffers_exist_dirty() {
332 return _n_completed_buffers > 0;
333 }
334
335 bool process_completed_buffers() { return _process_completed; }
336 void set_process_completed(bool x) { _process_completed = x; }
337
338 bool is_active() { return _all_active; }
339
340 // Set the buffer size. Should be called before any "enqueue" operation
341 // can be called. And should only be called once.
342 void set_buffer_size(size_t sz);
343
344 // Get the buffer size. Must have been set.
345 size_t buffer_size() const {
346 assert(_buffer_size > 0, "buffer size not set");
347 return _buffer_size;
348 }
349
350 // Get/Set the number of completed buffers that triggers log processing.
351 void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
352 int process_completed_threshold() const { return _process_completed_threshold; }
353
354 // Must only be called at a safe point. Indicates that the buffer free
355 // list size may be reduced, if that is deemed desirable.
356 void reduce_free_list();
357
358 size_t completed_buffers_num() { return _n_completed_buffers; }
359
360 void merge_bufferlists(PtrQueueSet* src);
361
362 void set_max_completed_queue(int m) { _max_completed_queue = m; }
363 int max_completed_queue() { return _max_completed_queue; }
364
365 void set_completed_queue_padding(size_t padding) { _completed_queue_padding = padding; }
366 size_t completed_queue_padding() { return _completed_queue_padding; }
367
368 // Notify the consumer if the number of buffers crossed the threshold
369 void notify_if_necessary();
370 };
371
372 #endif // SHARE_VM_GC_G1_PTRQUEUE_HPP