Fri, 18 Feb 2011 10:07:34 -0800
7020042: G1: Partially remove fix for 6994628
Summary: Disable reference discovery and processing during concurrent marking by disabling fix for 6994628.
Reviewed-by: tonyp, ysr
1 /*
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23 */
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"
33 // This method removes entries from an SATB buffer that will not be
34 // useful to the concurrent marking threads. An entry is removed if it
35 // satisfies one of the following conditions:
36 //
37 // * it points to an object outside the G1 heap (G1's concurrent
38 // marking only visits objects inside the G1 heap),
39 // * it points to an object that has been allocated since marking
40 // started (according to SATB those objects do not need to be
41 // visited during marking), or
42 // * it points to an object that has already been marked (no need to
43 // process it again).
44 //
45 // The rest of the entries will be retained and are compacted towards
46 // the top of the buffer. If with this filtering we clear a large
47 // enough chunk of the buffer we can re-use it (instead of enqueueing
48 // it) and we can just allow the mutator to carry on executing.
50 bool ObjPtrQueue::should_enqueue_buffer() {
51 assert(_lock == NULL || _lock->owned_by_self(),
52 "we should have taken the lock before calling this");
54 // A value of 0 means "don't filter SATB buffers".
55 if (G1SATBBufferEnqueueingThresholdPercent == 0) {
56 return true;
57 }
59 G1CollectedHeap* g1h = G1CollectedHeap::heap();
61 // This method should only be called if there is a non-NULL buffer
62 // that is full.
63 assert(_index == 0, "pre-condition");
64 assert(_buf != NULL, "pre-condition");
66 void** buf = _buf;
67 size_t sz = _sz;
69 // Used for sanity checking at the end of the loop.
70 debug_only(size_t entries = 0; size_t retained = 0;)
72 size_t i = sz;
73 size_t new_index = sz;
75 // Given that we are expecting _index == 0, we could have changed
76 // the loop condition to (i > 0). But we are using _index for
77 // generality.
78 while (i > _index) {
79 assert(i > 0, "we should have at least one more entry to process");
80 i -= oopSize;
81 debug_only(entries += 1;)
82 oop* p = (oop*) &buf[byte_index_to_index((int) i)];
83 oop obj = *p;
84 // NULL the entry so that unused parts of the buffer contain NULLs
85 // at the end. If we are going to retain it we will copy it to its
86 // final place. If we have retained all entries we have visited so
87 // far, we'll just end up copying it to the same place.
88 *p = NULL;
90 bool retain = g1h->is_obj_ill(obj);
91 if (retain) {
92 assert(new_index > 0, "we should not have already filled up the buffer");
93 new_index -= oopSize;
94 assert(new_index >= i,
95 "new_index should never be below i, as we alwaysr compact 'up'");
96 oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
97 assert(new_p >= p, "the destination location should never be below "
98 "the source as we always compact 'up'");
99 assert(*new_p == NULL,
100 "we should have already cleared the destination location");
101 *new_p = obj;
102 debug_only(retained += 1;)
103 }
104 }
105 size_t entries_calc = (sz - _index) / oopSize;
106 assert(entries == entries_calc, "the number of entries we counted "
107 "should match the number of entries we calculated");
108 size_t retained_calc = (sz - new_index) / oopSize;
109 assert(retained == retained_calc, "the number of retained entries we counted "
110 "should match the number of retained entries we calculated");
111 size_t perc = retained_calc * 100 / entries_calc;
112 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
113 _index = new_index;
115 return should_enqueue;
116 }
118 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
119 if (_buf != NULL) {
120 apply_closure_to_buffer(cl, _buf, _index, _sz);
121 _index = _sz;
122 }
123 }
125 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
126 void** buf, size_t index, size_t sz) {
127 if (cl == NULL) return;
128 for (size_t i = index; i < sz; i += oopSize) {
129 oop obj = (oop)buf[byte_index_to_index((int)i)];
130 // There can be NULL entries because of destructors.
