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/serial/serialHeap.inline.hpp"
28 #include "gc/serial/tenuredGeneration.hpp"
29 #include "gc/shared/adaptiveSizePolicy.hpp"
30 #include "gc/shared/ageTable.inline.hpp"
31 #include "gc/shared/cardTableRS.hpp"
32 #include "gc/shared/collectorCounters.hpp"
33 #include "gc/shared/gcHeapSummary.hpp"
34 #include "gc/shared/gcLocker.hpp"
35 #include "gc/shared/gcPolicyCounters.hpp"
36 #include "gc/shared/gcTimer.hpp"
37 #include "gc/shared/gcTrace.hpp"
38 #include "gc/shared/gcTraceTime.inline.hpp"
39 #include "gc/shared/genOopClosures.inline.hpp"
40 #include "gc/shared/generationSpec.hpp"
41 #include "gc/shared/preservedMarks.inline.hpp"
42 #include "gc/shared/referencePolicy.hpp"
43 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
44 #include "gc/shared/space.inline.hpp"
45 #include "gc/shared/spaceDecorator.hpp"
46 #include "gc/shared/strongRootsScope.hpp"
47 #include "gc/shared/weakProcessor.hpp"
48 #include "logging/log.hpp"
49 #include "memory/iterator.inline.hpp"
50 #include "memory/resourceArea.hpp"
51 #include "oops/instanceRefKlass.hpp"
52 #include "oops/oop.inline.hpp"
53 #include "runtime/atomic.hpp"
54 #include "runtime/java.hpp"
55 #include "runtime/prefetch.inline.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "utilities/align.hpp"
58 #include "utilities/copy.hpp"
59 #include "utilities/globalDefinitions.hpp"
60 #include "utilities/stack.inline.hpp"
61
62 //
63 // DefNewGeneration functions.
64
65 // Methods of protected closure types.
66
IsAliveClosure(Generation * young_gen)67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
68 assert(_young_gen->kind() == Generation::ParNew ||
69 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
70 }
71
do_object_b(oop p)72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
73 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
74 }
75
76 DefNewGeneration::KeepAliveClosure::
KeepAliveClosure(ScanWeakRefClosure * cl)77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
78 _rs = GenCollectedHeap::heap()->rem_set();
79 }
80
do_oop(oop * p)81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
do_oop(narrowOop * p)82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83
84
85 DefNewGeneration::FastKeepAliveClosure::
FastKeepAliveClosure(DefNewGeneration * g,ScanWeakRefClosure * cl)86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
87 DefNewGeneration::KeepAliveClosure(cl) {
88 _boundary = g->reserved().end();
89 }
90
do_oop(oop * p)91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
do_oop(narrowOop * p)92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93
94 DefNewGeneration::FastEvacuateFollowersClosure::
FastEvacuateFollowersClosure(SerialHeap * heap,FastScanClosure * cur,FastScanClosure * older)95 FastEvacuateFollowersClosure(SerialHeap* heap,
96 FastScanClosure* cur,
97 FastScanClosure* older) :
98 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
99 {
100 }
101
do_void()102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
103 do {
104 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
105 } while (!_heap->no_allocs_since_save_marks());
106 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
107 }
108
ScanClosure(DefNewGeneration * g,bool gc_barrier)109 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
110 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
111 {
112 _boundary = _g->reserved().end();
113 }
114
FastScanClosure(DefNewGeneration * g,bool gc_barrier)115 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
116 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
117 {
118 _boundary = _g->reserved().end();
119 }
120
do_cld(ClassLoaderData * cld)121 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
122 NOT_PRODUCT(ResourceMark rm);
123 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
124 p2i(cld),
125 cld->loader_name_and_id(),
126 cld->has_modified_oops() ? "true" : "false");
127
128 // If the cld has not been dirtied we know that there's
129 // no references into the young gen and we can skip it.
130 if (cld->has_modified_oops()) {
131 if (_accumulate_modified_oops) {
132 cld->accumulate_modified_oops();
133 }
134
135 // Tell the closure which CLD is being scanned so that it can be dirtied
136 // if oops are left pointing into the young gen.
