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_interface/collectedHeap.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/mutexLocker.hpp"
32 #include "runtime/thread.hpp"
33 #include "runtime/vmThread.hpp"
34
35 void ObjPtrQueue::flush() {
36 // Filter now to possibly save work later. If filtering empties the
37 // buffer then flush_impl can deallocate the buffer.
38 filter();
39 flush_impl();
40 }
41
42 // Return true if a SATB buffer entry refers to an object that
43 // requires marking.
44 //
45 // The entry must point into the G1 heap. In particular, it must not
46 // be a NULL pointer. NULL pointers are pre-filtered and never
47 // inserted into a SATB buffer.
48 //
49 // An entry that is below the NTAMS pointer for the containing heap
50 // region requires marking. Such an entry must point to a valid object.
51 //
52 // An entry that is at least the NTAMS pointer for the containing heap
53 // region might be any of the following, none of which should be marked.
54 //
55 // * A reference to an object allocated since marking started.
56 // According to SATB, such objects are implicitly kept live and do
57 // not need to be dealt with via SATB buffer processing.
58 //
59 // * A reference to a young generation object. Young objects are
60 // handled separately and are not marked by concurrent marking.
61 //
62 // * A stale reference to a young generation object. If a young
63 // generation object reference is recorded and not filtered out
64 // before being moved by a young collection, the reference becomes
65 // stale.
66 //
67 // * A stale reference to an eagerly reclaimed humongous object. If a
68 // humongous object is recorded and then reclaimed, the reference
69 // becomes stale.
70 //
71 // The stale reference cases are implicitly handled by the NTAMS
72 // comparison. Because of the possibility of stale references, buffer
73 // processing must be somewhat circumspect and not assume entries
74 // in an unfiltered buffer refer to valid objects.
75
76 inline bool requires_marking(const HeapWord* entry, G1CollectedHeap* heap) {
77 // Includes rejection of NULL pointers.
78 assert(heap->is_in_reserved(entry),
79 err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)));
80
81 HeapRegion* region = heap->heap_region_containing_raw(entry);
82 assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry)));
83 if (entry >= region->next_top_at_mark_start()) return false;
84
85 // Can obj really have it's mark word set? It's not in young gen...
86 assert(((oop)entry)->is_oop(true /* ignore mark word */),
87 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)));
88
89 return true;
90 }
91
92 // This method removes entries from a SATB buffer that will not be
93 // useful to the concurrent marking threads. Entries are retained if
94 // they require marking and are not already marked. Retained entries
95 // are compacted toward the top of the buffer.
96
97 void ObjPtrQueue::filter() {
98 G1CollectedHeap* g1h = G1CollectedHeap::heap();
99 void** buf = _buf;
100 size_t sz = _sz;
101
102 if (buf == NULL) {
103 // nothing to do
104 return;
105 }
106
107 // Used for sanity checking at the end of the loop.
108 debug_only(size_t entries = 0; size_t retained = 0;)
109
110 size_t i = sz;
111 size_t new_index = sz;
112
113 while (i > _index) {
114 assert(i > 0, "we should have at least one more entry to process");
115 i -= oopSize;
116 debug_only(entries += 1;)
117 HeapWord** p = (HeapWord**) &buf[byte_index_to_index((int) i)];
118 HeapWord* entry = *p;
119 // NULL the entry so that unused parts of the buffer contain NULLs
120 // at the end. If we are going to retain it we will copy it to its
121 // final place. If we have retained all entries we have visited so
122 // far, we'll just end up copying it to the same place.
