void PSMarkSweep::mark_sweep_phase2() {
EventMark m("2 compute new addresses");
TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty);
trace("2");
// Now all live objects are marked, compute the new object addresses.
// It is imperative that we traverse perm_gen LAST. If dead space is
// allowed a range of dead object may get overwritten by a dead int
// array. If perm_gen is not traversed last a klassOop may get
// overwritten. This is fine since it is dead, but if the class has dead
// instances we have to skip them, and in order to find their size we
// need the klassOop!
//
// It is not required that we traverse spaces in the same order in
// phase2, phase3 and phase4, but the ValidateMarkSweep live oops
// tracking expects us to do so. See comment under phase4.
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
// Begin compacting into the old gen
PSMarkSweepDecorator::set_destination_decorator_tenured();
// This will also compact the young gen spaces.
old_gen->precompact();
// Compact the perm gen into the perm gen
PSMarkSweepDecorator::set_destination_decorator_perm_gen();
perm_gen->precompact();
}
HeapWord* HeapInspection::start_of_perm_gen() {
if (is_shared_heap()) {
SharedHeap* sh = SharedHeap::heap();
return sh->perm_gen()->used_region().start();
}
#ifndef SERIALGC
ParallelScavengeHeap* psh = (ParallelScavengeHeap*)Universe::heap();
return psh->perm_gen()->object_space()->used_region().start();
#else
ShouldNotReachHere();
return NULL;
#endif // SERIALGC
}
void PSScavenge::initialize() {
// Arguments must have been parsed
if (AlwaysTenure) {
_tenuring_threshold = 0;
} else if (NeverTenure) {
_tenuring_threshold = markOopDesc::max_age + 1;
} else {
// We want to smooth out our startup times for the AdaptiveSizePolicy
_tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
MaxTenuringThreshold;
}
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
// Set boundary between young_gen and old_gen
assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
"perm above old");
assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
"old above young");
_young_generation_boundary = young_gen->eden_space()->bottom();
// Initialize ref handling object for scavenging.
MemRegion mr = young_gen->reserved();
_ref_processor =
new ReferenceProcessor(mr, // span
ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
(int) ParallelGCThreads, // mt processing degree
true, // mt discovery
(int) ParallelGCThreads, // mt discovery degree
true, // atomic_discovery
NULL, // header provides liveness info
false); // next field updates do not need write barrier
// Cache the cardtable
BarrierSet* bs = Universe::heap()->barrier_set();
assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
_card_table = (CardTableExtension*)bs;
_counters = new CollectorCounters("PSScavenge", 0);
}
// Static method
bool ParallelScavengeHeap::is_in_old_or_perm(oop* p) {
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap,
"Must be ParallelScavengeHeap");
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
if (old_gen->is_in(p)) {
return true;
}
if (perm_gen->is_in(p)) {
return true;
}
return false;
}
void PSMarkSweep::mark_sweep_phase3() {
// Adjust the pointers to reflect the new locations
EventMark m("3 adjust pointers");
TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty);
trace("3");
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
// General strong roots.
Universe::oops_do(adjust_root_pointer_closure());
ReferenceProcessor::oops_do(adjust_root_pointer_closure());
JNIHandles::oops_do(adjust_root_pointer_closure()); // Global (strong) JNI handles
Threads::oops_do(adjust_root_pointer_closure(), NULL);
ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
FlatProfiler::oops_do(adjust_root_pointer_closure());
Management::oops_do(adjust_root_pointer_closure());
JvmtiExport::oops_do(adjust_root_pointer_closure());
// SO_AllClasses
SystemDictionary::oops_do(adjust_root_pointer_closure());
vmSymbols::oops_do(adjust_root_pointer_closure());
//CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure());
// Now adjust pointers in remaining weak roots. (All of which should
// have been cleared if they pointed to non-surviving objects.)
// Global (weak) JNI handles
JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
CodeCache::oops_do(adjust_pointer_closure());
SymbolTable::oops_do(adjust_root_pointer_closure());
StringTable::oops_do(adjust_root_pointer_closure());
ref_processor()->weak_oops_do(adjust_root_pointer_closure());
PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure());
adjust_marks();
young_gen->adjust_pointers();
old_gen->adjust_pointers();
perm_gen->adjust_pointers();
}
void PSMarkSweepDecorator::advance_destination_decorator() {
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
assert(_destination_decorator != NULL, "Sanity");
guarantee(_destination_decorator != heap->perm_gen()->object_mark_sweep(), "Cannot advance perm gen decorator");
PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep();
PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep();
PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep();
PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep();
if ( _destination_decorator == first ) {
_destination_decorator = second;
} else if ( _destination_decorator == second ) {
_destination_decorator = third;
} else if ( _destination_decorator == third ) {
_destination_decorator = fourth;
} else {
fatal("PSMarkSweep attempting to advance past last compaction area");
}
}
void PSMarkSweep::mark_sweep_phase4() {
EventMark m("4 compact heap");
TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty);
trace("4");
// All pointers are now adjusted, move objects accordingly
// It is imperative that we traverse perm_gen first in phase4. All
// classes must be allocated earlier than their instances, and traversing
// perm_gen first makes sure that all klassOops have moved to their new
// location before any instance does a dispatch through it's klass!
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
perm_gen->compact();
old_gen->compact();
young_gen->compact();
}
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSScavenge::invoke_no_policy() {
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
elapsedTimer scavenge_time;
TimeStamp scavenge_entry;
TimeStamp scavenge_midpoint;
TimeStamp scavenge_exit;
scavenge_entry.update();
if (GC_locker::check_active_before_gc()) {
return false;
}
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
GCCause::Cause gc_cause = heap->gc_cause();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
// Check for potential problems.
if (!should_attempt_scavenge()) {
return false;
}
bool promotion_failure_occurred = false;
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
PSAdaptiveSizePolicy* size_policy = heap->size_policy();
heap->increment_total_collections();
AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
if ((gc_cause != GCCause::_java_lang_system_gc) ||
UseAdaptiveSizePolicyWithSystemGC) {
// Gather the feedback data for eden occupancy.
young_gen->eden_space()->accumulate_statistics();
}
// We need to track unique scavenge invocations as well.