137 _scavenge_closure->set_scanned_cld(cld);
138
139 // Clean the cld since we're going to scavenge all the metadata.
140 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
141
142 _scavenge_closure->set_scanned_cld(NULL);
143 }
144 }
145
ScanWeakRefClosure(DefNewGeneration * g)146 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
147 _g(g)
148 {
149 _boundary = _g->reserved().end();
150 }
151
DefNewGeneration(ReservedSpace rs,size_t initial_size,const char * policy)152 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
153 size_t initial_size,
154 const char* policy)
155 : Generation(rs, initial_size),
156 _preserved_marks_set(false /* in_c_heap */),
157 _promo_failure_drain_in_progress(false),
158 _should_allocate_from_space(false)
159 {
160 MemRegion cmr((HeapWord*)_virtual_space.low(),
161 (HeapWord*)_virtual_space.high());
162 GenCollectedHeap* gch = GenCollectedHeap::heap();
163
164 gch->rem_set()->resize_covered_region(cmr);
165
166 _eden_space = new ContiguousSpace();
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
174 // Compute the maximum eden and survivor space sizes. These sizes
175 // are computed assuming the entire reserved space is committed.
176 // These values are exported as performance counters.
177 uintx alignment = gch->collector_policy()->space_alignment();
178 uintx size = _virtual_space.reserved_size();
179 _max_survivor_size = compute_survivor_size(size, alignment);
180 _max_eden_size = size - (2*_max_survivor_size);
181
182 // allocate the performance counters
183 GenCollectorPolicy* gcp = gch->gen_policy();
184
185 // Generation counters -- generation 0, 3 subspaces
186 _gen_counters = new GenerationCounters("new", 0, 3,
187 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
188 _gc_counters = new CollectorCounters(policy, 0);
189
190 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
191 _gen_counters);
192 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
193 _gen_counters);
194 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
195 _gen_counters);
196
197 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
198 update_counters();
199 _old_gen = NULL;
200 _tenuring_threshold = MaxTenuringThreshold;
201 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
202
203 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
204 }
205
compute_space_boundaries(uintx minimum_eden_size,bool clear_space,bool mangle_space)206 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
207 bool clear_space,
208 bool mangle_space) {
209 uintx alignment =
210 GenCollectedHeap::heap()->collector_policy()->space_alignment();
211
212 // If the spaces are being cleared (only done at heap initialization
213 // currently), the survivor spaces need not be empty.
214 // Otherwise, no care is taken for used areas in the survivor spaces
215 // so check.
216 assert(clear_space || (to()->is_empty() && from()->is_empty()),
217 "Initialization of the survivor spaces assumes these are empty");
218
219 // Compute sizes
220 uintx size = _virtual_space.committed_size();
221 uintx survivor_size = compute_survivor_size(size, alignment);
222 uintx eden_size = size - (2*survivor_size);
223 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
224
225 if (eden_size < minimum_eden_size) {
226 // May happen due to 64Kb rounding, if so adjust eden size back up
227 minimum_eden_size = align_up(minimum_eden_size, alignment);
228 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
229 uintx unaligned_survivor_size =
230 align_down(maximum_survivor_size, alignment);
231 survivor_size = MAX2(unaligned_survivor_size, alignment);
232 eden_size = size - (2*survivor_size);
233 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
234 assert(eden_size >= minimum_eden_size, "just checking");
235 }
236
237 char *eden_start = _virtual_space.low();
238 char *from_start = eden_start + eden_size;
239 char *to_start = from_start + survivor_size;
240 char *to_end = to_start + survivor_size;
241
242 assert(to_end == _virtual_space.high(), "just checking");
243 assert(Space::is_aligned(eden_start), "checking alignment");
244 assert(Space::is_aligned(from_start), "checking alignment");
245 assert(Space::is_aligned(to_start), "checking alignment");
246
247 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
248 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
249 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
250
251 // A minimum eden size implies that there is a part of eden that
252 // is being used and that affects the initialization of any
253 // newly formed eden.
254 bool live_in_eden = minimum_eden_size > 0;
255
256 // If not clearing the spaces, do some checking to verify that
257 // the space are already mangled.
