8234437: Remove CollectedHeap::safe_object_iterate()
Reviewed-by: kbarrett, sjohanss
/*
* Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
#include "precompiled.hpp"
#include "aot/aotLoader.hpp"
#include "classfile/classLoaderDataGraph.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/stringTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "code/codeCache.hpp"
#include "code/icBuffer.hpp"
#include "gc/serial/defNewGeneration.hpp"
#include "gc/shared/adaptiveSizePolicy.hpp"
#include "gc/shared/cardTableBarrierSet.hpp"
#include "gc/shared/cardTableRS.hpp"
#include "gc/shared/collectedHeap.inline.hpp"
#include "gc/shared/collectorCounters.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.hpp"
#include "gc/shared/gcPolicyCounters.hpp"
#include "gc/shared/gcTrace.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/genArguments.hpp"
#include "gc/shared/gcVMOperations.hpp"
#include "gc/shared/genCollectedHeap.hpp"
#include "gc/shared/genOopClosures.inline.hpp"
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/locationPrinter.inline.hpp"
#include "gc/shared/oopStorageParState.inline.hpp"
#include "gc/shared/scavengableNMethods.hpp"
#include "gc/shared/space.hpp"
#include "gc/shared/strongRootsScope.hpp"
#include "gc/shared/weakProcessor.hpp"
#include "gc/shared/workgroup.hpp"
#include "memory/filemap.hpp"
#include "memory/metaspaceCounters.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/biasedLocking.hpp"
#include "runtime/flags/flagSetting.hpp"
#include "runtime/handles.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/vmThread.hpp"
#include "services/management.hpp"
#include "services/memoryService.hpp"
#include "utilities/debug.hpp"
#include "utilities/formatBuffer.hpp"
#include "utilities/macros.hpp"
#include "utilities/stack.inline.hpp"
#include "utilities/vmError.hpp"
#if INCLUDE_JVMCI
#include "jvmci/jvmci.hpp"
#endif
GenCollectedHeap::GenCollectedHeap(Generation::Name young,
Generation::Name old,
const char* policy_counters_name) :
CollectedHeap(),
_young_gen_spec(new GenerationSpec(young,
NewSize,
MaxNewSize,
GenAlignment)),
_old_gen_spec(new GenerationSpec(old,
OldSize,
MaxOldSize,
GenAlignment)),
_rem_set(NULL),
_soft_ref_gen_policy(),
_gc_policy_counters(new GCPolicyCounters(policy_counters_name, 2, 2)),
_full_collections_completed(0),
_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)) {
}
jint GenCollectedHeap::initialize() {
// While there are no constraints in the GC code that HeapWordSize
// be any particular value, there are multiple other areas in the
// system which believe this to be true (e.g. oop->object_size in some
// cases incorrectly returns the size in wordSize units rather than
// HeapWordSize).
guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
// Allocate space for the heap.
ReservedHeapSpace heap_rs = allocate(HeapAlignment);
if (!heap_rs.is_reserved()) {
vm_shutdown_during_initialization(
"Could not reserve enough space for object heap");
return JNI_ENOMEM;
}
initialize_reserved_region(heap_rs);
_rem_set = create_rem_set(heap_rs.region());
_rem_set->initialize();
CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);
bs->initialize();
BarrierSet::set_barrier_set(bs);
ReservedSpace young_rs = heap_rs.first_part(_young_gen_spec->max_size(), false, false);
_young_gen = _young_gen_spec->init(young_rs, rem_set());
ReservedSpace old_rs = heap_rs.last_part(_young_gen_spec->max_size());
old_rs = old_rs.first_part(_old_gen_spec->max_size(), false, false);
_old_gen = _old_gen_spec->init(old_rs, rem_set());
clear_incremental_collection_failed();
return JNI_OK;
}
CardTableRS* GenCollectedHeap::create_rem_set(const MemRegion& reserved_region) {
return new CardTableRS(reserved_region, false /* scan_concurrently */);
}
void GenCollectedHeap::initialize_size_policy(size_t init_eden_size,
size_t init_promo_size,
size_t init_survivor_size) {
const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
_size_policy = new AdaptiveSizePolicy(init_eden_size,
init_promo_size,
init_survivor_size,
max_gc_pause_sec,
GCTimeRatio);
}
ReservedHeapSpace GenCollectedHeap::allocate(size_t alignment) {
// Now figure out the total size.
const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
assert(alignment % pageSize == 0, "Must be");
// Check for overflow.
