1 /*
2 * Copyright (c) 2001, 2018, 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_GC_SHARED_PTRQUEUE_HPP
26 #define SHARE_GC_SHARED_PTRQUEUE_HPP
27
28 #include "utilities/align.hpp"
29 #include "utilities/sizes.hpp"
30
31 class Mutex;
32
33 // There are various techniques that require threads to be able to log
34 // addresses. For example, a generational write barrier might log
35 // the addresses of modified old-generation objects. This type supports
36 // this operation.
37
38 class BufferNode;
39 class PtrQueueSet;
40 class PtrQueue {
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 // The (byte) index at which an object was last enqueued. Starts at
59 // capacity_in_bytes (indicating an empty buffer) and goes towards zero.
60 // Value is always pointer-size aligned.
61 size_t _index;
62
63 // Size of the current buffer, in bytes.
64 // Value is always pointer-size aligned.
65 size_t _capacity_in_bytes;
66
67 static const size_t _element_size = sizeof(void*);
68
69 // Get the capacity, in bytes. The capacity must have been set.
70 size_t capacity_in_bytes() const {
71 assert(_capacity_in_bytes > 0, "capacity not set");
72 return _capacity_in_bytes;
73 }
74
75 void set_capacity(size_t entries) {
76 size_t byte_capacity = index_to_byte_index(entries);
77 assert(_capacity_in_bytes == 0 || _capacity_in_bytes == byte_capacity,
78 "changing capacity " SIZE_FORMAT " -> " SIZE_FORMAT,
79 _capacity_in_bytes, byte_capacity);
80 _capacity_in_bytes = byte_capacity;
81 }
82
83 static size_t byte_index_to_index(size_t ind) {
84 assert(is_aligned(ind, _element_size), "precondition");
85 return ind / _element_size;
86 }
87
88 static size_t index_to_byte_index(size_t ind) {
89 return ind * _element_size;
90 }
91
92 protected:
93 // The buffer.
94 void** _buf;
95
96 size_t index() const {
97 return byte_index_to_index(_index);
98 }
99
100 void set_index(size_t new_index) {
101 size_t byte_index = index_to_byte_index(new_index);
102 assert(byte_index <= capacity_in_bytes(), "precondition");
103 _index = byte_index;
104 }
105
106 size_t capacity() const {
107 return byte_index_to_index(capacity_in_bytes());
108 }
109
110 // If there is a lock associated with this buffer, this is that lock.
111 Mutex* _lock;
112
113 PtrQueueSet* qset() { return _qset; }
114 bool is_permanent() const { return _permanent; }
115
116 // Process queue entries and release resources.
117 void flush_impl();
118
119 // Initialize this queue to contain a null buffer, and be part of the
120 // given PtrQueueSet.
121 PtrQueue(PtrQueueSet* qset, bool permanent = false, bool active = false);
122
123 // Requires queue flushed or permanent.
124 ~PtrQueue();
125
126 public:
127
128 // Associate a lock with a ptr queue.
129 void set_lock(Mutex* lock) { _lock = lock; }
130
131 // Forcibly set empty.
132 void reset() {
133 if (_buf != NULL) {
134 _index = capacity_in_bytes();
135 }
136 }
137
138 void enqueue(volatile void* ptr) {
139 enqueue((void*)(ptr));
140 }
141
142 // Enqueues the given "obj".
143 void enqueue(void* ptr) {
144 if (!_active) return;
145 else enqueue_known_active(ptr);
146 }
147
148 // This method is called when we're doing the zero index handling
149 // and gives a chance to the queues to do any pre-enqueueing
150 // processing they might want to do on the buffer. It should return
151 // true if the buffer should be enqueued, or false if enough
152 // entries were cleared from it so that it can be re-used. It should
153 // not return false if the buffer is still full (otherwise we can
154 // get into an infinite loop).
155 virtual bool should_enqueue_buffer() { return true; }
156 void handle_zero_index();
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 AIX_ONLY(public:) // xlC 12 on AIX doesn't implement C++ DR45.
228 // Allocate a new BufferNode with the "buffer" having size elements.
229 static BufferNode* allocate(size_t size);
230
231 // Free a BufferNode.
232 static void deallocate(BufferNode* node);
233
234 public:
235 BufferNode* next() const { return _next; }
236 void set_next(BufferNode* n) { _next = n; }
237 size_t index() const { return _index; }
238 void set_index(size_t i) { _index = i; }
239
240 // Return the BufferNode containing the buffer, after setting its index.