258 if (!clear_space) {
259 // Must check mangling before the spaces are reshaped. Otherwise,
260 // the bottom or end of one space may have moved into another
261 // a failure of the check may not correctly indicate which space
262 // is not properly mangled.
263 if (ZapUnusedHeapArea) {
264 HeapWord* limit = (HeapWord*) _virtual_space.high();
265 eden()->check_mangled_unused_area(limit);
266 from()->check_mangled_unused_area(limit);
267 to()->check_mangled_unused_area(limit);
268 }
269 }
270
271 // Reset the spaces for their new regions.
272 eden()->initialize(edenMR,
273 clear_space && !live_in_eden,
274 SpaceDecorator::Mangle);
275 // If clear_space and live_in_eden, we will not have cleared any
276 // portion of eden above its top. This can cause newly
277 // expanded space not to be mangled if using ZapUnusedHeapArea.
278 // We explicitly do such mangling here.
279 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
280 eden()->mangle_unused_area();
281 }
282 from()->initialize(fromMR, clear_space, mangle_space);
283 to()->initialize(toMR, clear_space, mangle_space);
284
285 // Set next compaction spaces.
286 eden()->set_next_compaction_space(from());
287 // The to-space is normally empty before a compaction so need
288 // not be considered. The exception is during promotion
289 // failure handling when to-space can contain live objects.
290 from()->set_next_compaction_space(NULL);
291 }
292
swap_spaces()293 void DefNewGeneration::swap_spaces() {
294 ContiguousSpace* s = from();
295 _from_space = to();
296 _to_space = s;
297 eden()->set_next_compaction_space(from());
298 // The to-space is normally empty before a compaction so need
299 // not be considered. The exception is during promotion
300 // failure handling when to-space can contain live objects.
301 from()->set_next_compaction_space(NULL);
302
303 if (UsePerfData) {
304 CSpaceCounters* c = _from_counters;
305 _from_counters = _to_counters;
306 _to_counters = c;
307 }
308 }
309
expand(size_t bytes)310 bool DefNewGeneration::expand(size_t bytes) {
311 MutexLocker x(ExpandHeap_lock);
312 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
313 bool success = _virtual_space.expand_by(bytes);
314 if (success && ZapUnusedHeapArea) {
315 // Mangle newly committed space immediately because it
316 // can be done here more simply that after the new
317 // spaces have been computed.
318 HeapWord* new_high = (HeapWord*) _virtual_space.high();
319 MemRegion mangle_region(prev_high, new_high);
320 SpaceMangler::mangle_region(mangle_region);
321 }
322
323 // Do not attempt an expand-to-the reserve size. The
324 // request should properly observe the maximum size of
325 // the generation so an expand-to-reserve should be
326 // unnecessary. Also a second call to expand-to-reserve
327 // value potentially can cause an undue expansion.
328 // For example if the first expand fail for unknown reasons,
329 // but the second succeeds and expands the heap to its maximum
330 // value.
331 if (GCLocker::is_active()) {
332 log_debug(gc)("Garbage collection disabled, expanded heap instead");
333 }
334
335 return success;
336 }
337
adjust_for_thread_increase(size_t new_size_candidate,size_t new_size_before,size_t alignment) const338 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
339 size_t new_size_before,
340 size_t alignment) const {
341 size_t desired_new_size = new_size_before;
342
343 if (NewSizeThreadIncrease > 0) {
344 int threads_count;
345 size_t thread_increase_size = 0;
346
347 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
348 threads_count = Threads::number_of_non_daemon_threads();
349 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
350 thread_increase_size = threads_count * NewSizeThreadIncrease;
351
352 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
353 if (new_size_candidate <= max_uintx - thread_increase_size) {
354 new_size_candidate += thread_increase_size;
355
356 // 3. Check an overflow at 'align_up'.
357 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
358 if (new_size_candidate <= aligned_max) {
359 desired_new_size = align_up(new_size_candidate, alignment);
360 }
361 }
362 }
363 }
364
365 return desired_new_size;
366 }
367
compute_new_size()368 void DefNewGeneration::compute_new_size() {
369 // This is called after a GC that includes the old generation, so from-space
370 // will normally be empty.
