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/g1CollectedHeap.inline.hpp"
27 #include "gc/g1/g1OopClosures.inline.hpp"
28 #include "gc/g1/g1ParScanThreadState.inline.hpp"
29 #include "gc/g1/g1StringDedup.hpp"
30 #include "gc/shared/taskqueue.inline.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/prefetch.inline.hpp"
33
34 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, ReferenceProcessor* rp)
35 : _g1h(g1h),
36 _refs(g1h->task_queue(worker_id)),
37 _dcq(&g1h->dirty_card_queue_set()),
38 _ct_bs(g1h->g1_barrier_set()),
39 _g1_rem(g1h->g1_rem_set()),
40 _hash_seed(17), _worker_id(worker_id),
41 _term_attempts(0),
42 _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
43 _age_table(false), _scanner(g1h, rp),
44 _strong_roots_time(0), _term_time(0),
45 _old_gen_is_full(false)
46 {
47 _scanner.set_par_scan_thread_state(this);
48 // we allocate G1YoungSurvRateNumRegions plus one entries, since
49 // we "sacrifice" entry 0 to keep track of surviving bytes for
50 // non-young regions (where the age is -1)
51 // We also add a few elements at the beginning and at the end in
52 // an attempt to eliminate cache contention
53 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
54 uint array_length = PADDING_ELEM_NUM +
55 real_length +
56 PADDING_ELEM_NUM;
57 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
58 if (_surviving_young_words_base == NULL)
59 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
60 "Not enough space for young surv histo.");
61 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
62 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
63
64 _plab_allocator = G1PLABAllocator::create_allocator(_g1h->allocator());
65
66 _dest[InCSetState::NotInCSet] = InCSetState::NotInCSet;
67 // The dest for Young is used when the objects are aged enough to
68 // need to be moved to the next space.
69 _dest[InCSetState::Young] = InCSetState::Old;
70 _dest[InCSetState::Old] = InCSetState::Old;
71
72 _start = os::elapsedTime();
73 }
74
75 G1ParScanThreadState::~G1ParScanThreadState() {
76 _plab_allocator->retire_alloc_buffers();
77 delete _plab_allocator;
78 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
79 }
80
81 void G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) {
82 st->print_raw_cr("GC Termination Stats");
83 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
84 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo");
85 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
86 }
87
88 void G1ParScanThreadState::print_termination_stats(outputStream* const st) const {
89 const double elapsed_ms = elapsed_time() * 1000.0;
90 const double s_roots_ms = strong_roots_time() * 1000.0;
91 const double term_ms = term_time() * 1000.0;
92 size_t alloc_buffer_waste = 0;
93 size_t undo_waste = 0;
94 _plab_allocator->waste(alloc_buffer_waste, undo_waste);
95 st->print_cr("%3u %9.2f %9.2f %6.2f "
96 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
97 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
98 _worker_id, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
99 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
100 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
101 alloc_buffer_waste * HeapWordSize / K,
102 undo_waste * HeapWordSize / K);
103 }
104
105 #ifdef ASSERT
106 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
107 assert(ref != NULL, "invariant");
108 assert(UseCompressedOops, "sanity");
109 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref)));
110 oop p = oopDesc::load_decode_heap_oop(ref);
111 assert(_g1h->is_in_g1_reserved(p),
112 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
113 return true;
114 }
115
116 bool G1ParScanThreadState::verify_ref(oop* ref) const {
117 assert(ref != NULL, "invariant");
118 if (has_partial_array_mask(ref)) {
119 // Must be in the collection set--it's already been copied.
120 oop p = clear_partial_array_mask(ref);
121 assert(_g1h->obj_in_cs(p),
122 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
123 } else {
124 oop p = oopDesc::load_decode_heap_oop(ref);
125 assert(_g1h->is_in_g1_reserved(p),
126 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
127 }
128 return true;
129 }
130
131 bool G1ParScanThreadState::verify_task(StarTask ref) const {
132 if (ref.is_narrow()) {
133 return verify_ref((narrowOop*) ref);
134 } else {
135 return verify_ref((oop*) ref);
136 }
137 }
138 #endif // ASSERT
139
140 void G1ParScanThreadState::trim_queue() {
141 StarTask ref;
142 do {
143 // Drain the overflow stack first, so other threads can steal.
144 while (_refs->pop_overflow(ref)) {
145 dispatch_reference(ref);
146 }
147
148 while (_refs->pop_local(ref)) {
149 dispatch_reference(ref);
150 }
151 } while (!_refs->is_empty());
152 }
153
154 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
155 InCSetState* dest,
156 size_t word_sz,
157 AllocationContext_t const context,
158 bool previous_plab_refill_failed) {
159 assert(state.is_in_cset_or_humongous(), err_msg("Unexpected state: " CSETSTATE_FORMAT, state.value()));
160 assert(dest->is_in_cset_or_humongous(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
161
162 // Right now we only have two types of regions (young / old) so
163 // let's keep the logic here simple. We can generalize it when necessary.
164 if (dest->is_young()) {
165 bool plab_refill_in_old_failed = false;
166 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
167 word_sz,
168 context,
169 &plab_refill_in_old_failed);
170 // Make sure that we won't attempt to copy any other objects out
171 // of a survivor region (given that apparently we cannot allocate
172 // any new ones) to avoid coming into this slow path again and again.
173 // Only consider failed PLAB refill here: failed inline allocations are
174 // typically large, so not indicative of remaining space.
