1 /*
2 * Copyright (c) 2014, 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_implementation/g1/g1CollectedHeap.inline.hpp"
27 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
28 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "oops/oop.pcgc.inline.hpp"
31 #include "runtime/prefetch.inline.hpp"
32
33 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
34 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
35 #endif // _MSC_VER
36
37 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
38 : _g1h(g1h),
39 _refs(g1h->task_queue(queue_num)),
40 _dcq(&g1h->dirty_card_queue_set()),
41 _ct_bs(g1h->g1_barrier_set()),
42 _g1_rem(g1h->g1_rem_set()),
43 _hash_seed(17), _queue_num(queue_num),
44 _term_attempts(0),
45 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
46 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
47 _age_table(false), _scanner(g1h, this, rp),
48 _strong_roots_time(0), _term_time(0),
49 _alloc_buffer_waste(0), _undo_waste(0) {
50 // we allocate G1YoungSurvRateNumRegions plus one entries, since
51 // we "sacrifice" entry 0 to keep track of surviving bytes for
52 // non-young regions (where the age is -1)
53 // We also add a few elements at the beginning and at the end in
54 // an attempt to eliminate cache contention
55 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
56 uint array_length = PADDING_ELEM_NUM +
57 real_length +
58 PADDING_ELEM_NUM;
59 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
60 if (_surviving_young_words_base == NULL)
61 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
62 "Not enough space for young surv histo.");
63 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
64 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
65
66 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
67 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
68
69 _start = os::elapsedTime();
70 }
71
72 void
73 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
74 {
75 st->print_raw_cr("GC Termination Stats");
76 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
77 " ------waste (KiB)------");
78 st->print_raw_cr("thr ms ms % ms % attempts"
79 " total alloc undo");
80 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
81 " ------- ------- -------");
82 }
83
84 void
85 G1ParScanThreadState::print_termination_stats(int i,
86 outputStream* const st) const
87 {
88 const double elapsed_ms = elapsed_time() * 1000.0;
89 const double s_roots_ms = strong_roots_time() * 1000.0;
90 const double term_ms = term_time() * 1000.0;
91 st->print_cr("%3d %9.2f %9.2f %6.2f "
92 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
93 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
94 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
95 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
96 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
97 alloc_buffer_waste() * HeapWordSize / K,
98 undo_waste() * HeapWordSize / K);
99 }
100
101 #ifdef ASSERT
102 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
103 assert(ref != NULL, "invariant");
104 assert(UseCompressedOops, "sanity");
105 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref)));
106 oop p = oopDesc::load_decode_heap_oop(ref);
107 assert(_g1h->is_in_g1_reserved(p),
108 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
109 return true;
110 }
111
112 bool G1ParScanThreadState::verify_ref(oop* ref) const {
113 assert(ref != NULL, "invariant");
114 if (has_partial_array_mask(ref)) {
115 // Must be in the collection set--it's already been copied.
116 oop p = clear_partial_array_mask(ref);
117 assert(_g1h->obj_in_cs(p),
118 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
119 } else {
120 oop p = oopDesc::load_decode_heap_oop(ref);
121 assert(_g1h->is_in_g1_reserved(p),
122 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p)));
123 }
124 return true;
125 }
126
127 bool G1ParScanThreadState::verify_task(StarTask ref) const {
128 if (ref.is_narrow()) {
129 return verify_ref((narrowOop*) ref);
130 } else {
131 return verify_ref((oop*) ref);
132 }
133 }
134 #endif // ASSERT
135
136 void G1ParScanThreadState::trim_queue() {
137 assert(_evac_failure_cl != NULL, "not set");
138
139 StarTask ref;
140 do {
141 // Drain the overflow stack first, so other threads can steal.
142 while (_refs->pop_overflow(ref)) {
143 deal_with_reference(ref);
144 }
145
146 while (_refs->pop_local(ref)) {
147 deal_with_reference(ref);
148 }
149 } while (!_refs->is_empty());
150 }
151
152 void G1ParScanThreadState::steal_and_trim_queue(RefToScanQueueSet *task_queues) {
153 StarTask stolen_task;
154 while (task_queues->steal(queue_num(), hash_seed(), stolen_task)) {
155 assert(verify_task(stolen_task), "sanity");
156 deal_with_reference(stolen_task);
157
158 // We've just processed a reference and we might have made
159 // available new entries on the queues. So we have to make sure
160 // we drain the queues as necessary.
161 trim_queue();
162 }
163 }
164
165 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
166 size_t word_sz = old->size();
167 HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
168 // +1 to make the -1 indexes valid...
