Java example source code file (defNewGeneration.cpp)
The defNewGeneration.cpp Java example source code/*
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#include "precompiled.hpp"
#include "gc_implementation/shared/collectorCounters.hpp"
#include "gc_implementation/shared/gcPolicyCounters.hpp"
#include "gc_implementation/shared/gcHeapSummary.hpp"
#include "gc_implementation/shared/gcTimer.hpp"
#include "gc_implementation/shared/gcTraceTime.hpp"
#include "gc_implementation/shared/gcTrace.hpp"
#include "gc_implementation/shared/spaceDecorator.hpp"
#include "memory/defNewGeneration.inline.hpp"
#include "memory/gcLocker.inline.hpp"
#include "memory/genCollectedHeap.hpp"
#include "memory/genOopClosures.inline.hpp"
#include "memory/genRemSet.hpp"
#include "memory/generationSpec.hpp"
#include "memory/iterator.hpp"
#include "memory/referencePolicy.hpp"
#include "memory/space.inline.hpp"
#include "oops/instanceRefKlass.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/thread.inline.hpp"
#include "utilities/copy.hpp"
#include "utilities/stack.inline.hpp"
//
// DefNewGeneration functions.
// Methods of protected closure types.
DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
assert(g->level() == 0, "Optimized for youngest gen.");
}
bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
}
DefNewGeneration::KeepAliveClosure::
KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
_rs = (CardTableRS*)rs;
}
void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
DefNewGeneration::FastKeepAliveClosure::
FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
DefNewGeneration::KeepAliveClosure(cl) {
_boundary = g->reserved().end();
}
void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
DefNewGeneration::EvacuateFollowersClosure::
EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
ScanClosure* cur, ScanClosure* older) :
_gch(gch), _level(level),
_scan_cur_or_nonheap(cur), _scan_older(older)
{}
void DefNewGeneration::EvacuateFollowersClosure::do_void() {
do {
_gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
_scan_older);
} while (!_gch->no_allocs_since_save_marks(_level));
}
DefNewGeneration::FastEvacuateFollowersClosure::
FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
DefNewGeneration* gen,
FastScanClosure* cur, FastScanClosure* older) :
_gch(gch), _level(level), _gen(gen),
_scan_cur_or_nonheap(cur), _scan_older(older)
{}
void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
do {
_gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
_scan_older);
} while (!_gch->no_allocs_since_save_marks(_level));
guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
}
ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
{
assert(_g->level() == 0, "Optimized for youngest generation");
_boundary = _g->reserved().end();
}
void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
{
assert(_g->level() == 0, "Optimized for youngest generation");
_boundary = _g->reserved().end();
}
void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
void KlassScanClosure::do_klass(Klass* klass) {
#ifndef PRODUCT
if (TraceScavenge) {
ResourceMark rm;
gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
klass,
klass->external_name(),
klass->has_modified_oops() ? "true" : "false");
}
#endif
// If the klass has not been dirtied we know that there's
// no references into the young gen and we can skip it.
if (klass->has_modified_oops()) {
if (_accumulate_modified_oops) {
klass->accumulate_modified_oops();
}
// Clear this state since we're going to scavenge all the metadata.
klass->clear_modified_oops();
// Tell the closure which Klass is being scanned so that it can be dirtied
// if oops are left pointing into the young gen.
_scavenge_closure->set_scanned_klass(klass);
klass->oops_do(_scavenge_closure);
_scavenge_closure->set_scanned_klass(NULL);
}
}
ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
_g(g)
{
assert(_g->level() == 0, "Optimized for youngest generation");
_boundary = _g->reserved().end();
}
void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
KlassRemSet* klass_rem_set)
: _scavenge_closure(scavenge_closure),
_accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
DefNewGeneration::DefNewGeneration(ReservedSpace rs,
size_t initial_size,
int level,
const char* policy)
: Generation(rs, initial_size, level),
_promo_failure_drain_in_progress(false),
_should_allocate_from_space(false)
{
MemRegion cmr((HeapWord*)_virtual_space.low(),
(HeapWord*)_virtual_space.high());
Universe::heap()->barrier_set()->resize_covered_region(cmr);
if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
_eden_space = new ConcEdenSpace(this);
} else {
_eden_space = new EdenSpace(this);
}
_from_space = new ContiguousSpace();
_to_space = new ContiguousSpace();
if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
vm_exit_during_initialization("Could not allocate a new gen space");
// Compute the maximum eden and survivor space sizes. These sizes
// are computed assuming the entire reserved space is committed.
