void CardTableRS::clear_into_gen_and_younger(Generation* gen) {
GenCollectedHeap* gch = GenCollectedHeap::heap();
// Gen and all younger have been evacuated. We can clear
// remembered set entries for the next highest generation
// (we know that it has no pointers to younger gens) and
// those below.
Generation* g = gch->next_gen(gen);
while (g != NULL) {
clear(g->reserved());
g = gch->prev_gen(gen);
}
}
bool DefNewGeneration::collection_attempt_is_safe() {
if (!to()->is_empty()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print(" :: to is not empty :: ");
}
return false;
}
if (_next_gen == NULL) {
GenCollectedHeap* gch = GenCollectedHeap::heap();
_next_gen = gch->next_gen(this);
}
return _next_gen->promotion_attempt_is_safe(used());
}
bool DefNewGeneration::full_promotion_would_succeed() {
if (_next_gen == NULL) {
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");
}
// Decide if there's enough room for a full promotion
// When using extremely large edens, we effectively lose a large amount of old space.
// Use the "MaxLiveObjectEvacuationRatio" flag to reduce the minimum evacuation space
// requirements. If there is not enough space to evacuate eden during a scavenge, the
// VM will immediately exit with an out of memory error. This flag has not been tested
// with collectors other than simple mark & sweep.
const double evacuation_ratio = MaxLiveObjectEvacuationRatio / 100.0;
size_t worst_case_evacuation = (size_t)(used() * evacuation_ratio);
return _next_gen->max_contiguous_available() >= worst_case_evacuation;
}
bool DefNewGeneration::collection_attempt_is_safe() {
if (!to()->is_empty()) {
return false;
}
if (_next_gen == NULL) {
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");
}
// Decide if there's enough room for a full promotion
// When using extremely large edens, we effectively lose a
// large amount of old space. Use the "MaxLiveObjectEvacuationRatio"
// flag to reduce the minimum evacuation space requirements. If
// there is not enough space to evacuate eden during a scavenge,
// the VM will immediately exit with an out of memory error.
// This flag has not been tested
// with collectors other than simple mark & sweep.
//
// Note that with the addition of promotion failure handling, the
// VM will not immediately exit but will undo the young generation
// collection. The parameter is left here for compatibility.
const double evacuation_ratio = MaxLiveObjectEvacuationRatio / 100.0;
// worst_case_evacuation is based on "used()". For the case where this
// method is called after a collection, this is still appropriate because
// the case that needs to be detected is one in which a full collection
// has been done and has overflowed into the young generation. In that
// case a minor collection will fail (the overflow of the full collection
// means there is no space in the old generation for any promotion).
size_t worst_case_evacuation = (size_t)(used() * evacuation_ratio);
return _next_gen->promotion_attempt_is_safe(worst_case_evacuation,
HandlePromotionFailure);
}
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 DefNewGeneration::collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_large_noref,
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 worst-case promotion
// from this generation, pass on collection; let the next generation
// do it.
if (!full_promotion_would_succeed()) {
gch->set_incremental_collection_will_fail();
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("DefNewGeneration::collect"
" contiguous_available: " SIZE_FORMAT " < used: " SIZE_FORMAT,
_next_gen->max_contiguous_available(), used());
}
return;
}
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();
gch->rem_set()->prepare_for_younger_refs_iterate(false);
assert(gch->no_allocs_since_save_marks(0),
"save marks have not been newly set.");
// Weak refs.
// FIXME: Are these storage leaks, or are they resource objects?
NOT_COMPILER2(ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy());
COMPILER2_ONLY(ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy());
// Not very pretty.
CollectorPolicy* cp = gch->collector_policy();
if (!cp->is_train_policy()) {
FastScanClosure fsc_with_no_gc_barrier(this, false);
FastScanClosure fsc_with_gc_barrier(this, true);
FastEvacuateFollowersClosure evacuate_followers(gch, _level,
&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->process_strong_roots(_level,
true, // Process younger gens, if any, as
// strong roots.
false,// not collecting permanent generation.
GenCollectedHeap::CSO_AllClasses,
&fsc_with_gc_barrier,
&fsc_with_no_gc_barrier);
// "evacuate followers".
evacuate_followers.do_void();
FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
ref_processor()->process_discovered_references(soft_ref_policy,
&is_alive,
&keep_alive,
&evacuate_followers);
} else { // Train policy
ScanClosure sc_with_no_gc_barrier(this, false);
ScanClosure sc_with_gc_barrier(this, true);
EvacuateFollowersClosure evacuate_followers(gch, _level,
&sc_with_no_gc_barrier,
&sc_with_gc_barrier);
gch->process_strong_roots(_level,
true, // Process younger gens, if any, as
// strong roots.
false,// not collecting perm generation.
GenCollectedHeap::CSO_AllClasses,
&sc_with_gc_barrier,
&sc_with_no_gc_barrier);
// "evacuate followers".
evacuate_followers.do_void();
TrainPolicyKeepAliveClosure keep_alive((TrainGeneration*)_next_gen,
&scan_weak_ref);
ref_processor()->process_discovered_references(soft_ref_policy,
&is_alive,
&keep_alive,
&evacuate_followers);
}
// Swap the survivor spaces.
eden()->clear();
from()->clear();
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);
}
SpecializationStats::print();
update_time_of_last_gc(os::javaTimeMillis());
}