1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/serial/defNewGeneration.inline.hpp"
27 #include "gc/shared/adaptiveSizePolicy.hpp"
28 #include "gc/shared/ageTable.inline.hpp"
29 #include "gc/shared/cardTableRS.hpp"
30 #include "gc/shared/collectorCounters.hpp"
31 #include "gc/shared/gcHeapSummary.hpp"
32 #include "gc/shared/gcLocker.hpp"
33 #include "gc/shared/gcPolicyCounters.hpp"
34 #include "gc/shared/gcTimer.hpp"
35 #include "gc/shared/gcTrace.hpp"
36 #include "gc/shared/gcTraceTime.inline.hpp"
37 #include "gc/shared/genCollectedHeap.hpp"
38 #include "gc/shared/genOopClosures.inline.hpp"
39 #include "gc/shared/generationSpec.hpp"
40 #include "gc/shared/preservedMarks.inline.hpp"
41 #include "gc/shared/referencePolicy.hpp"
42 #include "gc/shared/space.inline.hpp"
43 #include "gc/shared/spaceDecorator.hpp"
44 #include "gc/shared/strongRootsScope.hpp"
45 #include "gc/shared/weakProcessor.hpp"
46 #include "logging/log.hpp"
47 #include "memory/iterator.hpp"
48 #include "memory/resourceArea.hpp"
49 #include "oops/instanceRefKlass.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "runtime/atomic.hpp"
52 #include "runtime/java.hpp"
53 #include "runtime/prefetch.inline.hpp"
54 #include "runtime/thread.inline.hpp"
55 #include "utilities/align.hpp"
56 #include "utilities/copy.hpp"
57 #include "utilities/globalDefinitions.hpp"
58 #include "utilities/stack.inline.hpp"
59 #if INCLUDE_ALL_GCS
60 #include "gc/cms/parOopClosures.hpp"
61 #endif
62
63 //
64 // DefNewGeneration functions.
65
66 // Methods of protected closure types.
67
68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
69 assert(_young_gen->kind() == Generation::ParNew ||
70 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
71 }
72
73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
74 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
75 }
76
77 DefNewGeneration::KeepAliveClosure::
78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
79 _rs = GenCollectedHeap::heap()->rem_set();
80 }
81
82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
84
85
86 DefNewGeneration::FastKeepAliveClosure::
87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
88 DefNewGeneration::KeepAliveClosure(cl) {
89 _boundary = g->reserved().end();
90 }
91
92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
94
95 DefNewGeneration::EvacuateFollowersClosure::
96 EvacuateFollowersClosure(GenCollectedHeap* gch,
97 ScanClosure* cur,
98 ScanClosure* older) :
99 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
100 {}
101
102 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
103 do {
104 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
105 } while (!_gch->no_allocs_since_save_marks());
106 }
107
108 DefNewGeneration::FastEvacuateFollowersClosure::
109 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
110 FastScanClosure* cur,
111 FastScanClosure* older) :
112 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
113 {
114 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
115 _young_gen = (DefNewGeneration*)_gch->young_gen();
116 }
117
118 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
119 do {
120 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
121 } while (!_gch->no_allocs_since_save_marks());
122 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
123 }
124
125 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
126 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
127 {
128 _boundary = _g->reserved().end();
129 }
130
131 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
132 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
133
134 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
135 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
136 {
137 _boundary = _g->reserved().end();
138 }
139
140 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
141 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
142
143 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
144 NOT_PRODUCT(ResourceMark rm);
145 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
146 p2i(cld),
147 cld->loader_name(),
148 cld->has_modified_oops() ? "true" : "false");
149
150 // If the cld has not been dirtied we know that there's
151 // no references into the young gen and we can skip it.
152 if (cld->has_modified_oops()) {
153 if (_accumulate_modified_oops) {
154 cld->accumulate_modified_oops();
155 }
156
157 // Tell the closure which CLD is being scanned so that it can be dirtied
158 // if oops are left pointing into the young gen.