371 // Note that we check both spaces, since if scavenge failed they revert roles.
372 // If not we bail out (otherwise we would have to relocate the objects).
373 if (!from()->is_empty() || !to()->is_empty()) {
374 return;
375 }
376
377 GenCollectedHeap* gch = GenCollectedHeap::heap();
378
379 size_t old_size = gch->old_gen()->capacity();
380 size_t new_size_before = _virtual_space.committed_size();
381 size_t min_new_size = initial_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;
388
389 int threads_count = 0;
390 size_t thread_increase_size = 0;
391
392 size_t new_size_candidate = old_size / NewRatio;
393 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
394 // and reverts to previous value if any overflow happens
395 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
396
397 // Adjust new generation size
398 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
399 assert(desired_new_size <= max_new_size, "just checking");
400
401 bool changed = false;
402 if (desired_new_size > new_size_before) {
403 size_t change = desired_new_size - new_size_before;
404 assert(change % alignment == 0, "just checking");
405 if (expand(change)) {
406 changed = true;
407 }
408 // If the heap failed to expand to the desired size,
409 // "changed" will be false. If the expansion failed
410 // (and at this point it was expected to succeed),
411 // ignore the failure (leaving "changed" as false).
412 }
413 if (desired_new_size < new_size_before && eden()->is_empty()) {
414 // bail out of shrinking if objects in eden
415 size_t change = new_size_before - desired_new_size;
416 assert(change % alignment == 0, "just checking");
417 _virtual_space.shrink_by(change);
418 changed = true;
419 }
420 if (changed) {
421 // The spaces have already been mangled at this point but
422 // may not have been cleared (set top = bottom) and should be.
423 // Mangling was done when the heap was being expanded.
424 compute_space_boundaries(eden()->used(),
425 SpaceDecorator::Clear,
426 SpaceDecorator::DontMangle);
427 MemRegion cmr((HeapWord*)_virtual_space.low(),
428 (HeapWord*)_virtual_space.high());
429 gch->rem_set()->resize_covered_region(cmr);
430
431 log_debug(gc, ergo, heap)(
432 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
433 new_size_before/K, _virtual_space.committed_size()/K,
434 eden()->capacity()/K, from()->capacity()/K);
435 log_trace(gc, ergo, heap)(
436 " [allowed " SIZE_FORMAT "K extra for %d threads]",
437 thread_increase_size/K, threads_count);
438 }
439 }
440
younger_refs_iterate(OopsInGenClosure * cl,uint n_threads)441 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
442 assert(false, "NYI -- are you sure you want to call this?");
443 }
444
445
capacity() const446 size_t DefNewGeneration::capacity() const {
447 return eden()->capacity()
448 + from()->capacity(); // to() is only used during scavenge
449 }
450
451
used() const452 size_t DefNewGeneration::used() const {
453 return eden()->used()
454 + from()->used(); // to() is only used during scavenge
455 }
456
457
free() const458 size_t DefNewGeneration::free() const {
459 return eden()->free()
460 + from()->free(); // to() is only used during scavenge
461 }
462
max_capacity() const463 size_t DefNewGeneration::max_capacity() const {
464 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
465 const size_t reserved_bytes = reserved().byte_size();
466 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
467 }
468
unsafe_max_alloc_nogc() const469 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
470 return eden()->free();
471 }
472
capacity_before_gc() const473 size_t DefNewGeneration::capacity_before_gc() const {
474 return eden()->capacity();
475 }
476
contiguous_available() const477 size_t DefNewGeneration::contiguous_available() const {
478 return eden()->free();
479 }
480
481
top_addr() const482 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
end_addr() const483 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
484
object_iterate(ObjectClosure * blk)485 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
486 eden()->object_iterate(blk);
487 from()->object_iterate(blk);
488 }
489
490
space_iterate(SpaceClosure * blk,bool usedOnly)491 void DefNewGeneration::space_iterate(SpaceClosure* blk,
492 bool usedOnly) {
493 blk->do_space(eden());
494 blk->do_space(from());
495 blk->do_space(to());
496 }
497
498 // The last collection bailed out, we are running out of heap space,
499 // so we try to allocate the from-space, too.
allocate_from_space(size_t size)500 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
501 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
502
503 // If the Heap_lock is not locked by this thread, this will be called
504 // again later with the Heap_lock held.
