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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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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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/align.hpp"
30 #include "utilities/sizes.hpp"
31
32 // There are various techniques that require threads to be able to log
33 // addresses. For example, a generational write barrier might log
34 // the addresses of modified old-generation objects. This type supports
35 // this operation.
36
37 class BufferNode;
38 class PtrQueueSet;
39 class PtrQueue VALUE_OBJ_CLASS_SPEC {
40 friend class VMStructs;
41
42 // Noncopyable - not defined.
43 PtrQueue(const PtrQueue&);
44 PtrQueue& operator=(const PtrQueue&);
45
46 // The ptr queue set to which this queue belongs.
47 PtrQueueSet* const _qset;
48
49 // Whether updates should be logged.
50 bool _active;
51
52 // If true, the queue is permanent, and doesn't need to deallocate
53 // its buffer in the destructor (since that obtains a lock which may not
54 // be legally locked by then.
55 const bool _permanent;
56
57 // The (byte) index at which an object was last enqueued. Starts at
58 // capacity_in_bytes (indicating an empty buffer) and goes towards zero.
59 // Value is always pointer-size aligned.
60 size_t _index;
61
62 // Size of the current buffer, in bytes.
63 // Value is always pointer-size aligned.
64 size_t _capacity_in_bytes;
65
66 static const size_t _element_size = sizeof(void*);
67
68 // Get the capacity, in bytes. The capacity must have been set.
69 size_t capacity_in_bytes() const {
70 assert(_capacity_in_bytes > 0, "capacity not set");
71 return _capacity_in_bytes;
72 }
73
74 void set_capacity(size_t entries) {
75 size_t byte_capacity = index_to_byte_index(entries);
76 assert(_capacity_in_bytes == 0 || _capacity_in_bytes == byte_capacity,
77 "changing capacity " SIZE_FORMAT " -> " SIZE_FORMAT,
78 _capacity_in_bytes, byte_capacity);
79 _capacity_in_bytes = byte_capacity;
80 }
81
82 static size_t byte_index_to_index(size_t ind) {
83 assert(is_aligned(ind, _element_size), "precondition");
84 return ind / _element_size;
85 }
86
87 static size_t index_to_byte_index(size_t ind) {
88 return ind * _element_size;
89 }
90
91 protected:
92 // The buffer.
93 void** _buf;
94
95 size_t index() const {
96 return byte_index_to_index(_index);
97 }
98
99 void set_index(size_t new_index) {
100 size_t byte_index = index_to_byte_index(new_index);
101 assert(byte_index <= capacity_in_bytes(), "precondition");
102 _index = byte_index;
103 }
104
105 size_t capacity() const {
106 return byte_index_to_index(capacity_in_bytes());
107 }
108
109 // If there is a lock associated with this buffer, this is that lock.
110 Mutex* _lock;
111
112 PtrQueueSet* qset() { return _qset; }
113 bool is_permanent() const { return _permanent; }
114
115 // Process queue entries and release resources.
116 void flush_impl();
117
118 // Initialize this queue to contain a null buffer, and be part of the
119 // given PtrQueueSet.
120 PtrQueue(PtrQueueSet* qset, bool permanent = false, bool active = false);
121
122 // Requires queue flushed or permanent.
123 ~PtrQueue();
124
125 public:
126
127 // Associate a lock with a ptr queue.
128 void set_lock(Mutex* lock) { _lock = lock; }
129
130 // Forcibly set empty.
131 void reset() {
132 if (_buf != NULL) {
133 _index = capacity_in_bytes();
134 }
135 }
136
137 void enqueue(volatile void* ptr) {
138 enqueue((void*)(ptr));
139 }
140
141 // Enqueues the given "obj".
142 void enqueue(void* ptr) {
143 if (!_active) return;
144 else enqueue_known_active(ptr);
145 }
146
147 // This method is called when we're doing the zero index handling
148 // and gives a chance to the queues to do any pre-enqueueing
149 // processing they might want to do on the buffer. It should return
150 // true if the buffer should be enqueued, or false if enough
151 // entries were cleared from it so that it can be re-used. It should
152 // not return false if the buffer is still full (otherwise we can
153 // get into an infinite loop).
154 virtual bool should_enqueue_buffer() { return true; }
155 void handle_zero_index();
156 void locking_enqueue_completed_buffer(BufferNode* node);
157
158 void enqueue_known_active(void* ptr);
159
160 // Return the size of the in-use region.
161 size_t size() const {
162 size_t result = 0;
163 if (_buf != NULL) {
164 assert(_index <= capacity_in_bytes(), "Invariant");
165 result = byte_index_to_index(capacity_in_bytes() - _index);
166 }
167 return result;
168 }
169
170 bool is_empty() const {
171 return _buf == NULL || capacity_in_bytes() == _index;
172 }
173
174 // Set the "active" property of the queue to "b". An enqueue to an
175 // inactive thread is a no-op. Setting a queue to inactive resets its
176 // log to the empty state.
177 void set_active(bool b) {
178 _active = b;
179 if (!b && _buf != NULL) {
180 reset();
181 } else if (b && _buf != NULL) {
182 assert(index() == capacity(),
183 "invariant: queues are empty when activated.");
184 }
185 }
186
187 bool is_active() const { return _active; }
188
189 // To support compiler.
190
191 protected:
192 template<typename Derived>
193 static ByteSize byte_offset_of_index() {
194 return byte_offset_of(Derived, _index);
195 }
196
197 static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
198
199 template<typename Derived>
200 static ByteSize byte_offset_of_buf() {
201 return byte_offset_of(Derived, _buf);
202 }
203
204 static ByteSize byte_width_of_buf() { return in_ByteSize(_element_size); }
205
206 template<typename Derived>
207 static ByteSize byte_offset_of_active() {
208 return byte_offset_of(Derived, _active);
209 }
210
211 static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }
212
213 };
214
215 class BufferNode {
216 size_t _index;
217 BufferNode* _next;
218 void* _buffer[1]; // Pseudo flexible array member.
