1 /*
2 * Copyright (c) 2001, 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_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gcTimer.hpp"
30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 #include "gc_implementation/shared/gcTrace.hpp"
32 #include "gc_implementation/shared/spaceDecorator.hpp"
33 #include "memory/defNewGeneration.inline.hpp"
34 #include "memory/gcLocker.inline.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/genOopClosures.inline.hpp"
37 #include "memory/genRemSet.hpp"
38 #include "memory/generationSpec.hpp"
39 #include "memory/iterator.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/space.inline.hpp"
42 #include "oops/instanceRefKlass.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "runtime/atomic.inline.hpp"
45 #include "runtime/java.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.inline.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/globalDefinitions.hpp"
50 #include "utilities/stack.inline.hpp"
51
52 //
53 // DefNewGeneration functions.
54
55 // Methods of protected closure types.
56
57 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
58 assert(g->level() == 0, "Optimized for youngest gen.");
59 }
60 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
61 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
62 }
63
64 DefNewGeneration::KeepAliveClosure::
65 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
66 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
67 _rs = (CardTableRS*)rs;
68 }
69
70 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
71 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
72
73
74 DefNewGeneration::FastKeepAliveClosure::
75 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
76 DefNewGeneration::KeepAliveClosure(cl) {
77 _boundary = g->reserved().end();
78 }
79
80 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
82
83 DefNewGeneration::EvacuateFollowersClosure::
84 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
85 ScanClosure* cur, ScanClosure* older) :
86 _gch(gch), _level(level),
87 _scan_cur_or_nonheap(cur), _scan_older(older)
88 {}
89
90 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
91 do {
92 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
93 _scan_older);
94 } while (!_gch->no_allocs_since_save_marks(_level));
95 }
96
97 DefNewGeneration::FastEvacuateFollowersClosure::
98 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
99 DefNewGeneration* gen,
100 FastScanClosure* cur, FastScanClosure* older) :
101 _gch(gch), _level(level), _gen(gen),
102 _scan_cur_or_nonheap(cur), _scan_older(older)
103 {}
104
105 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
106 do {
107 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
108 _scan_older);
109 } while (!_gch->no_allocs_since_save_marks(_level));
110 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
111 }
112
113 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
114 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
115 {
116 assert(_g->level() == 0, "Optimized for youngest generation");
117 _boundary = _g->reserved().end();
118 }
119
120 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
121 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
122
123 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
124 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
125 {
126 assert(_g->level() == 0, "Optimized for youngest generation");
127 _boundary = _g->reserved().end();
128 }
129
130 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
131 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
132
133 void KlassScanClosure::do_klass(Klass* klass) {
134 #ifndef PRODUCT
135 if (TraceScavenge) {
136 ResourceMark rm;
137 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
138 p2i(klass),
139 klass->external_name(),
140 klass->has_modified_oops() ? "true" : "false");
141 }
142 #endif
143
144 // If the klass has not been dirtied we know that there's
145 // no references into the young gen and we can skip it.
146 if (klass->has_modified_oops()) {
147 if (_accumulate_modified_oops) {
148 klass->accumulate_modified_oops();
149 }
150
151 // Clear this state since we're going to scavenge all the metadata.
152 klass->clear_modified_oops();
153
154 // Tell the closure which Klass is being scanned so that it can be dirtied
155 // if oops are left pointing into the young gen.
156 _scavenge_closure->set_scanned_klass(klass);
157
158 klass->oops_do(_scavenge_closure);
159
160 _scavenge_closure->set_scanned_klass(NULL);
161 }
162 }
163
164 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
165 _g(g)
166 {
167 assert(_g->level() == 0, "Optimized for youngest generation");
168 _boundary = _g->reserved().end();
169 }
170
171 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
172 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
173
174 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
175 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
176
177 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
178 KlassRemSet* klass_rem_set)
179 : _scavenge_closure(scavenge_closure),
180 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
181
182
183 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
184 size_t initial_size,
185 int level,
186 const char* policy)
187 : Generation(rs, initial_size, level),
188 _promo_failure_drain_in_progress(false),
189 _should_allocate_from_space(false)
190 {
191 MemRegion cmr((HeapWord*)_virtual_space.low(),
192 (HeapWord*)_virtual_space.high());
193 Universe::heap()->barrier_set()->resize_covered_region(cmr);
194
195 _eden_space = new ContiguousSpace();
196 _from_space = new ContiguousSpace();
197 _to_space = new ContiguousSpace();
198
199 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
200 vm_exit_during_initialization("Could not allocate a new gen space");
201
202 // Compute the maximum eden and survivor space sizes. These sizes
203 // are computed assuming the entire reserved space is committed.
