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/g1OopClosures.inline.hpp"
29 #include "gc/g1/g1ParScanThreadState.inline.hpp"
30 #include "gc/g1/g1StringDedup.hpp"
31 #include "gc/shared/taskqueue.inline.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/prefetch.inline.hpp"
34
35 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
36 : _g1h(g1h),
37 _refs(g1h->task_queue(worker_id)),
38 _dcq(&g1h->dirty_card_queue_set()),
39 _ct_bs(g1h->g1_barrier_set()),
40 _g1_rem(g1h->g1_rem_set()),
41 _hash_seed(17),
42 _worker_id(worker_id),
43 _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
44 _age_table(false),
45 _scanner(g1h),
46 _old_gen_is_full(false)
47 {
48 _scanner.set_par_scan_thread_state(this);
49 // we allocate G1YoungSurvRateNumRegions plus one entries, since
50 // we "sacrifice" entry 0 to keep track of surviving bytes for
51 // non-young regions (where the age is -1)
52 // We also add a few elements at the beginning and at the end in
53 // an attempt to eliminate cache contention
54 size_t real_length = 1 + young_cset_length;
55 size_t array_length = PADDING_ELEM_NUM +
56 real_length +
57 PADDING_ELEM_NUM;
58 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
59 if (_surviving_young_words_base == NULL)
60 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
61 "Not enough space for young surv histo.");
62 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
63 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
64
65 _plab_allocator = G1PLABAllocator::create_allocator(_g1h->allocator());
66
67 _dest[InCSetState::NotInCSet] = InCSetState::NotInCSet;
68 // The dest for Young is used when the objects are aged enough to
69 // need to be moved to the next space.
70 _dest[InCSetState::Young] = InCSetState::Old;
71 _dest[InCSetState::Old] = InCSetState::Old;
72 }
73
74 // Pass locally gathered statistics to global state.
75 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
76 _dcq.flush();
77 // Update allocation statistics.
78 _plab_allocator->flush_and_retire_stats();
79 _g1h->g1_policy()->record_age_table(&_age_table);
80
81 uint length = _g1h->g1_policy()->young_cset_region_length();
82 for (uint region_index = 0; region_index < length; region_index++) {
83 surviving_young_words[region_index] += _surviving_young_words[region_index];
84 }
85 }
86
87 G1ParScanThreadState::~G1ParScanThreadState() {
88 delete _plab_allocator;
89 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
90 }
91
92 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
93 _plab_allocator->waste(wasted, undo_wasted);
94 }
95
96 #ifdef ASSERT
97 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
98 assert(ref != NULL, "invariant");
99 assert(UseCompressedOops, "sanity");
100 assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
101 oop p = oopDesc::load_decode_heap_oop(ref);
102 assert(_g1h->is_in_g1_reserved(p),
103 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
104 return true;
105 }
106
107 bool G1ParScanThreadState::verify_ref(oop* ref) const {
108 assert(ref != NULL, "invariant");
109 if (has_partial_array_mask(ref)) {
110 // Must be in the collection set--it's already been copied.
111 oop p = clear_partial_array_mask(ref);
112 assert(_g1h->obj_in_cs(p),
113 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
114 } else {
115 oop p = oopDesc::load_decode_heap_oop(ref);
116 assert(_g1h->is_in_g1_reserved(p),
117 "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
118 }
119 return true;
120 }
121
122 bool G1ParScanThreadState::verify_task(StarTask ref) const {
123 if (ref.is_narrow()) {
124 return verify_ref((narrowOop*) ref);
125 } else {
126 return verify_ref((oop*) ref);
127 }
128 }
129 #endif // ASSERT
130
131 void G1ParScanThreadState::trim_queue() {
132 StarTask ref;
133 do {
134 // Drain the overflow stack first, so other threads can steal.
