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_implementation/g1/g1CollectedHeap.inline.hpp"
27 #include "gc_implementation/g1/satbQueue.hpp"
28 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "memory/sharedHeap.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/mutexLocker.hpp"
33 #include "runtime/safepoint.hpp"
34 #include "runtime/thread.hpp"
35 #include "runtime/vmThread.hpp"
36
37 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
38
39 void ObjPtrQueue::flush() {
40 // Filter now to possibly save work later. If filtering empties the
41 // buffer then flush_impl can deallocate the buffer.
42 filter();
43 flush_impl();
44 }
45
46 // Return true if a SATB buffer entry refers to an object that
47 // requires marking.
48 //
49 // The entry must point into the G1 heap. In particular, it must not
50 // be a NULL pointer. NULL pointers are pre-filtered and never
51 // inserted into a SATB buffer.
52 //
53 // An entry that is below the NTAMS pointer for the containing heap
54 // region requires marking. Such an entry must point to a valid object.
55 //
56 // An entry that is at least the NTAMS pointer for the containing heap
57 // region might be any of the following, none of which should be marked.
58 //
59 // * A reference to an object allocated since marking started.
60 // According to SATB, such objects are implicitly kept live and do
61 // not need to be dealt with via SATB buffer processing.
62 //
63 // * A reference to a young generation object. Young objects are
64 // handled separately and are not marked by concurrent marking.
65 //
66 // * A stale reference to a young generation object. If a young
67 // generation object reference is recorded and not filtered out
68 // before being moved by a young collection, the reference becomes
69 // stale.
70 //
71 // * A stale reference to an eagerly reclaimed humongous object. If a
72 // humongous object is recorded and then reclaimed, the reference
73 // becomes stale.
74 //
75 // The stale reference cases are implicitly handled by the NTAMS
76 // comparison. Because of the possibility of stale references, buffer
77 // processing must be somewhat circumspect and not assume entries
78 // in an unfiltered buffer refer to valid objects.
79
80 template <class HeapType>
81 inline bool requires_marking(const void* entry, HeapType* heap) {
82 return heap->requires_marking(entry);
83 }
84
85 void ObjPtrQueue::filter() {
86 if (UseG1GC) {
87 filter_impl<G1CollectedHeap>();
88 } else if (UseShenandoahGC) {
89 filter_impl<ShenandoahHeap>();
90 } else {
91 ShouldNotReachHere();
92 }
93 }
94
95 // This method removes entries from a SATB buffer that will not be
96 // useful to the concurrent marking threads. Entries are retained if
97 // they require marking and are not already marked. Retained entries
98 // are compacted toward the top of the buffer.
99
100 template <class HeapType>
101 void ObjPtrQueue::filter_impl() {
102 HeapType* heap = (HeapType*) Universe::heap();
103 void** buf = _buf;
104 size_t sz = _sz;
105
106 if (buf == NULL) {
107 // nothing to do
108 return;
109 }
110
111 // Used for sanity checking at the end of the loop.
112 debug_only(size_t entries = 0; size_t retained = 0;)
113
114 size_t i = sz;
115 size_t new_index = sz;
116
117 while (i > _index) {
118 assert(i > 0, "we should have at least one more entry to process");
119 i -= oopSize;
120 debug_only(entries += 1;)
121 void** p = &buf[byte_index_to_index((int) i)];
122 void* entry = *p;
123 // NULL the entry so that unused parts of the buffer contain NULLs
124 // at the end. If we are going to retain it we will copy it to its
125 // final place. If we have retained all entries we have visited so
126 // far, we'll just end up copying it to the same place.