_total_invocations++;
if (PrintHeapAtGC) {
Universe::print_heap_before_gc();
}
assert(!NeverTenure||_tenuring_threshold==markWord::max_age+1,"Sanity");
assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
size_t prev_used = heap->used();
assert(promotion_failed() == false, "Sanity");
// Fill in TLABs
heap->accumulate_statistics_all_tlabs();
heap->ensure_parsability(true); // retire TLABs
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyBeforeGC:");
Universe::verify(true);
}
{
ResourceMark rm;
HandleMark hm;
gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
TraceTime t1("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
TraceCollectorStats tcs(counters());
TraceMemoryManagerStats tms(false /* not full GC */);
if (TraceGen0Time) scavenge_time.start();
// Let the size policy know we're starting
size_policy->minor_collection_begin();
// Verify the object start arrays.
if (VerifyObjectStartArray &&
VerifyBeforeGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
// Verify no unmarked old->young roots
if (VerifyRememberedSets) {
CardTableExtension::verify_all_young_refs_imprecise();
}
if (!ScavengeWithObjectsInToSpace) {
assert(young_gen->to_space()->is_empty(),
"Attempt to scavenge with live objects in to_space");
young_gen->to_space()->clear();
} else if (ZapUnusedHeapArea) {
young_gen->to_space()->mangle_unused_area();
}
save_to_space_top_before_gc();
NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
DerivedPointerTable::clear();
reference_processor()->enable_discovery();
// We track how much was promoted to the next generation for
// the AdaptiveSizePolicy.
size_t old_gen_used_before = old_gen->used_in_bytes();
// For PrintGCDetails
size_t young_gen_used_before = young_gen->used_in_bytes();
// Reset our survivor overflow.
set_survivor_overflow(false);
// We need to save the old/perm top values before
// creating the promotion_manager. We pass the top
// values to the card_table, to prevent it from
// straying into the promotion labs.
HeapWord* old_top = old_gen->object_space()->top();
HeapWord* perm_top = perm_gen->object_space()->top();
// Release all previously held resources
gc_task_manager()->release_all_resources();
PSPromotionManager::pre_scavenge();
// We'll use the promotion manager again later.
PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
{
// TraceTime("Roots");
GCTaskQueue* q = GCTaskQueue::create();
for(uint i=0; i<ParallelGCThreads; i++) {
q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
q->enqueue(new OldToYoungRootsTask(perm_gen,perm_top,i));
}
// q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
// We scan the thread roots in parallel
// FIX ME! We should have a NoResourceMarkVerifier here!
Threads::create_thread_roots_tasks(q);
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
// NOTE! ArtaObjects are not normal roots. During scavenges, they are
// considered strong roots. During a mark sweep they are weak roots.
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::arta_objects));
ParallelTaskTerminator terminator(
gc_task_manager()->workers(),
promotion_manager->depth_first() ?
(TaskQueueSetSuper*)promotion_manager->stack_array_depth()
: (TaskQueueSetSuper*)promotion_manager->stack_array_breadth());
if (ParallelGCThreads>1) {
for (uint j=0; j<ParallelGCThreads; j++) {
q->enqueue(new StealTask(&terminator));
}
}
gc_task_manager()->execute_and_wait(q);
}
scavenge_midpoint.update();
// Process reference objects discovered during scavenge
{
ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy();
PSKeepAliveClosure keep_alive(promotion_manager);
PSEvacuateFollowersClosure evac_followers(promotion_manager);
assert(soft_ref_policy != NULL,"No soft reference policy");
if (reference_processor()->processing_is_mt()) {
PSRefProcTaskExecutor task_executor;
reference_processor()->process_discovered_references(
soft_ref_policy, &_is_alive_closure, &keep_alive, &evac_followers,
&task_executor);
} else {
reference_processor()->process_discovered_references(
soft_ref_policy, &_is_alive_closure, &keep_alive, &evac_followers,
NULL);
}
}
// Enqueue reference objects discovered during scavenge.
if (reference_processor()->processing_is_mt()) {
PSRefProcTaskExecutor task_executor;
reference_processor()->enqueue_discovered_references(&task_executor);
} else {
reference_processor()->enqueue_discovered_references(NULL);
}
// Finally, flush the promotion_manager's labs, and deallocate its stacks.
assert(promotion_manager->claimed_stack_empty(), "Sanity");
PSPromotionManager::post_scavenge();
promotion_failure_occurred = promotion_failed();
if (promotion_failure_occurred) {
_total_promotion_failures++;
clean_up_failed_promotion();
if (PrintGC) {
gclog_or_tty->print("--");
}
}
// Let the size policy know we're done. Note that we count promotion
// failure cleanup time as part of the collection (otherwise, we're
// implicitly saying it's mutator time).
size_policy->minor_collection_end(gc_cause);
if (!promotion_failure_occurred) {
// Swap the survivor spaces.