204 // These values are exported as performance counters.
205 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
206 uintx size = _virtual_space.reserved_size();
207 _max_survivor_size = compute_survivor_size(size, alignment);
208 _max_eden_size = size - (2*_max_survivor_size);
209
210 // allocate the performance counters
211 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
212
213 // Generation counters -- generation 0, 3 subspaces
214 _gen_counters = new GenerationCounters("new", 0, 3,
215 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
216 _gc_counters = new CollectorCounters(policy, 0);
217
218 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
219 _gen_counters);
220 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
221 _gen_counters);
222 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
223 _gen_counters);
224
225 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
226 update_counters();
227 _old_gen = NULL;
228 _tenuring_threshold = MaxTenuringThreshold;
229 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
230
231 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
232 }
233
234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
235 bool clear_space,
236 bool mangle_space) {
237 uintx alignment =
238 GenCollectedHeap::heap()->collector_policy()->space_alignment();
239
240 // If the spaces are being cleared (only done at heap initialization
241 // currently), the survivor spaces need not be empty.
242 // Otherwise, no care is taken for used areas in the survivor spaces
243 // so check.
244 assert(clear_space || (to()->is_empty() && from()->is_empty()),
245 "Initialization of the survivor spaces assumes these are empty");
246
247 // Compute sizes
248 uintx size = _virtual_space.committed_size();
249 uintx survivor_size = compute_survivor_size(size, alignment);
250 uintx eden_size = size - (2*survivor_size);
251 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
252
253 if (eden_size < minimum_eden_size) {
254 // May happen due to 64Kb rounding, if so adjust eden size back up
255 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
256 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
257 uintx unaligned_survivor_size =
258 align_size_down(maximum_survivor_size, alignment);
259 survivor_size = MAX2(unaligned_survivor_size, alignment);
260 eden_size = size - (2*survivor_size);
261 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
262 assert(eden_size >= minimum_eden_size, "just checking");
263 }
264
265 char *eden_start = _virtual_space.low();
266 char *from_start = eden_start + eden_size;
267 char *to_start = from_start + survivor_size;
268 char *to_end = to_start + survivor_size;
269
270 assert(to_end == _virtual_space.high(), "just checking");
271 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
272 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
273 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
274
275 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
276 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
277 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
278
279 // A minimum eden size implies that there is a part of eden that
280 // is being used and that affects the initialization of any
281 // newly formed eden.
282 bool live_in_eden = minimum_eden_size > 0;
283
284 // If not clearing the spaces, do some checking to verify that
285 // the space are already mangled.
286 if (!clear_space) {
287 // Must check mangling before the spaces are reshaped. Otherwise,
288 // the bottom or end of one space may have moved into another
289 // a failure of the check may not correctly indicate which space
290 // is not properly mangled.
291 if (ZapUnusedHeapArea) {
292 HeapWord* limit = (HeapWord*) _virtual_space.high();
293 eden()->check_mangled_unused_area(limit);
294 from()->check_mangled_unused_area(limit);
295 to()->check_mangled_unused_area(limit);
296 }
297 }
298
299 // Reset the spaces for their new regions.
300 eden()->initialize(edenMR,
301 clear_space && !live_in_eden,
302 SpaceDecorator::Mangle);
303 // If clear_space and live_in_eden, we will not have cleared any
304 // portion of eden above its top. This can cause newly
305 // expanded space not to be mangled if using ZapUnusedHeapArea.
306 // We explicitly do such mangling here.
