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 queue_num, ReferenceProcessor* rp)
35 : _g1h(g1h),
36 _refs(g1h->task_queue(queue_num)),
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), _queue_num(queue_num),
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 _last_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
82 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
83 {
84 st->print_raw_cr("GC Termination Stats");
85 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
86 " ------waste (KiB)------");
87 st->print_raw_cr("thr ms ms % ms % attempts"
88 " total alloc undo");
89 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
90 " ------- ------- -------");
91 }
92
93 void
94 G1ParScanThreadState::print_termination_stats(int i,
95 outputStream* const st) const
96 {
97 const double elapsed_ms = elapsed_time() * 1000.0;
98 const double s_roots_ms = strong_roots_time() * 1000.0;
99 const double term_ms = term_time() * 1000.0;
100 size_t alloc_buffer_waste = 0;
101 size_t undo_waste = 0;
102 _plab_allocator->waste(alloc_buffer_waste, undo_waste);
103 st->print_cr("%3d %9.2f %9.2f %6.2f "
104 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
105 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
106 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
107 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
108 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
109 alloc_buffer_waste * HeapWordSize / K,
110 undo_waste * HeapWordSize / K);
111 }
112
113 #ifdef ASSERT
114 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
115 assert(ref != NULL, "invariant");
116 assert(UseCompressedOops, "sanity");
117 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref)));
118 oop p = oopDesc::load_decode_heap_oop(ref);
119 assert(_g1h->is_in_g1_reserved(p),
120 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
121 return true;
122 }
123
124 bool G1ParScanThreadState::verify_ref(oop* ref) const {
125 assert(ref != NULL, "invariant");
126 if (has_partial_array_mask(ref)) {
127 // Must be in the collection set--it's already been copied.
128 oop p = clear_partial_array_mask(ref);
129 assert(_g1h->obj_in_cs(p),
130 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
131 } else {
132 oop p = oopDesc::load_decode_heap_oop(ref);
133 assert(_g1h->is_in_g1_reserved(p),
134 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
135 }
136 return true;
137 }
138
139 bool G1ParScanThreadState::verify_task(StarTask ref) const {
140 if (ref.is_narrow()) {
141 return verify_ref((narrowOop*) ref);
142 } else {
143 return verify_ref((oop*) ref);
144 }
145 }
146 #endif // ASSERT
147
148 void G1ParScanThreadState::trim_queue() {
149 StarTask ref;
150 do {
151 // Drain the overflow stack first, so other threads can steal.
152 while (_refs->pop_overflow(ref)) {
153 dispatch_reference(ref);
154 }
155
156 while (_refs->pop_local(ref)) {
157 dispatch_reference(ref);
158 }
159 } while (!_refs->is_empty());
160 }
161
162 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
163 InCSetState* dest,
164 size_t word_sz,
165 AllocationContext_t const context,
166 bool previous_plab_refill_failed) {
167 assert(state.is_in_cset_or_humongous(), err_msg("Unexpected state: " CSETSTATE_FORMAT, state.value()));
168 assert(dest->is_in_cset_or_humongous(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
169
170 // Right now we only have two types of regions (young / old) so
171 // let's keep the logic here simple. We can generalize it when necessary.
172 if (dest->is_young()) {
173 bool plab_refill_in_old_failed = false;
174 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
175 word_sz,
176 context,
177 &plab_refill_in_old_failed);
178 // Make sure that we won't attempt to copy any other objects out
179 // of a survivor region (given that apparently we cannot allocate
180 // any new ones) to avoid coming into this slow path again and again.
181 // Only consider failed PLAB refill here: failed inline allocations are
182 // typically large, so not indicative of remaining space.
183 if (previous_plab_refill_failed) {
184 _tenuring_threshold = 0;
185 }
186
187 if (obj_ptr != NULL) {
188 dest->set_old();
189 } else {
190 // We just failed to allocate in old gen. The same idea as explained above
191 // for making survivor gen unavailable for allocation applies for old gen.
192 _last_gen_is_full = plab_refill_in_old_failed;
193 }
194 return obj_ptr;
195 } else {
196 _last_gen_is_full = previous_plab_refill_failed;
197 assert(dest->is_old(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
198 // no other space to try.
199 return NULL;
200 }
201 }
202
203 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
204 if (state.is_young()) {
205 age = !m->has_displaced_mark_helper() ? m->age()
206 : m->displaced_mark_helper()->age();
207 if (age < _tenuring_threshold) {
208 return state;
209 }
210 }
211 return dest(state);
212 }
213
214 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
215 oop const old,
216 markOop const old_mark) {
217 const size_t word_sz = old->size();
218 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
219 // +1 to make the -1 indexes valid...