young_gen->eden_space()->clear();
young_gen->from_space()->clear();
young_gen->swap_spaces();
size_t survived = young_gen->from_space()->used_in_bytes();
size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
size_policy->update_averages(_survivor_overflow, survived, promoted);
if (UseAdaptiveSizePolicy) {
// Calculate the new survivor size and tenuring threshold
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print("AdaptiveSizeStart: ");
gclog_or_tty->stamp();
gclog_or_tty->print_cr(" collection: %d ",
heap->total_collections());
if (Verbose) {
gclog_or_tty->print("old_gen_capacity: %zd young_gen_capacity: %zd"
" perm_gen_capacity: %zd ",
old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
perm_gen->capacity_in_bytes());
}
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
counters->update_old_eden_size(
size_policy->calculated_eden_size_in_bytes());
counters->update_old_promo_size(
size_policy->calculated_promo_size_in_bytes());
counters->update_old_capacity(old_gen->capacity_in_bytes());
counters->update_young_capacity(young_gen->capacity_in_bytes());
counters->update_survived(survived);
counters->update_promoted(promoted);
counters->update_survivor_overflowed(_survivor_overflow);
}
size_t survivor_limit =
size_policy->max_survivor_size(young_gen->max_size());
_tenuring_threshold =
size_policy->compute_survivor_space_size_and_threshold(
_survivor_overflow,
_tenuring_threshold,
survivor_limit);
if (PrintTenuringDistribution) {
gclog_or_tty->cr();
gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %ld)",
size_policy->calculated_survivor_size_in_bytes(),
_tenuring_threshold, MaxTenuringThreshold);
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
counters->update_tenuring_threshold(_tenuring_threshold);
counters->update_survivor_size_counters();
}
// Do call at minor collections?
// Don't check if the size_policy is ready at this
// level. Let the size_policy check that internally.
if (UseAdaptiveSizePolicy &&
UseAdaptiveGenerationSizePolicyAtMinorCollection &&
((gc_cause != GCCause::_java_lang_system_gc) ||
UseAdaptiveSizePolicyWithSystemGC)) {
// Calculate optimial free space amounts
assert(young_gen->max_size() >
young_gen->from_space()->capacity_in_bytes() +
young_gen->to_space()->capacity_in_bytes(),
"Sizes of space in young gen are out-of-bounds");
size_t max_eden_size = young_gen->max_size() -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
young_gen->eden_space()->used_in_bytes(),
old_gen->used_in_bytes(),
perm_gen->used_in_bytes(),
young_gen->eden_space()->capacity_in_bytes(),
old_gen->max_gen_size(),
max_eden_size,
false /* full gc*/,
gc_cause);
}
// Resize the young generation at every collection
// even if new sizes have not been calculated. This is
// to allow resizes that may have been inhibited by the
// relative location of the "to" and "from" spaces.
// Resizing the old gen at minor collects can cause increases
// that don't feed back to the generation sizing policy until
// a major collection. Don't resize the old gen here.
heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
heap->total_collections());
}
}
// Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
// cause the change of the heap layout. Make sure eden is reshaped if that's the case.
// Also update() will case adaptive NUMA chunk resizing.
assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
young_gen->eden_space()->update();
heap->gc_policy_counters()->update_counters();
heap->resize_all_tlabs();
assert(young_gen->to_space()->is_empty(), "to space should be empty now");
}
DerivedPointerTable::update_pointers();
NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
// Re-verify object start arrays
if (VerifyObjectStartArray &&
VerifyAfterGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
// Verify all old -> young cards are now precise
if (VerifyRememberedSets) {
// Precise verification will give false positives. Until this is fixed,
// use imprecise verification.
// CardTableExtension::verify_all_young_refs_precise();
CardTableExtension::verify_all_young_refs_imprecise();
}
if (TraceGen0Time) {
scavenge_time.stop();
if (promotion_failure_occurred)
accumulated_undo_time()->add(scavenge_time);
else
accumulated_gc_time()->add(scavenge_time);
}
if (PrintGC) {
if (PrintGCDetails) {
// Don't print a GC timestamp here. This is after the GC so
// would be confusing.
young_gen->print_used_change(young_gen_used_before);
}
heap->print_heap_change(prev_used);
}
// Track memory usage and detect low memory
MemoryService::track_memory_usage();
heap->update_counters();
}
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyAfterGC:");
Universe::verify(false);
}
if (PrintHeapAtGC) {
Universe::print_heap_after_gc();
}
scavenge_exit.update();
if (PrintGCTaskTimeStamps) {
tty->print_cr("VM-Thread %lld %lld %lld",
scavenge_entry.ticks(), scavenge_midpoint.ticks(),
scavenge_exit.ticks());
gc_task_manager()->print_task_time_stamps();
}
return !promotion_failure_occurred;
}
void PSMarkSweepDecorator::set_destination_decorator_perm_gen() {
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
_destination_decorator = heap->perm_gen()->object_mark_sweep();
}
// This method contains no policy. You should probably
// be calling invoke() instead.
void PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
assert(ref_processor() != NULL, "Sanity");
if (GC_locker::check_active_before_gc()) {
return;
}
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
GCCause::Cause gc_cause = heap->gc_cause();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSAdaptiveSizePolicy* size_policy = heap->size_policy();
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
// Increment the invocation count
heap->increment_total_collections(true /* full */);
// Save information needed to minimize mangling
heap->record_gen_tops_before_GC();
// We need to track unique mark sweep invocations as well.
_total_invocations++;
AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
if (PrintHeapAtGC) {
Universe::print_heap_before_gc();
}
// Fill in TLABs
heap->accumulate_statistics_all_tlabs();
heap->ensure_parsability(true); // retire TLABs
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyBeforeGC:");
Universe::verify(true);
}
// Verify object start arrays
if (VerifyObjectStartArray &&
VerifyBeforeGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
heap->pre_full_gc_dump();
// Filled in below to track the state of the young gen after the collection.
bool eden_empty;
bool survivors_empty;
bool young_gen_empty;
{
HandleMark hm;
const bool is_system_gc = gc_cause == GCCause::_java_lang_system_gc;
// This is useful for debugging but don't change the output the
// the customer sees.
const char* gc_cause_str = "Full GC";
if (is_system_gc && PrintGCDetails) {
gc_cause_str = "Full GC (System)";
}
gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
TraceTime t1(gc_cause_str, PrintGC, !PrintGCDetails, gclog_or_tty);
TraceCollectorStats tcs(counters());
TraceMemoryManagerStats tms(true /* Full GC */);
if (TraceGen1Time) accumulated_time()->start();
// Let the size policy know we're starting
size_policy->major_collection_begin();
// When collecting the permanent generation methodOops may be moving,
// so we either have to flush all bcp data or convert it into bci.