127 *p = NULL;
128
129 if (requires_marking(entry, heap)) {
130 assert(new_index > 0, "we should not have already filled up the buffer");
131 new_index -= oopSize;
132 assert(new_index >= i,
133 "new_index should never be below i, as we alwaysr compact 'up'");
134 void** new_p = &buf[byte_index_to_index((int) new_index)];
135 assert(new_p >= p, "the destination location should never be below "
136 "the source as we always compact 'up'");
137 assert(*new_p == NULL,
138 "we should have already cleared the destination location");
139 *new_p = entry;
140 debug_only(retained += 1;)
141 }
142 }
143
144 #ifdef ASSERT
145 size_t entries_calc = (sz - _index) / oopSize;
146 assert(entries == entries_calc, "the number of entries we counted "
147 "should match the number of entries we calculated");
148 size_t retained_calc = (sz - new_index) / oopSize;
149 assert(retained == retained_calc, "the number of retained entries we counted "
150 "should match the number of retained entries we calculated");
151 #endif // ASSERT
152
153 _index = new_index;
154 }
155
156 // This method will first apply the above filtering to the buffer. If
157 // post-filtering a large enough chunk of the buffer has been cleared
158 // we can re-use the buffer (instead of enqueueing it) and we can just
159 // allow the mutator to carry on executing using the same buffer
160 // instead of replacing it.
161
162 bool ObjPtrQueue::should_enqueue_buffer() {
163 assert(_lock == NULL || _lock->owned_by_self(),
164 "we should have taken the lock before calling this");
165
166 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
167
168 // This method should only be called if there is a non-NULL buffer
169 // that is full.
170 assert(_index == 0, "pre-condition");
171 assert(_buf != NULL, "pre-condition");
172
173 filter();
174
175 size_t sz = _sz;
176 size_t all_entries = sz / oopSize;
177 size_t retained_entries = (sz - _index) / oopSize;
178 size_t perc = retained_entries * 100 / all_entries;
179 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
180
181 if (UseShenandoahGC) {
182 Thread* t = Thread::current();
183 if (t->is_force_satb_flush()) {
184 if (!should_enqueue && sz != _index) {
185 // Non-empty buffer is compacted, and we decided not to enqueue it.
186 // Shenandoah still wants to know about leftover work in that buffer eventually.
187 // This avoid dealing with these leftovers during the final-mark, after the buffers
188 // are drained completely.
189 // TODO: This can be extended to handle G1 too
190 should_enqueue = true;
191 }
192 t->set_force_satb_flush(false);
193 }
194 }
195
196 return should_enqueue;
197 }
198
199 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
200 assert(SafepointSynchronize::is_at_safepoint(),
201 "SATB queues must only be processed at safepoints");
202 if (_buf != NULL) {
203 assert(_index % sizeof(void*) == 0, "invariant");
204 assert(_sz % sizeof(void*) == 0, "invariant");
205 assert(_index <= _sz, "invariant");
206 cl->do_buffer(_buf + byte_index_to_index((int)_index),
207 byte_index_to_index((int)(_sz - _index)));
208 _index = _sz;
209 }
210 }
211
212 #ifndef PRODUCT
213 // Helpful for debugging
214
215 void ObjPtrQueue::print(const char* name) {
216 print(name, _buf, _index, _sz);
217 }
218
219 void ObjPtrQueue::print(const char* name,
220 void** buf, size_t index, size_t sz) {
221 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" "
222 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
223 name, buf, index, sz);
224 }
225 #endif // PRODUCT
226
227 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
228 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
229 #endif // _MSC_VER
230
231 SATBMarkQueueSet::SATBMarkQueueSet() :
232 PtrQueueSet(),
233 _shared_satb_queue(this, true /*perm*/) { }
234
235 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
236 int process_completed_threshold,
237 Mutex* lock) {
238 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
239 _shared_satb_queue.set_lock(lock);
240 }
241
242 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
243 t->satb_mark_queue().handle_zero_index();
244 }
245
246 #ifdef ASSERT
247 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
248 gclog_or_tty->print_cr("Expected SATB active state: %s",
249 expected_active ? "ACTIVE" : "INACTIVE");
250 gclog_or_tty->print_cr("Actual SATB active states:");
251 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
252 for (JavaThread* t = Threads::first(); t; t = t->next()) {