505 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
506
507 HeapWord* result = NULL;
508 if (do_alloc) {
509 result = from()->allocate(size);
510 }
511
512 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
513 size,
514 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
515 "true" : "false",
516 Heap_lock->is_locked() ? "locked" : "unlocked",
517 from()->free(),
518 should_try_alloc ? "" : " should_allocate_from_space: NOT",
519 do_alloc ? " Heap_lock is not owned by self" : "",
520 result == NULL ? "NULL" : "object");
521
522 return result;
523 }
524
expand_and_allocate(size_t size,bool is_tlab,bool parallel)525 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
526 bool is_tlab,
527 bool parallel) {
528 // We don't attempt to expand the young generation (but perhaps we should.)
529 return allocate(size, is_tlab);
530 }
531
adjust_desired_tenuring_threshold()532 void DefNewGeneration::adjust_desired_tenuring_threshold() {
533 // Set the desired survivor size to half the real survivor space
534 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
535 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
536
537 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
538
539 if (UsePerfData) {
540 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
541 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
542 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
543 }
544
545 age_table()->print_age_table(_tenuring_threshold);
546 }
547
collect(bool full,bool clear_all_soft_refs,size_t size,bool is_tlab)548 void DefNewGeneration::collect(bool full,
549 bool clear_all_soft_refs,
550 size_t size,
551 bool is_tlab) {
552 assert(full || size > 0, "otherwise we don't want to collect");
553
554 SerialHeap* heap = SerialHeap::heap();
555
556 _gc_timer->register_gc_start();
557 DefNewTracer gc_tracer;
558 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
559
560 _old_gen = heap->old_gen();
561
562 // If the next generation is too full to accommodate promotion
563 // from this generation, pass on collection; let the next generation
564 // do it.
565 if (!collection_attempt_is_safe()) {
566 log_trace(gc)(":: Collection attempt not safe ::");
567 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
568 return;
569 }
570 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
571
572 init_assuming_no_promotion_failure();
573
574 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
575
576 heap->trace_heap_before_gc(&gc_tracer);
577
578 // These can be shared for all code paths
579 IsAliveClosure is_alive(this);
580 ScanWeakRefClosure scan_weak_ref(this);
581
582 age_table()->clear();
583 to()->clear(SpaceDecorator::Mangle);
584 // The preserved marks should be empty at the start of the GC.
585 _preserved_marks_set.init(1);
586
587 heap->rem_set()->prepare_for_younger_refs_iterate(false);
588
589 assert(heap->no_allocs_since_save_marks(),
590 "save marks have not been newly set.");
591
592 FastScanClosure fsc_with_no_gc_barrier(this, false);
593 FastScanClosure fsc_with_gc_barrier(this, true);
594
595 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
596 heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
597
598 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
599 FastEvacuateFollowersClosure evacuate_followers(heap,
600 &fsc_with_no_gc_barrier,
601 &fsc_with_gc_barrier);
602
603 assert(heap->no_allocs_since_save_marks(),
604 "save marks have not been newly set.");
605
606 {
607 // DefNew needs to run with n_threads == 0, to make sure the serial
608 // version of the card table scanning code is used.
609 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
610 StrongRootsScope srs(0);
611
612 heap->young_process_roots(&srs,
613 &fsc_with_no_gc_barrier,
614 &fsc_with_gc_barrier,
615 &cld_scan_closure);
616 }
617
618 // "evacuate followers".
619 evacuate_followers.do_void();
620
621 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
622 ReferenceProcessor* rp = ref_processor();
623 rp->setup_policy(clear_all_soft_refs);
624 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
625 const ReferenceProcessorStats& stats =
626 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
627 NULL, &pt);
628 gc_tracer.report_gc_reference_stats(stats);
629 gc_tracer.report_tenuring_threshold(tenuring_threshold());
630 pt.print_all_references();
631
632 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
633
634 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
635
636 // Verify that the usage of keep_alive didn't copy any objects.