159 _scavenge_closure->set_scanned_cld(cld);
160
161 // Clean the cld since we're going to scavenge all the metadata.
162 cld->oops_do(_scavenge_closure, false, /*clear_modified_oops*/true);
163
164 _scavenge_closure->set_scanned_cld(NULL);
165 }
166 }
167
168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
169 _g(g)
170 {
171 _boundary = _g->reserved().end();
172 }
173
174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
176
177 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
178 size_t initial_size,
179 const char* policy)
180 : Generation(rs, initial_size),
181 _preserved_marks_set(false /* in_c_heap */),
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 GenCollectedHeap* gch = GenCollectedHeap::heap();
188
189 gch->rem_set()->resize_covered_region(cmr);
190
191 _eden_space = new ContiguousSpace();
192 _from_space = new ContiguousSpace();
193 _to_space = new ContiguousSpace();
194
195 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
196 vm_exit_during_initialization("Could not allocate a new gen space");
197 }
198
199 // Compute the maximum eden and survivor space sizes. These sizes
200 // are computed assuming the entire reserved space is committed.
201 // These values are exported as performance counters.
202 uintx alignment = gch->collector_policy()->space_alignment();
203 uintx size = _virtual_space.reserved_size();
204 _max_survivor_size = compute_survivor_size(size, alignment);
205 _max_eden_size = size - (2*_max_survivor_size);
206
207 // allocate the performance counters
208 GenCollectorPolicy* gcp = gch->gen_policy();
209
210 // Generation counters -- generation 0, 3 subspaces
211 _gen_counters = new GenerationCounters("new", 0, 3,
212 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
213 _gc_counters = new CollectorCounters(policy, 0);
214
215 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
216 _gen_counters);
217 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
218 _gen_counters);
219 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
220 _gen_counters);
221
222 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
223 update_counters();
224 _old_gen = NULL;
225 _tenuring_threshold = MaxTenuringThreshold;
226 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
227
228 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
229 }
230
231 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
232 bool clear_space,
233 bool mangle_space) {
234 uintx alignment =
235 GenCollectedHeap::heap()->collector_policy()->space_alignment();
236
237 // If the spaces are being cleared (only done at heap initialization
238 // currently), the survivor spaces need not be empty.
239 // Otherwise, no care is taken for used areas in the survivor spaces
240 // so check.
241 assert(clear_space || (to()->is_empty() && from()->is_empty()),
242 "Initialization of the survivor spaces assumes these are empty");
243
244 // Compute sizes
245 uintx size = _virtual_space.committed_size();
246 uintx survivor_size = compute_survivor_size(size, alignment);
247 uintx eden_size = size - (2*survivor_size);
248 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
249
250 if (eden_size < minimum_eden_size) {
251 // May happen due to 64Kb rounding, if so adjust eden size back up
252 minimum_eden_size = align_up(minimum_eden_size, alignment);
253 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
254 uintx unaligned_survivor_size =
255 align_down(maximum_survivor_size, alignment);
256 survivor_size = MAX2(unaligned_survivor_size, alignment);
257 eden_size = size - (2*survivor_size);
258 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
259 assert(eden_size >= minimum_eden_size, "just checking");
260 }
261
262 char *eden_start = _virtual_space.low();
263 char *from_start = eden_start + eden_size;
264 char *to_start = from_start + survivor_size;
265 char *to_end = to_start + survivor_size;
266
267 assert(to_end == _virtual_space.high(), "just checking");
268 assert(Space::is_aligned(eden_start), "checking alignment");
269 assert(Space::is_aligned(from_start), "checking alignment");
270 assert(Space::is_aligned(to_start), "checking alignment");
271
272 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
273 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
274 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
275
276 // A minimum eden size implies that there is a part of eden that
277 // is being used and that affects the initialization of any
278 // newly formed eden.