size_t total_reserved = _young_gen_spec->max_size() + _old_gen_spec->max_size();
if (total_reserved < _young_gen_spec->max_size()) {
vm_exit_during_initialization("The size of the object heap + VM data exceeds "
"the maximum representable size");
}
assert(total_reserved % alignment == 0,
"Gen size; total_reserved=" SIZE_FORMAT ", alignment="
SIZE_FORMAT, total_reserved, alignment);
ReservedHeapSpace heap_rs = Universe::reserve_heap(total_reserved, alignment);
os::trace_page_sizes("Heap",
MinHeapSize,
total_reserved,
alignment,
heap_rs.base(),
heap_rs.size());
return heap_rs;
}
class GenIsScavengable : public BoolObjectClosure {
public:
bool do_object_b(oop obj) {
return GenCollectedHeap::heap()->is_in_young(obj);
}
};
static GenIsScavengable _is_scavengable;
void GenCollectedHeap::post_initialize() {
CollectedHeap::post_initialize();
ref_processing_init();
DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
initialize_size_policy(def_new_gen->eden()->capacity(),
_old_gen->capacity(),
def_new_gen->from()->capacity());
MarkSweep::initialize();
ScavengableNMethods::initialize(&_is_scavengable);
}
void GenCollectedHeap::ref_processing_init() {
_young_gen->ref_processor_init();
_old_gen->ref_processor_init();
}
PreGenGCValues GenCollectedHeap::get_pre_gc_values() const {
const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
return PreGenGCValues(def_new_gen->used(),
def_new_gen->capacity(),
def_new_gen->eden()->used(),
def_new_gen->eden()->capacity(),
def_new_gen->from()->used(),
def_new_gen->from()->capacity(),
old_gen()->used(),
old_gen()->capacity());
}
GenerationSpec* GenCollectedHeap::young_gen_spec() const {
return _young_gen_spec;
}
GenerationSpec* GenCollectedHeap::old_gen_spec() const {
return _old_gen_spec;
}
size_t GenCollectedHeap::capacity() const {
return _young_gen->capacity() + _old_gen->capacity();
}
size_t GenCollectedHeap::used() const {
return _young_gen->used() + _old_gen->used();
}
void GenCollectedHeap::save_used_regions() {
_old_gen->save_used_region();
_young_gen->save_used_region();
}
size_t GenCollectedHeap::max_capacity() const {
return _young_gen->max_capacity() + _old_gen->max_capacity();
}
// Update the _full_collections_completed counter
// at the end of a stop-world full GC.
unsigned int GenCollectedHeap::update_full_collections_completed() {
MonitorLocker ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
assert(_full_collections_completed <= _total_full_collections,
"Can't complete more collections than were started");
_full_collections_completed = _total_full_collections;
ml.notify_all();
return _full_collections_completed;
}
// Update the _full_collections_completed counter, as appropriate,
// at the end of a concurrent GC cycle. Note the conditional update
// below to allow this method to be called by a concurrent collector
// without synchronizing in any manner with the VM thread (which
// may already have initiated a STW full collection "concurrently").
unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
MonitorLocker ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
assert((_full_collections_completed <= _total_full_collections) &&
(count <= _total_full_collections),
"Can't complete more collections than were started");
if (count > _full_collections_completed) {
_full_collections_completed = count;
ml.notify_all();
}
return _full_collections_completed;
}
// Return true if any of the following is true:
// . the allocation won't fit into the current young gen heap
// . gc locker is occupied (jni critical section)
// . heap memory is tight -- the most recent previous collection
// was a full collection because a partial collection (would
// have) failed and is likely to fail again
bool GenCollectedHeap::should_try_older_generation_allocation(size_t word_size) const {
size_t young_capacity = _young_gen->capacity_before_gc();
return (word_size > heap_word_size(young_capacity))
|| GCLocker::is_active_and_needs_gc()
|| incremental_collection_failed();
}
HeapWord* GenCollectedHeap::expand_heap_and_allocate(size_t size, bool is_tlab) {
HeapWord* result = NULL;
if (_old_gen->should_allocate(size, is_tlab)) {
result = _old_gen->expand_and_allocate(size, is_tlab);
}
if (result == NULL) {
if (_young_gen->should_allocate(size, is_tlab)) {
result = _young_gen->expand_and_allocate(size, is_tlab);
}
}
assert(result == NULL || is_in_reserved(result), "result not in heap");
return result;
}
HeapWord* GenCollectedHeap::mem_allocate_work(size_t size,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded) {
// In general gc_overhead_limit_was_exceeded should be false so
// set it so here and reset it to true only if the gc time
// limit is being exceeded as checked below.
*gc_overhead_limit_was_exceeded = false;
HeapWord* result = NULL;
// Loop until the allocation is satisfied, or unsatisfied after GC.
for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
HandleMark hm; // Discard any handles allocated in each iteration.
// First allocation attempt is lock-free.
Generation *young = _young_gen;
assert(young->supports_inline_contig_alloc(),
"Otherwise, must do alloc within heap lock");
if (young->should_allocate(size, is_tlab)) {
result = young->par_allocate(size, is_tlab);
if (result != NULL) {
assert(is_in_reserved(result), "result not in heap");
return result;
}
}
uint gc_count_before; // Read inside the Heap_lock locked region.
{
MutexLocker ml(Heap_lock);
log_trace(gc, alloc)("GenCollectedHeap::mem_allocate_work: attempting locked slow path allocation");
// Note that only large objects get a shot at being
// allocated in later generations.
bool first_only = !should_try_older_generation_allocation(size);
result = attempt_allocation(size, is_tlab, first_only);
if (result != NULL) {
assert(is_in_reserved(result), "result not in heap");
return result;
}
if (GCLocker::is_active_and_needs_gc()) {
if (is_tlab) {
return NULL; // Caller will retry allocating individual object.
