1 /*
2 * Copyright (c) 2001, 2010, 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/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/generationSpec.hpp"
34 #include "memory/iterator.hpp"
35 #include "memory/referencePolicy.hpp"
36 #include "memory/space.inline.hpp"
37 #include "oops/instanceRefKlass.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "utilities/copy.hpp"
41 #include "utilities/stack.inline.hpp"
42 #ifdef TARGET_OS_FAMILY_linux
43 # include "thread_linux.inline.hpp"
44 #endif
45 #ifdef TARGET_OS_FAMILY_solaris
46 # include "thread_solaris.inline.hpp"
47 #endif
48 #ifdef TARGET_OS_FAMILY_windows
49 # include "thread_windows.inline.hpp"
50 #endif
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 void DefNewGeneration::IsAliveClosure::do_object(oop p) {
61 assert(false, "Do not call.");
62 }
63 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
64 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
65 }
66
67 DefNewGeneration::KeepAliveClosure::
68 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
69 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
70 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
71 _rs = (CardTableRS*)rs;
72 }
73
74 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
75 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
76
77
78 DefNewGeneration::FastKeepAliveClosure::
79 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
80 DefNewGeneration::KeepAliveClosure(cl) {
81 _boundary = g->reserved().end();
82 }
83
84 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
85 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
86
87 DefNewGeneration::EvacuateFollowersClosure::
88 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
89 ScanClosure* cur, ScanClosure* older) :
90 _gch(gch), _level(level),
91 _scan_cur_or_nonheap(cur), _scan_older(older)
92 {}
93
94 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
95 do {
96 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
97 _scan_older);
98 } while (!_gch->no_allocs_since_save_marks(_level));
99 }
100
101 DefNewGeneration::FastEvacuateFollowersClosure::
102 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
103 DefNewGeneration* gen,
104 FastScanClosure* cur, FastScanClosure* older) :
105 _gch(gch), _level(level), _gen(gen),
106 _scan_cur_or_nonheap(cur), _scan_older(older)
107 {}
108
109 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
110 do {
111 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
112 _scan_older);
113 } while (!_gch->no_allocs_since_save_marks(_level));
114 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
115 }
116
117 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
118 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
119 {
120 assert(_g->level() == 0, "Optimized for youngest generation");
121 _boundary = _g->reserved().end();
122 }
123
124 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
125 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
126
127 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
128 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
129 {
130 assert(_g->level() == 0, "Optimized for youngest generation");
131 _boundary = _g->reserved().end();
132 }
133
134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
136
137 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
138 OopClosure(g->ref_processor()), _g(g)
139 {
140 assert(_g->level() == 0, "Optimized for youngest generation");
141 _boundary = _g->reserved().end();
142 }
143
144 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
145 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
146
147 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
148 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
149
150 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
151 size_t initial_size,
152 int level,
153 const char* policy)
154 : Generation(rs, initial_size, level),
155 _promo_failure_drain_in_progress(false),
156 _should_allocate_from_space(false)
157 {
158 MemRegion cmr((HeapWord*)_virtual_space.low(),
159 (HeapWord*)_virtual_space.high());
160 Universe::heap()->barrier_set()->resize_covered_region(cmr);
161
162 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
163 _eden_space = new ConcEdenSpace(this);
164 } else {
165 _eden_space = new EdenSpace(this);
166 }
167 _from_space = new ContiguousSpace();
168 _to_space = new ContiguousSpace();
169
170 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
171 vm_exit_during_initialization("Could not allocate a new gen space");
172
173 // Compute the maximum eden and survivor space sizes. These sizes
174 // are computed assuming the entire reserved space is committed.
175 // These values are exported as performance counters.