307 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
308 eden()->mangle_unused_area();
309 }
310 from()->initialize(fromMR, clear_space, mangle_space);
311 to()->initialize(toMR, clear_space, mangle_space);
312
313 // Set next compaction spaces.
314 eden()->set_next_compaction_space(from());
315 // The to-space is normally empty before a compaction so need
316 // not be considered. The exception is during promotion
317 // failure handling when to-space can contain live objects.
318 from()->set_next_compaction_space(NULL);
319 }
320
321 void DefNewGeneration::swap_spaces() {
322 ContiguousSpace* s = from();
323 _from_space = to();
324 _to_space = s;
325 eden()->set_next_compaction_space(from());
326 // The to-space is normally empty before a compaction so need
327 // not be considered. The exception is during promotion
328 // failure handling when to-space can contain live objects.
329 from()->set_next_compaction_space(NULL);
330
331 if (UsePerfData) {
332 CSpaceCounters* c = _from_counters;
333 _from_counters = _to_counters;
334 _to_counters = c;
335 }
336 }
337
338 bool DefNewGeneration::expand(size_t bytes) {
339 MutexLocker x(ExpandHeap_lock);
340 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
341 bool success = _virtual_space.expand_by(bytes);
342 if (success && ZapUnusedHeapArea) {
343 // Mangle newly committed space immediately because it
344 // can be done here more simply that after the new
345 // spaces have been computed.
346 HeapWord* new_high = (HeapWord*) _virtual_space.high();
347 MemRegion mangle_region(prev_high, new_high);
348 SpaceMangler::mangle_region(mangle_region);
349 }
350
351 // Do not attempt an expand-to-the reserve size. The
352 // request should properly observe the maximum size of
353 // the generation so an expand-to-reserve should be
354 // unnecessary. Also a second call to expand-to-reserve
355 // value potentially can cause an undue expansion.
356 // For example if the first expand fail for unknown reasons,
357 // but the second succeeds and expands the heap to its maximum
358 // value.
359 if (GC_locker::is_active()) {
360 if (PrintGC && Verbose) {
361 gclog_or_tty->print_cr("Garbage collection disabled, "
362 "expanded heap instead");
363 }
364 }
365
366 return success;
367 }
368
369
370 void DefNewGeneration::compute_new_size() {
371 // This is called after a gc that includes the following generation
372 // (which is required to exist.) So from-space will normally be empty.
373 // Note that we check both spaces, since if scavenge failed they revert roles.
374 // If not we bail out (otherwise we would have to relocate the objects)
375 if (!from()->is_empty() || !to()->is_empty()) {
376 return;
377 }
378
379 int next_level = level() + 1;
380 GenCollectedHeap* gch = GenCollectedHeap::heap();
381 assert(next_level < gch->n_gens(),
382 "DefNewGeneration cannot be an oldest gen");
383
384 Generation* old_gen = gch->old_gen();
385 size_t old_size = old_gen->capacity();
386 size_t new_size_before = _virtual_space.committed_size();
387 size_t min_new_size = spec()->init_size();
388 size_t max_new_size = reserved().byte_size();
389 assert(min_new_size <= new_size_before &&
390 new_size_before <= max_new_size,
391 "just checking");
392 // All space sizes must be multiples of Generation::GenGrain.
393 size_t alignment = Generation::GenGrain;
394
395 // Compute desired new generation size based on NewRatio and
396 // NewSizeThreadIncrease
397 size_t desired_new_size = old_size/NewRatio;
398 int threads_count = Threads::number_of_non_daemon_threads();
399 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
400 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
401
402 // Adjust new generation size
403 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
404 assert(desired_new_size <= max_new_size, "just checking");
405
406 bool changed = false;
407 if (desired_new_size > new_size_before) {
408 size_t change = desired_new_size - new_size_before;
409 assert(change % alignment == 0, "just checking");
410 if (expand(change)) {
411 changed = true;
412 }
413 // If the heap failed to expand to the desired size,
414 // "changed" will be false. If the expansion failed
415 // (and at this point it was expected to succeed),
416 // ignore the failure (leaving "changed" as false).