CodeCache::gc_prologue();
Threads::gc_prologue();
BiasedLocking::preserve_marks();
// Capture heap size before collection for printing.
size_t prev_used = heap->used();
// Capture perm gen size before collection for sizing.
size_t perm_gen_prev_used = perm_gen->used_in_bytes();
// For PrintGCDetails
size_t old_gen_prev_used = old_gen->used_in_bytes();
size_t young_gen_prev_used = young_gen->used_in_bytes();
allocate_stacks();
NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
COMPILER2_PRESENT(DerivedPointerTable::clear());
ref_processor()->enable_discovery();
ref_processor()->setup_policy(clear_all_softrefs);
mark_sweep_phase1(clear_all_softrefs);
mark_sweep_phase2();
// Don't add any more derived pointers during phase3
COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
mark_sweep_phase3();
mark_sweep_phase4();
restore_marks();
deallocate_stacks();
if (ZapUnusedHeapArea) {
// Do a complete mangle (top to end) because the usage for
// scratch does not maintain a top pointer.
young_gen->to_space()->mangle_unused_area_complete();
}
eden_empty = young_gen->eden_space()->is_empty();
if (!eden_empty) {
eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
}
// Update heap occupancy information which is used as
// input to soft ref clearing policy at the next gc.
Universe::update_heap_info_at_gc();
survivors_empty = young_gen->from_space()->is_empty() &&
young_gen->to_space()->is_empty();
young_gen_empty = eden_empty && survivors_empty;
BarrierSet* bs = heap->barrier_set();
if (bs->is_a(BarrierSet::ModRef)) {
ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
MemRegion old_mr = heap->old_gen()->reserved();
MemRegion perm_mr = heap->perm_gen()->reserved();
assert(perm_mr.end() <= old_mr.start(), "Generations out of order");
if (young_gen_empty) {
modBS->clear(MemRegion(perm_mr.start(), old_mr.end()));
} else {
modBS->invalidate(MemRegion(perm_mr.start(), old_mr.end()));
}
}
BiasedLocking::restore_marks();
Threads::gc_epilogue();
CodeCache::gc_epilogue();
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
ref_processor()->enqueue_discovered_references(NULL);
// Update time of last GC
reset_millis_since_last_gc();
// Let the size policy know we're done
size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
if (UseAdaptiveSizePolicy) {
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print("AdaptiveSizeStart: ");
gclog_or_tty->stamp();
gclog_or_tty->print_cr(" collection: %d ",
heap->total_collections());
if (Verbose) {
gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
" perm_gen_capacity: %d ",
old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
perm_gen->capacity_in_bytes());
}
}
// Don't check if the size_policy is ready here. Let
// the size_policy check that internally.
if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
((gc_cause != GCCause::_java_lang_system_gc) ||
UseAdaptiveSizePolicyWithSystemGC)) {
// Calculate optimal free space amounts
assert(young_gen->max_size() >
young_gen->from_space()->capacity_in_bytes() +
young_gen->to_space()->capacity_in_bytes(),
"Sizes of space in young gen are out-of-bounds");
size_t max_eden_size = young_gen->max_size() -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
young_gen->eden_space()->used_in_bytes(),
old_gen->used_in_bytes(),
perm_gen->used_in_bytes(),
young_gen->eden_space()->capacity_in_bytes(),
old_gen->max_gen_size(),
max_eden_size,
true /* full gc*/,
gc_cause);
heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
// Don't resize the young generation at an major collection. A
// desired young generation size may have been calculated but
// resizing the young generation complicates the code because the
// resizing of the old generation may have moved the boundary
// between the young generation and the old generation. Let the
// young generation resizing happen at the minor collections.
}
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
heap->total_collections());
}
}
if (UsePerfData) {
heap->gc_policy_counters()->update_counters();
heap->gc_policy_counters()->update_old_capacity(
old_gen->capacity_in_bytes());
heap->gc_policy_counters()->update_young_capacity(
young_gen->capacity_in_bytes());
}
heap->resize_all_tlabs();
// We collected the perm gen, so we'll resize it here.
perm_gen->compute_new_size(perm_gen_prev_used);
if (TraceGen1Time) accumulated_time()->stop();
if (PrintGC) {
if (PrintGCDetails) {
// Don't print a GC timestamp here. This is after the GC so
// would be confusing.
young_gen->print_used_change(young_gen_prev_used);
old_gen->print_used_change(old_gen_prev_used);
}
heap->print_heap_change(prev_used);
// Do perm gen after heap becase prev_used does
// not include the perm gen (done this way in the other
// collectors).
if (PrintGCDetails) {
perm_gen->print_used_change(perm_gen_prev_used);
}
}
// Track memory usage and detect low memory
MemoryService::track_memory_usage();
heap->update_counters();
if (PrintGCDetails) {
if (size_policy->print_gc_time_limit_would_be_exceeded()) {
if (size_policy->gc_time_limit_exceeded()) {
gclog_or_tty->print_cr(" GC time is exceeding GCTimeLimit "
"of %d%%", GCTimeLimit);
} else {
gclog_or_tty->print_cr(" GC time would exceed GCTimeLimit "
"of %d%%", GCTimeLimit);
}
}
size_policy->set_print_gc_time_limit_would_be_exceeded(false);
}
}
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyAfterGC:");
Universe::verify(false);
}
// Re-verify object start arrays
if (VerifyObjectStartArray &&
VerifyAfterGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
if (ZapUnusedHeapArea) {
old_gen->object_space()->check_mangled_unused_area_complete();
perm_gen->object_space()->check_mangled_unused_area_complete();
}
NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
if (PrintHeapAtGC) {
Universe::print_heap_after_gc();
}
heap->post_full_gc_dump();
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
}
void HeapInspection::heap_inspection(outputStream* st, bool need_prologue) {
ResourceMark rm;
HeapWord* ref;
CollectedHeap* heap = Universe::heap();
bool is_shared_heap = false;
switch (heap->kind()) {
case CollectedHeap::G1CollectedHeap:
case CollectedHeap::GenCollectedHeap: {
is_shared_heap = true;
SharedHeap* sh = (SharedHeap*)heap;
if (need_prologue) {
sh->gc_prologue(false /* !full */); // get any necessary locks, etc.