}
if (!is_maximal_no_gc()) {
// Try and expand heap to satisfy request.
result = expand_heap_and_allocate(size, is_tlab);
// Result could be null if we are out of space.
if (result != NULL) {
return result;
}
}
if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
return NULL; // We didn't get to do a GC and we didn't get any memory.
}
// If this thread is not in a jni critical section, we stall
// the requestor until the critical section has cleared and
// GC allowed. When the critical section clears, a GC is
// initiated by the last thread exiting the critical section; so
// we retry the allocation sequence from the beginning of the loop,
// rather than causing more, now probably unnecessary, GC attempts.
JavaThread* jthr = JavaThread::current();
if (!jthr->in_critical()) {
MutexUnlocker mul(Heap_lock);
// Wait for JNI critical section to be exited
GCLocker::stall_until_clear();
gclocker_stalled_count += 1;
continue;
} else {
if (CheckJNICalls) {
fatal("Possible deadlock due to allocating while"
" in jni critical section");
}
return NULL;
}
}
// Read the gc count while the heap lock is held.
gc_count_before = total_collections();
}
VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
VMThread::execute(&op);
if (op.prologue_succeeded()) {
result = op.result();
if (op.gc_locked()) {
assert(result == NULL, "must be NULL if gc_locked() is true");
continue; // Retry and/or stall as necessary.
}
// Allocation has failed and a collection
// has been done. If the gc time limit was exceeded the
// this time, return NULL so that an out-of-memory
// will be thrown. Clear gc_overhead_limit_exceeded
// so that the overhead exceeded does not persist.
const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
const bool softrefs_clear = soft_ref_policy()->all_soft_refs_clear();
if (limit_exceeded && softrefs_clear) {
*gc_overhead_limit_was_exceeded = true;
size_policy()->set_gc_overhead_limit_exceeded(false);
if (op.result() != NULL) {
CollectedHeap::fill_with_object(op.result(), size);
}
return NULL;
}
assert(result == NULL || is_in_reserved(result),
"result not in heap");
return result;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
log_warning(gc, ergo)("GenCollectedHeap::mem_allocate_work retries %d times,"
" size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
}
}
}
HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
bool is_tlab,
bool first_only) {
HeapWord* res = NULL;
if (_young_gen->should_allocate(size, is_tlab)) {
res = _young_gen->allocate(size, is_tlab);
if (res != NULL || first_only) {
return res;
}
}
if (_old_gen->should_allocate(size, is_tlab)) {
res = _old_gen->allocate(size, is_tlab);
}
return res;
}
HeapWord* GenCollectedHeap::mem_allocate(size_t size,
bool* gc_overhead_limit_was_exceeded) {
return mem_allocate_work(size,
false /* is_tlab */,
gc_overhead_limit_was_exceeded);
}
bool GenCollectedHeap::must_clear_all_soft_refs() {
return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
_gc_cause == GCCause::_wb_full_gc;
}
void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
bool is_tlab, bool run_verification, bool clear_soft_refs,
bool restore_marks_for_biased_locking) {
FormatBuffer<> title("Collect gen: %s", gen->short_name());
GCTraceTime(Trace, gc, phases) t1(title);
TraceCollectorStats tcs(gen->counters());
TraceMemoryManagerStats tmms(gen->gc_manager(), gc_cause());
gen->stat_record()->invocations++;
gen->stat_record()->accumulated_time.start();
// Must be done anew before each collection because
// a previous collection will do mangling and will
// change top of some spaces.
record_gen_tops_before_GC();
log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
if (run_verification && VerifyBeforeGC) {
HandleMark hm; // Discard invalid handles created during verification
Universe::verify("Before GC");
}
COMPILER2_PRESENT(DerivedPointerTable::clear());
if (restore_marks_for_biased_locking) {
// We perform this mark word preservation work lazily
// because it's only at this point that we know whether we
// absolutely have to do it; we want to avoid doing it for
// scavenge-only collections where it's unnecessary
BiasedLocking::preserve_marks();
}
// Do collection work
{
// Note on ref discovery: For what appear to be historical reasons,
// GCH enables and disabled (by enqueing) refs discovery.
// In the future this should be moved into the generation's
// collect method so that ref discovery and enqueueing concerns
// are local to a generation. The collect method could return
// an appropriate indication in the case that notification on
// the ref lock was needed. This will make the treatment of
// weak refs more uniform (and indeed remove such concerns
// from GCH). XXX
HandleMark hm; // Discard invalid handles created during gc
save_marks(); // save marks for all gens
// We want to discover references, but not process them yet.
// This mode is disabled in process_discovered_references if the
// generation does some collection work, or in
// enqueue_discovered_references if the generation returns
// without doing any work.