// These values are exported as performance counters.
uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
uintx size = _virtual_space.reserved_size();
_max_survivor_size = compute_survivor_size(size, alignment);
_max_eden_size = size - (2*_max_survivor_size);
// allocate the performance counters
// Generation counters -- generation 0, 3 subspaces
_gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
_gc_counters = new CollectorCounters(policy, 0);
_eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
_gen_counters);
_from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
_gen_counters);
_to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
_gen_counters);
compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
update_counters();
_next_gen = NULL;
_tenuring_threshold = MaxTenuringThreshold;
_pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
_gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
}
void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
bool clear_space,
bool mangle_space) {
uintx alignment =
GenCollectedHeap::heap()->collector_policy()->space_alignment();
// If the spaces are being cleared (only done at heap initialization
// currently), the survivor spaces need not be empty.
// Otherwise, no care is taken for used areas in the survivor spaces
// so check.
assert(clear_space || (to()->is_empty() && from()->is_empty()),
"Initialization of the survivor spaces assumes these are empty");
// Compute sizes
uintx size = _virtual_space.committed_size();
uintx survivor_size = compute_survivor_size(size, alignment);
uintx eden_size = size - (2*survivor_size);
assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
if (eden_size < minimum_eden_size) {
// May happen due to 64Kb rounding, if so adjust eden size back up
minimum_eden_size = align_size_up(minimum_eden_size, alignment);
uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
uintx unaligned_survivor_size =
align_size_down(maximum_survivor_size, alignment);
survivor_size = MAX2(unaligned_survivor_size, alignment);
eden_size = size - (2*survivor_size);
assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
assert(eden_size >= minimum_eden_size, "just checking");
}
char *eden_start = _virtual_space.low();
char *from_start = eden_start + eden_size;
char *to_start = from_start + survivor_size;
char *to_end = to_start + survivor_size;
assert(to_end == _virtual_space.high(), "just checking");
assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
// A minimum eden size implies that there is a part of eden that
// is being used and that affects the initialization of any
// newly formed eden.
bool live_in_eden = minimum_eden_size > 0;
// If not clearing the spaces, do some checking to verify that
// the space are already mangled.
if (!clear_space) {
// Must check mangling before the spaces are reshaped. Otherwise,
// the bottom or end of one space may have moved into another
// a failure of the check may not correctly indicate which space
// is not properly mangled.
if (ZapUnusedHeapArea) {
HeapWord* limit = (HeapWord*) _virtual_space.high();
eden()->check_mangled_unused_area(limit);
from()->check_mangled_unused_area(limit);
to()->check_mangled_unused_area(limit);
}
}
// Reset the spaces for their new regions.
eden()->initialize(edenMR,
clear_space && !live_in_eden,
SpaceDecorator::Mangle);
// If clear_space and live_in_eden, we will not have cleared any
// portion of eden above its top. This can cause newly
// expanded space not to be mangled if using ZapUnusedHeapArea.
