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.
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 #include "precompiled.hpp"
26 #include "gc/g1/g1CollectedHeap.inline.hpp"
27 #include "gc/g1/satbQueue.hpp"
28 #include "gc/shared/collectedHeap.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/mutexLocker.hpp"
32 #include "runtime/safepoint.hpp"
33 #include "runtime/thread.hpp"
34 #include "runtime/vmThread.hpp"
35
36 void ObjPtrQueue::flush() {
37 // Filter now to possibly save work later. If filtering empties the
38 // buffer then flush_impl can deallocate the buffer.
39 filter();
40 flush_impl();
41 }
42
43 // Return true if a SATB buffer entry refers to an object that
44 // requires marking.
45 //
46 // The entry must point into the G1 heap. In particular, it must not
47 // be a NULL pointer. NULL pointers are pre-filtered and never
48 // inserted into a SATB buffer.
49 //
50 // An entry that is below the NTAMS pointer for the containing heap
51 // region requires marking. Such an entry must point to a valid object.
52 //
53 // An entry that is at least the NTAMS pointer for the containing heap
54 // region might be any of the following, none of which should be marked.
55 //
56 // * A reference to an object allocated since marking started.
57 // According to SATB, such objects are implicitly kept live and do
58 // not need to be dealt with via SATB buffer processing.
59 //
60 // * A reference to a young generation object. Young objects are
61 // handled separately and are not marked by concurrent marking.
62 //
63 // * A stale reference to a young generation object. If a young
64 // generation object reference is recorded and not filtered out
65 // before being moved by a young collection, the reference becomes
66 // stale.
67 //
68 // * A stale reference to an eagerly reclaimed humongous object. If a
69 // humongous object is recorded and then reclaimed, the reference
70 // becomes stale.
71 //
72 // The stale reference cases are implicitly handled by the NTAMS
73 // comparison. Because of the possibility of stale references, buffer
74 // processing must be somewhat circumspect and not assume entries
75 // in an unfiltered buffer refer to valid objects.
76
77 // This method removes entries from a SATB buffer that will not be
78 // useful to the concurrent marking threads. Entries are retained if
79 // they require marking and are not already marked. Retained entries
80 // are compacted toward the top of the buffer.
81
82 void ObjPtrQueue::filter() {
83 CollectedHeap* heap = Universe::heap();
84 void** buf = _buf;
85 size_t sz = _sz;
86
87 if (buf == NULL) {
88 // nothing to do
89 return;
90 }
91
92 // Used for sanity checking at the end of the loop.
93 debug_only(size_t entries = 0; size_t retained = 0;)
94
95 size_t i = sz;
96 size_t new_index = sz;
97
98 while (i > _index) {
99 assert(i > 0, "we should have at least one more entry to process");
100 i -= oopSize;
101 debug_only(entries += 1;)
102 void** p = &buf[byte_index_to_index((int) i)];
103 void* entry = *p;
104 // NULL the entry so that unused parts of the buffer contain NULLs
105 // at the end. If we are going to retain it we will copy it to its
106 // final place. If we have retained all entries we have visited so
107 // far, we'll just end up copying it to the same place.
108 *p = NULL;
109
110 bool retain = heap->is_obj_ill(oop(entry));
111 if (retain) {
112 assert(new_index > 0, "we should not have already filled up the buffer");
113 new_index -= oopSize;
114 assert(new_index >= i,
115 "new_index should never be below i, as we always compact 'up'");
116 void** new_p = &buf[byte_index_to_index((int) new_index)];
117 assert(new_p >= p, "the destination location should never be below "
118 "the source as we always compact 'up'");
119 assert(*new_p == NULL,
120 "we should have already cleared the destination location");
121 *new_p = entry;
122 debug_only(retained += 1;)
123 }
124 }
125
126 #ifdef ASSERT
127 size_t entries_calc = (sz - _index) / oopSize;
128 assert(entries == entries_calc, "the number of entries we counted "
129 "should match the number of entries we calculated");
130 size_t retained_calc = (sz - new_index) / oopSize;
131 assert(retained == retained_calc, "the number of retained entries we counted "
132 "should match the number of retained entries we calculated");
133 #endif // ASSERT
134
135 _index = new_index;
136 }
137
138 // This method will first apply the above filtering to the buffer. If
139 // post-filtering a large enough chunk of the buffer has been cleared
140 // we can re-use the buffer (instead of enqueueing it) and we can just
141 // allow the mutator to carry on executing using the same buffer
142 // instead of replacing it.
143
144 bool ObjPtrQueue::should_enqueue_buffer() {
145 assert(_lock == NULL || _lock->owned_by_self(),
146 "we should have taken the lock before calling this");
147
148 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
149
150 // This method should only be called if there is a non-NULL buffer
151 // that is full.
