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 "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
31 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
32 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
34 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
35 #include "gc_implementation/parallelScavenge/psPermGen.hpp"
36 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
37 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
38 #include "gc_implementation/shared/isGCActiveMark.hpp"
39 #include "gc_implementation/shared/spaceDecorator.hpp"
40 #include "gc_interface/gcCause.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/referenceProcessor.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/biasedLocking.hpp"
46 #include "runtime/fprofiler.hpp"
47 #include "runtime/safepoint.hpp"
48 #include "runtime/vmThread.hpp"
49 #include "services/management.hpp"
50 #include "services/memoryService.hpp"
51 #include "utilities/events.hpp"
52
53 elapsedTimer PSMarkSweep::_accumulated_time;
54 unsigned int PSMarkSweep::_total_invocations = 0;
55 jlong PSMarkSweep::_time_of_last_gc = 0;
56 CollectorCounters* PSMarkSweep::_counters = NULL;
57
58 void PSMarkSweep::initialize() {
59 MemRegion mr = Universe::heap()->reserved_region();
60 _ref_processor = new ReferenceProcessor(mr,
61 true, // atomic_discovery
62 false); // mt_discovery
63 _counters = new CollectorCounters("PSMarkSweep", 1);
64 }
65
66 // This method contains all heap specific policy for invoking mark sweep.
67 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
68 // the heap. It will do nothing further. If we need to bail out for policy
69 // reasons, scavenge before full gc, or any other specialized behavior, it
70 // needs to be added here.
71 //
72 // Note that this method should only be called from the vm_thread while
73 // at a safepoint!
74 //
75 // Note that the all_soft_refs_clear flag in the collector policy
76 // may be true because this method can be called without intervening
77 // activity. For example when the heap space is tight and full measure
78 // are being taken to free space.
79
80 void PSMarkSweep::invoke(bool maximum_heap_compaction) {
81 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
82 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
83 assert(!Universe::heap()->is_gc_active(), "not reentrant");
84
85 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
86 GCCause::Cause gc_cause = heap->gc_cause();
87 PSAdaptiveSizePolicy* policy = heap->size_policy();
88 IsGCActiveMark mark;
89
90 if (ScavengeBeforeFullGC) {
91 PSScavenge::invoke_no_policy();
92 }
93
94 const bool clear_all_soft_refs =
95 heap->collector_policy()->should_clear_all_soft_refs();
96
97 int count = (maximum_heap_compaction)?1:MarkSweepAlwaysCompactCount;
98 IntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
99 PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
100 }
101
102 // This method contains no policy. You should probably
103 // be calling invoke() instead.
104 void PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
105 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
106 assert(ref_processor() != NULL, "Sanity");
107
108 if (GC_locker::check_active_before_gc()) {
109 return;
110 }
111
112 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
113 GCCause::Cause gc_cause = heap->gc_cause();
114 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
115 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
116
117 // The scope of casr should end after code that can change
118 // CollectorPolicy::_should_clear_all_soft_refs.
119 ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());
120
121 PSYoungGen* young_gen = heap->young_gen();
122 PSOldGen* old_gen = heap->old_gen();
123 PSPermGen* perm_gen = heap->perm_gen();
124
125 // Increment the invocation count
126 heap->increment_total_collections(true /* full */);
127
128 // Save information needed to minimize mangling
129 heap->record_gen_tops_before_GC();
130
131 // We need to track unique mark sweep invocations as well.
132 _total_invocations++;
133
134 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
135
136 if (PrintHeapAtGC) {
137 Universe::print_heap_before_gc();
138 }
139
140 // Fill in TLABs
141 heap->accumulate_statistics_all_tlabs();
142 heap->ensure_parsability(true); // retire TLABs
143
144 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
145 HandleMark hm; // Discard invalid handles created during verification
146 gclog_or_tty->print(" VerifyBeforeGC:");
147 Universe::verify(true);
148 }
149
150 // Verify object start arrays
151 if (VerifyObjectStartArray &&
152 VerifyBeforeGC) {
153 old_gen->verify_object_start_array();
154 perm_gen->verify_object_start_array();
155 }
156
157 heap->pre_full_gc_dump();
158
159 // Filled in below to track the state of the young gen after the collection.
