Fri, 17 May 2013 11:57:05 +0200
8014277: Remove ObjectClosure as base class for BoolObjectClosure
Reviewed-by: brutisso, tschatzl
1 /*
2 * Copyright (c) 2001, 2012, 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
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7 * published by the Free Software Foundation.
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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).
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/spaceDecorator.hpp"
29 #include "memory/defNewGeneration.inline.hpp"
30 #include "memory/gcLocker.inline.hpp"
31 #include "memory/genCollectedHeap.hpp"
32 #include "memory/genOopClosures.inline.hpp"
33 #include "memory/genRemSet.hpp"
34 #include "memory/generationSpec.hpp"
35 #include "memory/iterator.hpp"
36 #include "memory/referencePolicy.hpp"
37 #include "memory/space.inline.hpp"
38 #include "oops/instanceRefKlass.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/java.hpp"
41 #include "runtime/thread.inline.hpp"
42 #include "utilities/copy.hpp"
43 #include "utilities/stack.inline.hpp"
45 //
46 // DefNewGeneration functions.
48 // Methods of protected closure types.
50 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
51 assert(g->level() == 0, "Optimized for youngest gen.");
52 }
53 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
54 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
55 }
57 DefNewGeneration::KeepAliveClosure::
58 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
59 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
60 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
61 _rs = (CardTableRS*)rs;
62 }
64 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
65 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
68 DefNewGeneration::FastKeepAliveClosure::
69 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
70 DefNewGeneration::KeepAliveClosure(cl) {
71 _boundary = g->reserved().end();
72 }
74 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
75 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
77 DefNewGeneration::EvacuateFollowersClosure::
78 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
79 ScanClosure* cur, ScanClosure* older) :
80 _gch(gch), _level(level),
81 _scan_cur_or_nonheap(cur), _scan_older(older)
82 {}
84 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
85 do {
86 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
87 _scan_older);
88 } while (!_gch->no_allocs_since_save_marks(_level));
89 }
91 DefNewGeneration::FastEvacuateFollowersClosure::
92 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
93 DefNewGeneration* gen,
94 FastScanClosure* cur, FastScanClosure* older) :
95 _gch(gch), _level(level), _gen(gen),
96 _scan_cur_or_nonheap(cur), _scan_older(older)
97 {}
99 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
100 do {
101 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
102 _scan_older);
103 } while (!_gch->no_allocs_since_save_marks(_level));
104 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
105 }
107 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
108 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
109 {
110 assert(_g->level() == 0, "Optimized for youngest generation");
111 _boundary = _g->reserved().end();
112 }
114 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
115 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
117 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
118 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
119 {
120 assert(_g->level() == 0, "Optimized for youngest generation");
121 _boundary = _g->reserved().end();
122 }
124 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
125 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
127 void KlassScanClosure::do_klass(Klass* klass) {
128 #ifndef PRODUCT
129 if (TraceScavenge) {
130 ResourceMark rm;
131 gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
132 klass,
133 klass->external_name(),
134 klass->has_modified_oops() ? "true" : "false");
135 }
136 #endif
138 // If the klass has not been dirtied we know that there's
139 // no references into the young gen and we can skip it.
140 if (klass->has_modified_oops()) {
141 if (_accumulate_modified_oops) {
142 klass->accumulate_modified_oops();
143 }
145 // Clear this state since we're going to scavenge all the metadata.
146 klass->clear_modified_oops();
148 // Tell the closure which Klass is being scanned so that it can be dirtied
149 // if oops are left pointing into the young gen.
