1 /*
2 * Copyright (c) 2001, 2017, 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/serial/defNewGeneration.inline.hpp"
27 #include "gc/shared/ageTable.inline.hpp"
28 #include "gc/shared/cardTableRS.hpp"
29 #include "gc/shared/collectorCounters.hpp"
30 #include "gc/shared/gcHeapSummary.hpp"
31 #include "gc/shared/gcLocker.inline.hpp"
32 #include "gc/shared/gcPolicyCounters.hpp"
33 #include "gc/shared/gcTimer.hpp"
34 #include "gc/shared/gcTrace.hpp"
35 #include "gc/shared/gcTraceTime.inline.hpp"
36 #include "gc/shared/genCollectedHeap.hpp"
37 #include "gc/shared/genOopClosures.inline.hpp"
38 #include "gc/shared/generationSpec.hpp"
39 #include "gc/shared/preservedMarks.inline.hpp"
40 #include "gc/shared/referencePolicy.hpp"
41 #include "gc/shared/space.inline.hpp"
42 #include "gc/shared/spaceDecorator.hpp"
43 #include "gc/shared/strongRootsScope.hpp"
44 #include "logging/log.hpp"
45 #include "memory/iterator.hpp"
46 #include "memory/resourceArea.hpp"
47 #include "oops/instanceRefKlass.hpp"
48 #include "oops/oop.inline.hpp"
49 #include "runtime/atomic.hpp"
50 #include "runtime/java.hpp"
51 #include "runtime/prefetch.inline.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "utilities/align.hpp"
54 #include "utilities/copy.hpp"
55 #include "utilities/globalDefinitions.hpp"
56 #include "utilities/stack.inline.hpp"
57 #if INCLUDE_ALL_GCS
58 #include "gc/cms/parOopClosures.hpp"
59 #endif
60
61 //
62 // DefNewGeneration functions.
63
64 // Methods of protected closure types.
65
66 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
67 assert(_young_gen->kind() == Generation::ParNew ||
68 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
69 }
70
71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
72 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
73 }
74
75 DefNewGeneration::KeepAliveClosure::
76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
77 _rs = GenCollectedHeap::heap()->rem_set();
78 }
79
80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
82
83
84 DefNewGeneration::FastKeepAliveClosure::
85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
86 DefNewGeneration::KeepAliveClosure(cl) {
87 _boundary = g->reserved().end();
88 }
89
90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
92
93 DefNewGeneration::EvacuateFollowersClosure::
94 EvacuateFollowersClosure(GenCollectedHeap* gch,
95 ScanClosure* cur,
96 ScanClosure* older) :
97 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
98 {}
99
100 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
101 do {
102 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
103 } while (!_gch->no_allocs_since_save_marks());
104 }
105
106 DefNewGeneration::FastEvacuateFollowersClosure::
107 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
108 FastScanClosure* cur,
109 FastScanClosure* older) :
110 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
111 {
112 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
113 _young_gen = (DefNewGeneration*)_gch->young_gen();
114 }
115
116 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
117 do {
118 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
119 } while (!_gch->no_allocs_since_save_marks());
120 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
121 }
122
123 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
124 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
125 {
126 _boundary = _g->reserved().end();
127 }
128
129 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
130 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
131
132 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
133 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
134 {
135 _boundary = _g->reserved().end();
136 }
137
138 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
139 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
140
141 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
142 NOT_PRODUCT(ResourceMark rm);
143 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
144 p2i(cld),
145 cld->loader_name(),
146 cld->has_modified_oops() ? "true" : "false");
147
148 // If the cld has not been dirtied we know that there's
149 // no references into the young gen and we can skip it.
150 if (cld->has_modified_oops()) {
151 if (_accumulate_modified_oops) {
152 cld->accumulate_modified_oops();
153 }
154
155 // Tell the closure which CLD is being scanned so that it can be dirtied
156 // if oops are left pointing into the young gen.
157 _scavenge_closure->set_scanned_cld(cld);
158
159 // Clean the cld since we're going to scavenge all the metadata.
