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