1 /*
2 * Copyright (c) 2001, 2014, 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 // The buffer might contain refs into the CSet. We have to filter it
39 // first before we flush it, otherwise we might end up with an
40 // enqueued buffer with refs into the CSet which breaks our invariants.
41 filter();
42 PtrQueue::flush();
43 }
44
45 // This method removes entries from an SATB buffer that will not be
46 // useful to the concurrent marking threads. An entry is removed if it
47 // satisfies one of the following conditions:
48 //
49 // * it points to an object outside the G1 heap (G1's concurrent
50 // marking only visits objects inside the G1 heap),
51 // * it points to an object that has been allocated since marking
52 // started (according to SATB those objects do not need to be
53 // visited during marking), or
54 // * it points to an object that has already been marked (no need to
55 // process it again).
56 //
57 // The rest of the entries will be retained and are compacted towards
58 // the top of the buffer. Note that, because we do not allow old
59 // regions in the CSet during marking, all objects on the CSet regions
60 // are young (eden or survivors) and therefore implicitly live. So any
61 // references into the CSet will be removed during filtering.
62
63 void ObjPtrQueue::filter() {
64 G1CollectedHeap* g1h = G1CollectedHeap::heap();
65 void** buf = _buf;
66 size_t sz = _sz;
67
68 if (buf == NULL) {
69 // nothing to do
70 return;
71 }
72
73 // Used for sanity checking at the end of the loop.
74 debug_only(size_t entries = 0; size_t retained = 0;)
75
76 size_t i = sz;
77 size_t new_index = sz;
78
79 while (i > _index) {
80 assert(i > 0, "we should have at least one more entry to process");
81 i -= oopSize;
82 debug_only(entries += 1;)
83 oop* p = (oop*) &buf[byte_index_to_index((int) i)];
84 oop obj = *p;
85 // NULL the entry so that unused parts of the buffer contain NULLs
86 // at the end. If we are going to retain it we will copy it to its
87 // final place. If we have retained all entries we have visited so
88 // far, we'll just end up copying it to the same place.
89 *p = NULL;
90
91 bool retain = g1h->is_obj_ill(obj);
92 if (retain) {
93 assert(new_index > 0, "we should not have already filled up the buffer");
94 new_index -= oopSize;
95 assert(new_index >= i,
96 "new_index should never be below i, as we always compact 'up'");
97 oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
98 assert(new_p >= p, "the destination location should never be below "
99 "the source as we always compact 'up'");
100 assert(*new_p == NULL,
101 "we should have already cleared the destination location");
102 *new_p = obj;
103 debug_only(retained += 1;)
104 }
105 }
106
107 #ifdef ASSERT
108 size_t entries_calc = (sz - _index) / oopSize;
109 assert(entries == entries_calc, "the number of entries we counted "
110 "should match the number of entries we calculated");
111 size_t retained_calc = (sz - new_index) / oopSize;
112 assert(retained == retained_calc, "the number of retained entries we counted "
113 "should match the number of retained entries we calculated");
114 #endif // ASSERT
115
116 _index = new_index;
117 }
118
119 // This method will first apply the above filtering to the buffer. If
120 // post-filtering a large enough chunk of the buffer has been cleared
121 // we can re-use the buffer (instead of enqueueing it) and we can just
122 // allow the mutator to carry on executing using the same buffer
123 // instead of replacing it.
124
125 bool ObjPtrQueue::should_enqueue_buffer() {
126 assert(_lock == NULL || _lock->owned_by_self(),
127 "we should have taken the lock before calling this");
128
129 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to
130 // filter the buffer given that this will remove any references into
131 // the CSet as we currently assume that no such refs will appear in
132 // enqueued buffers.
133
134 // This method should only be called if there is a non-NULL buffer
135 // that is full.
136 assert(_index == 0, "pre-condition");
137 assert(_buf != NULL, "pre-condition");
138
139 filter();
140
141 size_t sz = _sz;
142 size_t all_entries = sz / oopSize;
143 size_t retained_entries = (sz - _index) / oopSize;
144 size_t perc = retained_entries * 100 / all_entries;
145 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
146 return should_enqueue;
147 }
148
149 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
150 if (_buf != NULL) {
151 apply_closure_to_buffer(cl, _buf, _index, _sz);
152 }
153 }
154
155 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {
156 if (_buf != NULL) {
157 apply_closure_to_buffer(cl, _buf, _index, _sz);
158 _index = _sz;
159 }
160 }
161
162 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
163 void** buf, size_t index, size_t sz) {
164 if (cl == NULL) return;
165 for (size_t i = index; i < sz; i += oopSize) {
166 oop obj = (oop)buf[byte_index_to_index((int)i)];
167 // There can be NULL entries because of destructors.