160 cld->oops_do(_scavenge_closure, false, /*clear_modified_oops*/true);
161
162 _scavenge_closure->set_scanned_cld(NULL);
163 }
164 }
165
166 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
167 _g(g)
168 {
169 _boundary = _g->reserved().end();
170 }
171
172 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
173 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
174
175 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
176 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
177
178 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
179 size_t initial_size,
180 const char* policy)
181 : Generation(rs, initial_size),
182 _preserved_marks_set(false /* in_c_heap */),
183 _promo_failure_drain_in_progress(false),
184 _should_allocate_from_space(false)
185 {
186 MemRegion cmr((HeapWord*)_virtual_space.low(),
187 (HeapWord*)_virtual_space.high());
188 GenCollectedHeap* gch = GenCollectedHeap::heap();
189
190 gch->barrier_set()->resize_covered_region(cmr);
191
192 _eden_space = new ContiguousSpace();
193 _from_space = new ContiguousSpace();
194 _to_space = new ContiguousSpace();
195
196 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
197 vm_exit_during_initialization("Could not allocate a new gen space");
198 }
199
200 // Compute the maximum eden and survivor space sizes. These sizes
201 // are computed assuming the entire reserved space is committed.
202 // These values are exported as performance counters.
203 uintx alignment = gch->collector_policy()->space_alignment();
204 uintx size = _virtual_space.reserved_size();
205 _max_survivor_size = compute_survivor_size(size, alignment);
206 _max_eden_size = size - (2*_max_survivor_size);
207
208 // allocate the performance counters
209 GenCollectorPolicy* gcp = gch->gen_policy();
210
211 // Generation counters -- generation 0, 3 subspaces
212 _gen_counters = new GenerationCounters("new", 0, 3,
213 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
214 _gc_counters = new CollectorCounters(policy, 0);
215
216 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
217 _gen_counters);
218 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
219 _gen_counters);
220 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
221 _gen_counters);
222
223 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
224 update_counters();
225 _old_gen = NULL;
226 _tenuring_threshold = MaxTenuringThreshold;
227 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
228
229 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
230 }
231
232 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
233 bool clear_space,
234 bool mangle_space) {
235 uintx alignment =
236 GenCollectedHeap::heap()->collector_policy()->space_alignment();
237
238 // If the spaces are being cleared (only done at heap initialization
239 // currently), the survivor spaces need not be empty.
240 // Otherwise, no care is taken for used areas in the survivor spaces
241 // so check.
242 assert(clear_space || (to()->is_empty() && from()->is_empty()),
243 "Initialization of the survivor spaces assumes these are empty");
244
245 // Compute sizes
246 uintx size = _virtual_space.committed_size();
247 uintx survivor_size = compute_survivor_size(size, alignment);
248 uintx eden_size = size - (2*survivor_size);
249 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
250
251 if (eden_size < minimum_eden_size) {
252 // May happen due to 64Kb rounding, if so adjust eden size back up
253 minimum_eden_size = align_up(minimum_eden_size, alignment);
254 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
255 uintx unaligned_survivor_size =
256 align_down(maximum_survivor_size, alignment);
257 survivor_size = MAX2(unaligned_survivor_size, alignment);
258 eden_size = size - (2*survivor_size);
259 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
260 assert(eden_size >= minimum_eden_size, "just checking");
261 }
262
263 char *eden_start = _virtual_space.low();
264 char *from_start = eden_start + eden_size;
265 char *to_start = from_start + survivor_size;
266 char *to_end = to_start + survivor_size;
267
268 assert(to_end == _virtual_space.high(), "just checking");
269 assert(Space::is_aligned(eden_start), "checking alignment");
270 assert(Space::is_aligned(from_start), "checking alignment");
271 assert(Space::is_aligned(to_start), "checking alignment");
272
273 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
274 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
275 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
276
277 // A minimum eden size implies that there is a part of eden that
278 // is being used and that affects the initialization of any
279 // newly formed eden.
280 bool live_in_eden = minimum_eden_size > 0;
281
282 // If not clearing the spaces, do some checking to verify that
283 // the space are already mangled.
