Thu, 12 Jun 2008 13:50:55 -0700
Merge
1 /*
2 * Copyright 2000-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 # include "incls/_precompiled.incl"
26 # include "incls/_genCollectedHeap.cpp.incl"
28 GenCollectedHeap* GenCollectedHeap::_gch;
29 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
31 // The set of potentially parallel tasks in strong root scanning.
32 enum GCH_process_strong_roots_tasks {
33 // We probably want to parallelize both of these internally, but for now...
34 GCH_PS_younger_gens,
35 // Leave this one last.
36 GCH_PS_NumElements
37 };
39 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
40 SharedHeap(policy),
41 _gen_policy(policy),
42 _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
43 _full_collections_completed(0)
44 {
45 if (_gen_process_strong_tasks == NULL ||
46 !_gen_process_strong_tasks->valid()) {
47 vm_exit_during_initialization("Failed necessary allocation.");
48 }
49 assert(policy != NULL, "Sanity check");
50 _preloading_shared_classes = false;
51 }
53 jint GenCollectedHeap::initialize() {
54 int i;
55 _n_gens = gen_policy()->number_of_generations();
57 // While there are no constraints in the GC code that HeapWordSize
58 // be any particular value, there are multiple other areas in the
59 // system which believe this to be true (e.g. oop->object_size in some
60 // cases incorrectly returns the size in wordSize units rather than
61 // HeapWordSize).
62 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
64 // The heap must be at least as aligned as generations.
65 size_t alignment = Generation::GenGrain;
67 _gen_specs = gen_policy()->generations();
68 PermanentGenerationSpec *perm_gen_spec =
69 collector_policy()->permanent_generation();
71 // Make sure the sizes are all aligned.
72 for (i = 0; i < _n_gens; i++) {
73 _gen_specs[i]->align(alignment);
74 }
75 perm_gen_spec->align(alignment);
77 // If we are dumping the heap, then allocate a wasted block of address
78 // space in order to push the heap to a lower address. This extra
79 // address range allows for other (or larger) libraries to be loaded
80 // without them occupying the space required for the shared spaces.
82 if (DumpSharedSpaces) {
83 uintx reserved = 0;
84 uintx block_size = 64*1024*1024;
85 while (reserved < SharedDummyBlockSize) {
86 char* dummy = os::reserve_memory(block_size);
87 reserved += block_size;
88 }
89 }
91 // Allocate space for the heap.
93 char* heap_address;
94 size_t total_reserved = 0;
95 int n_covered_regions = 0;
96 ReservedSpace heap_rs(0);
98 heap_address = allocate(alignment, perm_gen_spec, &total_reserved,
99 &n_covered_regions, &heap_rs);
101 if (UseSharedSpaces) {
102 if (!heap_rs.is_reserved() || heap_address != heap_rs.base()) {
103 if (heap_rs.is_reserved()) {
104 heap_rs.release();
105 }
106 FileMapInfo* mapinfo = FileMapInfo::current_info();
107 mapinfo->fail_continue("Unable to reserve shared region.");
108 allocate(alignment, perm_gen_spec, &total_reserved, &n_covered_regions,
109 &heap_rs);
110 }
111 }
113 if (!heap_rs.is_reserved()) {
114 vm_shutdown_during_initialization(
115 "Could not reserve enough space for object heap");
116 return JNI_ENOMEM;
117 }
119 _reserved = MemRegion((HeapWord*)heap_rs.base(),
120 (HeapWord*)(heap_rs.base() + heap_rs.size()));
122 // It is important to do this in a way such that concurrent readers can't
123 // temporarily think somethings in the heap. (Seen this happen in asserts.)
124 _reserved.set_word_size(0);
125 _reserved.set_start((HeapWord*)heap_rs.base());
126 size_t actual_heap_size = heap_rs.size() - perm_gen_spec->misc_data_size()
127 - perm_gen_spec->misc_code_size();
128 _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
130 _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
131 set_barrier_set(rem_set()->bs());
132 _gch = this;
134 for (i = 0; i < _n_gens; i++) {
135 ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(),
136 UseSharedSpaces, UseSharedSpaces);
137 _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
138 heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
139 }
140 _perm_gen = perm_gen_spec->init(heap_rs, PermSize, rem_set());
142 clear_incremental_collection_will_fail();
143 clear_last_incremental_collection_failed();
145 #ifndef SERIALGC
146 // If we are running CMS, create the collector responsible
147 // for collecting the CMS generations.
148 if (collector_policy()->is_concurrent_mark_sweep_policy()) {
149 bool success = create_cms_collector();
150 if (!success) return JNI_ENOMEM;
151 }
152 #endif // SERIALGC
154 return JNI_OK;
155 }
158 char* GenCollectedHeap::allocate(size_t alignment,
159 PermanentGenerationSpec* perm_gen_spec,
160 size_t* _total_reserved,
161 int* _n_covered_regions,
162 ReservedSpace* heap_rs){
163 const char overflow_msg[] = "The size of the object heap + VM data exceeds "
164 "the maximum representable size";
166 // Now figure out the total size.
167 size_t total_reserved = 0;
168 int n_covered_regions = 0;
169 const size_t pageSize = UseLargePages ?