150 _scavenge_closure->set_scanned_klass(klass);
152 klass->oops_do(_scavenge_closure);
154 _scavenge_closure->set_scanned_klass(NULL);
155 }
156 }
158 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
159 _g(g)
160 {
161 assert(_g->level() == 0, "Optimized for youngest generation");
162 _boundary = _g->reserved().end();
163 }
165 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
166 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
168 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
169 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
171 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
172 KlassRemSet* klass_rem_set)
173 : _scavenge_closure(scavenge_closure),
174 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
177 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
178 size_t initial_size,
179 int level,
180 const char* policy)
181 : Generation(rs, initial_size, level),
182 _promo_failure_drain_in_progress(false),
183 _should_allocate_from_space(false)
184 {
185 MemRegion cmr((HeapWord*)_virtual_space.low(),
186 (HeapWord*)_virtual_space.high());
187 Universe::heap()->barrier_set()->resize_covered_region(cmr);
189 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
190 _eden_space = new ConcEdenSpace(this);
191 } else {
192 _eden_space = new EdenSpace(this);
193 }
194 _from_space = new ContiguousSpace();
195 _to_space = new ContiguousSpace();
197 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
198 vm_exit_during_initialization("Could not allocate a new gen space");
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 = GenCollectedHeap::heap()->collector_policy()->min_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);
208 // allocate the performance counters
210 // Generation counters -- generation 0, 3 subspaces
211 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
212 _gc_counters = new CollectorCounters(policy, 0);
214 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
215 _gen_counters);
216 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
217 _gen_counters);
218 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
219 _gen_counters);
221 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
222 update_counters();
223 _next_gen = NULL;
224 _tenuring_threshold = MaxTenuringThreshold;
225 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
226 }
228 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
229 bool clear_space,
230 bool mangle_space) {
231 uintx alignment =
232 GenCollectedHeap::heap()->collector_policy()->min_alignment();
234 // If the spaces are being cleared (only done at heap initialization
235 // currently), the survivor spaces need not be empty.
236 // Otherwise, no care is taken for used areas in the survivor spaces
237 // so check.
238 assert(clear_space || (to()->is_empty() && from()->is_empty()),
239 "Initialization of the survivor spaces assumes these are empty");
241 // Compute sizes
242 uintx size = _virtual_space.committed_size();
243 uintx survivor_size = compute_survivor_size(size, alignment);
244 uintx eden_size = size - (2*survivor_size);
245 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
247 if (eden_size < minimum_eden_size) {
248 // May happen due to 64Kb rounding, if so adjust eden size back up
249 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
250 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
251 uintx unaligned_survivor_size =
252 align_size_down(maximum_survivor_size, alignment);
253 survivor_size = MAX2(unaligned_survivor_size, alignment);
254 eden_size = size - (2*survivor_size);
255 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
256 assert(eden_size >= minimum_eden_size, "just checking");
257 }
259 char *eden_start = _virtual_space.low();
260 char *from_start = eden_start + eden_size;
261 char *to_start = from_start + survivor_size;
262 char *to_end = to_start + survivor_size;
264 assert(to_end == _virtual_space.high(), "just checking");
265 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
266 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
267 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
269 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
270 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
271 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
273 // A minimum eden size implies that there is a part of eden that
274 // is being used and that affects the initialization of any
275 // newly formed eden.
276 bool live_in_eden = minimum_eden_size > 0;
278 // If not clearing the spaces, do some checking to verify that
279 // the space are already mangled.
280 if (!clear_space) {
281 // Must check mangling before the spaces are reshaped. Otherwise,
282 // the bottom or end of one space may have moved into another
283 // a failure of the check may not correctly indicate which space
284 // is not properly mangled.
285 if (ZapUnusedHeapArea) {
286 HeapWord* limit = (HeapWord*) _virtual_space.high();
287 eden()->check_mangled_unused_area(limit);
288 from()->check_mangled_unused_area(limit);
289 to()->check_mangled_unused_area(limit);
290 }
291 }
293 // Reset the spaces for their new regions.
294 eden()->initialize(edenMR,
295 clear_space && !live_in_eden,
296 SpaceDecorator::Mangle);
297 // If clear_space and live_in_eden, we will not have cleared any
298 // portion of eden above its top. This can cause newly
299 // expanded space not to be mangled if using ZapUnusedHeapArea.
300 // We explicitly do such mangling here.
301 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
302 eden()->mangle_unused_area();
303 }
304 from()->initialize(fromMR, clear_space, mangle_space);
305 to()->initialize(toMR, clear_space, mangle_space);
307 // Set next compaction spaces.
308 eden()->set_next_compaction_space(from());
309 // The to-space is normally empty before a compaction so need
310 // not be considered. The exception is during promotion
311 // failure handling when to-space can contain live objects.
312 from()->set_next_compaction_space(NULL);
313 }
315 void DefNewGeneration::swap_spaces() {
316 ContiguousSpace* s = from();
317 _from_space = to();
318 _to_space = s;
319 eden()->set_next_compaction_space(from());
320 // The to-space is normally empty before a compaction so need
321 // not be considered. The exception is during promotion
322 // failure handling when to-space can contain live objects.