284 if (!clear_space) {
285 // Must check mangling before the spaces are reshaped. Otherwise,
286 // the bottom or end of one space may have moved into another
287 // a failure of the check may not correctly indicate which space
288 // is not properly mangled.
289 if (ZapUnusedHeapArea) {
290 HeapWord* limit = (HeapWord*) _virtual_space.high();
291 eden()->check_mangled_unused_area(limit);
292 from()->check_mangled_unused_area(limit);
293 to()->check_mangled_unused_area(limit);
294 }
295 }
296
297 // Reset the spaces for their new regions.
298 eden()->initialize(edenMR,
299 clear_space && !live_in_eden,
300 SpaceDecorator::Mangle);
301 // If clear_space and live_in_eden, we will not have cleared any
302 // portion of eden above its top. This can cause newly
303 // expanded space not to be mangled if using ZapUnusedHeapArea.
304 // We explicitly do such mangling here.
305 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
306 eden()->mangle_unused_area();
307 }
308 from()->initialize(fromMR, clear_space, mangle_space);
309 to()->initialize(toMR, clear_space, mangle_space);
310
311 // Set next compaction spaces.
312 eden()->set_next_compaction_space(from());
313 // The to-space is normally empty before a compaction so need
314 // not be considered. The exception is during promotion
315 // failure handling when to-space can contain live objects.
316 from()->set_next_compaction_space(NULL);
317 }
318
319 void DefNewGeneration::swap_spaces() {
320 ContiguousSpace* s = from();
321 _from_space = to();
322 _to_space = s;
323 eden()->set_next_compaction_space(from());
324 // The to-space is normally empty before a compaction so need
325 // not be considered. The exception is during promotion
326 // failure handling when to-space can contain live objects.
327 from()->set_next_compaction_space(NULL);
328
329 if (UsePerfData) {
330 CSpaceCounters* c = _from_counters;
331 _from_counters = _to_counters;
332 _to_counters = c;
333 }
334 }
335
336 bool DefNewGeneration::expand(size_t bytes) {
337 MutexLocker x(ExpandHeap_lock);
338 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
339 bool success = _virtual_space.expand_by(bytes);
340 if (success && ZapUnusedHeapArea) {
341 // Mangle newly committed space immediately because it
342 // can be done here more simply that after the new
343 // spaces have been computed.
344 HeapWord* new_high = (HeapWord*) _virtual_space.high();
345 MemRegion mangle_region(prev_high, new_high);
346 SpaceMangler::mangle_region(mangle_region);
347 }
348
349 // Do not attempt an expand-to-the reserve size. The
350 // request should properly observe the maximum size of
351 // the generation so an expand-to-reserve should be
352 // unnecessary. Also a second call to expand-to-reserve
353 // value potentially can cause an undue expansion.
354 // For example if the first expand fail for unknown reasons,
355 // but the second succeeds and expands the heap to its maximum
356 // value.
357 if (GCLocker::is_active()) {
358 log_debug(gc)("Garbage collection disabled, expanded heap instead");
359 }
360
361 return success;
362 }
363
364 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
365 size_t new_size_before,
366 size_t alignment) const {
367 size_t desired_new_size = new_size_before;
368
369 if (NewSizeThreadIncrease > 0) {
370 int threads_count;
371 size_t thread_increase_size = 0;
372
373 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
374 threads_count = Threads::number_of_non_daemon_threads();
375 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
376 thread_increase_size = threads_count * NewSizeThreadIncrease;
377
378 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
379 if (new_size_candidate <= max_uintx - thread_increase_size) {
380 new_size_candidate += thread_increase_size;
381
382 // 3. Check an overflow at 'align_up'.
383 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
384 if (new_size_candidate <= aligned_max) {
385 desired_new_size = align_up(new_size_candidate, alignment);
386 }
387 }
388 }
389 }
390
391 return desired_new_size;
392 }
393
394 void DefNewGeneration::compute_new_size() {
395 // This is called after a GC that includes the old generation, so from-space
396 // will normally be empty.