160 bool eden_empty;
161 bool survivors_empty;
162 bool young_gen_empty;
163
164 {
165 HandleMark hm;
166 const bool is_system_gc = gc_cause == GCCause::_java_lang_system_gc;
167 // This is useful for debugging but don't change the output the
168 // the customer sees.
169 const char* gc_cause_str = "Full GC";
170 if (is_system_gc && PrintGCDetails) {
171 gc_cause_str = "Full GC (System)";
172 }
173 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
174 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
175 TraceTime t1(gc_cause_str, PrintGC, !PrintGCDetails, gclog_or_tty);
176 TraceCollectorStats tcs(counters());
177 TraceMemoryManagerStats tms(true /* Full GC */);
178
179 if (TraceGen1Time) accumulated_time()->start();
180
181 // Let the size policy know we're starting
182 size_policy->major_collection_begin();
183
184 // When collecting the permanent generation methodOops may be moving,
185 // so we either have to flush all bcp data or convert it into bci.
186 CodeCache::gc_prologue();
187 Threads::gc_prologue();
188 BiasedLocking::preserve_marks();
189
190 // Capture heap size before collection for printing.
191 size_t prev_used = heap->used();
192
193 // Capture perm gen size before collection for sizing.
194 size_t perm_gen_prev_used = perm_gen->used_in_bytes();
195
196 // For PrintGCDetails
197 size_t old_gen_prev_used = old_gen->used_in_bytes();
198 size_t young_gen_prev_used = young_gen->used_in_bytes();
199
200 allocate_stacks();
201
202 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
203 COMPILER2_PRESENT(DerivedPointerTable::clear());
204
205 ref_processor()->enable_discovery();
206 ref_processor()->setup_policy(clear_all_softrefs);
207
208 mark_sweep_phase1(clear_all_softrefs);
209
210 mark_sweep_phase2();
211
212 // Don't add any more derived pointers during phase3
213 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
214 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
215
216 mark_sweep_phase3();
217
218 mark_sweep_phase4();
219
220 restore_marks();
221
222 deallocate_stacks();
223
224 if (ZapUnusedHeapArea) {
225 // Do a complete mangle (top to end) because the usage for
226 // scratch does not maintain a top pointer.
227 young_gen->to_space()->mangle_unused_area_complete();
228 }
229
230 eden_empty = young_gen->eden_space()->is_empty();
231 if (!eden_empty) {
232 eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
233 }
234
235 // Update heap occupancy information which is used as
236 // input to soft ref clearing policy at the next gc.
237 Universe::update_heap_info_at_gc();
238
239 survivors_empty = young_gen->from_space()->is_empty() &&
240 young_gen->to_space()->is_empty();
241 young_gen_empty = eden_empty && survivors_empty;
242
243 BarrierSet* bs = heap->barrier_set();
244 if (bs->is_a(BarrierSet::ModRef)) {
245 ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
246 MemRegion old_mr = heap->old_gen()->reserved();
247 MemRegion perm_mr = heap->perm_gen()->reserved();
248 assert(perm_mr.end() <= old_mr.start(), "Generations out of order");
249
250 if (young_gen_empty) {
251 modBS->clear(MemRegion(perm_mr.start(), old_mr.end()));
252 } else {
253 modBS->invalidate(MemRegion(perm_mr.start(), old_mr.end()));
254 }
255 }
256
257 BiasedLocking::restore_marks();
258 Threads::gc_epilogue();
259 CodeCache::gc_epilogue();
260
261 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
262
263 ref_processor()->enqueue_discovered_references(NULL);
264
265 // Update time of last GC
266 reset_millis_since_last_gc();
267
268 // Let the size policy know we're done
269 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
270
271 if (UseAdaptiveSizePolicy) {
272
273 if (PrintAdaptiveSizePolicy) {
274 gclog_or_tty->print("AdaptiveSizeStart: ");
275 gclog_or_tty->stamp();
276 gclog_or_tty->print_cr(" collection: %d ",
277 heap->total_collections());
278 if (Verbose) {
279 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
280 " perm_gen_capacity: %d ",
281 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
282 perm_gen->capacity_in_bytes());
283 }
284 }
285
286 // Don't check if the size_policy is ready here. Let
287 // the size_policy check that internally.