279 bool live_in_eden = minimum_eden_size > 0;
280
281 // If not clearing the spaces, do some checking to verify that
282 // the space are already mangled.
283 if (!clear_space) {
284 // Must check mangling before the spaces are reshaped. Otherwise,
285 // the bottom or end of one space may have moved into another
286 // a failure of the check may not correctly indicate which space
287 // is not properly mangled.
288 if (ZapUnusedHeapArea) {
289 HeapWord* limit = (HeapWord*) _virtual_space.high();
290 eden()->check_mangled_unused_area(limit);
291 from()->check_mangled_unused_area(limit);
292 to()->check_mangled_unused_area(limit);
293 }
294 }
295
296 // Reset the spaces for their new regions.
297 eden()->initialize(edenMR,
298 clear_space && !live_in_eden,
299 SpaceDecorator::Mangle);
300 // If clear_space and live_in_eden, we will not have cleared any
301 // portion of eden above its top. This can cause newly
302 // expanded space not to be mangled if using ZapUnusedHeapArea.
303 // We explicitly do such mangling here.
304 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
305 eden()->mangle_unused_area();
306 }
307 from()->initialize(fromMR, clear_space, mangle_space);
308 to()->initialize(toMR, clear_space, mangle_space);
309
310 // Set next compaction spaces.
311 eden()->set_next_compaction_space(from());
312 // The to-space is normally empty before a compaction so need
313 // not be considered. The exception is during promotion
314 // failure handling when to-space can contain live objects.
315 from()->set_next_compaction_space(NULL);
316 }
317
318 void DefNewGeneration::swap_spaces() {
319 ContiguousSpace* s = from();
320 _from_space = to();
321 _to_space = s;
322 eden()->set_next_compaction_space(from());
323 // The to-space is normally empty before a compaction so need
324 // not be considered. The exception is during promotion
325 // failure handling when to-space can contain live objects.
326 from()->set_next_compaction_space(NULL);
327
328 if (UsePerfData) {
329 CSpaceCounters* c = _from_counters;
330 _from_counters = _to_counters;
331 _to_counters = c;
332 }
333 }
334
335 bool DefNewGeneration::expand(size_t bytes) {
336 MutexLocker x(ExpandHeap_lock);
337 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
338 bool success = _virtual_space.expand_by(bytes);
339 if (success && ZapUnusedHeapArea) {
340 // Mangle newly committed space immediately because it
341 // can be done here more simply that after the new
342 // spaces have been computed.
343 HeapWord* new_high = (HeapWord*) _virtual_space.high();
344 MemRegion mangle_region(prev_high, new_high);
345 SpaceMangler::mangle_region(mangle_region);
346 }
347
348 // Do not attempt an expand-to-the reserve size. The
349 // request should properly observe the maximum size of
350 // the generation so an expand-to-reserve should be
351 // unnecessary. Also a second call to expand-to-reserve
352 // value potentially can cause an undue expansion.
353 // For example if the first expand fail for unknown reasons,
354 // but the second succeeds and expands the heap to its maximum
355 // value.
356 if (GCLocker::is_active()) {
357 log_debug(gc)("Garbage collection disabled, expanded heap instead");
358 }
359
360 return success;
361 }
362
363 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
364 size_t new_size_before,
365 size_t alignment) const {
366 size_t desired_new_size = new_size_before;
367
368 if (NewSizeThreadIncrease > 0) {
369 int threads_count;
370 size_t thread_increase_size = 0;
371
372 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
373 threads_count = Threads::number_of_non_daemon_threads();
374 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
375 thread_increase_size = threads_count * NewSizeThreadIncrease;
376
377 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
378 if (new_size_candidate <= max_uintx - thread_increase_size) {
379 new_size_candidate += thread_increase_size;
380
381 // 3. Check an overflow at 'align_up'.
382 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
383 if (new_size_candidate <= aligned_max) {
384 desired_new_size = align_up(new_size_candidate, alignment);
385 }
386 }
387 }
388 }
389
390 return desired_new_size;
391 }
392
393 void DefNewGeneration::compute_new_size() {
394 // This is called after a GC that includes the old generation, so from-space
395 // will normally be empty.