397 // Note that we check both spaces, since if scavenge failed they revert roles.
398 // If not we bail out (otherwise we would have to relocate the objects).
399 if (!from()->is_empty() || !to()->is_empty()) {
400 return;
401 }
402
403 GenCollectedHeap* gch = GenCollectedHeap::heap();
404
405 size_t old_size = gch->old_gen()->capacity();
406 size_t new_size_before = _virtual_space.committed_size();
407 size_t min_new_size = initial_size();
408 size_t max_new_size = reserved().byte_size();
409 assert(min_new_size <= new_size_before &&
410 new_size_before <= max_new_size,
411 "just checking");
412 // All space sizes must be multiples of Generation::GenGrain.
413 size_t alignment = Generation::GenGrain;
414
415 int threads_count = 0;
416 size_t thread_increase_size = 0;
417
418 size_t new_size_candidate = old_size / NewRatio;
419 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
420 // and reverts to previous value if any overflow happens
421 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
422
423 // Adjust new generation size
424 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
425 assert(desired_new_size <= max_new_size, "just checking");
426
427 bool changed = false;
428 if (desired_new_size > new_size_before) {
429 size_t change = desired_new_size - new_size_before;
430 assert(change % alignment == 0, "just checking");
431 if (expand(change)) {
432 changed = true;
433 }
434 // If the heap failed to expand to the desired size,
435 // "changed" will be false. If the expansion failed
436 // (and at this point it was expected to succeed),
437 // ignore the failure (leaving "changed" as false).
438 }
439 if (desired_new_size < new_size_before && eden()->is_empty()) {
440 // bail out of shrinking if objects in eden
441 size_t change = new_size_before - desired_new_size;
442 assert(change % alignment == 0, "just checking");
443 _virtual_space.shrink_by(change);
444 changed = true;
445 }
446 if (changed) {
447 // The spaces have already been mangled at this point but
448 // may not have been cleared (set top = bottom) and should be.
449 // Mangling was done when the heap was being expanded.
450 compute_space_boundaries(eden()->used(),
451 SpaceDecorator::Clear,
452 SpaceDecorator::DontMangle);
453 MemRegion cmr((HeapWord*)_virtual_space.low(),
454 (HeapWord*)_virtual_space.high());
455 gch->barrier_set()->resize_covered_region(cmr);
456
457 log_debug(gc, ergo, heap)(
458 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
459 new_size_before/K, _virtual_space.committed_size()/K,
460 eden()->capacity()/K, from()->capacity()/K);
461 log_trace(gc, ergo, heap)(
462 " [allowed " SIZE_FORMAT "K extra for %d threads]",
463 thread_increase_size/K, threads_count);
464 }
465 }
466
467 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
468 assert(false, "NYI -- are you sure you want to call this?");
469 }
470
471
472 size_t DefNewGeneration::capacity() const {
473 return eden()->capacity()
474 + from()->capacity(); // to() is only used during scavenge
475 }
476
477
478 size_t DefNewGeneration::used() const {
479 return eden()->used()
480 + from()->used(); // to() is only used during scavenge
481 }
482
483
484 size_t DefNewGeneration::free() const {
485 return eden()->free()
486 + from()->free(); // to() is only used during scavenge
487 }
488
489 size_t DefNewGeneration::max_capacity() const {
490 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
491 const size_t reserved_bytes = reserved().byte_size();
492 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
493 }
494
495 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
496 return eden()->free();
497 }
498
499 size_t DefNewGeneration::capacity_before_gc() const {
500 return eden()->capacity();
501 }
502
503 size_t DefNewGeneration::contiguous_available() const {
504 return eden()->free();
505 }
506
507
508 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
509 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
510
511 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
512 eden()->object_iterate(blk);
513 from()->object_iterate(blk);
514 }
515
516
517 void DefNewGeneration::space_iterate(SpaceClosure* blk,
518 bool usedOnly) {
519 blk->do_space(eden());
520 blk->do_space(from());
521 blk->do_space(to());
522 }
523
524 // The last collection bailed out, we are running out of heap space,
525 // so we try to allocate the from-space, too.