170 os::large_page_size() : os::vm_page_size();
172 for (int i = 0; i < _n_gens; i++) {
173 total_reserved += _gen_specs[i]->max_size();
174 if (total_reserved < _gen_specs[i]->max_size()) {
175 vm_exit_during_initialization(overflow_msg);
176 }
177 n_covered_regions += _gen_specs[i]->n_covered_regions();
178 }
179 assert(total_reserved % pageSize == 0, "Gen size");
180 total_reserved += perm_gen_spec->max_size();
181 assert(total_reserved % pageSize == 0, "Perm Gen size");
183 if (total_reserved < perm_gen_spec->max_size()) {
184 vm_exit_during_initialization(overflow_msg);
185 }
186 n_covered_regions += perm_gen_spec->n_covered_regions();
188 // Add the size of the data area which shares the same reserved area
189 // as the heap, but which is not actually part of the heap.
190 size_t s = perm_gen_spec->misc_data_size() + perm_gen_spec->misc_code_size();
192 total_reserved += s;
193 if (total_reserved < s) {
194 vm_exit_during_initialization(overflow_msg);
195 }
197 if (UseLargePages) {
198 assert(total_reserved != 0, "total_reserved cannot be 0");
199 total_reserved = round_to(total_reserved, os::large_page_size());
200 if (total_reserved < os::large_page_size()) {
201 vm_exit_during_initialization(overflow_msg);
202 }
203 }
205 // Calculate the address at which the heap must reside in order for
206 // the shared data to be at the required address.
208 char* heap_address;
209 if (UseSharedSpaces) {
211 // Calculate the address of the first word beyond the heap.
212 FileMapInfo* mapinfo = FileMapInfo::current_info();
213 int lr = CompactingPermGenGen::n_regions - 1;
214 size_t capacity = align_size_up(mapinfo->space_capacity(lr), alignment);
215 heap_address = mapinfo->region_base(lr) + capacity;
217 // Calculate the address of the first word of the heap.
218 heap_address -= total_reserved;
219 } else {
220 heap_address = NULL; // any address will do.
221 }
223 *_total_reserved = total_reserved;
224 *_n_covered_regions = n_covered_regions;
225 *heap_rs = ReservedSpace(total_reserved, alignment,
226 UseLargePages, heap_address);
228 return heap_address;
229 }
232 void GenCollectedHeap::post_initialize() {
233 SharedHeap::post_initialize();
234 TwoGenerationCollectorPolicy *policy =
235 (TwoGenerationCollectorPolicy *)collector_policy();
236 guarantee(policy->is_two_generation_policy(), "Illegal policy type");
237 DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
238 assert(def_new_gen->kind() == Generation::DefNew ||
239 def_new_gen->kind() == Generation::ParNew ||
240 def_new_gen->kind() == Generation::ASParNew,
241 "Wrong generation kind");
243 Generation* old_gen = get_gen(1);
244 assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
245 old_gen->kind() == Generation::ASConcurrentMarkSweep ||
246 old_gen->kind() == Generation::MarkSweepCompact,
247 "Wrong generation kind");
249 policy->initialize_size_policy(def_new_gen->eden()->capacity(),
250 old_gen->capacity(),
251 def_new_gen->from()->capacity());
252 policy->initialize_gc_policy_counters();
253 }
255 void GenCollectedHeap::ref_processing_init() {
256 SharedHeap::ref_processing_init();
257 for (int i = 0; i < _n_gens; i++) {
258 _gens[i]->ref_processor_init();
259 }
260 }
262 size_t GenCollectedHeap::capacity() const {
263 size_t res = 0;
264 for (int i = 0; i < _n_gens; i++) {
265 res += _gens[i]->capacity();
266 }
267 return res;
268 }
270 size_t GenCollectedHeap::used() const {
271 size_t res = 0;
272 for (int i = 0; i < _n_gens; i++) {
273 res += _gens[i]->used();
274 }
275 return res;
276 }
278 // Save the "used_region" for generations level and lower,
279 // and, if perm is true, for perm gen.
280 void GenCollectedHeap::save_used_regions(int level, bool perm) {
281 assert(level < _n_gens, "Illegal level parameter");
282 for (int i = level; i >= 0; i--) {
283 _gens[i]->save_used_region();
284 }
285 if (perm) {
286 perm_gen()->save_used_region();
287 }
288 }
290 size_t GenCollectedHeap::max_capacity() const {
291 size_t res = 0;
292 for (int i = 0; i < _n_gens; i++) {
293 res += _gens[i]->max_capacity();
294 }
295 return res;
296 }
298 // Update the _full_collections_completed counter
299 // at the end of a stop-world full GC.
300 unsigned int GenCollectedHeap::update_full_collections_completed() {
301 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
302 assert(_full_collections_completed <= _total_full_collections,
303 "Can't complete more collections than were started");
304 _full_collections_completed = _total_full_collections;
305 ml.notify_all();
306 return _full_collections_completed;
307 }
309 // Update the _full_collections_completed counter, as appropriate,
310 // at the end of a concurrent GC cycle. Note the conditional update
311 // below to allow this method to be called by a concurrent collector
312 // without synchronizing in any manner with the VM thread (which
313 // may already have initiated a STW full collection "concurrently").
314 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
315 MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
316 assert((_full_collections_completed <= _total_full_collections) &&
317 (count <= _total_full_collections),
318 "Can't complete more collections than were started");
319 if (count > _full_collections_completed) {
320 _full_collections_completed = count;
321 ml.notify_all();
322 }
323 return _full_collections_completed;
324 }
327 #ifndef PRODUCT
328 // Override of memory state checking method in CollectedHeap:
329 // Some collectors (CMS for example) can't have badHeapWordVal written
330 // in the first two words of an object. (For instance , in the case of
331 // CMS these words hold state used to synchronize between certain
332 // (concurrent) GC steps and direct allocating mutators.)