220 const int young_index = from_region->young_index_in_cset()+1;
221 assert( (from_region->is_young() && young_index > 0) ||
222 (!from_region->is_young() && young_index == 0), "invariant" );
223 const AllocationContext_t context = from_region->allocation_context();
224
225 uint age = 0;
226 InCSetState dest_state = next_state(state, old_mark, age);
227 // The second clause is to prevent premature evacuation failure in case there
228 // is still space in survivor, but old gen is full.
229 if (_last_gen_is_full && dest_state.is_old()) {
230 return handle_evacuation_failure_par(old, old_mark);
231 }
232 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
233
234 // PLAB allocations should succeed most of the time, so we'll
235 // normally check against NULL once and that's it.
236 if (obj_ptr == NULL) {
237 bool plab_refill_failed = false;
238 obj_ptr = _plab_allocator->allocate_inline_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
239 if (obj_ptr == NULL) {
240 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
241 if (obj_ptr == NULL) {
242 // This will either forward-to-self, or detect that someone else has
243 // installed a forwarding pointer.
244 return handle_evacuation_failure_par(old, old_mark);
245 }
246 }
247 }
248
249 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
250 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
251
252 #ifndef PRODUCT
253 // Should this evacuation fail?
254 if (_g1h->evacuation_should_fail()) {
255 // Doing this after all the allocation attempts also tests the
256 // undo_allocation() method too.
257 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
258 return handle_evacuation_failure_par(old, old_mark);
259 }
260 #endif // !PRODUCT
261
262 // We're going to allocate linearly, so might as well prefetch ahead.
263 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
264
265 const oop obj = oop(obj_ptr);
266 const oop forward_ptr = old->forward_to_atomic(obj);
267 if (forward_ptr == NULL) {
268 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
269
270 if (dest_state.is_young()) {
271 if (age < markOopDesc::max_age) {
272 age++;
273 }
274 if (old_mark->has_displaced_mark_helper()) {
275 // In this case, we have to install the mark word first,
276 // otherwise obj looks to be forwarded (the old mark word,
277 // which contains the forward pointer, was copied)
278 obj->set_mark(old_mark);
279 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
280 old_mark->set_displaced_mark_helper(new_mark);
281 } else {
282 obj->set_mark(old_mark->set_age(age));
283 }
284 age_table()->add(age, word_sz);
285 } else {
286 obj->set_mark(old_mark);
287 }
288
289 if (G1StringDedup::is_enabled()) {
290 const bool is_from_young = state.is_young();
291 const bool is_to_young = dest_state.is_young();
292 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
293 "sanity");
294 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
295 "sanity");
296 G1StringDedup::enqueue_from_evacuation(is_from_young,
297 is_to_young,
298 queue_num(),
299 obj);
300 }
301
302 size_t* const surv_young_words = surviving_young_words();
303 surv_young_words[young_index] += word_sz;
304
305 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
306 // We keep track of the next start index in the length field of
307 // the to-space object. The actual length can be found in the
308 // length field of the from-space object.
309 arrayOop(obj)->set_length(0);
310 oop* old_p = set_partial_array_mask(old);
311 push_on_queue(old_p);
312 } else {
313 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
314 _scanner.set_region(to_region);
315 obj->oop_iterate_backwards(&_scanner);
316 }
317 return obj;
318 } else {
319 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
320 return forward_ptr;
321 }
322 }
323
324 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
325 assert(_g1h->obj_in_cs(old),
326 err_msg("Object " PTR_FORMAT " should be in the CSet", p2i(old)));
327
328 oop forward_ptr = old->forward_to_atomic(old);
329 if (forward_ptr == NULL) {
330 // Forward-to-self succeeded. We are the "owner" of the object.
331 HeapRegion* r = _g1h->heap_region_containing(old);
332
333 if (!r->evacuation_failed()) {
334 r->set_evacuation_failed(true);
335 _g1h->hr_printer()->evac_failure(r);
336 }
337
338 _g1h->preserve_mark_during_evac_failure(_queue_num, old, m);
339
340 _scanner.set_region(r);
341 old->oop_iterate_backwards(&_scanner);
342
343 return old;
344 } else {
345 // Forward-to-self failed. Either someone else managed to allocate
346 // space for this object (old != forward_ptr) or they beat us in
347 // self-forwarding it (old == forward_ptr).
348 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
349 err_msg("Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
350 "should not be in the CSet",
351 p2i(old), p2i(forward_ptr)));
352 return forward_ptr;
353 }
354 }
355