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, ReferenceProcessor* rp)
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), _worker_id(worker_id),
42 _term_attempts(0),
43 _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
44 _age_table(false), _scanner(g1h, rp),
45 _strong_roots_time(0), _term_time(0),
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 _start = os::elapsedTime();
74 }
75
76 G1ParScanThreadState::~G1ParScanThreadState() {
77 _plab_allocator->flush_and_retire_stats();
78 delete _plab_allocator;
79 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
80 }
81
82 void G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) {
83 st->print_raw_cr("GC Termination Stats");
84 st->print_raw_cr(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
85 st->print_raw_cr("thr ms ms % ms % attempts total alloc undo");
86 st->print_raw_cr("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
87 }
88
89 void G1ParScanThreadState::print_termination_stats(outputStream* const st) const {
90 const double elapsed_ms = elapsed_time() * 1000.0;
91 const double s_roots_ms = strong_roots_time() * 1000.0;
92 const double term_ms = term_time() * 1000.0;
93 size_t alloc_buffer_waste = 0;
94 size_t undo_waste = 0;
95 _plab_allocator->waste(alloc_buffer_waste, undo_waste);
96 st->print_cr("%3u %9.2f %9.2f %6.2f "
97 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
98 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
99 _worker_id, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
100 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
101 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
102 alloc_buffer_waste * HeapWordSize / K,
103 undo_waste * HeapWordSize / K);
104 }
105
106 #ifdef ASSERT
107 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
108 assert(ref != NULL, "invariant");
109 assert(UseCompressedOops, "sanity");
110 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref)));
111 oop p = oopDesc::load_decode_heap_oop(ref);
112 assert(_g1h->is_in_g1_reserved(p),
113 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
114 return true;
115 }
116
117 bool G1ParScanThreadState::verify_ref(oop* ref) const {
118 assert(ref != NULL, "invariant");
119 if (has_partial_array_mask(ref)) {
120 // Must be in the collection set--it's already been copied.
121 oop p = clear_partial_array_mask(ref);
122 assert(_g1h->obj_in_cs(p),
123 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
124 } else {
125 oop p = oopDesc::load_decode_heap_oop(ref);
126 assert(_g1h->is_in_g1_reserved(p),
127 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
128 }
129 return true;
130 }
131
132 bool G1ParScanThreadState::verify_task(StarTask ref) const {
133 if (ref.is_narrow()) {
134 return verify_ref((narrowOop*) ref);
135 } else {
136 return verify_ref((oop*) ref);
137 }
138 }
139 #endif // ASSERT
140
141 void G1ParScanThreadState::trim_queue() {
142 StarTask ref;
143 do {
144 // Drain the overflow stack first, so other threads can steal.
145 while (_refs->pop_overflow(ref)) {
146 dispatch_reference(ref);
147 }
148
149 while (_refs->pop_local(ref)) {
150 dispatch_reference(ref);
151 }
152 } while (!_refs->is_empty());
153 }
154
155 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
156 InCSetState* dest,
157 size_t word_sz,
158 AllocationContext_t const context,
159 bool previous_plab_refill_failed) {
160 assert(state.is_in_cset_or_humongous(), err_msg("Unexpected state: " CSETSTATE_FORMAT, state.value()));
161 assert(dest->is_in_cset_or_humongous(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
162
163 // Right now we only have two types of regions (young / old) so
164 // let's keep the logic here simple. We can generalize it when necessary.
165 if (dest->is_young()) {
166 bool plab_refill_in_old_failed = false;
167 HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
168 word_sz,
169 context,
170 &plab_refill_in_old_failed);
171 // Make sure that we won't attempt to copy any other objects out
172 // of a survivor region (given that apparently we cannot allocate
173 // any new ones) to avoid coming into this slow path again and again.
174 // Only consider failed PLAB refill here: failed inline allocations are
175 // typically large, so not indicative of remaining space.
176 if (previous_plab_refill_failed) {
177 _tenuring_threshold = 0;
178 }
179
180 if (obj_ptr != NULL) {
181 dest->set_old();
182 } else {
183 // We just failed to allocate in old gen. The same idea as explained above
184 // for making survivor gen unavailable for allocation applies for old gen.
185 _old_gen_is_full = plab_refill_in_old_failed;
186 }
187 return obj_ptr;
188 } else {
189 _old_gen_is_full = previous_plab_refill_failed;
190 assert(dest->is_old(), err_msg("Unexpected dest: " CSETSTATE_FORMAT, dest->value()));
191 // no other space to try.
192 return NULL;
193 }
194 }
195
196 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
197 if (state.is_young()) {
198 age = !m->has_displaced_mark_helper() ? m->age()
199 : m->displaced_mark_helper()->age();
200 if (age < _tenuring_threshold) {
201 return state;
202 }
203 }
204 return dest(state);
205 }
206
207 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
208 oop const old,
209 markOop const old_mark) {
210 const size_t word_sz = old->size();
211 HeapRegion* const from_region = _g1h->heap_region_containing_raw(old);
212 // +1 to make the -1 indexes valid...