396 // Note that we check both spaces, since if scavenge failed they revert roles.
397 // If not we bail out (otherwise we would have to relocate the objects).
398 if (!from()->is_empty() || !to()->is_empty()) {
399 return;
400 }
401
402 GenCollectedHeap* gch = GenCollectedHeap::heap();
403
404 size_t old_size = gch->old_gen()->capacity();
405 size_t new_size_before = _virtual_space.committed_size();
406 size_t min_new_size = initial_size();
407 size_t max_new_size = reserved().byte_size();
408 assert(min_new_size <= new_size_before &&
409 new_size_before <= max_new_size,
410 "just checking");
411 // All space sizes must be multiples of Generation::GenGrain.
412 size_t alignment = Generation::GenGrain;
413
414 int threads_count = 0;
415 size_t thread_increase_size = 0;
416
417 size_t new_size_candidate = old_size / NewRatio;
418 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
419 // and reverts to previous value if any overflow happens
420 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
421
422 // Adjust new generation size
423 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
424 assert(desired_new_size <= max_new_size, "just checking");
425
426 bool changed = false;
427 if (desired_new_size > new_size_before) {
428 size_t change = desired_new_size - new_size_before;
429 assert(change % alignment == 0, "just checking");
430 if (expand(change)) {
431 changed = true;
432 }
433 // If the heap failed to expand to the desired size,
434 // "changed" will be false. If the expansion failed
435 // (and at this point it was expected to succeed),
436 // ignore the failure (leaving "changed" as false).
437 }
438 if (desired_new_size < new_size_before && eden()->is_empty()) {
439 // bail out of shrinking if objects in eden
440 size_t change = new_size_before - desired_new_size;
441 assert(change % alignment == 0, "just checking");
442 _virtual_space.shrink_by(change);
443 changed = true;
444 }
445 if (changed) {
446 // The spaces have already been mangled at this point but
447 // may not have been cleared (set top = bottom) and should be.
448 // Mangling was done when the heap was being expanded.
449 compute_space_boundaries(eden()->used(),
450 SpaceDecorator::Clear,
451 SpaceDecorator::DontMangle);
452 MemRegion cmr((HeapWord*)_virtual_space.low(),
453 (HeapWord*)_virtual_space.high());
454 gch->rem_set()->resize_covered_region(cmr);
455
456 log_debug(gc, ergo, heap)(
457 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
458 new_size_before/K, _virtual_space.committed_size()/K,
459 eden()->capacity()/K, from()->capacity()/K);
460 log_trace(gc, ergo, heap)(
461 " [allowed " SIZE_FORMAT "K extra for %d threads]",
462 thread_increase_size/K, threads_count);
463 }
464 }
465
466 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
467 assert(false, "NYI -- are you sure you want to call this?");
468 }
469
470
471 size_t DefNewGeneration::capacity() const {
472 return eden()->capacity()
473 + from()->capacity(); // to() is only used during scavenge
474 }
475
476
477 size_t DefNewGeneration::used() const {
478 return eden()->used()
479 + from()->used(); // to() is only used during scavenge
480 }
481
482
483 size_t DefNewGeneration::free() const {
484 return eden()->free()
485 + from()->free(); // to() is only used during scavenge
486 }
487
488 size_t DefNewGeneration::max_capacity() const {
489 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
490 const size_t reserved_bytes = reserved().byte_size();
491 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
492 }
493
494 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
495 return eden()->free();
496 }
497
498 size_t DefNewGeneration::capacity_before_gc() const {
499 return eden()->capacity();
500 }
501
502 size_t DefNewGeneration::contiguous_available() const {
503 return eden()->free();
504 }
505
506
507 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
508 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
509
510 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
511 eden()->object_iterate(blk);
512 from()->object_iterate(blk);
513 }
514
515
516 void DefNewGeneration::space_iterate(SpaceClosure* blk,
517 bool usedOnly) {
518 blk->do_space(eden());
519 blk->do_space(from());
520 blk->do_space(to());
521 }
522
523 // The last collection bailed out, we are running out of heap space,
524 // so we try to allocate the from-space, too.