333 // The skip_header_HeapWords() method below, allows us to skip
334 // over the requisite number of HeapWord's. Note that (for
335 // generational collectors) this means that those many words are
336 // skipped in each object, irrespective of the generation in which
337 // that object lives. The resultant loss of precision seems to be
338 // harmless and the pain of avoiding that imprecision appears somewhat
339 // higher than we are prepared to pay for such rudimentary debugging
340 // support.
341 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
342 size_t size) {
343 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
344 // We are asked to check a size in HeapWords,
345 // but the memory is mangled in juint words.
346 juint* start = (juint*) (addr + skip_header_HeapWords());
347 juint* end = (juint*) (addr + size);
348 for (juint* slot = start; slot < end; slot += 1) {
349 assert(*slot == badHeapWordVal,
350 "Found non badHeapWordValue in pre-allocation check");
351 }
352 }
353 }
354 #endif
356 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
357 bool is_tlab,
358 bool first_only) {
359 HeapWord* res;
360 for (int i = 0; i < _n_gens; i++) {
361 if (_gens[i]->should_allocate(size, is_tlab)) {
362 res = _gens[i]->allocate(size, is_tlab);
363 if (res != NULL) return res;
364 else if (first_only) break;
365 }
366 }
367 // Otherwise...
368 return NULL;
369 }
371 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
372 bool is_large_noref,
373 bool is_tlab,
374 bool* gc_overhead_limit_was_exceeded) {
375 return collector_policy()->mem_allocate_work(size,
376 is_tlab,
377 gc_overhead_limit_was_exceeded);
378 }
380 bool GenCollectedHeap::must_clear_all_soft_refs() {
381 return _gc_cause == GCCause::_last_ditch_collection;
382 }
384 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
385 return (cause == GCCause::_java_lang_system_gc ||
386 cause == GCCause::_gc_locker) &&
387 UseConcMarkSweepGC && ExplicitGCInvokesConcurrent;
388 }
390 void GenCollectedHeap::do_collection(bool full,
391 bool clear_all_soft_refs,
392 size_t size,
393 bool is_tlab,
394 int max_level) {
395 bool prepared_for_verification = false;
396 ResourceMark rm;
397 DEBUG_ONLY(Thread* my_thread = Thread::current();)
399 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
400 assert(my_thread->is_VM_thread() ||
401 my_thread->is_ConcurrentGC_thread(),
402 "incorrect thread type capability");
403 assert(Heap_lock->is_locked(), "the requesting thread should have the Heap_lock");
404 guarantee(!is_gc_active(), "collection is not reentrant");
405 assert(max_level < n_gens(), "sanity check");
407 if (GC_locker::check_active_before_gc()) {
408 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
409 }
411 const size_t perm_prev_used = perm_gen()->used();
413 if (PrintHeapAtGC) {
414 Universe::print_heap_before_gc();
415 if (Verbose) {
416 gclog_or_tty->print_cr("GC Cause: %s", GCCause::to_string(gc_cause()));
417 }
418 }
420 {
421 FlagSetting fl(_is_gc_active, true);
423 bool complete = full && (max_level == (n_gens()-1));
424 const char* gc_cause_str = "GC ";
425 if (complete) {
426 GCCause::Cause cause = gc_cause();
427 if (cause == GCCause::_java_lang_system_gc) {
428 gc_cause_str = "Full GC (System) ";
429 } else {
430 gc_cause_str = "Full GC ";
431 }
432 }
433 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
434 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
435 TraceTime t(gc_cause_str, PrintGCDetails, false, gclog_or_tty);
437 gc_prologue(complete);
438 increment_total_collections(complete);
440 size_t gch_prev_used = used();
442 int starting_level = 0;
443 if (full) {
444 // Search for the oldest generation which will collect all younger
445 // generations, and start collection loop there.
446 for (int i = max_level; i >= 0; i--) {
447 if (_gens[i]->full_collects_younger_generations()) {
448 starting_level = i;
449 break;
450 }
451 }
452 }
454 bool must_restore_marks_for_biased_locking = false;
456 int max_level_collected = starting_level;
457 for (int i = starting_level; i <= max_level; i++) {
458 if (_gens[i]->should_collect(full, size, is_tlab)) {
459 // Timer for individual generations. Last argument is false: no CR
460 TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
461 TraceCollectorStats tcs(_gens[i]->counters());
462 TraceMemoryManagerStats tmms(_gens[i]->kind());
464 size_t prev_used = _gens[i]->used();
465 _gens[i]->stat_record()->invocations++;
466 _gens[i]->stat_record()->accumulated_time.start();
468 if (PrintGC && Verbose) {
469 gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
470 i,
471 _gens[i]->stat_record()->invocations,
472 size*HeapWordSize);
473 }
475 if (VerifyBeforeGC && i >= VerifyGCLevel &&
476 total_collections() >= VerifyGCStartAt) {
477 HandleMark hm; // Discard invalid handles created during verification
478 if (!prepared_for_verification) {
479 prepare_for_verify();
480 prepared_for_verification = true;
481 }
482 gclog_or_tty->print(" VerifyBeforeGC:");
483 Universe::verify(true);
484 }
485 COMPILER2_PRESENT(DerivedPointerTable::clear());
487 if (!must_restore_marks_for_biased_locking &&
488 _gens[i]->performs_in_place_marking()) {
489 // We perform this mark word preservation work lazily
490 // because it's only at this point that we know whether we
491 // absolutely have to do it; we want to avoid doing it for
492 // scavenge-only collections where it's unnecessary
493 must_restore_marks_for_biased_locking = true;
494 BiasedLocking::preserve_marks();
495 }
497 // Do collection work
498 {
499 // Note on ref discovery: For what appear to be historical reasons,
500 // GCH enables and disabled (by enqueing) refs discovery.