176 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
177 uintx size = _virtual_space.reserved_size();
178 _max_survivor_size = compute_survivor_size(size, alignment);
179 _max_eden_size = size - (2*_max_survivor_size);
180
181 // allocate the performance counters
182
183 // Generation counters -- generation 0, 3 subspaces
184 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
185 _gc_counters = new CollectorCounters(policy, 0);
186
187 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
188 _gen_counters);
189 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
190 _gen_counters);
191 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
192 _gen_counters);
193
194 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
195 update_counters();
196 _next_gen = NULL;
197 _tenuring_threshold = MaxTenuringThreshold;
198 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
199 }
200
201 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
202 bool clear_space,
203 bool mangle_space) {
204 uintx alignment =
205 GenCollectedHeap::heap()->collector_policy()->min_alignment();
206
207 // If the spaces are being cleared (only done at heap initialization
208 // currently), the survivor spaces need not be empty.
209 // Otherwise, no care is taken for used areas in the survivor spaces
210 // so check.
211 assert(clear_space || (to()->is_empty() && from()->is_empty()),
212 "Initialization of the survivor spaces assumes these are empty");
213
214 // Compute sizes
215 uintx size = _virtual_space.committed_size();
216 uintx survivor_size = compute_survivor_size(size, alignment);
217 uintx eden_size = size - (2*survivor_size);
218 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
219
220 if (eden_size < minimum_eden_size) {
221 // May happen due to 64Kb rounding, if so adjust eden size back up
222 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
223 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
224 uintx unaligned_survivor_size =
225 align_size_down(maximum_survivor_size, alignment);
226 survivor_size = MAX2(unaligned_survivor_size, alignment);
227 eden_size = size - (2*survivor_size);
228 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
229 assert(eden_size >= minimum_eden_size, "just checking");
230 }
231
232 char *eden_start = _virtual_space.low();
233 char *from_start = eden_start + eden_size;
234 char *to_start = from_start + survivor_size;
235 char *to_end = to_start + survivor_size;
236
237 assert(to_end == _virtual_space.high(), "just checking");
238 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
239 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
240 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
241
242 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
243 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
244 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
245
246 // A minimum eden size implies that there is a part of eden that
247 // is being used and that affects the initialization of any
248 // newly formed eden.
249 bool live_in_eden = minimum_eden_size > 0;
250
251 // If not clearing the spaces, do some checking to verify that
252 // the space are already mangled.
253 if (!clear_space) {
254 // Must check mangling before the spaces are reshaped. Otherwise,
255 // the bottom or end of one space may have moved into another
256 // a failure of the check may not correctly indicate which space
257 // is not properly mangled.
258 if (ZapUnusedHeapArea) {
259 HeapWord* limit = (HeapWord*) _virtual_space.high();
260 eden()->check_mangled_unused_area(limit);
261 from()->check_mangled_unused_area(limit);
262 to()->check_mangled_unused_area(limit);
263 }
264 }
265
266 // Reset the spaces for their new regions.
267 eden()->initialize(edenMR,
268 clear_space && !live_in_eden,
269 SpaceDecorator::Mangle);
270 // If clear_space and live_in_eden, we will not have cleared any
271 // portion of eden above its top. This can cause newly
272 // expanded space not to be mangled if using ZapUnusedHeapArea.
273 // We explicitly do such mangling here.
274 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
275 eden()->mangle_unused_area();
276 }
277 from()->initialize(fromMR, clear_space, mangle_space);
278 to()->initialize(toMR, clear_space, mangle_space);
279
280 // Set next compaction spaces.
281 eden()->set_next_compaction_space(from());
282 // The to-space is normally empty before a compaction so need
283 // not be considered. The exception is during promotion
284 // failure handling when to-space can contain live objects.
285 from()->set_next_compaction_space(NULL);
286 }
287
288 void DefNewGeneration::swap_spaces() {
289 ContiguousSpace* s = from();
290 _from_space = to();
291 _to_space = s;
292 eden()->set_next_compaction_space(from());
293 // The to-space is normally empty before a compaction so need
294 // not be considered. The exception is during promotion
295 // failure handling when to-space can contain live objects.