131 if (obj != NULL) {
132 cl->do_object(obj);
133 }
134 }
135 }
137 #ifdef ASSERT
138 void ObjPtrQueue::verify_oops_in_buffer() {
139 if (_buf == NULL) return;
140 for (size_t i = _index; i < _sz; i += oopSize) {
141 oop obj = (oop)_buf[byte_index_to_index((int)i)];
142 assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
143 "Not an oop");
144 }
145 }
146 #endif
148 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
149 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
150 #endif // _MSC_VER
153 SATBMarkQueueSet::SATBMarkQueueSet() :
154 PtrQueueSet(),
155 _closure(NULL), _par_closures(NULL),
156 _shared_satb_queue(this, true /*perm*/)
157 {}
159 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
160 int process_completed_threshold,
161 Mutex* lock) {
162 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
163 _shared_satb_queue.set_lock(lock);
164 if (ParallelGCThreads > 0) {
165 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);
166 }
167 }
170 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
171 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
172 t->satb_mark_queue().handle_zero_index();
173 }
175 #ifdef ASSERT
176 void SATBMarkQueueSet::dump_active_values(JavaThread* first,
177 bool expected_active) {
178 gclog_or_tty->print_cr("SATB queue active values for Java Threads");
179 gclog_or_tty->print_cr(" SATB queue set: active is %s",
180 (is_active()) ? "TRUE" : "FALSE");
181 gclog_or_tty->print_cr(" expected_active is %s",
182 (expected_active) ? "TRUE" : "FALSE");
183 for (JavaThread* t = first; t; t = t->next()) {
184 bool active = t->satb_mark_queue().is_active();
185 gclog_or_tty->print_cr(" thread %s, active is %s",
186 t->name(), (active) ? "TRUE" : "FALSE");
187 }
188 }
189 #endif // ASSERT
191 void SATBMarkQueueSet::set_active_all_threads(bool b,
192 bool expected_active) {
193 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
194 JavaThread* first = Threads::first();
196 #ifdef ASSERT
197 if (_all_active != expected_active) {
198 dump_active_values(first, expected_active);
200 // I leave this here as a guarantee, instead of an assert, so
201 // that it will still be compiled in if we choose to uncomment
202 // the #ifdef ASSERT in a product build. The whole block is
203 // within an #ifdef ASSERT so the guarantee will not be compiled
204 // in a product build anyway.
205 guarantee(false,
206 "SATB queue set has an unexpected active value");
207 }
208 #endif // ASSERT
209 _all_active = b;
211 for (JavaThread* t = first; t; t = t->next()) {
212 #ifdef ASSERT
213 bool active = t->satb_mark_queue().is_active();
214 if (active != expected_active) {
215 dump_active_values(first, expected_active);
217 // I leave this here as a guarantee, instead of an assert, so
218 // that it will still be compiled in if we choose to uncomment
219 // the #ifdef ASSERT in a product build. The whole block is
220 // within an #ifdef ASSERT so the guarantee will not be compiled
221 // in a product build anyway.
222 guarantee(false,
223 "thread has an unexpected active value in its SATB queue");
224 }
225 #endif // ASSERT
226 t->satb_mark_queue().set_active(b);
227 }
228 }
230 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
231 _closure = closure;
232 }
234 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
235 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
236 _par_closures[i] = par_closure;
237 }
239 void SATBMarkQueueSet::iterate_closure_all_threads() {
240 for(JavaThread* t = Threads::first(); t; t = t->next()) {
241 t->satb_mark_queue().apply_closure(_closure);
242 }
243 shared_satb_queue()->apply_closure(_closure);
244 }
246 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
247 SharedHeap* sh = SharedHeap::heap();
248 int parity = sh->strong_roots_parity();
250 for(JavaThread* t = Threads::first(); t; t = t->next()) {
251 if (t->claim_oops_do(true, parity)) {
252 t->satb_mark_queue().apply_closure(_par_closures[worker]);
253 }
254 }
255 // We'll have worker 0 do this one.
256 if (worker == 0) {
257 shared_satb_queue()->apply_closure(_par_closures[0]);
258 }
259 }
261 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
262 int worker) {
263 BufferNode* nd = NULL;
264 {
265 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
266 if (_completed_buffers_head != NULL) {
267 nd = _completed_buffers_head;
268 _completed_buffers_head = nd->next();
269 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
270 _n_completed_buffers--;
271 if (_n_completed_buffers == 0) _process_completed = false;
272 }
273 }
274 ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
275 if (nd != NULL) {
276 void **buf = BufferNode::make_buffer_from_node(nd);
277 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
278 deallocate_buffer(buf);
279 return true;
280 } else {
281 return false;
282 }
283 }
285 void SATBMarkQueueSet::abandon_partial_marking() {
286 BufferNode* buffers_to_delete = NULL;
287 {
288 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
289 while (_completed_buffers_head != NULL) {
290 BufferNode* nd = _completed_buffers_head;
291 _completed_buffers_head = nd->next();
292 nd->set_next(buffers_to_delete);
293 buffers_to_delete = nd;
294 }
295 _completed_buffers_tail = NULL;
296 _n_completed_buffers = 0;
297 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
298 }
299 while (buffers_to_delete != NULL) {
300 BufferNode* nd = buffers_to_delete;
301 buffers_to_delete = nd->next();
302 deallocate_buffer(BufferNode::make_buffer_from_node(nd));
303 }
304 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
305 // So we can safely manipulate these queues.
306 for (JavaThread* t = Threads::first(); t; t = t->next()) {
307 t->satb_mark_queue().reset();
308 }
309 shared_satb_queue()->reset();
310 }