void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
bool clear_all_softrefs) {
// Recursively traverse all live objects and mark them
EventMark m("1 mark object");
TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
GenMarkSweep::trace(" 1");
SharedHeap* sh = SharedHeap::heap();
sh->process_strong_roots(true, // activeate StrongRootsScope
true, // Collecting permanent generation.
SharedHeap::SO_SystemClasses,
&GenMarkSweep::follow_root_closure,
&GenMarkSweep::follow_code_root_closure,
&GenMarkSweep::follow_root_closure);
// Process reference objects found during marking
ReferenceProcessor* rp = GenMarkSweep::ref_processor();
rp->setup_policy(clear_all_softrefs);
rp->process_discovered_references(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
&GenMarkSweep::follow_stack_closure,
NULL);
// Follow system dictionary roots and unload classes
bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
assert(GenMarkSweep::_marking_stack.is_empty(),
"stack should be empty by now");
// Follow code cache roots (has to be done after system dictionary,
// assumes all live klasses are marked)
CodeCache::do_unloading(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
purged_class);
GenMarkSweep::follow_stack();
// Update subklass/sibling/implementor links of live klasses
GenMarkSweep::follow_weak_klass_links();
assert(GenMarkSweep::_marking_stack.is_empty(),
"stack should be empty by now");
// Visit memoized MDO's and clear any unmarked weak refs
GenMarkSweep::follow_mdo_weak_refs();
assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");
// Visit symbol and interned string tables and delete unmarked oops
SymbolTable::unlink(&GenMarkSweep::is_alive);
StringTable::unlink(&GenMarkSweep::is_alive);
assert(GenMarkSweep::_marking_stack.is_empty(),
"stack should be empty by now");
}
void DefNewGeneration::collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_tlab) {
assert(full || size > 0, "otherwise we don't want to collect");
GenCollectedHeap* gch = GenCollectedHeap::heap();
_gc_timer->register_gc_start();
DefNewTracer gc_tracer;
gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
_next_gen = gch->next_gen(this);
// If the next generation is too full to accommodate promotion
// from this generation, pass on collection; let the next generation
// do it.
if (!collection_attempt_is_safe()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print(" :: Collection attempt not safe :: ");
}
gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
return;
}
assert(to()->is_empty(), "Else not collection_attempt_is_safe");
init_assuming_no_promotion_failure();
GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
// Capture heap used before collection (for printing).
size_t gch_prev_used = gch->used();
gch->trace_heap_before_gc(&gc_tracer);
SpecializationStats::clear();
// These can be shared for all code paths
IsAliveClosure is_alive(this);
ScanWeakRefClosure scan_weak_ref(this);
age_table()->clear();
to()->clear(SpaceDecorator::Mangle);
gch->rem_set()->prepare_for_younger_refs_iterate(false);
assert(gch->no_allocs_since_save_marks(0),
"save marks have not been newly set.");
// Not very pretty.
CollectorPolicy* cp = gch->collector_policy();
FastScanClosure fsc_with_no_gc_barrier(this, false);
FastScanClosure fsc_with_gc_barrier(this, true);
KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
gch->rem_set()->klass_rem_set());
set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
&fsc_with_no_gc_barrier,
&fsc_with_gc_barrier);
assert(gch->no_allocs_since_save_marks(0),
"save marks have not been newly set.");
int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
gch->gen_process_strong_roots(_level,
true, // Process younger gens, if any,
// as strong roots.
true, // activate StrongRootsScope
true, // is scavenging
SharedHeap::ScanningOption(so),
&fsc_with_no_gc_barrier,
true, // walk *all* scavengable nmethods
&fsc_with_gc_barrier,
&klass_scan_closure);
// "evacuate followers".
evacuate_followers.do_void();
FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
ReferenceProcessor* rp = ref_processor();
rp->setup_policy(clear_all_soft_refs);
const ReferenceProcessorStats& stats =
rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
NULL, _gc_timer);
gc_tracer.report_gc_reference_stats(stats);
if (!_promotion_failed) {
// Swap the survivor spaces.
eden()->clear(SpaceDecorator::Mangle);
from()->clear(SpaceDecorator::Mangle);
if (ZapUnusedHeapArea) {
// This is now done here because of the piece-meal mangling which
// can check for valid mangling at intermediate points in the
// collection(s). When a minor collection fails to collect
// sufficient space resizing of the young generation can occur
// an redistribute the spaces in the young generation. Mangle
// here so that unzapped regions don't get distributed to
// other spaces.
to()->mangle_unused_area();
}
swap_spaces();
assert(to()->is_empty(), "to space should be empty now");
adjust_desired_tenuring_threshold();
// A successful scavenge should restart the GC time limit count which is
// for full GC's.
AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
size_policy->reset_gc_overhead_limit_count();
if (PrintGC && !PrintGCDetails) {
gch->print_heap_change(gch_prev_used);
}
assert(!gch->incremental_collection_failed(), "Should be clear");
} else {
assert(_promo_failure_scan_stack.is_empty(), "post condition");
_promo_failure_scan_stack.clear(true); // Clear cached segments.
remove_forwarding_pointers();
if (PrintGCDetails) {
gclog_or_tty->print(" (promotion failed) ");
}
// Add to-space to the list of space to compact
// when a promotion failure has occurred. In that
// case there can be live objects in to-space
// as a result of a partial evacuation of eden
// and from-space.
swap_spaces(); // For uniformity wrt ParNewGeneration.
from()->set_next_compaction_space(to());
gch->set_incremental_collection_failed();
// Inform the next generation that a promotion failure occurred.
_next_gen->promotion_failure_occurred();
gc_tracer.report_promotion_failed(_promotion_failed_info);
// Reset the PromotionFailureALot counters.
NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
}
// set new iteration safe limit for the survivor spaces
from()->set_concurrent_iteration_safe_limit(from()->top());
to()->set_concurrent_iteration_safe_limit(to()->top());
SpecializationStats::print();
// We need to use a monotonically non-decreasing time in ms
// or we will see time-warp warnings and os::javaTimeMillis()
// does not guarantee monotonicity.
jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
update_time_of_last_gc(now);
gch->trace_heap_after_gc(&gc_tracer);
gc_tracer.report_tenuring_threshold(tenuring_threshold());
_gc_timer->register_gc_end();
gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
}
void DefNewGeneration::collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_tlab) {
assert(full || size > 0, "otherwise we don't want to collect");
GenCollectedHeap* gch = GenCollectedHeap::heap();
_next_gen = gch->next_gen(this);
assert(_next_gen != NULL,
"This must be the youngest gen, and not the only gen");
// If the next generation is too full to accomodate promotion
// from this generation, pass on collection; let the next generation
// do it.
if (!collection_attempt_is_safe()) {
gch->set_incremental_collection_will_fail();
return;
}
assert(to()->is_empty(), "Else not collection_attempt_is_safe");
init_assuming_no_promotion_failure();
TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
// Capture heap used before collection (for printing).
size_t gch_prev_used = gch->used();
SpecializationStats::clear();
// These can be shared for all code paths
IsAliveClosure is_alive(this);
ScanWeakRefClosure scan_weak_ref(this);
age_table()->clear();
to()->clear(SpaceDecorator::Mangle);
gch->rem_set()->prepare_for_younger_refs_iterate(false);
assert(gch->no_allocs_since_save_marks(0),
"save marks have not been newly set.");
// Not very pretty.
CollectorPolicy* cp = gch->collector_policy();
FastScanClosure fsc_with_no_gc_barrier(this, false);
FastScanClosure fsc_with_gc_barrier(this, true);
set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
&fsc_with_no_gc_barrier,
&fsc_with_gc_barrier);
assert(gch->no_allocs_since_save_marks(0),
"save marks have not been newly set.");
gch->gen_process_strong_roots(_level,
true, // Process younger gens, if any,
// as strong roots.
true, // activate StrongRootsScope
false, // not collecting perm generation.
SharedHeap::SO_AllClasses,
&fsc_with_no_gc_barrier,
true, // walk *all* scavengable nmethods
&fsc_with_gc_barrier);
// "evacuate followers".
evacuate_followers.do_void();
FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
ReferenceProcessor* rp = ref_processor();
rp->setup_policy(clear_all_soft_refs);
rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
NULL);
if (!promotion_failed()) {
// Swap the survivor spaces.
eden()->clear(SpaceDecorator::Mangle);
from()->clear(SpaceDecorator::Mangle);
if (ZapUnusedHeapArea) {
// This is now done here because of the piece-meal mangling which
// can check for valid mangling at intermediate points in the
// collection(s). When a minor collection fails to collect
// sufficient space resizing of the young generation can occur
// an redistribute the spaces in the young generation. Mangle
// here so that unzapped regions don't get distributed to
// other spaces.
to()->mangle_unused_area();
}
swap_spaces();
assert(to()->is_empty(), "to space should be empty now");
// Set the desired survivor size to half the real survivor space
_tenuring_threshold =
age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
if (PrintGC && !PrintGCDetails) {
gch->print_heap_change(gch_prev_used);
}
} else {
assert(HandlePromotionFailure,
"Should not be here unless promotion failure handling is on");
assert(_promo_failure_scan_stack != NULL &&
_promo_failure_scan_stack->length() == 0, "post condition");
// deallocate stack and it's elements
delete _promo_failure_scan_stack;
_promo_failure_scan_stack = NULL;
remove_forwarding_pointers();
if (PrintGCDetails) {
gclog_or_tty->print(" (promotion failed) ");
}
// Add to-space to the list of space to compact
// when a promotion failure has occurred. In that
// case there can be live objects in to-space
// as a result of a partial evacuation of eden
// and from-space.
swap_spaces(); // For the sake of uniformity wrt ParNewGeneration::collect().
from()->set_next_compaction_space(to());
gch->set_incremental_collection_will_fail();
// Inform the next generation that a promotion failure occurred.