296 from()->set_next_compaction_space(NULL);
297
298 if (UsePerfData) {
299 CSpaceCounters* c = _from_counters;
300 _from_counters = _to_counters;
301 _to_counters = c;
302 }
303 }
304
305 bool DefNewGeneration::expand(size_t bytes) {
306 MutexLocker x(ExpandHeap_lock);
307 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
308 bool success = _virtual_space.expand_by(bytes);
309 if (success && ZapUnusedHeapArea) {
310 // Mangle newly committed space immediately because it
311 // can be done here more simply that after the new
312 // spaces have been computed.
313 HeapWord* new_high = (HeapWord*) _virtual_space.high();
314 MemRegion mangle_region(prev_high, new_high);
315 SpaceMangler::mangle_region(mangle_region);
316 }
317
318 // Do not attempt an expand-to-the reserve size. The
319 // request should properly observe the maximum size of
320 // the generation so an expand-to-reserve should be
321 // unnecessary. Also a second call to expand-to-reserve
322 // value potentially can cause an undue expansion.
323 // For example if the first expand fail for unknown reasons,
324 // but the second succeeds and expands the heap to its maximum
325 // value.
326 if (GC_locker::is_active()) {
327 if (PrintGC && Verbose) {
328 gclog_or_tty->print_cr("Garbage collection disabled, "
329 "expanded heap instead");
330 }
331 }
332
333 return success;
334 }
335
336
337 void DefNewGeneration::compute_new_size() {
338 // This is called after a gc that includes the following generation
339 // (which is required to exist.) So from-space will normally be empty.
340 // Note that we check both spaces, since if scavenge failed they revert roles.
341 // If not we bail out (otherwise we would have to relocate the objects)
342 if (!from()->is_empty() || !to()->is_empty()) {
343 return;
344 }
345
346 int next_level = level() + 1;
347 GenCollectedHeap* gch = GenCollectedHeap::heap();
348 assert(next_level < gch->_n_gens,
349 "DefNewGeneration cannot be an oldest gen");
350
351 Generation* next_gen = gch->_gens[next_level];
352 size_t old_size = next_gen->capacity();
353 size_t new_size_before = _virtual_space.committed_size();
354 size_t min_new_size = spec()->init_size();
355 size_t max_new_size = reserved().byte_size();
356 assert(min_new_size <= new_size_before &&
357 new_size_before <= max_new_size,
358 "just checking");
359 // All space sizes must be multiples of Generation::GenGrain.
360 size_t alignment = Generation::GenGrain;
361
362 // Compute desired new generation size based on NewRatio and
363 // NewSizeThreadIncrease
364 size_t desired_new_size = old_size/NewRatio;
365 int threads_count = Threads::number_of_non_daemon_threads();
366 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
367 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
368
369 // Adjust new generation size
370 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
371 assert(desired_new_size <= max_new_size, "just checking");
372
373 bool changed = false;
374 if (desired_new_size > new_size_before) {
375 size_t change = desired_new_size - new_size_before;
376 assert(change % alignment == 0, "just checking");
377 if (expand(change)) {
378 changed = true;
379 }
380 // If the heap failed to expand to the desired size,
381 // "changed" will be false. If the expansion failed
382 // (and at this point it was expected to succeed),
383 // ignore the failure (leaving "changed" as false).
384 }
385 if (desired_new_size < new_size_before && eden()->is_empty()) {
386 // bail out of shrinking if objects in eden
387 size_t change = new_size_before - desired_new_size;
388 assert(change % alignment == 0, "just checking");
389 _virtual_space.shrink_by(change);
390 changed = true;
391 }
392 if (changed) {
393 // The spaces have already been mangled at this point but
394 // may not have been cleared (set top = bottom) and should be.
395 // Mangling was done when the heap was being expanded.