323 from()->set_next_compaction_space(NULL);
325 if (UsePerfData) {
326 CSpaceCounters* c = _from_counters;
327 _from_counters = _to_counters;
328 _to_counters = c;
329 }
330 }
332 bool DefNewGeneration::expand(size_t bytes) {
333 MutexLocker x(ExpandHeap_lock);
334 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
335 bool success = _virtual_space.expand_by(bytes);
336 if (success && ZapUnusedHeapArea) {
337 // Mangle newly committed space immediately because it
338 // can be done here more simply that after the new
339 // spaces have been computed.
340 HeapWord* new_high = (HeapWord*) _virtual_space.high();
341 MemRegion mangle_region(prev_high, new_high);
342 SpaceMangler::mangle_region(mangle_region);
343 }
345 // Do not attempt an expand-to-the reserve size. The
346 // request should properly observe the maximum size of
347 // the generation so an expand-to-reserve should be
348 // unnecessary. Also a second call to expand-to-reserve
349 // value potentially can cause an undue expansion.
350 // For example if the first expand fail for unknown reasons,
351 // but the second succeeds and expands the heap to its maximum
352 // value.
353 if (GC_locker::is_active()) {
354 if (PrintGC && Verbose) {
355 gclog_or_tty->print_cr("Garbage collection disabled, "
356 "expanded heap instead");
357 }
358 }
360 return success;
361 }
364 void DefNewGeneration::compute_new_size() {
365 // This is called after a gc that includes the following generation
366 // (which is required to exist.) So from-space will normally be empty.
367 // Note that we check both spaces, since if scavenge failed they revert roles.
368 // If not we bail out (otherwise we would have to relocate the objects)
369 if (!from()->is_empty() || !to()->is_empty()) {
370 return;
371 }
373 int next_level = level() + 1;
374 GenCollectedHeap* gch = GenCollectedHeap::heap();
375 assert(next_level < gch->_n_gens,
376 "DefNewGeneration cannot be an oldest gen");
378 Generation* next_gen = gch->_gens[next_level];
379 size_t old_size = next_gen->capacity();
380 size_t new_size_before = _virtual_space.committed_size();
381 size_t min_new_size = spec()->init_size();
382 size_t max_new_size = reserved().byte_size();
383 assert(min_new_size <= new_size_before &&
384 new_size_before <= max_new_size,
385 "just checking");
386 // All space sizes must be multiples of Generation::GenGrain.
387 size_t alignment = Generation::GenGrain;
389 // Compute desired new generation size based on NewRatio and
390 // NewSizeThreadIncrease
391 size_t desired_new_size = old_size/NewRatio;
392 int threads_count = Threads::number_of_non_daemon_threads();
393 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
394 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
396 // Adjust new generation size
397 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
398 assert(desired_new_size <= max_new_size, "just checking");
400 bool changed = false;
401 if (desired_new_size > new_size_before) {
402 size_t change = desired_new_size - new_size_before;
403 assert(change % alignment == 0, "just checking");
404 if (expand(change)) {
405 changed = true;
406 }
407 // If the heap failed to expand to the desired size,
408 // "changed" will be false. If the expansion failed
409 // (and at this point it was expected to succeed),
410 // ignore the failure (leaving "changed" as false).
411 }
412 if (desired_new_size < new_size_before && eden()->is_empty()) {
413 // bail out of shrinking if objects in eden
414 size_t change = new_size_before - desired_new_size;
415 assert(change % alignment == 0, "just checking");
416 _virtual_space.shrink_by(change);
417 changed = true;
418 }
419 if (changed) {
420 // The spaces have already been mangled at this point but
421 // may not have been cleared (set top = bottom) and should be.
422 // Mangling was done when the heap was being expanded.
423 compute_space_boundaries(eden()->used(),
424 SpaceDecorator::Clear,
425 SpaceDecorator::DontMangle);
426 MemRegion cmr((HeapWord*)_virtual_space.low(),
427 (HeapWord*)_virtual_space.high());
428 Universe::heap()->barrier_set()->resize_covered_region(cmr);
429 if (Verbose && PrintGC) {
430 size_t new_size_after = _virtual_space.committed_size();
431 size_t eden_size_after = eden()->capacity();
432 size_t survivor_size_after = from()->capacity();
433 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
434 SIZE_FORMAT "K [eden="
435 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
436 new_size_before/K, new_size_after/K,
437 eden_size_after/K, survivor_size_after/K);
438 if (WizardMode) {
439 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
440 thread_increase_size/K, threads_count);
441 }
442 gclog_or_tty->cr();
443 }
444 }
445 }
447 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
448 // $$$ This may be wrong in case of "scavenge failure"?
