1 /*
2 * Copyright (c) 2014, 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/g1/g1Allocator.inline.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1EvacuationClosures.hpp"
29 #include "gc/g1/g1OopClosures.inline.hpp"
30 #include "gc/g1/g1ParScanThreadState.inline.hpp"
31 #include "gc/g1/g1StringDedup.hpp"
32 #include "gc/shared/taskqueue.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/prefetch.inline.hpp"
35
36 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
37 : _g1h(g1h),
38 _refs(g1h->task_queue(worker_id)),
39 _dcq(&g1h->dirty_card_queue_set()),
40 _ct_bs(g1h->g1_barrier_set()),
41 _closures(NULL),
42 _hash_seed(17),
43 _worker_id(worker_id),
44 _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
45 _age_table(false),
46 _scanner(g1h),
47 _old_gen_is_full(false)
48 {
49 _scanner.set_par_scan_thread_state(this);
50 // we allocate G1YoungSurvRateNumRegions plus one entries, since
51 // we "sacrifice" entry 0 to keep track of surviving bytes for
52 // non-young regions (where the age is -1)
53 // We also add a few elements at the beginning and at the end in
54 // an attempt to eliminate cache contention
55 size_t real_length = 1 + young_cset_length;
56 size_t array_length = PADDING_ELEM_NUM +
57 real_length +
58 PADDING_ELEM_NUM;
59 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
60 if (_surviving_young_words_base == NULL)
61 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
62 "Not enough space for young surv histo.");
63 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
64 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
65
66 _plab_allocator = G1PLABAllocator::create_allocator(_g1h->allocator());
67
68 _dest[InCSetState::NotInCSet] = InCSetState::NotInCSet;
69 // The dest for Young is used when the objects are aged enough to
70 // need to be moved to the next space.
71 _dest[InCSetState::Young] = InCSetState::Old;
72 _dest[InCSetState::Old] = InCSetState::Old;
73
74 _closures = new_root_closures();
75 }
76
77 G1EvacuationRootClosures* G1ParScanThreadState::new_root_closures() {
78 if (_g1h->collector_state()->during_initial_mark_pause()) {
79 if (ClassUnloadingWithConcurrentMark) {
80 return new G1InitalMarkClosures<G1MarkPromotedFromRoot>(_g1h, this);
81 } else {
82 return new G1InitalMarkClosures<G1MarkFromRoot>(_g1h, this);
83 }
84 } else {
85 return new G1EvacuationClosures(_g1h, this, _g1h->collector_state()->gcs_are_young());
86 }
87 }
88
89 // Pass locally gathered statistics to global state.
90 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
91 _dcq.flush();
92 // Update allocation statistics.
93 _plab_allocator->flush_and_retire_stats();
94 _g1h->g1_policy()->record_age_table(&_age_table);
95
96 uint length = _g1h->g1_policy()->young_cset_region_length();
97 for (uint region_index = 0; region_index < length; region_index++) {
98 surviving_young_words[region_index] += _surviving_young_words[region_index];
99 }
100 }
101
102 G1ParScanThreadState::~G1ParScanThreadState() {
103 delete _plab_allocator;
104 delete _closures;
105 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
106 }
107
108 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
109 _plab_allocator->waste(wasted, undo_wasted);
110 }
111
112 #ifdef ASSERT
113 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
114 assert(ref != NULL, "invariant");
115 assert(UseCompressedOops, "sanity");
116 assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
117 oop p = oopDesc::load_decode_heap_oop(ref);
118 assert(_g1h->is_in_g1_reserved(p),
119 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
120 return true;
121 }
122
123 bool G1ParScanThreadState::verify_ref(oop* ref) const {
124 assert(ref != NULL, "invariant");
125 if (has_partial_array_mask(ref)) {
126 // Must be in the collection set--it's already been copied.
127 oop p = clear_partial_array_mask(ref);
128 assert(_g1h->obj_in_cs(p),
129 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
130 } else {
131 oop p = oopDesc::load_decode_heap_oop(ref);
132 assert(_g1h->is_in_g1_reserved(p),
133 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
134 }
135 return true;
136 }
137
138 bool G1ParScanThreadState::verify_task(StarTask ref) const {
139 if (ref.is_narrow()) {
140 return verify_ref((narrowOop*) ref);
141 } else {
142 return verify_ref((oop*) ref);
143 }
144 }
145 #endif // ASSERT
146
147 void G1ParScanThreadState::trim_queue() {
148 StarTask ref;
149 do {
150 // Drain the overflow stack first, so other threads can steal.