// We explicitly do such mangling here.
if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
eden()->mangle_unused_area();
}
from()->initialize(fromMR, clear_space, mangle_space);
to()->initialize(toMR, clear_space, mangle_space);
// Set next compaction spaces.
eden()->set_next_compaction_space(from());
// The to-space is normally empty before a compaction so need
// not be considered. The exception is during promotion
// failure handling when to-space can contain live objects.
from()->set_next_compaction_space(NULL);
}
void DefNewGeneration::swap_spaces() {
ContiguousSpace* s = from();
_from_space = to();
_to_space = s;
eden()->set_next_compaction_space(from());
// The to-space is normally empty before a compaction so need
// not be considered. The exception is during promotion
// failure handling when to-space can contain live objects.
from()->set_next_compaction_space(NULL);
if (UsePerfData) {
CSpaceCounters* c = _from_counters;
_from_counters = _to_counters;
_to_counters = c;
}
}
bool DefNewGeneration::expand(size_t bytes) {
MutexLocker x(ExpandHeap_lock);
HeapWord* prev_high = (HeapWord*) _virtual_space.high();
bool success = _virtual_space.expand_by(bytes);
if (success && ZapUnusedHeapArea) {
// Mangle newly committed space immediately because it
// can be done here more simply that after the new
// spaces have been computed.
HeapWord* new_high = (HeapWord*) _virtual_space.high();
MemRegion mangle_region(prev_high, new_high);
SpaceMangler::mangle_region(mangle_region);
}
// Do not attempt an expand-to-the reserve size. The
// request should properly observe the maximum size of
// the generation so an expand-to-reserve should be
// unnecessary. Also a second call to expand-to-reserve
// value potentially can cause an undue expansion.
// For example if the first expand fail for unknown reasons,
// but the second succeeds and expands the heap to its maximum
// value.
if (GC_locker::is_active()) {
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("Garbage collection disabled, "
"expanded heap instead");
}
}
return success;
}
void DefNewGeneration::compute_new_size() {
// This is called after a gc that includes the following generation
// (which is required to exist.) So from-space will normally be empty.
// Note that we check both spaces, since if scavenge failed they revert roles.
// If not we bail out (otherwise we would have to relocate the objects)
if (!from()->is_empty() || !to()->is_empty()) {
return;
}
int next_level = level() + 1;
GenCollectedHeap* gch = GenCollectedHeap::heap();
assert(next_level < gch->_n_gens,
"DefNewGeneration cannot be an oldest gen");
Generation* next_gen = gch->_gens[next_level];
size_t old_size = next_gen->capacity();
size_t new_size_before = _virtual_space.committed_size();
size_t min_new_size = spec()->init_size();
size_t max_new_size = reserved().byte_size();
assert(min_new_size <= new_size_before &&
new_size_before <= max_new_size,
"just checking");
// All space sizes must be multiples of Generation::GenGrain.
size_t alignment = Generation::GenGrain;
// Compute desired new generation size based on NewRatio and
// NewSizeThreadIncrease
size_t desired_new_size = old_size/NewRatio;
int threads_count = Threads::number_of_non_daemon_threads();
size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
// Adjust new generation size
desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
assert(desired_new_size <= max_new_size, "just checking");
bool changed = false;
if (desired_new_size > new_size_before) {
size_t change = desired_new_size - new_size_before;
assert(change % alignment == 0, "just checking");
if (expand(change)) {
changed = true;
}
// If the heap failed to expand to the desired size,
// "changed" will be false. If the expansion failed
// (and at this point it was expected to succeed),
// ignore the failure (leaving "changed" as false).
}
if (desired_new_size < new_size_before && eden()->is_empty()) {
// bail out of shrinking if objects in eden
size_t change = new_size_before - desired_new_size;
assert(change % alignment == 0, "just checking");
_virtual_space.shrink_by(change);
changed = true;
}
if (changed) {
// The spaces have already been mangled at this point but
// may not have been cleared (set top = bottom) and should be.
// Mangling was done when the heap was being expanded.