417 }
418 if (desired_new_size < new_size_before && eden()->is_empty()) {
419 // bail out of shrinking if objects in eden
420 size_t change = new_size_before - desired_new_size;
421 assert(change % alignment == 0, "just checking");
422 _virtual_space.shrink_by(change);
423 changed = true;
424 }
425 if (changed) {
426 // The spaces have already been mangled at this point but
427 // may not have been cleared (set top = bottom) and should be.
428 // Mangling was done when the heap was being expanded.
429 compute_space_boundaries(eden()->used(),
430 SpaceDecorator::Clear,
431 SpaceDecorator::DontMangle);
432 MemRegion cmr((HeapWord*)_virtual_space.low(),
433 (HeapWord*)_virtual_space.high());
434 Universe::heap()->barrier_set()->resize_covered_region(cmr);
435 if (Verbose && PrintGC) {
436 size_t new_size_after = _virtual_space.committed_size();
437 size_t eden_size_after = eden()->capacity();
438 size_t survivor_size_after = from()->capacity();
439 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
440 SIZE_FORMAT "K [eden="
441 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
442 new_size_before/K, new_size_after/K,
443 eden_size_after/K, survivor_size_after/K);
444 if (WizardMode) {
445 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
446 thread_increase_size/K, threads_count);
447 }
448 gclog_or_tty->cr();
449 }
450 }
451 }
452
453 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
454 assert(false, "NYI -- are you sure you want to call this?");
455 }
456
457
458 size_t DefNewGeneration::capacity() const {
459 return eden()->capacity()
460 + from()->capacity(); // to() is only used during scavenge
461 }
462
463
464 size_t DefNewGeneration::used() const {
465 return eden()->used()
466 + from()->used(); // to() is only used during scavenge
467 }
468
469
470 size_t DefNewGeneration::free() const {
471 return eden()->free()
472 + from()->free(); // to() is only used during scavenge
473 }
474
475 size_t DefNewGeneration::max_capacity() const {
476 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
477 const size_t reserved_bytes = reserved().byte_size();
478 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
479 }
480
481 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
482 return eden()->free();
483 }
484
485 size_t DefNewGeneration::capacity_before_gc() const {
486 return eden()->capacity();
487 }
488
489 size_t DefNewGeneration::contiguous_available() const {
490 return eden()->free();
491 }
492
493
494 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
495 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
496
497 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
498 eden()->object_iterate(blk);
499 from()->object_iterate(blk);
500 }
501
502
503 void DefNewGeneration::space_iterate(SpaceClosure* blk,
504 bool usedOnly) {
505 blk->do_space(eden());
506 blk->do_space(from());
507 blk->do_space(to());
508 }
509
510 // The last collection bailed out, we are running out of heap space,
511 // so we try to allocate the from-space, too.
512 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
513 HeapWord* result = NULL;
514 if (Verbose && PrintGCDetails) {
515 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
516 " will_fail: %s"
517 " heap_lock: %s"
518 " free: " SIZE_FORMAT,
519 size,
520 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
521 "true" : "false",
522 Heap_lock->is_locked() ? "locked" : "unlocked",
523 from()->free());
524 }
525 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
526 if (Heap_lock->owned_by_self() ||
527 (SafepointSynchronize::is_at_safepoint() &&
528 Thread::current()->is_VM_thread())) {
529 // If the Heap_lock is not locked by this thread, this will be called
530 // again later with the Heap_lock held.
531 result = from()->allocate(size);
532 } else if (PrintGC && Verbose) {
533 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
534 }
535 } else if (PrintGC && Verbose) {
536 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
537 }
538 if (PrintGC && Verbose) {
539 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
540 }
541 return result;
542 }
543
544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
545 bool is_tlab,
546 bool parallel) {
547 // We don't attempt to expand the young generation (but perhaps we should.)