525 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
526 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
527
528 // If the Heap_lock is not locked by this thread, this will be called
529 // again later with the Heap_lock held.
530 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
531
532 HeapWord* result = NULL;
533 if (do_alloc) {
534 result = from()->allocate(size);
535 }
536
537 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
538 size,
539 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
540 "true" : "false",
541 Heap_lock->is_locked() ? "locked" : "unlocked",
542 from()->free(),
543 should_try_alloc ? "" : " should_allocate_from_space: NOT",
544 do_alloc ? " Heap_lock is not owned by self" : "",
545 result == NULL ? "NULL" : "object");
546
547 return result;
548 }
549
550 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
551 bool is_tlab,
552 bool parallel) {
553 // We don't attempt to expand the young generation (but perhaps we should.)
554 return allocate(size, is_tlab);
555 }
556
557 void DefNewGeneration::adjust_desired_tenuring_threshold() {
558 // Set the desired survivor size to half the real survivor space
559 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
560 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
561
562 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
563
564 if (UsePerfData) {
565 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
566 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
567 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
568 }
569
570 age_table()->print_age_table(_tenuring_threshold);
571 }
572
573 void DefNewGeneration::collect(bool full,
574 bool clear_all_soft_refs,
575 size_t size,
576 bool is_tlab) {
577 assert(full || size > 0, "otherwise we don't want to collect");
578
579 GenCollectedHeap* gch = GenCollectedHeap::heap();
580
581 _gc_timer->register_gc_start();
582 DefNewTracer gc_tracer;
583 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
584
585 _old_gen = gch->old_gen();
586
587 // If the next generation is too full to accommodate promotion
588 // from this generation, pass on collection; let the next generation
589 // do it.
590 if (!collection_attempt_is_safe()) {
591 log_trace(gc)(":: Collection attempt not safe ::");
592 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
593 return;
594 }
595 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
596
597 init_assuming_no_promotion_failure();
598
599 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause());
600
601 gch->trace_heap_before_gc(&gc_tracer);
602
603 // These can be shared for all code paths
604 IsAliveClosure is_alive(this);
605 ScanWeakRefClosure scan_weak_ref(this);
606
607 age_table()->clear();
608 to()->clear(SpaceDecorator::Mangle);
609 // The preserved marks should be empty at the start of the GC.
610 _preserved_marks_set.init(1);
611
612 gch->rem_set()->prepare_for_younger_refs_iterate(false);
613
614 assert(gch->no_allocs_since_save_marks(),
615 "save marks have not been newly set.");
616
617 FastScanClosure fsc_with_no_gc_barrier(this, false);
618 FastScanClosure fsc_with_gc_barrier(this, true);
619
620 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
621 gch->rem_set()->cld_rem_set()->accumulate_modified_oops());
622
623 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
624 FastEvacuateFollowersClosure evacuate_followers(gch,
625 &fsc_with_no_gc_barrier,
626 &fsc_with_gc_barrier);
627
628 assert(gch->no_allocs_since_save_marks(),
629 "save marks have not been newly set.");
630
631 {
632 // DefNew needs to run with n_threads == 0, to make sure the serial
633 // version of the card table scanning code is used.
634 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
635 StrongRootsScope srs(0);
636
637 gch->young_process_roots(&srs,
638 &fsc_with_no_gc_barrier,
639 &fsc_with_gc_barrier,
640 &cld_scan_closure);
641 }
642
643 // "evacuate followers".