253 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
254 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
255 }
256 gclog_or_tty->print_cr(" Shared queue: %s",
257 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
258 }
259
260 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
261 // Verify queue set state
262 if (is_active() != expected_active) {
263 dump_active_states(expected_active);
264 guarantee(false, "SATB queue set has an unexpected active state");
265 }
266
267 // Verify thread queue states
268 for (JavaThread* t = Threads::first(); t; t = t->next()) {
269 if (t->satb_mark_queue().is_active() != expected_active) {
270 dump_active_states(expected_active);
271 guarantee(false, "Thread SATB queue has an unexpected active state");
272 }
273 }
274
275 // Verify shared queue state
276 if (shared_satb_queue()->is_active() != expected_active) {
277 dump_active_states(expected_active);
278 guarantee(false, "Shared SATB queue has an unexpected active state");
279 }
280 }
281 #endif // ASSERT
282
283 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
284 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
285 #ifdef ASSERT
286 verify_active_states(expected_active);
287 #endif // ASSERT
288 _all_active = active;
289 for (JavaThread* t = Threads::first(); t; t = t->next()) {
290 t->satb_mark_queue().set_active(active);
291 }
292 shared_satb_queue()->set_active(active);
293 }
294
295 void SATBMarkQueueSet::filter_thread_buffers() {
296 for(JavaThread* t = Threads::first(); t; t = t->next()) {
297 t->satb_mark_queue().filter();
298 }
299 shared_satb_queue()->filter();
300 }
301
302 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
303 BufferNode* nd = NULL;
304 {
305 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
306 if (_completed_buffers_head != NULL) {
307 nd = _completed_buffers_head;
308 _completed_buffers_head = nd->next();
309 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
310 _n_completed_buffers--;
311 if (_n_completed_buffers == 0) _process_completed = false;
312 }
313 }
314 if (nd != NULL) {
315 void **buf = BufferNode::make_buffer_from_node(nd);
316 // Skip over NULL entries at beginning (e.g. push end) of buffer.
317 // Filtering can result in non-full completed buffers; see
318 // should_enqueue_buffer.
319 assert(_sz % sizeof(void*) == 0, "invariant");
320 size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);
321 for (size_t i = 0; i < limit; ++i) {
322 if (buf[i] != NULL) {
323 // Found the end of the block of NULLs; process the remainder.
324 cl->do_buffer(buf + i, limit - i);
325 break;
326 }
327 }
328 deallocate_buffer(buf);
329 return true;
330 } else {
331 return false;
332 }
333 }
334
335 #ifndef PRODUCT
336 // Helpful for debugging
337
338 #define SATB_PRINTER_BUFFER_SIZE 256
339
340 void SATBMarkQueueSet::print_all(const char* msg) {
341 char buffer[SATB_PRINTER_BUFFER_SIZE];
342 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
343
344 gclog_or_tty->cr();
345 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
346
347 BufferNode* nd = _completed_buffers_head;
348 int i = 0;
349 while (nd != NULL) {
350 void** buf = BufferNode::make_buffer_from_node(nd);
351 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
352 ObjPtrQueue::print(buffer, buf, 0, _sz);
353 nd = nd->next();
354 i += 1;
355 }
356
357 for (JavaThread* t = Threads::first(); t; t = t->next()) {
358 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
359 t->satb_mark_queue().print(buffer);
360 }
361
362 shared_satb_queue()->print("Shared");
363
364 gclog_or_tty->cr();
365 }
366 #endif // PRODUCT
367
368 void SATBMarkQueueSet::abandon_partial_marking() {
369 BufferNode* buffers_to_delete = NULL;
370 {
371 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
372 while (_completed_buffers_head != NULL) {
373 BufferNode* nd = _completed_buffers_head;
374 _completed_buffers_head = nd->next();
375 nd->set_next(buffers_to_delete);
376 buffers_to_delete = nd;
377 }
378 _completed_buffers_tail = NULL;
379 _n_completed_buffers = 0;
380 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
381 }
382 while (buffers_to_delete != NULL) {
383 BufferNode* nd = buffers_to_delete;
384 buffers_to_delete = nd->next();
385 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
386 }
387 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
388 // So we can safely manipulate these queues.
389 for (JavaThread* t = Threads::first(); t; t = t->next()) {
390 t->satb_mark_queue().reset();
391 }
392 shared_satb_queue()->reset();
393 }