548 return allocate(size, is_tlab);
549 }
550
551 void DefNewGeneration::adjust_desired_tenuring_threshold() {
552 // Set the desired survivor size to half the real survivor space
553 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
554 _tenuring_threshold =
555 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
556 }
557
558 void DefNewGeneration::collect(bool full,
559 bool clear_all_soft_refs,
560 size_t size,
561 bool is_tlab) {
562 assert(full || size > 0, "otherwise we don't want to collect");
563
564 GenCollectedHeap* gch = GenCollectedHeap::heap();
565
566 _gc_timer->register_gc_start();
567 DefNewTracer gc_tracer;
568 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
569
570 _old_gen = gch->old_gen();
571
572 // If the next generation is too full to accommodate promotion
573 // from this generation, pass on collection; let the next generation
574 // do it.
575 if (!collection_attempt_is_safe()) {
576 if (Verbose && PrintGCDetails) {
577 gclog_or_tty->print(" :: Collection attempt not safe :: ");
578 }
579 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
580 return;
581 }
582 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
583
584 init_assuming_no_promotion_failure();
585
586 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
587 // Capture heap used before collection (for printing).
588 size_t gch_prev_used = gch->used();
589
590 gch->trace_heap_before_gc(&gc_tracer);
591
592 // These can be shared for all code paths
593 IsAliveClosure is_alive(this);
594 ScanWeakRefClosure scan_weak_ref(this);
595
596 age_table()->clear();
597 to()->clear(SpaceDecorator::Mangle);
598
599 gch->rem_set()->prepare_for_younger_refs_iterate(false);
600
601 assert(gch->no_allocs_since_save_marks(0),
602 "save marks have not been newly set.");
603
604 // Not very pretty.
605 CollectorPolicy* cp = gch->collector_policy();
606
607 FastScanClosure fsc_with_no_gc_barrier(this, false);
608 FastScanClosure fsc_with_gc_barrier(this, true);
609
610 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
611 gch->rem_set()->klass_rem_set());
612 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
613 &fsc_with_no_gc_barrier,
614 false);
615
616 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
617 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
618 &fsc_with_no_gc_barrier,
619 &fsc_with_gc_barrier);
620
621 assert(gch->no_allocs_since_save_marks(0),
622 "save marks have not been newly set.");
623
624 gch->gen_process_roots(_level,
625 true, // Process younger gens, if any,
626 // as strong roots.
627 true, // activate StrongRootsScope
628 GenCollectedHeap::SO_ScavengeCodeCache,
629 GenCollectedHeap::StrongAndWeakRoots,
630 &fsc_with_no_gc_barrier,
631 &fsc_with_gc_barrier,
632 &cld_scan_closure);
633
634 // "evacuate followers".
635 evacuate_followers.do_void();
636
637 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
638 ReferenceProcessor* rp = ref_processor();
639 rp->setup_policy(clear_all_soft_refs);
640 const ReferenceProcessorStats& stats =
641 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
642 NULL, _gc_timer, gc_tracer.gc_id());
643 gc_tracer.report_gc_reference_stats(stats);
644
645 if (!_promotion_failed) {
646 // Swap the survivor spaces.
647 eden()->clear(SpaceDecorator::Mangle);
648 from()->clear(SpaceDecorator::Mangle);
649 if (ZapUnusedHeapArea) {
650 // This is now done here because of the piece-meal mangling which
651 // can check for valid mangling at intermediate points in the
652 // collection(s). When a minor collection fails to collect
653 // sufficient space resizing of the young generation can occur
654 // an redistribute the spaces in the young generation. Mangle
655 // here so that unzapped regions don't get distributed to
656 // other spaces.
657 to()->mangle_unused_area();
658 }
659 swap_spaces();
660
661 assert(to()->is_empty(), "to space should be empty now");
662
663 adjust_desired_tenuring_threshold();
664
665 // A successful scavenge should restart the GC time limit count which is
666 // for full GC's.
667 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
668 size_policy->reset_gc_overhead_limit_count();
669 assert(!gch->incremental_collection_failed(), "Should be clear");
670 } else {
671 assert(_promo_failure_scan_stack.is_empty(), "post condition");
672 _promo_failure_scan_stack.clear(true); // Clear cached segments.