637 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
638
639 if (!_promotion_failed) {
640 // Swap the survivor spaces.
641 eden()->clear(SpaceDecorator::Mangle);
642 from()->clear(SpaceDecorator::Mangle);
643 if (ZapUnusedHeapArea) {
644 // This is now done here because of the piece-meal mangling which
645 // can check for valid mangling at intermediate points in the
646 // collection(s). When a young collection fails to collect
647 // sufficient space resizing of the young generation can occur
648 // an redistribute the spaces in the young generation. Mangle
649 // here so that unzapped regions don't get distributed to
650 // other spaces.
651 to()->mangle_unused_area();
652 }
653 swap_spaces();
654
655 assert(to()->is_empty(), "to space should be empty now");
656
657 adjust_desired_tenuring_threshold();
658
659 // A successful scavenge should restart the GC time limit count which is
660 // for full GC's.
661 AdaptiveSizePolicy* size_policy = heap->size_policy();
662 size_policy->reset_gc_overhead_limit_count();
663 assert(!heap->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.
667
668 remove_forwarding_pointers();
669 log_info(gc, promotion)("Promotion failed");
670 // Add to-space to the list of space to compact
671 // when a promotion failure has occurred. In that
672 // case there can be live objects in to-space
673 // as a result of a partial evacuation of eden
674 // and from-space.
675 swap_spaces(); // For uniformity wrt ParNewGeneration.
676 from()->set_next_compaction_space(to());
677 heap->set_incremental_collection_failed();
678
679 // Inform the next generation that a promotion failure occurred.
680 _old_gen->promotion_failure_occurred();
681 gc_tracer.report_promotion_failed(_promotion_failed_info);
682
683 // Reset the PromotionFailureALot counters.
684 NOT_PRODUCT(heap->reset_promotion_should_fail();)
685 }
686 // We should have processed and cleared all the preserved marks.
687 _preserved_marks_set.reclaim();
688 // set new iteration safe limit for the survivor spaces
689 from()->set_concurrent_iteration_safe_limit(from()->top());
690 to()->set_concurrent_iteration_safe_limit(to()->top());
691
692 // We need to use a monotonically non-decreasing 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
698 heap->trace_heap_after_gc(&gc_tracer);
699
700 _gc_timer->register_gc_end();
701
702 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
703 }
704
init_assuming_no_promotion_failure()705 void DefNewGeneration::init_assuming_no_promotion_failure() {
706 _promotion_failed = false;
707 _promotion_failed_info.reset();
708 from()->set_next_compaction_space(NULL);
709 }
710
remove_forwarding_pointers()711 void DefNewGeneration::remove_forwarding_pointers() {
712 RemoveForwardedPointerClosure rspc;
713 eden()->object_iterate(&rspc);
714 from()->object_iterate(&rspc);
715 restore_preserved_marks();
716 }
717
restore_preserved_marks()718 void DefNewGeneration::restore_preserved_marks() {
719 SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
720 _preserved_marks_set.restore(&task_executor);
721 }
722
handle_promotion_failure(oop old)723 void DefNewGeneration::handle_promotion_failure(oop old) {
724 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
725
726 _promotion_failed = true;
727 _promotion_failed_info.register_copy_failure(old->size());
728 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
729 // forward to self
730 old->forward_to(old);
731
732 _promo_failure_scan_stack.push(old);
733
734 if (!_promo_failure_drain_in_progress) {
735 // prevent recursion in copy_to_survivor_space()
736 _promo_failure_drain_in_progress = true;
737 drain_promo_failure_scan_stack();
738 _promo_failure_drain_in_progress = false;
739 }
740 }
741
copy_to_survivor_space(oop old)742 oop DefNewGeneration::copy_to_survivor_space(oop old) {
743 assert(is_in_reserved(old) && !old->is_forwarded(),
744 "shouldn't be scavenging this oop");
745 size_t s = old->size();
746 oop obj = NULL;
747
748 // Try allocating obj in to-space (unless too old)
749 if (old->age() < tenuring_threshold()) {
750 obj = (oop) to()->allocate_aligned(s);
751 }
752
753 // Otherwise try allocating obj tenured
754 if (obj == NULL) {
755 obj = _old_gen->promote(old, s);
756 if (obj == NULL) {
757 handle_promotion_failure(old);
758 return old;
759 }
760 } else {
761 // Prefetch beyond obj