288 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
289 ((gc_cause != GCCause::_java_lang_system_gc) ||
290 UseAdaptiveSizePolicyWithSystemGC)) {
291 // Calculate optimal free space amounts
292 assert(young_gen->max_size() >
293 young_gen->from_space()->capacity_in_bytes() +
294 young_gen->to_space()->capacity_in_bytes(),
295 "Sizes of space in young gen are out-of-bounds");
296 size_t max_eden_size = young_gen->max_size() -
297 young_gen->from_space()->capacity_in_bytes() -
298 young_gen->to_space()->capacity_in_bytes();
299 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
300 young_gen->eden_space()->used_in_bytes(),
301 old_gen->used_in_bytes(),
302 perm_gen->used_in_bytes(),
303 young_gen->eden_space()->capacity_in_bytes(),
304 old_gen->max_gen_size(),
305 max_eden_size,
306 true /* full gc*/,
307 gc_cause,
308 heap->collector_policy());
309
310 heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
311
312 // Don't resize the young generation at an major collection. A
313 // desired young generation size may have been calculated but
314 // resizing the young generation complicates the code because the
315 // resizing of the old generation may have moved the boundary
316 // between the young generation and the old generation. Let the
317 // young generation resizing happen at the minor collections.
318 }
319 if (PrintAdaptiveSizePolicy) {
320 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
321 heap->total_collections());
322 }
323 }
324
325 if (UsePerfData) {
326 heap->gc_policy_counters()->update_counters();
327 heap->gc_policy_counters()->update_old_capacity(
328 old_gen->capacity_in_bytes());
329 heap->gc_policy_counters()->update_young_capacity(
330 young_gen->capacity_in_bytes());
331 }
332
333 heap->resize_all_tlabs();
334
335 // We collected the perm gen, so we'll resize it here.
336 perm_gen->compute_new_size(perm_gen_prev_used);
337
338 if (TraceGen1Time) accumulated_time()->stop();
339
340 if (PrintGC) {
341 if (PrintGCDetails) {
342 // Don't print a GC timestamp here. This is after the GC so
343 // would be confusing.
344 young_gen->print_used_change(young_gen_prev_used);
345 old_gen->print_used_change(old_gen_prev_used);
346 }
347 heap->print_heap_change(prev_used);
348 // Do perm gen after heap becase prev_used does
349 // not include the perm gen (done this way in the other
350 // collectors).
351 if (PrintGCDetails) {
352 perm_gen->print_used_change(perm_gen_prev_used);
353 }
354 }
355
356 // Track memory usage and detect low memory
357 MemoryService::track_memory_usage();
358 heap->update_counters();
359 }
360
361 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
362 HandleMark hm; // Discard invalid handles created during verification
363 gclog_or_tty->print(" VerifyAfterGC:");
364 Universe::verify(false);
365 }
366
367 // Re-verify object start arrays
368 if (VerifyObjectStartArray &&
369 VerifyAfterGC) {
370 old_gen->verify_object_start_array();
371 perm_gen->verify_object_start_array();
372 }
373
374 if (ZapUnusedHeapArea) {
375 old_gen->object_space()->check_mangled_unused_area_complete();
376 perm_gen->object_space()->check_mangled_unused_area_complete();
377 }
378
379 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
380
381 if (PrintHeapAtGC) {
382 Universe::print_heap_after_gc();
383 }
384
385 heap->post_full_gc_dump();
386
387 #ifdef TRACESPINNING
388 ParallelTaskTerminator::print_termination_counts();
389 #endif
390 }
391
392 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
393 PSYoungGen* young_gen,
394 PSOldGen* old_gen) {
395 MutableSpace* const eden_space = young_gen->eden_space();
396 assert(!eden_space->is_empty(), "eden must be non-empty");
397 assert(young_gen->virtual_space()->alignment() ==
398 old_gen->virtual_space()->alignment(), "alignments do not match");
399
400 if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
401 return false;
402 }
403
404 // Both generations must be completely committed.