}
ref = sh->perm_gen()->used_region().start();
break;
}
#ifndef SERIALGC
case CollectedHeap::ParallelScavengeHeap: {
ParallelScavengeHeap* psh = (ParallelScavengeHeap*)heap;
ref = psh->perm_gen()->object_space()->used_region().start();
break;
}
#endif // SERIALGC
default:
ShouldNotReachHere(); // Unexpected heap kind for this op
}
// Collect klass instance info
KlassInfoTable cit(KlassInfoTable::cit_size, ref);
if (!cit.allocation_failed()) {
// Iterate over objects in the heap
RecordInstanceClosure ric(&cit);
// If this operation encounters a bad object when using CMS,
// consider using safe_object_iterate() which avoids perm gen
// objects that may contain bad references.
Universe::heap()->object_iterate(&ric);
// Report if certain classes are not counted because of
// running out of C-heap for the histogram.
size_t missed_count = ric.missed_count();
if (missed_count != 0) {
st->print_cr("WARNING: Ran out of C-heap; undercounted " SIZE_FORMAT
" total instances in data below",
missed_count);
}
// Sort and print klass instance info
KlassInfoHisto histo("\n"
" num #instances #bytes class name\n"
"----------------------------------------------",
KlassInfoHisto::histo_initial_size);
HistoClosure hc(&histo);
cit.iterate(&hc);
histo.sort();
histo.print_on(st);
} else {
st->print_cr("WARNING: Ran out of C-heap; histogram not generated");
}
st->flush();
if (need_prologue && is_shared_heap) {
SharedHeap* sh = (SharedHeap*)heap;
sh->gc_epilogue(false /* !full */); // release all acquired locks, etc.
}
}
// This method contains no policy. You should probably
// be calling invoke() instead.
void PSMarkSweep::invoke_no_policy(bool& notify_ref_lock, bool clear_all_softrefs) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
assert(ref_processor() != NULL, "Sanity");
if (GC_locker::is_active()) return;
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
// Increment the invocation count
heap->increment_total_collections();
// We need to track unique mark sweep invocations as well.
_total_invocations++;
if (PrintHeapAtGC) {
gclog_or_tty->print_cr(" {Heap before GC invocations=%d:", heap->total_collections());
Universe::print();
}
// Fill in TLABs
heap->ensure_parseability();
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
tty->print(" VerifyBeforeGC:");
Universe::verify(true);
}
{
HandleMark hm;
TraceTime t1("Full GC", PrintGC, true, gclog_or_tty);
TraceCollectorStats tcs(counters());
if (TraceGen1Time) accumulated_time()->start();
// Let the size policy know we're starting
AdaptiveSizePolicy* size_policy = heap->size_policy();
size_policy->major_collection_begin();
// When collecting the permanent generation methodOops may be moving,
// so we either have to flush all bcp data or convert it into bci.
NOT_CORE(CodeCache::gc_prologue());
Threads::gc_prologue();
// Capture heap size before collection for printing.
size_t prev_used = heap->used();
// Capture perm gen size before collection for sizing.
size_t perm_gen_prev_used = perm_gen->used_in_bytes();
bool marked_for_unloading = false;
allocate_stacks();
NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
COMPILER2_ONLY(DerivedPointerTable::clear());
ref_processor()->enable_discovery();
mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
mark_sweep_phase2();
// Don't add any more derived pointers during phase3
COMPILER2_ONLY(assert(DerivedPointerTable::is_active(), "Sanity"));
COMPILER2_ONLY(DerivedPointerTable::set_active(false));
mark_sweep_phase3();
mark_sweep_phase4();
restore_marks();
deallocate_stacks();
// "free at last gc" is calculated from these.
Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
Universe::set_heap_used_at_last_gc(Universe::heap()->used());
bool all_empty = young_gen->eden_space()->is_empty() &&
young_gen->from_space()->is_empty() &&
young_gen->to_space()->is_empty();
BarrierSet* bs = heap->barrier_set();
if (bs->is_a(BarrierSet::ModRef)) {
ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
MemRegion old_mr = heap->old_gen()->reserved();
MemRegion perm_mr = heap->perm_gen()->reserved();
assert(old_mr.end() <= perm_mr.start(), "Generations out of order");
if (all_empty) {
modBS->clear(MemRegion(old_mr.start(), perm_mr.end()));
} else {
modBS->invalidate(MemRegion(old_mr.start(), perm_mr.end()));
}
}
Threads::gc_epilogue();
NOT_CORE(CodeCache::gc_epilogue());
COMPILER2_ONLY(DerivedPointerTable::update_pointers());
notify_ref_lock |= ref_processor()->enqueue_discovered_references();
// Update time of last GC
reset_millis_since_last_gc();
// Let the size policy know we're done
size_policy->major_collection_end(old_gen->used_in_bytes());
if (UseAdaptiveSizePolicy) {
if (PrintAdaptiveSizePolicy) {
tty->print_cr("AdaptiveSizeStart: collection: %d ",
heap->total_collections());
}
// Calculate optimial free space amounts
size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
old_gen->used_in_bytes(),
perm_gen->used_in_bytes(),
true /* full gc*/);
// Resize old and young generations
old_gen->resize(size_policy->calculated_old_free_size_in_bytes());
young_gen->resize(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
if (PrintAdaptiveSizePolicy) {
tty->print_cr("AdaptiveSizeStop: collection: %d ",
heap->total_collections());
}
}
// We collected the perm gen, so we'll resize it here.
