1 /*
2 * Copyright (c) 2014, 2016, 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/g1CollectionSet.hpp"
29 #include "gc/g1/g1OopClosures.inline.hpp"
30 #include "gc/g1/g1ParScanThreadState.inline.hpp"
31 #include "gc/g1/g1RootClosures.hpp"
32 #include "gc/g1/g1StringDedup.hpp"
33 #include "gc/shared/taskqueue.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/prefetch.inline.hpp"
36
37 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
38 : _g1h(g1h),
39 _refs(g1h->task_queue(worker_id)),
40 _dcq(&g1h->dirty_card_queue_set()),
41 _ct_bs(g1h->g1_barrier_set()),
42 _closures(NULL),
43 _hash_seed(17),
44 _worker_id(worker_id),
45 _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
46 _age_table(false),
47 _scanner(g1h, this),
48 _old_gen_is_full(false)
49 {
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 = G1EvacuationRootClosures::create_root_closures(this, _g1h);
75 }
76
77 // Pass locally gathered statistics to global state.
78 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
79 _dcq.flush();
80 // Update allocation statistics.
81 _plab_allocator->flush_and_retire_stats();
82 _g1h->g1_policy()->record_age_table(&_age_table);
83
84 uint length = _g1h->collection_set()->young_region_length();
85 for (uint region_index = 0; region_index < length; region_index++) {
86 surviving_young_words[region_index] += _surviving_young_words[region_index];
87 }
88 }
89
90 G1ParScanThreadState::~G1ParScanThreadState() {
91 delete _plab_allocator;
92 delete _closures;
93 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
94 }
95
96 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
97 _plab_allocator->waste(wasted, undo_wasted);
98 }
99
100 #ifdef ASSERT
101 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
102 assert(ref != NULL, "invariant");
103 assert(UseCompressedOops, "sanity");
104 assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
105 oop p = oopDesc::load_decode_heap_oop(ref);
106 assert(_g1h->is_in_g1_reserved(p),
107 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
108 return true;
109 }
110
111 bool G1ParScanThreadState::verify_ref(oop* ref) const {
112 assert(ref != NULL, "invariant");
113 if (has_partial_array_mask(ref)) {
114 // Must be in the collection set--it's already been copied.
115 oop p = clear_partial_array_mask(ref);
116 assert(_g1h->obj_in_cs(p),
117 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
118 } else {
119 oop p = oopDesc::load_decode_heap_oop(ref);
120 assert(_g1h->is_in_g1_reserved(p),
121 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
122 }
123 return true;
124 }
125
126 bool G1ParScanThreadState::verify_task(StarTask ref) const {
127 if (ref.is_narrow()) {
128 return verify_ref((narrowOop*) ref);
129 } else {
130 return verify_ref((oop*) ref);
131 }
132 }
133 #endif // ASSERT
134
135 void G1ParScanThreadState::trim_queue() {
136 StarTask ref;
137 do {
138 // Drain the overflow stack first, so other threads can steal.
139 while (_refs->pop_overflow(ref)) {
140 if (!_refs->try_push_to_taskqueue(ref)) {
141 dispatch_reference(ref);
142 }
143 }
144
145 while (_refs->pop_local(ref)) {
146 dispatch_reference(ref);
147 }
148 } while (!_refs->is_empty());
149 }
150
151 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
152 InCSetState* dest,
153 size_t word_sz,
154 AllocationContext_t const context,
155 bool previous_plab_refill_failed) {
156 assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
157 assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
158
159 // Right now we only have two types of regions (young / old) so
160 // let's keep the logic here simple. We can generalize it when necessary.
161 if (dest->is_young()) {
162 bool plab_refill_in_old_failed = false;
163 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
164 word_sz,
165 context,
166 &plab_refill_in_old_failed);
167 // Make sure that we won't attempt to copy any other objects out
168 // of a survivor region (given that apparently we cannot allocate
169 // any new ones) to avoid coming into this slow path again and again.
170 // Only consider failed PLAB refill here: failed inline allocations are
171 // typically large, so not indicative of remaining space.
172 if (previous_plab_refill_failed) {
173 _tenuring_threshold = 0;
174 }
175
176 if (obj_ptr != NULL) {
177 dest->set_old();
178 } else {
179 // We just failed to allocate in old gen. The same idea as explained above
180 // for making survivor gen unavailable for allocation applies for old gen.
181 _old_gen_is_full = plab_refill_in_old_failed;
182 }
183 return obj_ptr;
184 } else {
185 _old_gen_is_full = previous_plab_refill_failed;
186 assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
187 // no other space to try.
188 return NULL;
189 }
190 }
191
192 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
193 if (state.is_young()) {
194 age = !m->has_displaced_mark_helper() ? m->age()
195 : m->displaced_mark_helper()->age();
196 if (age < _tenuring_threshold) {
197 return state;
198 }
199 }
200 return dest(state);
201 }
202
203 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
204 oop const old, size_t word_sz, uint age,
205 HeapWord * const obj_ptr,
206 const AllocationContext_t context) const {
207 G1PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state, context);
208 if (alloc_buf->contains(obj_ptr)) {
209 _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
210 dest_state.value() == InCSetState::Old,
211 alloc_buf->word_sz());
212 } else {
213 _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
214 dest_state.value() == InCSetState::Old);
215 }
216 }
217
218 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
219 oop const old,
220 markOop const old_mark) {
221 const size_t word_sz = old->size();
222 HeapRegion* const from_region = _g1h->heap_region_containing(old);
223 // +1 to make the -1 indexes valid...