405 if (young_gen->virtual_space()->uncommitted_size() != 0) {
406 return false;
407 }
408 if (old_gen->virtual_space()->uncommitted_size() != 0) {
409 return false;
410 }
411
412 // Figure out how much to take from eden. Include the average amount promoted
413 // in the total; otherwise the next young gen GC will simply bail out to a
414 // full GC.
415 const size_t alignment = old_gen->virtual_space()->alignment();
416 const size_t eden_used = eden_space->used_in_bytes();
417 const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
418 const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
419 const size_t eden_capacity = eden_space->capacity_in_bytes();
420
421 if (absorb_size >= eden_capacity) {
422 return false; // Must leave some space in eden.
423 }
424
425 const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
426 if (new_young_size < young_gen->min_gen_size()) {
427 return false; // Respect young gen minimum size.
428 }
429
430 if (TraceAdaptiveGCBoundary && Verbose) {
431 gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: "
432 "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
433 "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
434 "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
435 absorb_size / K,
436 eden_capacity / K, (eden_capacity - absorb_size) / K,
437 young_gen->from_space()->used_in_bytes() / K,
438 young_gen->to_space()->used_in_bytes() / K,
439 young_gen->capacity_in_bytes() / K, new_young_size / K);
440 }
441
442 // Fill the unused part of the old gen.
443 MutableSpace* const old_space = old_gen->object_space();
444 HeapWord* const unused_start = old_space->top();
445 size_t const unused_words = pointer_delta(old_space->end(), unused_start);
446
447 if (unused_words > 0) {
448 if (unused_words < CollectedHeap::min_fill_size()) {
449 return false; // If the old gen cannot be filled, must give up.
450 }
451 CollectedHeap::fill_with_objects(unused_start, unused_words);
452 }
453
454 // Take the live data from eden and set both top and end in the old gen to
455 // eden top. (Need to set end because reset_after_change() mangles the region
456 // from end to virtual_space->high() in debug builds).
457 HeapWord* const new_top = eden_space->top();
458 old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
459 absorb_size);
460 young_gen->reset_after_change();
461 old_space->set_top(new_top);
462 old_space->set_end(new_top);
463 old_gen->reset_after_change();
464
465 // Update the object start array for the filler object and the data from eden.
466 ObjectStartArray* const start_array = old_gen->start_array();
467 for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
468 start_array->allocate_block(p);
469 }
470
471 // Could update the promoted average here, but it is not typically updated at
472 // full GCs and the value to use is unclear. Something like
473 //
474 // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
475
476 size_policy->set_bytes_absorbed_from_eden(absorb_size);
477 return true;
478 }
479
480 void PSMarkSweep::allocate_stacks() {
481 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
482 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
483
484 PSYoungGen* young_gen = heap->young_gen();
485
486 MutableSpace* to_space = young_gen->to_space();
487 _preserved_marks = (PreservedMark*)to_space->top();
488 _preserved_count = 0;
489
490 // We want to calculate the size in bytes first.