perm_gen->compute_new_size(perm_gen_prev_used);
if (TraceGen1Time) accumulated_time()->stop();
if (PrintGC) {
heap->print_heap_change(prev_used);
}
heap->update_counters();
}
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
tty->print(" VerifyAfterGC:");
Universe::verify(false);
}
NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
if (PrintHeapAtGC) {
gclog_or_tty->print_cr(" Heap after GC invocations=%d:", heap->total_collections());
Universe::print();
gclog_or_tty->print("} ");
}
}
// This method contains no policy. You should probably
// be calling invoke() instead.
void PSScavenge::invoke_no_policy(bool& notify_ref_lock) {
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
TimeStamp scavenge_entry;
TimeStamp scavenge_midpoint;
TimeStamp scavenge_exit;
scavenge_entry.update();
if (GC_locker::is_active()) return;
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
// Check for potential problems.
if (!should_attempt_scavenge()) {
return;
}
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
AdaptiveSizePolicy* size_policy = heap->size_policy();
heap->increment_total_collections();
if (PrintHeapAtGC){
gclog_or_tty->print_cr(" {Heap before GC invocations=%d:", heap->total_collections());
Universe::print();
}
assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
size_t prev_used = heap->used();
assert(promotion_failed() == false, "Sanity");
// Fill in TLABs
heap->ensure_parseability();
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
tty->print(" VerifyBeforeGC:");
Universe::verify(true);
}
{
ResourceMark rm;
HandleMark hm;
TraceTime t1("GC", PrintGC, true, gclog_or_tty);
TraceCollectorStats tcs(counters());
if (TraceGen0Time) accumulated_time()->start();
// Let the size policy know we're starting
size_policy->minor_collection_begin();
// Verify no unmarked old->young roots
if (VerifyRememberedSets) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
CardTableExtension::verify_all_young_refs_imprecise();
}
assert(young_gen->to_space()->is_empty(), "Attempt to scavenge with live objects in to_space");
young_gen->to_space()->clear();
NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
COMPILER2_ONLY(DerivedPointerTable::clear(););
reference_processor()->enable_discovery();
// We track how much was promoted to the next generation for
// the AdaptiveSizePolicy.
size_t old_gen_used_before = old_gen->object_space()->used_in_bytes();
// Reset our survivor overflow.
set_survivor_overflow(false);
// We need to save the old/perm top values before
// creating the promotion_manager. We pass the top
// values to the card_table, to prevent it from
// straying into the promotion labs.
HeapWord* old_top = old_gen->object_space()->top();
HeapWord* perm_top = perm_gen->object_space()->top();
// Release all previously held resources
gc_task_manager()->release_all_resources();
PSPromotionManager::pre_scavenge();
// We'll use the promotion manager again later.
PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
{
// TraceTime("Roots");
GCTaskQueue* q = GCTaskQueue::create();
for(uint i=0; i<ParallelGCThreads; i++) {
q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
}
q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
// We scan the thread roots in parallel
Threads::create_thread_roots_tasks(q);
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
if (ParallelGCThreads>1) {
for (uint j=0; j<ParallelGCThreads-1; j++) {
q->enqueue(new StealTask(false));
}
q->enqueue(new StealTask(true));
}
WaitForBarrierGCTask* fin = WaitForBarrierGCTask::create();
q->enqueue(fin);
gc_task_manager()->add_list(q);
fin->wait_for();
// We have to release the barrier tasks!
WaitForBarrierGCTask::destroy(fin);
}
scavenge_midpoint.update();
NOT_COMPILER2(ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy());
COMPILER2_ONLY(ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy());
PSIsAliveClosure is_alive;
PSKeepAliveClosure keep_alive(promotion_manager);
PSEvacuateFollowersClosure evac_followers(promotion_manager);
// Process reference objects discovered during scavenge
reference_processor()->process_discovered_references(soft_ref_policy, &is_alive,
&keep_alive, &evac_followers);
// Enqueue reference objects discovered during scavenge.
notify_ref_lock = reference_processor()->enqueue_discovered_references();
// Finally, flush the promotion_manager's labs, and deallocate its stacks.
assert(promotion_manager->claimed_stack()->size() == 0, "Sanity");
PSPromotionManager::post_scavenge();
bool scavenge_promotion_failure = promotion_failed();
if (scavenge_promotion_failure) {
clean_up_failed_promotion();
if (PrintGC) {
gclog_or_tty->print("--");
}
}
// Let the size policy know we're done. Note that we count promotion
// failure cleanup time as part of the collection (otherwise, we're implicitly
// saying it's mutator time).
size_policy->minor_collection_end();
if (!scavenge_promotion_failure) {
// Swap the survivor spaces.
young_gen->eden_space()->clear();
young_gen->from_space()->clear();
young_gen->swap_spaces();
if (UseAdaptiveSizePolicy) {
// Calculate the new survivor size and tenuring threshold
size_t survived = young_gen->from_space()->used_in_bytes();
size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
if (PrintAdaptiveSizePolicy) {
tty->print_cr("AdaptiveSizeStart: collection: %d ",
heap->total_collections());
}
size_t survivor_limit =
size_policy->max_survivor_size(young_gen->max_size());
_tenuring_threshold =
size_policy->compute_survivor_space_size_and_threshold(survived,
promoted,
_survivor_overflow,
_tenuring_threshold,
survivor_limit);
// Calculate optimial free space amounts
size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
old_gen->used_in_bytes(),
perm_gen->used_in_bytes(),
false /* full gc*/);
// Resize the old and young generations
old_gen->resize(size_policy->calculated_old_free_size_in_bytes());
young_gen->resize(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
if (PrintAdaptiveSizePolicy) {
tty->print_cr("AdaptiveSizeStop: collection: %d ",
heap->total_collections());
}
}
assert(young_gen->to_space()->is_empty(), "to space should be empty now");
}
COMPILER2_ONLY(DerivedPointerTable::update_pointers());
NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
// Verify all old -> young cards are now precise
if (VerifyRememberedSets) {
// Precise verification will give false positives. Until this is fixed,
// use imprecise verification.