175 if (previous_plab_refill_failed) {
176 _tenuring_threshold = 0;
177 }
178
179 if (obj_ptr != NULL) {
180 dest->set_old();
181 } else {
182 // We just failed to allocate in old gen. The same idea as explained above
183 // for making survivor gen unavailable for allocation applies for old gen.
184 _old_gen_is_full = plab_refill_in_old_failed;
185 }
186 return obj_ptr;
187 } else {
188 _old_gen_is_full = previous_plab_refill_failed;
189 assert(dest->is_old(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
190 // no other space to try.
191 return NULL;
192 }
193 }
194
195 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
196 if (state.is_young()) {
197 age = !m->has_displaced_mark_helper() ? m->age()
198 : m->displaced_mark_helper()->age();
199 if (age < _tenuring_threshold) {
200 return state;
201 }
202 }
203 return dest(state);
204 }
205
206 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
207 oop const old,
208 markOop const old_mark) {
209 const size_t word_sz = old->size();
210 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
211 // +1 to make the -1 indexes valid...
212 const int young_index = from_region->young_index_in_cset()+1;
213 assert( (from_region->is_young() && young_index > 0) ||
214 (!from_region->is_young() && young_index == 0), "invariant" );
215 const AllocationContext_t context = from_region->allocation_context();
216
217 uint age = 0;
218 InCSetState dest_state = next_state(state, old_mark, age);
219 // The second clause is to prevent premature evacuation failure in case there
220 // is still space in survivor, but old gen is full.
221 if (_old_gen_is_full && dest_state.is_old()) {
222 return handle_evacuation_failure_par(old, old_mark);
223 }
224 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
225
226 // PLAB allocations should succeed most of the time, so we'll
227 // normally check against NULL once and that's it.
228 if (obj_ptr == NULL) {
229 bool plab_refill_failed = false;
230 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
231 if (obj_ptr == NULL) {
232 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
233 if (obj_ptr == NULL) {
234 // This will either forward-to-self, or detect that someone else has
235 // installed a forwarding pointer.
236 return handle_evacuation_failure_par(old, old_mark);
237 }
238 }
239 }
240
241 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
242 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
243
244 #ifndef PRODUCT
245 // Should this evacuation fail?
246 if (_g1h->evacuation_should_fail()) {
247 // Doing this after all the allocation attempts also tests the
248 // undo_allocation() method too.
249 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
250 return handle_evacuation_failure_par(old, old_mark);
251 }
252 #endif // !PRODUCT
253
254 // We're going to allocate linearly, so might as well prefetch ahead.
255 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
256
257 const oop obj = oop(obj_ptr);
258 const oop forward_ptr = old->forward_to_atomic(obj);
259 if (forward_ptr == NULL) {
260 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
261
262 if (dest_state.is_young()) {
263 if (age < markOopDesc::max_age) {
264 age++;
265 }
266 if (old_mark->has_displaced_mark_helper()) {
267 // In this case, we have to install the mark word first,
268 // otherwise obj looks to be forwarded (the old mark word,
269 // which contains the forward pointer, was copied)
270 obj->set_mark(old_mark);
271 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
272 old_mark->set_displaced_mark_helper(new_mark);
273 } else {
274 obj->set_mark(old_mark->set_age(age));
275 }
276 age_table()->add(age, word_sz);
277 } else {
278 obj->set_mark(old_mark);
279 }
280
281 if (G1StringDedup::is_enabled()) {
282 const bool is_from_young = state.is_young();
283 const bool is_to_young = dest_state.is_young();
284 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
285 "sanity");
286 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
287 "sanity");
288 G1StringDedup::enqueue_from_evacuation(is_from_young,
289 is_to_young,
290 _worker_id,
291 obj);
292 }
293
294 size_t* const surv_young_words = surviving_young_words();
295 surv_young_words[young_index] += word_sz;
296
297 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
298 // We keep track of the next start index in the length field of
299 // the to-space object. The actual length can be found in the
300 // length field of the from-space object.
301 arrayOop(obj)->set_length(0);
302 oop* old_p = set_partial_array_mask(old);
303 push_on_queue(old_p);
304 } else {
305 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
306 _scanner.set_region(to_region);
307 obj->oop_iterate_backwards(&_scanner);
308 }
309 return obj;
310 } else {
311 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
312 return forward_ptr;
313 }
314 }
315
316 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
317 assert(_g1h->obj_in_cs(old),
318 err_msg("Object " PTR_FORMAT " should be in the CSet", p2i(old)));
319
320 oop forward_ptr = old->forward_to_atomic(old);
321 if (forward_ptr == NULL) {
322 // Forward-to-self succeeded. We are the "owner" of the object.
323 HeapRegion* r = _g1h->heap_region_containing(old);
324
325 if (!r->evacuation_failed()) {
326 r->set_evacuation_failed(true);
327 _g1h->hr_printer()->evac_failure(r);
328 }
329
330 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
331
332 _scanner.set_region(r);
333 old->oop_iterate_backwards(&_scanner);
334
335 return old;
336 } else {
337 // Forward-to-self failed. Either someone else managed to allocate
338 // space for this object (old != forward_ptr) or they beat us in
339 // self-forwarding it (old == forward_ptr).
340 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
341 err_msg("Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
342 "should not be in the CSet",
343 p2i(old), p2i(forward_ptr)));
344 return forward_ptr;
345 }
346 }
347