501 // In the future this should be moved into the generation's
502 // collect method so that ref discovery and enqueueing concerns
503 // are local to a generation. The collect method could return
504 // an appropriate indication in the case that notification on
505 // the ref lock was needed. This will make the treatment of
506 // weak refs more uniform (and indeed remove such concerns
507 // from GCH). XXX
509 HandleMark hm; // Discard invalid handles created during gc
510 save_marks(); // save marks for all gens
511 // We want to discover references, but not process them yet.
512 // This mode is disabled in process_discovered_references if the
513 // generation does some collection work, or in
514 // enqueue_discovered_references if the generation returns
515 // without doing any work.
516 ReferenceProcessor* rp = _gens[i]->ref_processor();
517 // If the discovery of ("weak") refs in this generation is
518 // atomic wrt other collectors in this configuration, we
519 // are guaranteed to have empty discovered ref lists.
520 if (rp->discovery_is_atomic()) {
521 rp->verify_no_references_recorded();
522 rp->enable_discovery();
523 } else {
524 // collect() will enable discovery as appropriate
525 }
526 _gens[i]->collect(full, clear_all_soft_refs, size, is_tlab);
527 if (!rp->enqueuing_is_done()) {
528 rp->enqueue_discovered_references();
529 } else {
530 rp->set_enqueuing_is_done(false);
531 }
532 rp->verify_no_references_recorded();
533 }
534 max_level_collected = i;
536 // Determine if allocation request was met.
537 if (size > 0) {
538 if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
539 if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
540 size = 0;
541 }
542 }
543 }
545 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
547 _gens[i]->stat_record()->accumulated_time.stop();
549 update_gc_stats(i, full);
551 if (VerifyAfterGC && i >= VerifyGCLevel &&
552 total_collections() >= VerifyGCStartAt) {
553 HandleMark hm; // Discard invalid handles created during verification
554 gclog_or_tty->print(" VerifyAfterGC:");
555 Universe::verify(false);
556 }
558 if (PrintGCDetails) {
559 gclog_or_tty->print(":");
560 _gens[i]->print_heap_change(prev_used);
561 }
562 }
563 }
565 // Update "complete" boolean wrt what actually transpired --
566 // for instance, a promotion failure could have led to
567 // a whole heap collection.
568 complete = complete || (max_level_collected == n_gens() - 1);
570 if (PrintGCDetails) {
571 print_heap_change(gch_prev_used);
573 // Print perm gen info for full GC with PrintGCDetails flag.
574 if (complete) {
575 print_perm_heap_change(perm_prev_used);
576 }
577 }
579 for (int j = max_level_collected; j >= 0; j -= 1) {
580 // Adjust generation sizes.
581 _gens[j]->compute_new_size();
582 }
584 if (complete) {
585 // Ask the permanent generation to adjust size for full collections
586 perm()->compute_new_size();
587 update_full_collections_completed();
588 }
590 // Track memory usage and detect low memory after GC finishes
591 MemoryService::track_memory_usage();
593 gc_epilogue(complete);
595 if (must_restore_marks_for_biased_locking) {
596 BiasedLocking::restore_marks();
597 }
598 }
600 AdaptiveSizePolicy* sp = gen_policy()->size_policy();
601 AdaptiveSizePolicyOutput(sp, total_collections());
603 if (PrintHeapAtGC) {
604 Universe::print_heap_after_gc();
605 }
607 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
608 tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
609 vm_exit(-1);
610 }
611 }
613 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
614 return collector_policy()->satisfy_failed_allocation(size, is_tlab);
615 }
617 void GenCollectedHeap::set_par_threads(int t) {
618 SharedHeap::set_par_threads(t);
619 _gen_process_strong_tasks->set_par_threads(t);
620 }
622 class AssertIsPermClosure: public OopClosure {
623 public:
624 void do_oop(oop* p) {
625 assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm.");
626 }
627 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
628 };
629 static AssertIsPermClosure assert_is_perm_closure;
631 void GenCollectedHeap::
632 gen_process_strong_roots(int level,
633 bool younger_gens_as_roots,
634 bool collecting_perm_gen,
635 SharedHeap::ScanningOption so,
636 OopsInGenClosure* older_gens,
637 OopsInGenClosure* not_older_gens) {
638 // General strong roots.
639 SharedHeap::process_strong_roots(collecting_perm_gen, so,
640 not_older_gens, older_gens);
642 if (younger_gens_as_roots) {
643 if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
644 for (int i = 0; i < level; i++) {
645 not_older_gens->set_generation(_gens[i]);
646 _gens[i]->oop_iterate(not_older_gens);
647 }
648 not_older_gens->reset_generation();
649 }
650 }
651 // When collection is parallel, all threads get to cooperate to do
652 // older-gen scanning.
