1 /*
2 * Copyright (c) 2001, 2011, 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 "runtime/mutexLocker.hpp"
31 #include "runtime/thread.hpp"
32 #include "runtime/vmThread.hpp"
33
34 // This method removes entries from an SATB buffer that will not be
35 // useful to the concurrent marking threads. An entry is removed if it
36 // satisfies one of the following conditions:
37 //
38 // * it points to an object outside the G1 heap (G1's concurrent
39 // marking only visits objects inside the G1 heap),
40 // * it points to an object that has been allocated since marking
41 // started (according to SATB those objects do not need to be
42 // visited during marking), or
43 // * it points to an object that has already been marked (no need to
44 // process it again).
45 //
46 // The rest of the entries will be retained and are compacted towards
47 // the top of the buffer. If with this filtering we clear a large
48 // enough chunk of the buffer we can re-use it (instead of enqueueing
49 // it) and we can just allow the mutator to carry on executing.
50
51 bool ObjPtrQueue::should_enqueue_buffer() {
52 assert(_lock == NULL || _lock->owned_by_self(),
53 "we should have taken the lock before calling this");
54
55 // A value of 0 means "don't filter SATB buffers".
56 if (G1SATBBufferEnqueueingThresholdPercent == 0) {
57 return true;
58 }
59
60 G1CollectedHeap* g1h = G1CollectedHeap::heap();
61
62 // This method should only be called if there is a non-NULL buffer
63 // that is full.
64 assert(_index == 0, "pre-condition");
65 assert(_buf != NULL, "pre-condition");
66
67 void** buf = _buf;
68 size_t sz = _sz;
69
70 // Used for sanity checking at the end of the loop.
71 debug_only(size_t entries = 0; size_t retained = 0;)
72
73 size_t i = sz;
74 size_t new_index = sz;
75
76 // Given that we are expecting _index == 0, we could have changed
77 // the loop condition to (i > 0). But we are using _index for
78 // generality.
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 alwaysr 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 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 size_t perc = retained_calc * 100 / entries_calc;
113 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
114 _index = new_index;
115
116 return should_enqueue;
117 }
118
119 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
120 if (_buf != NULL) {
121 apply_closure_to_buffer(cl, _buf, _index, _sz);
122 _index = _sz;
123 }
124 }
125
126 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
127 void** buf, size_t index, size_t sz) {
128 if (cl == NULL) return;
129 for (size_t i = index; i < sz; i += oopSize) {
130 oop obj = (oop)buf[byte_index_to_index((int)i)];
131 // There can be NULL entries because of destructors.
132 if (obj != NULL) {
133 cl->do_object(obj);
134 }
135 }
136 }
137
138 #ifdef ASSERT
139 void ObjPtrQueue::verify_oops_in_buffer() {
140 if (_buf == NULL) return;
141 for (size_t i = _index; i < _sz; i += oopSize) {
142 oop obj = (oop)_buf[byte_index_to_index((int)i)];
143 assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
144 "Not an oop");
145 }
146 }
147 #endif
148
149 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
150 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
151 #endif // _MSC_VER
152
153
154 SATBMarkQueueSet::SATBMarkQueueSet() :
155 PtrQueueSet(),
156 _closure(NULL), _par_closures(NULL),
157 _shared_satb_queue(this, true /*perm*/)
158 {}
159
160 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
161 int process_completed_threshold,
162 Mutex* lock) {
163 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
164 _shared_satb_queue.set_lock(lock);
165 if (ParallelGCThreads > 0) {
166 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);
167 }
168 }
169
170
171 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
172 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
173 t->satb_mark_queue().handle_zero_index();
174 }
175
176 #ifdef ASSERT
177 void SATBMarkQueueSet::dump_active_values(JavaThread* first,
178 bool expected_active) {
179 gclog_or_tty->print_cr("SATB queue active values for Java Threads");
180 gclog_or_tty->print_cr(" SATB queue set: active is %s",
181 (is_active()) ? "TRUE" : "FALSE");
182 gclog_or_tty->print_cr(" expected_active is %s",
183 (expected_active) ? "TRUE" : "FALSE");
184 for (JavaThread* t = first; t; t = t->next()) {
185 bool active = t->satb_mark_queue().is_active();
186 gclog_or_tty->print_cr(" thread %s, active is %s",
187 t->name(), (active) ? "TRUE" : "FALSE");
188 }
189 }
190 #endif // ASSERT
191
192 void SATBMarkQueueSet::set_active_all_threads(bool b,
193 bool expected_active) {
194 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
195 JavaThread* first = Threads::first();
196
197 #ifdef ASSERT
198 if (_all_active != expected_active) {
199 dump_active_values(first, expected_active);
200
201 // I leave this here as a guarantee, instead of an assert, so
202 // that it will still be compiled in if we choose to uncomment
203 // the #ifdef ASSERT in a product build. The whole block is
204 // within an #ifdef ASSERT so the guarantee will not be compiled
205 // in a product build anyway.