compute_space_boundaries(eden()->used(),
SpaceDecorator::Clear,
SpaceDecorator::DontMangle);
MemRegion cmr((HeapWord*)_virtual_space.low(),
(HeapWord*)_virtual_space.high());
Universe::heap()->barrier_set()->resize_covered_region(cmr);
if (Verbose && PrintGC) {
size_t new_size_after = _virtual_space.committed_size();
size_t eden_size_after = eden()->capacity();
size_t survivor_size_after = from()->capacity();
gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
SIZE_FORMAT "K [eden="
SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
new_size_before/K, new_size_after/K,
eden_size_after/K, survivor_size_after/K);
if (WizardMode) {
gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
thread_increase_size/K, threads_count);
}
gclog_or_tty->cr();
}
}
}
void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
assert(false, "NYI -- are you sure you want to call this?");
}
size_t DefNewGeneration::capacity() const {
return eden()->capacity()
+ from()->capacity(); // to() is only used during scavenge
}
size_t DefNewGeneration::used() const {
return eden()->used()
+ from()->used(); // to() is only used during scavenge
}
size_t DefNewGeneration::free() const {
return eden()->free()
+ from()->free(); // to() is only used during scavenge
}
size_t DefNewGeneration::max_capacity() const {
const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
const size_t reserved_bytes = reserved().byte_size();
return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
}
size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
return eden()->free();
}
size_t DefNewGeneration::capacity_before_gc() const {
return eden()->capacity();
}
size_t DefNewGeneration::contiguous_available() const {
return eden()->free();
}
HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
void DefNewGeneration::object_iterate(ObjectClosure* blk) {
eden()->object_iterate(blk);
from()->object_iterate(blk);
}
void DefNewGeneration::space_iterate(SpaceClosure* blk,
bool usedOnly) {
blk->do_space(eden());
blk->do_space(from());
blk->do_space(to());
}
// The last collection bailed out, we are running out of heap space,
// so we try to allocate the from-space, too.
HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
HeapWord* result = NULL;
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
" will_fail: %s"
" heap_lock: %s"
" free: " SIZE_FORMAT,
size,
GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
"true" : "false",
Heap_lock->is_locked() ? "locked" : "unlocked",
from()->free());
}
if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
if (Heap_lock->owned_by_self() ||
(SafepointSynchronize::is_at_safepoint() &&
Thread::current()->is_VM_thread())) {
// If the Heap_lock is not locked by this thread, this will be called
// again later with the Heap_lock held.
result = from()->allocate(size);
} else if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" Heap_lock is not owned by self");
}
} else if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
}
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
}
return result;
}
HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
bool is_tlab,
bool parallel) {
// We don't attempt to expand the young generation (but perhaps we should.)
return allocate(size, is_tlab);
}
void DefNewGeneration::adjust_desired_tenuring_threshold() {
// Set the desired survivor size to half the real survivor space
_tenuring_threshold =
age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
}
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());
}
class RemoveForwardPointerClosure: public ObjectClosure {
public:
void do_object(oop obj) {
obj->init_mark();
}
};
void DefNewGeneration::init_assuming_no_promotion_failure() {
_promotion_failed = false;
_promotion_failed_info.reset();
from()->set_next_compaction_space(NULL);
}
void DefNewGeneration::remove_forwarding_pointers() {
RemoveForwardPointerClosure rspc;
eden()->object_iterate(&rspc);
from()->object_iterate(&rspc);
// Now restore saved marks, if any.
assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
"should be the same");
while (!_objs_with_preserved_marks.is_empty()) {
oop obj = _objs_with_preserved_marks.pop();
markOop m = _preserved_marks_of_objs.pop();
obj->set_mark(m);
}
_objs_with_preserved_marks.clear(true);
_preserved_marks_of_objs.clear(true);
}
void DefNewGeneration::preserve_mark(oop obj, markOop m) {
assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
"Oversaving!");
_objs_with_preserved_marks.push(obj);
_preserved_marks_of_objs.push(m);
}
void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
if (m->must_be_preserved_for_promotion_failure(obj)) {
preserve_mark(obj, m);
}
}
void DefNewGeneration::handle_promotion_failure(oop old) {
if (PrintPromotionFailure && !_promotion_failed) {
gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
old->size());
}
_promotion_failed = true;
_promotion_failed_info.register_copy_failure(old->size());
preserve_mark_if_necessary(old, old->mark());
// forward to self
old->forward_to(old);
_promo_failure_scan_stack.push(old);
if (!_promo_failure_drain_in_progress) {
// prevent recursion in copy_to_survivor_space()
_promo_failure_drain_in_progress = true;
drain_promo_failure_scan_stack();
_promo_failure_drain_in_progress = false;
}
}
oop DefNewGeneration::copy_to_survivor_space(oop old) {
assert(is_in_reserved(old) && !old->is_forwarded(),
"shouldn't be scavenging this oop");
size_t s = old->size();
oop obj = NULL;
// Try allocating obj in to-space (unless too old)
if (old->age() < tenuring_threshold()) {
obj = (oop) to()->allocate(s);
}
// Otherwise try allocating obj tenured
if (obj == NULL) {
obj = _next_gen->promote(old, s);
if (obj == NULL) {
handle_promotion_failure(old);
return old;
}
} else {
// Prefetch beyond obj
const intx interval = PrefetchCopyIntervalInBytes;
Prefetch::write(obj, interval);
// Copy obj
Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
// Increment age if obj still in new generation
obj->incr_age();
age_table()->add(obj, s);
}
// Done, insert forward pointer to obj in this header
old->forward_to(obj);
return obj;
}
void DefNewGeneration::drain_promo_failure_scan_stack() {
while (!_promo_failure_scan_stack.is_empty()) {
oop obj = _promo_failure_scan_stack.pop();
obj->oop_iterate(_promo_failure_scan_stack_closure);
}
}
void DefNewGeneration::save_marks() {
eden()->set_saved_mark();
to()->set_saved_mark();
from()->set_saved_mark();
}
void DefNewGeneration::reset_saved_marks() {
eden()->reset_saved_mark();
to()->reset_saved_mark();
from()->reset_saved_mark();
}
bool DefNewGeneration::no_allocs_since_save_marks() {
assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
return to()->saved_mark_at_top();
}
#define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
\
void DefNewGeneration:: \
oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
cl->set_generation(this); \
eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
to()->oop_since_save_marks_iterate##nv_suffix(cl); \
from()->oop_since_save_marks_iterate##nv_suffix(cl); \
cl->reset_generation(); \
save_marks(); \
}
ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
#undef DefNew_SINCE_SAVE_MARKS_DEFN
void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
size_t max_alloc_words) {
if (requestor == this || _promotion_failed) return;
assert(requestor->level() > level(), "DefNewGeneration must be youngest");
/* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
if (to_space->top() > to_space->bottom()) {
trace("to_space not empty when contribute_scratch called");
}
*/
ContiguousSpace* to_space = to();
assert(to_space->end() >= to_space->top(), "pointers out of order");
size_t free_words = pointer_delta(to_space->end(), to_space->top());
if (free_words >= MinFreeScratchWords) {
ScratchBlock* sb = (ScratchBlock*)to_space->top();
sb->num_words = free_words;
sb->next = list;
list = sb;
}
}
void DefNewGeneration::reset_scratch() {
// If contributing scratch in to_space, mangle all of
// to_space if ZapUnusedHeapArea. This is needed because
// top is not maintained while using to-space as scratch.
if (ZapUnusedHeapArea) {
to()->mangle_unused_area_complete();
}
}
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());
}
void DefNewGeneration::gc_epilogue(bool full) {
DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
assert(!GC_locker::is_active(), "We should not be executing here");
// Check if the heap is approaching full after a collection has
// been done. Generally the young generation is empty at
// a minimum at the end of a collection. If it is not, then
// the heap is approaching full.
GenCollectedHeap* gch = GenCollectedHeap::heap();
if (full) {
DEBUG_ONLY(seen_incremental_collection_failed = false;)
if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
GCCause::to_string(gch->gc_cause()));
}
gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
set_should_allocate_from_space(); // we seem to be running out of space
} else {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
GCCause::to_string(gch->gc_cause()));
}
gch->clear_incremental_collection_failed(); // We just did a full collection
clear_should_allocate_from_space(); // if set
}
} else {
#ifdef ASSERT
// It is possible that incremental_collection_failed() == true
// here, because an attempted scavenge did not succeed. The policy
// is normally expected to cause a full collection which should
// clear that condition, so we should not be here twice in a row
// with incremental_collection_failed() == true without having done
// a full collection in between.
