1 /*
2 * Copyright (c) 2001, 2012, 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 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 PtrQueue::flush();
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 alwaysr 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(ObjectClosure* cl) {
148 if (_buf != NULL) {
149 apply_closure_to_buffer(cl, _buf, _index, _sz);
150 }
151 }
152
153 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {
154 if (_buf != NULL) {
155 apply_closure_to_buffer(cl, _buf, _index, _sz);
156 _index = _sz;
157 }
158 }
159
160 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
161 void** buf, size_t index, size_t sz) {
162 if (cl == NULL) return;
163 for (size_t i = index; i < sz; i += oopSize) {
164 oop obj = (oop)buf[byte_index_to_index((int)i)];
165 // There can be NULL entries because of destructors.
166 if (obj != NULL) {
167 cl->do_object(obj);
168 }
169 }
170 }
171
172 #ifndef PRODUCT
173 // Helpful for debugging
174
175 void ObjPtrQueue::print(const char* name) {
176 print(name, _buf, _index, _sz);
177 }
178
179 void ObjPtrQueue::print(const char* name,
180 void** buf, size_t index, size_t sz) {
181 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" "
182 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
183 name, buf, index, sz);
184 }
185 #endif // PRODUCT
186
187 #ifdef ASSERT
188 void ObjPtrQueue::verify_oops_in_buffer() {
189 if (_buf == NULL) return;
190 for (size_t i = _index; i < _sz; i += oopSize) {
191 oop obj = (oop)_buf[byte_index_to_index((int)i)];
192 assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
193 "Not an oop");
194 }
195 }
196 #endif
197
198 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
199 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
200 #endif // _MSC_VER
201
202 SATBMarkQueueSet::SATBMarkQueueSet() :
203 PtrQueueSet(), _closure(NULL), _par_closures(NULL),
204 _shared_satb_queue(this, true /*perm*/) { }
205
206 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
207 int process_completed_threshold,
208 Mutex* lock) {
209 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
210 _shared_satb_queue.set_lock(lock);
211 if (ParallelGCThreads > 0) {
212 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC);
213 }
214 }
215
216 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
217 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
218 t->satb_mark_queue().handle_zero_index();
219 }
220
221 #ifdef ASSERT
222 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
223 gclog_or_tty->print_cr("Expected SATB active state: %s",
224 expected_active ? "ACTIVE" : "INACTIVE");
225 gclog_or_tty->print_cr("Actual SATB active states:");
226 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
227 for (JavaThread* t = Threads::first(); t; t = t->next()) {
228 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
229 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
230 }
231 gclog_or_tty->print_cr(" Shared queue: %s",
232 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
233 }
234
235 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
236 // Verify queue set state
237 if (is_active() != expected_active) {
238 dump_active_states(expected_active);
239 guarantee(false, "SATB queue set has an unexpected active state");
240 }
241
242 // Verify thread queue states
243 for (JavaThread* t = Threads::first(); t; t = t->next()) {
244 if (t->satb_mark_queue().is_active() != expected_active) {
245 dump_active_states(expected_active);
246 guarantee(false, "Thread SATB queue has an unexpected active state");
247 }
248 }
249
250 // Verify shared queue state
251 if (shared_satb_queue()->is_active() != expected_active) {
252 dump_active_states(expected_active);
253 guarantee(false, "Shared SATB queue has an unexpected active state");
254 }
255 }
256 #endif // ASSERT
257
258 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
259 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
260 #ifdef ASSERT
261 verify_active_states(expected_active);
262 #endif // ASSERT
263 _all_active = active;
264 for (JavaThread* t = Threads::first(); t; t = t->next()) {
265 t->satb_mark_queue().set_active(active);
266 }
267 shared_satb_queue()->set_active(active);
268 }
269
270 void SATBMarkQueueSet::filter_thread_buffers() {
271 for(JavaThread* t = Threads::first(); t; t = t->next()) {
272 t->satb_mark_queue().filter();
273 }
274 shared_satb_queue()->filter();
275 }
276
277 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
278 _closure = closure;
279 }
280
281 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
282 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
283 _par_closures[i] = par_closure;
284 }
285
286 void SATBMarkQueueSet::iterate_closure_all_threads() {
287 for(JavaThread* t = Threads::first(); t; t = t->next()) {
288 t->satb_mark_queue().apply_closure_and_empty(_closure);
289 }
290 shared_satb_queue()->apply_closure_and_empty(_closure);
291 }
292
293 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
294 SharedHeap* sh = SharedHeap::heap();
295 int parity = sh->strong_roots_parity();
296
297 for(JavaThread* t = Threads::first(); t; t = t->next()) {
298 if (t->claim_oops_do(true, parity)) {
299 t->satb_mark_queue().apply_closure_and_empty(_par_closures[worker]);
300 }
301 }
302
303 // We also need to claim the VMThread so that its parity is updated
304 // otherwise the next call to Thread::possibly_parallel_oops_do inside
305 // a StrongRootsScope might skip the VMThread because it has a stale
306 // parity that matches the parity set by the StrongRootsScope
307 //
308 // Whichever worker succeeds in claiming the VMThread gets to do
309 // the shared queue.
