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 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
201 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
202 #endif // _MSC_VER
203
204 SATBMarkQueueSet::SATBMarkQueueSet() :
205 PtrQueueSet(), _closure(NULL), _par_closures(NULL),
206 _shared_satb_queue(this, true /*perm*/) { }
207
208 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
209 int process_completed_threshold,
210 Mutex* lock) {
211 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
212 _shared_satb_queue.set_lock(lock);
213 if (ParallelGCThreads > 0) {
214 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC);
215 }
216 }
217
218 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
219 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
220 t->satb_mark_queue().handle_zero_index();
221 }
222
223 #ifdef ASSERT
224 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
225 gclog_or_tty->print_cr("Expected SATB active state: %s",
226 expected_active ? "ACTIVE" : "INACTIVE");
227 gclog_or_tty->print_cr("Actual SATB active states:");
228 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
229 for (JavaThread* t = Threads::first(); t; t = t->next()) {
230 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(),
231 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
232 }
233 gclog_or_tty->print_cr(" Shared queue: %s",
234 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
235 }
236
237 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
238 // Verify queue set state
239 if (is_active() != expected_active) {
240 dump_active_states(expected_active);
241 guarantee(false, "SATB queue set has an unexpected active state");
242 }
243
244 // Verify thread queue states
245 for (JavaThread* t = Threads::first(); t; t = t->next()) {
246 if (t->satb_mark_queue().is_active() != expected_active) {
247 dump_active_states(expected_active);
248 guarantee(false, "Thread SATB queue has an unexpected active state");
249 }
250 }
251
252 // Verify shared queue state
253 if (shared_satb_queue()->is_active() != expected_active) {
254 dump_active_states(expected_active);
255 guarantee(false, "Shared SATB queue has an unexpected active state");
256 }
257 }
258 #endif // ASSERT
259
260 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
261 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
262 #ifdef ASSERT
263 verify_active_states(expected_active);
264 #endif // ASSERT
265 _all_active = active;
266 for (JavaThread* t = Threads::first(); t; t = t->next()) {
267 t->satb_mark_queue().set_active(active);
268 }
269 shared_satb_queue()->set_active(active);
270 }
271
272 void SATBMarkQueueSet::filter_thread_buffers() {
273 for(JavaThread* t = Threads::first(); t; t = t->next()) {
274 t->satb_mark_queue().filter();
275 }
276 shared_satb_queue()->filter();
277 }
278
279 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
280 _closure = closure;
281 }
282
283 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
284 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
285 _par_closures[i] = par_closure;
286 }
287
288 void SATBMarkQueueSet::iterate_closure_all_threads() {
289 for(JavaThread* t = Threads::first(); t; t = t->next()) {
290 t->satb_mark_queue().apply_closure_and_empty(_closure);
291 }
292 shared_satb_queue()->apply_closure_and_empty(_closure);
293 }
294
295 void SATBMarkQueueSet::par_iterate_closure_all_threads(uint worker) {
296 SharedHeap* sh = SharedHeap::heap();
297 int parity = sh->strong_roots_parity();
298
299 for(JavaThread* t = Threads::first(); t; t = t->next()) {
300 if (t->claim_oops_do(true, parity)) {
301 t->satb_mark_queue().apply_closure_and_empty(_par_closures[worker]);
302 }
303 }
304
305 // We also need to claim the VMThread so that its parity is updated
306 // otherwise the next call to Thread::possibly_parallel_oops_do inside
307 // a StrongRootsScope might skip the VMThread because it has a stale
308 // parity that matches the parity set by the StrongRootsScope
309 //
310 // Whichever worker succeeds in claiming the VMThread gets to do
311 // the shared queue.
312
313 VMThread* vmt = VMThread::vm_thread();
314 if (vmt->claim_oops_do(true, parity)) {
315 shared_satb_queue()->apply_closure_and_empty(_par_closures[worker]);
316 }
317 }
318
319 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
320 uint worker) {
321 BufferNode* nd = NULL;
322 {
323 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
324 if (_completed_buffers_head != NULL) {
325 nd = _completed_buffers_head;
326 _completed_buffers_head = nd->next();
327 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
328 _n_completed_buffers--;
329 if (_n_completed_buffers == 0) _process_completed = false;
330 }
331 }
332 ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
333 if (nd != NULL) {
334 void **buf = BufferNode::make_buffer_from_node(nd);
335 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
336 deallocate_buffer(buf);
337 return true;
338 } else {
339 return false;
340 }
341 }
342
343 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {
344 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
345 assert(cl != NULL, "pre-condition");
346
347 BufferNode* nd = _completed_buffers_head;
348 while (nd != NULL) {
349 void** buf = BufferNode::make_buffer_from_node(nd);
350 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
351 nd = nd->next();
352 }
353 }
354
355 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {
356 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
357 assert(cl != NULL, "pre-condition");
358
359 for (JavaThread* t = Threads::first(); t; t = t->next()) {
360 t->satb_mark_queue().apply_closure(cl);
361 }
362 shared_satb_queue()->apply_closure(cl);
363 }
364
365 #ifndef PRODUCT
366 // Helpful for debugging
367
368 #define SATB_PRINTER_BUFFER_SIZE 256
369
370 void SATBMarkQueueSet::print_all(const char* msg) {
371 char buffer[SATB_PRINTER_BUFFER_SIZE];
372 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
373
374 gclog_or_tty->cr();
375 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
376
377 BufferNode* nd = _completed_buffers_head;
378 int i = 0;
379 while (nd != NULL) {
380 void** buf = BufferNode::make_buffer_from_node(nd);
381 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
382 ObjPtrQueue::print(buffer, buf, 0, _sz);
383 nd = nd->next();
384 i += 1;
385 }
386
387 for (JavaThread* t = Threads::first(); t; t = t->next()) {
388 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
389 t->satb_mark_queue().print(buffer);
390 }
391
392 shared_satb_queue()->print("Shared");
393
394 gclog_or_tty->cr();
395 }
396 #endif // PRODUCT
397
398 void SATBMarkQueueSet::abandon_partial_marking() {
399 BufferNode* buffers_to_delete = NULL;
400 {
401 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
402 while (_completed_buffers_head != NULL) {
403 BufferNode* nd = _completed_buffers_head;
404 _completed_buffers_head = nd->next();
405 nd->set_next(buffers_to_delete);
406 buffers_to_delete = nd;
407 }
408 _completed_buffers_tail = NULL;
409 _n_completed_buffers = 0;
410 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
411 }
412 while (buffers_to_delete != NULL) {
413 BufferNode* nd = buffers_to_delete;
414 buffers_to_delete = nd->next();
415 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
416 }
417 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
418 // So we can safely manipulate these queues.
419 for (JavaThread* t = Threads::first(); t; t = t->next()) {
420 t->satb_mark_queue().reset();
421 }
422 shared_satb_queue()->reset();
423 }