_next_gen->promotion_failure_occurred();
// Reset the PromotionFailureALot counters.
NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
}
// set new iteration safe limit for the survivor spaces
from()->set_concurrent_iteration_safe_limit(from()->top());
to()->set_concurrent_iteration_safe_limit(to()->top());
SpecializationStats::print();
update_time_of_last_gc(os::javaTimeMillis());
}
void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
bool clear_all_softrefs) {
// Recursively traverse all live objects and mark them
GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
G1CollectedHeap* g1h = G1CollectedHeap::heap();
// Need cleared claim bits for the roots processing
ClassLoaderDataGraph::clear_claimed_marks();
MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
{
G1RootProcessor root_processor(g1h, 1);
if (ClassUnloading) {
root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
&GenMarkSweep::follow_cld_closure,
&follow_code_closure);
} else {
root_processor.process_all_roots_no_string_table(
&GenMarkSweep::follow_root_closure,
&GenMarkSweep::follow_cld_closure,
&follow_code_closure);
}
}
{
GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
// Process reference objects found during marking
ReferenceProcessor* rp = GenMarkSweep::ref_processor();
assert(rp == g1h->ref_processor_stw(), "Sanity");
rp->setup_policy(clear_all_softrefs);
const ReferenceProcessorStats& stats =
rp->process_discovered_references(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
&GenMarkSweep::follow_stack_closure,
NULL,
gc_timer());
gc_tracer()->report_gc_reference_stats(stats);
}
// This is the point where the entire marking should have completed.
assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
if (ClassUnloading) {
GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
// Unload classes and purge the SystemDictionary.
bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
// Unload nmethods.
CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
// Prune dead klasses from subklass/sibling/implementor lists.
Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
}
{
GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
// Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
}
if (G1StringDedup::is_enabled()) {
GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
G1StringDedup::unlink(&GenMarkSweep::is_alive);
}
if (VerifyDuringGC) {
HandleMark hm; // handle scope
#if defined(COMPILER2) || INCLUDE_JVMCI
DerivedPointerTableDeactivate dpt_deact;
#endif
g1h->prepare_for_verify();
// Note: we can verify only the heap here. When an object is
// marked, the previous value of the mark word (including
// identity hash values, ages, etc) is preserved, and the mark
// word is set to markOop::marked_value - effectively removing
// any hash values from the mark word. These hash values are
// used when verifying the dictionaries and so removing them
// from the mark word can make verification of the dictionaries
// fail. At the end of the GC, the original mark word values
// (including hash values) are restored to the appropriate
// objects.
GCTraceTime(Info, gc, verify)("During GC (full)");
g1h->verify(VerifyOption_G1UseMarkWord);
}
gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
}
void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
bool clear_all_softrefs) {
// Recursively traverse all live objects and mark them
GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer());
GenMarkSweep::trace(" 1");
SharedHeap* sh = SharedHeap::heap();
// Need cleared claim bits for the strong roots processing
ClassLoaderDataGraph::clear_claimed_marks();
sh->process_strong_roots(true, // activate StrongRootsScope
false, // not scavenging.
SharedHeap::SO_SystemClasses,
&GenMarkSweep::follow_root_closure,
&GenMarkSweep::follow_code_root_closure,
&GenMarkSweep::follow_klass_closure);
// Process reference objects found during marking
ReferenceProcessor* rp = GenMarkSweep::ref_processor();
assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
rp->setup_policy(clear_all_softrefs);
const ReferenceProcessorStats& stats =
rp->process_discovered_references(&GenMarkSweep::is_alive,
&GenMarkSweep::keep_alive,
&GenMarkSweep::follow_stack_closure,
NULL,
gc_timer());
gc_tracer()->report_gc_reference_stats(stats);
// This is the point where the entire marking should have completed.
assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
// Unload classes and purge the SystemDictionary.
bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
// Unload nmethods.
CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
// Prune dead klasses from subklass/sibling/implementor lists.
Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
// Delete entries for dead interned strings.
StringTable::unlink(&GenMarkSweep::is_alive);
// Clean up unreferenced symbols in symbol table.
SymbolTable::unlink();
if (VerifyDuringGC) {
HandleMark hm; // handle scope
COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
Universe::heap()->prepare_for_verify();
// Note: we can verify only the heap here. When an object is
// marked, the previous value of the mark word (including
// identity hash values, ages, etc) is preserved, and the mark
// word is set to markOop::marked_value - effectively removing
// any hash values from the mark word. These hash values are
// used when verifying the dictionaries and so removing them
// from the mark word can make verification of the dictionaries
// fail. At the end of the GC, the orginal mark word values
// (including hash values) are restored to the appropriate
// objects.
if (!VerifySilently) {
gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
}
Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
if (!VerifySilently) {
gclog_or_tty->print_cr("]");
}
}
gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
}