644 evacuate_followers.do_void();
645
646 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
647 ReferenceProcessor* rp = ref_processor();
648 rp->setup_policy(clear_all_soft_refs);
649 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q());
650 const ReferenceProcessorStats& stats =
651 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
652 NULL, &pt);
653 gc_tracer.report_gc_reference_stats(stats);
654 gc_tracer.report_tenuring_threshold(tenuring_threshold());
655 pt.print_all_references();
656
657 assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set.");
658
659 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
660
661 // Verify that the usage of keep_alive didn't copy any objects.
662 assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set.");
663
664 if (!_promotion_failed) {
665 // Swap the survivor spaces.
666 eden()->clear(SpaceDecorator::Mangle);
667 from()->clear(SpaceDecorator::Mangle);
668 if (ZapUnusedHeapArea) {
669 // This is now done here because of the piece-meal mangling which
670 // can check for valid mangling at intermediate points in the
671 // collection(s). When a young collection fails to collect
672 // sufficient space resizing of the young generation can occur
673 // an redistribute the spaces in the young generation. Mangle
674 // here so that unzapped regions don't get distributed to
675 // other spaces.
676 to()->mangle_unused_area();
677 }
678 swap_spaces();
679
680 assert(to()->is_empty(), "to space should be empty now");
681
682 adjust_desired_tenuring_threshold();
683
684 // A successful scavenge should restart the GC time limit count which is
685 // for full GC's.
686 AdaptiveSizePolicy* size_policy = gch->size_policy();
687 size_policy->reset_gc_overhead_limit_count();
688 assert(!gch->incremental_collection_failed(), "Should be clear");
689 } else {
690 assert(_promo_failure_scan_stack.is_empty(), "post condition");
691 _promo_failure_scan_stack.clear(true); // Clear cached segments.
692
693 remove_forwarding_pointers();
694 log_info(gc, promotion)("Promotion failed");
695 // Add to-space to the list of space to compact
696 // when a promotion failure has occurred. In that
697 // case there can be live objects in to-space
698 // as a result of a partial evacuation of eden
699 // and from-space.
700 swap_spaces(); // For uniformity wrt ParNewGeneration.
701 from()->set_next_compaction_space(to());
702 gch->set_incremental_collection_failed();
703
704 // Inform the next generation that a promotion failure occurred.
705 _old_gen->promotion_failure_occurred();
706 gc_tracer.report_promotion_failed(_promotion_failed_info);
707
708 // Reset the PromotionFailureALot counters.
709 NOT_PRODUCT(gch->reset_promotion_should_fail();)
710 }
711 // We should have processed and cleared all the preserved marks.
712 _preserved_marks_set.reclaim();
713 // set new iteration safe limit for the survivor spaces
714 from()->set_concurrent_iteration_safe_limit(from()->top());
715 to()->set_concurrent_iteration_safe_limit(to()->top());
716
717 // We need to use a monotonically non-decreasing time in ms
718 // or we will see time-warp warnings and os::javaTimeMillis()
719 // does not guarantee monotonicity.