219
220 BufferNode() : _index(0), _next(NULL) { }
221 ~BufferNode() { }
222
223 static size_t buffer_offset() {
224 return offset_of(BufferNode, _buffer);
225 }
226
227 public:
228 BufferNode* next() const { return _next; }
229 void set_next(BufferNode* n) { _next = n; }
230 size_t index() const { return _index; }
231 void set_index(size_t i) { _index = i; }
232
233 // Allocate a new BufferNode with the "buffer" having size elements.
234 static BufferNode* allocate(size_t size);
235
236 // Free a BufferNode.
237 static void deallocate(BufferNode* node);
238
239 // Return the BufferNode containing the buffer, after setting its index.
240 static BufferNode* make_node_from_buffer(void** buffer, size_t index) {
241 BufferNode* node =
242 reinterpret_cast<BufferNode*>(
243 reinterpret_cast<char*>(buffer) - buffer_offset());
244 node->set_index(index);
245 return node;
246 }
247
248 // Return the buffer for node.
249 static void** make_buffer_from_node(BufferNode *node) {
250 // &_buffer[0] might lead to index out of bounds warnings.
251 return reinterpret_cast<void**>(
252 reinterpret_cast<char*>(node) + buffer_offset());
253 }
254 };
255
256 // A PtrQueueSet represents resources common to a set of pointer queues.
257 // In particular, the individual queues allocate buffers from this shared
258 // set, and return completed buffers to the set.
259 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
260 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
261 private:
262 // The size of all buffers in the set.
263 size_t _buffer_size;
264
265 protected:
266 Monitor* _cbl_mon; // Protects the fields below.
267 BufferNode* _completed_buffers_head;
268 BufferNode* _completed_buffers_tail;
269 size_t _n_completed_buffers;
270 int _process_completed_threshold;
271 volatile bool _process_completed;
272
273 // This (and the interpretation of the first element as a "next"
274 // pointer) are protected by the TLOQ_FL_lock.
275 Mutex* _fl_lock;
276 BufferNode* _buf_free_list;
277 size_t _buf_free_list_sz;
278 // Queue set can share a freelist. The _fl_owner variable
279 // specifies the owner. It is set to "this" by default.
280 PtrQueueSet* _fl_owner;
281
282 bool _all_active;
283
284 // If true, notify_all on _cbl_mon when the threshold is reached.
285 bool _notify_when_complete;
286
287 // Maximum number of elements allowed on completed queue: after that,
288 // enqueuer does the work itself. Zero indicates no maximum.
289 int _max_completed_queue;
290 size_t _completed_queue_padding;
291
292 size_t completed_buffers_list_length();
293 void assert_completed_buffer_list_len_correct_locked();
294 void assert_completed_buffer_list_len_correct();
295
296 protected:
297 // A mutator thread does the the work of processing a buffer.
298 // Returns "true" iff the work is complete (and the buffer may be
299 // deallocated).
300 virtual bool mut_process_buffer(BufferNode* node) {
301 ShouldNotReachHere();
302 return false;
303 }
304
305 // Create an empty ptr queue set.
306 PtrQueueSet(bool notify_when_complete = false);
307 ~PtrQueueSet();
308
309 // Because of init-order concerns, we can't pass these as constructor
310 // arguments.
311 void initialize(Monitor* cbl_mon,
312 Mutex* fl_lock,
313 int process_completed_threshold,
314 int max_completed_queue,
315 PtrQueueSet *fl_owner = NULL);
316
317 public:
318
319 // Return the buffer for a BufferNode of size buffer_size().
320 void** allocate_buffer();
321
322 // Return an empty buffer to the free list. The node is required
323 // to have been allocated with a size of buffer_size().
324 void deallocate_buffer(BufferNode* node);
325
326 // Declares that "buf" is a complete buffer.
327 void enqueue_complete_buffer(BufferNode* node);
328
329 // To be invoked by the mutator.
330 bool process_or_enqueue_complete_buffer(BufferNode* node);
331
332 bool completed_buffers_exist_dirty() {
333 return _n_completed_buffers > 0;
334 }
335
336 bool process_completed_buffers() { return _process_completed; }
337 void set_process_completed(bool x) { _process_completed = x; }
338
339 bool is_active() { return _all_active; }
340
341 // Set the buffer size. Should be called before any "enqueue" operation
342 // can be called. And should only be called once.
343 void set_buffer_size(size_t sz);
344
345 // Get the buffer size. Must have been set.
346 size_t buffer_size() const {
347 assert(_buffer_size > 0, "buffer size not set");
348 return _buffer_size;
349 }
350
351 // Get/Set the number of completed buffers that triggers log processing.
352 void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
353 int process_completed_threshold() const { return _process_completed_threshold; }
354
355 // Must only be called at a safe point. Indicates that the buffer free
356 // list size may be reduced, if that is deemed desirable.
357 void reduce_free_list();
358
359 size_t completed_buffers_num() { return _n_completed_buffers; }
360
361 void merge_bufferlists(PtrQueueSet* src);
362
363 void set_max_completed_queue(int m) { _max_completed_queue = m; }
364 int max_completed_queue() { return _max_completed_queue; }
365
366 void set_completed_queue_padding(size_t padding) { _completed_queue_padding = padding; }
367 size_t completed_queue_padding() { return _completed_queue_padding; }
368
369 // Notify the consumer if the number of buffers crossed the threshold
370 void notify_if_necessary();
371 };
372
373 #endif // SHARE_VM_GC_G1_PTRQUEUE_HPP