653 for (int i = level+1; i < _n_gens; i++) {
654 older_gens->set_generation(_gens[i]);
655 rem_set()->younger_refs_iterate(_gens[i], older_gens);
656 older_gens->reset_generation();
657 }
659 _gen_process_strong_tasks->all_tasks_completed();
660 }
662 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
663 OopClosure* non_root_closure) {
664 SharedHeap::process_weak_roots(root_closure, non_root_closure);
665 // "Local" "weak" refs
666 for (int i = 0; i < _n_gens; i++) {
667 _gens[i]->ref_processor()->weak_oops_do(root_closure);
668 }
669 }
671 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix) \
672 void GenCollectedHeap:: \
673 oop_since_save_marks_iterate(int level, \
674 OopClosureType* cur, \
675 OopClosureType* older) { \
676 _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur); \
677 for (int i = level+1; i < n_gens(); i++) { \
678 _gens[i]->oop_since_save_marks_iterate##nv_suffix(older); \
679 } \
680 perm_gen()->oop_since_save_marks_iterate##nv_suffix(older); \
681 }
683 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
685 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
687 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
688 for (int i = level; i < _n_gens; i++) {
689 if (!_gens[i]->no_allocs_since_save_marks()) return false;
690 }
691 return perm_gen()->no_allocs_since_save_marks();
692 }
694 bool GenCollectedHeap::supports_inline_contig_alloc() const {
695 return _gens[0]->supports_inline_contig_alloc();
696 }
698 HeapWord** GenCollectedHeap::top_addr() const {
699 return _gens[0]->top_addr();
700 }
702 HeapWord** GenCollectedHeap::end_addr() const {
703 return _gens[0]->end_addr();
704 }
706 size_t GenCollectedHeap::unsafe_max_alloc() {
707 return _gens[0]->unsafe_max_alloc_nogc();
708 }
710 // public collection interfaces
712 void GenCollectedHeap::collect(GCCause::Cause cause) {
713 if (should_do_concurrent_full_gc(cause)) {
714 #ifndef SERIALGC
715 // mostly concurrent full collection
716 collect_mostly_concurrent(cause);
717 #else // SERIALGC
718 ShouldNotReachHere();
719 #endif // SERIALGC
720 } else {
721 #ifdef ASSERT
722 if (cause == GCCause::_scavenge_alot) {
723 // minor collection only
724 collect(cause, 0);
725 } else {
726 // Stop-the-world full collection
727 collect(cause, n_gens() - 1);
728 }
729 #else
730 // Stop-the-world full collection
731 collect(cause, n_gens() - 1);
732 #endif
733 }
734 }
736 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
737 // The caller doesn't have the Heap_lock
738 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
739 MutexLocker ml(Heap_lock);
740 collect_locked(cause, max_level);
741 }
743 // This interface assumes that it's being called by the
744 // vm thread. It collects the heap assuming that the
745 // heap lock is already held and that we are executing in
746 // the context of the vm thread.
747 void GenCollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
748 assert(Thread::current()->is_VM_thread(), "Precondition#1");
749 assert(Heap_lock->is_locked(), "Precondition#2");
750 GCCauseSetter gcs(this, cause);
751 switch (cause) {
752 case GCCause::_heap_inspection:
753 case GCCause::_heap_dump: {
754 HandleMark hm;
755 do_full_collection(false, // don't clear all soft refs
756 n_gens() - 1);
757 break;
758 }
759 default: // XXX FIX ME
760 ShouldNotReachHere(); // Unexpected use of this function
761 }
762 }
764 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
765 // The caller has the Heap_lock
766 assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
767 collect_locked(cause, n_gens() - 1);
768 }
770 // this is the private collection interface
771 // The Heap_lock is expected to be held on entry.
773 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
774 if (_preloading_shared_classes) {
775 warning("\nThe permanent generation is not large enough to preload "
776 "requested classes.\nUse -XX:PermSize= to increase the initial "
777 "size of the permanent generation.\n");
778 vm_exit(2);
779 }
780 // Read the GC count while holding the Heap_lock
781 unsigned int gc_count_before = total_collections();
782 unsigned int full_gc_count_before = total_full_collections();
783 {
784 MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
785 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
786 cause, max_level);
787 VMThread::execute(&op);
788 }
789 }
791 #ifndef SERIALGC
792 bool GenCollectedHeap::create_cms_collector() {
794 assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
795 (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)) &&
796 _perm_gen->as_gen()->kind() == Generation::ConcurrentMarkSweep,
797 "Unexpected generation kinds");
798 // Skip two header words in the block content verification
799 NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
800 CMSCollector* collector = new CMSCollector(
801 (ConcurrentMarkSweepGeneration*)_gens[1],
802 (ConcurrentMarkSweepGeneration*)_perm_gen->as_gen(),
803 _rem_set->as_CardTableRS(),
804 (ConcurrentMarkSweepPolicy*) collector_policy());
806 if (collector == NULL || !collector->completed_initialization()) {
807 if (collector) {
808 delete collector; // Be nice in embedded situation
809 }
810 vm_shutdown_during_initialization("Could not create CMS collector");
811 return false;
812 }
813 return true; // success
814 }
816 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
817 assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
819 MutexLocker ml(Heap_lock);
820 // Read the GC counts while holding the Heap_lock
821 unsigned int full_gc_count_before = total_full_collections();
822 unsigned int gc_count_before = total_collections();
823 {
824 MutexUnlocker mu(Heap_lock);
825 VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
826 VMThread::execute(&op);
827 }
828 }
829 #endif // SERIALGC
832 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
833 int max_level) {
834 int local_max_level;
835 if (!incremental_collection_will_fail() &&
836 gc_cause() == GCCause::_gc_locker) {
837 local_max_level = 0;
838 } else {
839 local_max_level = max_level;
840 }
842 do_collection(true /* full */,
843 clear_all_soft_refs /* clear_all_soft_refs */,
844 0 /* size */,
845 false /* is_tlab */,
846 local_max_level /* max_level */);
847 // Hack XXX FIX ME !!!