168 if (obj != NULL) {
169 cl->do_object(obj);
170 }
171 }
172 }
173
174 #ifndef PRODUCT
175 // Helpful for debugging
176
177 void ObjPtrQueue::print(const char* name) {
178 print(name, _buf, _index, _sz);
179 }
180
181 void ObjPtrQueue::print(const char* name,
182 void** buf, size_t index, size_t sz) {
183 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" "
184 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
185 name, buf, index, sz);
186 }
187 #endif // PRODUCT
188
189 #ifdef ASSERT
190 void ObjPtrQueue::verify_oops_in_buffer() {
191 if (_buf == NULL) return;
192 for (size_t i = _index; i < _sz; i += oopSize) {
193 oop obj = (oop)_buf[byte_index_to_index((int)i)];
194 assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
195 "Not an oop");
196 }
197 }
198 #endif
199
200 SATBMarkQueueSet::SATBMarkQueueSet() :
201 PtrQueueSet(), _closures(NULL) {
202 _shared_satb_queue = ObjPtrQueue(this, true /*perm*/);
203 }
204
205 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
206 int process_completed_threshold,
207 Mutex* lock) {
208 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
209 _shared_satb_queue.set_lock(lock);
210 _closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC);
211 }
212
213 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
214 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
215 t->satb_mark_queue().handle_zero_index();
216 }
217
218 #ifdef ASSERT
219 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
220 gclog_or_tty->print_cr("Expected SATB active state: %s",
221 expected_active ? "ACTIVE" : "INACTIVE");
222 gclog_or_tty->print_cr("Actual SATB active states:");
223 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
224 for (JavaThread* t = Threads::first(); t; t = t->next()) {
225 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
226 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
227 }
228 gclog_or_tty->print_cr(" Shared queue: %s",
229 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
230 }
231
232 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
233 // Verify queue set state
234 if (is_active() != expected_active) {
235 dump_active_states(expected_active);
236 guarantee(false, "SATB queue set has an unexpected active state");
237 }
238
239 // Verify thread queue states
240 for (JavaThread* t = Threads::first(); t; t = t->next()) {
241 if (t->satb_mark_queue().is_active() != expected_active) {
242 dump_active_states(expected_active);
243 guarantee(false, "Thread SATB queue has an unexpected active state");
244 }
245 }
246
247 // Verify shared queue state
248 if (shared_satb_queue()->is_active() != expected_active) {
249 dump_active_states(expected_active);
250 guarantee(false, "Shared SATB queue has an unexpected active state");
251 }
252 }
253 #endif // ASSERT
254
255 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
256 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
257 #ifdef ASSERT
258 verify_active_states(expected_active);
259 #endif // ASSERT
260 _all_active = active;
261 for (JavaThread* t = Threads::first(); t; t = t->next()) {
262 t->satb_mark_queue().set_active(active);
263 }
264 shared_satb_queue()->set_active(active);
265 }
266
267 void SATBMarkQueueSet::filter_thread_buffers() {
268 for(JavaThread* t = Threads::first(); t; t = t->next()) {
269 t->satb_mark_queue().filter();
270 }
271 shared_satb_queue()->filter();
272 }
273
274 void SATBMarkQueueSet::set_closure(uint worker, ObjectClosure* closure) {
275 assert(_closures != NULL, "Precondition");
276 assert(worker < ParallelGCThreads, "Worker index must be in range [0...ParallelGCThreads)");
277 _closures[worker] = closure;
278 }
279
280 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(uint worker) {
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 ObjectClosure* cl = _closures[worker];
293 if (nd != NULL) {
294 void **buf = BufferNode::make_buffer_from_node(nd);
295 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
296 deallocate_buffer(buf);
297 return true;
298 } else {
299 return false;
300 }
301 }
302
303 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {
304 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
305 assert(cl != NULL, "pre-condition");
306
307 BufferNode* nd = _completed_buffers_head;
308 while (nd != NULL) {
309 void** buf = BufferNode::make_buffer_from_node(nd);
310 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
311 nd = nd->next();
312 }
313 }
314
315 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {
316 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
317 assert(cl != NULL, "pre-condition");
318
319 for (JavaThread* t = Threads::first(); t; t = t->next()) {
320 t->satb_mark_queue().apply_closure(cl);
321 }
322 shared_satb_queue()->apply_closure(cl);
323 }
324
325 #ifndef PRODUCT
326 // Helpful for debugging
327
328 #define SATB_PRINTER_BUFFER_SIZE 256
329
330 void SATBMarkQueueSet::print_all(const char* msg) {
331 char buffer[SATB_PRINTER_BUFFER_SIZE];
332 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
333
334 gclog_or_tty->cr();
335 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
336
337 BufferNode* nd = _completed_buffers_head;
338 int i = 0;
339 while (nd != NULL) {
340 void** buf = BufferNode::make_buffer_from_node(nd);
341 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
342 ObjPtrQueue::print(buffer, buf, 0, _sz);
343 nd = nd->next();
344 i += 1;
345 }
346
347 for (JavaThread* t = Threads::first(); t; t = t->next()) {
348 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
349 t->satb_mark_queue().print(buffer);
350 }
351
352 shared_satb_queue()->print("Shared");
353
354 gclog_or_tty->cr();
355 }
356 #endif // PRODUCT
357
358 void SATBMarkQueueSet::abandon_partial_marking() {
359 BufferNode* buffers_to_delete = NULL;
360 {
361 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
362 while (_completed_buffers_head != NULL) {
363 BufferNode* nd = _completed_buffers_head;
364 _completed_buffers_head = nd->next();
365 nd->set_next(buffers_to_delete);
366 buffers_to_delete = nd;
367 }
368 _completed_buffers_tail = NULL;
369 _n_completed_buffers = 0;
370 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
371 }
372 while (buffers_to_delete != NULL) {
373 BufferNode* nd = buffers_to_delete;
374 buffers_to_delete = nd->next();
375 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
376 }
377 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
378 // So we can safely manipulate these queues.
379 for (JavaThread* t = Threads::first(); t; t = t->next()) {
380 t->satb_mark_queue().reset();
381 }
382 shared_satb_queue()->reset();
383 }