673
674 remove_forwarding_pointers();
675 if (PrintGCDetails) {
676 gclog_or_tty->print(" (promotion failed) ");
677 }
678 // Add to-space to the list of space to compact
679 // when a promotion failure has occurred. In that
680 // case there can be live objects in to-space
681 // as a result of a partial evacuation of eden
682 // and from-space.
683 swap_spaces(); // For uniformity wrt ParNewGeneration.
684 from()->set_next_compaction_space(to());
685 gch->set_incremental_collection_failed();
686
687 // Inform the next generation that a promotion failure occurred.
688 _old_gen->promotion_failure_occurred();
689 gc_tracer.report_promotion_failed(_promotion_failed_info);
690
691 // Reset the PromotionFailureALot counters.
692 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
693 }
694 if (PrintGC && !PrintGCDetails) {
695 gch->print_heap_change(gch_prev_used);
696 }
697 // set new iteration safe limit for the survivor spaces
698 from()->set_concurrent_iteration_safe_limit(from()->top());
699 to()->set_concurrent_iteration_safe_limit(to()->top());
700
701 // We need to use a monotonically non-decreasing time in ms
702 // or we will see time-warp warnings and os::javaTimeMillis()
703 // does not guarantee monotonicity.
704 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
705 update_time_of_last_gc(now);
706
707 gch->trace_heap_after_gc(&gc_tracer);
708 gc_tracer.report_tenuring_threshold(tenuring_threshold());
709
710 _gc_timer->register_gc_end();
711
712 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
713 }
714
715 class RemoveForwardPointerClosure: public ObjectClosure {
716 public:
717 void do_object(oop obj) {
718 obj->init_mark();
719 }
720 };
721
722 void DefNewGeneration::init_assuming_no_promotion_failure() {
723 _promotion_failed = false;
724 _promotion_failed_info.reset();
725 from()->set_next_compaction_space(NULL);
726 }
727
728 void DefNewGeneration::remove_forwarding_pointers() {
729 RemoveForwardPointerClosure rspc;
730 eden()->object_iterate(&rspc);
731 from()->object_iterate(&rspc);
732
733 // Now restore saved marks, if any.
734 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
735 "should be the same");
736 while (!_objs_with_preserved_marks.is_empty()) {
737 oop obj = _objs_with_preserved_marks.pop();
738 markOop m = _preserved_marks_of_objs.pop();
739 obj->set_mark(m);
740 }
741 _objs_with_preserved_marks.clear(true);
742 _preserved_marks_of_objs.clear(true);
743 }
744
745 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
746 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
747 "Oversaving!");
748 _objs_with_preserved_marks.push(obj);
749 _preserved_marks_of_objs.push(m);
750 }
751
752 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
753 if (m->must_be_preserved_for_promotion_failure(obj)) {
754 preserve_mark(obj, m);
755 }
756 }
757
758 void DefNewGeneration::handle_promotion_failure(oop old) {
759 if (PrintPromotionFailure && !_promotion_failed) {
760 gclog_or_tty->print(" (promotion failure size = %d) ",
761 old->size());
762 }
763 _promotion_failed = true;
764 _promotion_failed_info.register_copy_failure(old->size());
765 preserve_mark_if_necessary(old, old->mark());
766 // forward to self
767 old->forward_to(old);
768
769 _promo_failure_scan_stack.push(old);
770
771 if (!_promo_failure_drain_in_progress) {
772 // prevent recursion in copy_to_survivor_space()
773 _promo_failure_drain_in_progress = true;
774 drain_promo_failure_scan_stack();
775 _promo_failure_drain_in_progress = false;
776 }
777 }
778
779 oop DefNewGeneration::copy_to_survivor_space(oop old) {
780 assert(is_in_reserved(old) && !old->is_forwarded(),
781 "shouldn't be scavenging this oop");
782 size_t s = old->size();
783 oop obj = NULL;
784
785 // Try allocating obj in to-space (unless too old)
786 if (old->age() < tenuring_threshold()) {
787 obj = (oop) to()->allocate_aligned(s);
788 }
789
790 // Otherwise try allocating obj tenured
791 if (obj == NULL) {
792 obj = _old_gen->promote(old, s);
793 if (obj == NULL) {
794 handle_promotion_failure(old);
795 return old;
796 }
797 } else {
798 // Prefetch beyond obj
799 const intx interval = PrefetchCopyIntervalInBytes;
800 Prefetch::write(obj, interval);
801
802 // Copy obj
803 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
804
805 // Increment age if obj still in new generation
806 obj->incr_age();
807 age_table()->add(obj, s);
808 }
809
