// 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();
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();
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
Universe::verify(" VerifyBeforeGC:");
}
{
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();
}
// 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 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();
// 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();
if (!old_gen->object_space()->is_empty()) {
// There are only old-to-young pointers if there are objects
// in the old gen.
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 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::class_loader_data));
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);
}
}
{
GCTraceTime tm("StringTable", false, false, &_gc_timer);
// Unlink any dead interned Strings and process the remaining live ones.
PSScavengeRootsClosure root_closure(promotion_manager);
StringTable::unlink_or_oops_do(&_is_alive_closure, &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",
old_gen->capacity_in_bytes(), young_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 max_young_size = young_gen->max_size();
// Deciding a free ratio in the young generation is tricky, so if
// MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
// that the old generation size may have been limited because of them) we
// should then limit our young generation size using NewRatio to have it
// follow the old generation size.
if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
}
size_t survivor_limit =
size_policy->max_survivor_size(max_young_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 " SIZE_FORMAT " bytes, new threshold %u (max %u)",
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 (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 young_live = young_gen->used_in_bytes();
size_t eden_live = young_gen->eden_space()->used_in_bytes();
size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
size_t max_old_gen_size = old_gen->max_gen_size();
size_t max_eden_size = max_young_size -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
// Used for diagnostics
size_policy->clear_generation_free_space_flags();
size_policy->compute_eden_space_size(young_live,
eden_live,
cur_eden,
max_eden_size,
false /* not full gc*/);
size_policy->check_gc_overhead_limit(young_live,
eden_live,
max_old_gen_size,
max_eden_size,
false /* not full gc*/,
gc_cause,
heap->collector_policy());
size_policy->decay_supplemental_growth(false /* not full gc*/);
}
// 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();
}
// 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
Universe::verify(" VerifyAfterGC:");
}
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();
_gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
return !promotion_failure_occurred;
}
