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)
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 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
55 uint 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, (size_t) 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 G1ParScanThreadState::~G1ParScanThreadState() {
75 _plab_allocator->flush_and_retire_stats();
76 delete _plab_allocator;
77 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
78 }
79
80 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
81 _plab_allocator->waste(wasted, undo_wasted);
82 }
83
84 #ifdef ASSERT
85 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
86 assert(ref != NULL, "invariant");
87 assert(UseCompressedOops, "sanity");
88 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref)));
89 oop p = oopDesc::load_decode_heap_oop(ref);
90 assert(_g1h->is_in_g1_reserved(p),
91 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
92 return true;
93 }
94
95 bool G1ParScanThreadState::verify_ref(oop* ref) const {
96 assert(ref != NULL, "invariant");
97 if (has_partial_array_mask(ref)) {
98 // Must be in the collection set--it's already been copied.
99 oop p = clear_partial_array_mask(ref);
100 assert(_g1h->obj_in_cs(p),
101 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
102 } else {
103 oop p = oopDesc::load_decode_heap_oop(ref);
104 assert(_g1h->is_in_g1_reserved(p),
105 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
106 }
107 return true;
108 }
109
110 bool G1ParScanThreadState::verify_task(StarTask ref) const {
111 if (ref.is_narrow()) {
112 return verify_ref((narrowOop*) ref);
113 } else {
114 return verify_ref((oop*) ref);
115 }
116 }
117 #endif // ASSERT
118
119 void G1ParScanThreadState::trim_queue() {
120 StarTask ref;
121 do {
122 // Drain the overflow stack first, so other threads can steal.
123 while (_refs->pop_overflow(ref)) {
124 dispatch_reference(ref);
125 }
126
127 while (_refs->pop_local(ref)) {
128 dispatch_reference(ref);
129 }
130 } while (!_refs->is_empty());
131 }
132
133 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
134 InCSetState* dest,
135 size_t word_sz,
136 AllocationContext_t const context,
137 bool previous_plab_refill_failed) {
138 assert(state.is_in_cset_or_humongous(), err_msg("Unexpected state: " CSETSTATE_FORMAT, state.value()));
139 assert(dest->is_in_cset_or_humongous(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
140
141 // Right now we only have two types of regions (young / old) so
142 // let's keep the logic here simple. We can generalize it when necessary.
143 if (dest->is_young()) {
144 bool plab_refill_in_old_failed = false;
145 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
146 word_sz,
147 context,
148 &plab_refill_in_old_failed);
149 // Make sure that we won't attempt to copy any other objects out
150 // of a survivor region (given that apparently we cannot allocate
151 // any new ones) to avoid coming into this slow path again and again.
152 // Only consider failed PLAB refill here: failed inline allocations are
153 // typically large, so not indicative of remaining space.
154 if (previous_plab_refill_failed) {
155 _tenuring_threshold = 0;
156 }
157
158 if (obj_ptr != NULL) {
159 dest->set_old();
160 } else {
161 // We just failed to allocate in old gen. The same idea as explained above
162 // for making survivor gen unavailable for allocation applies for old gen.
163 _old_gen_is_full = plab_refill_in_old_failed;
164 }
165 return obj_ptr;
166 } else {
167 _old_gen_is_full = previous_plab_refill_failed;
168 assert(dest->is_old(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
169 // no other space to try.
170 return NULL;
171 }
172 }
173
174 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
175 if (state.is_young()) {
176 age = !m->has_displaced_mark_helper() ? m->age()
177 : m->displaced_mark_helper()->age();
178 if (age < _tenuring_threshold) {
179 return state;
180 }
181 }
182 return dest(state);
183 }
184
185 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
186 oop const old,
187 markOop const old_mark) {
188 const size_t word_sz = old->size();
189 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
190 // +1 to make the -1 indexes valid...
191 const int young_index = from_region->young_index_in_cset()+1;
192 assert( (from_region->is_young() && young_index > 0) ||
193 (!from_region->is_young() && young_index == 0), "invariant" );
194 const AllocationContext_t context = from_region->allocation_context();
195
196 uint age = 0;
197 InCSetState dest_state = next_state(state, old_mark, age);
198 // The second clause is to prevent premature evacuation failure in case there
199 // is still space in survivor, but old gen is full.