396 compute_space_boundaries(eden()->used(),
397 SpaceDecorator::Clear,
398 SpaceDecorator::DontMangle);
399 MemRegion cmr((HeapWord*)_virtual_space.low(),
400 (HeapWord*)_virtual_space.high());
401 Universe::heap()->barrier_set()->resize_covered_region(cmr);
402 if (Verbose && PrintGC) {
403 size_t new_size_after = _virtual_space.committed_size();
404 size_t eden_size_after = eden()->capacity();
405 size_t survivor_size_after = from()->capacity();
406 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
407 SIZE_FORMAT "K [eden="
408 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
409 new_size_before/K, new_size_after/K,
410 eden_size_after/K, survivor_size_after/K);
411 if (WizardMode) {
412 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
413 thread_increase_size/K, threads_count);
414 }
415 gclog_or_tty->cr();
416 }
417 }
418 }
419
420 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
421 // $$$ This may be wrong in case of "scavenge failure"?
422 eden()->object_iterate(cl);
423 }
424
425 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
426 assert(false, "NYI -- are you sure you want to call this?");
427 }
428
429
430 size_t DefNewGeneration::capacity() const {
431 return eden()->capacity()
432 + from()->capacity(); // to() is only used during scavenge
433 }
434
435
436 size_t DefNewGeneration::used() const {
437 return eden()->used()
438 + from()->used(); // to() is only used during scavenge
439 }
440
441
442 size_t DefNewGeneration::free() const {
443 return eden()->free()
444 + from()->free(); // to() is only used during scavenge
445 }
446
447 size_t DefNewGeneration::max_capacity() const {
448 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
449 const size_t reserved_bytes = reserved().byte_size();
450 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
451 }
452
453 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
454 return eden()->free();
455 }
456
457 size_t DefNewGeneration::capacity_before_gc() const {
458 return eden()->capacity();
459 }
460
461 size_t DefNewGeneration::contiguous_available() const {
462 return eden()->free();
463 }
464
465
466 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
467 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
468
469 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
470 eden()->object_iterate(blk);
471 from()->object_iterate(blk);
472 }
473
474
475 void DefNewGeneration::space_iterate(SpaceClosure* blk,
476 bool usedOnly) {
477 blk->do_space(eden());
478 blk->do_space(from());
479 blk->do_space(to());
480 }
481
482 // The last collection bailed out, we are running out of heap space,
483 // so we try to allocate the from-space, too.
484 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
485 HeapWord* result = NULL;
486 if (PrintGC && Verbose) {
487 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
488 " will_fail: %s"
489 " heap_lock: %s"
490 " free: " SIZE_FORMAT,
491 size,
492 GenCollectedHeap::heap()->incremental_collection_will_fail() ? "true" : "false",
493 Heap_lock->is_locked() ? "locked" : "unlocked",
494 from()->free());
495 }
496 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
497 if (Heap_lock->owned_by_self() ||
498 (SafepointSynchronize::is_at_safepoint() &&
499 Thread::current()->is_VM_thread())) {
500 // If the Heap_lock is not locked by this thread, this will be called
501 // again later with the Heap_lock held.
502 result = from()->allocate(size);
503 } else if (PrintGC && Verbose) {
504 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
505 }
506 } else if (PrintGC && Verbose) {
507 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
508 }
509 if (PrintGC && Verbose) {
510 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
511 }
512 return result;
513 }
514
515 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
516 bool is_tlab,
517 bool parallel) {
518 // We don't attempt to expand the young generation (but perhaps we should.)
519 return allocate(size, is_tlab);
520 }
521
522
523 void DefNewGeneration::collect(bool full,
524 bool clear_all_soft_refs,
525 size_t size,
526 bool is_tlab) {
527 assert(full || size > 0, "otherwise we don't want to collect");
528 GenCollectedHeap* gch = GenCollectedHeap::heap();
529 _next_gen = gch->next_gen(this);
530 assert(_next_gen != NULL,
531 "This must be the youngest gen, and not the only gen");
532
533 // If the next generation is too full to accomodate promotion
534 // from this generation, pass on collection; let the next generation
535 // do it.