762 const intx interval = PrefetchCopyIntervalInBytes;
763 Prefetch::write(obj, interval);
764
765 // Copy obj
766 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
767
768 // Increment age if obj still in new generation
769 obj->incr_age();
770 age_table()->add(obj, s);
771 }
772
773 // Done, insert forward pointer to obj in this header
774 old->forward_to(obj);
775
776 return obj;
777 }
778
drain_promo_failure_scan_stack()779 void DefNewGeneration::drain_promo_failure_scan_stack() {
780 while (!_promo_failure_scan_stack.is_empty()) {
781 oop obj = _promo_failure_scan_stack.pop();
782 obj->oop_iterate(_promo_failure_scan_stack_closure);
783 }
784 }
785
save_marks()786 void DefNewGeneration::save_marks() {
787 eden()->set_saved_mark();
788 to()->set_saved_mark();
789 from()->set_saved_mark();
790 }
791
792
reset_saved_marks()793 void DefNewGeneration::reset_saved_marks() {
794 eden()->reset_saved_mark();
795 to()->reset_saved_mark();
796 from()->reset_saved_mark();
797 }
798
799
no_allocs_since_save_marks()800 bool DefNewGeneration::no_allocs_since_save_marks() {
801 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
802 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
803 return to()->saved_mark_at_top();
804 }
805
contribute_scratch(ScratchBlock * & list,Generation * requestor,size_t max_alloc_words)806 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
807 size_t max_alloc_words) {
808 if (requestor == this || _promotion_failed) {
809 return;
810 }
811 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
812
813 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
814 if (to_space->top() > to_space->bottom()) {
815 trace("to_space not empty when contribute_scratch called");
816 }
817 */
818
819 ContiguousSpace* to_space = to();
820 assert(to_space->end() >= to_space->top(), "pointers out of order");
821 size_t free_words = pointer_delta(to_space->end(), to_space->top());
822 if (free_words >= MinFreeScratchWords) {
823 ScratchBlock* sb = (ScratchBlock*)to_space->top();
824 sb->num_words = free_words;
825 sb->next = list;
826 list = sb;
827 }
828 }
829
reset_scratch()830 void DefNewGeneration::reset_scratch() {
831 // If contributing scratch in to_space, mangle all of
832 // to_space if ZapUnusedHeapArea. This is needed because
833 // top is not maintained while using to-space as scratch.
834 if (ZapUnusedHeapArea) {
835 to()->mangle_unused_area_complete();
836 }
837 }
838
collection_attempt_is_safe()839 bool DefNewGeneration::collection_attempt_is_safe() {
840 if (!to()->is_empty()) {
841 log_trace(gc)(":: to is not empty ::");
842 return false;
843 }
844 if (_old_gen == NULL) {
845 GenCollectedHeap* gch = GenCollectedHeap::heap();
846 _old_gen = gch->old_gen();
847 }
848 return _old_gen->promotion_attempt_is_safe(used());
849 }
850
gc_epilogue(bool full)851 void DefNewGeneration::gc_epilogue(bool full) {
852 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
853
854 assert(!GCLocker::is_active(), "We should not be executing here");
855 // Check if the heap is approaching full after a collection has
856 // been done. Generally the young generation is empty at
857 // a minimum at the end of a collection. If it is not, then
858 // the heap is approaching full.
859 GenCollectedHeap* gch = GenCollectedHeap::heap();
860 if (full) {
861 DEBUG_ONLY(seen_incremental_collection_failed = false;)
862 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
863 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
864 GCCause::to_string(gch->gc_cause()));
865 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
866 set_should_allocate_from_space(); // we seem to be running out of space
867 } else {
868 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
869 GCCause::to_string(gch->gc_cause()));
870 gch->clear_incremental_collection_failed(); // We just did a full collection
871 clear_should_allocate_from_space(); // if set
872 }
873 } else {
874 #ifdef ASSERT
875 // It is possible that incremental_collection_failed() == true
876 // here, because an attempted scavenge did not succeed. The policy
877 // is normally expected to cause a full collection which should
878 // clear that condition, so we should not be here twice in a row
879 // with incremental_collection_failed() == true without having done
880 // a full collection in between.