135 while (_refs->pop_overflow(ref)) {
136 dispatch_reference(ref);
137 }
138
139 while (_refs->pop_local(ref)) {
140 dispatch_reference(ref);
141 }
142 } while (!_refs->is_empty());
143 }
144
145 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
146 InCSetState* dest,
147 size_t word_sz,
148 AllocationContext_t const context,
149 bool previous_plab_refill_failed) {
150 assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
151 assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
152
153 // Right now we only have two types of regions (young / old) so
154 // let's keep the logic here simple. We can generalize it when necessary.
155 if (dest->is_young()) {
156 bool plab_refill_in_old_failed = false;
157 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
158 word_sz,
159 context,
160 &plab_refill_in_old_failed);
161 // Make sure that we won't attempt to copy any other objects out
162 // of a survivor region (given that apparently we cannot allocate
163 // any new ones) to avoid coming into this slow path again and again.
164 // Only consider failed PLAB refill here: failed inline allocations are
165 // typically large, so not indicative of remaining space.
166 if (previous_plab_refill_failed) {
167 _tenuring_threshold = 0;
168 }
169
170 if (obj_ptr != NULL) {
171 dest->set_old();
172 } else {
173 // We just failed to allocate in old gen. The same idea as explained above
174 // for making survivor gen unavailable for allocation applies for old gen.
175 _old_gen_is_full = plab_refill_in_old_failed;
176 }
177 return obj_ptr;
178 } else {
179 _old_gen_is_full = previous_plab_refill_failed;
180 assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
181 // no other space to try.
182 return NULL;
183 }
184 }
185
186 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
187 if (state.is_young()) {
188 age = !m->has_displaced_mark_helper() ? m->age()
189 : m->displaced_mark_helper()->age();
190 if (age < _tenuring_threshold) {
191 return state;
192 }
193 }
194 return dest(state);
195 }
196
197 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
198 oop const old, size_t word_sz, uint age,
199 HeapWord * const obj_ptr,
200 const AllocationContext_t context) const {
201 G1PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state, context);
202 if (alloc_buf->contains(obj_ptr)) {
203 _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
204 dest_state.value() == InCSetState::Old,
205 alloc_buf->word_sz());
206 } else {
207 _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
208 dest_state.value() == InCSetState::Old);
209 }
210 }
211
212 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
213 oop const old,
214 markOop const old_mark) {
215 const size_t word_sz = old->size();
216 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
217 // +1 to make the -1 indexes valid...
218 const int young_index = from_region->young_index_in_cset()+1;
219 assert( (from_region->is_young() && young_index > 0) ||
220 (!from_region->is_young() && young_index == 0), "invariant" );
221 const AllocationContext_t context = from_region->allocation_context();
222
223 uint age = 0;
224 InCSetState dest_state = next_state(state, old_mark, age);
225 // The second clause is to prevent premature evacuation failure in case there
226 // is still space in survivor, but old gen is full.
227 if (_old_gen_is_full && dest_state.is_old()) {
228 return handle_evacuation_failure_par(old, old_mark);
229 }
230 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
231
232 // PLAB allocations should succeed most of the time, so we'll
233 // normally check against NULL once and that's it.
234 if (obj_ptr == NULL) {
235 bool plab_refill_failed = false;
236 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
237 if (obj_ptr == NULL) {
238 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
239 if (obj_ptr == NULL) {
240 // This will either forward-to-self, or detect that someone else has
241 // installed a forwarding pointer.
242 return handle_evacuation_failure_par(old, old_mark);
243 }
244 }
245 if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
246 // The events are checked individually as part of the actual commit
247 report_promotion_event(dest_state, old, word_sz, age, obj_ptr, context);
248 }
249 }
250
251 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
252 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
253
254 #ifndef PRODUCT
255 // Should this evacuation fail?
256 if (_g1h->evacuation_should_fail()) {
257 // Doing this after all the allocation attempts also tests the
258 // undo_allocation() method too.
259 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
260 return handle_evacuation_failure_par(old, old_mark);
261 }
262 #endif // !PRODUCT
263
264 // We're going to allocate linearly, so might as well prefetch ahead.
