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 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {
78 // Includes rejection of NULL pointers.
79 assert(heap->is_in_reserved(entry),
80 "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry));
81
82 HeapRegion* region = heap->heap_region_containing_raw(entry);
83 assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry));
84 if (entry >= region->next_top_at_mark_start()) {
85 return false;
86 }
87
88 assert(((oop)entry)->is_oop(true /* ignore mark word */),
89 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry));
90
91 return true;
92 }
93
94 // This method removes entries from a SATB buffer that will not be
95 // useful to the concurrent marking threads. Entries are retained if
96 // they require marking and are not already marked. Retained entries
97 // are compacted toward the top of the buffer.
98
99 void ObjPtrQueue::filter() {
100 G1CollectedHeap* g1h = G1CollectedHeap::heap();
101 void** buf = _buf;
102 size_t sz = _sz;
103
104 if (buf == NULL) {
105 // nothing to do
106 return;
107 }
108
109 // Used for sanity checking at the end of the loop.
110 debug_only(size_t entries = 0; size_t retained = 0;)
111
112 size_t i = sz;
113 size_t new_index = sz;
114
115 while (i > _index) {
116 assert(i > 0, "we should have at least one more entry to process");
117 i -= oopSize;
118 debug_only(entries += 1;)
119 void** p = &buf[byte_index_to_index((int) i)];
120 void* entry = *p;
121 // NULL the entry so that unused parts of the buffer contain NULLs
122 // at the end. If we are going to retain it we will copy it to its
123 // final place. If we have retained all entries we have visited so
124 // far, we'll just end up copying it to the same place.
125 *p = NULL;
126
127 if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) {
128 assert(new_index > 0, "we should not have already filled up the buffer");
129 new_index -= oopSize;
130 assert(new_index >= i,
131 "new_index should never be below i, as we always compact 'up'");
132 void** new_p = &buf[byte_index_to_index((int) new_index)];
133 assert(new_p >= p, "the destination location should never be below "
134 "the source as we always compact 'up'");
135 assert(*new_p == NULL,
136 "we should have already cleared the destination location");
137 *new_p = entry;
138 debug_only(retained += 1;)
139 }
140 }
141
142 #ifdef ASSERT
143 size_t entries_calc = (sz - _index) / oopSize;
144 assert(entries == entries_calc, "the number of entries we counted "
145 "should match the number of entries we calculated");
146 size_t retained_calc = (sz - new_index) / oopSize;
147 assert(retained == retained_calc, "the number of retained entries we counted "
148 "should match the number of retained entries we calculated");
149 #endif // ASSERT
150
151 _index = new_index;
152 }
153
154 // This method will first apply the above filtering to the buffer. If
155 // post-filtering a large enough chunk of the buffer has been cleared
156 // we can re-use the buffer (instead of enqueueing it) and we can just
157 // allow the mutator to carry on executing using the same buffer
158 // instead of replacing it.
159
160 bool ObjPtrQueue::should_enqueue_buffer() {
161 assert(_lock == NULL || _lock->owned_by_self(),
162 "we should have taken the lock before calling this");
163
164 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
165
166 // This method should only be called if there is a non-NULL buffer
167 // that is full.
168 assert(_index == 0, "pre-condition");
169 assert(_buf != NULL, "pre-condition");
170
171 filter();
172
173 size_t sz = _sz;
174 size_t all_entries = sz / oopSize;
175 size_t retained_entries = (sz - _index) / oopSize;
176 size_t perc = retained_entries * 100 / all_entries;
177 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
178 return should_enqueue;
179 }
180
181 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
182 assert(SafepointSynchronize::is_at_safepoint(),
183 "SATB queues must only be processed at safepoints");
184 if (_buf != NULL) {
185 assert(_index % sizeof(void*) == 0, "invariant");
186 assert(_sz % sizeof(void*) == 0, "invariant");
187 assert(_index <= _sz, "invariant");
188 cl->do_buffer(_buf + byte_index_to_index((int)_index),
189 byte_index_to_index((int)(_sz - _index)));
190 _index = _sz;
191 }
192 }
193
194 #ifndef PRODUCT
195 // Helpful for debugging
196
197 void ObjPtrQueue::print(const char* name) {
198 print(name, _buf, _index, _sz);
199 }
200
201 void ObjPtrQueue::print(const char* name,
202 void** buf, size_t index, size_t sz) {
203 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " "
204 "index: " SIZE_FORMAT " sz: " SIZE_FORMAT,
205 name, p2i(buf), index, sz);
206 }
207 #endif // PRODUCT
208
209 SATBMarkQueueSet::SATBMarkQueueSet() :
210 PtrQueueSet(),
211 _shared_satb_queue(this, true /*perm*/) { }
212
213 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
214 int process_completed_threshold,
215 Mutex* lock) {
216 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
217 _shared_satb_queue.set_lock(lock);