206 guarantee(false,
207 "SATB queue set has an unexpected active value");
208 }
209 #endif // ASSERT
210 _all_active = b;
211
212 for (JavaThread* t = first; t; t = t->next()) {
213 #ifdef ASSERT
214 bool active = t->satb_mark_queue().is_active();
215 if (active != expected_active) {
216 dump_active_values(first, expected_active);
217
218 // I leave this here as a guarantee, instead of an assert, so
219 // that it will still be compiled in if we choose to uncomment
220 // the #ifdef ASSERT in a product build. The whole block is
221 // within an #ifdef ASSERT so the guarantee will not be compiled
222 // in a product build anyway.
223 guarantee(false,
224 "thread has an unexpected active value in its SATB queue");
225 }
226 #endif // ASSERT
227 t->satb_mark_queue().set_active(b);
228 }
229 }
230
231 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
232 _closure = closure;
233 }
234
235 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
236 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
237 _par_closures[i] = par_closure;
238 }
239
240 void SATBMarkQueueSet::iterate_closure_all_threads() {
241 for(JavaThread* t = Threads::first(); t; t = t->next()) {
242 t->satb_mark_queue().apply_closure(_closure);
243 }
244 shared_satb_queue()->apply_closure(_closure);
245 }
246
247 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
248 SharedHeap* sh = SharedHeap::heap();
249 int parity = sh->strong_roots_parity();
250
251 for(JavaThread* t = Threads::first(); t; t = t->next()) {
252 if (t->claim_oops_do(true, parity)) {
253 t->satb_mark_queue().apply_closure(_par_closures[worker]);
254 }
255 }
256
257 // We also need to claim the VMThread so that it's parity is updated
258 // otherwise the next call to Thread::possibly_parallel_oops_do inside
259 // a StrongRootsScope might skip the VMThread because it has a stale
260 // parity that matches the parity set by the StrongRootsScope
261 //
262 // Whichever worker succeeds in claiming the VMThread gets to do
263 // the shared queue.
264
265 VMThread* vmt = VMThread::vm_thread();
266 if (vmt->claim_oops_do(true, parity)) {
267 shared_satb_queue()->apply_closure(_par_closures[worker]);
268 }
269 }
270
271 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
272 int worker) {
273 BufferNode* nd = NULL;
274 {
275 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
276 if (_completed_buffers_head != NULL) {
277 nd = _completed_buffers_head;
278 _completed_buffers_head = nd->next();
279 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
280 _n_completed_buffers--;
281 if (_n_completed_buffers == 0) _process_completed = false;
282 }
283 }
284 ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
285 if (nd != NULL) {
286 void **buf = BufferNode::make_buffer_from_node(nd);
287 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
288 deallocate_buffer(buf);
289 return true;
290 } else {
291 return false;
292 }
293 }
294
295 void SATBMarkQueueSet::abandon_partial_marking() {
296 BufferNode* buffers_to_delete = NULL;
297 {
298 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
299 while (_completed_buffers_head != NULL) {
300 BufferNode* nd = _completed_buffers_head;
301 _completed_buffers_head = nd->next();
302 nd->set_next(buffers_to_delete);
303 buffers_to_delete = nd;
304 }
305 _completed_buffers_tail = NULL;
306 _n_completed_buffers = 0;
307 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
308 }
309 while (buffers_to_delete != NULL) {
310 BufferNode* nd = buffers_to_delete;
311 buffers_to_delete = nd->next();
312 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
313 }
314 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
315 // So we can safely manipulate these queues.
316 for (JavaThread* t = Threads::first(); t; t = t->next()) {
317 t->satb_mark_queue().reset();
318 }
319 shared_satb_queue()->reset();
320 }