123 *p = NULL;
124
125 if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) {
126 assert(new_index > 0, "we should not have already filled up the buffer");
127 new_index -= oopSize;
128 assert(new_index >= i,
129 "new_index should never be below i, as we always compact 'up'");
130 HeapWord** new_p = (HeapWord**) &buf[byte_index_to_index((int) new_index)];
131 assert(new_p >= p, "the destination location should never be below "
132 "the source as we always compact 'up'");
133 assert(*new_p == NULL,
134 "we should have already cleared the destination location");
135 *new_p = entry;
136 debug_only(retained += 1;)
137 }
138 }
139
140 #ifdef ASSERT
141 size_t entries_calc = (sz - _index) / oopSize;
142 assert(entries == entries_calc, "the number of entries we counted "
143 "should match the number of entries we calculated");
144 size_t retained_calc = (sz - new_index) / oopSize;
145 assert(retained == retained_calc, "the number of retained entries we counted "
146 "should match the number of retained entries we calculated");
147 #endif // ASSERT
148
149 _index = new_index;
150 }
151
152 // This method will first apply the above filtering to the buffer. If
153 // post-filtering a large enough chunk of the buffer has been cleared
154 // we can re-use the buffer (instead of enqueueing it) and we can just
155 // allow the mutator to carry on executing using the same buffer
156 // instead of replacing it.
157
158 bool ObjPtrQueue::should_enqueue_buffer() {
159 assert(_lock == NULL || _lock->owned_by_self(),
160 "we should have taken the lock before calling this");
161
162 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to
163 // filter the buffer given that this will remove any references into
164 // the CSet as we currently assume that no such refs will appear in
165 // enqueued buffers.
166
167 // This method should only be called if there is a non-NULL buffer
168 // that is full.
169 assert(_index == 0, "pre-condition");
170 assert(_buf != NULL, "pre-condition");
171
172 filter();
173
174 size_t sz = _sz;
175 size_t all_entries = sz / oopSize;
176 size_t retained_entries = (sz - _index) / oopSize;
177 size_t perc = retained_entries * 100 / all_entries;
178 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
179 return should_enqueue;
180 }
181
182 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
183 if (_buf != NULL) {
184 apply_closure_to_buffer(cl, _buf, _index, _sz);
185 }
186 }
187
188 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {
189 if (_buf != NULL) {
190 apply_closure_to_buffer(cl, _buf, _index, _sz);
191 _index = _sz;
192 }
193 }
194
195 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
196 void** buf, size_t index, size_t sz) {
197 if (cl == NULL) return;
198 for (size_t i = index; i < sz; i += oopSize) {
199 oop obj = (oop)buf[byte_index_to_index((int)i)];
200 // There can be NULL entries because of destructors.
201 if (obj != NULL) {
202 cl->do_object(obj);
203 }
204 }
205 }
206
207 #ifndef PRODUCT
208 // Helpful for debugging
209
210 void ObjPtrQueue::print(const char* name) {
211 print(name, _buf, _index, _sz);
212 }
213
214 void ObjPtrQueue::print(const char* name,
215 void** buf, size_t index, size_t sz) {
216 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" "
217 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
218 name, p2i(buf), index, sz);
219 }
220 #endif // PRODUCT
221
222 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
223 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
224 #endif // _MSC_VER
225
226 SATBMarkQueueSet::SATBMarkQueueSet() :
227 PtrQueueSet(), _closures(NULL),
228 _shared_satb_queue(this, true /*perm*/) { }
229
230 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
231 int process_completed_threshold,
232 Mutex* lock) {
233 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
234 _shared_satb_queue.set_lock(lock);
235 _closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC);
236 }
237
238 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
239 t->satb_mark_queue().handle_zero_index();
240 }
241
242 #ifdef ASSERT
243 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
244 gclog_or_tty->print_cr("Expected SATB active state: %s",
245 expected_active ? "ACTIVE" : "INACTIVE");
246 gclog_or_tty->print_cr("Actual SATB active states:");
247 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
248 for (JavaThread* t = Threads::first(); t; t = t->next()) {
249 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
250 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
251 }
252 gclog_or_tty->print_cr(" Shared queue: %s",
253 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
254 }
255
256 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
257 // Verify queue set state
258 if (is_active() != expected_active) {