218 }
219
220 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
221 t->satb_mark_queue().handle_zero_index();
222 }
223
224 #ifdef ASSERT
225 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
226 gclog_or_tty->print_cr("Expected SATB active state: %s",
227 expected_active ? "ACTIVE" : "INACTIVE");
228 gclog_or_tty->print_cr("Actual SATB active states:");
229 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
230 for (JavaThread* t = Threads::first(); t; t = t->next()) {
231 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
232 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
233 }
234 gclog_or_tty->print_cr(" Shared queue: %s",
235 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
236 }
237
238 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
239 // Verify queue set state
240 if (is_active() != expected_active) {
241 dump_active_states(expected_active);
242 guarantee(false, "SATB queue set has an unexpected active state");
243 }
244
245 // Verify thread queue states
246 for (JavaThread* t = Threads::first(); t; t = t->next()) {
247 if (t->satb_mark_queue().is_active() != expected_active) {
248 dump_active_states(expected_active);
249 guarantee(false, "Thread SATB queue has an unexpected active state");
250 }
251 }
252
253 // Verify shared queue state
254 if (shared_satb_queue()->is_active() != expected_active) {
255 dump_active_states(expected_active);
256 guarantee(false, "Shared SATB queue has an unexpected active state");
257 }
258 }
259 #endif // ASSERT
260
261 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
262 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
263 #ifdef ASSERT
264 verify_active_states(expected_active);
265 #endif // ASSERT
266 _all_active = active;
267 for (JavaThread* t = Threads::first(); t; t = t->next()) {
268 t->satb_mark_queue().set_active(active);
269 }
270 shared_satb_queue()->set_active(active);
271 }
272
273 void SATBMarkQueueSet::filter_thread_buffers() {
274 for(JavaThread* t = Threads::first(); t; t = t->next()) {
275 t->satb_mark_queue().filter();
276 }
277 shared_satb_queue()->filter();
278 }
279
280 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
281 BufferNode* nd = NULL;
282 {
283 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
284 if (_completed_buffers_head != NULL) {
285 nd = _completed_buffers_head;
286 _completed_buffers_head = nd->next();
287 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
288 _n_completed_buffers--;
289 if (_n_completed_buffers == 0) _process_completed = false;
290 }
291 }
292 if (nd != NULL) {
293 void **buf = BufferNode::make_buffer_from_node(nd);
294 // Skip over NULL entries at beginning (e.g. push end) of buffer.
295 // Filtering can result in non-full completed buffers; see
296 // should_enqueue_buffer.
297 assert(_sz % sizeof(void*) == 0, "invariant");
298 size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);
299 for (size_t i = 0; i < limit; ++i) {
300 if (buf[i] != NULL) {
301 // Found the end of the block of NULLs; process the remainder.
302 cl->do_buffer(buf + i, limit - i);
303 break;
304 }
305 }
306 deallocate_buffer(buf);
307 return true;
308 } else {
309 return false;
310 }
311 }
312
313 #ifndef PRODUCT
314 // Helpful for debugging
315
316 #define SATB_PRINTER_BUFFER_SIZE 256
317
318 void SATBMarkQueueSet::print_all(const char* msg) {
319 char buffer[SATB_PRINTER_BUFFER_SIZE];
320 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
321
322 gclog_or_tty->cr();
323 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
324
325 BufferNode* nd = _completed_buffers_head;
326 int i = 0;
327 while (nd != NULL) {
328 void** buf = BufferNode::make_buffer_from_node(nd);
329 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
330 ObjPtrQueue::print(buffer, buf, 0, _sz);
331 nd = nd->next();
332 i += 1;
333 }
334
335 for (JavaThread* t = Threads::first(); t; t = t->next()) {
336 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
337 t->satb_mark_queue().print(buffer);
338 }
339
340 shared_satb_queue()->print("Shared");
341
342 gclog_or_tty->cr();
343 }
344 #endif // PRODUCT
345
346 void SATBMarkQueueSet::abandon_partial_marking() {
347 BufferNode* buffers_to_delete = NULL;
348 {
349 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
350 while (_completed_buffers_head != NULL) {
351 BufferNode* nd = _completed_buffers_head;
352 _completed_buffers_head = nd->next();
353 nd->set_next(buffers_to_delete);
354 buffers_to_delete = nd;
355 }
356 _completed_buffers_tail = NULL;
357 _n_completed_buffers = 0;
358 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
359 }
360 while (buffers_to_delete != NULL) {
361 BufferNode* nd = buffers_to_delete;
362 buffers_to_delete = nd->next();
363 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
364 }
365 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
366 // So we can safely manipulate these queues.
367 for (JavaThread* t = Threads::first(); t; t = t->next()) {
368 t->satb_mark_queue().reset();
369 }
370 shared_satb_queue()->reset();
371 }