213 const int young_index = from_region->young_index_in_cset()+1;
214 assert( (from_region->is_young() && young_index > 0) ||
215 (!from_region->is_young() && young_index == 0), "invariant" );
216 const AllocationContext_t context = from_region->allocation_context();
217
218 uint age = 0;
219 InCSetState dest_state = next_state(state, old_mark, age);
220 // The second clause is to prevent premature evacuation failure in case there
221 // is still space in survivor, but old gen is full.
222 if (_old_gen_is_full && dest_state.is_old()) {
223 return handle_evacuation_failure_par(old, old_mark);
224 }
225 HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
226
227 // PLAB allocations should succeed most of the time, so we'll
228 // normally check against NULL once and that's it.
229 if (obj_ptr == NULL) {
230 bool plab_refill_failed = false;
231 obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
232 if (obj_ptr == NULL) {
233 obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
234 if (obj_ptr == NULL) {
235 // This will either forward-to-self, or detect that someone else has
236 // installed a forwarding pointer.
237 return handle_evacuation_failure_par(old, old_mark);
238 }
239 }
240 }
241
242 assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
243 assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
244
245 #ifndef PRODUCT
246 // Should this evacuation fail?
247 if (_g1h->evacuation_should_fail()) {
248 // Doing this after all the allocation attempts also tests the
249 // undo_allocation() method too.
250 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
251 return handle_evacuation_failure_par(old, old_mark);
252 }
253 #endif // !PRODUCT
254
255 // We're going to allocate linearly, so might as well prefetch ahead.
256 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
257
258 const oop obj = oop(obj_ptr);
259 const oop forward_ptr = old->forward_to_atomic(obj);
260 if (forward_ptr == NULL) {
261 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
262
263 if (dest_state.is_young()) {
264 if (age < markOopDesc::max_age) {
265 age++;
266 }
267 if (old_mark->has_displaced_mark_helper()) {
268 // In this case, we have to install the mark word first,
269 // otherwise obj looks to be forwarded (the old mark word,
270 // which contains the forward pointer, was copied)
271 obj->set_mark(old_mark);
272 markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
273 old_mark->set_displaced_mark_helper(new_mark);
274 } else {
275 obj->set_mark(old_mark->set_age(age));
276 }
277 age_table()->add(age, word_sz);
278 } else {
279 obj->set_mark(old_mark);
280 }
281
282 if (G1StringDedup::is_enabled()) {
283 const bool is_from_young = state.is_young();
284 const bool is_to_young = dest_state.is_young();
285 assert(is_from_young == _g1h->heap_region_containing_raw(old)->is_young(),
286 "sanity");
287 assert(is_to_young == _g1h->heap_region_containing_raw(obj)->is_young(),
288 "sanity");
289 G1StringDedup::enqueue_from_evacuation(is_from_young,
290 is_to_young,
291 _worker_id,
292 obj);
293 }
294
295 size_t* const surv_young_words = surviving_young_words();
296 surv_young_words[young_index] += word_sz;
297
298 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
299 // We keep track of the next start index in the length field of
300 // the to-space object. The actual length can be found in the
301 // length field of the from-space object.
302 arrayOop(obj)->set_length(0);
303 oop* old_p = set_partial_array_mask(old);
304 push_on_queue(old_p);
305 } else {
306 HeapRegion* const to_region = _g1h->heap_region_containing_raw(obj_ptr);
307 _scanner.set_region(to_region);
308 obj->oop_iterate_backwards(&_scanner);
309 }
310 return obj;
311 } else {
312 _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
313 return forward_ptr;
314 }
315 }
316
317 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
318 assert(_g1h->obj_in_cs(old),
319 err_msg("Object " PTR_FORMAT " should be in the CSet", p2i(old)));
320
321 oop forward_ptr = old->forward_to_atomic(old);
322 if (forward_ptr == NULL) {
323 // Forward-to-self succeeded. We are the "owner" of the object.
324 HeapRegion* r = _g1h->heap_region_containing(old);
325
326 if (!r->evacuation_failed()) {
327 r->set_evacuation_failed(true);
328 _g1h->hr_printer()->evac_failure(r);
329 }
330
331 _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
332
333 _scanner.set_region(r);
334 old->oop_iterate_backwards(&_scanner);
335
336 return old;
337 } else {
338 // Forward-to-self failed. Either someone else managed to allocate
339 // space for this object (old != forward_ptr) or they beat us in
340 // self-forwarding it (old == forward_ptr).
341 assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
342 err_msg("Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
343 "should not be in the CSet",
344 p2i(old), p2i(forward_ptr)));
345 return forward_ptr;
346 }
347 }
348