881 if (!seen_incremental_collection_failed &&
882 gch->incremental_collection_failed()) {
883 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
884 GCCause::to_string(gch->gc_cause()));
885 seen_incremental_collection_failed = true;
886 } else if (seen_incremental_collection_failed) {
887 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
888 GCCause::to_string(gch->gc_cause()));
889 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
890 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
891 !gch->incremental_collection_failed(),
892 "Twice in a row");
893 seen_incremental_collection_failed = false;
894 }
895 #endif // ASSERT
896 }
897
898 if (ZapUnusedHeapArea) {
899 eden()->check_mangled_unused_area_complete();
900 from()->check_mangled_unused_area_complete();
901 to()->check_mangled_unused_area_complete();
902 }
903
904 if (!CleanChunkPoolAsync) {
905 Chunk::clean_chunk_pool();
906 }
907
908 // update the generation and space performance counters
909 update_counters();
910 gch->counters()->update_counters();
911 }
912
record_spaces_top()913 void DefNewGeneration::record_spaces_top() {
914 assert(ZapUnusedHeapArea, "Not mangling unused space");
915 eden()->set_top_for_allocations();
916 to()->set_top_for_allocations();
917 from()->set_top_for_allocations();
918 }
919
ref_processor_init()920 void DefNewGeneration::ref_processor_init() {
921 Generation::ref_processor_init();
922 }
923
924
update_counters()925 void DefNewGeneration::update_counters() {
926 if (UsePerfData) {
927 _eden_counters->update_all();
928 _from_counters->update_all();
929 _to_counters->update_all();
930 _gen_counters->update_all();
931 }
932 }
933
verify()934 void DefNewGeneration::verify() {
935 eden()->verify();
936 from()->verify();
937 to()->verify();
938 }
939
print_on(outputStream * st) const940 void DefNewGeneration::print_on(outputStream* st) const {
941 Generation::print_on(st);
942 st->print(" eden");
943 eden()->print_on(st);
944 st->print(" from");
945 from()->print_on(st);
946 st->print(" to ");
947 to()->print_on(st);
948 }
949
950
name() const951 const char* DefNewGeneration::name() const {
952 return "def new generation";
953 }
954
955 // Moved from inline file as they are not called inline
first_compaction_space() const956 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
957 return eden();
958 }
959
allocate(size_t word_size,bool is_tlab)960 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
961 // This is the slow-path allocation for the DefNewGeneration.
962 // Most allocations are fast-path in compiled code.
963 // We try to allocate from the eden. If that works, we are happy.
964 // Note that since DefNewGeneration supports lock-free allocation, we
965 // have to use it here, as well.
966 HeapWord* result = eden()->par_allocate(word_size);
967 if (result != NULL) {
968 if (_old_gen != NULL) {
969 _old_gen->sample_eden_chunk();
970 }
971 } else {
972 // If the eden is full and the last collection bailed out, we are running
973 // out of heap space, and we try to allocate the from-space, too.
974 // allocate_from_space can't be inlined because that would introduce a
975 // circular dependency at compile time.
976 result = allocate_from_space(word_size);
977 }
978 return result;
979 }
980
par_allocate(size_t word_size,bool is_tlab)981 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
982 bool is_tlab) {
983 HeapWord* res = eden()->par_allocate(word_size);
984 if (_old_gen != NULL) {
985 _old_gen->sample_eden_chunk();
986 }
987 return res;
988 }
989
tlab_capacity() const990 size_t DefNewGeneration::tlab_capacity() const {
991 return eden()->capacity();
992 }
993
tlab_used() const994 size_t DefNewGeneration::tlab_used() const {
995 return eden()->used();
996 }
997
unsafe_max_tlab_alloc() const998 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
999 return unsafe_max_alloc_nogc();
1000 }
1001