ReferenceProcessor* rp = gen->ref_processor();
// If the discovery of ("weak") refs in this generation is
// atomic wrt other collectors in this configuration, we
// are guaranteed to have empty discovered ref lists.
if (rp->discovery_is_atomic()) {
rp->enable_discovery();
rp->setup_policy(clear_soft_refs);
} else {
// collect() below will enable discovery as appropriate
}
gen->collect(full, clear_soft_refs, size, is_tlab);
if (!rp->enqueuing_is_done()) {
rp->disable_discovery();
} else {
rp->set_enqueuing_is_done(false);
}
rp->verify_no_references_recorded();
}
COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
gen->stat_record()->accumulated_time.stop();
update_gc_stats(gen, full);
if (run_verification && VerifyAfterGC) {
HandleMark hm; // Discard invalid handles created during verification
Universe::verify("After GC");
}
}
void GenCollectedHeap::do_collection(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_tlab,
GenerationType max_generation) {
ResourceMark rm;
DEBUG_ONLY(Thread* my_thread = Thread::current();)
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(my_thread->is_VM_thread() ||
my_thread->is_ConcurrentGC_thread(),
"incorrect thread type capability");
assert(Heap_lock->is_locked(),
"the requesting thread should have the Heap_lock");
guarantee(!is_gc_active(), "collection is not reentrant");
if (GCLocker::check_active_before_gc()) {
return; // GC is disabled (e.g. JNI GetXXXCritical operation)
}
const bool do_clear_all_soft_refs = clear_all_soft_refs ||
soft_ref_policy()->should_clear_all_soft_refs();
ClearedAllSoftRefs casr(do_clear_all_soft_refs, soft_ref_policy());
FlagSetting fl(_is_gc_active, true);
bool complete = full && (max_generation == OldGen);
bool old_collects_young = complete && !ScavengeBeforeFullGC;
bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
const PreGenGCValues pre_gc_values = get_pre_gc_values();
bool run_verification = total_collections() >= VerifyGCStartAt;
bool prepared_for_verification = false;
bool do_full_collection = false;
if (do_young_collection) {
GCIdMark gc_id_mark;
GCTraceCPUTime tcpu;
GCTraceTime(Info, gc) t("Pause Young", NULL, gc_cause(), true);
print_heap_before_gc();
if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
prepare_for_verify();
prepared_for_verification = true;
}
gc_prologue(complete);
increment_total_collections(complete);
collect_generation(_young_gen,
full,
size,
is_tlab,
run_verification && VerifyGCLevel <= 0,
do_clear_all_soft_refs,
false);
if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
// Allocation request was met by young GC.
size = 0;
}
// Ask if young collection is enough. If so, do the final steps for young collection,
// and fallthrough to the end.
do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
if (!do_full_collection) {
// Adjust generation sizes.
_young_gen->compute_new_size();
print_heap_change(pre_gc_values);
// Track memory usage and detect low memory after GC finishes
MemoryService::track_memory_usage();
gc_epilogue(complete);
}
print_heap_after_gc();
} else {
// No young collection, ask if we need to perform Full collection.
do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
}
if (do_full_collection) {
GCIdMark gc_id_mark;
GCTraceCPUTime tcpu;
GCTraceTime(Info, gc) t("Pause Full", NULL, gc_cause(), true);
print_heap_before_gc();
if (!prepared_for_verification && run_verification &&
VerifyGCLevel <= 1 && VerifyBeforeGC) {
prepare_for_verify();
}
if (!do_young_collection) {
gc_prologue(complete);
increment_total_collections(complete);
}
// Accounting quirk: total full collections would be incremented when "complete"
// is set, by calling increment_total_collections above. However, we also need to
// account Full collections that had "complete" unset.
if (!complete) {
increment_total_full_collections();
}
collect_generation(_old_gen,
full,
size,
is_tlab,
run_verification && VerifyGCLevel <= 1,
do_clear_all_soft_refs,
true);
// Adjust generation sizes.
_old_gen->compute_new_size();
_young_gen->compute_new_size();
// Delete metaspaces for unloaded class loaders and clean up loader_data graph
ClassLoaderDataGraph::purge();
MetaspaceUtils::verify_metrics();
// Resize the metaspace capacity after full collections
MetaspaceGC::compute_new_size();
update_full_collections_completed();
print_heap_change(pre_gc_values);
// Track memory usage and detect low memory after GC finishes
MemoryService::track_memory_usage();
// Need to tell the epilogue code we are done with Full GC, regardless what was
// the initial value for "complete" flag.
gc_epilogue(true);
BiasedLocking::restore_marks();
print_heap_after_gc();
}
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
}
bool GenCollectedHeap::should_do_full_collection(size_t size, bool full, bool is_tlab,
GenCollectedHeap::GenerationType max_gen) const {
return max_gen == OldGen && _old_gen->should_collect(full, size, is_tlab);
}
void GenCollectedHeap::register_nmethod(nmethod* nm) {
ScavengableNMethods::register_nmethod(nm);
}
void GenCollectedHeap::unregister_nmethod(nmethod* nm) {
ScavengableNMethods::unregister_nmethod(nm);
}
void GenCollectedHeap::verify_nmethod(nmethod* nm) {
ScavengableNMethods::verify_nmethod(nm);
}
void GenCollectedHeap::flush_nmethod(nmethod* nm) {
// Do nothing.