720 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
721 update_time_of_last_gc(now);
722
723 gch->trace_heap_after_gc(&gc_tracer);
724
725 _gc_timer->register_gc_end();
726
727 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
728 }
729
730 void DefNewGeneration::init_assuming_no_promotion_failure() {
731 _promotion_failed = false;
732 _promotion_failed_info.reset();
733 from()->set_next_compaction_space(NULL);
734 }
735
736 void DefNewGeneration::remove_forwarding_pointers() {
737 RemoveForwardedPointerClosure rspc;
738 eden()->object_iterate(&rspc);
739 from()->object_iterate(&rspc);
740 restore_preserved_marks();
741 }
742
743 void DefNewGeneration::restore_preserved_marks() {
744 SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
745 _preserved_marks_set.restore(&task_executor);
746 }
747
748 void DefNewGeneration::handle_promotion_failure(oop old) {
749 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
750
751 _promotion_failed = true;
752 _promotion_failed_info.register_copy_failure(old->size());
753 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
754 // forward to self
755 old->forward_to(old);
756
757 _promo_failure_scan_stack.push(old);
758
759 if (!_promo_failure_drain_in_progress) {
760 // prevent recursion in copy_to_survivor_space()
761 _promo_failure_drain_in_progress = true;
762 drain_promo_failure_scan_stack();
763 _promo_failure_drain_in_progress = false;
764 }
765 }
766
767 oop DefNewGeneration::copy_to_survivor_space(oop old) {
768 assert(is_in_reserved(old) && !old->is_forwarded(),
769 "shouldn't be scavenging this oop");
770 size_t s = old->size();
771 oop obj = NULL;
772
773 // Try allocating obj in to-space (unless too old)
774 if (old->age() < tenuring_threshold()) {
775 obj = (oop) to()->allocate_aligned(s);
776 }
777
778 // Otherwise try allocating obj tenured
779 if (obj == NULL) {
780 obj = _old_gen->promote(old, s);
781 if (obj == NULL) {
782 handle_promotion_failure(old);
783 return old;
784 }
785 } else {
786 // Prefetch beyond obj
787 const intx interval = PrefetchCopyIntervalInBytes;
788 Prefetch::write(obj, interval);
789
790 // Copy obj
791 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
792
793 // Increment age if obj still in new generation
794 obj->incr_age();
795 age_table()->add(obj, s);
796 }
797
798 // Done, insert forward pointer to obj in this header
799 old->forward_to(obj);
800
801 return obj;
802 }
803
804 void DefNewGeneration::drain_promo_failure_scan_stack() {
805 while (!_promo_failure_scan_stack.is_empty()) {
806 oop obj = _promo_failure_scan_stack.pop();
807 obj->oop_iterate(_promo_failure_scan_stack_closure);
808 }
809 }
810
811 void DefNewGeneration::save_marks() {
812 eden()->set_saved_mark();
813 to()->set_saved_mark();
814 from()->set_saved_mark();
815 }
816
817
818 void DefNewGeneration::reset_saved_marks() {
819 eden()->reset_saved_mark();
820 to()->reset_saved_mark();
821 from()->reset_saved_mark();
822 }
823
824
825 bool DefNewGeneration::no_allocs_since_save_marks() {
826 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
827 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
828 return to()->saved_mark_at_top();
829 }
830
831 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
832 \
833 void DefNewGeneration:: \
834 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
835 cl->set_generation(this); \
836 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
837 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
838 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
839 cl->reset_generation(); \
840 save_marks(); \
841 }
842
843 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
844
845 #undef DefNew_SINCE_SAVE_MARKS_DEFN
846
847 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
848 size_t max_alloc_words) {
849 if (requestor == this || _promotion_failed) {
850 return;
851 }
852 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
853
854 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
855 if (to_space->top() > to_space->bottom()) {
856 trace("to_space not empty when contribute_scratch called");
857 }
858 */
859
860 ContiguousSpace* to_space = to();
861 assert(to_space->end() >= to_space->top(), "pointers out of order");
862 size_t free_words = pointer_delta(to_space->end(), to_space->top());
863 if (free_words >= MinFreeScratchWords) {
864 ScratchBlock* sb = (ScratchBlock*)to_space->top();
865 sb->num_words = free_words;
866 sb->next = list;
867 list = sb;
868 }
869 }
870
871 void DefNewGeneration::reset_scratch() {
872 // If contributing scratch in to_space, mangle all of
873 // to_space if ZapUnusedHeapArea. This is needed because
874 // top is not maintained while using to-space as scratch.