491 _preserved_count_max = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
492 // Now divide by the size of a PreservedMark
493 _preserved_count_max /= sizeof(PreservedMark);
494
495 _preserved_mark_stack = NULL;
496 _preserved_oop_stack = NULL;
497
498 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
499 _objarray_stack = new (ResourceObj::C_HEAP) GrowableArray<ObjArrayTask>(50, true);
500
501 int size = SystemDictionary::number_of_classes() * 2;
502 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
503 // (#klass/k)^2, for k ~ 10 appears a better setting, but this will have to do for
504 // now until we investigate a more optimal setting.
505 _revisit_mdo_stack = new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(size*2, true);
506 }
507
508
509 void PSMarkSweep::deallocate_stacks() {
510 if (_preserved_oop_stack) {
511 delete _preserved_mark_stack;
512 _preserved_mark_stack = NULL;
513 delete _preserved_oop_stack;
514 _preserved_oop_stack = NULL;
515 }
516
517 delete _marking_stack;
518 delete _objarray_stack;
519 delete _revisit_klass_stack;
520 delete _revisit_mdo_stack;
521 }
522
523 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
524 // Recursively traverse all live objects and mark them
525 EventMark m("1 mark object");
526 TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty);
527 trace(" 1");
528
529 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
530 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
531
532 // General strong roots.
533 {
534 ParallelScavengeHeap::ParStrongRootsScope psrs;
535 Universe::oops_do(mark_and_push_closure());
536 ReferenceProcessor::oops_do(mark_and_push_closure());
537 JNIHandles::oops_do(mark_and_push_closure()); // Global (strong) JNI handles
538 CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true);
539 Threads::oops_do(mark_and_push_closure(), &each_active_code_blob);
540 ObjectSynchronizer::oops_do(mark_and_push_closure());
541 FlatProfiler::oops_do(mark_and_push_closure());
542 Management::oops_do(mark_and_push_closure());
543 JvmtiExport::oops_do(mark_and_push_closure());
544 SystemDictionary::always_strong_oops_do(mark_and_push_closure());
545 vmSymbols::oops_do(mark_and_push_closure());
546 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
547 //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
548 }
549
550 // Flush marking stack.
551 follow_stack();
552
553 // Process reference objects found during marking
554 {
555 ref_processor()->setup_policy(clear_all_softrefs);
556 ref_processor()->process_discovered_references(
557 is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL);
558 }
559
560 // Follow system dictionary roots and unload classes
561 bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
562
563 // Follow code cache roots
564 CodeCache::do_unloading(is_alive_closure(), mark_and_push_closure(),
565 purged_class);
566 follow_stack(); // Flush marking stack
567
568 // Update subklass/sibling/implementor links of live klasses
569 follow_weak_klass_links();
570 assert(_marking_stack->is_empty(), "just drained");
571
572 // Visit memoized mdo's and clear unmarked weak refs
573 follow_mdo_weak_refs();
574 assert(_marking_stack->is_empty(), "just drained");
575
576 // Visit symbol and interned string tables and delete unmarked oops
577 SymbolTable::unlink(is_alive_closure());
578 StringTable::unlink(is_alive_closure());
579
580 assert(_marking_stack->is_empty(), "stack should be empty by now");
581 }
582
583
584 void PSMarkSweep::mark_sweep_phase2() {
585 EventMark m("2 compute new addresses");
586 TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty);
587 trace("2");
588
589 // Now all live objects are marked, compute the new object addresses.
590
591 // It is imperative that we traverse perm_gen LAST. If dead space is
592 // allowed a range of dead object may get overwritten by a dead int
593 // array. If perm_gen is not traversed last a klassOop may get
594 // overwritten. This is fine since it is dead, but if the class has dead
595 // instances we have to skip them, and in order to find their size we
596 // need the klassOop!
597 //
598 // It is not required that we traverse spaces in the same order in
599 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
600 // tracking expects us to do so. See comment under phase4.