810 // Done, insert forward pointer to obj in this header
811 old->forward_to(obj);
812
813 return obj;
814 }
815
816 void DefNewGeneration::drain_promo_failure_scan_stack() {
817 while (!_promo_failure_scan_stack.is_empty()) {
818 oop obj = _promo_failure_scan_stack.pop();
819 obj->oop_iterate(_promo_failure_scan_stack_closure);
820 }
821 }
822
823 void DefNewGeneration::save_marks() {
824 eden()->set_saved_mark();
825 to()->set_saved_mark();
826 from()->set_saved_mark();
827 }
828
829
830 void DefNewGeneration::reset_saved_marks() {
831 eden()->reset_saved_mark();
832 to()->reset_saved_mark();
833 from()->reset_saved_mark();
834 }
835
836
837 bool DefNewGeneration::no_allocs_since_save_marks() {
838 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
839 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
840 return to()->saved_mark_at_top();
841 }
842
843 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
844 \
845 void DefNewGeneration:: \
846 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
847 cl->set_generation(this); \
848 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
849 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
850 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
851 cl->reset_generation(); \
852 save_marks(); \
853 }
854
855 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
856
857 #undef DefNew_SINCE_SAVE_MARKS_DEFN
858
859 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
860 size_t max_alloc_words) {
861 if (requestor == this || _promotion_failed) return;
862 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
863
864 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
865 if (to_space->top() > to_space->bottom()) {
866 trace("to_space not empty when contribute_scratch called");
867 }
868 */
869
870 ContiguousSpace* to_space = to();
871 assert(to_space->end() >= to_space->top(), "pointers out of order");
872 size_t free_words = pointer_delta(to_space->end(), to_space->top());
873 if (free_words >= MinFreeScratchWords) {
874 ScratchBlock* sb = (ScratchBlock*)to_space->top();
875 sb->num_words = free_words;
876 sb->next = list;
877 list = sb;
878 }
879 }
880
881 void DefNewGeneration::reset_scratch() {
882 // If contributing scratch in to_space, mangle all of
883 // to_space if ZapUnusedHeapArea. This is needed because
884 // top is not maintained while using to-space as scratch.
885 if (ZapUnusedHeapArea) {
886 to()->mangle_unused_area_complete();
887 }
888 }
889
890 bool DefNewGeneration::collection_attempt_is_safe() {
891 if (!to()->is_empty()) {
892 if (Verbose && PrintGCDetails) {
893 gclog_or_tty->print(" :: to is not empty :: ");
894 }
895 return false;
896 }
897 if (_old_gen == NULL) {
898 GenCollectedHeap* gch = GenCollectedHeap::heap();
899 _old_gen = gch->old_gen();
900 }
901 return _old_gen->promotion_attempt_is_safe(used());
902 }
903
904 void DefNewGeneration::gc_epilogue(bool full) {
905 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
906
907 assert(!GC_locker::is_active(), "We should not be executing here");
908 // Check if the heap is approaching full after a collection has
909 // been done. Generally the young generation is empty at
910 // a minimum at the end of a collection. If it is not, then
911 // the heap is approaching full.
912 GenCollectedHeap* gch = GenCollectedHeap::heap();
913 if (full) {
914 DEBUG_ONLY(seen_incremental_collection_failed = false;)
915 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
916 if (Verbose && PrintGCDetails) {
917 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
918 GCCause::to_string(gch->gc_cause()));
919 }
920 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
921 set_should_allocate_from_space(); // we seem to be running out of space
922 } else {
923 if (Verbose && PrintGCDetails) {
924 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
925 GCCause::to_string(gch->gc_cause()));
926 }
927 gch->clear_incremental_collection_failed(); // We just did a full collection
928 clear_should_allocate_from_space(); // if set
929 }
930 } else {
931 #ifdef ASSERT
932 // It is possible that incremental_collection_failed() == true
933 // here, because an attempted scavenge did not succeed. The policy
934 // is normally expected to cause a full collection which should
935 // clear that condition, so we should not be here twice in a row
936 // with incremental_collection_failed() == true without having done
937 // a full collection in between.