875 if (ZapUnusedHeapArea) {
876 to()->mangle_unused_area_complete();
877 }
878 }
879
880 bool DefNewGeneration::collection_attempt_is_safe() {
881 if (!to()->is_empty()) {
882 log_trace(gc)(":: to is not empty ::");
883 return false;
884 }
885 if (_old_gen == NULL) {
886 GenCollectedHeap* gch = GenCollectedHeap::heap();
887 _old_gen = gch->old_gen();
888 }
889 return _old_gen->promotion_attempt_is_safe(used());
890 }
891
892 void DefNewGeneration::gc_epilogue(bool full) {
893 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
894
895 assert(!GCLocker::is_active(), "We should not be executing here");
896 // Check if the heap is approaching full after a collection has
897 // been done. Generally the young generation is empty at
898 // a minimum at the end of a collection. If it is not, then
899 // the heap is approaching full.
900 GenCollectedHeap* gch = GenCollectedHeap::heap();
901 if (full) {
902 DEBUG_ONLY(seen_incremental_collection_failed = false;)
903 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
904 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
905 GCCause::to_string(gch->gc_cause()));
906 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
907 set_should_allocate_from_space(); // we seem to be running out of space
908 } else {
909 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
910 GCCause::to_string(gch->gc_cause()));
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 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
925 GCCause::to_string(gch->gc_cause()));
926 seen_incremental_collection_failed = true;
927 } else if (seen_incremental_collection_failed) {
928 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
929 GCCause::to_string(gch->gc_cause()));
930 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
931 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
932 !gch->incremental_collection_failed(),
933 "Twice in a row");
934 seen_incremental_collection_failed = false;
935 }
936 #endif // ASSERT
937 }
938
939 if (ZapUnusedHeapArea) {
940 eden()->check_mangled_unused_area_complete();
941 from()->check_mangled_unused_area_complete();
942 to()->check_mangled_unused_area_complete();
943 }
944
945 if (!CleanChunkPoolAsync) {
946 Chunk::clean_chunk_pool();
947 }
948
949 // update the generation and space performance counters
950 update_counters();
951 gch->counters()->update_counters();
952 }
953
954 void DefNewGeneration::record_spaces_top() {
955 assert(ZapUnusedHeapArea, "Not mangling unused space");
956 eden()->set_top_for_allocations();
957 to()->set_top_for_allocations();
958 from()->set_top_for_allocations();
959 }
960
961 void DefNewGeneration::ref_processor_init() {
962 Generation::ref_processor_init();
963 }
964
965
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 }
974
975 void DefNewGeneration::verify() {
976 eden()->verify();
977 from()->verify();
978 to()->verify();
979 }
980
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 }
990
991
992 const char* DefNewGeneration::name() const {
993 return "def new generation";
994 }
995
996 // Moved from inline file as they are not called inline
997 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
998 return eden();
999 }
1000
1001 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1002 // This is the slow-path allocation for the DefNewGeneration.
1003 // Most allocations are fast-path in compiled code.
1004 // We try to allocate from the eden. If that works, we are happy.
1005 // Note that since DefNewGeneration supports lock-free allocation, we
1006 // have to use it here, as well.
1007 HeapWord* result = eden()->par_allocate(word_size);
1008 if (result != NULL) {
1009 #if INCLUDE_ALL_GCS
1010 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1011 _old_gen->sample_eden_chunk();
1012 }
1013 #endif
1014 } else {
1015 // If the eden is full and the last collection bailed out, we are running
1016 // out of heap space, and we try to allocate the from-space, too.
1017 // allocate_from_space can't be inlined because that would introduce a
1018 // circular dependency at compile time.
1019 result = allocate_from_space(word_size);
1020 }
1021 return result;
1022 }
1023
1024 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1025 bool is_tlab) {
1026 HeapWord* res = eden()->par_allocate(word_size);
1027 #if INCLUDE_ALL_GCS
1028 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1029 _old_gen->sample_eden_chunk();
1030 }
1031 #endif
1032 return res;
1033 }
1034
1035 size_t DefNewGeneration::tlab_capacity() const {
1036 return eden()->capacity();
1037 }
1038
1039 size_t DefNewGeneration::tlab_used() const {
1040 return eden()->used();
1041 }
1042
1043 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1044 return unsafe_max_alloc_nogc();
1045 }