848 // A scavenge may not have been attempted, or may have
849 // been attempted and failed, because the old gen was too full
850 if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
851 incremental_collection_will_fail()) {
852 if (PrintGCDetails) {
853 gclog_or_tty->print_cr("GC locker: Trying a full collection "
854 "because scavenge failed");
855 }
856 // This time allow the old gen to be collected as well
857 do_collection(true /* full */,
858 clear_all_soft_refs /* clear_all_soft_refs */,
859 0 /* size */,
860 false /* is_tlab */,
861 n_gens() - 1 /* max_level */);
862 }
863 }
865 // Returns "TRUE" iff "p" points into the allocated area of the heap.
866 bool GenCollectedHeap::is_in(const void* p) const {
867 #ifndef ASSERT
868 guarantee(VerifyBeforeGC ||
869 VerifyDuringGC ||
870 VerifyBeforeExit ||
871 VerifyAfterGC, "too expensive");
872 #endif
873 // This might be sped up with a cache of the last generation that
874 // answered yes.
875 for (int i = 0; i < _n_gens; i++) {
876 if (_gens[i]->is_in(p)) return true;
877 }
878 if (_perm_gen->as_gen()->is_in(p)) return true;
879 // Otherwise...
880 return false;
881 }
883 // Returns "TRUE" iff "p" points into the allocated area of the heap.
884 bool GenCollectedHeap::is_in_youngest(void* p) {
885 return _gens[0]->is_in(p);
886 }
888 void GenCollectedHeap::oop_iterate(OopClosure* cl) {
889 for (int i = 0; i < _n_gens; i++) {
890 _gens[i]->oop_iterate(cl);
891 }
892 }
894 void GenCollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl) {
895 for (int i = 0; i < _n_gens; i++) {
896 _gens[i]->oop_iterate(mr, cl);
897 }
898 }
900 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
901 for (int i = 0; i < _n_gens; i++) {
902 _gens[i]->object_iterate(cl);
903 }
904 perm_gen()->object_iterate(cl);
905 }
907 void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
908 for (int i = 0; i < _n_gens; i++) {
909 _gens[i]->object_iterate_since_last_GC(cl);
910 }
911 }
913 Space* GenCollectedHeap::space_containing(const void* addr) const {
914 for (int i = 0; i < _n_gens; i++) {
915 Space* res = _gens[i]->space_containing(addr);
916 if (res != NULL) return res;
917 }
918 Space* res = perm_gen()->space_containing(addr);
919 if (res != NULL) return res;
920 // Otherwise...
921 assert(false, "Could not find containing space");
922 return NULL;
923 }
926 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
927 assert(is_in_reserved(addr), "block_start of address outside of heap");
928 for (int i = 0; i < _n_gens; i++) {
929 if (_gens[i]->is_in_reserved(addr)) {
930 assert(_gens[i]->is_in(addr),
931 "addr should be in allocated part of generation");
932 return _gens[i]->block_start(addr);
933 }
934 }
935 if (perm_gen()->is_in_reserved(addr)) {
936 assert(perm_gen()->is_in(addr),
937 "addr should be in allocated part of perm gen");
938 return perm_gen()->block_start(addr);
939 }
940 assert(false, "Some generation should contain the address");
941 return NULL;
942 }
944 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
945 assert(is_in_reserved(addr), "block_size of address outside of heap");
946 for (int i = 0; i < _n_gens; i++) {
947 if (_gens[i]->is_in_reserved(addr)) {
948 assert(_gens[i]->is_in(addr),
949 "addr should be in allocated part of generation");
950 return _gens[i]->block_size(addr);
951 }
952 }
953 if (perm_gen()->is_in_reserved(addr)) {
954 assert(perm_gen()->is_in(addr),
955 "addr should be in allocated part of perm gen");
956 return perm_gen()->block_size(addr);
957 }
958 assert(false, "Some generation should contain the address");
959 return 0;
960 }
962 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
963 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
964 assert(block_start(addr) == addr, "addr must be a block start");
965 for (int i = 0; i < _n_gens; i++) {
966 if (_gens[i]->is_in_reserved(addr)) {
967 return _gens[i]->block_is_obj(addr);
968 }
969 }
970 if (perm_gen()->is_in_reserved(addr)) {
971 return perm_gen()->block_is_obj(addr);
972 }
973 assert(false, "Some generation should contain the address");
974 return false;
975 }
977 bool GenCollectedHeap::supports_tlab_allocation() const {
978 for (int i = 0; i < _n_gens; i += 1) {
979 if (_gens[i]->supports_tlab_allocation()) {
980 return true;
981 }
982 }
983 return false;
984 }
986 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
987 size_t result = 0;
988 for (int i = 0; i < _n_gens; i += 1) {
989 if (_gens[i]->supports_tlab_allocation()) {
990 result += _gens[i]->tlab_capacity();
991 }
992 }
993 return result;
994 }
996 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
997 size_t result = 0;
998 for (int i = 0; i < _n_gens; i += 1) {
999 if (_gens[i]->supports_tlab_allocation()) {
1000 result += _gens[i]->unsafe_max_tlab_alloc();
1001 }
1002 }
1003 return result;
1004 }
1006 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1007 bool gc_overhead_limit_was_exceeded;
1008 HeapWord* result = mem_allocate(size /* size */,
1009 false /* is_large_noref */,
1010 true /* is_tlab */,
1011 &gc_overhead_limit_was_exceeded);
1012 return result;
1013 }
1015 // Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size
1016 // from the list headed by "*prev_ptr".
1017 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1018 bool first = true;
1019 size_t min_size = 0; // "first" makes this conceptually infinite.