526 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
527 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
528
529 // If the Heap_lock is not locked by this thread, this will be called
530 // again later with the Heap_lock held.
531 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
532
533 HeapWord* result = NULL;
534 if (do_alloc) {
535 result = from()->allocate(size);
536 }
537
538 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
539 size,
540 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
541 "true" : "false",
542 Heap_lock->is_locked() ? "locked" : "unlocked",
543 from()->free(),
544 should_try_alloc ? "" : " should_allocate_from_space: NOT",
545 do_alloc ? " Heap_lock is not owned by self" : "",
546 result == NULL ? "NULL" : "object");
547
548 return result;
549 }
550
551 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
552 bool is_tlab,
553 bool parallel) {
554 // We don't attempt to expand the young generation (but perhaps we should.)
555 return allocate(size, is_tlab);
556 }
557
558 void DefNewGeneration::adjust_desired_tenuring_threshold() {
559 // Set the desired survivor size to half the real survivor space
560 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
561 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
562
563 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
564
565 if (UsePerfData) {
566 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters();
567 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
568 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
569 }
570
571 age_table()->print_age_table(_tenuring_threshold);
572 }
573
574 void DefNewGeneration::collect(bool full,
575 bool clear_all_soft_refs,
576 size_t size,
577 bool is_tlab) {
578 assert(full || size > 0, "otherwise we don't want to collect");
579
580 GenCollectedHeap* gch = GenCollectedHeap::heap();
581
582 _gc_timer->register_gc_start();
583 DefNewTracer gc_tracer;
584 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
585
586 _old_gen = gch->old_gen();
587
588 // If the next generation is too full to accommodate promotion
589 // from this generation, pass on collection; let the next generation
590 // do it.
591 if (!collection_attempt_is_safe()) {
592 log_trace(gc)(":: Collection attempt not safe ::");
593 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
594 return;
595 }
596 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
597
598 init_assuming_no_promotion_failure();
599
600 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause());
601
602 gch->trace_heap_before_gc(&gc_tracer);
603
604 // These can be shared for all code paths
605 IsAliveClosure is_alive(this);
606 ScanWeakRefClosure scan_weak_ref(this);
607
608 age_table()->clear();
609 to()->clear(SpaceDecorator::Mangle);
610 // The preserved marks should be empty at the start of the GC.
611 _preserved_marks_set.init(1);
612
613 gch->rem_set()->prepare_for_younger_refs_iterate(false);
614
615 assert(gch->no_allocs_since_save_marks(),
616 "save marks have not been newly set.");
617
618 // Not very pretty.
619 CollectorPolicy* cp = gch->collector_policy();
620
621 FastScanClosure fsc_with_no_gc_barrier(this, false);
622 FastScanClosure fsc_with_gc_barrier(this, true);
623
624 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
625 gch->rem_set()->cld_rem_set()->accumulate_modified_oops());
626
627 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
628 FastEvacuateFollowersClosure evacuate_followers(gch,
629 &fsc_with_no_gc_barrier,
630 &fsc_with_gc_barrier);
631
632 assert(gch->no_allocs_since_save_marks(),
633 "save marks have not been newly set.");
634
635 {
636 // DefNew needs to run with n_threads == 0, to make sure the serial
637 // version of the card table scanning code is used.
638 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
639 StrongRootsScope srs(0);
640
641 gch->young_process_roots(&srs,
642 &fsc_with_no_gc_barrier,
643 &fsc_with_gc_barrier,
644 &cld_scan_closure);
645 }
646
647 // "evacuate followers".
648 evacuate_followers.do_void();
649
650 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
651 ReferenceProcessor* rp = ref_processor();
652 rp->setup_policy(clear_all_soft_refs);
653 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q());
654 const ReferenceProcessorStats& stats =
655 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
656 NULL, &pt);
657 gc_tracer.report_gc_reference_stats(stats);
658 gc_tracer.report_tenuring_threshold(tenuring_threshold());
659 pt.print_all_references();
660
661 if (!_promotion_failed) {
662 // Swap the survivor spaces.