536 if (!collection_attempt_is_safe()) {
537 gch->set_incremental_collection_will_fail();
538 return;
539 }
540 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
541
542 init_assuming_no_promotion_failure();
543
544 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
545 // Capture heap used before collection (for printing).
546 size_t gch_prev_used = gch->used();
547
548 SpecializationStats::clear();
549
550 // These can be shared for all code paths
551 IsAliveClosure is_alive(this);
552 ScanWeakRefClosure scan_weak_ref(this);
553
554 age_table()->clear();
555 to()->clear(SpaceDecorator::Mangle);
556
557 gch->rem_set()->prepare_for_younger_refs_iterate(false);
558
559 assert(gch->no_allocs_since_save_marks(0),
560 "save marks have not been newly set.");
561
562 // Not very pretty.
563 CollectorPolicy* cp = gch->collector_policy();
564
565 FastScanClosure fsc_with_no_gc_barrier(this, false);
566 FastScanClosure fsc_with_gc_barrier(this, true);
567
568 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
569 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
570 &fsc_with_no_gc_barrier,
571 &fsc_with_gc_barrier);
572
573 assert(gch->no_allocs_since_save_marks(0),
574 "save marks have not been newly set.");
575
576 gch->gen_process_strong_roots(_level,
577 true, // Process younger gens, if any,
578 // as strong roots.
579 true, // activate StrongRootsScope
580 false, // not collecting perm generation.
581 SharedHeap::SO_AllClasses,
582 &fsc_with_no_gc_barrier,
583 true, // walk *all* scavengable nmethods
584 &fsc_with_gc_barrier);
585
586 // "evacuate followers".
587 evacuate_followers.do_void();
588
589 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
590 ReferenceProcessor* rp = ref_processor();
591 rp->setup_policy(clear_all_soft_refs);
592 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
593 NULL);
594 if (!promotion_failed()) {
595 // Swap the survivor spaces.
596 eden()->clear(SpaceDecorator::Mangle);
597 from()->clear(SpaceDecorator::Mangle);
598 if (ZapUnusedHeapArea) {
599 // This is now done here because of the piece-meal mangling which
600 // can check for valid mangling at intermediate points in the
601 // collection(s). When a minor collection fails to collect
602 // sufficient space resizing of the young generation can occur
603 // an redistribute the spaces in the young generation. Mangle
604 // here so that unzapped regions don't get distributed to
605 // other spaces.
606 to()->mangle_unused_area();
607 }
608 swap_spaces();
609
610 assert(to()->is_empty(), "to space should be empty now");
611
612 // Set the desired survivor size to half the real survivor space
613 _tenuring_threshold =
614 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
615
616 // A successful scavenge should restart the GC time limit count which is
617 // for full GC's.
618 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
619 size_policy->reset_gc_overhead_limit_count();
620 if (PrintGC && !PrintGCDetails) {
621 gch->print_heap_change(gch_prev_used);
622 }
623 } else {
624 assert(HandlePromotionFailure,
625 "Should not be here unless promotion failure handling is on");
626 assert(_promo_failure_scan_stack.is_empty(), "post condition");
627 _promo_failure_scan_stack.clear(true); // Clear cached segments.
628
629 remove_forwarding_pointers();
630 if (PrintGCDetails) {
631 gclog_or_tty->print(" (promotion failed) ");
632 }
633 // Add to-space to the list of space to compact
634 // when a promotion failure has occurred. In that
635 // case there can be live objects in to-space
636 // as a result of a partial evacuation of eden
637 // and from-space.
638 swap_spaces(); // For uniformity wrt ParNewGeneration.
639 from()->set_next_compaction_space(to());
640 gch->set_incremental_collection_will_fail();
641
642 // Inform the next generation that a promotion failure occurred.