151 while (_refs->pop_overflow(ref)) {
152 dispatch_reference(ref);
153 }
154
155 while (_refs->pop_local(ref)) {
156 dispatch_reference(ref);
157 }
158 } while (!_refs->is_empty());
159 }
160
161 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
162 InCSetState* dest,
163 size_t word_sz,
164 AllocationContext_t const context,
165 bool previous_plab_refill_failed) {
166 assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
167 assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
168
169 // Right now we only have two types of regions (young / old) so
170 // let's keep the logic here simple. We can generalize it when necessary.
171 if (dest->is_young()) {
172 bool plab_refill_in_old_failed = false;
173 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
174 word_sz,
175 context,
176 &plab_refill_in_old_failed);
177 // Make sure that we won't attempt to copy any other objects out
178 // of a survivor region (given that apparently we cannot allocate
179 // any new ones) to avoid coming into this slow path again and again.
180 // Only consider failed PLAB refill here: failed inline allocations are
181 // typically large, so not indicative of remaining space.
182 if (previous_plab_refill_failed) {
183 _tenuring_threshold = 0;
184 }
185
186 if (obj_ptr != NULL) {
187 dest->set_old();
188 } else {
189 // We just failed to allocate in old gen. The same idea as explained above
190 // for making survivor gen unavailable for allocation applies for old gen.
191 _old_gen_is_full = plab_refill_in_old_failed;
192 }
193 return obj_ptr;
194 } else {
195 _old_gen_is_full = previous_plab_refill_failed;
196 assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
197 // no other space to try.
198 return NULL;
199 }
200 }
201
202 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
203 if (state.is_young()) {
204 age = !m->has_displaced_mark_helper() ? m->age()
205 : m->displaced_mark_helper()->age();
206 if (age < _tenuring_threshold) {
207 return state;
208 }
209 }
210 return dest(state);
211 }
212
213 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
214 oop const old, size_t word_sz, uint age,
215 HeapWord * const obj_ptr,
216 const AllocationContext_t context) const {
217 G1PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state, context);
218 if (alloc_buf->contains(obj_ptr)) {
219 _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
220 dest_state.value() == InCSetState::Old,
221 alloc_buf->word_sz());
222 } else {
223 _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
224 dest_state.value() == InCSetState::Old);
225 }
226 }
227
228 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
229 oop const old,
230 markOop const old_mark) {
231 const size_t word_sz = old->size();
232 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
233 // +1 to make the -1 indexes valid...
234 const int young_index = from_region->young_index_in_cset()+1;
235 assert( (from_region->is_young() && young_index > 0) ||
236 (!from_region->is_young() && young_index == 0), "invariant" );
237 const AllocationContext_t context = from_region->allocation_context();
238
239 uint age = 0;
240 InCSetState dest_state = next_state(state, old_mark, age);
241 // The second clause is to prevent premature evacuation failure in case there
242 // is still space in survivor, but old gen is full.
243 if (_old_gen_is_full && dest_state.is_old()) {
244 return handle_evacuation_failure_par(old, old_mark);
245 }
246 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
247
248 // PLAB allocations should succeed most of the time, so we'll
249 // normally check against NULL once and that's it.
250 if (obj_ptr == NULL) {
251 bool plab_refill_failed = false;
252 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
253 if (obj_ptr == NULL) {
254 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
255 if (obj_ptr == NULL) {
256 // This will either forward-to-self, or detect that someone else has
257 // installed a forwarding pointer.
258 return handle_evacuation_failure_par(old, old_mark);
259 }
260 }
261 if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
262 // The events are checked individually as part of the actual commit
263 report_promotion_event(dest_state, old, word_sz, age, obj_ptr, context);
264 }
265 }
266
267 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
268 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
269
270 #ifndef PRODUCT
271 // Should this evacuation fail?