449 eden()->object_iterate(cl);
450 }
452 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
453 assert(false, "NYI -- are you sure you want to call this?");
454 }
457 size_t DefNewGeneration::capacity() const {
458 return eden()->capacity()
459 + from()->capacity(); // to() is only used during scavenge
460 }
463 size_t DefNewGeneration::used() const {
464 return eden()->used()
465 + from()->used(); // to() is only used during scavenge
466 }
469 size_t DefNewGeneration::free() const {
470 return eden()->free()
471 + from()->free(); // to() is only used during scavenge
472 }
474 size_t DefNewGeneration::max_capacity() const {
475 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
476 const size_t reserved_bytes = reserved().byte_size();
477 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
478 }
480 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
481 return eden()->free();
482 }
484 size_t DefNewGeneration::capacity_before_gc() const {
485 return eden()->capacity();
486 }
488 size_t DefNewGeneration::contiguous_available() const {
489 return eden()->free();
490 }
493 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
494 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
496 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
497 eden()->object_iterate(blk);
498 from()->object_iterate(blk);
499 }
502 void DefNewGeneration::space_iterate(SpaceClosure* blk,
503 bool usedOnly) {
504 blk->do_space(eden());
505 blk->do_space(from());
506 blk->do_space(to());
507 }
509 // The last collection bailed out, we are running out of heap space,
510 // so we try to allocate the from-space, too.
511 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
512 HeapWord* result = NULL;
513 if (Verbose && PrintGCDetails) {
514 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
515 " will_fail: %s"
516 " heap_lock: %s"
517 " free: " SIZE_FORMAT,
518 size,
519 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
520 "true" : "false",
521 Heap_lock->is_locked() ? "locked" : "unlocked",
522 from()->free());
523 }
524 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
525 if (Heap_lock->owned_by_self() ||
526 (SafepointSynchronize::is_at_safepoint() &&
527 Thread::current()->is_VM_thread())) {
528 // If the Heap_lock is not locked by this thread, this will be called
529 // again later with the Heap_lock held.
530 result = from()->allocate(size);
531 } else if (PrintGC && Verbose) {
532 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
533 }
534 } else if (PrintGC && Verbose) {
535 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
536 }
537 if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
539 }
540 return result;
541 }
543 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
544 bool is_tlab,
545 bool parallel) {
546 // We don't attempt to expand the young generation (but perhaps we should.)
547 return allocate(size, is_tlab);
548 }
550 void DefNewGeneration::adjust_desired_tenuring_threshold() {
551 // Set the desired survivor size to half the real survivor space
552 _tenuring_threshold =
553 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
554 }
556 void DefNewGeneration::collect(bool full,
557 bool clear_all_soft_refs,
558 size_t size,
559 bool is_tlab) {
560 assert(full || size > 0, "otherwise we don't want to collect");
561 GenCollectedHeap* gch = GenCollectedHeap::heap();
562 _next_gen = gch->next_gen(this);
563 assert(_next_gen != NULL,
564 "This must be the youngest gen, and not the only gen");
566 // If the next generation is too full to accomodate promotion
567 // from this generation, pass on collection; let the next generation
568 // do it.
569 if (!collection_attempt_is_safe()) {
570 if (Verbose && PrintGCDetails) {
571 gclog_or_tty->print(" :: Collection attempt not safe :: ");
572 }
573 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
574 return;
575 }
576 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
578 init_assuming_no_promotion_failure();
580 TraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
581 // Capture heap used before collection (for printing).
582 size_t gch_prev_used = gch->used();
584 SpecializationStats::clear();
586 // These can be shared for all code paths
587 IsAliveClosure is_alive(this);
588 ScanWeakRefClosure scan_weak_ref(this);
590 age_table()->clear();
591 to()->clear(SpaceDecorator::Mangle);
593 gch->rem_set()->prepare_for_younger_refs_iterate(false);
595 assert(gch->no_allocs_since_save_marks(0),
596 "save marks have not been newly set.");
598 // Not very pretty.