663 eden()->clear(SpaceDecorator::Mangle);
664 from()->clear(SpaceDecorator::Mangle);
665 if (ZapUnusedHeapArea) {
666 // This is now done here because of the piece-meal mangling which
667 // can check for valid mangling at intermediate points in the
668 // collection(s). When a young collection fails to collect
669 // sufficient space resizing of the young generation can occur
670 // an redistribute the spaces in the young generation. Mangle
671 // here so that unzapped regions don't get distributed to
672 // other spaces.
673 to()->mangle_unused_area();
674 }
675 swap_spaces();
676
677 assert(to()->is_empty(), "to space should be empty now");
678
679 adjust_desired_tenuring_threshold();
680
681 // A successful scavenge should restart the GC time limit count which is
682 // for full GC's.
683 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
684 size_policy->reset_gc_overhead_limit_count();
685 assert(!gch->incremental_collection_failed(), "Should be clear");
686 } else {
687 assert(_promo_failure_scan_stack.is_empty(), "post condition");
688 _promo_failure_scan_stack.clear(true); // Clear cached segments.
689
690 remove_forwarding_pointers();
691 log_info(gc, promotion)("Promotion failed");
692 // Add to-space to the list of space to compact
693 // when a promotion failure has occurred. In that
694 // case there can be live objects in to-space
695 // as a result of a partial evacuation of eden
696 // and from-space.
697 swap_spaces(); // For uniformity wrt ParNewGeneration.
698 from()->set_next_compaction_space(to());
699 gch->set_incremental_collection_failed();
700
701 // Inform the next generation that a promotion failure occurred.
702 _old_gen->promotion_failure_occurred();
703 gc_tracer.report_promotion_failed(_promotion_failed_info);
704
705 // Reset the PromotionFailureALot counters.
706 NOT_PRODUCT(gch->reset_promotion_should_fail();)
707 }
708 // We should have processed and cleared all the preserved marks.
709 _preserved_marks_set.reclaim();
710 // set new iteration safe limit for the survivor spaces
711 from()->set_concurrent_iteration_safe_limit(from()->top());
712 to()->set_concurrent_iteration_safe_limit(to()->top());
713
714 // We need to use a monotonically non-decreasing time in ms
715 // or we will see time-warp warnings and os::javaTimeMillis()
716 // does not guarantee monotonicity.
717 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
718 update_time_of_last_gc(now);
719
720 gch->trace_heap_after_gc(&gc_tracer);
721
722 _gc_timer->register_gc_end();
723
724 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
725 }
726
727 void DefNewGeneration::init_assuming_no_promotion_failure() {
728 _promotion_failed = false;
729 _promotion_failed_info.reset();
730 from()->set_next_compaction_space(NULL);
731 }
732
733 void DefNewGeneration::remove_forwarding_pointers() {
734 RemoveForwardedPointerClosure rspc;
735 eden()->object_iterate(&rspc);
736 from()->object_iterate(&rspc);
737
738 SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers());
739 _preserved_marks_set.restore(&task_executor);
740 }
741
742 void DefNewGeneration::handle_promotion_failure(oop old) {
743 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
744
745 _promotion_failed = true;
746 _promotion_failed_info.register_copy_failure(old->size());
747 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
748 // forward to self
749 old->forward_to(old);
750
751 _promo_failure_scan_stack.push(old);
752
753 if (!_promo_failure_drain_in_progress) {
754 // prevent recursion in copy_to_survivor_space()
755 _promo_failure_drain_in_progress = true;
756 drain_promo_failure_scan_stack();
757 _promo_failure_drain_in_progress = false;
758 }
759 }
760
761 oop DefNewGeneration::copy_to_survivor_space(oop old) {
762 assert(is_in_reserved(old) && !old->is_forwarded(),
763 "shouldn't be scavenging this oop");
764 size_t s = old->size();
765 oop obj = NULL;