241 static BufferNode* make_node_from_buffer(void** buffer, size_t index) {
242 BufferNode* node =
243 reinterpret_cast<BufferNode*>(
244 reinterpret_cast<char*>(buffer) - buffer_offset());
245 node->set_index(index);
246 return node;
247 }
248
249 // Return the buffer for node.
250 static void** make_buffer_from_node(BufferNode *node) {
251 // &_buffer[0] might lead to index out of bounds warnings.
252 return reinterpret_cast<void**>(
253 reinterpret_cast<char*>(node) + buffer_offset());
254 }
255
256 // Free-list based allocator.
257 class Allocator {
258 size_t _buffer_size;
259 Mutex* _lock;
260 BufferNode* _free_list;
261 volatile size_t _free_count;
262
263 public:
264 Allocator(size_t buffer_size, Mutex* lock);
265 ~Allocator();
266
267 size_t buffer_size() const { return _buffer_size; }
268 size_t free_count() const;
269 BufferNode* allocate();
270 void release(BufferNode* node);
271 void reduce_free_list();
272 };
273 };
274
275 // A PtrQueueSet represents resources common to a set of pointer queues.
276 // In particular, the individual queues allocate buffers from this shared
277 // set, and return completed buffers to the set.
278 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???
279 class PtrQueueSet {
280 BufferNode::Allocator* _allocator;
281
282 protected:
283 Monitor* _cbl_mon; // Protects the fields below.
284 BufferNode* _completed_buffers_head;
285 BufferNode* _completed_buffers_tail;
286 size_t _n_completed_buffers;
287 int _process_completed_threshold;
288 volatile bool _process_completed;
289
290 bool _all_active;
291
292 // If true, notify_all on _cbl_mon when the threshold is reached.
293 bool _notify_when_complete;
294
295 // Maximum number of elements allowed on completed queue: after that,
296 // enqueuer does the work itself. Zero indicates no maximum.
297 int _max_completed_queue;
298 size_t _completed_queue_padding;
299
300 size_t completed_buffers_list_length();
301 void assert_completed_buffer_list_len_correct_locked();
302 void assert_completed_buffer_list_len_correct();
303
304 protected:
305 // A mutator thread does the the work of processing a buffer.
306 // Returns "true" iff the work is complete (and the buffer may be
307 // deallocated).
308 virtual bool mut_process_buffer(BufferNode* node) {
309 ShouldNotReachHere();
310 return false;
311 }
312
313 // Create an empty ptr queue set.
314 PtrQueueSet(bool notify_when_complete = false);
315 ~PtrQueueSet();
316
317 // Because of init-order concerns, we can't pass these as constructor
318 // arguments.
319 void initialize(Monitor* cbl_mon,
320 BufferNode::Allocator* allocator,
321 int process_completed_threshold,
322 int max_completed_queue);
323
324 public:
325
326 // Return the buffer for a BufferNode of size buffer_size().
327 void** allocate_buffer();
328
329 // Return an empty buffer to the free list. The node is required
330 // to have been allocated with a size of buffer_size().
331 void deallocate_buffer(BufferNode* node);
332
333 // Declares that "buf" is a complete buffer.
334 void enqueue_complete_buffer(BufferNode* node);
335
336 // To be invoked by the mutator.
337 bool process_or_enqueue_complete_buffer(BufferNode* node);
338
339 bool completed_buffers_exist_dirty() {
340 return _n_completed_buffers > 0;
341 }
342
343 bool process_completed_buffers() { return _process_completed; }
344 void set_process_completed(bool x) { _process_completed = x; }
345
346 bool is_active() { return _all_active; }
347
348 size_t buffer_size() const {
349 return _allocator->buffer_size();
350 }
351
352 // Get/Set the number of completed buffers that triggers log processing.
353 void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }
354 int process_completed_threshold() const { return _process_completed_threshold; }
355
356 size_t completed_buffers_num() { return _n_completed_buffers; }
357
358 void merge_bufferlists(PtrQueueSet* src);
359
360 void set_max_completed_queue(int m) { _max_completed_queue = m; }
361 int max_completed_queue() { return _max_completed_queue; }
362
363 void set_completed_queue_padding(size_t padding) { _completed_queue_padding = padding; }
364 size_t completed_queue_padding() { return _completed_queue_padding; }
365
366 // Notify the consumer if the number of buffers crossed the threshold
367 void notify_if_necessary();
368 };
369
370 #endif // SHARE_GC_SHARED_PTRQUEUE_HPP