599 CollectorPolicy* cp = gch->collector_policy();
601 FastScanClosure fsc_with_no_gc_barrier(this, false);
602 FastScanClosure fsc_with_gc_barrier(this, true);
604 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
605 gch->rem_set()->klass_rem_set());
607 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
608 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
609 &fsc_with_no_gc_barrier,
610 &fsc_with_gc_barrier);
612 assert(gch->no_allocs_since_save_marks(0),
613 "save marks have not been newly set.");
615 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
617 gch->gen_process_strong_roots(_level,
618 true, // Process younger gens, if any,
619 // as strong roots.
620 true, // activate StrongRootsScope
621 true, // is scavenging
622 SharedHeap::ScanningOption(so),
623 &fsc_with_no_gc_barrier,
624 true, // walk *all* scavengable nmethods
625 &fsc_with_gc_barrier,
626 &klass_scan_closure);
628 // "evacuate followers".
629 evacuate_followers.do_void();
631 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
632 ReferenceProcessor* rp = ref_processor();
633 rp->setup_policy(clear_all_soft_refs);
634 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
635 NULL);
636 if (!promotion_failed()) {
637 // Swap the survivor spaces.
638 eden()->clear(SpaceDecorator::Mangle);
639 from()->clear(SpaceDecorator::Mangle);
640 if (ZapUnusedHeapArea) {
641 // This is now done here because of the piece-meal mangling which
642 // can check for valid mangling at intermediate points in the
643 // collection(s). When a minor collection fails to collect
644 // sufficient space resizing of the young generation can occur
645 // an redistribute the spaces in the young generation. Mangle
646 // here so that unzapped regions don't get distributed to
647 // other spaces.
648 to()->mangle_unused_area();
649 }
650 swap_spaces();
652 assert(to()->is_empty(), "to space should be empty now");
654 adjust_desired_tenuring_threshold();
656 // A successful scavenge should restart the GC time limit count which is
657 // for full GC's.
658 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
659 size_policy->reset_gc_overhead_limit_count();
660 if (PrintGC && !PrintGCDetails) {
661 gch->print_heap_change(gch_prev_used);
662 }
663 assert(!gch->incremental_collection_failed(), "Should be clear");
664 } else {
665 assert(_promo_failure_scan_stack.is_empty(), "post condition");
666 _promo_failure_scan_stack.clear(true); // Clear cached segments.
668 remove_forwarding_pointers();
669 if (PrintGCDetails) {
670 gclog_or_tty->print(" (promotion failed) ");
671 }
672 // Add to-space to the list of space to compact
673 // when a promotion failure has occurred. In that
674 // case there can be live objects in to-space
675 // as a result of a partial evacuation of eden
676 // and from-space.
677 swap_spaces(); // For uniformity wrt ParNewGeneration.
678 from()->set_next_compaction_space(to());
679 gch->set_incremental_collection_failed();
681 // Inform the next generation that a promotion failure occurred.
682 _next_gen->promotion_failure_occurred();
684 // Reset the PromotionFailureALot counters.
685 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
686 }
687 // set new iteration safe limit for the survivor spaces
688 from()->set_concurrent_iteration_safe_limit(from()->top());
689 to()->set_concurrent_iteration_safe_limit(to()->top());
690 SpecializationStats::print();
692 // We need to use a monotonically non-deccreasing time in ms
693 // or we will see time-warp warnings and os::javaTimeMillis()
694 // does not guarantee monotonicity.
695 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
696 update_time_of_last_gc(now);
697 }
699 class RemoveForwardPointerClosure: public ObjectClosure {
700 public:
701 void do_object(oop obj) {
702 obj->init_mark();
703 }
704 };
706 void DefNewGeneration::init_assuming_no_promotion_failure() {
707 _promotion_failed = false;
708 from()->set_next_compaction_space(NULL);
709 }
711 void DefNewGeneration::remove_forwarding_pointers() {
712 RemoveForwardPointerClosure rspc;
713 eden()->object_iterate(&rspc);
714 from()->object_iterate(&rspc);
716 // Now restore saved marks, if any.
