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 "memory/allocation.inline.hpp"
29 #include "memory/sharedHeap.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/mutexLocker.hpp"
32 #include "runtime/thread.hpp"
33 #include "runtime/vmThread.hpp"
34
35 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
36
37 void ObjPtrQueue::flush() {
38 // Filter now to possibly save work later. If filtering empties the
39 // buffer then flush_impl can deallocate the buffer.
40 filter();
41 flush_impl();
42 }
43
44 // Return true if a SATB buffer entry refers to an object that
45 // requires marking.
46 //
47 // The entry must point into the G1 heap. In particular, it must not
48 // be a NULL pointer. NULL pointers are pre-filtered and never
49 // inserted into a SATB buffer.
50 //
51 // An entry that is below the NTAMS pointer for the containing heap
52 // region requires marking. Such an entry must point to a valid object.
53 //
54 // An entry that is at least the NTAMS pointer for the containing heap
55 // region might be any of the following, none of which should be marked.
56 //
57 // * A reference to an object allocated since marking started.
58 // According to SATB, such objects are implicitly kept live and do
59 // not need to be dealt with via SATB buffer processing.
60 //
61 // * A reference to a young generation object. Young objects are
62 // handled separately and are not marked by concurrent marking.
63 //
64 // * A stale reference to a young generation object. If a young
65 // generation object reference is recorded and not filtered out
66 // before being moved by a young collection, the reference becomes
67 // stale.
68 //
69 // * A stale reference to an eagerly reclaimed humongous object. If a
70 // humongous object is recorded and then reclaimed, the reference
71 // becomes stale.
72 //
73 // The stale reference cases are implicitly handled by the NTAMS
74 // comparison. Because of the possibility of stale references, buffer
75 // processing must be somewhat circumspect and not assume entries
76 // in an unfiltered buffer refer to valid objects.
77
78 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {
79 // Includes rejection of NULL pointers.
80 assert(heap->is_in_reserved(entry),
81 err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)));
82
83 HeapRegion* region = heap->heap_region_containing_raw(entry);
84 assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry)));
85 if (entry >= region->next_top_at_mark_start()) {
86 return false;
87 }
88
89 assert(((oop)entry)->is_oop(true /* ignore mark word */),
90 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)));
91
92 return true;
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 void ObjPtrQueue::filter() {
101 G1CollectedHeap* g1h = G1CollectedHeap::heap();
102 void** buf = _buf;
103 size_t sz = _sz;
104
105 if (buf == NULL) {
106 // nothing to do
107 return;
108 }
109
110 // Used for sanity checking at the end of the loop.
111 debug_only(size_t entries = 0; size_t retained = 0;)
112
113 size_t i = sz;
114 size_t new_index = sz;
115
116 while (i > _index) {
117 assert(i > 0, "we should have at least one more entry to process");
118 i -= oopSize;
119 debug_only(entries += 1;)
120 void** p = &buf[byte_index_to_index((int) i)];
121 void* entry = *p;
122 // NULL the entry so that unused parts of the buffer contain NULLs
123 // at the end. If we are going to retain it we will copy it to its
124 // final place. If we have retained all entries we have visited so
125 // far, we'll just end up copying it to the same place.
126 *p = NULL;
127
128 if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) {
129 assert(new_index > 0, "we should not have already filled up the buffer");
130 new_index -= oopSize;
131 assert(new_index >= i,
132 "new_index should never be below i, as we alwaysr compact 'up'");
133 void** new_p = &buf[byte_index_to_index((int) new_index)];
134 assert(new_p >= p, "the destination location should never be below "
135 "the source as we always compact 'up'");
136 assert(*new_p == NULL,
137 "we should have already cleared the destination location");
138 *new_p = entry;
139 debug_only(retained += 1;)
140 }
141 }
142
143 #ifdef ASSERT
144 size_t entries_calc = (sz - _index) / oopSize;
145 assert(entries == entries_calc, "the number of entries we counted "
146 "should match the number of entries we calculated");
147 size_t retained_calc = (sz - new_index) / oopSize;
148 assert(retained == retained_calc, "the number of retained entries we counted "
149 "should match the number of retained entries we calculated");
150 #endif // ASSERT
151
152 _index = new_index;
153 }
154
155 // This method will first apply the above filtering to the buffer. If
156 // post-filtering a large enough chunk of the buffer has been cleared
157 // we can re-use the buffer (instead of enqueueing it) and we can just
158 // allow the mutator to carry on executing using the same buffer
159 // instead of replacing it.
160
161 bool ObjPtrQueue::should_enqueue_buffer() {
162 assert(_lock == NULL || _lock->owned_by_self(),
163 "we should have taken the lock before calling this");
164
165 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to
166 // filter the buffer given that this will remove any references into
167 // the CSet as we currently assume that no such refs will appear in
168 // enqueued buffers.
169
170 // This method should only be called if there is a non-NULL buffer
171 // that is full.
172 assert(_index == 0, "pre-condition");
173 assert(_buf != NULL, "pre-condition");
174
175 filter();
176
177 size_t sz = _sz;
178 size_t all_entries = sz / oopSize;
179 size_t retained_entries = (sz - _index) / oopSize;
180 size_t perc = retained_entries * 100 / all_entries;
181 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
182 return should_enqueue;
183 }
184
185 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {
186 if (_buf != NULL) {
187 apply_closure_to_buffer(cl, _buf, _index, _sz);
188 _index = _sz;
189 }
190 }
191
192 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
193 void** buf, size_t index, size_t sz) {
194 if (cl == NULL) return;
195 for (size_t i = index; i < sz; i += oopSize) {
196 oop obj = (oop)buf[byte_index_to_index((int)i)];
197 // There can be NULL entries because of destructors.