224 const int young_index = from_region->young_index_in_cset()+1;
225 assert( (from_region->is_young() && young_index > 0) ||
226 (!from_region->is_young() && young_index == 0), "invariant" );
227 const AllocationContext_t context = from_region->allocation_context();
228
229 uint age = 0;
230 InCSetState dest_state = next_state(state, old_mark, age);
231 // The second clause is to prevent premature evacuation failure in case there
232 // is still space in survivor, but old gen is full.
233 if (_old_gen_is_full && dest_state.is_old()) {
234 return handle_evacuation_failure_par(old, old_mark);
235 }
236 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
237
238 // PLAB allocations should succeed most of the time, so we'll
239 // normally check against NULL once and that's it.
240 if (obj_ptr == NULL) {
241 bool plab_refill_failed = false;
242 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
243 if (obj_ptr == NULL) {
244 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
245 if (obj_ptr == NULL) {
246 // This will either forward-to-self, or detect that someone else has
247 // installed a forwarding pointer.
248 return handle_evacuation_failure_par(old, old_mark);
249 }
250 }
251 if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
252 // The events are checked individually as part of the actual commit
253 report_promotion_event(dest_state, old, word_sz, age, obj_ptr, context);
254 }
255 }
256
257 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
258 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
259
260 #ifndef PRODUCT
261 // Should this evacuation fail?
262 if (_g1h->evacuation_should_fail()) {
263 // Doing this after all the allocation attempts also tests the
264 // undo_allocation() method too.
265 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
266 return handle_evacuation_failure_par(old, old_mark);
267 }
268 #endif // !PRODUCT
269
270 // We're going to allocate linearly, so might as well prefetch ahead.
271 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
272
273 const oop obj = oop(obj_ptr);
274 const oop forward_ptr = old->forward_to_atomic(obj);
275 if (forward_ptr == NULL) {
276 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
277
278 if (dest_state.is_young()) {
279 if (age < markOopDesc::max_age) {
280 age++;
281 }
282 if (old_mark->has_displaced_mark_helper()) {
283 // In this case, we have to install the mark word first,
284 // otherwise obj looks to be forwarded (the old mark word,
285 // which contains the forward pointer, was copied)
286 obj->set_mark(old_mark);
287 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
288 old_mark->set_displaced_mark_helper(new_mark);
289 } else {
290 obj->set_mark(old_mark->set_age(age));
291 }
292 _age_table.add(age, word_sz);
293 } else {
294 obj->set_mark(old_mark);
295 }
296
297 if (G1StringDedup::is_enabled()) {
298 const bool is_from_young = state.is_young();
299 const bool is_to_young = dest_state.is_young();
300 assert(is_from_young == _g1h->heap_region_containing(old)->is_young(),
301 "sanity");
302 assert(is_to_young == _g1h->heap_region_containing(obj)->is_young(),
303 "sanity");
304 G1StringDedup::enqueue_from_evacuation(is_from_young,
305 is_to_young,
306 _worker_id,
307 obj);
308 }
309
310 _surviving_young_words[young_index] += word_sz;
311
312 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
313 // We keep track of the next start index in the length field of
314 // the to-space object. The actual length can be found in the
315 // length field of the from-space object.
316 arrayOop(obj)->set_length(0);
317 oop* old_p = set_partial_array_mask(old);
318 push_on_queue(old_p);
319 } else {
320 HeapRegion* const to_region = _g1h->heap_region_containing(obj_ptr);
321 _scanner.set_region(to_region);
322 obj->oop_iterate_backwards(&_scanner);
323 }
324 return obj;
325 } else {
326 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
327 return forward_ptr;
328 }
329 }
330
331 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
332 assert(worker_id < _n_workers, "out of bounds access");
333 if (_states[worker_id] == NULL) {
334 _states[worker_id] = new_par_scan_state(worker_id, _young_cset_length);
335 }
336 return _states[worker_id];
337 }
338
339 void G1ParScanThreadStateSet::add_cards_scanned(uint worker_id, size_t cards_scanned) {
340 assert(worker_id < _n_workers, "out of bounds access");
341 _cards_scanned[worker_id] += cards_scanned;
342 }
343
344 size_t G1ParScanThreadStateSet::total_cards_scanned() const {
345 assert(_flushed, "thread local state from the per thread states should have been flushed");
346 return _total_cards_scanned;
347 }
348
349 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
350 assert(_flushed, "thread local state from the per thread states should have been flushed");
351 return _surviving_young_words_total;
352 }
353
354 void G1ParScanThreadStateSet::flush() {
355 assert(!_flushed, "thread local state from the per thread states should be flushed once");
356 assert(_total_cards_scanned == 0, "should have been cleared");
357
358 for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
359 G1ParScanThreadState* pss = _states[worker_index];
360
361 if (pss == NULL) {
362 continue;
363 }
364
365 _total_cards_scanned += _cards_scanned[worker_index];
366
367 pss->flush(_surviving_young_words_total);
368 delete pss;
369 _states[worker_index] = NULL;
370 }
371 _flushed = true;
372 }
373
374 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
375 assert(_g1h->obj_in_cs(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
376
377 oop forward_ptr = old->forward_to_atomic(old);
378 if (forward_ptr == NULL) {
379 // Forward-to-self succeeded. We are the "owner" of the object.
380 HeapRegion* r = _g1h->heap_region_containing(old);
381
382 if (!r->evacuation_failed()) {
383 r->set_evacuation_failed(true);
384 _g1h->hr_printer()->evac_failure(r);
385 }
386
387 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
388
389 _scanner.set_region(r);
390 old->oop_iterate_backwards(&_scanner);
391
392 return old;
393 } else {
394 // Forward-to-self failed. Either someone else managed to allocate
395 // space for this object (old != forward_ptr) or they beat us in
396 // self-forwarding it (old == forward_ptr).
397 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
398 "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
399 "should not be in the CSet",
400 p2i(old), p2i(forward_ptr));
401 return forward_ptr;
402 }
403 }
404