643 _next_gen->promotion_failure_occurred();
644
645 // Reset the PromotionFailureALot counters.
646 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
647 }
648 // set new iteration safe limit for the survivor spaces
649 from()->set_concurrent_iteration_safe_limit(from()->top());
650 to()->set_concurrent_iteration_safe_limit(to()->top());
651 SpecializationStats::print();
652 update_time_of_last_gc(os::javaTimeMillis());
653 }
654
655 class RemoveForwardPointerClosure: public ObjectClosure {
656 public:
657 void do_object(oop obj) {
658 obj->init_mark();
659 }
660 };
661
662 void DefNewGeneration::init_assuming_no_promotion_failure() {
663 _promotion_failed = false;
664 from()->set_next_compaction_space(NULL);
665 }
666
667 void DefNewGeneration::remove_forwarding_pointers() {
668 RemoveForwardPointerClosure rspc;
669 eden()->object_iterate(&rspc);
670 from()->object_iterate(&rspc);
671
672 // Now restore saved marks, if any.
673 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
674 "should be the same");
675 while (!_objs_with_preserved_marks.is_empty()) {
676 oop obj = _objs_with_preserved_marks.pop();
677 markOop m = _preserved_marks_of_objs.pop();
678 obj->set_mark(m);
679 }
680 _objs_with_preserved_marks.clear(true);
681 _preserved_marks_of_objs.clear(true);
682 }
683
684 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
685 if (m->must_be_preserved_for_promotion_failure(obj)) {
686 _objs_with_preserved_marks.push(obj);
687 _preserved_marks_of_objs.push(m);
688 }
689 }
690
691 void DefNewGeneration::handle_promotion_failure(oop old) {
692 preserve_mark_if_necessary(old, old->mark());
693 if (!_promotion_failed && PrintPromotionFailure) {
694 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
695 old->size());
696 }
697
698 // forward to self
699 old->forward_to(old);
700 _promotion_failed = true;
701
702 _promo_failure_scan_stack.push(old);
703
704 if (!_promo_failure_drain_in_progress) {
705 // prevent recursion in copy_to_survivor_space()
706 _promo_failure_drain_in_progress = true;
707 drain_promo_failure_scan_stack();
708 _promo_failure_drain_in_progress = false;
709 }
710 }
711
712 oop DefNewGeneration::copy_to_survivor_space(oop old) {
713 assert(is_in_reserved(old) && !old->is_forwarded(),
714 "shouldn't be scavenging this oop");
715 size_t s = old->size();
716 oop obj = NULL;
717
718 // Try allocating obj in to-space (unless too old)
719 if (old->age() < tenuring_threshold()) {
720 obj = (oop) to()->allocate(s);
721 }
722
723 // Otherwise try allocating obj tenured
724 if (obj == NULL) {
725 obj = _next_gen->promote(old, s);
726 if (obj == NULL) {
727 if (!HandlePromotionFailure) {
728 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag
729 // is incorrectly set. In any case, its seriously wrong to be here!