}
void GenCollectedHeap::prune_scavengable_nmethods() {
ScavengableNMethods::prune_nmethods();
}
HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
GCCauseSetter x(this, GCCause::_allocation_failure);
HeapWord* result = NULL;
assert(size != 0, "Precondition violated");
if (GCLocker::is_active_and_needs_gc()) {
// GC locker is active; instead of a collection we will attempt
// to expand the heap, if there's room for expansion.
if (!is_maximal_no_gc()) {
result = expand_heap_and_allocate(size, is_tlab);
}
return result; // Could be null if we are out of space.
} else if (!incremental_collection_will_fail(false /* don't consult_young */)) {
// Do an incremental collection.
do_collection(false, // full
false, // clear_all_soft_refs
size, // size
is_tlab, // is_tlab
GenCollectedHeap::OldGen); // max_generation
} else {
log_trace(gc)(" :: Trying full because partial may fail :: ");
// Try a full collection; see delta for bug id 6266275
// for the original code and why this has been simplified
// with from-space allocation criteria modified and
// such allocation moved out of the safepoint path.
do_collection(true, // full
false, // clear_all_soft_refs
size, // size
is_tlab, // is_tlab
GenCollectedHeap::OldGen); // max_generation
}
result = attempt_allocation(size, is_tlab, false /*first_only*/);
if (result != NULL) {
assert(is_in_reserved(result), "result not in heap");
return result;
}
// OK, collection failed, try expansion.
result = expand_heap_and_allocate(size, is_tlab);
if (result != NULL) {
return result;
}
// If we reach this point, we're really out of memory. Try every trick
// we can to reclaim memory. Force collection of soft references. Force
// a complete compaction of the heap. Any additional methods for finding
// free memory should be here, especially if they are expensive. If this
// attempt fails, an OOM exception will be thrown.
{
UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
do_collection(true, // full
true, // clear_all_soft_refs
size, // size
is_tlab, // is_tlab
GenCollectedHeap::OldGen); // max_generation
}
result = attempt_allocation(size, is_tlab, false /* first_only */);
if (result != NULL) {
assert(is_in_reserved(result), "result not in heap");
return result;
}
assert(!soft_ref_policy()->should_clear_all_soft_refs(),
"Flag should have been handled and cleared prior to this point");
// What else? We might try synchronous finalization later. If the total
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
return NULL;
}
#ifdef ASSERT
class AssertNonScavengableClosure: public OopClosure {
public:
virtual void do_oop(oop* p) {
assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
"Referent should not be scavengable."); }
virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
};
static AssertNonScavengableClosure assert_is_non_scavengable_closure;
#endif
void GenCollectedHeap::process_roots(StrongRootsScope* scope,
ScanningOption so,
OopClosure* strong_roots,
CLDClosure* strong_cld_closure,
CLDClosure* weak_cld_closure,
CodeBlobToOopClosure* code_roots) {
// General roots.
assert(code_roots != NULL, "code root closure should always be set");
// _n_termination for _process_strong_tasks should be set up stream
// in a method not running in a GC worker. Otherwise the GC worker
// could be trying to change the termination condition while the task
// is executing in another GC worker.
if (_process_strong_tasks->try_claim_task(GCH_PS_ClassLoaderDataGraph_oops_do)) {
ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
}
// Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
bool is_par = scope->n_threads() > 1;
Threads::possibly_parallel_oops_do(is_par, strong_roots, roots_from_code_p);
if (_process_strong_tasks->try_claim_task(GCH_PS_Universe_oops_do)) {
Universe::oops_do(strong_roots);
}
// Global (strong) JNI handles
if (_process_strong_tasks->try_claim_task(GCH_PS_JNIHandles_oops_do)) {
JNIHandles::oops_do(strong_roots);
}
if (_process_strong_tasks->try_claim_task(GCH_PS_ObjectSynchronizer_oops_do)) {
ObjectSynchronizer::oops_do(strong_roots);
}
if (_process_strong_tasks->try_claim_task(GCH_PS_Management_oops_do)) {
Management::oops_do(strong_roots);
}
if (_process_strong_tasks->try_claim_task(GCH_PS_jvmti_oops_do)) {
JvmtiExport::oops_do(strong_roots);
}
#if INCLUDE_AOT
if (UseAOT && _process_strong_tasks->try_claim_task(GCH_PS_aot_oops_do)) {
AOTLoader::oops_do(strong_roots);
}
#endif
if (_process_strong_tasks->try_claim_task(GCH_PS_SystemDictionary_oops_do)) {
SystemDictionary::oops_do(strong_roots);
}
if (_process_strong_tasks->try_claim_task(GCH_PS_CodeCache_oops_do)) {
if (so & SO_ScavengeCodeCache) {
assert(code_roots != NULL, "must supply closure for code cache");
// We only visit parts of the CodeCache when scavenging.
ScavengableNMethods::nmethods_do(code_roots);
}
if (so & SO_AllCodeCache) {
assert(code_roots != NULL, "must supply closure for code cache");
// CMSCollector uses this to do intermediate-strength collections.
// We scan the entire code cache, since CodeCache::do_unloading is not called.