265 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
266
267 const oop obj = oop(obj_ptr);
268 const oop forward_ptr = old->forward_to_atomic(obj);
269 if (forward_ptr == NULL) {
270 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
271
272 if (dest_state.is_young()) {
273 if (age < markOopDesc::max_age) {
274 age++;
275 }
276 if (old_mark->has_displaced_mark_helper()) {
277 // In this case, we have to install the mark word first,
278 // otherwise obj looks to be forwarded (the old mark word,
279 // which contains the forward pointer, was copied)
280 obj->set_mark(old_mark);
281 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
282 old_mark->set_displaced_mark_helper(new_mark);
283 } else {
284 obj->set_mark(old_mark->set_age(age));
285 }
286 _age_table.add(age, word_sz);
287 } else {
288 obj->set_mark(old_mark);
289 }
290
291 if (G1StringDedup::is_enabled()) {
292 const bool is_from_young = state.is_young();
293 const bool is_to_young = dest_state.is_young();
294 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
295 "sanity");
296 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
297 "sanity");
298 G1StringDedup::enqueue_from_evacuation(is_from_young,
299 is_to_young,
300 _worker_id,
301 obj);
302 }
303
304 _surviving_young_words[young_index] += word_sz;
305
306 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
307 // We keep track of the next start index in the length field of
308 // the to-space object. The actual length can be found in the
309 // length field of the from-space object.
310 arrayOop(obj)->set_length(0);
311 oop* old_p = set_partial_array_mask(old);
312 push_on_queue(old_p);
313 } else {
314 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
315 _scanner.set_region(to_region);
316 obj->oop_iterate_backwards(&_scanner);
317 }
318 return obj;
319 } else {
320 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
321 return forward_ptr;
322 }
323 }
324
325 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
326 assert(worker_id < _n_workers, "out of bounds access");
327 return _states[worker_id];
328 }
329
330 void G1ParScanThreadStateSet::add_cards_scanned(uint worker_id, size_t cards_scanned) {
331 assert(worker_id < _n_workers, "out of bounds access");
332 _cards_scanned[worker_id] += cards_scanned;
333 }
334
335 size_t G1ParScanThreadStateSet::total_cards_scanned() const {
336 assert(_flushed, "thread local state from the per thread states should have been flushed");
337 return _total_cards_scanned;
338 }
339
340 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
341 assert(_flushed, "thread local state from the per thread states should have been flushed");
342 return _surviving_young_words_total;
343 }
344
345 void G1ParScanThreadStateSet::flush() {
346 assert(!_flushed, "thread local state from the per thread states should be flushed once");
347 assert(_total_cards_scanned == 0, "should have been cleared");
348
349 for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
350 G1ParScanThreadState* pss = _states[worker_index];
351
352 _total_cards_scanned += _cards_scanned[worker_index];
353
354 pss->flush(_surviving_young_words_total);
355 delete pss;
356 _states[worker_index] = NULL;
357 }
358 _flushed = true;
359 }
360
361 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
362 assert(_g1h->obj_in_cs(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
363
364 oop forward_ptr = old->forward_to_atomic(old);
365 if (forward_ptr == NULL) {
366 // Forward-to-self succeeded. We are the "owner" of the object.
367 HeapRegion* r = _g1h->heap_region_containing(old);
368
369 if (!r->evacuation_failed()) {
370 r->set_evacuation_failed(true);
371 _g1h->hr_printer()->evac_failure(r);
372 }
373
374 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
375
376 _scanner.set_region(r);
377 old->oop_iterate_backwards(&_scanner);
378
379 return old;
380 } else {
381 // Forward-to-self failed. Either someone else managed to allocate
382 // space for this object (old != forward_ptr) or they beat us in
383 // self-forwarding it (old == forward_ptr).
384 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
385 "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
386 "should not be in the CSet",
387 p2i(old), p2i(forward_ptr));
388 return forward_ptr;
389 }
390 }
391