1020 ScratchBlock **smallest_ptr, *smallest;
1021 ScratchBlock *cur = *prev_ptr;
1022 while (cur) {
1023 assert(*prev_ptr == cur, "just checking");
1024 if (first || cur->num_words < min_size) {
1025 smallest_ptr = prev_ptr;
1026 smallest = cur;
1027 min_size = smallest->num_words;
1028 first = false;
1029 }
1030 prev_ptr = &cur->next;
1031 cur = cur->next;
1032 }
1033 smallest = *smallest_ptr;
1034 *smallest_ptr = smallest->next;
1035 return smallest;
1036 }
1038 // Sort the scratch block list headed by res into decreasing size order,
1039 // and set "res" to the result.
1040 static void sort_scratch_list(ScratchBlock*& list) {
1041 ScratchBlock* sorted = NULL;
1042 ScratchBlock* unsorted = list;
1043 while (unsorted) {
1044 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1045 smallest->next = sorted;
1046 sorted = smallest;
1047 }
1048 list = sorted;
1049 }
1051 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1052 size_t max_alloc_words) {
1053 ScratchBlock* res = NULL;
1054 for (int i = 0; i < _n_gens; i++) {
1055 _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1056 }
1057 sort_scratch_list(res);
1058 return res;
1059 }
1061 size_t GenCollectedHeap::large_typearray_limit() {
1062 return gen_policy()->large_typearray_limit();
1063 }
1065 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1066 void do_generation(Generation* gen) {
1067 gen->prepare_for_verify();
1068 }
1069 };
1071 void GenCollectedHeap::prepare_for_verify() {
1072 ensure_parsability(false); // no need to retire TLABs
1073 GenPrepareForVerifyClosure blk;
1074 generation_iterate(&blk, false);
1075 perm_gen()->prepare_for_verify();
1076 }
1079 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1080 bool old_to_young) {
1081 if (old_to_young) {
1082 for (int i = _n_gens-1; i >= 0; i--) {
1083 cl->do_generation(_gens[i]);
1084 }
1085 } else {
1086 for (int i = 0; i < _n_gens; i++) {
1087 cl->do_generation(_gens[i]);
1088 }
1089 }
1090 }
1092 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1093 for (int i = 0; i < _n_gens; i++) {
1094 _gens[i]->space_iterate(cl, true);
1095 }
1096 perm_gen()->space_iterate(cl, true);
1097 }
1099 bool GenCollectedHeap::is_maximal_no_gc() const {
1100 for (int i = 0; i < _n_gens; i++) { // skip perm gen
1101 if (!_gens[i]->is_maximal_no_gc()) {
1102 return false;
1103 }
1104 }
1105 return true;
1106 }
1108 void GenCollectedHeap::save_marks() {
1109 for (int i = 0; i < _n_gens; i++) {
1110 _gens[i]->save_marks();
1111 }
1112 perm_gen()->save_marks();
1113 }
1115 void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
1116 for (int i = 0; i <= collectedGen; i++) {
1117 _gens[i]->compute_new_size();
1118 }
1119 }
1121 GenCollectedHeap* GenCollectedHeap::heap() {
1122 assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1123 assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1124 return _gch;
1125 }
1128 void GenCollectedHeap::prepare_for_compaction() {
1129 Generation* scanning_gen = _gens[_n_gens-1];
1130 // Start by compacting into same gen.
1131 CompactPoint cp(scanning_gen, NULL, NULL);
1132 while (scanning_gen != NULL) {
1133 scanning_gen->prepare_for_compaction(&cp);
1134 scanning_gen = prev_gen(scanning_gen);
1135 }
1136 }
1138 GCStats* GenCollectedHeap::gc_stats(int level) const {
1139 return _gens[level]->gc_stats();
1140 }
1142 void GenCollectedHeap::verify(bool allow_dirty, bool silent) {
1143 if (!silent) {
1144 gclog_or_tty->print("permgen ");
1145 }
1146 perm_gen()->verify(allow_dirty);
1147 for (int i = _n_gens-1; i >= 0; i--) {
1148 Generation* g = _gens[i];
1149 if (!silent) {
1150 gclog_or_tty->print(g->name());
1151 gclog_or_tty->print(" ");
1152 }
1153 g->verify(allow_dirty);
1154 }
1155 if (!silent) {
1156 gclog_or_tty->print("remset ");
1157 }
1158 rem_set()->verify();
1159 if (!silent) {
1160 gclog_or_tty->print("ref_proc ");
1161 }
1162 ReferenceProcessor::verify();
1163 }
1165 void GenCollectedHeap::print() const { print_on(tty); }
1166 void GenCollectedHeap::print_on(outputStream* st) const {
1167 for (int i = 0; i < _n_gens; i++) {
1168 _gens[i]->print_on(st);
1169 }
1170 perm_gen()->print_on(st);
1171 }
1173 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1174 if (workers() != NULL) {
1175 workers()->threads_do(tc);
1176 }
1177 #ifndef SERIALGC
1178 if (UseConcMarkSweepGC) {
1179 ConcurrentMarkSweepThread::threads_do(tc);
1180 }
1181 #endif // SERIALGC
1182 }
1184 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1185 #ifndef SERIALGC
1186 if (UseParNewGC) {
1187 workers()->print_worker_threads_on(st);
1188 }
1189 if (UseConcMarkSweepGC) {
1190 ConcurrentMarkSweepThread::print_all_on(st);
1191 }
1192 #endif // SERIALGC
1193 }
1195 void GenCollectedHeap::print_tracing_info() const {
1196 if (TraceGen0Time) {
1197 get_gen(0)->print_summary_info();
1198 }
1199 if (TraceGen1Time) {
1200 get_gen(1)->print_summary_info();
1201 }
1202 }
1204 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1205 if (PrintGCDetails && Verbose) {
1206 gclog_or_tty->print(" " SIZE_FORMAT
1207 "->" SIZE_FORMAT
1208 "(" SIZE_FORMAT ")",
1209 prev_used, used(), capacity());
1210 } else {