259 dump_active_states(expected_active);
260 guarantee(false, "SATB queue set has an unexpected active state");
261 }
262
263 // Verify thread queue states
264 for (JavaThread* t = Threads::first(); t; t = t->next()) {
265 if (t->satb_mark_queue().is_active() != expected_active) {
266 dump_active_states(expected_active);
267 guarantee(false, "Thread SATB queue has an unexpected active state");
268 }
269 }
270
271 // Verify shared queue state
272 if (shared_satb_queue()->is_active() != expected_active) {
273 dump_active_states(expected_active);
274 guarantee(false, "Shared SATB queue has an unexpected active state");
275 }
276 }
277 #endif // ASSERT
278
279 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
280 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
281 #ifdef ASSERT
282 verify_active_states(expected_active);
283 #endif // ASSERT
284 _all_active = active;
285 for (JavaThread* t = Threads::first(); t; t = t->next()) {
286 t->satb_mark_queue().set_active(active);
287 }
288 shared_satb_queue()->set_active(active);
289 }
290
291 void SATBMarkQueueSet::filter_thread_buffers() {
292 for(JavaThread* t = Threads::first(); t; t = t->next()) {
293 t->satb_mark_queue().filter();
294 }
295 shared_satb_queue()->filter();
296 }
297
298 void SATBMarkQueueSet::set_closure(uint worker, ObjectClosure* closure) {
299 assert(_closures != NULL, "Precondition");
300 assert(worker < ParallelGCThreads, "Worker index must be in range [0...ParallelGCThreads)");
301 _closures[worker] = closure;
302 }
303
304 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(uint worker) {
305 BufferNode* nd = NULL;
306 {
307 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
308 if (_completed_buffers_head != NULL) {
309 nd = _completed_buffers_head;
310 _completed_buffers_head = nd->next();
311 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
312 _n_completed_buffers--;
313 if (_n_completed_buffers == 0) _process_completed = false;
314 }
315 }
316 ObjectClosure* cl = _closures[worker];
317 if (nd != NULL) {
318 void **buf = BufferNode::make_buffer_from_node(nd);
319 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
320 deallocate_buffer(buf);
321 return true;
322 } else {
323 return false;
324 }
325 }
326
327 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {
328 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
329 assert(cl != NULL, "pre-condition");
330
331 BufferNode* nd = _completed_buffers_head;
332 while (nd != NULL) {
333 void** buf = BufferNode::make_buffer_from_node(nd);
334 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
335 nd = nd->next();
336 }
337 }
338
339 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {
340 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
341 assert(cl != NULL, "pre-condition");
342
343 for (JavaThread* t = Threads::first(); t; t = t->next()) {
344 t->satb_mark_queue().apply_closure(cl);
345 }
346 shared_satb_queue()->apply_closure(cl);
347 }
348
349 #ifndef PRODUCT
350 // Helpful for debugging
351
352 #define SATB_PRINTER_BUFFER_SIZE 256
353
354 void SATBMarkQueueSet::print_all(const char* msg) {
355 char buffer[SATB_PRINTER_BUFFER_SIZE];
356 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
357
358 gclog_or_tty->cr();
359 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
360
361 BufferNode* nd = _completed_buffers_head;
362 int i = 0;
363 while (nd != NULL) {
364 void** buf = BufferNode::make_buffer_from_node(nd);
365 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
366 ObjPtrQueue::print(buffer, buf, 0, _sz);
367 nd = nd->next();
368 i += 1;
369 }
370
371 for (JavaThread* t = Threads::first(); t; t = t->next()) {
372 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
373 t->satb_mark_queue().print(buffer);
374 }
375
376 shared_satb_queue()->print("Shared");
377
378 gclog_or_tty->cr();
379 }
380 #endif // PRODUCT
381
382 void SATBMarkQueueSet::abandon_partial_marking() {
383 BufferNode* buffers_to_delete = NULL;
384 {
385 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
386 while (_completed_buffers_head != NULL) {
387 BufferNode* nd = _completed_buffers_head;
388 _completed_buffers_head = nd->next();
389 nd->set_next(buffers_to_delete);
390 buffers_to_delete = nd;
391 }
392 _completed_buffers_tail = NULL;
393 _n_completed_buffers = 0;
394 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
395 }
396 while (buffers_to_delete != NULL) {
397 BufferNode* nd = buffers_to_delete;
398 buffers_to_delete = nd->next();
399 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
400 }
401 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
402 // So we can safely manipulate these queues.
403 for (JavaThread* t = Threads::first(); t; t = t->next()) {
404 t->satb_mark_queue().reset();
405 }
406 shared_satb_queue()->reset();
407 }