200 if (_old_gen_is_full && dest_state.is_old()) {
201 return handle_evacuation_failure_par(old, old_mark);
202 }
203 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
204
205 // PLAB allocations should succeed most of the time, so we'll
206 // normally check against NULL once and that's it.
207 if (obj_ptr == NULL) {
208 bool plab_refill_failed = false;
209 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
210 if (obj_ptr == NULL) {
211 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
212 if (obj_ptr == NULL) {
213 // This will either forward-to-self, or detect that someone else has
214 // installed a forwarding pointer.
215 return handle_evacuation_failure_par(old, old_mark);
216 }
217 }
218 }
219
220 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
221 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
222
223 #ifndef PRODUCT
224 // Should this evacuation fail?
225 if (_g1h->evacuation_should_fail()) {
226 // Doing this after all the allocation attempts also tests the
227 // undo_allocation() method too.
228 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
229 return handle_evacuation_failure_par(old, old_mark);
230 }
231 #endif // !PRODUCT
232
233 // We're going to allocate linearly, so might as well prefetch ahead.
234 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
235
236 const oop obj = oop(obj_ptr);
237 const oop forward_ptr = old->forward_to_atomic(obj);
238 if (forward_ptr == NULL) {
239 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
240
241 if (dest_state.is_young()) {
242 if (age < markOopDesc::max_age) {
243 age++;
244 }
245 if (old_mark->has_displaced_mark_helper()) {
246 // In this case, we have to install the mark word first,
247 // otherwise obj looks to be forwarded (the old mark word,
248 // which contains the forward pointer, was copied)
249 obj->set_mark(old_mark);
250 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
251 old_mark->set_displaced_mark_helper(new_mark);
252 } else {
253 obj->set_mark(old_mark->set_age(age));
254 }
255 age_table()->add(age, word_sz);
256 } else {
257 obj->set_mark(old_mark);
258 }
259
260 if (G1StringDedup::is_enabled()) {
261 const bool is_from_young = state.is_young();
262 const bool is_to_young = dest_state.is_young();
263 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
264 "sanity");
265 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
266 "sanity");
267 G1StringDedup::enqueue_from_evacuation(is_from_young,
268 is_to_young,
269 _worker_id,
270 obj);
271 }
272
273 _surviving_young_words[young_index] += word_sz;
274
275 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
276 // We keep track of the next start index in the length field of
277 // the to-space object. The actual length can be found in the
278 // length field of the from-space object.
279 arrayOop(obj)->set_length(0);
280 oop* old_p = set_partial_array_mask(old);
281 push_on_queue(old_p);
282 } else {
283 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
284 _scanner.set_region(to_region);
285 obj->oop_iterate_backwards(&_scanner);
286 }
287 return obj;
288 } else {
289 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
290 return forward_ptr;
291 }
292 }
293
294 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
295 assert(_g1h->obj_in_cs(old),
296 err_msg("Object " PTR_FORMAT " should be in the CSet", p2i(old)));
297
298 oop forward_ptr = old->forward_to_atomic(old);
299 if (forward_ptr == NULL) {
300 // Forward-to-self succeeded. We are the "owner" of the object.
301 HeapRegion* r = _g1h->heap_region_containing(old);
302
303 if (!r->evacuation_failed()) {
304 r->set_evacuation_failed(true);
305 _g1h->hr_printer()->evac_failure(r);
306 }
307
308 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
309
310 _scanner.set_region(r);
311 old->oop_iterate_backwards(&_scanner);
312
313 return old;
314 } else {
315 // Forward-to-self failed. Either someone else managed to allocate
316 // space for this object (old != forward_ptr) or they beat us in
317 // self-forwarding it (old == forward_ptr).
318 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
319 err_msg("Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
320 "should not be in the CSet",
321 p2i(old), p2i(forward_ptr)));
322 return forward_ptr;
323 }
324 }
325