717 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
718 "should be the same");
719 while (!_objs_with_preserved_marks.is_empty()) {
720 oop obj = _objs_with_preserved_marks.pop();
721 markOop m = _preserved_marks_of_objs.pop();
722 obj->set_mark(m);
723 }
724 _objs_with_preserved_marks.clear(true);
725 _preserved_marks_of_objs.clear(true);
726 }
728 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
729 assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj),
730 "Oversaving!");
731 _objs_with_preserved_marks.push(obj);
732 _preserved_marks_of_objs.push(m);
733 }
735 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
736 if (m->must_be_preserved_for_promotion_failure(obj)) {
737 preserve_mark(obj, m);
738 }
739 }
741 void DefNewGeneration::handle_promotion_failure(oop old) {
742 if (PrintPromotionFailure && !_promotion_failed) {
743 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
744 old->size());
745 }
746 _promotion_failed = true;
747 preserve_mark_if_necessary(old, old->mark());
748 // forward to self
749 old->forward_to(old);
751 _promo_failure_scan_stack.push(old);
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 }
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;
767 // Try allocating obj in to-space (unless too old)
768 if (old->age() < tenuring_threshold()) {
769 obj = (oop) to()->allocate(s);
770 }
772 // Otherwise try allocating obj tenured
773 if (obj == NULL) {
774 obj = _next_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);
784 // Copy obj
785 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
787 // Increment age if obj still in new generation
788 obj->incr_age();
789 age_table()->add(obj, s);
790 }
792 // Done, insert forward pointer to obj in this header
793 old->forward_to(obj);
795 return obj;
796 }
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 }
805 void DefNewGeneration::save_marks() {
806 eden()->set_saved_mark();
807 to()->set_saved_mark();
808 from()->set_saved_mark();
809 }
812 void DefNewGeneration::reset_saved_marks() {
813 eden()->reset_saved_mark();
814 to()->reset_saved_mark();
815 from()->reset_saved_mark();
816 }
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 }
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 }
837 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
839 #undef DefNew_SINCE_SAVE_MARKS_DEFN
841 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
842 size_t max_alloc_words) {
843 if (requestor == this || _promotion_failed) return;
844 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
846 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
847 if (to_space->top() > to_space->bottom()) {
848 trace("to_space not empty when contribute_scratch called");
849 }
850 */
852 ContiguousSpace* to_space = to();
853 assert(to_space->end() >= to_space->top(), "pointers out of order");
854 size_t free_words = pointer_delta(to_space->end(), to_space->top());
855 if (free_words >= MinFreeScratchWords) {
856 ScratchBlock* sb = (ScratchBlock*)to_space->top();
857 sb->num_words = free_words;
858 sb->next = list;
859 list = sb;
860 }
861 }
863 void DefNewGeneration::reset_scratch() {
864 // If contributing scratch in to_space, mangle all of
865 // to_space if ZapUnusedHeapArea. This is needed because
866 // top is not maintained while using to-space as scratch.
867 if (ZapUnusedHeapArea) {
868 to()->mangle_unused_area_complete();
869 }
870 }
872 bool DefNewGeneration::collection_attempt_is_safe() {
873 if (!to()->is_empty()) {
874 if (Verbose && PrintGCDetails) {
875 gclog_or_tty->print(" :: to is not empty :: ");
876 }
877 return false;
878 }
879 if (_next_gen == NULL) {
880 GenCollectedHeap* gch = GenCollectedHeap::heap();
881 _next_gen = gch->next_gen(this);
882 assert(_next_gen != NULL,
883 "This must be the youngest gen, and not the only gen");
884 }
885 return _next_gen->promotion_attempt_is_safe(used());
886 }
888 void DefNewGeneration::gc_epilogue(bool full) {
889 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
891 assert(!GC_locker::is_active(), "We should not be executing here");
892 // Check if the heap is approaching full after a collection has
893 // been done. Generally the young generation is empty at
894 // a minimum at the end of a collection. If it is not, then
895 // the heap is approaching full.
896 GenCollectedHeap* gch = GenCollectedHeap::heap();
897 if (full) {
898 DEBUG_ONLY(seen_incremental_collection_failed = false;)
899 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
900 if (Verbose && PrintGCDetails) {
901 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
902 GCCause::to_string(gch->gc_cause()));
903 }
904 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
905 set_should_allocate_from_space(); // we seem to be running out of space
906 } else {
907 if (Verbose && PrintGCDetails) {
908 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
909 GCCause::to_string(gch->gc_cause()));
910 }
911 gch->clear_incremental_collection_failed(); // We just did a full collection
912 clear_should_allocate_from_space(); // if set
913 }
914 } else {
915 #ifdef ASSERT
916 // It is possible that incremental_collection_failed() == true
917 // here, because an attempted scavenge did not succeed. The policy
918 // is normally expected to cause a full collection which should
919 // clear that condition, so we should not be here twice in a row
920 // with incremental_collection_failed() == true without having done
921 // a full collection in between.