198 if (obj != NULL) {
199 cl->do_object(obj);
200 }
201 }
202 }
203
204 #ifndef PRODUCT
205 // Helpful for debugging
206
207 void ObjPtrQueue::print(const char* name) {
208 print(name, _buf, _index, _sz);
209 }
210
211 void ObjPtrQueue::print(const char* name,
212 void** buf, size_t index, size_t sz) {
213 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" "
214 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
215 name, buf, index, sz);
216 }
217 #endif // PRODUCT
218
219 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
220 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
221 #endif // _MSC_VER
222
223 SATBMarkQueueSet::SATBMarkQueueSet() :
224 PtrQueueSet(),
225 _shared_satb_queue(this, true /*perm*/) { }
226
227 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
228 int process_completed_threshold,
229 Mutex* lock) {
230 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
231 _shared_satb_queue.set_lock(lock);
232 }
233
234 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
235 t->satb_mark_queue().handle_zero_index();
236 }
237
238 #ifdef ASSERT
239 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
240 gclog_or_tty->print_cr("Expected SATB active state: %s",
241 expected_active ? "ACTIVE" : "INACTIVE");
242 gclog_or_tty->print_cr("Actual SATB active states:");
243 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
244 for (JavaThread* t = Threads::first(); t; t = t->next()) {
245 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
246 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
247 }
248 gclog_or_tty->print_cr(" Shared queue: %s",
249 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
250 }
251
252 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
253 // Verify queue set state
254 if (is_active() != expected_active) {
255 dump_active_states(expected_active);
256 guarantee(false, "SATB queue set has an unexpected active state");
257 }
258
259 // Verify thread queue states
260 for (JavaThread* t = Threads::first(); t; t = t->next()) {
261 if (t->satb_mark_queue().is_active() != expected_active) {
262 dump_active_states(expected_active);
263 guarantee(false, "Thread SATB queue has an unexpected active state");
264 }
265 }
266
267 // Verify shared queue state
268 if (shared_satb_queue()->is_active() != expected_active) {
269 dump_active_states(expected_active);
270 guarantee(false, "Shared SATB queue has an unexpected active state");
271 }
272 }
273 #endif // ASSERT
274
275 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
276 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
277 #ifdef ASSERT
278 verify_active_states(expected_active);
279 #endif // ASSERT
280 _all_active = active;
281 for (JavaThread* t = Threads::first(); t; t = t->next()) {
282 t->satb_mark_queue().set_active(active);
283 }
284 shared_satb_queue()->set_active(active);
285 }
286
287 void SATBMarkQueueSet::filter_thread_buffers() {
288 for(JavaThread* t = Threads::first(); t; t = t->next()) {
289 t->satb_mark_queue().filter();
290 }
291 shared_satb_queue()->filter();
292 }
293
294 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(ObjectClosure* cl) {
295 BufferNode* nd = NULL;
296 {
297 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
298 if (_completed_buffers_head != NULL) {
299 nd = _completed_buffers_head;
300 _completed_buffers_head = nd->next();
301 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
302 _n_completed_buffers--;
303 if (_n_completed_buffers == 0) _process_completed = false;
304 }
305 }
306 if (nd != NULL) {
307 void **buf = BufferNode::make_buffer_from_node(nd);
308 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
309 deallocate_buffer(buf);
310 return true;
311 } else {
312 return false;
313 }
314 }
315
316 #ifndef PRODUCT
317 // Helpful for debugging
318
319 #define SATB_PRINTER_BUFFER_SIZE 256
320
321 void SATBMarkQueueSet::print_all(const char* msg) {
322 char buffer[SATB_PRINTER_BUFFER_SIZE];
323 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
324
325 gclog_or_tty->cr();
326 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
327
328 BufferNode* nd = _completed_buffers_head;
329 int i = 0;
330 while (nd != NULL) {
331 void** buf = BufferNode::make_buffer_from_node(nd);
332 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
333 ObjPtrQueue::print(buffer, buf, 0, _sz);
334 nd = nd->next();
335 i += 1;
336 }
337
338 for (JavaThread* t = Threads::first(); t; t = t->next()) {
339 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
340 t->satb_mark_queue().print(buffer);
341 }
342
343 shared_satb_queue()->print("Shared");
344
345 gclog_or_tty->cr();
346 }
347 #endif // PRODUCT
348
349 void SATBMarkQueueSet::abandon_partial_marking() {
350 BufferNode* buffers_to_delete = NULL;
351 {
352 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
353 while (_completed_buffers_head != NULL) {
354 BufferNode* nd = _completed_buffers_head;
355 _completed_buffers_head = nd->next();
356 nd->set_next(buffers_to_delete);
357 buffers_to_delete = nd;
358 }
359 _completed_buffers_tail = NULL;
360 _n_completed_buffers = 0;
361 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
362 }
363 while (buffers_to_delete != NULL) {
364 BufferNode* nd = buffers_to_delete;
365 buffers_to_delete = nd->next();
366 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
367 }
368 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
369 // So we can safely manipulate these queues.
370 for (JavaThread* t = Threads::first(); t; t = t->next()) {
371 t->satb_mark_queue().reset();
372 }
373 shared_satb_queue()->reset();
374 }