601
602 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
603 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
604
605 PSOldGen* old_gen = heap->old_gen();
606 PSPermGen* perm_gen = heap->perm_gen();
607
608 // Begin compacting into the old gen
609 PSMarkSweepDecorator::set_destination_decorator_tenured();
610
611 // This will also compact the young gen spaces.
612 old_gen->precompact();
613
614 // Compact the perm gen into the perm gen
615 PSMarkSweepDecorator::set_destination_decorator_perm_gen();
616
617 perm_gen->precompact();
618 }
619
620 // This should be moved to the shared markSweep code!
621 class PSAlwaysTrueClosure: public BoolObjectClosure {
622 public:
623 void do_object(oop p) { ShouldNotReachHere(); }
624 bool do_object_b(oop p) { return true; }
625 };
626 static PSAlwaysTrueClosure always_true;
627
628 void PSMarkSweep::mark_sweep_phase3() {
629 // Adjust the pointers to reflect the new locations
630 EventMark m("3 adjust pointers");
631 TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty);
632 trace("3");
633
634 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
635 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
636
637 PSYoungGen* young_gen = heap->young_gen();
638 PSOldGen* old_gen = heap->old_gen();
639 PSPermGen* perm_gen = heap->perm_gen();
640
641 // General strong roots.
642 Universe::oops_do(adjust_root_pointer_closure());
643 ReferenceProcessor::oops_do(adjust_root_pointer_closure());
644 JNIHandles::oops_do(adjust_root_pointer_closure()); // Global (strong) JNI handles
645 Threads::oops_do(adjust_root_pointer_closure(), NULL);
646 ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
647 FlatProfiler::oops_do(adjust_root_pointer_closure());
648 Management::oops_do(adjust_root_pointer_closure());
649 JvmtiExport::oops_do(adjust_root_pointer_closure());
650 // SO_AllClasses
651 SystemDictionary::oops_do(adjust_root_pointer_closure());
652 vmSymbols::oops_do(adjust_root_pointer_closure());
653 //CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure());
654
655 // Now adjust pointers in remaining weak roots. (All of which should
656 // have been cleared if they pointed to non-surviving objects.)
657 // Global (weak) JNI handles
658 JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
659
660 CodeCache::oops_do(adjust_pointer_closure());
661 SymbolTable::oops_do(adjust_root_pointer_closure());
662 StringTable::oops_do(adjust_root_pointer_closure());
663 ref_processor()->weak_oops_do(adjust_root_pointer_closure());
664 PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure());
665
666 adjust_marks();
667
668 young_gen->adjust_pointers();
669 old_gen->adjust_pointers();
670 perm_gen->adjust_pointers();
671 }
672
673 void PSMarkSweep::mark_sweep_phase4() {
674 EventMark m("4 compact heap");
675 TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty);
676 trace("4");
677
678 // All pointers are now adjusted, move objects accordingly
679
680 // It is imperative that we traverse perm_gen first in phase4. All
681 // classes must be allocated earlier than their instances, and traversing
682 // perm_gen first makes sure that all klassOops have moved to their new
683 // location before any instance does a dispatch through it's klass!
684 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
685 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
686
687 PSYoungGen* young_gen = heap->young_gen();
688 PSOldGen* old_gen = heap->old_gen();
689 PSPermGen* perm_gen = heap->perm_gen();
690
691 perm_gen->compact();
692 old_gen->compact();
693 young_gen->compact();
694 }
695
696 jlong PSMarkSweep::millis_since_last_gc() {
697 jlong ret_val = os::javaTimeMillis() - _time_of_last_gc;
698 // XXX See note in genCollectedHeap::millis_since_last_gc().
699 if (ret_val < 0) {
700 NOT_PRODUCT(warning("time warp: %d", ret_val);)
701 return 0;
702 }
703 return ret_val;
704 }
705
706 void PSMarkSweep::reset_millis_since_last_gc() {
707 _time_of_last_gc = os::javaTimeMillis();
708 }