938 if (!seen_incremental_collection_failed &&
939 gch->incremental_collection_failed()) {
940 if (Verbose && PrintGCDetails) {
941 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
942 GCCause::to_string(gch->gc_cause()));
943 }
944 seen_incremental_collection_failed = true;
945 } else if (seen_incremental_collection_failed) {
946 if (Verbose && PrintGCDetails) {
947 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
948 GCCause::to_string(gch->gc_cause()));
949 }
950 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
951 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
952 !gch->incremental_collection_failed(),
953 "Twice in a row");
954 seen_incremental_collection_failed = false;
955 }
956 #endif // ASSERT
957 }
958
959 if (ZapUnusedHeapArea) {
960 eden()->check_mangled_unused_area_complete();
961 from()->check_mangled_unused_area_complete();
962 to()->check_mangled_unused_area_complete();
963 }
964
965 if (!CleanChunkPoolAsync) {
966 Chunk::clean_chunk_pool();
967 }
968
969 // update the generation and space performance counters
970 update_counters();
971 gch->collector_policy()->counters()->update_counters();
972 }
973
974 void DefNewGeneration::record_spaces_top() {
975 assert(ZapUnusedHeapArea, "Not mangling unused space");
976 eden()->set_top_for_allocations();
977 to()->set_top_for_allocations();
978 from()->set_top_for_allocations();
979 }
980
981 void DefNewGeneration::ref_processor_init() {
982 Generation::ref_processor_init();
983 }
984
985
986 void DefNewGeneration::update_counters() {
987 if (UsePerfData) {
988 _eden_counters->update_all();
989 _from_counters->update_all();
990 _to_counters->update_all();
991 _gen_counters->update_all();
992 }
993 }
994
995 void DefNewGeneration::verify() {
996 eden()->verify();
997 from()->verify();
998 to()->verify();
999 }
1000
1001 void DefNewGeneration::print_on(outputStream* st) const {
1002 Generation::print_on(st);
1003 st->print(" eden");
1004 eden()->print_on(st);
1005 st->print(" from");
1006 from()->print_on(st);
1007 st->print(" to ");
1008 to()->print_on(st);
1009 }
1010
1011
1012 const char* DefNewGeneration::name() const {
1013 return "def new generation";
1014 }
1015
1016 // Moved from inline file as they are not called inline
1017 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1018 return eden();
1019 }
1020
1021 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1022 // This is the slow-path allocation for the DefNewGeneration.
1023 // Most allocations are fast-path in compiled code.
1024 // We try to allocate from the eden. If that works, we are happy.
1025 // Note that since DefNewGeneration supports lock-free allocation, we
1026 // have to use it here, as well.
1027 HeapWord* result = eden()->par_allocate(word_size);
1028 if (result != NULL) {
1029 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1030 _old_gen->sample_eden_chunk();
1031 }
1032 } else {
1033 // If the eden is full and the last collection bailed out, we are running
1034 // out of heap space, and we try to allocate the from-space, too.
1035 // allocate_from_space can't be inlined because that would introduce a
1036 // circular dependency at compile time.
1037 result = allocate_from_space(word_size);
1038 }
1039 return result;
1040 }
1041
1042 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1043 bool is_tlab) {
1044 HeapWord* res = eden()->par_allocate(word_size);
1045 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1046 _old_gen->sample_eden_chunk();
1047 }
1048 return res;
1049 }
1050
1051 size_t DefNewGeneration::tlab_capacity() const {
1052 return eden()->capacity();
1053 }
1054
1055 size_t DefNewGeneration::tlab_used() const {
1056 return eden()->used();
1057 }
1058
1059 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1060 return unsafe_max_alloc_nogc();
1061 }