730 vm_exit_out_of_memory(s*wordSize, "promotion");
731 }
732
733 handle_promotion_failure(old);
734 return old;
735 }
736 } else {
737 // Prefetch beyond obj
738 const intx interval = PrefetchCopyIntervalInBytes;
739 Prefetch::write(obj, interval);
740
741 // Copy obj
742 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
743
744 // Increment age if obj still in new generation
745 obj->incr_age();
746 age_table()->add(obj, s);
747 }
748
749 // Done, insert forward pointer to obj in this header
750 old->forward_to(obj);
751
752 return obj;
753 }
754
755 void DefNewGeneration::drain_promo_failure_scan_stack() {
756 while (!_promo_failure_scan_stack.is_empty()) {
757 oop obj = _promo_failure_scan_stack.pop();
758 obj->oop_iterate(_promo_failure_scan_stack_closure);
759 }
760 }
761
762 void DefNewGeneration::save_marks() {
763 eden()->set_saved_mark();
764 to()->set_saved_mark();
765 from()->set_saved_mark();
766 }
767
768
769 void DefNewGeneration::reset_saved_marks() {
770 eden()->reset_saved_mark();
771 to()->reset_saved_mark();
772 from()->reset_saved_mark();
773 }
774
775
776 bool DefNewGeneration::no_allocs_since_save_marks() {
777 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
778 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
779 return to()->saved_mark_at_top();
780 }
781
782 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
783 \
784 void DefNewGeneration:: \
785 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
786 cl->set_generation(this); \
787 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
788 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
789 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
790 cl->reset_generation(); \
791 save_marks(); \
792 }
793
794 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
795
796 #undef DefNew_SINCE_SAVE_MARKS_DEFN
797
798 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
799 size_t max_alloc_words) {
800 if (requestor == this || _promotion_failed) return;
801 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
802
803 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
804 if (to_space->top() > to_space->bottom()) {
805 trace("to_space not empty when contribute_scratch called");
806 }
807 */
808
809 ContiguousSpace* to_space = to();
810 assert(to_space->end() >= to_space->top(), "pointers out of order");
811 size_t free_words = pointer_delta(to_space->end(), to_space->top());
812 if (free_words >= MinFreeScratchWords) {
813 ScratchBlock* sb = (ScratchBlock*)to_space->top();
814 sb->num_words = free_words;
815 sb->next = list;
816 list = sb;
817 }
818 }
819
820 void DefNewGeneration::reset_scratch() {
821 // If contributing scratch in to_space, mangle all of
822 // to_space if ZapUnusedHeapArea. This is needed because
823 // top is not maintained while using to-space as scratch.
824 if (ZapUnusedHeapArea) {
825 to()->mangle_unused_area_complete();
826 }
827 }
828
829 bool DefNewGeneration::collection_attempt_is_safe() {
830 if (!to()->is_empty()) {
831 return false;
832 }
833 if (_next_gen == NULL) {
834 GenCollectedHeap* gch = GenCollectedHeap::heap();
835 _next_gen = gch->next_gen(this);
836 assert(_next_gen != NULL,
837 "This must be the youngest gen, and not the only gen");
838 }
839
840 // Decide if there's enough room for a full promotion
841 // When using extremely large edens, we effectively lose a
842 // large amount of old space. Use the "MaxLiveObjectEvacuationRatio"
843 // flag to reduce the minimum evacuation space requirements. If
844 // there is not enough space to evacuate eden during a scavenge,
845 // the VM will immediately exit with an out of memory error.
846 // This flag has not been tested
847 // with collectors other than simple mark & sweep.
848 //
849 // Note that with the addition of promotion failure handling, the
850 // VM will not immediately exit but will undo the young generation
851 // collection. The parameter is left here for compatibility.
852 const double evacuation_ratio = MaxLiveObjectEvacuationRatio / 100.0;
853
854 // worst_case_evacuation is based on "used()". For the case where this
855 // method is called after a collection, this is still appropriate because
856 // the case that needs to be detected is one in which a full collection
857 // has been done and has overflowed into the young generation. In that
858 // case a minor collection will fail (the overflow of the full collection
859 // means there is no space in the old generation for any promotion).
860 size_t worst_case_evacuation = (size_t)(used() * evacuation_ratio);
861
862 return _next_gen->promotion_attempt_is_safe(worst_case_evacuation,
863 HandlePromotionFailure);
864 }
865
866 void DefNewGeneration::gc_epilogue(bool full) {
867 // Check if the heap is approaching full after a collection has
868 // been done. Generally the young generation is empty at
869 // a minimum at the end of a collection. If it is not, then
870 // the heap is approaching full.