152 assert(_index == 0, "pre-condition");
153 assert(_buf != NULL, "pre-condition");
154
155 filter();
156
157 size_t sz = _sz;
158 size_t all_entries = sz / oopSize;
159 size_t retained_entries = (sz - _index) / oopSize;
160 size_t perc = retained_entries * 100 / all_entries;
161 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
162 return should_enqueue;
163 }
164
165 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
166 assert(SafepointSynchronize::is_at_safepoint(),
167 "SATB queues must only be processed at safepoints");
168 if (_buf != NULL) {
169 assert(_index % sizeof(void*) == 0, "invariant");
170 assert(_sz % sizeof(void*) == 0, "invariant");
171 assert(_index <= _sz, "invariant");
172 cl->do_buffer(_buf + byte_index_to_index((int)_index),
173 byte_index_to_index((int)(_sz - _index)));
174 _index = _sz;
175 }
176 }
177
178 #ifndef PRODUCT
179 // Helpful for debugging
180
181 void ObjPtrQueue::print(const char* name) {
182 print(name, _buf, _index, _sz);
183 }
184
185 void ObjPtrQueue::print(const char* name,
186 void** buf, size_t index, size_t sz) {
187 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " "
188 "index: " SIZE_FORMAT " sz: " SIZE_FORMAT,
189 name, p2i(buf), index, sz);
190 }
191 #endif // PRODUCT
192
193 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
194 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
195 #endif // _MSC_VER
196
197 SATBMarkQueueSet::SATBMarkQueueSet() :
198 PtrQueueSet(),
199 _shared_satb_queue(this, true /*perm*/) { }
200
201 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
202 int process_completed_threshold,
203 Mutex* lock) {
204 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
205 _shared_satb_queue.set_lock(lock);
206 }
207
208 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
209 t->satb_mark_queue().handle_zero_index();
210 }
211
212 #ifdef ASSERT
213 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
214 gclog_or_tty->print_cr("Expected SATB active state: %s",
215 expected_active ? "ACTIVE" : "INACTIVE");
216 gclog_or_tty->print_cr("Actual SATB active states:");
217 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
218 for (JavaThread* t = Threads::first(); t; t = t->next()) {
219 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
220 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
221 }
222 gclog_or_tty->print_cr(" Shared queue: %s",
223 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
224 }
225
226 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
227 // Verify queue set state
228 if (is_active() != expected_active) {
229 dump_active_states(expected_active);
230 guarantee(false, "SATB queue set has an unexpected active state");
231 }
232
233 // Verify thread queue states
234 for (JavaThread* t = Threads::first(); t; t = t->next()) {
235 if (t->satb_mark_queue().is_active() != expected_active) {
236 dump_active_states(expected_active);
237 guarantee(false, "Thread SATB queue has an unexpected active state");
238 }
239 }
240
241 // Verify shared queue state
242 if (shared_satb_queue()->is_active() != expected_active) {
243 dump_active_states(expected_active);
244 guarantee(false, "Shared SATB queue has an unexpected active state");
245 }
246 }
247 #endif // ASSERT
248
249 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
250 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
251 #ifdef ASSERT
252 verify_active_states(expected_active);
253 #endif // ASSERT
254 _all_active = active;
255 for (JavaThread* t = Threads::first(); t; t = t->next()) {
256 t->satb_mark_queue().set_active(active);
257 }
258 shared_satb_queue()->set_active(active);
259 }
260
261 void SATBMarkQueueSet::filter_thread_buffers() {
262 for(JavaThread* t = Threads::first(); t; t = t->next()) {
263 t->satb_mark_queue().filter();
264 }
265 shared_satb_queue()->filter();
266 }
267
268 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
269 BufferNode* nd = NULL;
270 {
271 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
272 if (_completed_buffers_head != NULL) {
273 nd = _completed_buffers_head;
274 _completed_buffers_head = nd->next();
275 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
276 _n_completed_buffers--;
277 if (_n_completed_buffers == 0) _process_completed = false;
278 }
279 }
280 if (nd != NULL) {
281 void **buf = BufferNode::make_buffer_from_node(nd);
282 // Skip over NULL entries at beginning (e.g. push end) of buffer.
283 // Filtering can result in non-full completed buffers; see
284 // should_enqueue_buffer.
285 assert(_sz % sizeof(void*) == 0, "invariant");
286 size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);
287 for (size_t i = 0; i < limit; ++i) {
288 if (buf[i] != NULL) {
289 // Found the end of the block of NULLs; process the remainder.
290 cl->do_buffer(buf + i, limit - i);
291 break;
292 }
293 }
294 deallocate_buffer(buf);
295 return true;
296 } else {
297 return false;
298 }
299 }
300
301 #ifndef PRODUCT
302 // Helpful for debugging
303
304 #define SATB_PRINTER_BUFFER_SIZE 256
305
306 void SATBMarkQueueSet::print_all(const char* msg) {
307 char buffer[SATB_PRINTER_BUFFER_SIZE];
308 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
309
310 gclog_or_tty->cr();
311 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
312
313 BufferNode* nd = _completed_buffers_head;
314 int i = 0;
315 while (nd != NULL) {
316 void** buf = BufferNode::make_buffer_from_node(nd);
317 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
318 ObjPtrQueue::print(buffer, buf, 0, _sz);
319 nd = nd->next();
320 i += 1;
321 }
322
323 for (JavaThread* t = Threads::first(); t; t = t->next()) {
324 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
325 t->satb_mark_queue().print(buffer);
326 }
327
328 shared_satb_queue()->print("Shared");
329
330 gclog_or_tty->cr();
331 }
332 #endif // PRODUCT
333
334 void SATBMarkQueueSet::abandon_partial_marking() {
335 BufferNode* buffers_to_delete = NULL;
336 {
337 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
338 while (_completed_buffers_head != NULL) {
339 BufferNode* nd = _completed_buffers_head;
340 _completed_buffers_head = nd->next();
341 nd->set_next(buffers_to_delete);
342 buffers_to_delete = nd;
343 }
344 _completed_buffers_tail = NULL;
345 _n_completed_buffers = 0;
346 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
347 }
348 while (buffers_to_delete != NULL) {
349 BufferNode* nd = buffers_to_delete;
350 buffers_to_delete = nd->next();
351 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
352 }
353 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
354 // So we can safely manipulate these queues.
355 for (JavaThread* t = Threads::first(); t; t = t->next()) {
356 t->satb_mark_queue().reset();
357 }
358 shared_satb_queue()->reset();
359 }