169 int young_index = from_region->young_index_in_cset()+1;
170 assert( (from_region->is_young() && young_index > 0) ||
171 (!from_region->is_young() && young_index == 0), "invariant" );
172 G1CollectorPolicy* g1p = _g1h->g1_policy();
173 markOop m = old->mark();
174 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
175 : m->age();
176 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
177 word_sz);
178 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz);
179 #ifndef PRODUCT
180 // Should this evacuation fail?
181 if (_g1h->evacuation_should_fail()) {
182 if (obj_ptr != NULL) {
183 undo_allocation(alloc_purpose, obj_ptr, word_sz);
184 obj_ptr = NULL;
185 }
186 }
187 #endif // !PRODUCT
188
189 if (obj_ptr == NULL) {
190 // This will either forward-to-self, or detect that someone else has
191 // installed a forwarding pointer.
192 return _g1h->handle_evacuation_failure_par(this, old);
193 }
194
195 oop obj = oop(obj_ptr);
196
197 // We're going to allocate linearly, so might as well prefetch ahead.
198 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
199
200 oop forward_ptr = old->forward_to_atomic(obj);
201 if (forward_ptr == NULL) {
202 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
203
204 // alloc_purpose is just a hint to allocate() above, recheck the type of region
205 // we actually allocated from and update alloc_purpose accordingly
206 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
207 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
208
209 if (g1p->track_object_age(alloc_purpose)) {
210 // We could simply do obj->incr_age(). However, this causes a
211 // performance issue. obj->incr_age() will first check whether
212 // the object has a displaced mark by checking its mark word;
213 // getting the mark word from the new location of the object
214 // stalls. So, given that we already have the mark word and we
215 // are about to install it anyway, it's better to increase the
216 // age on the mark word, when the object does not have a
217 // displaced mark word. We're not expecting many objects to have
218 // a displaced marked word, so that case is not optimized
219 // further (it could be...) and we simply call obj->incr_age().
220
221 if (m->has_displaced_mark_helper()) {
222 // in this case, we have to install the mark word first,
223 // otherwise obj looks to be forwarded (the old mark word,
224 // which contains the forward pointer, was copied)
225 obj->set_mark(m);
226 obj->incr_age();
227 } else {
228 m = m->incr_age();
229 obj->set_mark(m);
230 }
231 age_table()->add(obj, word_sz);
232 } else {
233 obj->set_mark(m);
234 }
235
236 if (G1StringDedup::is_enabled()) {
237 G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
238 to_region->is_young(),
239 queue_num(),
240 obj);
241 }
242
243 size_t* surv_young_words = surviving_young_words();
244 surv_young_words[young_index] += word_sz;
245
246 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
247 // We keep track of the next start index in the length field of
248 // the to-space object. The actual length can be found in the
249 // length field of the from-space object.
250 arrayOop(obj)->set_length(0);
251 oop* old_p = set_partial_array_mask(old);
252 push_on_queue(old_p);
253 } else {
254 // No point in using the slower heap_region_containing() method,
255 // given that we know obj is in the heap.
256 _scanner.set_region(_g1h->heap_region_containing_raw(obj));
257 obj->oop_iterate_backwards(&_scanner);
258 }
259 } else {
260 undo_allocation(alloc_purpose, obj_ptr, word_sz);
261 obj = forward_ptr;
262 }
263 return obj;
264 }
265
266 HeapWord* G1ParScanThreadState::allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
267 HeapWord* obj = NULL;
268 size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
269 if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
270 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
271 add_to_alloc_buffer_waste(alloc_buf->words_remaining());
272 alloc_buf->retire(false /* end_of_gc */, false /* retain */);
273
274 HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
275 if (buf == NULL) {
276 return NULL; // Let caller handle allocation failure.
277 }
278 // Otherwise.