// CardTableExtension::verify_all_young_refs_precise();
CardTableExtension::verify_all_young_refs_imprecise();
}
if (TraceGen0Time) accumulated_time()->stop();
if (PrintGC) {
heap->print_heap_change(prev_used);
}
heap->update_counters();
}
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSScavenge::invoke_no_policy() {
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
assert(_preserved_mark_stack.is_empty(), "should be empty");
assert(_preserved_oop_stack.is_empty(), "should be empty");
_gc_timer.register_gc_start(os::elapsed_counter());
TimeStamp scavenge_entry;
TimeStamp scavenge_midpoint;
TimeStamp scavenge_exit;
scavenge_entry.update();
if (GC_locker::check_active_before_gc()) {
return false;
}
ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
GCCause::Cause gc_cause = heap->gc_cause();
assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
// Check for potential problems.
if (!should_attempt_scavenge()) {
return false;
}
_gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
bool promotion_failure_occurred = false;
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSPermGen* perm_gen = heap->perm_gen();
PSAdaptiveSizePolicy* size_policy = heap->size_policy();
heap->increment_total_collections();
AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
if ((gc_cause != GCCause::_java_lang_system_gc) ||
UseAdaptiveSizePolicyWithSystemGC) {
// Gather the feedback data for eden occupancy.
young_gen->eden_space()->accumulate_statistics();
}
if (ZapUnusedHeapArea) {
// Save information needed to minimize mangling
heap->record_gen_tops_before_GC();
}
heap->print_heap_before_gc();
heap->trace_heap_before_gc(&_gc_tracer);
assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
size_t prev_used = heap->used();
// Fill in TLABs
heap->accumulate_statistics_all_tlabs();
heap->ensure_parsability(true); // retire TLABs
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyBeforeGC:");
Universe::verify();
}
{
ResourceMark rm;
HandleMark hm;
gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
TraceCollectorStats tcs(counters());
TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
if (TraceGen0Time) accumulated_time()->start();
// Let the size policy know we're starting
size_policy->minor_collection_begin();
// Verify the object start arrays.
if (VerifyObjectStartArray &&
VerifyBeforeGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
// Verify no unmarked old->young roots
if (VerifyRememberedSets) {
CardTableExtension::verify_all_young_refs_imprecise();
}
if (!ScavengeWithObjectsInToSpace) {
assert(young_gen->to_space()->is_empty(),
"Attempt to scavenge with live objects in to_space");
young_gen->to_space()->clear(SpaceDecorator::Mangle);
} else if (ZapUnusedHeapArea) {
young_gen->to_space()->mangle_unused_area();
}
save_to_space_top_before_gc();
COMPILER2_PRESENT(DerivedPointerTable::clear());
reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
reference_processor()->setup_policy(false);
// We track how much was promoted to the next generation for
// the AdaptiveSizePolicy.
size_t old_gen_used_before = old_gen->used_in_bytes();
// For PrintGCDetails
size_t young_gen_used_before = young_gen->used_in_bytes();
// Reset our survivor overflow.
set_survivor_overflow(false);
// We need to save the old/perm top values before
// creating the promotion_manager. We pass the top
// values to the card_table, to prevent it from
// straying into the promotion labs.
HeapWord* old_top = old_gen->object_space()->top();
HeapWord* perm_top = perm_gen->object_space()->top();
// Release all previously held resources
gc_task_manager()->release_all_resources();
// Set the number of GC threads to be used in this collection
gc_task_manager()->set_active_gang();
gc_task_manager()->task_idle_workers();
// Get the active number of workers here and use that value
// throughout the methods.
uint active_workers = gc_task_manager()->active_workers();
heap->set_par_threads(active_workers);
PSPromotionManager::pre_scavenge();
// We'll use the promotion manager again later.
PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
{
GCTraceTime tm("Scavenge", false, false, &_gc_timer);
ParallelScavengeHeap::ParStrongRootsScope psrs;
GCTaskQueue* q = GCTaskQueue::create();
uint stripe_total = active_workers;
for(uint i=0; i < stripe_total; i++) {
q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
}
q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
// We scan the thread roots in parallel
Threads::create_thread_roots_tasks(q);
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
ParallelTaskTerminator terminator(
active_workers,
(TaskQueueSetSuper*) promotion_manager->stack_array_depth());
if (active_workers > 1) {
for (uint j = 0; j < active_workers; j++) {
q->enqueue(new StealTask(&terminator));
}
}
gc_task_manager()->execute_and_wait(q);
}
scavenge_midpoint.update();
// Process reference objects discovered during scavenge
{
GCTraceTime tm("References", false, false, &_gc_timer);
reference_processor()->setup_policy(false); // not always_clear
reference_processor()->set_active_mt_degree(active_workers);
PSKeepAliveClosure keep_alive(promotion_manager);
PSEvacuateFollowersClosure evac_followers(promotion_manager);
ReferenceProcessorStats stats;
if (reference_processor()->processing_is_mt()) {
PSRefProcTaskExecutor task_executor;
stats = reference_processor()->process_discovered_references(
&_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
&_gc_timer);
} else {
stats = reference_processor()->process_discovered_references(
&_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
}
_gc_tracer.report_gc_reference_stats(stats);
// Enqueue reference objects discovered during scavenge.
if (reference_processor()->processing_is_mt()) {
PSRefProcTaskExecutor task_executor;
reference_processor()->enqueue_discovered_references(&task_executor);
} else {
reference_processor()->enqueue_discovered_references(NULL);
}
}
if (!JavaObjectsInPerm) {
GCTraceTime tm("StringTable", false, false, &_gc_timer);
// Unlink any dead interned Strings
StringTable::unlink(&_is_alive_closure);
// Process the remaining live ones
PSScavengeRootsClosure root_closure(promotion_manager);
StringTable::oops_do(&root_closure);
}
// Finally, flush the promotion_manager's labs, and deallocate its stacks.
promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
if (promotion_failure_occurred) {
clean_up_failed_promotion();
if (PrintGC) {
gclog_or_tty->print("--");
}
}
// Let the size policy know we're done. Note that we count promotion
// failure cleanup time as part of the collection (otherwise, we're
// implicitly saying it's mutator time).
size_policy->minor_collection_end(gc_cause);
if (!promotion_failure_occurred) {
// Swap the survivor spaces.
young_gen->eden_space()->clear(SpaceDecorator::Mangle);
young_gen->from_space()->clear(SpaceDecorator::Mangle);
young_gen->swap_spaces();
size_t survived = young_gen->from_space()->used_in_bytes();
size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
size_policy->update_averages(_survivor_overflow, survived, promoted);
// A successful scavenge should restart the GC time limit count which is
// for full GC's.
size_policy->reset_gc_overhead_limit_count();
if (UseAdaptiveSizePolicy) {
// Calculate the new survivor size and tenuring threshold
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print("AdaptiveSizeStart: ");
gclog_or_tty->stamp();
gclog_or_tty->print_cr(" collection: %d ",
heap->total_collections());
if (Verbose) {
gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
" perm_gen_capacity: %d ",
old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
perm_gen->capacity_in_bytes());
}
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
counters->update_old_eden_size(
size_policy->calculated_eden_size_in_bytes());
counters->update_old_promo_size(
size_policy->calculated_promo_size_in_bytes());
counters->update_old_capacity(old_gen->capacity_in_bytes());
counters->update_young_capacity(young_gen->capacity_in_bytes());
counters->update_survived(survived);
counters->update_promoted(promoted);
counters->update_survivor_overflowed(_survivor_overflow);
}
size_t survivor_limit =
size_policy->max_survivor_size(young_gen->max_size());
_tenuring_threshold =
size_policy->compute_survivor_space_size_and_threshold(
_survivor_overflow,
_tenuring_threshold,
survivor_limit);
if (PrintTenuringDistribution) {
gclog_or_tty->cr();
gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
size_policy->calculated_survivor_size_in_bytes(),
_tenuring_threshold, MaxTenuringThreshold);
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
counters->update_tenuring_threshold(_tenuring_threshold);
counters->update_survivor_size_counters();
}
// Do call at minor collections?
// Don't check if the size_policy is ready at this
// level. Let the size_policy check that internally.
if (UseAdaptiveSizePolicy &&
UseAdaptiveGenerationSizePolicyAtMinorCollection &&
((gc_cause != GCCause::_java_lang_system_gc) ||
UseAdaptiveSizePolicyWithSystemGC)) {
// Calculate optimial free space amounts
assert(young_gen->max_size() >
young_gen->from_space()->capacity_in_bytes() +
young_gen->to_space()->capacity_in_bytes(),
"Sizes of space in young gen are out-of-bounds");
size_t max_eden_size = young_gen->max_size() -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
young_gen->eden_space()->used_in_bytes(),
old_gen->used_in_bytes(),
perm_gen->used_in_bytes(),
young_gen->eden_space()->capacity_in_bytes(),
old_gen->max_gen_size(),
max_eden_size,
false /* full gc*/,
gc_cause,
heap->collector_policy());
}
// Resize the young generation at every collection
// even if new sizes have not been calculated. This is
// to allow resizes that may have been inhibited by the
// relative location of the "to" and "from" spaces.
// Resizing the old gen at minor collects can cause increases
// that don't feed back to the generation sizing policy until
// a major collection. Don't resize the old gen here.
heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
if (PrintAdaptiveSizePolicy) {
gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
heap->total_collections());
}
}
// Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
// cause the change of the heap layout. Make sure eden is reshaped if that's the case.
// Also update() will case adaptive NUMA chunk resizing.
assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
young_gen->eden_space()->update();
heap->gc_policy_counters()->update_counters();
heap->resize_all_tlabs();
assert(young_gen->to_space()->is_empty(), "to space should be empty now");
}
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
{
GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);
CodeCache::prune_scavenge_root_nmethods();
}
// Re-verify object start arrays
if (VerifyObjectStartArray &&
VerifyAfterGC) {
old_gen->verify_object_start_array();
perm_gen->verify_object_start_array();
}
// Verify all old -> young cards are now precise
if (VerifyRememberedSets) {
// Precise verification will give false positives. Until this is fixed,
// use imprecise verification.
// CardTableExtension::verify_all_young_refs_precise();
CardTableExtension::verify_all_young_refs_imprecise();
}
if (TraceGen0Time) accumulated_time()->stop();
if (PrintGC) {
if (PrintGCDetails) {
// Don't print a GC timestamp here. This is after the GC so
// would be confusing.
young_gen->print_used_change(young_gen_used_before);
}
heap->print_heap_change(prev_used);
}
// Track memory usage and detect low memory
MemoryService::track_memory_usage();
heap->update_counters();
gc_task_manager()->release_idle_workers();
}
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
gclog_or_tty->print(" VerifyAfterGC:");
Universe::verify();
}
heap->print_heap_after_gc();
heap->trace_heap_after_gc(&_gc_tracer);
_gc_tracer.report_tenuring_threshold(tenuring_threshold());
if (ZapUnusedHeapArea) {
young_gen->eden_space()->check_mangled_unused_area_complete();
young_gen->from_space()->check_mangled_unused_area_complete();
young_gen->to_space()->check_mangled_unused_area_complete();
}
scavenge_exit.update();
if (PrintGCTaskTimeStamps) {
tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
scavenge_entry.ticks(), scavenge_midpoint.ticks(),
scavenge_exit.ticks());
gc_task_manager()->print_task_time_stamps();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
_gc_timer.register_gc_end(os::elapsed_counter());
_gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
return !promotion_failure_occurred;
}