871 GenCollectedHeap* gch = GenCollectedHeap::heap();
872 clear_should_allocate_from_space();
873 if (collection_attempt_is_safe()) {
874 gch->clear_incremental_collection_will_fail();
875 } else {
876 gch->set_incremental_collection_will_fail();
877 if (full) { // we seem to be running out of space
878 set_should_allocate_from_space();
879 }
880 }
881
882 if (ZapUnusedHeapArea) {
883 eden()->check_mangled_unused_area_complete();
884 from()->check_mangled_unused_area_complete();
885 to()->check_mangled_unused_area_complete();
886 }
887
888 // update the generation and space performance counters
889 update_counters();
890 gch->collector_policy()->counters()->update_counters();
891 }
892
893 void DefNewGeneration::record_spaces_top() {
894 assert(ZapUnusedHeapArea, "Not mangling unused space");
895 eden()->set_top_for_allocations();
896 to()->set_top_for_allocations();
897 from()->set_top_for_allocations();
898 }
899
900
901 void DefNewGeneration::update_counters() {
902 if (UsePerfData) {
903 _eden_counters->update_all();
904 _from_counters->update_all();
905 _to_counters->update_all();
906 _gen_counters->update_all();
907 }
908 }
909
910 void DefNewGeneration::verify(bool allow_dirty) {
911 eden()->verify(allow_dirty);
912 from()->verify(allow_dirty);
913 to()->verify(allow_dirty);
914 }
915
916 void DefNewGeneration::print_on(outputStream* st) const {
917 Generation::print_on(st);
918 st->print(" eden");
919 eden()->print_on(st);
920 st->print(" from");
921 from()->print_on(st);
922 st->print(" to ");
923 to()->print_on(st);
924 }
925
926
927 const char* DefNewGeneration::name() const {
928 return "def new generation";
929 }
930
931 // Moved from inline file as they are not called inline
932 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
933 return eden();
934 }
935
936 HeapWord* DefNewGeneration::allocate(size_t word_size,
937 bool is_tlab) {
938 // This is the slow-path allocation for the DefNewGeneration.
939 // Most allocations are fast-path in compiled code.
940 // We try to allocate from the eden. If that works, we are happy.
941 // Note that since DefNewGeneration supports lock-free allocation, we
942 // have to use it here, as well.
943 HeapWord* result = eden()->par_allocate(word_size);
944 if (result != NULL) {
945 return result;
946 }
947 do {
948 HeapWord* old_limit = eden()->soft_end();
949 if (old_limit < eden()->end()) {
950 // Tell the next generation we reached a limit.
951 HeapWord* new_limit =
952 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
953 if (new_limit != NULL) {
954 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
955 } else {
956 assert(eden()->soft_end() == eden()->end(),
957 "invalid state after allocation_limit_reached returned null");
958 }
959 } else {
960 // The allocation failed and the soft limit is equal to the hard limit,
961 // there are no reasons to do an attempt to allocate
962 assert(old_limit == eden()->end(), "sanity check");
963 break;
964 }
965 // Try to allocate until succeeded or the soft limit can't be adjusted
966 result = eden()->par_allocate(word_size);
967 } while (result == NULL);
968
969 // If the eden is full and the last collection bailed out, we are running
970 // out of heap space, and we try to allocate the from-space, too.
971 // allocate_from_space can't be inlined because that would introduce a
972 // circular dependency at compile time.
973 if (result == NULL) {
974 result = allocate_from_space(word_size);
975 }
976 return result;
977 }
978
979 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
980 bool is_tlab) {
981 return eden()->par_allocate(word_size);
982 }
983
984 void DefNewGeneration::gc_prologue(bool full) {
985 // Ensure that _end and _soft_end are the same in eden space.
986 eden()->set_soft_end(eden()->end());
987 }
988
989 size_t DefNewGeneration::tlab_capacity() const {
990 return eden()->capacity();
991 }
992
993 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
994 return unsafe_max_alloc_nogc();
995 }