if (!seen_incremental_collection_failed &&
gch->incremental_collection_failed()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
GCCause::to_string(gch->gc_cause()));
}
seen_incremental_collection_failed = true;
} else if (seen_incremental_collection_failed) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
GCCause::to_string(gch->gc_cause()));
}
assert(gch->gc_cause() == GCCause::_scavenge_alot ||
(gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
!gch->incremental_collection_failed(),
"Twice in a row");
seen_incremental_collection_failed = false;
}
#endif // ASSERT
}
if (ZapUnusedHeapArea) {
eden()->check_mangled_unused_area_complete();
from()->check_mangled_unused_area_complete();
to()->check_mangled_unused_area_complete();
}
if (!CleanChunkPoolAsync) {
Chunk::clean_chunk_pool();
}
// update the generation and space performance counters
update_counters();
gch->collector_policy()->counters()->update_counters();
}
void DefNewGeneration::record_spaces_top() {
assert(ZapUnusedHeapArea, "Not mangling unused space");
eden()->set_top_for_allocations();
to()->set_top_for_allocations();
from()->set_top_for_allocations();
}
void DefNewGeneration::ref_processor_init() {
Generation::ref_processor_init();
}
void DefNewGeneration::update_counters() {
if (UsePerfData) {
_eden_counters->update_all();
_from_counters->update_all();
_to_counters->update_all();
_gen_counters->update_all();
}
}
void DefNewGeneration::verify() {
eden()->verify();
from()->verify();
to()->verify();
}
void DefNewGeneration::print_on(outputStream* st) const {
Generation::print_on(st);
st->print(" eden");
eden()->print_on(st);
st->print(" from");
from()->print_on(st);
st->print(" to ");
to()->print_on(st);
}
const char* DefNewGeneration::name() const {
return "def new generation";
}
// Moved from inline file as they are not called inline
CompactibleSpace* DefNewGeneration::first_compaction_space() const {
return eden();
}
HeapWord* DefNewGeneration::allocate(size_t word_size,
bool is_tlab) {
// This is the slow-path allocation for the DefNewGeneration.
// Most allocations are fast-path in compiled code.
// We try to allocate from the eden. If that works, we are happy.
// Note that since DefNewGeneration supports lock-free allocation, we
// have to use it here, as well.
HeapWord* result = eden()->par_allocate(word_size);
if (result != NULL) {
if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
_next_gen->sample_eden_chunk();
}
return result;
}
do {
HeapWord* old_limit = eden()->soft_end();
if (old_limit < eden()->end()) {
// Tell the next generation we reached a limit.
HeapWord* new_limit =
next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
if (new_limit != NULL) {
Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
} else {
assert(eden()->soft_end() == eden()->end(),
"invalid state after allocation_limit_reached returned null");
}
} else {
// The allocation failed and the soft limit is equal to the hard limit,
// there are no reasons to do an attempt to allocate
assert(old_limit == eden()->end(), "sanity check");
break;
}
// Try to allocate until succeeded or the soft limit can't be adjusted
result = eden()->par_allocate(word_size);
} while (result == NULL);
// If the eden is full and the last collection bailed out, we are running
// out of heap space, and we try to allocate the from-space, too.
// allocate_from_space can't be inlined because that would introduce a
// circular dependency at compile time.
if (result == NULL) {
result = allocate_from_space(word_size);
} else if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
_next_gen->sample_eden_chunk();
}
return result;
}
HeapWord* DefNewGeneration::par_allocate(size_t word_size,
bool is_tlab) {
HeapWord* res = eden()->par_allocate(word_size);
if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
_next_gen->sample_eden_chunk();
}
return res;
}
void DefNewGeneration::gc_prologue(bool full) {
// Ensure that _end and _soft_end are the same in eden space.
eden()->set_soft_end(eden()->end());
}
size_t DefNewGeneration::tlab_capacity() const {
return eden()->capacity();
}
size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
return unsafe_max_alloc_nogc();
}
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