310
311 VMThread* vmt = VMThread::vm_thread();
312 if (vmt->claim_oops_do(true, parity)) {
313 shared_satb_queue()->apply_closure_and_empty(_par_closures[worker]);
314 }
315 }
316
317 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
318 int worker) {
319 BufferNode* nd = NULL;
320 {
321 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
322 if (_completed_buffers_head != NULL) {
323 nd = _completed_buffers_head;
324 _completed_buffers_head = nd->next();
325 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
326 _n_completed_buffers--;
327 if (_n_completed_buffers == 0) _process_completed = false;
328 }
329 }
330 ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
331 if (nd != NULL) {
332 void **buf = BufferNode::make_buffer_from_node(nd);
333 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
334 deallocate_buffer(buf);
335 return true;
336 } else {
337 return false;
338 }
339 }
340
341 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {
342 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
343 assert(cl != NULL, "pre-condition");
344
345 BufferNode* nd = _completed_buffers_head;
346 while (nd != NULL) {
347 void** buf = BufferNode::make_buffer_from_node(nd);
348 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
349 nd = nd->next();
350 }
351 }
352
353 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {
354 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
355 assert(cl != NULL, "pre-condition");
356
357 for (JavaThread* t = Threads::first(); t; t = t->next()) {
358 t->satb_mark_queue().apply_closure(cl);
359 }
360 shared_satb_queue()->apply_closure(cl);
361 }
362
363 #ifndef PRODUCT
364 // Helpful for debugging
365
366 #define SATB_PRINTER_BUFFER_SIZE 256
367
368 void SATBMarkQueueSet::print_all(const char* msg) {
369 char buffer[SATB_PRINTER_BUFFER_SIZE];
370 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
371
372 gclog_or_tty->cr();
373 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
374
375 BufferNode* nd = _completed_buffers_head;
376 int i = 0;
377 while (nd != NULL) {
378 void** buf = BufferNode::make_buffer_from_node(nd);
379 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
380 ObjPtrQueue::print(buffer, buf, 0, _sz);
381 nd = nd->next();
382 i += 1;
383 }
384
385 for (JavaThread* t = Threads::first(); t; t = t->next()) {
386 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
387 t->satb_mark_queue().print(buffer);
388 }
389
390 shared_satb_queue()->print("Shared");
391
392 gclog_or_tty->cr();
393 }
394 #endif // PRODUCT
395
396 void SATBMarkQueueSet::abandon_partial_marking() {
397 BufferNode* buffers_to_delete = NULL;
398 {
399 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
400 while (_completed_buffers_head != NULL) {
401 BufferNode* nd = _completed_buffers_head;
402 _completed_buffers_head = nd->next();
403 nd->set_next(buffers_to_delete);
404 buffers_to_delete = nd;
405 }
406 _completed_buffers_tail = NULL;
407 _n_completed_buffers = 0;
408 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
409 }
410 while (buffers_to_delete != NULL) {
411 BufferNode* nd = buffers_to_delete;
412 buffers_to_delete = nd->next();
413 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
414 }
415 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
416 // So we can safely manipulate these queues.
417 for (JavaThread* t = Threads::first(); t; t = t->next()) {
418 t->satb_mark_queue().reset();
419 }
420 shared_satb_queue()->reset();
421 }