279 alloc_buf->set_word_size(gclab_word_size);
280 alloc_buf->set_buf(buf);
281
282 obj = alloc_buf->allocate(word_sz);
283 assert(obj != NULL, "buffer was definitely big enough...");
284 } else {
285 obj = _g1h->par_allocate_during_gc(purpose, word_sz);
286 }
287 return obj;
288 }
289
290 void G1ParScanThreadState::undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
291 if (alloc_buffer(purpose)->contains(obj)) {
292 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
293 "should contain whole object");
294 alloc_buffer(purpose)->undo_allocation(obj, word_sz);
295 } else {
296 CollectedHeap::fill_with_object(obj, word_sz);
297 add_to_undo_waste(word_sz);
298 }
299 }
300
301 HeapWord* G1ParScanThreadState::allocate(GCAllocPurpose purpose, size_t word_sz) {
302 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
303 if (obj != NULL) {
304 return obj;
305 }
306 return allocate_slow(purpose, word_sz);
307 }
308
309 void G1ParScanThreadState::retire_alloc_buffers() {
310 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
311 size_t waste = _alloc_buffers[ap]->words_remaining();
312 add_to_alloc_buffer_waste(waste);
313 _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
314 true /* end_of_gc */,
315 false /* retain */);
316 }
317 }
318
319 template <class T> void G1ParScanThreadState::do_oop_evac(T* p, HeapRegion* from) {
320 assert(!oopDesc::is_null(oopDesc::load_decode_heap_oop(p)),
321 "Reference should not be NULL here as such are never pushed to the task queue.");
322 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
323
324 // Although we never intentionally push references outside of the collection
325 // set, due to (benign) races in the claim mechanism during RSet scanning more
326 // than one thread might claim the same card. So the same card may be
327 // processed multiple times. So redo this check.
328 if (_g1h->in_cset_fast_test(obj)) {
329 oop forwardee;
330 if (obj->is_forwarded()) {
331 forwardee = obj->forwardee();
332 } else {
333 forwardee = copy_to_survivor_space(obj);
334 }
335 assert(forwardee != NULL, "forwardee should not be NULL");
336 oopDesc::encode_store_heap_oop(p, forwardee);
337 }
338
339 assert(obj != NULL, "Must be");
340 update_rs(from, p, queue_num());
341 }
342
343 inline void G1ParScanThreadState::do_oop_partial_array(oop* p) {
344 assert(has_partial_array_mask(p), "invariant");
345 oop from_obj = clear_partial_array_mask(p);
346
347 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
348 assert(from_obj->is_objArray(), "must be obj array");
349 objArrayOop from_obj_array = objArrayOop(from_obj);
350 // The from-space object contains the real length.
351 int length = from_obj_array->length();
352
353 assert(from_obj->is_forwarded(), "must be forwarded");
354 oop to_obj = from_obj->forwardee();
355 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
356 objArrayOop to_obj_array = objArrayOop(to_obj);
357 // We keep track of the next start index in the length field of the
358 // to-space object.
359 int next_index = to_obj_array->length();
360 assert(0 <= next_index && next_index < length,
361 err_msg("invariant, next index: %d, length: %d", next_index, length));
362
363 int start = next_index;
364 int end = length;
365 int remainder = end - start;
366 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
367 if (remainder > 2 * ParGCArrayScanChunk) {
368 end = start + ParGCArrayScanChunk;
369 to_obj_array->set_length(end);
370 // Push the remainder before we process the range in case another
371 // worker has run out of things to do and can steal it.
372 oop* from_obj_p = set_partial_array_mask(from_obj);
373 push_on_queue(from_obj_p);
374 } else {
375 assert(length == end, "sanity");
376 // We'll process the final range for this object. Restore the length
377 // so that the heap remains parsable in case of evacuation failure.
378 to_obj_array->set_length(end);
379 }
380 _scanner.set_region(_g1h->heap_region_containing_raw(to_obj));
381 // Process indexes [start,end). It will also process the header
382 // along with the first chunk (i.e., the chunk with start == 0).
383 // Note that at this point the length field of to_obj_array is not
384 // correct given that we are using it to keep track of the next
385 // start index. oop_iterate_range() (thankfully!) ignores the length
386 // field and only relies on the start / end parameters. It does
387 // however return the size of the object which will be incorrect. So
388 // we have to ignore it even if we wanted to use it.
389 to_obj_array->oop_iterate_range(&_scanner, start, end);
390 }
391
392 template <class T> inline void G1ParScanThreadState::deal_with_reference(T* ref_to_scan) {
393 if (!has_partial_array_mask(ref_to_scan)) {
394 // Note: we can use "raw" versions of "region_containing" because
395 // "obj_to_scan" is definitely in the heap, and is not in a
396 // humongous region.
397 HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
398 do_oop_evac(ref_to_scan, r);
399 } else {
400 do_oop_partial_array((oop*)ref_to_scan);
401 }
402 }
403
404 inline void G1ParScanThreadState::deal_with_reference(StarTask ref) {
405 assert(verify_task(ref), "sanity");
406 if (ref.is_narrow()) {
407 deal_with_reference((narrowOop*)ref);
408 } else {
409 deal_with_reference((oop*)ref);
410 }
411 }