922 if (!seen_incremental_collection_failed &&
923 gch->incremental_collection_failed()) {
924 if (Verbose && PrintGCDetails) {
925 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
926 GCCause::to_string(gch->gc_cause()));
927 }
928 seen_incremental_collection_failed = true;
929 } else if (seen_incremental_collection_failed) {
930 if (Verbose && PrintGCDetails) {
931 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
932 GCCause::to_string(gch->gc_cause()));
933 }
934 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
935 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
936 !gch->incremental_collection_failed(),
937 "Twice in a row");
938 seen_incremental_collection_failed = false;
939 }
940 #endif // ASSERT
941 }
943 if (ZapUnusedHeapArea) {
944 eden()->check_mangled_unused_area_complete();
945 from()->check_mangled_unused_area_complete();
946 to()->check_mangled_unused_area_complete();
947 }
949 if (!CleanChunkPoolAsync) {
950 Chunk::clean_chunk_pool();
951 }
953 // update the generation and space performance counters
954 update_counters();
955 gch->collector_policy()->counters()->update_counters();
956 }
958 void DefNewGeneration::record_spaces_top() {
959 assert(ZapUnusedHeapArea, "Not mangling unused space");
960 eden()->set_top_for_allocations();
961 to()->set_top_for_allocations();
962 from()->set_top_for_allocations();
963 }
966 void DefNewGeneration::update_counters() {
967 if (UsePerfData) {
968 _eden_counters->update_all();
969 _from_counters->update_all();
970 _to_counters->update_all();
971 _gen_counters->update_all();
972 }
973 }
975 void DefNewGeneration::verify() {
976 eden()->verify();
977 from()->verify();
978 to()->verify();
979 }
981 void DefNewGeneration::print_on(outputStream* st) const {
982 Generation::print_on(st);
983 st->print(" eden");
984 eden()->print_on(st);
985 st->print(" from");
986 from()->print_on(st);
987 st->print(" to ");
988 to()->print_on(st);
989 }
992 const char* DefNewGeneration::name() const {
993 return "def new generation";
994 }
996 // Moved from inline file as they are not called inline
997 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
998 return eden();
999 }
1001 HeapWord* DefNewGeneration::allocate(size_t word_size,
1002 bool is_tlab) {
1003 // This is the slow-path allocation for the DefNewGeneration.
1004 // Most allocations are fast-path in compiled code.
1005 // We try to allocate from the eden. If that works, we are happy.
1006 // Note that since DefNewGeneration supports lock-free allocation, we
1007 // have to use it here, as well.
1008 HeapWord* result = eden()->par_allocate(word_size);
1009 if (result != NULL) {
1010 return result;
1011 }
1012 do {
1013 HeapWord* old_limit = eden()->soft_end();
1014 if (old_limit < eden()->end()) {
1015 // Tell the next generation we reached a limit.
1016 HeapWord* new_limit =
1017 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1018 if (new_limit != NULL) {
1019 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1020 } else {
1021 assert(eden()->soft_end() == eden()->end(),
1022 "invalid state after allocation_limit_reached returned null");
1023 }
1024 } else {
1025 // The allocation failed and the soft limit is equal to the hard limit,
1026 // there are no reasons to do an attempt to allocate
1027 assert(old_limit == eden()->end(), "sanity check");
1028 break;
1029 }
1030 // Try to allocate until succeeded or the soft limit can't be adjusted
1031 result = eden()->par_allocate(word_size);
1032 } while (result == NULL);
1034 // If the eden is full and the last collection bailed out, we are running
1035 // out of heap space, and we try to allocate the from-space, too.
1036 // allocate_from_space can't be inlined because that would introduce a
1037 // circular dependency at compile time.
1038 if (result == NULL) {
1039 result = allocate_from_space(word_size);
1040 }
1041 return result;
1042 }
1044 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1045 bool is_tlab) {
1046 return eden()->par_allocate(word_size);
1047 }
1049 void DefNewGeneration::gc_prologue(bool full) {
1050 // Ensure that _end and _soft_end are the same in eden space.
1051 eden()->set_soft_end(eden()->end());
1052 }
1054 size_t DefNewGeneration::tlab_capacity() const {
1055 return eden()->capacity();
1056 }
1058 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1059 return unsafe_max_alloc_nogc();
1060 }