766
767 // Try allocating obj in to-space (unless too old)
768 if (old->age() < tenuring_threshold()) {
769 obj = (oop) to()->allocate_aligned(s);
770 }
771
772 // Otherwise try allocating obj tenured
773 if (obj == NULL) {
774 obj = _old_gen->promote(old, s);
775 if (obj == NULL) {
776 handle_promotion_failure(old);
777 return old;
778 }
779 } else {
780 // Prefetch beyond obj
781 const intx interval = PrefetchCopyIntervalInBytes;
782 Prefetch::write(obj, interval);
783
784 // Copy obj
785 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
786
787 // Increment age if obj still in new generation
788 obj->incr_age();
789 age_table()->add(obj, s);
790 }
791
792 // Done, insert forward pointer to obj in this header
793 old->forward_to(obj);
794
795 return obj;
796 }
797
798 void DefNewGeneration::drain_promo_failure_scan_stack() {
799 while (!_promo_failure_scan_stack.is_empty()) {
800 oop obj = _promo_failure_scan_stack.pop();
801 obj->oop_iterate(_promo_failure_scan_stack_closure);
802 }
803 }
804
805 void DefNewGeneration::save_marks() {
806 eden()->set_saved_mark();
807 to()->set_saved_mark();
808 from()->set_saved_mark();
809 }
810
811
812 void DefNewGeneration::reset_saved_marks() {
813 eden()->reset_saved_mark();
814 to()->reset_saved_mark();
815 from()->reset_saved_mark();
816 }
817
818
819 bool DefNewGeneration::no_allocs_since_save_marks() {
820 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
821 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
822 return to()->saved_mark_at_top();
823 }
824
825 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
826 \
827 void DefNewGeneration:: \
828 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
829 cl->set_generation(this); \
830 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
831 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
832 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
833 cl->reset_generation(); \
834 save_marks(); \
835 }
836
837 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
838
839 #undef DefNew_SINCE_SAVE_MARKS_DEFN
840
841 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
842 size_t max_alloc_words) {
843 if (requestor == this || _promotion_failed) {
844 return;
845 }
846 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
847
848 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
849 if (to_space->top() > to_space->bottom()) {
850 trace("to_space not empty when contribute_scratch called");
851 }
852 */
853
854 ContiguousSpace* to_space = to();
855 assert(to_space->end() >= to_space->top(), "pointers out of order");
856 size_t free_words = pointer_delta(to_space->end(), to_space->top());
857 if (free_words >= MinFreeScratchWords) {
858 ScratchBlock* sb = (ScratchBlock*)to_space->top();
859 sb->num_words = free_words;
860 sb->next = list;
861 list = sb;
862 }
863 }
864
865 void DefNewGeneration::reset_scratch() {
866 // If contributing scratch in to_space, mangle all of
867 // to_space if ZapUnusedHeapArea. This is needed because
868 // top is not maintained while using to-space as scratch.
869 if (ZapUnusedHeapArea) {
870 to()->mangle_unused_area_complete();
871 }
872 }
873
874 bool DefNewGeneration::collection_attempt_is_safe() {
875 if (!to()->is_empty()) {
876 log_trace(gc)(":: to is not empty ::");
877 return false;
878 }
879 if (_old_gen == NULL) {
880 GenCollectedHeap* gch = GenCollectedHeap::heap();
881 _old_gen = gch->old_gen();
882 }
883 return _old_gen->promotion_attempt_is_safe(used());
884 }
885
886 void DefNewGeneration::gc_epilogue(bool full) {
887 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
888
889 assert(!GCLocker::is_active(), "We should not be executing here");
890 // Check if the heap is approaching full after a collection has
891 // been done. Generally the young generation is empty at
892 // a minimum at the end of a collection. If it is not, then
893 // the heap is approaching full.