1211 gclog_or_tty->print(" " SIZE_FORMAT "K"
1212 "->" SIZE_FORMAT "K"
1213 "(" SIZE_FORMAT "K)",
1214 prev_used / K, used() / K, capacity() / K);
1215 }
1216 }
1218 //New method to print perm gen info with PrintGCDetails flag
1219 void GenCollectedHeap::print_perm_heap_change(size_t perm_prev_used) const {
1220 gclog_or_tty->print(", [%s :", perm_gen()->short_name());
1221 perm_gen()->print_heap_change(perm_prev_used);
1222 gclog_or_tty->print("]");
1223 }
1225 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1226 private:
1227 bool _full;
1228 public:
1229 void do_generation(Generation* gen) {
1230 gen->gc_prologue(_full);
1231 }
1232 GenGCPrologueClosure(bool full) : _full(full) {};
1233 };
1235 void GenCollectedHeap::gc_prologue(bool full) {
1236 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1238 always_do_update_barrier = false;
1239 // Fill TLAB's and such
1240 CollectedHeap::accumulate_statistics_all_tlabs();
1241 ensure_parsability(true); // retire TLABs
1243 // Call allocation profiler
1244 AllocationProfiler::iterate_since_last_gc();
1245 // Walk generations
1246 GenGCPrologueClosure blk(full);
1247 generation_iterate(&blk, false); // not old-to-young.
1248 perm_gen()->gc_prologue(full);
1249 };
1251 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1252 private:
1253 bool _full;
1254 public:
1255 void do_generation(Generation* gen) {
1256 gen->gc_epilogue(_full);
1257 }
1258 GenGCEpilogueClosure(bool full) : _full(full) {};
1259 };
1261 void GenCollectedHeap::gc_epilogue(bool full) {
1262 // Remember if a partial collection of the heap failed, and
1263 // we did a complete collection.
1264 if (full && incremental_collection_will_fail()) {
1265 set_last_incremental_collection_failed();
1266 } else {
1267 clear_last_incremental_collection_failed();
1268 }
1269 // Clear the flag, if set; the generation gc_epilogues will set the
1270 // flag again if the condition persists despite the collection.
1271 clear_incremental_collection_will_fail();
1273 #ifdef COMPILER2
1274 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1275 size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1276 guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1277 #endif /* COMPILER2 */
1279 resize_all_tlabs();
1281 GenGCEpilogueClosure blk(full);
1282 generation_iterate(&blk, false); // not old-to-young.
1283 perm_gen()->gc_epilogue(full);
1285 always_do_update_barrier = UseConcMarkSweepGC;
1286 };
1288 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1289 public:
1290 void do_generation(Generation* gen) {
1291 gen->ensure_parsability();
1292 }
1293 };
1295 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1296 CollectedHeap::ensure_parsability(retire_tlabs);
1297 GenEnsureParsabilityClosure ep_cl;
1298 generation_iterate(&ep_cl, false);
1299 perm_gen()->ensure_parsability();
1300 }
1302 oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
1303 oop obj,
1304 size_t obj_size) {
1305 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1306 HeapWord* result = NULL;
1308 // First give each higher generation a chance to allocate the promoted object.
1309 Generation* allocator = next_gen(gen);
1310 if (allocator != NULL) {
1311 do {
1312 result = allocator->allocate(obj_size, false);
1313 } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
1314 }
1316 if (result == NULL) {
1317 // Then give gen and higher generations a chance to expand and allocate the
1318 // object.
1319 do {
1320 result = gen->expand_and_allocate(obj_size, false);
1321 } while (result == NULL && (gen = next_gen(gen)) != NULL);
1322 }
1324 if (result != NULL) {
1325 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1326 }
1327 return oop(result);
1328 }
1330 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1331 jlong _time; // in ms
1332 jlong _now; // in ms
1334 public:
1335 GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1337 jlong time() { return _time; }
1339 void do_generation(Generation* gen) {
1340 _time = MIN2(_time, gen->time_of_last_gc(_now));
1341 }
1342 };
1344 jlong GenCollectedHeap::millis_since_last_gc() {
1345 jlong now = os::javaTimeMillis();
1346 GenTimeOfLastGCClosure tolgc_cl(now);
1347 // iterate over generations getting the oldest
1348 // time that a generation was collected
1349 generation_iterate(&tolgc_cl, false);
1350 tolgc_cl.do_generation(perm_gen());
1351 // XXX Despite the assert above, since javaTimeMillis()
1352 // doesnot guarantee monotonically increasing return
1353 // values (note, i didn't say "strictly monotonic"),
1354 // we need to guard against getting back a time
1355 // later than now. This should be fixed by basing
1356 // on someting like gethrtime() which guarantees
1357 // monotonicity. Note that cond_wait() is susceptible
1358 // to a similar problem, because its interface is
1359 // based on absolute time in the form of the
1360 // system time's notion of UCT. See also 4506635
1361 // for yet another problem of similar nature. XXX
1362 jlong retVal = now - tolgc_cl.time();
1363 if (retVal < 0) {
1364 NOT_PRODUCT(warning("time warp: %d", retVal);)
1365 return 0;
1366 }
1367 return retVal;
1368 }