CodeCache::blobs_do(code_roots);
}
// Verify that the code cache contents are not subject to
// movement by a scavenging collection.
DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
DEBUG_ONLY(ScavengableNMethods::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
}
}
void GenCollectedHeap::young_process_roots(StrongRootsScope* scope,
OopsInGenClosure* root_closure,
OopsInGenClosure* old_gen_closure,
CLDClosure* cld_closure) {
MarkingCodeBlobClosure mark_code_closure(root_closure, CodeBlobToOopClosure::FixRelocations);
process_roots(scope, SO_ScavengeCodeCache, root_closure,
cld_closure, cld_closure, &mark_code_closure);
if (_process_strong_tasks->try_claim_task(GCH_PS_younger_gens)) {
root_closure->reset_generation();
}
// When collection is parallel, all threads get to cooperate to do
// old generation scanning.
old_gen_closure->set_generation(_old_gen);
rem_set()->younger_refs_iterate(_old_gen, old_gen_closure, scope->n_threads());
old_gen_closure->reset_generation();
_process_strong_tasks->all_tasks_completed(scope->n_threads());
}
void GenCollectedHeap::full_process_roots(StrongRootsScope* scope,
bool is_adjust_phase,
ScanningOption so,
bool only_strong_roots,
OopsInGenClosure* root_closure,
CLDClosure* cld_closure) {
MarkingCodeBlobClosure mark_code_closure(root_closure, is_adjust_phase);
CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
process_roots(scope, so, root_closure, cld_closure, weak_cld_closure, &mark_code_closure);
_process_strong_tasks->all_tasks_completed(scope->n_threads());
}
void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
WeakProcessor::oops_do(root_closure);
_young_gen->ref_processor()->weak_oops_do(root_closure);
_old_gen->ref_processor()->weak_oops_do(root_closure);
}
bool GenCollectedHeap::no_allocs_since_save_marks() {
return _young_gen->no_allocs_since_save_marks() &&
_old_gen->no_allocs_since_save_marks();
}
bool GenCollectedHeap::supports_inline_contig_alloc() const {
return _young_gen->supports_inline_contig_alloc();
}
HeapWord* volatile* GenCollectedHeap::top_addr() const {
return _young_gen->top_addr();
}
HeapWord** GenCollectedHeap::end_addr() const {
return _young_gen->end_addr();
}
// public collection interfaces
void GenCollectedHeap::collect(GCCause::Cause cause) {
if ((cause == GCCause::_wb_young_gc) ||
(cause == GCCause::_gc_locker)) {
// Young collection for WhiteBox or GCLocker.
collect(cause, YoungGen);
} else {
#ifdef ASSERT
if (cause == GCCause::_scavenge_alot) {
// Young collection only.
collect(cause, YoungGen);
} else {
// Stop-the-world full collection.
collect(cause, OldGen);
}
#else
// Stop-the-world full collection.
collect(cause, OldGen);
#endif
}
}
void GenCollectedHeap::collect(GCCause::Cause cause, GenerationType max_generation) {
// The caller doesn't have the Heap_lock
assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
MutexLocker ml(Heap_lock);
collect_locked(cause, max_generation);
}
void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
// The caller has the Heap_lock
assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
collect_locked(cause, OldGen);
}
// this is the private collection interface
// The Heap_lock is expected to be held on entry.
void GenCollectedHeap::collect_locked(GCCause::Cause cause, GenerationType max_generation) {
// Read the GC count while holding the Heap_lock
unsigned int gc_count_before = total_collections();
unsigned int full_gc_count_before = total_full_collections();
if (GCLocker::should_discard(cause, gc_count_before)) {
return;
}
{
MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
VM_GenCollectFull op(gc_count_before, full_gc_count_before,
cause, max_generation);
VMThread::execute(&op);
}
}
void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
do_full_collection(clear_all_soft_refs, OldGen);
}
void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
GenerationType last_generation) {
do_collection(true, // full
clear_all_soft_refs, // clear_all_soft_refs
0, // size
false, // is_tlab
last_generation); // last_generation
// Hack XXX FIX ME !!!
// A scavenge may not have been attempted, or may have
// been attempted and failed, because the old gen was too full
if (gc_cause() == GCCause::_gc_locker && incremental_collection_failed()) {
log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
// This time allow the old gen to be collected as well
do_collection(true, // full
clear_all_soft_refs, // clear_all_soft_refs
0, // size
false, // is_tlab
OldGen); // last_generation
}
}
bool GenCollectedHeap::is_in_young(oop p) {
bool result = ((HeapWord*)p) < _old_gen->reserved().start();
assert(result == _young_gen->is_in_reserved(p),
"incorrect test - result=%d, p=" INTPTR_FORMAT, result, p2i((void*)p));
return result;
}
// Returns "TRUE" iff "p" points into the committed areas of the heap.
bool GenCollectedHeap::is_in(const void* p) const {
return _young_gen->is_in(p) || _old_gen->is_in(p);
}
#ifdef ASSERT
// Don't implement this by using is_in_young(). This method is used
// in some cases to check that is_in_young() is correct.