894 GenCollectedHeap* gch = GenCollectedHeap::heap();
895 if (full) {
896 DEBUG_ONLY(seen_incremental_collection_failed = false;)
897 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
898 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
899 GCCause::to_string(gch->gc_cause()));
900 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
901 set_should_allocate_from_space(); // we seem to be running out of space
902 } else {
903 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
904 GCCause::to_string(gch->gc_cause()));
905 gch->clear_incremental_collection_failed(); // We just did a full collection
906 clear_should_allocate_from_space(); // if set
907 }
908 } else {
909 #ifdef ASSERT
910 // It is possible that incremental_collection_failed() == true
911 // here, because an attempted scavenge did not succeed. The policy
912 // is normally expected to cause a full collection which should
913 // clear that condition, so we should not be here twice in a row
914 // with incremental_collection_failed() == true without having done
915 // a full collection in between.
916 if (!seen_incremental_collection_failed &&
917 gch->incremental_collection_failed()) {
918 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
919 GCCause::to_string(gch->gc_cause()));
920 seen_incremental_collection_failed = true;
921 } else if (seen_incremental_collection_failed) {
922 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
923 GCCause::to_string(gch->gc_cause()));
924 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
925 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
926 !gch->incremental_collection_failed(),
927 "Twice in a row");
928 seen_incremental_collection_failed = false;
929 }
930 #endif // ASSERT
931 }
932
933 if (ZapUnusedHeapArea) {
934 eden()->check_mangled_unused_area_complete();
935 from()->check_mangled_unused_area_complete();
936 to()->check_mangled_unused_area_complete();
937 }
938
939 if (!CleanChunkPoolAsync) {
940 Chunk::clean_chunk_pool();
941 }
942
943 // update the generation and space performance counters
944 update_counters();
945 gch->gen_policy()->counters()->update_counters();
946 }
947
948 void DefNewGeneration::record_spaces_top() {
949 assert(ZapUnusedHeapArea, "Not mangling unused space");
950 eden()->set_top_for_allocations();
951 to()->set_top_for_allocations();
952 from()->set_top_for_allocations();
953 }
954
955 void DefNewGeneration::ref_processor_init() {
956 Generation::ref_processor_init();
957 }
958
959
960 void DefNewGeneration::update_counters() {
961 if (UsePerfData) {
962 _eden_counters->update_all();
963 _from_counters->update_all();
964 _to_counters->update_all();
965 _gen_counters->update_all();
966 }
967 }
968
969 void DefNewGeneration::verify() {
970 eden()->verify();
971 from()->verify();
972 to()->verify();
973 }
974
975 void DefNewGeneration::print_on(outputStream* st) const {
976 Generation::print_on(st);
977 st->print(" eden");
978 eden()->print_on(st);
979 st->print(" from");
980 from()->print_on(st);
981 st->print(" to ");
982 to()->print_on(st);
983 }
984
985
986 const char* DefNewGeneration::name() const {
987 return "def new generation";
988 }
989
990 // Moved from inline file as they are not called inline
991 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
992 return eden();
993 }
994
995 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
996 // This is the slow-path allocation for the DefNewGeneration.
997 // Most allocations are fast-path in compiled code.
998 // We try to allocate from the eden. If that works, we are happy.
999 // Note that since DefNewGeneration supports lock-free allocation, we
1000 // have to use it here, as well.
1001 HeapWord* result = eden()->par_allocate(word_size);
1002 if (result != NULL) {
1003 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1004 _old_gen->sample_eden_chunk();
1005 }
1006 } else {
1007 // If the eden is full and the last collection bailed out, we are running
1008 // out of heap space, and we try to allocate the from-space, too.
1009 // allocate_from_space can't be inlined because that would introduce a
1010 // circular dependency at compile time.
1011 result = allocate_from_space(word_size);
1012 }
1013 return result;
1014 }
1015
1016 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1017 bool is_tlab) {
1018 HeapWord* res = eden()->par_allocate(word_size);
1019 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1020 _old_gen->sample_eden_chunk();
1021 }
1022 return res;
1023 }
1024
1025 size_t DefNewGeneration::tlab_capacity() const {
1026 return eden()->capacity();
1027 }
1028
1029 size_t DefNewGeneration::tlab_used() const {
1030 return eden()->used();
1031 }
1032
1033 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1034 return unsafe_max_alloc_nogc();
1035 }