272 if (_g1h->evacuation_should_fail()) {
273 // Doing this after all the allocation attempts also tests the
274 // undo_allocation() method too.
275 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
276 return handle_evacuation_failure_par(old, old_mark);
277 }
278 #endif // !PRODUCT
279
280 // We're going to allocate linearly, so might as well prefetch ahead.
281 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
282
283 const oop obj = oop(obj_ptr);
284 const oop forward_ptr = old->forward_to_atomic(obj);
285 if (forward_ptr == NULL) {
286 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
287
288 if (dest_state.is_young()) {
289 if (age < markOopDesc::max_age) {
290 age++;
291 }
292 if (old_mark->has_displaced_mark_helper()) {
293 // In this case, we have to install the mark word first,
294 // otherwise obj looks to be forwarded (the old mark word,
295 // which contains the forward pointer, was copied)
296 obj->set_mark(old_mark);
297 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
298 old_mark->set_displaced_mark_helper(new_mark);
299 } else {
300 obj->set_mark(old_mark->set_age(age));
301 }
302 _age_table.add(age, word_sz);
303 } else {
304 obj->set_mark(old_mark);
305 }
306
307 if (G1StringDedup::is_enabled()) {
308 const bool is_from_young = state.is_young();
309 const bool is_to_young = dest_state.is_young();
310 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
311 "sanity");
312 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
313 "sanity");
314 G1StringDedup::enqueue_from_evacuation(is_from_young,
315 is_to_young,
316 _worker_id,
317 obj);
318 }
319
320 _surviving_young_words[young_index] += word_sz;
321
322 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
323 // We keep track of the next start index in the length field of
324 // the to-space object. The actual length can be found in the
325 // length field of the from-space object.
326 arrayOop(obj)->set_length(0);
327 oop* old_p = set_partial_array_mask(old);
328 push_on_queue(old_p);
329 } else {
330 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
331 _scanner.set_region(to_region);
332 obj->oop_iterate_backwards(&_scanner);
333 }
334 return obj;
335 } else {
336 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
337 return forward_ptr;
338 }
339 }
340
341 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
342 assert(worker_id < _n_workers, "out of bounds access");
343 return _states[worker_id];
344 }
345
346 void G1ParScanThreadStateSet::add_cards_scanned(uint worker_id, size_t cards_scanned) {
347 assert(worker_id < _n_workers, "out of bounds access");
348 _cards_scanned[worker_id] += cards_scanned;
349 }
350
351 size_t G1ParScanThreadStateSet::total_cards_scanned() const {
352 assert(_flushed, "thread local state from the per thread states should have been flushed");
353 return _total_cards_scanned;
354 }
355
356 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
357 assert(_flushed, "thread local state from the per thread states should have been flushed");
358 return _surviving_young_words_total;
359 }
360
361 void G1ParScanThreadStateSet::flush() {
362 assert(!_flushed, "thread local state from the per thread states should be flushed once");
363 assert(_total_cards_scanned == 0, "should have been cleared");
364
365 for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
366 G1ParScanThreadState* pss = _states[worker_index];
367
368 _total_cards_scanned += _cards_scanned[worker_index];
369
370 pss->flush(_surviving_young_words_total);
371 delete pss;
372 _states[worker_index] = NULL;
373 }
374 _flushed = true;
375 }
376
377 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
378 assert(_g1h->obj_in_cs(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
379
380 oop forward_ptr = old->forward_to_atomic(old);
381 if (forward_ptr == NULL) {
382 // Forward-to-self succeeded. We are the "owner" of the object.
383 HeapRegion* r = _g1h->heap_region_containing(old);
384
385 if (!r->evacuation_failed()) {
386 r->set_evacuation_failed(true);
387 _g1h->hr_printer()->evac_failure(r);
388 }
389
390 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
391
392 _scanner.set_region(r);
393 old->oop_iterate_backwards(&_scanner);
394
395 return old;
396 } else {
397 // Forward-to-self failed. Either someone else managed to allocate
398 // space for this object (old != forward_ptr) or they beat us in
399 // self-forwarding it (old == forward_ptr).
400 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
401 "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
402 "should not be in the CSet",
403 p2i(old), p2i(forward_ptr));
404 return forward_ptr;
405 }
406 }
407