bool GenCollectedHeap::is_in_partial_collection(const void* p) {
assert(is_in_reserved(p) || p == NULL,
"Does not work if address is non-null and outside of the heap");
return p < _young_gen->reserved().end() && p != NULL;
}
#endif
void GenCollectedHeap::oop_iterate(OopIterateClosure* cl) {
_young_gen->oop_iterate(cl);
_old_gen->oop_iterate(cl);
}
void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
_young_gen->object_iterate(cl);
_old_gen->object_iterate(cl);
}
Space* GenCollectedHeap::space_containing(const void* addr) const {
Space* res = _young_gen->space_containing(addr);
if (res != NULL) {
return res;
}
res = _old_gen->space_containing(addr);
assert(res != NULL, "Could not find containing space");
return res;
}
HeapWord* GenCollectedHeap::block_start(const void* addr) const {
assert(is_in_reserved(addr), "block_start of address outside of heap");
if (_young_gen->is_in_reserved(addr)) {
assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
return _young_gen->block_start(addr);
}
assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
return _old_gen->block_start(addr);
}
bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
assert(block_start(addr) == addr, "addr must be a block start");
if (_young_gen->is_in_reserved(addr)) {
return _young_gen->block_is_obj(addr);
}
assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
return _old_gen->block_is_obj(addr);
}
bool GenCollectedHeap::supports_tlab_allocation() const {
assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
return _young_gen->supports_tlab_allocation();
}
size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
if (_young_gen->supports_tlab_allocation()) {
return _young_gen->tlab_capacity();
}
return 0;
}
size_t GenCollectedHeap::tlab_used(Thread* thr) const {
assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
if (_young_gen->supports_tlab_allocation()) {
return _young_gen->tlab_used();
}
return 0;
}
size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
if (_young_gen->supports_tlab_allocation()) {
return _young_gen->unsafe_max_tlab_alloc();
}
return 0;
}
HeapWord* GenCollectedHeap::allocate_new_tlab(size_t min_size,
size_t requested_size,
size_t* actual_size) {
bool gc_overhead_limit_was_exceeded;
HeapWord* result = mem_allocate_work(requested_size /* size */,
true /* is_tlab */,
&gc_overhead_limit_was_exceeded);
if (result != NULL) {
*actual_size = requested_size;
}
return result;
}
// Requires "*prev_ptr" to be non-NULL. Deletes and a block of minimal size
// from the list headed by "*prev_ptr".
static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
bool first = true;
size_t min_size = 0; // "first" makes this conceptually infinite.
ScratchBlock **smallest_ptr, *smallest;
ScratchBlock *cur = *prev_ptr;
while (cur) {
assert(*prev_ptr == cur, "just checking");
if (first || cur->num_words < min_size) {
smallest_ptr = prev_ptr;
smallest = cur;
min_size = smallest->num_words;
first = false;
}
prev_ptr = &cur->next;
cur = cur->next;
}
smallest = *smallest_ptr;
*smallest_ptr = smallest->next;
return smallest;
}
// Sort the scratch block list headed by res into decreasing size order,
// and set "res" to the result.
static void sort_scratch_list(ScratchBlock*& list) {
ScratchBlock* sorted = NULL;
ScratchBlock* unsorted = list;
while (unsorted) {
ScratchBlock *smallest = removeSmallestScratch(&unsorted);
smallest->next = sorted;
sorted = smallest;
}
list = sorted;
}
ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
size_t max_alloc_words) {
ScratchBlock* res = NULL;
_young_gen->contribute_scratch(res, requestor, max_alloc_words);
_old_gen->contribute_scratch(res, requestor, max_alloc_words);
sort_scratch_list(res);
return res;
}
void GenCollectedHeap::release_scratch() {
_young_gen->reset_scratch();
_old_gen->reset_scratch();
}
class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
void do_generation(Generation* gen) {
gen->prepare_for_verify();
}
};
void GenCollectedHeap::prepare_for_verify() {
ensure_parsability(false); // no need to retire TLABs
GenPrepareForVerifyClosure blk;
generation_iterate(&blk, false);
}
void GenCollectedHeap::generation_iterate(GenClosure* cl,
bool old_to_young) {
if (old_to_young) {
cl->do_generation(_old_gen);
cl->do_generation(_young_gen);
} else {
cl->do_generation(_young_gen);
cl->do_generation(_old_gen);
}
}
bool GenCollectedHeap::is_maximal_no_gc() const {
return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
}
void GenCollectedHeap::save_marks() {
_young_gen->save_marks();
_old_gen->save_marks();
}
GenCollectedHeap* GenCollectedHeap::heap() {
CollectedHeap* heap = Universe::heap();
assert(heap != NULL, "Uninitialized access to GenCollectedHeap::heap()");
assert(heap->kind() == CollectedHeap::Serial, "Invalid name");
return (GenCollectedHeap*) heap;
}
#if INCLUDE_SERIALGC
void GenCollectedHeap::prepare_for_compaction() {
// Start by compacting into same gen.
CompactPoint cp(_old_gen);
_old_gen->prepare_for_compaction(&cp);
_young_gen->prepare_for_compaction(&cp);
}
#endif // INCLUDE_SERIALGC
void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
log_debug(gc, verify)("%s", _old_gen->name());
_old_gen->verify();
log_debug(gc, verify)("%s", _old_gen->name());
_young_gen->verify();
log_debug(gc, verify)("RemSet");
rem_set()->verify();
}
void GenCollectedHeap::print_on(outputStream* st) const {
_young_gen->print_on(st);
_old_gen->print_on(st);
MetaspaceUtils::print_on(st);
}
void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
}
void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
}
bool GenCollectedHeap::print_location(outputStream* st, void* addr) const {
return BlockLocationPrinter<GenCollectedHeap>::print_location(st, addr);
}
void GenCollectedHeap::print_tracing_info() const {
if (log_is_enabled(Debug, gc, heap, exit)) {
LogStreamHandle(Debug, gc, heap, exit) lsh;
_young_gen->print_summary_info_on(&lsh);
_old_gen->print_summary_info_on(&lsh);
}
}
void GenCollectedHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
HEAP_CHANGE_FORMAT" "
HEAP_CHANGE_FORMAT,
HEAP_CHANGE_FORMAT_ARGS(def_new_gen->short_name(),
pre_gc_values.young_gen_used(),
pre_gc_values.young_gen_capacity(),
def_new_gen->used(),
def_new_gen->capacity()),
HEAP_CHANGE_FORMAT_ARGS("Eden",
pre_gc_values.eden_used(),
pre_gc_values.eden_capacity(),
def_new_gen->eden()->used(),
def_new_gen->eden()->capacity()),
HEAP_CHANGE_FORMAT_ARGS("From",
pre_gc_values.from_used(),
pre_gc_values.from_capacity(),
def_new_gen->from()->used(),
def_new_gen->from()->capacity()));
log_info(gc, heap)(HEAP_CHANGE_FORMAT,
HEAP_CHANGE_FORMAT_ARGS(old_gen()->short_name(),
pre_gc_values.old_gen_used(),
pre_gc_values.old_gen_capacity(),
old_gen()->used(),
old_gen()->capacity()));
MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
}
class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
private:
bool _full;
public:
void do_generation(Generation* gen) {
gen->gc_prologue(_full);
}
GenGCPrologueClosure(bool full) : _full(full) {};
};
void GenCollectedHeap::gc_prologue(bool full) {
assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
// Fill TLAB's and such
ensure_parsability(true); // retire TLABs
// Walk generations
GenGCPrologueClosure blk(full);
generation_iterate(&blk, false); // not old-to-young.
};
class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
private:
bool _full;
public:
void do_generation(Generation* gen) {
gen->gc_epilogue(_full);
}
GenGCEpilogueClosure(bool full) : _full(full) {};
};
void GenCollectedHeap::gc_epilogue(bool full) {
#if COMPILER2_OR_JVMCI
assert(DerivedPointerTable::is_empty(), "derived pointer present");
size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
guarantee(is_client_compilation_mode_vm() || actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
#endif // COMPILER2_OR_JVMCI
resize_all_tlabs();
GenGCEpilogueClosure blk(full);
generation_iterate(&blk, false); // not old-to-young.
if (!CleanChunkPoolAsync) {
Chunk::clean_chunk_pool();
}
MetaspaceCounters::update_performance_counters();
CompressedClassSpaceCounters::update_performance_counters();
};
#ifndef PRODUCT
class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
private:
public:
void do_generation(Generation* gen) {
gen->record_spaces_top();
}
};
void GenCollectedHeap::record_gen_tops_before_GC() {
if (ZapUnusedHeapArea) {
GenGCSaveTopsBeforeGCClosure blk;
generation_iterate(&blk, false); // not old-to-young.
}
}
#endif // not PRODUCT
class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
public:
void do_generation(Generation* gen) {
gen->ensure_parsability();
}
};
void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
CollectedHeap::ensure_parsability(retire_tlabs);
GenEnsureParsabilityClosure ep_cl;
generation_iterate(&ep_cl, false);
}
oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
oop obj,
size_t obj_size) {
guarantee(old_gen == _old_gen, "We only get here with an old generation");
assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
HeapWord* result = NULL;
result = old_gen->expand_and_allocate(obj_size, false);
if (result != NULL) {
Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
}
return oop(result);
}
class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
jlong _time; // in ms
jlong _now; // in ms
public:
GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
jlong time() { return _time; }
void do_generation(Generation* gen) {
_time = MIN2(_time, gen->time_of_last_gc(_now));
}
};
jlong GenCollectedHeap::millis_since_last_gc() {
// javaTimeNanos() is guaranteed to be monotonically non-decreasing
// provided the underlying platform provides such a time source
// (and it is bug free). So we still have to guard against getting
// back a time later than 'now'.
jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
GenTimeOfLastGCClosure tolgc_cl(now);
// iterate over generations getting the oldest
// time that a generation was collected
generation_iterate(&tolgc_cl, false);
jlong retVal = now - tolgc_cl.time();
if (retVal < 0) {
log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
". returning zero instead.", retVal);
return 0;
}
return retVal;
}